HEP2026: 42nd Conference on Recent Developments in High Energy Physics and Cosmology [NTUA] Jul 8 – 11, 2026

Jul 8, 2026, 9:00 AM → Jul 11, 2026, 7:00 PM Europe/Athens

Main Hall (Level 1) (National Technical University of Athens)

Wed, July 8

9:30 AM → 10:00 AM Welcome HEP2026

Conveners: Ioannis Kopsalis (National Technical Univ. of Athens (GR)), Theodoros Alexopoulos (National Technical Univ. of Athens (GR))

9:30 AM Welcome from the Vice-Rector

Speaker: Panagiotis Psarakos

9:35 AM Welcome from the HEP2026 Organizing Committee

Speaker: Theodoros Alexopoulos (National Technical Univ. of Athens (GR))

welcome_slides.pdf

9:40 AM Welcome and Statement of the President of the CERN Council

Speaker: Costas Fountas (University of Ioannina (GR))

9:50 AM Welcome of the President of Athens Chamber of Tradesmen

Speaker: Ioannis Chatzitheodosiou

10:00 AM → 11:00 AM Keynote

Convener: Theodoros Alexopoulos (National Technical Univ. of Athens (GR))

10:00 AM From Tracks to Triggers: The CMS upgrade for the HL-LHC

Speaker: Konstantinos Manolopoulos (Science and Technology Facilities Council STFC (GB))

HEP26_Manolopoulos.pdf

10:30 AM Towards energy sensitive Quantum Sensors: Dual Mode SNSPDs

Ξεκινώντας από το CERN και έρευνες πάνω στο σωματίδιο Higgs, μετά από μιά σειρά συμπτώσεων διαπιστώσαμε οτι δεν υπάρχουν ανιχνευτές απλών φωτονίων στο οπτικό και υπέρυθρο φάσμα που να μπορούν να μετρήσουν τον αριθμὀ φωτονίων ή την ενέργεια των φωτονίων, με ταυτόχρονη υψηλή ακρίβεια στον χρόνο ανίχνευσης. Το 2025 προτείναμε έναν καινούριο τύπο κβαντικού ανιχνευτή: Dual-Mode SNSPD.

Στη συμβατική λειτουργία Geiger, ο ανιχνευτής λειτουργεί σε θερμοκρασίες πολύ κάτω από την θερμοκρασία Curie Tc, λειτουργώντας ως μετρητής συμβάντων χωρίς ευαισθησία στον αριθμό των φωτονίων που προσπίπτουν στον αισθητήρα. Στη θερμιδομετρική λειτουργία, ο ανιχνευτής λειτουργεί σε θερμοκρασίες ακριβώς κάτω από την Tc και εμφανίζει θερμιδομετρική ευαισθησία στην περιοχή των 15-250 ισοδύναμων απορροφούμενων φωτονίων για μια δέσμη φωτονίων με μήκος κύματος 515 nm. Σε αυτήν την ενεργειακά ευαίσθητη λειτουργία, η απορρόφηση φωτονίων προκαλεί θέρμανση Joule του SNSPD. Ανάλογα με την εφαρμογή, ρυθμίζοντας τη θερμοκρασία του ανιχνευτή και το ρεύμα πόλωσης χρησιμοποιώντας το ίδιο σύστημα ανάγνωσης, το SNSPD μπορεί εύκολα να εναλλάσσεται μεταξύ των δύο λειτουργιών. Τα SNSPD διπλής λειτουργίας, εκτός από την παροχή λύσεων σε εφαρμογές στη φασματοσκοπία και τη θερμιδομετρία, όπου απαιτείται ακριβής χρονισμός και ενεργειακή ανάλυση, μπορούν επίσης να προσφέρουν σημαντικές εξελίξεις στην ανίχνευση υψηλής ταχύτητας με ανάλυση αριθμού φωτονίων μέσω της ευέλικτης υβριδικής αρχιτεκτονικής τους, προωθώντας την καινοτομία στην οπτική κβαντική υπολογιστική και τον χαρακτηρισμό κβαντικών πηγών. Οι συγκεκριμένοι ανιχνευτές είναι ιδεώδεις για έρευνες για dark matter, όπως επίσης και για ιατρική απεικόνιση (medical imaging).

Speaker: Stathes Paganis (National Taiwan University)

EESFYE_2026-July10-DMSNSPDs.pdf

11:00 AM → 11:30 AM Coffee break

11:30 AM → 1:30 PM Experiments

Convener: Dimitris Fassouliotis (National and Kapodistrian University of Athens (GR))

11:30 AM Electroweak Physics with Multiboson Production at the LHC: Past, Present, and Future

Multiboson production provides a powerful framework to probe the electroweak sector of the Standard Model, allowing direct access to triple and quartic gauge couplings. During Run 2 of the LHC, major experimental milestones were achieved, with the observation and measurement of electroweak diboson and triboson processes, marking the first experimental sensitivity to quartic gauge couplings at the TeV scale.
Vector Boson Scattering (VBS) plays a central role in these studies, offering unique sensitivity to the gauge structure of the Standard Model. In particular, polarized VBS, although experimentally challenging, provides new opportunities to further test the electroweak sector and enhance sensitivity to effects beyond Standard Model expectations.
Looking ahead, the increased dataset from Run 3 and the High-Luminosity LHC will significantly extend the reach of multiboson measurements. Future analyses are expected to improve precision and strengthen constraints on new physics contributions. This contribution reviews past achievements, summarizes the current experimental status, and discusses future prospects for electroweak physics with multiboson production at the LHC.

Speaker: Iro Koletsou (Centre National de la Recherche Scientifique (FR))

HEP2026IroKoletsou.pdf

11:50 AM Operational Experience and Performance of the ATLAS New Small Wheels in Run 3

During the second long shutdown of the LHC at CERN, the most important Phase-1 upgrade within the ATLAS experiment was the replacement of the two inner endcap stations of the Muon Spectrometer, with the New Small Wheels (NSW). Consisting of two novel detector technologies, the small-strip Thin Gap Chambers (sTGC) and the resistive strips Micromegas (MM), the NSW is targeting the rejection of fake muons in the endcap trigger region between pseudorapidity $1.3<|\eta|<2.4$. Furthermore, thanks to the excellent muon tracking and the improved triggering capability NSW contributes to the identification of muons coming from the interaction point with high precision.

Following an extensive initial commissioning effort to finalise the new detector systems, the technologies were successfully integrated into the ATLAS data acquisition and reconstruction frameworks in 2022, providing high tracking efficiency and good spatial resolution (improving over time and still under tuning). Moreover, the integration of the NSW into the trigger system, which started in 2023, was completed in 2024, leading to a significant reduction in fake triggers in the ATLAS Level-1 trigger rate and a further decrease in readout dead time. Despite the demanding challenges and increased luminosity delivered by LHC, the ATLAS NSW completed important milestones and successfully demonstrated excellent performance for over than three years.

This contribution presents a detailed report of the NSW tracking and triggering performance using pp collision data at 13.6 TeV between 2022 and 2026, along with the operational experience and planned improvements for the High-Luminosity LHC era.

Speaker: Stergios Tsigaridas (TRIUMF (CA))

2026-07-08_HEP2026_NSW_Stergios.pdf

12:10 PM CMS Tracking for the HL-LHC: A Heterogeneous Baseline with Extended Physics Reach

The unprecedented computational challenges of the High-Luminosity Large Hadron Collider, driven by the large number of simultaneous proton-proton collisions per bunch crossing, demand a fundamental change in reconstruction strategy. To address this, innovative algorithms are proposed for track seeding, building and fitting in Phase-2 CMS. For seeding, the Patatrack and Line Segment Tracking (LST) algorithms are optimized for parallel execution on GPUs. For building, the mkFit algorithm is vectorized for efficient CPU performance, and its score is further extended to track fitting, with initial measurements demonstrating a ~4× speedup for this task. Together, this new strategy can achieve up to a factor of 6× speedup of the full Phase-2 High Level Trigger (HLT) tracking sequence. Beyond computational efficiency, the combination also broadens the physics reach of CMS. LST, designed to build track candidates using outer tracker hits alone, naturally accommodates displaced track signatures and extends the acceptance for displaced tracks by ~60 cm. This talk presents the new baseline strategy for Phase-2 tracking in the CMS experiment, targeting the online HLT reconstruction and serving as the basis for the main iteration of offline tracking. Novel ML architectures based on Transformers are also discussed. These operate on LST segments rather than individual hits and use object condensation to create full tracks in a single inference step. They can achieve high reconstruction efficiency with low fake and duplicate rates, demonstrating promising preliminary results on a realistic CMS Phase-2 detector simulation.

