In this poster, we present a study of the rejection of jets containing more than one b-hadron in the ATLAS “online" b-taggers, aiming to significantly reduce the readout rates of the ATLAS b-jet trigger system. It is important to be able to efficiently select events containing b-jets at the trigger level for analyses that involve many b-quarks in the final states, such as the search for HH->4b...
The statistical combination of LHC results enables a greater understanding of what the observed data tell us about physics Beyond the Standard Model (BSM). In practice, it would allow us to derive stronger limits on BSM theories, to search for dispersed signals, as well as performing more comprehensive probes for deviations from the Standard Model. However, the combination of LHC analyses...
The ATLAS Forward Proton Time-of-Flight detector: use and projected performance for LHC Run 3 The Time-of-Flight (ToF) detectors of the ATLAS Forward Proton (AFP) system are designed to measure the primary vertex z-position of the pp -> pXp processes by comparing the arrival times measured in the ToF of the two intact protons in the final state. We present the results obtained from a...
In Supersymmetry, Staus are the proposed super-partner of Standard Model Tau particles and have previously been searched for by the ATLAS and CMS collaborations, so far with no evidence for their existence. However, previous Stau searches in ATLAS have only been able to obtain sensitivity as low as 100 GeV due to the challenging Standard Model backgrounds, resulting in a gap between the ATLAS...
In the high-luminosity era of the Large Hadron Collider, the instantaneous luminosity is expected to reach unprecedented values, resulting in up to 200 proton-proton interactions in a typical bunch crossing. To cope with the resulting increase in occupancy, bandwidth and radiation damage, the ATLAS Inner Detector will be replaced by an all-silicon system, the Inner Tracker (ITk). The innermost...
The Liquid Argon Calorimeters are employed by ATLAS for all electromagnetic calorimetry in the pseudo-rapidity region |η| < 3.2, and for hadronic and forward calorimetry in the region from |η| = 1.5 to |η| = 4.9. They also provide inputs to the first level of the ATLAS trigger. After successful period of data taking during the LHC Run-2 between 2015 and 2018 the ATLAS detector entered into the...
A new era of hadron collisions will start around 2029 with the High-Luminosity LHC which will allow to collect ten times more data than what has been collected during 10 years of operation at LHC. This will be achieved by higher instantaneous luminosity at the price of higher number of collisions per bunch crossing.
In order to withstand the high expected radiation doses and the harsher...
The ATLAS experiment at CERN is constructing upgraded system
for the "High Luminosity LHC", with collisions due to start in
2029. In order to deliver an order of magnitude more data than
previous LHC runs, 14 TeV protons will collide with an instantaneous
luminosity of up to 7.5 x 10e34 cm^-2s^-1, resulting in much higher pileup and data rates than the current experiment was designed to...
Precision observables are well known for constraining most of the Beyond Standard Model (BSM) scenarios tightly. We present here a simple and comprehensive fitting framework for various BSM scenarios to these observables. We start with the fit of S, T and V parameter and their correlations using the Electroweak Precision Observables (EWPO) including the recent $m_W$ measurement from CDF-II....
The inner detector of the present ATLAS experiment has been designed and developed to function in the environment of the present Large Hadron Collider (LHC). For the next LHC upgrade to High Luminosity, the particle densities and radiation levels will exceed the current levels by a factor of ten. The instantaneous luminosity is expected to reach unprecedented values, resulting in up to 200...
In the Standard Model (SM) there are no symmetries that would forbid lepton flavor violating (LFV) processes, which have been observed for the first time in the form of neutrino oscillations. However, to date no evidence for this kind of decays was found in the charged lepton sector. Although in principle possible, charged LFV (CLFV) decays, such as the tau->3muons decay, are expected to have,...
FASER-2 is a potential upgrade to the FASER experiment, and could be hosted in the proposed Forward Physics Facility (FPF) 620m to the west of the ATLAS interaction point, in the far-forward region of the LHC collisions. The experiment would have sensitivity for long-lived particles (LLPs) produced by rare meson decays that could be potential candidates for light dark matter. The proposed...
Electromagnetic interaction of colliding beams leads to perturbations in their motion as a whole (coherent effect resulting in orbit shift) as well as to the motion of individual particles (incoherent effect resulting in particles re-distribution. In colliders the effect influences its luminosity in two ways. First, the number of collisions is changed in comparison to expected values; second,...
The ATLAS Collaboration provides a range of outreach and engagement opportunities appropriate for classroom engagement with particle physics developed by the ATLAS Collaboration. Here we present details of the exhibits/features and use of the new ATLAS Visitors Centre at CERN – the most visited external visitor site at CERN – as well as an overview of the highly-successful Virtual Visit...
