Advances in QCD at the LHC and the EIC

9 Nov 2025, 09:00 → 15 Nov 2025, 23:30 America/Sao_Paulo

CBPF, Rio de Janeiro

Jointly with the CLAF Symposium on Opportunities for Latin-American Cooperation in High Energy Physics with CERN

 

 

The purpose of the workshop on Advances in QCD at the LHC and the EIC is to stimulate discussions between experimentalists and theorists in photon exchange and beyond standard model physics, flavour physics, diffractive hadronic physics, QCD dynamics at low-x, parton saturation and exciting problems in QCD at the Tevatron, LHC, RHIC and the future EIC. 

The workshop will be held jointly with the CLAF Symposium on Opportunities for Latin-American Cooperation in High Energy Physics with CERN, to take place on November 14, 2025.

The conference venue will be at CBPF, Rio de Janeiro, from November 9 in the evening (date of arrival) to November 15 in the evening Please register as soon as possible since this is a highly touristic region. 

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Registration Fees

The registration fees will be 400 US dollars for participants of the workshop, and 125 US dollars for companions. The fees cover the conference room, all coffee breaks, the workshop dinner and workshop cocktail. Reduced fees of respectively 250 US dollars and 125 US dollars will be available for participants from Latin America and students. 

The conference registration fee can be paid via this PayPal link (international participants) or via this link (participants from Brazil). 

The fee payments received from October 25th onwards will have an extra charge of 10%. 

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Social activities

An optional tour of Rio will be proposed for people interested.

In addition, a post-conference tour to Paraty, a UNESCO heritage list colonial city, will be proposed after the workshop. We will spend two nights in Paraty to visit the city and there will be a boat tour included in the tropical islands close to Paraty.

The full registration fee covers the workshop dinner on Thursday 13th November.  For companions or participants who payed the reduced fee or who got a fee exemption, the dinner can be purchased separately until Tuesday November 11th at noon.

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This workshop is part of a series of workshops related to the LHC Forward Physics Working Group at CERN that took place at CERN, Switzerland in 2019, 2020, 2024,  Madrid, Spain, in 2017, Trento, Italy, in 2022, Bad Honef, Germany in 2023.

 

The Workshop is organized and sponsored by FAPESP, FAPERJ, CAPES, CNPq, The University of Kansas, ExtreMe Matter Institute at GSI (EMMI), Brookhaven National Laboratory and the I.ANN QCD network.

   

 

         

 

 

 

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Administrative_Circular_SymposiumCLAF-CERN-1.pdf

Poster - Advances in QCD at the LHC and the EIC

Monday 10 November

08:00 Registration

Welcome

Presentation of the IANN QCD Network

1 Presentation of the IANN QCD Network

Speaker: Daniel Tapia Takaki (University of Kansas)

PDFs, Jets and Nuclear Structure

2 Jet cross section measurements and PDF constraints at LHC

27+3'

Speaker: Dr Francesco Giuli (INFN e Universita Roma Tor Vergata (IT))

3 Jet shape and substructure measurements at the LHC

27+3'

Speaker: Christophe Royon (The University of Kansas (US))

4 Revisiting constraints on proton PDFs from HERA DIS, Drell-Yan, W/Z Boson production, and projected EIC measurements

23+2'
We present new parton distribution functions (PDFs) at next-to-leading order (NLO) and
next-to-next-to-leading order (NNLO) in perturbative QCD, derived from a comprehensive QCD analysis
of high-precision data sets from combined HERA deep-inelastic scattering (DIS),
the Tevatron, and the Large Hadron Collider (LHC). To improve constraints on quark
flavor separation, we incorporate Drell-Yan pair production data, which provides
critical sensitivity to the quark distributions. In addition, we include the latest
W and Z boson production data from the CDF, D0, ATLAS, and CMS collaborations,
further refining both quark and gluon distributions. Our nominal QCD fit
integrates these datasets and examines the resulting impact on the PDFs and their
associated uncertainties.
Uncertainties in the PDFs are quantified using the Hessian method, ensuring robust
error estimates. Furthermore, we explore the sensitivity of the strong coupling
constant, (\alpha_s(M_Z^2)), and proton PDFs in light of the projected measurements
from the Electron-Ion Collider (EIC), where improvements in precision are expected.
The analysis also investigates the effects of inclusive
jet and dijet production data, which provide enhanced constraints on the gluon PDF and (\alpha_s(M_Z^2)).

Speaker: Maral Salajegheh (HISKP, University of Bonn)

10:45 Coffee break

PDFs, Jets and Nuclear Structure

5 Predictions for dimuon production in high-energy neutrino-proton collisions using the color dipole model

18+2'
Interactions of high-energy neutrinos with matter can be studied through the angular separation observed in dimuon production, an observable particularly sensitive to the transverse momentum dynamics of partons. In this work, we develop a Monte Carlo event generator based on the color dipole model, interfaced with Pythia8 for parton showering and hadronization simulations, to predict dimuon production cross sections in neutrino-proton collisions at energies relevant to IceCube and future detectors. The color dipole formalism generates larger transverse momentum compared to standard Pythia predictions, enhancing the yield of angularly separated high-energy muons.