Speaker: Manos Vourliotis (Univ. of California San Diego (US))

CMSTrackingForHLLHCHeterogeneousBaselineWithExtendedPhysicsReach_Vourliotis_HEP2026_260708.pdf

12:30 PM Next-Generation MDT DCS: Power Supply System Developments for the Phase-2 Upgrade

The background radiation levels expected at the High-Luminosity LHC (HL-LHC) will significantly exceed those for which the ATLAS Muon Spectrometer was originally designed. To meet this challenge, the Monitored Drift Tube (MDT) chambers in the barrel inner small sectors will be replaced by new small-diameter MDT (sMDT) chambers. This upgrade also enables the installation of a new triple-layer of Resistive Plate Chambers (RPCs) to enhance the Level 1 muon trigger system. Alongside the R\&D of these new detectors, the development of a robust and user-friendly Detector Control System (DCS) has been a critical priority. The DCS for the (s)MDT power supply follows the proven design philosophy, graphical interface, and command structure of existing legacy systems. Its primary goal is to ensure coherent and safe detector operation through continuous monitoring of key parameters and system status. In total, 96 new sMDT chambers will be integrated into ATLAS, complementing the existing MDT infrastructure. To validate both the detector technologies and control architecture, a dedicated test bench has been installed in Building 188, reproducing the complete power supply configuration for three sMDT chambers. This test setup serves not only as a validation platform but also as a reference system for all Muon sub-detectors across test areas. It supports pre-commissioning activities for Point 1 (P1) and acts as a training environment for new DCS experts, facilitating knowledge transfer and operational readiness.

Speaker: Ioannis Drivas-Koulouris (National Technical Univ. of Athens (GR))

hep_Ioannis Drivas Koulouris.pdf

hep_Ioannis Drivas Koulouris.pptx

12:50 PM Search for Higgs boson decay to a charm quark-antiquark pair via ttH production

The measurement of the Higgs boson coupling to second-generation quarks is a critical test of the Standard Model Yukawa sector. This talk presents an updated search for the Higgs boson produced in association with a top quark-antiquark pair (ttH), where the Higgs boson decays into a charm quark-antiquark pair (H --> cc), using the CMS detector at the Large Hadron Collider. Building upon the successful analysis of the full Run 2 dataset, which established the most stringent constraints to date on the Higgs-charm Yukawa coupling modifier κ_c, we extend this search into the Run 3 era. This update incorporates the larger Run 3 dataset and introduces various analysis improvements, including refined machine learning techniques for jet flavor identification and event classification, which are detailed in this talk.

Speaker: Nikolaos Plastiras (National and Kapodistrian University of Athens (GR))

ttHcc_HEP2026_NP.pdf

1:30 PM → 3:00 PM Lunch break - Restaurant (Level 1) - National Technical University of Athens

3:00 PM → 3:30 PM Keynote

Convener: Theodoros Alexopoulos (National Technical Univ. of Athens (GR))

3:00 PM Tracking and Particle Identification in FCC-ee

Speaker: George Iakovidis (Brookhaven National Laboratory (US))

2026_07_9_FCC_Tracking_PID_Iakovidis.pdf

3:30 PM → 4:30 PM FCC

Convener: George Stavropoulos (Nat. Cent. for Sci. Res. Demokritos (GR))

3:30 PM Toward a Superconducting Luminometer for FCC-ee: Device Physics, Detector Response, and Beam Performance

Superconducting nanowire single-photon detectors (SNSPDs) combine single-photon sensitivity with intrinsic timing capabilities approaching the SUB 10-PICOSSECOND scale, making them excellent candidates for a new generation of detectors for high-energy physics. Extending the exceptional single-photon performance of SNSPDs to relativistic charged particles enables precision timing luminometry for the Future Circular Collider (FCC), where luminosity measurements at the $10^{−4}$ precision level are required.

In this presentation we investigate the interaction of charged particles with superconducting nanowires using NbTiN, NbN and MgB2 SNSPD devices. Detector performance is studied using $^{90}Sr$ source and 160 GeV pion beam at CERN SPS within a EUDET-type MIMOSA-26 beam telescope, providing ∼5μm tracking resolution. Detection efficiency, spatial response, and timing characteristics as a function of nanowire geometry, bias conditions, and superconducting material properties are evaluated.

To interpret microscopic detection mechanisms, measurements are complemented by a comprehensive simulation framework, linking charged-particle energy deposition to superconducting dynamics and electronic signal formation. Energy deposition is modeled within GEANT4 using a custom extension of the Photo Absorption Ionization (PAI) model below the 10 eV limit of the Sandia tables. A Drude–Lorentz oscillator approach is implemented, enablling for the ultra low-energy excitation spectrum relevant for quasiparticle generation in superconductors to be resolved. The subsequent evolution of the superconducting condensate and transient resistive hotspot formation are studied via time-dependent Ginzburg–Landau simulations within the FEniCS framework, while SPICE-based circuit modeling reproduces expected pulse formation and readout behavior.

Together, these results provide direct insight into the coupling of ionizing radiation to superconducting nanowires and establish the physical foundations for SNSPD-based charged-particle detectors with ultrafast timing capabilities. Ongoing production efforts and upcoming test-beam campaigns are also discussed with emphasis on alternative geometries and phonon detection.

Speaker: Dr Vagelis Gkougkousis (University of Zurich)

HEP2026_Gkougkousis_Uploaded.pdf

3:50 PM Study of the $e^+ + e^- \rightarrow Z(l^+l^-)H(WW^*)$ decay in the 3-lepton final state at the FCC-ee

The FCC project is a proposed next-generation collider to be hosted in a new 91-km-long circular tunnel around CERN. This tunnel would initially host an electron-positron collider (FCC-ee), while later on would be an energy-frontier hadron collider (FCC-hh). During the first phase of FCC operation, the FCC-ee is designed to serve as a Higgs and electroweak factory, operating at several center-of-mass energies in the range of 91--365 GeV, aiming at high precision measurements and rare process studies.

Along with the clean environment of the final state in a lepton collider, FCC-ee is expected to produce large Higgs samples at centre-of-mass energies around 240 and 365 GeV, which will allow Higgs boson properties to be measured with exceptional precision. In particular, it is expected to generate approximately $2 \times 10^6$ $e^+ + e^- \rightarrow ZH$ events in three years of data taking at $\sqrt{s} = 240$ GeV. Although associated VH production has already been observed by the ATLAS and the CMS experiments, the large and clean ZH sample expected at FCC-ee, together with the much smaller backgrounds of the lepton-collider environment, will enable unprecedented precision in the measurement of Higgs boson properties. In addition, the measurement of the $H \rightarrow WW^*$ decay is particularly important, as the HWW coupling provides a key input to the interpretation of Higgs branching fractions and the determination of the Higgs total width.

In this presentation, we will report results from the study of the $e^+ + e^- \rightarrow Z(l^+l^-)H(WW^*)$ decay in the 3-lepton final state at the FCC-ee, using the recoil mass method, at $\sqrt{s} = 240$ and $365$ GeV.

Speaker: Michaela Arampatzi (National Technical Univ. of Athens (GR))

HEP2026_Analysis_Arampatzi.pdf

4:10 PM Impact of Power Supply Ripple on the new planned accelerator FCC-ee at CERN

The Future Circular electron-positron Collider (FCC-ee) is a proposed next-generation lepton collider designed to deliver very high luminosities across a broad beam-energy range. The extremely tight emittance and beam stability requirements of the machine make the control of time-dependent magnetic field variations critical. Power supply ripple introduces periodic fluctuations in the magnetic field of accelerator magnets, which translate into turn-by-turn orbit and tune modulations, potentially leading to emittance growth and beam degradation. In this work, single-particle tracking simulations within the Xsuite framework are used to assess the impact of such perturbations on beam quality for the Local Chromaticity Correction (LCC) optics design, with the aim of defining power converter specifications.

