publications
list of publications with significant contributions in reversed chronological order.
2025
- preprintPhysics with high-luminosity proton-nucleus collisions at the LHCD. d’Enterria, and othersApr 2025
The physics case for the operation of high-luminosity proton-nucleus (pA) collision during Run 3 and 4 at the LHC is reviewed. The collection of O(1-10 pb-1) of proton-lead (pPb) collisions at the LHC will provide unique physics opportunities in a broad range of topics including proton and nuclear parton distribution functions (PDFs and nPDFs), generalised parton distributions (GPDs), transverse momentum dependent PDFs (TMDs), low-x QCD and parton saturation, hadron spectroscopy, baseline studies for quark-gluon plasma and parton collectivity, double and triple parton scatterings (DPS/TPS), photon-photon collisions, and physics beyond the Standard Model (BSM); which are not otherwise as clearly accessible by exploiting data from any other colliding system at the LHC. This report summarises the accelerator aspects of high-luminosity pA operation at the LHC, as well as each of the physics topics outlined above, including the relevant experimental measurements that motivate – much – larger pA datasets.
- preprintMeasurement of isolated prompt photon production in pp and p-Pb collisions at the LHCShreyasi Acharya, and othersFeb 2025
- Public NoteAssessing the mental health state of LHC scientistsFlorian Jonas, Luca Quaglia, Carolina Anna Reetz, and 4 more authorsFeb 2025ALICE-PUBLIC-2025-001, CMS NOTE-2025-001
A series of mental health awareness trainings have been initiated by the Early Career Scientists Fora (ECSF) to support and inform the LHC community. Building on a series of workshops, held online and in person at CERN between 2021 and 2023, a survey was shared with all four major experiments to assess the mental health perceptions and needs of participants. In this note the main survey findings are presented, with specific attention to the role work culture, career uncertainty, and support networks play in this scientific community. We hope this work raises awareness around the experience of mental health in a large international scientific collaboration and offers evidence that can foster deeper understanding and broaden the scope for impactful interventions.
2024
- preprintMeasurement of \(ω\)meson production in pp collisions at \(\sqrt{s}=\) 13 TeVShreyasi Acharya, and othersNov 2024
- preprintMeasurement of the inclusive isolated-photon production cross section in pp and Pb-Pb collisions at \(\sqrt{s}=\) 5.02 TeVShreyasi Acharya, and othersSep 2024
- TDRTechnical Design Report of the ALICE Forward Calorimeter (FoCal)ALICE collaborationFeb 2024CERN-LHCC-2024-004, ALICE-TDR-022
This report presents the technical design of the ALICE Forward Calorimeter (FoCal). FoCal is an upgrade of the ALICE experiment at the LHC, to be installed during Long Shutdown 3 for data-taking in the period 2029-2032. FoCal consists of a highly granular Si+W electromagnetic calorimeter combined with a Cu+scintillating-fiber hadronic calorimeter, covering pseudo-rapidity 3.2 < η < 5.8.FoCal has unique capabilities to measure direct photon production at forward rapidity, which probes the gluon distribution in protons and nuclei at small-x, and is theoretically calculable at high precision. FoCal will carry out inclusive and correlation measurements of photons, neutral mesons, and jets in hadronic pp and p-Pb collisions, as well as J/ψ production in ultra-peripheral p-Pb and Pb-Pb collisions. FoCal extends significantly the scope of the ALICE physics program to explore the dynamics of hadronic matter and the nature of QCD evolution at small x, down to x 10-6.
2023
- preprintPerformance of the electromagnetic and hadronic prototype segments of the ALICE Forward CalorimeterM. Aehle, J. Alme, C. Arata, and 72 more authorsNov 2023
We present the performance of a full-length prototype of the ALICE Forward Calorimeter (FoCal). The detector is composed of a silicon-tungsten electromagnetic sampling calorimeter with longitudinal and transverse segmentation (FoCal-E) of about 20X_0 and a hadronic copper-scintillating-fiber calorimeter (FoCal-H) of about 5}lambda_{}rm int}. The data were taken between 2021 and 2023 at the CERN PS and SPS beam lines with hadron (electron) beams up to energies of 350 (300) GeV. Regarding FoCal-E, we report a comprehensive analysis of its response to minimum ionizing particles across all pad layers. The longitudinal shower profile of electromagnetic showers is measured with a layer-wise segmentation of 1X_0. As a projection to the performance of the final detector in electromagnetic showers, we demonstrate linearity in the full energy range, and show that the energy resolution fulfills the requirements for the physics needs. Additionally, the performance to separate two-showers events was studied by quantifying the transverse shower width. Regarding FoCal-H, we report a detailed analysis of the response to hadron beams between 60 and 350 GeV. The results are compared to simulations obtained with a Geant4 model of the test beam setup, which in particular for FoCal-E are in good agreement with the data. The energy resolution of FoCal-E was found to be lower than 3% at energies larger than 100 GeV. The response of FoCal-H to hadron beams was found to be linear, albeit with a significant intercept that is about factor 2 larger than in simulations. Its resolution, which is non-Gaussian and generally larger than in simulations, was quantified using the FWHM, and decreases from about 16% at 100 GeV to about 11% at 350 GeV. The discrepancy to simulations, which is particularly evident at low hadron energies, needs to be further investigated.