Festivals, conferences and other public events provide scientists and science communicators with an opportunity to reach new audiences. To do this successfully ATLAS collaboration members have come up with attractive material and programmes targeting these audiences. Science tents have been set up at music, art and dance festivals, such as WOMAD in the U.K. and the Colours of Ostrava in the...
The ATLAS Open Data project has for many years successfully delivered open-access data, simulations, documentation and related resources for education and outreach use in High Energy Physics and related computer sciences based on data collected in proton–proton collisions at 8 TeV and 13 TeV. These resources have found substantial application worldwide in Universities, in Schools, and in other...
Engaging children under the age of 12 in physics research is particularly challenging but offers unique educational potential. Outreach and engagement at an early age has been demonstrated to be key to increasing awareness of physics and to increasing diversity in the field in later years. We present a variety of activities and resources developed by the ATLAS Collaboration targeting this...
Event-by-event fluctuations of mean transverse momentum, $\langle p_{\rm{T}}\rangle$, help to characterize the properties of the bulk of the system created in ultrarelativsitic heavy-ion collisions, called the quark-gluon plasma (QGP). The fluctuations are closely related to the dynamics of the phase transition from the QGP to a hadron gas.
In this contribution, event-by-event fluctuations...
The ATLAS Collaboration consists of more than 5000 members, from over 100 different countries. Regional, age and gender demographics of the collaboration are presented, including the time evolution over the lifetime of the experiment. In particular, the relative fraction of women is discussed, including their share of contributions, recognition and positions of responsibility, including...
The t-channel single top quark production is measured in proton-proton collisions at a center of mass energy of 5 TeV with 257 pb^{-1} of data collected with the ATLAS detector. The measurement uses a Boosted Decision Tree (BDT) trained on Monte Carlo to separate signal from background. The output distribution of the BDT is used in a profile-likelihood fit to data. The analysis also measures...
Identification of multi-pronged jets plays a fundamental role at the LHC and other colliders, especially in the forthcoming years when the energy frontier will reach unexplored regions. Within multivariate tools, the strategy of MUST (Mass Unspecific Supervised Tagging) has proven to be successful for implementing generic jet taggers capable of discriminating signals over a wide range of jet...
In the Standard Model the mass of the Higgs boson (m(H)) is a fundamental constant that is not predicted by any theory. Therefore, it must be measured experimentally. Many properties of the Higgs boson depend on m(H), such as its production cross sections, the branching ratios, and more generally its couplings. We present the latest measurement of the Higgs boson mass using H->ZZ decays in the...
This work focuses on the influence of the nonextensivity on the transport properties related to charge and heat in a magnetized hot QCD medium. We have determined the electrical conductivity, Hall conductivity, thermal conductivity and Hall-type thermal conductivity using the nonextensive Tsallis framework within the kinetic theory approach. The deviation of the nonextensive parameter $q$ from...
Cathode Strip Chambers (CSC) provide precise measurements of muon track coordinates in the CMS endcap region. CSC uses 40%Ar+50%CO2+10%CF4 as a working gas mixture, where the CF4 component provides reliable protection against anode wire aging sufficient for CSC operation during the HL-LHC period. However, CF4 has a Global Warming Potential (GWP) of 6630 over 100 years, so the CMS CSC community...
ATLAS has measured the total cross section during the LHC Run-1 at sqrt(s) = 7 and 8 TeV and in Run-2 at sqrt(s)=13 TeV using a luminosity dependent approach which exploits the relation ensured by the Optical Theorem between sigma_tot and the imaginary part of the scattering amplitude in the forward direction. To reach values of the Mandelstam variable -t down to 2.5 x 10^-4 GeV^2 needed to...
The LUXE experiment (Laser Und XFEL Experiment) is an experiment in planning at DESY Hamburg using the electron beam of the European XFEL. LUXE is intended to study collisions between a high-intensity optical laser pulse and 16.5 GeV electrons from the XFEL electron beam, as well as collisions between the laser pulse and high-energy secondary photons. This will elucidate quantum...
The elastic scattering of protons at 13 TeV is measured in the range of protons transverse momenta allowing access to the Coulomb-Nuclear-Interference region. The data were collected thanks to dedicated special LHC beta* = 2.5 km optics. The total cross-section and rho-parameter, the ratio of the real to imaginary part of the forward elastic scattering amplitude, are measured and compared to...
This poster will present the measurement of the fiducial and differential cross sections of the electroweak production of a Zy pair in association with two jets. The analysis uses 140.1 /fb of LHC proton-proton collision data taken at sqrt(s)=13 TeV recorded by the ATLAS experiment during the years 2015-2018. Events with a Z boson candidate decaying into either an e+e- or mu+mu- pair, a photon...
In 2017, the ATLAS collaboration measured the W-boson mass using pp-collision data taken in 2011 at sqrt(s) = 7 TeV, resulting in a precision of 19 MeV. We present a revised analysis of the same dataset, improving the fit methods and including a measurement of the width of the W-boson. A precise measurement of these quantities in the decay of the W-boson represent an excellent precision test...