Speaker: Angelos Kastrinellis (National Technical Univ. of Athens (GR))

FCCee_Kastrinellis_2026.pdf

FCCee_Kastrinellis_2026.pptx

4:30 PM → 5:00 PM Coffee break

5:00 PM → 7:30 PM Detectors

Convener: Kostas Kordas (Aristotle University of Thessaloniki (GR))

5:00 PM Machine Learning Application for PICOSEC Signal Processing and Precise Timing

PICOSEC Micromegas (PICOSEC-MM) is a high precision timing Micro Pattern Gaseous Detector (MPGD) developed to reach time resolutions on the order of a few tens of picoseconds. Its operation is based on detecting Cherenkov light generated in a crystal radiator. The ultraviolet photons produced are converted into photoelectrons by a photocathode, and the signal is subsequently formed through a two stage amplification process.

Test beam studies using muon beams have shown that PICOSEC-MM prototypes can achieve a time resolution of about $ \sigma_t \approx $ 10ps when the avalanches from all photoelectrons are collected on a single pad this is referred to as the intrinsic resolution. In addition, the signal formation mechanism in PICOSEC-MM detectors has been thoroughly investigated and modeled, providing a detailed understanding of their timing behavior, including resolution and systematic time offsets.

However, maintaining this level of precision becomes significantly more challenging in multi pad PICOSEC-MM detectors, where photoelectrons are distributed across multiple anode pads. Traditional signal reconstruction methods, based on combining individual pad signals, suffer from systematic errors. These effects are particularly pronounced for non central tracks, i.e., when the muon track crosses the detector near pad boundaries. Such systematic time offsets are difficult to model and typically require large calibration datasets for proper parameterization.

In this work, we present a novel signal reconstruction framework based on Graph Neural Networks (GNNs). We demonstrate that this approach can provide unbiased, high precision estimates of the particle arrival time using raw digitized waveforms as input. By representing the detector’s multi pad signals as a graph, the network learns both spatial correlations and signal sharing effects. Moreover, by employing a Gaussian Negative Log Likelihood (NLL) loss function, the model simultaneously performs regression of the particle arrival time ($t_{GNN}$) and estimation of its uncertainty ($\sigma_{GNN}$) on a track by track basis.

Our results, based on muon beam data, show that the GNN architecture effectively recovers the intrinsic timing resolution (within $\sim$ 1 ps), even in cases where photoelectrons are shared across pad boundaries. In addition, the model’s self estimated uncertainty is shown to be a consistent and unbiased measure of the true timing resolution. Finally, the computational efficiency of the GNN framework enables fast inference, offering a scalable solution for real time particle timing.

Speaker: Angelos Tsiamis (Aristotle University of Thessaloniki (GR))

Machine_Learning_Application_for_PICOSEC_Signal_Processing_and_Precise_Timing.pdf

5:30 PM TestBeam Performance Studies of the ATLAS BCM’ Detector for the HL‑LHC Phase‑II Upgrade

The Beam Conditions Monitor (BCM’) is part of the Phase-II upgrade of the ATLAS detector for operation at the High-Luminosity Large Hadron Collider (HL-LHC). To evaluate the performance of the BCM’ detector, beam-test measurements have been carried out at the CERN SPS using the six-plane MALTA telescope. Data acquisition is performed with the DRS4 readout system, while track reconstruction and detector alignment are carried out using the Proteus framework. The reconstructed particle tracks are used to determine the hit detection efficiency, while the recorded analogue waveforms are analysed to evaluate the detector signal response and timing performance, including the time-of-arrival (ToA) and time-over-threshold (ToT) of the ATLAS-18 silicon mini-strip sensor read out by the Calypso ASIC under beam conditions. This contribution presents the beam-test setup, the data acquisition and reconstruction workflow, and preliminary results on detection efficiency and signal timing performance, providing important input for the validation of the BCM’ detector for the ATLAS Phase-II upgrade.

Speaker: Muhammad Basir Khan (Jozef Stefan Institute (SI))

Preliminary testbeam results for the BCM’ 3-chip module.pdf

5:50 PM GRANDProto300 - Status and Recent Progress

The Giant Radio Array for Neutrino Detection (GRAND) aims to detect ultra-high-energy neutrinos, cosmic rays, gamma rays, and radio transients using large arrays of autonomous radio antennas. A major milestone toward this goal is GRANDProto300, currently under deployment in Gansu, China.
The present GP65 array, consisting of 65 autonomous radio detection units, is being used to validate detector performance, autonomous triggering, timing synchronization, calibration procedures, and event reconstruction techniques under realistic operating conditions. Continuous data taking has enabled detailed studies of the radio background environment and detector stability.
Recent analyses have led to the identification of the first candidate cosmic-ray events recorded by the array, marking an important step toward the standalone radio detection of extensive air showers with GRAND technology. In parallel, significant progress has been achieved in detector calibration, reconstruction algorithms, and data analysis tools.
This contribution presents the current status of GRANDProto300, highlights recent results from the GP65 array, and discusses the next steps toward the full 300-antenna deployment and future large-scale GRAND observatories.

Speaker: Dr Apostolos Tsirigotis (Aristotle University of Thessaloniki (GR), Hellenic Open University)

Presentation_hep2026_GRAND_corr2.pdf

6:20 PM Detector Calibration and Precision Studies in GRANDProto300

The GRANDProto300 experiment is a major prototype of the Giant Radio Array for Neutrino Detection (GRAND), designed to validate the technologies and analysis methods required for large-scale radio detection of ultra-high-energy particles. Achieving nanosecond-level timing synchronization and a uniform detector response across the array is essential for accurate event reconstruction.
We present recent calibration studies performed with the current GP65 array in China. Timing calibration is based on dedicated beacon measurements and global-fit techniques, allowing the determination of relative station offsets and the validation of reconstruction performance using both fixed and roaming beacon data. In parallel, detector gain calibration is investigated through Galactic-noise observations and RF-chain monitoring, including temperature-dependent corrections and inter-station response homogenization.
The calibration studies presented here provide encouraging indications of improved timing consistency and detector response uniformity across the array. Ongoing work focuses on validating these results and quantifying their impact on air-shower reconstruction, as part of the broader effort toward the scientific goals of GRANDProto300 and future GRAND observatories.

Speaker: Dr Stavros Nonis (Hellenic Open University)

hep2026_grand_calibration_nonis.pdf

6:50 PM Giant Radio Array for Neutrino Detection (GRAND): Candidate selection and trigger optimization in the GP80 Prototype

The GRAND experiment aims to observe ultra-high-energy cosmic particles through the 10–200 MHz radio pulses of extensive air showers. The Grand Proto 80 (GP80) prototype is currently operating at Dunhuang as a testbed for the future full-scale array. We present an end-to-end analysis combining a Monte Carlo simulation chain with realistic GP80 noise, a directional reconstruction validated against the electrical field of the RF pulses simulated by ZHAireS, and a systematic optimization of the front-end trigger parameters. The research work aims to a calibrated trigger configuration and a hierarchical event-selection methodology applied to GP80 data, providing therefor the foundation for the upcoming sky-distribution and cosmic-ray identification studies.

Speaker: George Vittakis (University of the Aegean)

GRAND_HEP2026_v1.pdf

7:10 PM μNet: A Nationwide Cosmic-Ray Education and Research Network – Current Status and Future Upgrades

μNet (microNet) is a nationwide network of cosmic-ray detectors operating in high schools and educational institutions across Greece. The project aims to bring modern astroparticle physics closer to students and teachers through hands-on activities, real experimental data, and participation in authentic scientific procedures.
This contribution presents the current status of the μNet network and its educational and outreach activities. We also discuss recent and planned upgrades designed to enhance both its scientific and educational capabilities. These include the deployment of remotely operated muon telescopes and the planned integration of radio antennas based on technologies developed for the GRAND experiment. The new instrumentation will allow students and teachers to explore modern particle- and radio-detection techniques used in contemporary cosmic-ray and ultra-high-energy neutrino research.
By combining particle, muon, and radio detectors within a common educational framework, μNet is evolving into a unique platform that connects science education, outreach, and modern astroparticle physics research.