Speaker: Emmanuel Gräve de Oliveira (UFSC, Brazil)

6 Effects of the initial condition on multiplicity distribution in pPb collisions

18+2'
In this work we discuss the possibility of accessing the initial geometric shape of the proton in proton-nucleus collisions at the LHC. More specifically, we want to test the configuration in which the proton is made of three quarks linked by a Y-shape gluon string, called baryon junction. This initial state spatial configuration has been used in the past to describe data on baryon rapidity distributions, diffractive $J/\psi$ production and multiplicity distributions in pp collisions. In spite of its success in explaining the data, the evidence of the baryon juntion still needs confirmation. Further studies will be undertaken at the electron-ion collider. In this work we study multiplicity distributions measured in pPb collisions. We use different initial state geometries as input in the MC-KLN Monte Carlo event generator which implements the $k_T$ factorization formalism of the CGC with KLN unintegrated gluon distributions. We find that the hard sphere and Gaussian proton configurations are incompatible with the data. The baryon junction configuration can describe the data provided that fluctuations in the saturation scale (also called "intrinsic fluctuations'') are included.

Speaker: Richard Terra de Oliveira (Instituto de Física da USP)

7 Momentum fraction and hard scale dependence of double parton scattering

18+2'
The effective cross section of double parton scattering in high-energy hadron collisions has been measured in proton--proton collisions, with significant variation among final-state observables, contrary to the idea of a universal value. Building upon our previous work, we incorporate the dependence on the parton longitudinal momentum fraction x and the process energy hard scale μ into the transverse part of the double parton distributions, using a Gaussian profile. Employing the experimental data from the LHC and Tevatron experiments (covering different processes, kinematic configurations, and center--of--mass energies), we perform a global fit of the model, extracting the parameters that describe the proton structure. With this result, it becomes possible to calculate the effective cross section for other observables, and we provide predictions for future measurements at the LHC.

Speaker: Joao Vitor Lovato (Universidade Federal de Santa Catarina)

8 Hadrons in Minkowski space

18+2'

Speaker: Tobias Frederico

12:35 Lunch

EIC

9 Parton distribution functions and fragmentation functions at a future Electron-Ion Collider

I will review the calculation of parton distribution functions of meson derived from either light-front wave functions or from a cut diagram based on the optical theorem applied to Compton scattering. The latter approach can also be used to compute an elementary fragmentation for the case of a quark into a meson. However, there is no reason a high-energy quark should fragment into just one meson, and one must consider a tower of final
hadrons described by jet functions. These one-dimensional probability functions are of particular interest to the science program of the Electron-Ion Collider (EIC).

Speaker: Prof. Bruno El-Bennich (Federal University of São Paulo)

Saturation and UPC

10 Review of UPC results at the LHC

23+2'

Speaker: Luis Alcerro Alcerro (The University of Kansas (US))

11 Updates on particle production in UPCs

23+2'

Speaker: Fernando Navarra

12 Overview of UPC and photonuclear results from CMS

18+2'

Speaker: Saray Arteaga Escatel (The University of Kansas (US))

13 Investigating the inclusive D0 and B0 photoproduction in ultraperipheral collisions

18+2'
The inclusive $D^0$ and $B^0$ photoproduction in $pPb$ and $PbPb$ collisions at the center - of - mass energies of the Large Hadron Collider (LHC) is investigated considering the color dipole S - matrix approach. The analytical expressions for the differential distributions are derived in the transverse momentum space and predictions for the rapidity and transverse momentum distributions are presented considering distinct models for the unintegrated gluon distribution of the target, assuming linear and nonlinear dynamics. A comparison of these predictions with the recent CMS data for $D^0$ photoproduction is also performed. Our results indicate that a detailed analysis of this observable will be very useful to improve our understanding of the strong interaction theory at high energies and in a nuclear medium.

Speaker: Luana Santana (Universidade Federal de Pelotas)

16:10 Informal discussions and Refreshments

Tuesday 11 November

08:00 Registration

Saturation and UPC

14 Dissociative associated mu- mu+ and J/psi production via double parton scattering in nucleus--proton ultraperipheral collisions

18+2'
At high energies, double parton scattering plays a crucial role in studying the double parton distribution function for the proton. Extracting this distribution is highly complex. To address this challenge, we propose a novel channel to further investigate it: the associated production of mesons and leptons, such as $J/\psi$ and $\mu^-\mu^+$ pairs, in ultraperipheral $Ap$ collisions. In this work, we analyze the kinematic dependence of the effective cross-section and derive an analog to the standard pocket formula commonly used for central $pp$ collisions.

Speaker: Edgar Huayra

15 Results from Ultra-peripheral Collisions at LHCb

23+2'

Speaker: Murilo Santana Rangel (Federal University of Rio de Janeiro (BR))

16 NLO BFKL evolution and the energy dependence of exclusive heavy vector meson photoproduction cross-sections

23+2'

Speaker: Martin Hentschinski (Universidad de las Americas, Puebla)

17 Photo- and electroproduction of light vector mesons in the dipole picture

18+2'
We study the photoproduction of light vector mesons considering the proton and the nucleus as the target. Utilizing the dipole picture and the wave functions obtained via AdS/QCD, we were able to describe the HERA γp data and extend the analysis to the nuclear case considering the Glauber–Gribov formalism supplemented by an effective suppression factor RG accounting for the gluon shadowing correction. The results obtained in the nuclear regime are compared to the recent Pb Pb → ρ Pb Pb LHC data and predictions of other light vector mesons are made.