Using 13 TeV pp collision data collected during Run-2 of the LHC, new decays of beauty baryons are searched for.
The International Particle Physics Outreach Group (IPPOG) is a network of scientists, science educators and communication specialists working across the globe in informal science education and public engagement. IPPOG members activities include the International Particle Physics Masterclasses programme, the International Muon Week and International Cosmic Day organisation, as well as a wide...
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...
The increase of the particle flux (pile-up) at the HL-LHC with instantaneous luminosities up to $L ≃ 7.5 \times 10^{34}$ cm$^{−2}$s$^{−1}$ will have a severe impact on the ATLAS detector reconstruction and trigger performance. The end-cap and forward region where the liquid Argon calorimeter has coarser granularity and the inner tracker has poorer momentum resolution will be particularly...
The Tile Calorimeter (TileCal) is a sampling hadronic calorimeter covering the central region of the ATLAS experiment, with steel as absorber and plastic scintillators as active medium. The scintillators are read-out by the wavelength shifting fibres coupled to the photomultiplier tubes (PMTs). The analogue signals from the PMTs are amplified, shaped, digitized by sampling the signal every 25...
The results are presented for the gamma and neutron irradiation tests for SFP+ transceivers. The radiation tolerance of the electronics components used in the detector area is a key of the electronics systems at the LHC experiments. For example, the total ionising dose and the 1-MeV neutron equivalent flux estimated for the frontend electronics of the thin gap chamber of the ATLAS experiment...
The Higgs boson's discovery has opened up a plethora of possibilities. Exploring these possibilities requires precise theoretical predictions within the SM and beyond (BSM) in conjunction with revolutionary experimental progress. First, I will discuss the current work state in the study of pseudoscalar Higgs boson production, followed by the computation of radiative corrections to...
Multiplicity distributions at different collision energies collapse to a single distribution using a simple scaling. This phenomenon, known as the Koba–Nielsen–Olesen (KNO) scaling, however, breaks down at higher collision energies. We studied the multiplicity distributions of events with hard jets and show that the charged-hadron multiplicity distributions scale with jet momentum. This...
A search for new physics in top quark production with additional final-state leptons is performed with 138 fb^(-1) of proton-proton collisions at sqrt(s) = 13 TeV, collected by the CMS detector during 2016, 2017, and 2018. The search is performanced within the context of an effective field theory (EFT) framework, which parametrizes potential new physics effects in terms of 26 dimension-six EFT...
The ATLAS experiment in the LHC Run 3 is recording up to 3 kHz of fully-built physics collision events out of an LHC bunch crossing rate of up to 40 MHz, with additional rate dedicated to partial readout. A two-level trigger system selects events of interest to to cover a wide variety of physics while rejecting a high rate of background events.
The selection of events targets both generic...
The innermost tracking system of the CMS experiment consists of two tracking devices, the Silicon Pixel and Silicon Strip detectors. The tracker was specifically designed to very accurately determine the trajectory of charged particles or tracks.
In this poster, the preliminary performance of the tracker detectors during the Run 3 operation will be summarized, with particular emphasis on...
The new ALICE Fast Interaction Trigger in LHC Run 3
On the 5th of July 2022, the Large Hadron Collider (LHC) at CERN, Geneva, started the official data taking of the current LHC run, Run 3, after a maintenance, upgrade, and commissioning period of around three and a half years. ALICE (A Large Ion Collider Experiment) has undergone many upgrades and improvements [1], one of which is...
Recent experimental results, coming from ALICE and CMS, show a low-pT enhancement of charm baryon production over model predictions, which are based on e+e- collisions. This new development challenges the assumption that the fragmentation function is universal, i.e. independent of the collision system [1,2]. Several scenarios have been proposed to explain the discrepancy between the...
Four top quark production has been on the horizon since the end of LHC Run 2. Over the past few years, the process has been in the spotlight due to the continuously improving sensitivity of the LHC experiments and its rich phenomenology. The latest result of the CMS Collaboration on four top quark production in the same-sign dilepton and multilepton final states is presented. This new result...
Hadronic resonances are effective tools for studying the hadronic phase in ultrarelativistic heavy-ion collisions. In fact, their lifetime is comparable to that of the hadronic phase, and resonances are sensitive to effects such as rescattering and regeneration processes, which affect the resonance yields and shape of the transverse momentum spectra. These processes can be studied considering...
In preparation for the High-Luminosity era of the LHC, the CMS experiment will replace the existing calorimeter endcaps with a novel device - the High Granularity Calorimeter (HGCAL). The device will have around six million readout channels. Given the scale of the endcap upgrade project, the electronics system is highly specialised and has significant complexity involving multiple layers of...