Speaker: Mr Leonidas Xiros (Hellenic Open University)

HEP2026_L.XIROS.pdf

HEP2026_L.XIROS.pptx

Thu, July 9

9:30 AM → 11:00 AM Keynote

Convener: Theodoros Alexopoulos (National Technical Univ. of Athens (GR))

9:30 AM The Status of the FCC & Plans for the Reference Design Phase

The 2026 update of the European Strategy for Particle Physics has recommended the high‑luminosity electron–positron Future Circular Collider (FCC‑ee) as the preferred option for CERN's next flagship project. This choice would enable a programme of precision measurements in particle physics while reinforcing Europe's leadership in the field. The tunnel constructed for FCC‑ee could also provide the infrastructure for a subsequent hadron collider, FCC‑hh, operating at the energy frontier. This presentation will outline the current status of the FCC design, including the principal elements of the proposed layouts, ongoing research and development for key enabling technologies, and considerations for a possible implementation timeline.

Speaker: Emmanuel Tsesmelis (CERN)

Tsesmelis NTUA HEP2026 July2026 FINAL.pdf

Tsesmelis NTUA HEP2026 July2026 FINAL.pptx

10:00 AM Concepts for Muon Systems at Future e+e- colliders

Speaker: Paolo Iengo (INFN)

PaoloIengo_HEP2026.pdf

10:30 AM Upgrade of the PADME experiment for the X17 Search

Speaker: Mario Antonelli (INFN e Laboratori Nazionali di Frascati (IT))

hep2026_antonelli.pdf

11:00 AM → 11:30 AM Coffee break

11:30 AM → 1:30 PM Experiments

Convener: Konstantinos Vellidis (National and Kapodistrian University of Athens (GR))

11:30 AM Search for heavy charged long-lived particles with the ATLAS detector using the full Run 2 dataset

This presentation outlines a search for stable, massive, and charged long-lived particles (LLPs) using the full Run 2 dataset of proton-proton collisions at $\sqrt{s}=13$ TeV collected by the ATLAS experiment. These particles are predicted by various extensions of the Standard Model, such as Supersymmetry (SUSY), and are expected to travel significantly slower than the speed of light ($\beta < 1$).
The search relies on measuring the velocity ($\beta$) of the particle candidates using time-of-flight (ToF) information from the Resistive Plate Chambers (RPCs) in the ATLAS muon spectrometer. Because standard reconstruction algorithms assume that particles travel at the speed of light ($\beta \approx 1$), a dedicated algorithm is used to correctly reconstruct the tracks of these slow-moving particles.
The background, mainly consisting of muons with mismeasured velocities, is estimated using a fully data-driven ABCD method, which is based on the independence of the track's transverse momentum ($p_T$) and velocity.
In the absence of a statistically significant excess of data over the expected background, 95% Confidence Level (CL) upper exclusion limits are established on the production cross-sections of benchmark SUSY models. Mass exclusion limits are set for staus, charginos, and gluino R-hadrons, improving upon previous results and demonstrating the high sensitivity of the RPC timing measurements.

Speaker: Leonidas Fountas (National and Kapodistrian University of Athens (GR))

LLP 9_7_26 EESFYE.pdf

LLP 9_7_26 EESFYE.pptx

11:50 AM Study of VH(→bb̄/cc̄) production in the ATLAS experiment

The associated production of a vector boson and a Higgs boson, VH(→bb̄/cc̄), provides a direct probe of the $κ_b$ and $κ_c$ couplings. The analysis targets the 0, 1, and 2 lepton channels, depending on the decay products of the vector boson, using proton-proton collision data collected by the ATLAS detector at √s = 13 Tev and 13.6 TeV. I will present updates to the analysis framework for Run 3, including the production of NLO electroweak corrections at 13.6 TeV and improvements to the jet energy correction procedure for b-tagged jets.

Speaker: Eleni Papadimitriou (Aristotle University of Thessaloniki (GR))

HEP2026 Papadimitriou.pdf

12:10 PM Evidence of Higgs boson inclusive production at high transverse momentum decaying to a pair of $b$-quarks with the ATLAS detector

Studies of the Higgs boson at high transverse momentum ($p_T$) are a valuable tool for the exploration of physics beyond the Standard Model. This work presents the first evidence of inclusive Higgs boson production at high $p_T$, decaying into $b\bar{b}$ quarks. The analysis is based on data from proton-proton collisions recorded by the ATLAS detector at CERN during Run 2 ($\sqrt{s} = 13\,\mathrm{TeV}$) and part of Run 3 ($\sqrt{s} = 13.6\,\mathrm{TeV}$), with a total integrated luminosity of $301\,\mathrm{fb}^{-1}$. The final state is reconstructed as a single large-radius jet, and the $b$-quark identification is performed by a transformer-based algorithm providing improved performance compared with previous analyses, and a significant background suppression. Moreover, a regression model and a muon-in-jet correction lead to sharper $p_T$ and mass resolution. The Higgs boson yield is extracted from a fit to the jet mass spectrum and the dominant multijet background is determined in a data-driven way. For $p_T > 450\,\mathrm{GeV}$, the measured yield relative to the Standard Model prediction is $1.53 \pm 0.27\,\mathrm{(stat.)}\,^{+0.33}_{-0.27}\,\mathrm{(syst.)} \pm 0.17\,\mathrm{(theo.)}$, with an observed (expected) significance of $3.8\sigma$ ($2.5\sigma$), relative to the background-only hypothesis. Results will also be presented in three $p_T$ intervals. Overall, the inclusive and differential results are compatible with the Standard Model predictions.

Speaker: Evripidis Koutsioumpas (National Technical Univ. of Athens (GR))

EvripidisKoutsioumpas_BoostedHbb.pdf

EvripidisKoutsioumpas_BoostedHbb.pptx

12:30 PM Study of pp→HH→bbγγ production at \sqrt{s}=13TeV and \sqrt{s}=13.6TeV using ATLAS simulations

Study of the $HH \to b\bar{b}\gamma\gamma$ decay channel in pp collisions at $\sqrt{s}=13TeV$ and $\sqrt{s}=13.6TeV$ using simulated events from the ATLAS experiment. A neural network classifier is trained on kinematic features to enhance signal-to-background discrimination. Background modeling and diphoton mass reconstruction assumptions, relevant to Higgs boson pair production searches, are investigated.

Speaker: Eliana Kapsali (Aristotle University of Thessaloniki (GR))

HEP2026_Kapsali.pdf

12:50 PM From Design File to SCADA: Automating OPC UA Server Integration in the ATLAS DCS with quasar and Cacophony

The ATLAS Detector Control System (DCS) is responsible for the safe and coherent operation of the ATLAS detector at CERN, supervising tens of thousands of hardware components spanning power supplies, cooling infrastructure, and front-end electronics to mention a few. The sheer scale and heterogeneity of the hardware demand a robust, maintainable middleware layer between the detector hardware and the WinCC OA SCADA system used for monitoring and control. OPC Unified Architecture (OPC
UA) serves this role. Developing OPC UA servers for heterogeneous detector hardware and integrating them into the SCADA environment at the scale of ATLAS is a significant engineering challenge. This talk resents two complementary tools developed at CERN that together address this challenge. The quasar framework enables rapid OPC UA server development through model-driven code generation, substantially reducing the effort required to build and maintain each server. Cacophony, a quasar extension, automates the equally demanding step of configuring the corresponding WinCC OA SCADA environment, eliminating a class of manual work that would otherwise scale with the size and complexity of each server deployment. The architecture and design
principles of both tools are presented, together with an overview of their application within the ATLAS DCS and recent developments that have extended their combined reach.

Speaker: Nikolaos Kanellos (National Technical Univ. of Athens (GR))

from_design_to_SCADA_hep_2026_nkanellos.pdf

1:10 PM Probing dark matter with novel signatures at the LHC

The 2HDMa model is one of the main models used in the searches for dark matter at the LHC. However the benchmarks used have already been ruled out to a large extent by Run 2 searches. In this talk, we will show that new signatures emerge when we lift the restrictions imposed on the current benchmarks. We analyse the decay patterns of the charged Higgs boson in benchmarks with a Type-I Yukawa sector and a non-degenerate BSM Higgs sector, demonstrating that they lead to new experimental signatures that remain unexplored.

Speaker: Ms Sofia Zioga (Aristotle University of Thessaloniki (GR))

2HDMa_charged_ATLAS_keynote coNF_compressed.pdf

1:30 PM → 3:00 PM Lunch break - Restaurant (Level 1) - National Technical University of Athens

3:00 PM → 4:30 PM Astroparticle and rare event searches

Convener: IOANNIS Gkialas (University of the Aegean (GR))

3:00 PM Latest results on the search for a diffuse astrophysical neutrino flux with KM3NeT/ARCA

KM3NeT/ARCA is a deep-sea neutrino detector that is currently under construction at a depth of roughly 3500 meters in the Mediterranean Sea, off the Sicilian coast, Italy. The detector is continuously collecting data while its instrumented volume keeps increasing. The main physics goals of KM3NeT/ARCA are the discovery of point sources of high-energy neutrinos and the characterization of the diffuse astrophysical neutrino flux. In this contribution, latest results will be presented for the search for a diffuse flux of astrophysical neutrinos with KM3NeT/ARCA data.