Speaker: Haimon Trebien (Universidade Federal de Santa Catarina)

10:30 Coffee break

QGP and Extreme Matter

18 Heavy-Flavour and Quarkonia Production in pp and p-Pb Collisions with ALICE at the LHC

23+2'

Speaker: Cristiane Jahnke Fiorini Da Silva (University of Campinas UNICAMP (BR))

19 Recent results from O/Ne runs in the CMS experiment

23+2'

Speaker: Dr Georgios Krintiras (The University of Kansas (US))

20 Study of the thermodynamic properties of hot QCD matter in the CMS experiment

18+2'

Speaker: Cesar Bernardes (UNESP - Universidade Estadual Paulista (BR))

21 Study of Collective Phenomena in Heavy-Ion Collisions Using CMS Open Data

18+2'
Event-by-event quantum fluctuations in the initial stages of ultrarelativistic nucleus–nucleus collisions have been theoretically predicted to influence observables constructed from final-state quantities, such as azimuthal two-particle momentum correlations. In several instances, these predictions have been indirectly confirmed through comparisons between experimental data and simulations that incorporate the hydrodynamic evolution of the medium formed in such collisions, known as quark-gluon plasma (QGP), composed of deconfined quarks and gluons. In this presentation, we report preliminary measurements of the observable v0​(pT), as proposed in Phys. Lett. B 857, 138985 (2024). This observable is directly sensitive to the properties of the initial state and has been suggested as a valuable probe of collective behavior in heavy-ion collisions, particularly in relation to the radial flow of the QGP. The analysis is based on PbPb collision data at 2.76 TeV, obtained from publicly available datasets provided by the CMS experiment (CMS Open Data).

Speaker: Allan Eduardo Flores Godoi Ferreira (UFRGS - Universidade Federal do Rio Grande do Sul (BR))

12:30 Lunch

QGP and Extreme Matter

22 Chiral vortical catalysis constrained by lattice QCD

18+2'
Evidences of vortical effects have been recently found by experiments in heavy ion collisions, instigating new insights into the phase diagram of quantum chromodynamics. Considering the effect of rotations, lattice QCD calculations shows that temperatures for deconfinement and chiral symmetry restoration should increase with the angular velocity, and the dominant effects are related to gluonic degrees of freedom. These findings could be essential for quark models in rotating systems that lack gluonic interactions, which predicts the decreasing of the chiral temperature transition with the angular velocity. To address this issue properly, in this work we apply the two-flavor Nambu--Jona-Lasinio model to explore the phase diagram in a rotating rigid cylinder with constant angular velocity in the mean field approximation. To circumvent the absence of gluons, we propose the application of an effective coupling dependent of the angular velocity, fitted to match the pseudocritical temperature of chiral phase transition in the model through lattice QCD data. Our results indicate that the running coupling induces the enhancement of the chiral condensate as a function of angular velocity, strengthening the breaking of chiral symmetry, an effect previously dubbed as chiral vortical catalysis. For the chiral susceptibility we observe stronger fluctuations around the transition temperature when we consider the running coupling. The phase diagram is affected by these findings shifting the critical end point (CEP) to higher temperatures and chemical potentials.

Speaker: Varese Salvador Timóteo (University of Campinas - UNICAMP)

23 Delineating the viscous properties of the rotating QCD medium formed in relativistic heavy ion collisions

18+2'
We have explored the influence of angular velocity on the shear and bulk viscosities of a rotating QCD medium. In the noncentral events of the relativistic heavy ion collisions, the resulting QCD medium acquires finite angular momentum, giving rise to a finite angular velocity. This rotational motion can notably alter various properties of the hot QCD medium, including the viscous properties. Thus, there exist phenomenological consequences of such rotation on the shear and bulk viscosities of the medium. Using the recently developed novel relaxation time approximation in the relativistic Boltzmann transport equation and incorporating the influence of finite angular velocity, we have calculated the shear and bulk viscous coefficients of the rotating QCD medium. Additionally, we have compared these viscous coefficients with their counterparts in the standard relaxation time approximation within the kinetic theory approach. Our analysis reveals that the introduction of rotation increases both shear and bulk viscosities, suggesting an enhanced momentum transfer within the medium and greater fluctuations in local pressure. This rotational impact on the shear and bulk viscosities is more conspicuous at low temperatures than at high temperatures. It is further observed that the use of the novel relaxation time approximation results in a reduction of the shear viscosity and an enhancement of the bulk viscosity as compared to the standard relaxation time approximation across the entire temperature range. Furthermore, our analysis shows that the rotation leaves a significant impact on some observables associated with the flow characteristic, fluid behavior and conformal symmetry of the medium. On the whole, our results suggest that the rotation serves as an essential component in understanding the viscous properties and collective behavior of the hot QCD medium.

Speaker: Dr Shubhalaxmi Rath (Universidad Mayor)

24 Jet-Induced Λ Polarization from Spin-Vorticity Coupling: Probing Vorticity Rings in the QGP

18+2'
We propose a novel observable of jet thermalization in high-energy nuclear collisions, based on correlating $\Lambda$ hyperon polarization with vortex dynamics. Using hybrid simulations, we show that the deposition of energy and momentum by quenched jets generates toroidal vorticity rings, a ubiquitous structure in fluid dynamics. These rings induce a corresponding toroidal pattern of $\Lambda$ polarization through spin-vorticity coupling, and the observable is explicitly designed to isolate the circular polarization component around the jet axis, measuring this geometry.