- Public NotePhysics performance of the ALICE Forward Calorimeter upgradeALICE collaborationSep 2023ALICE-PUBLIC-2023-004
- thesisProbing the initial state of heavy-ion collisions with isolated prompt photonsFlorian JonasAug 2023Phd thesis, defended 11 Aug 2023
Prompt photons are an exciting and robust probe for the initial state of nuclear collisions, in particular the momentum distribution of gluons bound inside the colliding proton. Measurements of prompt photon production in p-Pb collisions can offer insights into cold nuclear matter effects such as gluon shadowing, as well as non-linear QCD effects such as gluon saturation when measured at forward rapidities. They offer these insights in a robust way, mostly unaffected by final state effects such as fragmentation or interactions with a hot or cold medium. This thesis presents the measurement of the isolated prompt photon production cross section in pp and p-Pb collisions at sqrt(s)= 8 TeV and 8.16 TeV, respectively. The measurement is performed using data recorded by the ALICE experiment, where in particular the EMCal is used to measure photons with pseudorapidities of ∣η∣< 0.7. The production cross section is measured in both collision systems for 12 GeV/c ≤ pT ≤ 80 GeV/c and confronted with pQCD calculations at NLO using the JetPhox program. Good agreement between the theoretical calculations and experimental data is observed in both collision systems within the theoretical and experimental uncertainties, showcasing the ability of NLO calculations to adequately describe the experimental data in the inspected phasespace. In order to quantify possible modifications of the partonic substructure in nuclear environments, e.g. due to the presence of the gluon shadowing, the so-called nuclear modification factor RpA is constructed. While the data is found to be in agreement with unity for the whole covered transverse momentum within the experimental uncertainties, a hint of a suppression is observed for photons with pT≲20 GeV/c. This is the first time the isolated prompt photon RpA is presented for transverse momenta below 25 GeV/c – extending the low momentum reach of a previous measurement by the ATLAS collaboration in the same collision system by a factor of two. The measurement is in good agreement with the theoretical predictions, which also indicate an increasing suppression of the prompt photon production for pT≲20 GeV/c that is commonly attributed to gluon shadowing. Finally, detailed simulation studies for a future Forward Calorimeter (FoCal) are presented, which showcase the capabilities of the FoCal detector to perform isolated prompt photon measurements down to unprecedented low Bjorken-x of x 10-6.
- JINSTPerformance of the ALICE Electromagnetic CalorimeterS. Acharya, D. Adamová, A. Adler, and 1092 more authorsJINST, Aug 2023
The performance of the electromagnetic calorimeter of the ALICE experiment during operation in 2010-2018 at the Large Hadron Collider is presented. After a short introduction into the design, readout, and trigger capabilities of the detector, the procedures for data taking, reconstruction, and validation are explained. The methods used for the calibration and various derived corrections are presented in detail. Subsequently, the capabilities of the calorimeter to reconstruct and measure photons, light mesons, electrons and jets are discussed. The performance of the calorimeter is illustrated mainly with data obtained with test beams at the Proton Synchrotron and Super Proton Synchrotron or in proton-proton collisions at }sqrt{s}=13 TeV, and compared to simulations.