Speaker: Chrysovalantis Karagiannis (NCSR Demokritos)

Talk_HEP2026_CKaragiannis-5.pdf

3:20 PM Machine Learning applications for the design of LEMMOND, a water Cherenkov Detector to measure low energy neutrino interaction cross sections

ESSnuSB is a future long base-line (LBL) neutrino oscillation experiment, based on the low energy neutrino super-beam which can be generated using the European Spallation Source (ESS) Linear proton accelerator.The experiment is designed to measure the CP violating phase angle with an accuracy of less than $8^{\circ}$. To achieve such a goal, the very precise knowledge of the neutrino interaction cross section is extremely important.

LEMMOND is a water Cherenkov detector currently under development for measuring low energy neutrino interaction cross sections on water. The detector is planned to operate during the first development phase of the implementation of the ESS$\nu$SB project. This work demonstrates the application of Graph Neural Networks (GNNs) and other Deep Learning (DL) techniques for reconstructing LEMMOND signals, estimating neutrino energies, and extracting neutrino cross sections.

In this study, we use simulations of the Low Energy NuSTORM facility as a source of neutrino and antineutrino fluxes originating from muon decays, together with the GENIE event generator to simulate neutrino interactions within the effective volume of the LEMMOND detector. A modified version of Geant4 is employed to model in detail the propagation of charged particles in water, the production of Cherenkov photons, and the response of the photodetectors. The reconstruction of the charged lepton kinematic variables is based on GNN models trained on Geant4-simulated data and evaluated using statistically independent simulated samples.

Due to uncertainties in the exact neutrino direction and, more importantly, the impact of nuclear effects on the final state kinematics, a probabilistic Machine Learning (ML) approach has been advanced to provide a probability density function describing the experimental knowledge of the neutrino energy on an event by event basis. We demonstrate that this probabilistic approach can successfully reproduce the energy spectrum of the incoming neutrino flux.

Furthermore, the reconstructed information is used to estimate the energy dependence of the neutrino cross section. In addition, we investigate the size of systematic uncertainties arising from the modelling of nuclear effects by training the probabilistic neural network using different nuclear models.

Speaker: Ioannis Karakoulias

LEMMOND.pdf

3:40 PM New Physics in the Neutrino Fog Era of Dark Matter Direct Detection

The observation of solar $^8$B neutrinos in ton-scale xenon dark matter detectors has marked the beginning of the \emph{neutrino fog} era, establishing these experiments as complementary probes of neutrino and dark matter physics. In this talk, I will discuss recent constraints on new physics obtained from coherent elastic neutrino--nucleus scattering (CE$\nu$NS) measurements in XENONnT, PandaX-4T, and LUX-ZEPLIN [1]. I will present limits on non-standard neutrino interactions, with particular emphasis on scenarios involving light and heavy mediators. I will further show how such interactions can significantly modify the morphology of the neutrino fog, with important consequences for future direct detection searches [2]. Finally, I will outline new prospects within the DarkSPHERE programme for constraining effective field theory operators governing WIMP--nucleus interactions [3].

References

[1] V. De Romeri, D.K. Papoulias, F. Pompa, G. Sanchez Garcia, C.A. Ternes, Testing light and heavy vector mediators with solar CEνNS measurements, arXiv.org/pdf/2603.00554 [hep-ph], JCAP accepted
[2] V. De Romeri, A. Majumdar, D.K. Papoulias, R. Srivastava, New light mediators and the neutrino fog: Implications from XENONnT nuclear recoil data, JCAP 05 (2026) 093
[3] DarkSPHERE collaboration, in preparation

Speaker: Dr Dimitrios Papoulias (IFIC (CSIC/Valencia U.))

Papoulias_HEP2026.pdf

4:00 PM Sterile neutrino phenomenology

I review the status of sterile neutrino searches and discuss their appearance within D-brane string models. Finally, I present limits on their existence.

Speaker: Prof. CHRISTOS KOKORELIS (American University of Iraq-Baghdad)

CHR_KOKORELIS_TALK_EMP_9_JULY_2026_NEUTRINOS.pdf

4:30 PM → 5:00 PM Coffee break

5:00 PM → 7:20 PM Detectors

Convener: Ioannis Kopsalis (National Technical Univ. of Athens (GR))

5:00 PM AI-driven readout compression methods in Resistive Silicon Devices

Resistive Silicon Devices (RSDs), particularly AC-coupled Low Gain Avalanche Diodes (AC-LGADs), open the path for picosecond-level space and time (4D) tracking in high-energy physics (HEP) experiments such as those at the Large Hadron Collider (LHC), Electron-Ion Collider (EIC), and future (lepton) collider facilities. These sensors combine the fine spatial resolution of segmented detectors with the excellent timing performance of LGADs, achieving nearly 100% fill factor. Unlike conventional detectors, typically structured as linear strip arrays (1D) or pixel matrices (2D), RSDs offer a highly flexible geometry for readout pads, allowing for optimisation based on experimental demands.

When ionizing radiation interacts with these sensors, the generated charge spreads beyond adjacent pixels. This broad charge sharing, while beneficial for interpolation-based resolution enhancement, is complicated by reduced signal amplitudes and Landau fluctuations on pixels farther from the true hit location. To address these challenges, we study pixelated AC-LGADs fabricated at Brookhaven National Laboratory with different pad geometries, including square and triangular configurations with a 500 μm × 500 μm pitch, and analyse their impact on spatial resolution.

In contrast to previous studies, we leverage full-waveform information from each readout channel and utilise transformer-based architectures and RNNs to infer the full waveforms of the readout pads, given the hit’s position and AC-LGAD structure, thereby reconstructing the hit position. The higher precision achieved by the classical charge-imbalance and geometry-based matrix inversion methods is leveraged by the networks' ability to process more information, such as identifying optimal trade-offs between spatial granularity and data volume. Initial studies on Transient Current Techniques are used as inputs to further refine the algorithms with particle beams at SPS, where Landau fluctuations challenge the readout. We report the latest results from both TCTS and test-beam analyses, as well as the latest geometry-independent models.

Speaker: Gaetano Barone (Brown University)

hep2026_barone.pdf

5:30 PM The Design and Commission of the Beam Conditions Monitoring system for ATLAS ITk

For the High Luminosity phase of the Large Hadron Collider (HL-LHC), the ATLAS experiment will be equipped with a new state of the art all silicon inner tracker (ITk). This upgrade is designed to cope with the high density of particles on the detector, which will be increased by an order of magnitude, with neutron equivalent fluence reaching up to 3 × 10^15, total ionizing doses up to 3 MGy and charged particle flux up to 230 MHz/cm², at an average pile-up of μ = 200. The development of
electronics control systems under these conditions is a big engineering challenge and multiple sub-systems need to operate in parallel to assist the successful operation of the ITk. Such a subsystem is the Beam Condition Monitoring (BCM) system, that has a dual function. First,
it provides a complementary luminosity measurement (LUMI), contributing to the precision physics experiment of ATLAS. Second, it ensures detector safety through a fast beam abort capability (ABORT),
protecting sensitive frontend electronics from damaging particle showers and assure the continuous operation of ATLAS ITk for the upcoming years.
To address the engineering challenges, a set of custom ASICs with nanosecond-scale response and radiation hardness were designed in close accordance with the ITk Pixel Inner system architecture and
constraints, for both the system structure and the acquisition and control software. The detectors used in the BCM include mini strip arrays used in the strip detector part of the ITk, as well as custom pCVD detectors with ultra-fast timing response. In this work, the design, implementation, and testing strategies that were used in the BCM development are presented as well as the performance of the system compared to the design specifications.