Hence, this observable provides a practical way to measure vortex formation through polarization. Because the formation of vortex rings is a uniquely hydrodynamic response, it also enables tests of the onset of collective behavior in both large and small collision systems. Moreover, since the strength of the induced polarization is sensitive to the shear viscosity ($\eta/s$) of the plasma and the kinematics of jet energy deposition, the observable can act as a probe of medium properties and jet thermalization dynamics.

To assess its experimental viability, we validate the observable using Monte Carlo simulations. Hybrid hydrodynamic events for Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 2.76~\rm TeV$ provide a scenario where $\Lambda$ polarization is generated by jet-induced vorticity, while PYTHIA pp events serve as a null baseline with no polarization by construction. In both cases, $\Lambda$ polarization is reconstructed from the anisotropic emission of protons in the weak decay $\Lambda \rightarrow \pi^- + p^+$, a direct consequence of parity-violating nature. This framework is used to confirm that the observable isolates the ring-like signal from vorticity and correctly yields a null result for the unpolarized baseline.

We then use the simulation results to estimate the number of measured events needed to resolve the signal experimentally. Using typical $\Lambda$ reconstruction efficiencies and jet production rates, we find that a $5\sigma$ discrimination between the vortex-polarized and null hypotheses is achievable with the Pb--Pb, O--O, and pp data already collected by ALICE.

With its feasibility demonstrated, this measurement is now being studied as a formal analysis proposal within the ALICE Collaboration. A successful detection of this signal would provide the first direct evidence of vortical structures from jet quenching, broadening our understanding of how energy dynamically thermalizes in the QGP and offering new insights into collectivity and spin transport.

Speaker: Cicero Domenico Muncinelli (University of Campinas UNICAMP (BR))

15:00 Coffee break

QGP and Extreme Matter

25 Extreme magnetic-field effects in heavy-ion collisions and QCD matter

23+2'

Speaker: Leticia Palhares

26 Photon production from gluon splitting and fusion induced by a magnetic field in heavy-ion collisions

23+2'
We compute the photon yield and elliptic flow coefficient in relativistic heavy-ion collisions from gluon fusion and splitting processes induced by a magnetic field. The calculation accounts for the intense magnetic field and the high gluon occupation number at early times. The photon production induced by these process represents an excess contribution over calculations without magnetic field effects. We compare this excess to the difference between PHENIX data and recent hydrodynamic calculations for the photon transverse momentum distribution and elliptic flow coefficient $v_2$. We show that the calculation helps to better describe the experimental results obtained at RHIC energies.

Speaker: Prof. Alejandro Ayala (Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico)

27 Universal Scaled Spectra: Bayesian Constraints on QGP Transport from Heavy-Ion Collisions

18+2'
We present the first comprehensive Bayesian calibration of a state-of-the-art hybrid heavy-ion collision model incorporating a novel observable: the scaled particle spectra of pions. This observable isolates the intrinsic spectral shape and reveals a remarkable degree of universality across centrality classes and collision systems. Leveraging the JETSCAPE framework, we construct Gaussian process emulators to efficiently explore the scaled spectra throughout the QGP transport parameter space.
We perform a model-to-data calibration using ALICE measurements from Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 2.76$ TeV and Xe-Xe collisions at $\sqrt{s_{\mathrm{NN}}} = 5.44$ TeV. By comparing posterior distributions, we demonstrate that this differential universal observable provides complementary constraints to traditional $p_T$-integrated observables, revealing previously hidden tensions in the parameter space. Our analysis quantifies the enhanced sensitivity of scaled spectra to specific transport properties and highlights the importance of incorporating differential information in multi-observable Bayesian frameworks.
These findings establish scaled spectra as a powerful tool for precision extraction of QGP properties and pave the way for more discriminating tests of heavy-ion collision models across different collision systems and energies.

Speaker: Thiago Siqueira Domingues

28 Discussion

17:30 Welcome Cocktails

Wednesday 12 November

Heavy Flavor

29 Flavor anomalies: the experimental landscape

23+2'

Speaker: Rafael Silva Coutinho (CBPF - Brazilian Center for Physics Research (BR))

30 Conventional heavy flavor hadron spectroscopy at LHCb

23+2'
The LHCb experiment is well suited to the spectroscopy of heavy flavor hadrons. The proton-proton collisions provided by the Large Hadron Collider produce a variety of heavy flavor states, and the excellent vertex and momentum resolution of the LHCb detector enables precision studies of hadron properties. Access to the kinematics of full decay chains allows amplitude analysis, which provides detailed information on the properties of intermediate resonances. This talk will present recent measurements in conventional heavy flavor hadron spectroscopy from LHCb, highlighting contributions to our understanding of the hadron spectrum.