- Public NotePhysics of the ALICE Forward Calorimeter upgradeALICE collaborationMay 2023ALICE-PUBLIC-2023-001
The ALICE Collaboration proposes to instrument the existing ALICE detector with a forward calorimeter system (FoCal), planned to take data during LHC Run 4 (2029-2032). The FoCal detector is a highly-granular Si+W electromagnetic calorimeter combined with a conventional sampling hadronic calorimeter, covering the pseudorapidity interval of 3.4<}eta<5.8. The FoCal design is optimized to measure isolated photons at most forward rapidity for p_{}rm T}}gtrsim4 GeV/c. In this note we discuss the scientific potential of FoCal, which will enable broad exploration of gluon dynamics and non-linear QCD evolution at the smallest values of Bjorken x accessible at any current or near-future facility world-wide. FoCal will measure theoretically well-motivated observables in pp and p-Pb collisions which are sensitive to the gluon distribution at small x at low to moderate Q^2, based on isolated photon, neutral meson, and jet production and correlations in hadronic collisions, and the measurement of vector meson photoproduction in ultra-peripheral collisions. These FoCal measurements will provide incisive tests of the universality of linear and non-linear QCD evolution in different collision systems over an unprecedented kinematic range, in particular when combined with the comprehensive experimental program at the EIC and other forward measurements at RHIC and the LHC. FoCal will also carry out measurements at very forward rapidity in Pb-Pb collisions, enabling novel probes of the Quark-Gluon Plasma based on jet quenching phenomena and long-range correlations of neutral pions, jets, and photons.
2021
- Phys. Rev. CCentrality dependence of electroweak boson production in PbPb collisions at the LHCFlorian Jonas, and Constantin LoizidesPhys. Rev. C, Oct 2021
Recent data on the nuclear modification of W and Z boson production measured by the ATLAS collaboration in PbPb collisions at \(}sqrt{s_{}rm nn}}=5.02\)TeV show an enhancement in peripheral collisions, seemingly contradicting predictions of the Glauber model. The data were previously explained by arguing that the nucleon-nucleon cross section may be shadowed in nucleus-nucleus collisions, and hence suppressed compared to the proton-proton cross section at the same collision energy. This interpretation has quite significant consequences for the understanding of heavy-ion data, in particular in the context of the Glauber model. Instead, we provide an alternative explanation of the data by assuming that there is a mild bias present in the centrality determination of the measurement; on the size of the related systematic uncertainty. Using this assumption, we show that the data is in agreement with theoretical calculations using nuclear parton distribution functions. Finally, we speculate that the centrality dependence of the W^-/W^{+} ratio may point to the relevance of a larger skin thickness of the Pb nucleus, which, if present, would result in a few percent larger PbPb cross section than currently accounted for in the Glauber model and may hence be the root of the centrality bias.
2020
- ReportLetter of Intent: A Forward Calorimeter (FoCal) in the ALICE experimentALICE CollaborationJun 2020Number: CERN-LHCC-2020-009
We propose a forward electromagnetic and hadronic calorimeter (FoCal) as an upgrade to the ALICE experiment, to be installed during LS3 for data-taking in 2027–2029 at the LHC. The FoCal is a highly granular Si+W electromagnetic calorimeter combined with a conventional sampling hadronic calorimeter covering pseudorapidities of 3.4 < }eta < 5.8. The FoCal provides unique capabilities to measure small-x gluon distributions via prompt photon production and will significantly enhance the scope of ALICE for inclusive and correlation measurements with mesons, photons, and jets to explore the dynamics of hadronic matter at small x down to ~10^{ -6}
- Eur. Phys. J. CProduction of \(ω\) mesons in pp collisions at \(\sqrt{s}=\)7 TeVShreyasi Acharya, and othersEur. Phys. J. C, Jun 2020
The invariant differential cross section of inclusive }omega(782) meson production at midrapidity (\textbary\textbar\textless0.5) in pp collisions at }sqrt{s} = 7 TeV was measured with the ALICE detector at the LHC over a transverse momentum range of 2 \textless p_{}rm{T}} \textless 17 GeV/c. The }omega meson was reconstructed via its }omega}rightarrow}pi^+}pi^-}pi^0 decay channel. The measured }omega production cross section is compared to various calculations: PYTHIA 8.2 Monash 2013 describes the data, while PYTHIA 8.2 Tune 4C overestimates the data by about 50%. A recent NLO calculation, which includes a model describing the fragmentation of the whole vector-meson nonet, describes the data within uncertainties below 6 GeV/c, while it overestimates the data by up to 50% for higher p_{}rm{T}}. The }omega/}pi^0 ratio is in agreement with previous measurements at lower collision energies and the PYTHIA calculations. In addition, the measurement is compatible with transverse mass scaling within the measured p_{}rm{T}} range and the ratio is constant with C^{}omega/}pi^{0}} = 0.67 }pm 0.03 (stat) }pm 0.04 (sys) above a transverse momentum of 2.5 GeV/c.