Speaker: Vasileios Mouzakis (National Technical Univ. of Athens (GR))

The Design And Commission of the Beam Conditions Monitoring System for ATLAS ITK.pdf

5:50 PM Mitigation approach for silicon fractures in the ATLAS ITk strip tracker endcap module production

The ATLAS experiment is undergoing a major upgrade in preparation for the High-Luminosity LHC (HL-LHC), with the installation of the Inner Tracker (ITk). The outer tracking system includes the Strip Detector, which is installed in both the Barrel and the End-Cap (EC) regions.
The End-Caps consist of six disks on each side, populated with silicon modules mounted on support structures known as Petals.
During Quality Control procedures, including current–voltage (I–V) measurements and thermal cycling tests, early voltage breakdown was observed, in some cases below 100 V. This effect
was attributed to a mismatch in the coefficients of thermal expansion (CTE) between the silicon sensor and the attached electronics (hybrid and powerboard PCBs), leading to sensor fractures at low temperatures. The issue was more pronounced in the End-Cap regions due to their
geometry. A free-standing sensor would bend uniformly under thermal contraction; however, the presence of copper in flex circuits and the attached electronics constrains this behavior, resulting in
localized mechanical stress. These stress concentrations, particularly near attachment points, can exceed the fracture limit of the 320 μm thick n-in-p silicon sensors. To address this issue, an interposer solution was developed and implemented for the End-Cap
modules. The interposer consists of a 50 μm Kapton layer and a 100 μm soft silicone adhesive layer (SE445), placed between the sensor and the rigidly attached electronics. This configuration enables mechanical decoupling of the sensor from the electronics, reducing stress
transfer during thermal contraction. Additionally, the Kapton layer acts as a buffer, mitigating the effects of CTE mismatch between materials.
The results demonstrated a complete elimination of sensor cracking at the operational temperature of −35 °C. Furthermore, thermal cycling down to −70 °C showed no failures in 153 out of 154 modules.
These findings establish the necessity of interposer implementation for the successful production of End-Cap modules in the ITk, ensuring reliable detector operation under the demanding conditions of the HL-LHC.

Speaker: Stylianos Partsinevelos (National Technical Univ. of Athens (GR))

July2026Conference (1).pdf

July2026Conference (1).pptx

6:10 PM CMOS Active Sensor with Internal Amplification (CASSIA) characterization within CERN-DRD3 Collaboration

The CMOS Active Sensor with Internal Amplification (CASSIA) is an advanced detector concept developed within the DRD3 Collaboration at CERN. It represents a cutting-edge approach to monolithic pixel
design, enabling internal charge multiplication through engineered gain regions and supporting two distinct modes of operation. In the Low-Gain Avalanche Diode (LGAD) regime, the sensor operates below the hard
breakdown voltage, providing controlled gain typically in the range of 10–100. When biased at or above the breakdown voltage, the device transitions to Geiger-mode operation as a Single-Photon Avalanche
Diode (SPAD), achieving extremely high intrinsic gain. This capability can eliminate the need for external front-end amplification, significantly enhancing the signal-to-noise ratio and timing performance. The first prototype, CASSIA1, includes four 3 × 3 pixel matrices and 24 single-pixel structures with varying gain-layer geometries and electrode spacing, enabling a systematic study of their impact on gain, noise, and breakdown behavior.
CASSIA1 was subjected to detailed electrical (DC) characterization through current–voltage (IV) measurements to investigate the performance variations across the different matrices and to study the behavior of the two operating regimes. The measurements provide insight into leakage current, breakdown voltage, and the influence of gain-layer design on device stability. In addition, the internal gain across the
multiplication region was investigated using the Transient Current Technique (TCT), employing a focused laser with a full width at half maximum (FWHM) of 13 um. These measurements allow spatially resolved
characterization of the gain region and a deeper understanding of the charge multiplication mechanisms.

Speaker: Dimitrios Xynis (National Technical Univ. of Athens (GR))

cassia.conference_dimitriosxynis (1).pdf

6:30 PM Characterization of Low Gain Avalanche Detectors (LGADs) for the LHC

The continuous increase in luminosity at particle colliders worldwide requires the development of 4D (fast timing in addition to 3D resolution in space) silicon particle detectors. Improved timing resolution has
become essential, especially in regions close to the interaction point, where particle flux is higher. LGADs (Low Gain Avalanche Detectors) are silicon sensors with intrinsic charge multiplication and moderate
gain, making them a promising solution. They offer timing resolutions on the order of tens of picoseconds, allowing us better reconstruction of vertices. This work presents IV and CV measurements across wafers
for LGADs, along with gain characterization using TCT laser injections.

Speaker: Nikitas Kladas (National Technical Univ. of Athens (GR))

Characterization of Low Gain Avalanche Detectors (LGADs) for the LHC.pdf

8:30 PM → 11:30 PM Dinner - Kopsidi Restaurant, Kaisariani, 240 Ethnikis Antistaseos Avenue, 16122

Fri, July 10

10:00 AM → 11:00 AM Keynote

Convener: Fotis Farakos (Physics Division, National Technical University of Athens)

10:00 AM Dynamical extreme black hole horizons

Speaker: Achilleas Porfyriadis

10:30 AM Quantum vacua of string theory on Riemann flat manifolds

Speaker: Gianguido Dall'Agata (Universita e INFN (IT))

11:00 AM → 11:30 AM Coffee break

11:30 AM → 12:00 PM Keynote

Convener: Fotis Farakos (Physics Division, National Technical University of Athens)

11:30 AM A non-compact QCD axion

Speaker: Georgios Karananas

2026_HEP2026.pdf

12:00 PM → 1:30 PM Theory

Convener: Fotis Farakos (Physics Division, National Technical University of Athens)

12:00 PM Scale-separated vacua with extended supersymmetry

We propose the first examples of scale-separated vacua with extended supersymmetry. They
arise as circle compactifications of four-dimensional vacua of massive type IIA supergravity
with scale separation, upon introducing additional fluxes and sources. We provide both the
ten-dimensional solutions and the three-dimensional effective descriptions in terms of Kähler
potential and superpotential. The conformal dimensions of the putative dual two-dimensional
field theory appear not to be integers. The superpotential for the additional fluxes of one of
our models was guessed by ChatGPT and, to the best of our knowledge, it does not appear in
existing literature. Should these vacua be solutions of string theory, they would allow to address
the open problem of scale separation from the vantage point of extended supersymmetry.

Speaker: Alexandros Zarafonitis (Physics Division, National Technical University of Athens)

Scale_Separated_Vacua_With_Extended_SUSY.pdf

12:20 PM Hints for an AdS Universe from DESI

In this talk, I will present recent BAO results from DESI suggesting that dark energy may be evolving, with low redshift supernova data playing an important role in this indication. I will briefly discuss equation of state parametrizations and focus on a simple quintessence model with a Higgs like potential. This approach suggests that the Universe may already be in, or could evolve into, an AdS phase, potentially leading to a future cosmological collapse.

Speaker: Ioannis Gialamas (National Institute of Chemical Physics and Biophysics)

talk_HEP_Gialamas.pdf

12:40 PM SMEFT Analysis of Exclusive Higgs Decays H → Mγ

Rare exclusive Higgs decays H → Mγ, with M = ρ, ω, ϕ, J/ψ, Υ, provide a clean probe of Higgs–quark interactions and possible SMEFT effects. We study the dimension-six operators contributing to these channels and classify their impact into direct, indirect and dipole-contact contributions. Particular emphasis is placed on electroweak quark dipole operators, which can modify the branching ratios and are constrained by Higgs, electroweak and flavour observables, including B → Xsγ for third-generation down-type dipoles. The analysis shows that H → Mγ decays offer complementary sensitivity to CP-even flavour-diagonal electroweak dipoles, especially for light- and second-generation quarks.

Speaker: Dimitrios Beis

h_to_vgamma_HEP2026.pdf

1:30 PM → 3:00 PM Lunch break - Restaurant (Level 1) - National Technical University of Athens

3:00 PM → 3:20 PM Theory

Convener: Fotis Farakos (Physics Division, National Technical University of Athens)

3:00 PM Emergence of a $1/r$ Gravitational Regime from a Corrected Relativistic Structure

We present recent developments of a corrected relativistic framework based on a structural re-examination of the spacetime–energy coupling in General Relativity. The approach replaces the standard static description of matter with a fully dynamical representation of energy, leading to additional first-order structural contributions in the Einsteinian formulation.

A recent technical advance resolves non-commutativity issues associated with the composition of energy distributions in curved spacetime, providing a consistent framework in which the relativistic structure can be treated without ad hoc regularization procedures.