Speaker: Dr Paras Naik (University of Liverpool (GB))

31 Exotic States with charm and/or strangeness

18+2'

Speaker: Alberto Martinez Torres (University of Sao Paulo)

32 Some current challenges in hadron physics

18+2'

Speaker: Prof. KANCHAN PRADEEPKUMAR KHEMCHANDANI

10:30 Coffee break

Heavy Flavor

33 Latest developments in CP violation and flavor mixing

23+2'

Speaker: Alberto Correa Dos Reis (CBPF - Centro Brasileiro de Pesquisas Físicas (BR))

34 Hadronic rescattering to solve helicity puzzle in B decays

23+2'

Speaker: Patricia Magalhaes (UNICAMP)

35 Search for the B0(s) to 4-proton decay in the LHCb experiment

18+2'
The large masses of B mesons allow them to decay into baryonic final states. The first observations and studies of such baryonic B decays were performed by the ARGUS and CLEO experiments in the 1990s.

The LHCb collaboration has measured the branching fractions of the decays $B^0$ and $B^0_s \to p \bar{p} p \bar{p}$ to be of the order of $10^{-8}$ using Run 1+2 datasets corresponding to an integrated luminosity of 9 $fb^{-1}$, with significances of 9.3σ and 4.0σ, respectively. In the charm sector, the BESII collaboration observed the kinematically allowed decay $D_{s}^+ \to p \bar{n} $ and has searched for the decay $D_s^+ \to p \bar{p} e^{+} ν_{e}$.

Baryonic B decays provide a unique opportunity to study several interesting phenomena, such as: Threshold enhancement - an effect observed in three- and four-body decay modes as an enhancement near the baryon–antibaryon invariant mass threshold; multiplicity effects - the observed hierarchy between the branching fractions of two-body and multi-body final states.

In this talk, I will summarise the Run 2 LHCb analysis of the decays $B^0$ and $B^0_s \to p \bar{p} p \bar{p}$, and share some perspectives to Run 3.

Speaker: Juan Baptista de Souza Leite (CBPF - Brazilian Center for Physics Research (BR))

36 Alternative Model for an Amplitude Analysis of the D+ to K-K+pi+ decay

18+2'
Charge-Parity Violation (CPV) is expected in 3-body charm decays such as the $D^+\rightarrow K^- K^+\pi^+$. This is an interesting channel to investigate, and an amplitude analysis is required to understand the dynamics of different contributions to the final state and the dynamical origin of CPV. The present research seeks to analyse recent data of the Large Hadron Collider beauty (LHCb) experiment at CERN, with a precise theoretical model capable of revealing CPV mechanisms. Previous analyses of the $D^+\rightarrow K^- K^+\pi^+$ decay reported by collaborations such as CLEO, BaBar and LHCb itself, were unable to satisfactorily describe the data using the Isobar Model. Currently, the LHCb has a sample of charmed meson decays with around 100 million events for the $D^+\rightarrow K^- K^+\pi^+$ decay. Therefore, this is an excellent opportunity to test more complex and realistic models that include hadronic final state interactions and capable of revealing the presence of CPV.

Speaker: Felipe Cesario Laterza Lopes (Universidade Estadual de Campinas)

12:30 Lunch

EIC

37 Probing Cold QCD: Jefferson Lab eA program today and its prospects at 20+ GeV and EIC

27+3'
The Jefferson Lab eA program, initially carried out with a 5 GeV electron beam and the CLAS detector, is now continuing with beam energies up to 11 GeV using CLAS12. Looking ahead, there are plans to extend the program to higher energies following the CEBAF upgrade to beyond 20 GeV. The aim of eA program is to investigate the underlying mechanisms of medium-induced modifications to quark propagation and hadron formation using semi-inclusive deep-inelastic scattering. These effects, quantified through the measurements of hadronic multiplicity ratios and transverse momentum broadening, require multidimensional analyses on a broad kinematical range. In this talk, I will summarize key results from the Jefferson Lab eA program conducted with 5 GeV and 11 GeV beams, and discuss future prospects for extending these studies to the upgraded 20+ GeV CEBAF and the Electron-Ion Collider (EIC).

Speaker: Taisiya Mineeva (Universidad de La Serena (CL))

38 Hadronization Dynamics in the Nuclear Medium: Preliminary Insights from the CLAS12 RGE Experiment at Jefferson Lab

27+3'
Studying hadronization - the process by which quarks and gluons transition into hadrons -is fundamental to understanding the strong interaction dynamics within quantum chromodynamics (QCD). Using the CLAS12 detector at Jefferson Lab, the Run Group E (RGE) experiment offers unprecedented insights into hadronization in the nuclear medium. This talk will present preliminary results from the experiment, focusing on the behavior of hadrons produced in 11-GeV electron-nucleus scattering. The experiment employs various nuclear targets, enabling a comparative study of medium effects on hadron formation and propagation. By analyzing observables such as hadron multiplicity ratios, transverse momentum broadening, and energy loss, we explore the interaction of quarks and hadrons with the nuclear environment. These measurements provide critical data for understanding color confinement and hadronization timescales, shedding light on QCD processes in dense media. The talk will also highlight the innovative Double-Target system developed for RGE, which facilitates rapid target switching to enhance data collection efficiency.