Within this formulation, a previously introduced “Surrounding” field emerges as a direct structural consequence of the modified spacetime–energy relation. The standard Einsteinian limit is recovered in configurations at scales below 15 kpc or in the presence of a constant Surrounding field, while systematic deviations appear in large-scale (>15 kpc) configurations with varying Surrounding.

A central result of the framework is the emergence of an effective long-range gravitational regime characterized by an asymptotic transition toward a $1/r$-like behaviour in large-scale systems dominated by a single central attractor. This behaviour arises as a structural large-scale limit of the theory.

In this context, the acceleration scale $a_0$ plays the role of a universal transition parameter between regimes. The associated scale $a_0/G$ defines an effective density scale governing equilibrium configurations, characterizing gravitational regimes within the framework.

The resulting effective dynamics exhibits MOND-like behaviour in large-scale systems dominated by a single central attractor, corresponding to the weak-field, low-acceleration regime of the theory. A full derivation of the Tully–Fisher relation is left for future work.

Speaker: Frederic Lassiaille

HEP2026Surrounding.pdf

3:20 PM → 4:30 PM Experiments

Convener: Konstantinos Theofilatos (National and Kapodistrian University of Athens (GR))

3:20 PM Searches for High-Mass Resonances in the ZZ→4ℓ Final State with the ATLAS Experiment

A search for heavy resonances decaying into a pair of Z bosons leading to the $\ell\ell\ell\ell$ final state is presented, using the Run3 data collected by the ATLAS detector at √s = 13.6 TeV. The results are interpreted separately for the ggF and VBF production modes, with events being classified into ggF-enriched and VBF-enriched categories. Reducible backgrounds from processes such as Z+jets and $t\bar{t}$ are estimated using a data-driven Fake Factor method. The statistical model is built and validated using Run 3 data, and expected limits are extracted as a function of the resonance mass.

Speaker: Konstantinos Sioulas (National and Kapodistrian University of Athens (GR))

HEP2026_Sioulas.pdf

3:40 PM Search for exotic decays of the Higgs boson to a pair of new light bosons in VH, H→XX→4b with the CMS experiment

Many extensions of the Standard Model predict exotic Higgs boson decays into new light scalar or pseudo-scalar particles. This contribution presents a search for the decay H → XX → bbbb in the associated production mode (VH), using Run 3 proton-proton collision data collected with the CMS detector at the LHC. The analysis targets final states containing four bottom quarks and, for the first time in CMS, simultaneously explores both the Z(ℓℓ)H and Z(νν)H associated production channels, where the leptonic and invisible decays of the Z boson provide efficient event triggering and complementary sensitivity.

Special emphasis is placed on the low-mass regime (mX < 30 GeV), where the two b quarks from each (X) boson are highly collimated and often reconstructed as a single jet. To enhance the sensitivity in this challenging topology, the analysis employs dedicated transformer-based double-b tagging algorithms, advanced jet substructure techniques, and multivariate signal discrimination. This search extends the CMS exotic Higgs program and improves sensitivity to light bosons in previously unexplored regions of parameter space.

Speaker: Artemis Taxeidi (National Technical Univ. of Athens (GR))

HEP2026_H4b_100726.pdf

4:00 PM Enhancement of the ATLAS NSW DCS performance and implementation of DCS for experimental setups

During the second long shutdown of the LHC at CERN, the most important Phase-1 upgrade within the ATLAS experiment was the replacement of the two inner endcap stations of the Muon Spectrometer with the New Small Wheels (NSW), in preparation for the High-Luminosity period (HL-LHC). The NSW consists of two novel detector technologies, the MicroMesh Gaseous Structure (Micromegas/MMG) and the small-strip Thin Gap Chambers (sTGC). Although MMG detectors are primarily used for tracking and sTGCs for triggering, the two technologies are complementary. Therefore, as an integrated detector system, the NSW provides excellent muon tracking and triggering performance, contributing to the high-precision identification of muons originating from the interaction
point.

Due to NSW complexity and the need for long-term operation, a sophisticated Detector Control System (DCS) has been developed. After four years of data-taking, the NSW DCS has supported successfully the daily operation of the detector. At the same time and based on the users’ experience, new tools and automated mechanisms were developed to improve the NSW DCS performance. In parallel, three development set-ups were established to investigate different parameters affecting the detector performance. The first one, dedicated to MMG, used to study the detector response under high-flux photon irradiation and different detector configurations in comparison with the MMG detectors used in the ATLAS experiment. The rest are used to facilitate the sTGC HV failure mitigation strategy.

The first part of the presentation will focus on the new tools and automated mechanisms developed to improve the performance and operational stability of the ATLAS NSW DCS, while the second part presents the implementation of the DCS in experimental setups aimed at optimizing the operation and long-term performance of the ATLAS NSW detector system.

Speaker: Michaela Arampatzi (National Technical Univ. of Athens (GR))

HEP2026_NSWDCS_Arampatzi.pdf

4:30 PM → 5:00 PM Coffee break

5:00 PM → 5:40 PM Experiments

Convener: Konstantinos Theofilatos (National and Kapodistrian University of Athens (GR))

5:00 PM Logistics in ATLAS ITk Upgrade Project: A challenging task for a global collaboration of Institutes

The ATLAS ITk System is an all-silicon tracker being built for the Phase-II upgrade of the ATLAS experiment with a total detector surface of almost 180 m2. The ITk is being built by more than 1000 researchers from 113 institutes in 22 countries around the globe. The ITk parts, built in institutes and industry, require complex logistics to ensure timely availability at the different sites.

The whole procedure is not governed by standard logistics procedures found in literature, but taking into account the capabilities and the capacity of each collaborating Institute, ignoring its position on the map. Industrial collaborators deliver sensitive, usually small components to CERN, from where they need be shipped to different institutes, sometimes returning to CERN to be shipped again to other institutes, depending on their planned journey through different sites during their assembly and quality control steps. Some challenging procedures such as CERNs international organization status, temporary exports and dual-use material control rules as well as a very precise tracking follow up prior to any assembly, do make this effort heavier than may be expected.

On the other side, when large and very fragile components with dimensions in the order of meters, are delivered to CERN, corresponding handling and storing procedures must be organized.

The project decided that a logistics team, exclusively dedicated to ATLAS ITk Upgrade, be formed and support all these complex logistics activities during the prototype and construction period, and using CERN as a hub for them.

Speaker: Spyridon Kompogiannis (Aristotle University of Thessaloniki (GR))

ATLAS_ITk_Logistics_HEP_2026_Spyridon_Kompogiannis_10th_of_July_2026_v2.pdf

5:20 PM A Fast Analytical Multiphysics Model for Laser-Driven Particle Acceleration Toward Pair Production Studies

Laser-driven particle acceleration provides a promising route to accessing extreme field conditions relevant to high-energy physics and laboratory studies of electron–positron plasma formation.
However, exploring these regimes remains challenging, as existing modeling approaches are both computationally intensive and inherently fragmented: particle-in-cell (PIC), magnetohydrodynamic
(MHD), and Monte Carlo methods each resolve specific aspects of the interaction, but their separation prevents a unified, end-to-end description of the full laser–matter interaction sequence
and limits predictive optimization. Here, we present a fast, analytical, end-to-end multiphysics framework that captures the complete evolution of laser–target interactions in solid-density materials, from energy deposition and plasma formation to the generation of accelerating fields and high-energy particle emission. The model provides a self-consistent, physics-based description of the dominant mechanisms governing energy
transfer and particle acceleration, while remaining computationally efficient and scalable across a wide range of laser conditions.
Although less detailed than fully kinetic approaches, the framework enables rapid exploration of parameter space and delivers an end-to-end, predictive overview of laser-to-particle coupling. It has been validated against experimental data from multiple high-power laser facilities, demonstrating strong predictive capability.
As a case study, we use this model to identify regimes that enhance hot-electron generation and energy coupling, key prerequisites for secondary processes such as Bremsstrahlung-mediated positron production. The model thus provides a practical tool for designing and optimizing experiments approaching pair-production conditions, enabling controlled access to regimes relevant for high-energy-density physics and laboratory pair-plasma studies.

Speaker: Dr Vasiliki Alexopoulou (National Technical Univ. of Athens (GR))

Alexopoulou_HEP2026.pdf

5:40 PM → 7:00 PM Detectors

Convener: Ioannis Kopsalis (National Technical Univ. of Athens (GR))

5:40 PM Characterization of SiPMs using Radiation Sources for Quantum Random Number Generation

In this work, a Silicon Photomultiplier (SiPM) detector was
assembled and experimentally characterized using the CAEN Premium SiPM setup. The detector response was studied under controlled conditions using pulsed LED laser illumination, enabling the extraction of key SiPM parameters such as gain, dark count rate, optical crosstalk, after-pulsing probability, and charge resolution. An absolute energy calibration was also performed using a (¹³⁷Cs) γ-ray source coupled to a LYSO scintillator, demonstrating the spectroscopic capabilities of the system through the identification of characteristic photoelectric
peak and Compton continuum. In addition, the intrinsic noise properties of the SiPM were analyzed as a potential entropy source for Quantum Random Number Generation (QRNG). Overall, this work provides a comprehensive performance evaluation and experimental characterization of the SiPM, establishing a validated framework for detector studies, scintillation-based spectroscopy, and future quantum applications.

Speaker: Evangelos Xirotyris Chrysos (National Technical Univ. of Athens (GR))

HEP2026_Vagelis_Xirotyris.pdf

6:00 PM Environmental Monitoring for the ATLAS ITk Barrel Integration

As part of the preparations for the High-Luminosity Large Hadron Collider (HL-LHC), the ATLAS experiment is undergoing major detector upgrades to cope with the significantly increased collision rates and data volumes expected during future operation. One of the most important upgrades is the replacement of the current Inner Detector with the new all-silicon Inner Tracker (ITk), designed to operate under the much harsher radiation and occupancy conditions of the HL-LHC.

During the integration and testing phases of the ITk Barrel, maintaining stable environmental conditions is essential to prevent condensation and ensure the safe operation of detector components. To support these activities, an Environmental Safety System (ESS) was developed for the ITk Barrel in the SR1 integration facility at CERN. The system is based on a Vaisala Indigo 520 transmitter coupled to two DMP8 dew-point probes installed on opposite sides of the detector volume. It continuously monitors dew point, temperature, and relative humidity, while dedicated relay outputs provide robust safety interlocks to the cooling plant.

Monitoring, alarm handling, and data archiving are implemented through a WinCC OA application using Modbus TCP/IP communication. To validate the system performance and determine the lowest achievable dew point inside the detector volume, the barrel was flushed with dry air while environmental parameters were continuously recorded. Long-term operation of the setup also enabled the identification and mitigation of effects that could potentially lead to spurious cooling interlocks.

The ESS has subsequently been integrated into the Integration Finite State Machine (FSM) of the ITk Strip Barrel Detector Control System (DCS), providing environmental supervision and safety functionality during detector testing and commissioning. Additionally, a dedicated setup was developed to measure the gas leak rate of the Barrel Outer Cylinder, providing valuable input for the assessment of the detector's environmental integrity and long-term operational stability.

The developed ESS and gas-leak measurements systems constitute key elements of the ITk Strip Barrel integration infrastructure, providing reliable detector protection, continuous environmental supervision, and valuable operational feedback during the detector integration, validation, and commissioning phases at CERN. The design, implementation, commissioning, and operational experience of these systems, as well as their contribution to the safe integration and testing of the ITk Strip Barrel at CERN, will be presented.

Speaker: Georgios Katselis (National Technical Univ. of Athens (GR))

HEP_2026_KATSELIS.pdf

HEP_2026_KATSELIS.pdf

6:20 PM Development and Characterization of an Environmental Parameter Monitoring System for the ATLAS ITk

As the ATLAS experiment prepares for the High-Luminosity upgrade of the Large Hadron Collider (HL-LHC), the transition to the new, all-silicon Inner Tracker (ITk) presents significant engineering challenges. Operating in a high-radiation environment, the ITk requires constant and precise environmental monitoring to protect its sensitive silicon sensors. Specifically, keeping the dew point well below ambient temperatures is vital to prevent condensation, which could lead to catastrophic electrical failures within the detector. To address these requirements, the ATLAS Sniffer system is employed to continuously sample the detector’s internal atmosphere and monitor humidity levels
with high reliability. This work focuses on the design and implementation of a high-precision monitoring interface
that bridges industrial sensing technology with the ITk’s specialized data acquisition system. The core of this work involved developing a custom Signal Conditioning Board (SCB) to interface a
Vaisala dew point transmitter with the Environmental Monitoring Readout Board (EMRB). By employing a dual-stage amplification strategy with a zero-drift amplifier, the system converts the sensor’s 4-20mA current loop into a 0-2.5V signal, matching the dynamic range of the EMRB’s
24-bit Analog-to-Digital Converter (ADC).
To manage the data flow, a Raspberry Pi 4 was integrated to handle the communication between the hardware and the end-user. The software layer was implemented in C++, utilizing memory mapping for direct access to the SoC registers, ensuring high-performance SPI communication and
deterministic control over EMRB’s ADC and multiplexers. This low-level approach allows for the efficient execution of complex, high-order polynomial models that translate raw sensor readings into accurate dew point and relative humidity values.

Speaker: Nikolaos-Anastasios Kontogiorgis

HEP2026-Nikos_Kontogiorgis.pdf

6:40 PM Contactless Determination of Martensitic Phase in Austenitic Steels

In this presentation we report results on the detection of martensitic phase in the SS316 austenitic steel grade during stress – strain and non-monotonic stress tests. Although the austenitic steels do not exhibit magnetic properties, the accumulated stresses due to their stress or fatigue result in martensitic phase transformation. The development and increase of the martensitic phase is the indication of the austenitic steel failure process, that has been studied in this work. During stress and fatigue, the three magnetic field components on the surface of the steel dogbone were monitored using AMR sensors with sensitivity and dynamic range of 100 nTHz^{-1/2} and +10 mT respectively, allowing for the indirect observation of the martensitic phase development on the surface of the austenitic steel dogbone. This response appeared to be monotonic up to the ultimate tensile stress (UTS) point in the stress – strain measurement. Furthermore, the non-monotonic low-frequency cyclic stress resulted in a periodic stress effective field effect at least 18,000 cycles before the steel failure, allowing for time to perform emergency actions in corresponding engineering applicatins.

Speaker: Tatiana Damatopoulou

Tatiana_Presentation austenites (4).pdf

7:00 PM → 7:20 PM The History of High Energy Physics at Athens NTU: Η Ιστορία της Πειραματικής Φυσικής Υψηλών Ενεργειών στο Εθνικό Μετσόβιο Πολυτεχνείο

7:00 PM Πειραματική Φυσική Υψηλών Ενεργειών στο ΕΜΠ

Τη δραστηριότητα στην πειραματική Φυσική Υψηλών Ενεργειών (ΦΥΕ) στο ΕΜΠ την ξεκίνησε ο αείμνηστος καθηγητής Αναστάσιος Φίλιππας. Ο Φίλιππας το 1958 πήρε υποτροφία (πρόγραμμα Fulbright, ΗΠΑ) και έκανε διδακτορικό στο πανεπιστήμιο Carnegie Institute of Technology (Carnegie Mellon University) στην πόλη Pittsburgh της πολιτείας Pennsylvania των ΗΠΑ. Το 1964 διορίστηκε στο Δημόκριτο ως ερευνητής. Το 1975 διορίζεται Έκτακτος Καθηγητής στο ΕΜΠ όπου πλαισιώθηκε με νέους ερευνητές που προσέλαβε και σχημάτισε μια πειραματική ομάδα ΦΥΕ. Από τότε (1975) αρχίζει η πειραματική δραστηριότητα του ΕΜΠ στη ΦΥΕ με πειράματα στο CERN. Στη συνέχεια αναφερόμαστε σε μερικά πειράματα στα οποία συμμετείχε η ομάδα του ΕΜΠ.

Speaker: Manolis Dris (National Technical Univ. of Athens (GR))

fyeemppdf.pdf

omilia_sto_synedr_fye_sto_emp.pdf

7:20 PM → 9:20 PM Hellenic Society for the Study of High Energy Physics

Convener: Katerina Zachariadou (University of West Attica (GR))

2026 Ηesshep report.pdf

ΕΕΣΦΥΕ-Σχέδιο Νέου Καταστατικού-2-7-2026.pdf

Sat, July 11

10:00 AM → 11:30 AM Goodbye

Conveners: Ioannis Kopsalis (National Technical Univ. of Athens (GR)), Theodoros Alexopoulos (National Technical Univ. of Athens (GR))