Speaker: Prof. Hayk Hakobyan (Universidad Técnica Federico Santa María)

Student flash talks

39 Effects of the magnetic field on the production of pseudoscalar mesons in ultra-peripheral heavy-ion collisions

Recent studies indicate that the decay width $\Gamma(\pi^0\to\gamma\gamma)$ is strongly reduced in the presence of a uniform external magnetic field. In this work, we study the effect of the magnetic field on the production of neutral pions in photon-photon interactions in ultra-peripheral heavy-ion collisions. In addition, we present the calculation of the production cross section of the $\eta_b$ meson, based on the two-photon decay width recently determined by lattice QCD calculations, which constitutes the first direct application of the lattice result. Furthermore, we estimate the production cross section of the $\eta_c$ meson in ultra-peripheral collisions using the new value of the partial decay width $\Gamma(\eta_c\to\gamma\gamma)$, measured by the BESIII Collaboration in the process $J/\psi\to\gamma\eta_c$, which turned out to be more than twice the current reported world average for this decay. Finally, in view of the growing interest of the heavy-ion community in UPCs, we take the opportunity to perform a comprehensive study of the different ways of defining ultra-peripheral collisions and of the distinct approaches to treat the equivalent photon flux.

Speaker: Celsina Azevedo (University of Sao Paulo)

40 Associated production of Psi(2S) and Phi in diffractive proton-proton collisions at the LHCb experiment

The LHCb detector, with its forward rapidity coverage, can probe kinematic regions at low Bjorken-x as low as $10^{-6}$. This unique capability, combined with excellent momentum resolution, vertex reconstruction, and particle identification, enables precision measurements at low transverse momentum and forward rapidity.
Studies of associated production of $\Psi(2S)$ and $\Phi$ in diffractive proton-proton collisions at the LHCb experiment will be discussed. At LHC energies, investigations of diffractive events provide valuable insights into QCD phenomena. These include understanding the characteristics of pomerons and exotic hadronic states, as well as examining low-x gluon distributions and the effects of saturation.

Speaker: Mr Jeferson Dos Santos Oliveira (Brazilian Center for Research in Physics (BR))

41 Charge Asymmetry in Three-Body 𝐵 ± Decays with LHCb Run 3 Data

The study of charge asymmetries in three-body 𝐵 ± → h h h decays provides a sensitive probe of CP violation in the beauty sector. Using the first data collected during LHCb Run 3, we are performing a preliminary investigation aimed at measuring these asymmetries through fits to the invariant mass distributions of selected candidates. The upgraded detector and higher instantaneous luminosity of Run 3 are expected to improve signal-to-background separation and reduce systematic uncertainties, offering enhanced sensitivity compared to previous runs. This ongoing study will lay the groundwork for precise tests of the Standard Model and potential exploration of effects beyond it.

Speaker: Jorge Julio Barreiros Venuto De Siqueira (CBPF - Brazilian Center for Physics Research (BR))

42 Signal Classification in Rare B⁰ → K*⁰(892)μ⁺μ⁻ Decays Using Machine Learning Technique

Rare decays of B mesons, such as B⁰ → K*⁰(892)μ⁺μ⁻, play a crucial role in testing the Standard Model (SM) of particle physics and probing potential signs of New Physics (NP). These flavor-changing neutral current (FCNC) processes are forbidden at tree level in the SM and occur only via higher-order loop diagrams, making them extremely sensitive to virtual contributions from beyond the SM particles.

The complexity and rarity of these events pose significant challenges in terms of signal identification and background suppression. In this context, Machine Learning (ML) techniques have emerged as powerful tools for enhancing the precision and efficiency of signal classification in high energy physics experiments.

This work aims to develop and evaluate machine learning models capable of distinguishing signal events of the rare decay B⁰ → K*⁰(892)μ⁺μ⁻ from various background processes using simulated and real experimental data.

Speaker: Mr Thiago De Andrade Rangel Monteiro (Rio de Janeiro State University - (UERJ))

43 Photoproduction of a Y-shaped Proton

In high-energy physics, understanding and describing interactions involving protons is essential. One of the first steps needed is to correctly model the proton. Assuming minimization of the momentum flux within the proton, the Y-shaped proton is the natural choice. Since the investigations focus on particle collisions and considering that charges in ultrarelativistic motion produce a photonic field, we worked on modeling the photoproduction of a Y-shaped proton focusing on latter use on a better description of the ultraperipheral collisions (UPCs) and investigated the impact of the charge distribution on the photon flux for this shape of proton.

Speaker: Brunno Mota

44 Fractal Rectification of Yang-Mills Theory

In this work, we analyze the scaling properties of Yang-Mills field theory that manifest as self-similarity of n-point functions truncated by the scale evolution. In certain approaches, fractal structures are used in Yang-Mills theories to circumvent computational difficulties, allowing the determination of an analytical expression for the coupling constant, which agrees with the results obtained in several experimental findings, making it possible to explain many phenomena observed in high-energy collisions. In this work, we approach the study of fractal structures through field theory using the perturbative expansions of the propagators and vertices, making an application to Quantum Electrodynamics and Quantum Chromodynamics, where we obtain the $q$-exponential in the renormalization factors of the elements of the theory, and thus evidencing the connection with Tsallis statistics and fractal structures.

Speaker: Mr Jhon Mario Cordoba Pareja (São Paulo University)

45 Projections for CEP of W pairs in the HL-LHC with the PPS2 detector of the CMS experiment

This work consists of a projection study on the efficiency of the PPS detector in the high-luminosity regime through the CEP process $pp\rightarrow p(W^{+}W^{-})p$ with hadronic decay in both W bosons. Simulated samples containing: signal for SM, anomalous coupling $a_0^W = 2\times 10^{-7}$, anomalous coupling $a_C^W = 2\times 10^{-5}$, and with the QCD background for $pp\rightarrow 4J$, were subjected to a selection process where the kinematics equations of CEP processes were applied. The W bosons reconstruction counted on the ordering of jet pairs based on their mass proximity to the one of the W boson. The hadronic decay of both W bosons, requiring the presence of 4 jets in each event, proved to be a major limitation in searching for signal. The projected significance is presented for both anomalous couplings and SM signal, which is expected to be improved with optimized kinematic cuts, like acoplanarity on W bosons and their respective dijets decays. Improvements will be used to establish new exclusion limits for the aQGC couplings $a_0^W$ and $a_C^W$.

Speaker: Omar Silveira (Universidade Federal do Rio Grande do Sul (UFRGS))

46 Characterization and Simulation of Hybrid UFSD/LGAD Sensors for high-precision timing measurements with the Precision Proton Spectrometer in the CMS Experiment

The High-Luminosity LHC (HL-LHC) presents challenges due to up to $200$ simultaneous interactions per beam crossing, where around $10\sim15\%$ of the reconstructed vertices are composed of multiple interactions time-separated by about $\sim150~\text{ps}$, which degrades the performance and the accuracy of the event reconstruction. To mitigate this, it is required to employ more precise timing information. The present work has the objective of simulation, characterization, and calibration of hybrid Ultra-Fast Silicon Detectors (UFSD) based on Low-Gain Avalanche Diode (LGAD) sensors, aiming at a timing resolution with uncertainty of $~\sim10~\text{ps}$. The methodology is divided into two specific objectives: (1) the computational simulation of the sensor's response with Allpix Squared (AP$^{2}$), COMSOL, and Garfield++, utilizing the ROOT Framework for Data Analysis and Geant4 for graphical visualization; (2) and the experimental characterization that is performed using pulsed lasers and radioactive sources, to study the sensor's response to traversing particles.

Speaker: Mrs Valeria Vale (CBPF - Brazilian Center for Physics Research (BR))

47 Hunting for axion-like particles with top quarks at the high-energy frontier

The unprecedented proton-proton collision energy and the large data volumes reached by the LHC and the CMS detector with supreme particle detection capabilities provide a unique setting for discovering the particle constituting the dark matter. Since the beginning of the LHC, there were various DM searches within the CMS experiment. With this analysis, we embark on a novel search for axion-like dark matter particles in proton-proton collisions at the LHC. The hypothetical axion particle was first proposed to address the famous strong-CP problem in Quantum Chromodynamics (QCD). Since then, such pseudo-scalar particles, dubbed axion-like-particles (ALPs), have been incorporated in various well motivated theoretical models that extend the SM, and have been sought for in vastly different experiments. The mass of ALPs and their interaction strength with the SM particles are generally free parameters, and depending on the model ALPs can either constitute a viable candidate for DM or a portal to a more extended dark sector. The CMS and ATLAS experiments have searched for ALPs using Run 2 data, however these searches target ALP production via Higgs boson or other scalar particles and only decay to two collimated photons are considered. This work aims to add a complementary phase-space to these searches with a completely new production and decay channel that was experimentally never explored. Our goal is the search for the production of axion-like particles from proton-proton collisions at √s = 13.6 TeV at the CERN LHC, using the data collected by the CMS detector. There are two main study fronts: exotic top quark decays and single top + ALP production. Both research directions represent a t+a signature (where a stands for ALP) that is amenable to a search in the collisions produced by the LHC. In summary, we propose to use LHC Run 3 data to search for axion-like particles as a viable DM candidate in production and decay that was never explored before experimentally. The success of this effort relies on innovative analysis techniques to tackle the triggering, signal reconstruction, and estimation of background processes.

Speaker: Marcio De Sousa Mateus Junior (SPRACE - UNESP)

16:30 Posters and Refreshments

Thursday 13 November

Soft QCD and Diffraction

48 Soft and semi-hard components of multiplicity distributions in the k_T factorization approach

18+2'
The multiplicity distribution (MD) of charged particles in high-energy proton-proton collisions remains an intricate aspect of quantum chromodynamics (QCD). Traditional models, such as the Negative Binomial Distribution (NBD), successfully described MDs at lower energies, but fail at higher energies, such as those probed by the Large Hadron Collider (LHC), where a "shoulder-like" structure emerges.

To address this, we employ the Double Negative Binomial Distribution (DNBD), a weighted combination of two NBDs representing contributions from soft and semi-hard processes. This model typically involves six free parameters, but by incorporating the $k_T$-factorization formalism and introducing an energy scale $\Lambda$, we effectively reduce the number of free parameters from six to four while maintaining a strong fit to high-energy MD data. The unintegrated gluon distribution used in this work is derived from the Golec-Biernat--Wüsthoff (GBW) model.

In addition, we explore different values of the energy scale $\Lambda$ and perform a parallel analysis using the Kharzeev-Levin-Nardi (KLN) gluon distribution model. We also investigate KNO scaling and use the $k_T$-factorization formalism to describe the pseudo-rapidity distribution.

Our approach demonstrates excellent agreement with recent experimental data, yielding low $\chi^2$ values and highlighting the potential for further improvements using more realistic gluon distribution models. This analysis provides valuable insights into the interplay of soft and semi-hard processes in high-energy collisions.

Speaker: Henrique Rodrigues Martins Fontes (Instituto de Física da USP)

49 Particle production in semi/exclusive collisions and collectivity probes at the LHC

23+2'
After confirmation of production of exclusive events with intact protons and ions at the LHC such as light by light scattering or dilepton exclusive production, there is increased interest to probe for photo or pomeron induced production of mesons and di-quark pair systems such as top antitop pairs. The talk describes key signatures for ttbar production with a single intact proton via photon + gluon or pomeron + gluon initiated processes. The systematic effect from pomeron structure and photon fluxes functions is discussed. Neural network based results to distinguish these two semiexclusive productions from main central background are also discussed. Additionally a phenomenological and experimental update on collectivity probes at the LHC is included.

Speaker: Dr Javier Alberto Murillo Quijada (Universidad de Sonora (MX))

50 Diffractive processes in pPb collisions and intrajet collectivity probes at the LHC

18+2'
Diffractive processes in proton–lead (pPb) collisions provide a window into the nonperturbative regime of QCD, where color singlet exchanges and gluon saturation phenomena may play a key role. Recent observations of collective-like effects within jets suggest that signatures of collectivity, traditionally associated with heavy-ion collisions, may also emerge in small systems. In this talk, we present studies of diffractive pPb collisions and intrajet correlations, exploring how soft-QCD effects and model variations impact the extraction of charged-particle multiplicities, rapidity gaps, and azimuthal anisotropies.

Speaker: Jesus Alberto Velazquez Corral (The University of Kansas (US))

51 Review of diffractive results at the LHC

23+2'

Speaker: Antonio Vilela Pereira (CBPF - Brazilian Center for Research in Physics (BR))

10:30 Coffee break

Soft QCD and Diffraction

52 TOTEM results

27+3'

Speaker: Frigyes Janos Nemes (CERN (also at Wigner RCP Budapest, Hungary))

53 Overview of ATLAS forward proton detectors: status, performance and new physics results

27+3'
A key focus of the physics program at the LHC is the study of head-on proton-proton collisions. However, an important class of physics can be studied for cases where the protons narrowly miss one another and remain intact. In such cases, the electromagnetic fields surrounding the protons can interact producing high-energy photon-photon collisions. Alternatively, interactions mediated by the strong force can also result in intact forward scattered protons, providing probes of quantum chromodynamics (QCD). In order to aid identification and provide unique information about these rare interactions, instrumentation to detect and measure protons scattered through very small angles is installed in the beam pipe far downstream of the interaction point.
We describe the ATLAS Forward Proton AFP Detectors, including their performance to date, covering Tracking and Time-of-Flight Detectors as well as the associated electronics, trigger, readout, detector control and data quality monitoring. Finally, a glimpse on the newest results will be given.

Speaker: Janusz Chwastowski (Polish Academy of Sciences (PL))

12:00 Lunch

BSM and photon-photon

54 Review of photon-photon physics at the LHC

23+2'

Speaker: Christophe Royon (The University of Kansas (US))

55 CMS Precision Proton Spectrometer performance and HL-LHC plans

18+2'

Speaker: Clemencia Mora Herrera (CBPF - Brazilian Center for Physics Research (BR))

56 Measuring photon-induced tau-lepton pair production with ATLAS

18+2'

Speaker: Lydia Audrey Beresford (Deutsches Elektronen-Synchrotron (DE))

57 Physics results with the CMS Precision Proton Spectrometer and projections for the HL-LHC with PPS2

23+2'
This talk will present the recent results from various analyses on signals containing intact protons measured by the CMS Precision Proton Spectrometer (PPS), which includes searches for New Physics in the electroweak sector. As the operation of the HL-LHC will require more stringent selection of intact protons due to the higher pileup, the PPS2 project will be presented and projections for potential physics analyses with the upcoming data from Phase-II will be discussed.

Speaker: Gustavo Gil Da Silveira (Universidade do Estado do Rio de Janeiro (BR))

15:30 Coffee break

BSM and photon-photon

58 New covariant methods for higher loop corrections in effective field theories

23+2'

Speaker: Gero von Gersdorff

59 Looking for Baryon Number Violation with HIBEAM/NNBAR Experiment

23+2'
The baryon number violation is an essential ingredient for the preferential creation of matter over antimatter needed to account for the observed baryon asymmetry in the Universe. However, a process that violates baryon number has yet to be experimentally observed. The HIBEAM/NNBAR program is a proposed two-stage experiment at the European Spallation Source (ESS) to search for baryon number violation. The program will include high-sensitivity searches for processes that violate baryon number by one or two units: free neutron–antineutron oscillation, neutron–antineutron oscillation via regeneration from a sterile neutron state, and neutron disappearance. The search for free neutrons converting to antineutrons will have a sensitivity improvement of three orders of magnitude compared to the last searches. We will present the recent progress on the experiment, including design studies for the annihilation detector, particle identification and background rejection.

Speaker: Andre Asevedo Nepomuceno (Universidade Federal Fluminense)

60 Discussion

Closing of the Workshp & Welcome to the Symposium

19:30 Workshop Dinner – Rest. Terra Brasilis

Friday 14 November

CLAF Symposium – Opportunities for Latin-American Cooperation in High-Energy Physics with CERN

CLAF Symposium announcement

18:00 Symposium – Cocktails