Dr. Florian Jonas

Research

I am a physicist working on the ALICE experiment at the Large Hadron Collider (LHC). My main research interests include:

• Prompt Photons: Using isolated photons to probe the gluon density in protons and nuclei (gluon saturation) and to test perturbative QCD.
• Calorimetry: R&D and performance studies for the ALICE Forward Calorimeter (FoCal), operation of the ALICE Electromagnetic Calorimeter (EMCal) as deputy system runcoordinator
• Jets: Measuring jets and their correlations with photons to study energy loss in the Quark-Gluon Plasma (QGP)
• Phenomenology: I always had a passion for phenomenology. Currently I am doing various phenomenological studies related to cold nuclear matter effects and the Quark-Gluon Plasma (QGP), as well as for the future FCC-ee collider.

Publications

Selected publications in chronological order. Citation counts and journal references are pulled from INSPIRE-HEP

1. Abstract: The physics case for the operation of high-luminosity proton-nucleus (pA) collisions at the CERN 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 quantum chromodynamics and parton saturation, hadron spectroscopy, baseline studies for quark-gluon plasma and parton collectivity, double and triple parton scatterings, photon–photon collisions, and physics beyond the Standard Model; 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 than collected to date. [Close] Physics with high-luminosity proton-nucleus collisions at the LHC
   D. d'Enterria, C. Flett, I. Grabowska-Bold, C. Hadjidakis, P. Kotko, A. Kusina, J. Lansberg, R. McNulty, M. Rinaldi, L. Bonechi, R. Bruce, C. Da Silva, E. Ferreiro, S. Fichet, L. Harland-Lang, G. Innocenti, F. Jonas, J. Jowett, R. Longo, K. Lynch et al.
   J.Phys.G 52 (2025), 090501
   [Abstract] [arXiv:2504.04268] [DOI] [INSPIRE] [PDF] (3 citations)

2. Abstract: This paper presents the measurement of the isolated prompt photon inclusive production cross section in pp and p–Pb collisions by the ALICE Collaboration at the LHC. The measurement is performed in p–Pb collisions at centre-of-mass energies per nucleon pair of $\sqrt{s_{\text{NN}}}=5.02\text{TeV}$ and 8.16 TeV, as well as in pp collisions at $\sqrt{s}=5.02\text{TeV}$ and 8 TeV. The cross section is obtained at midrapidity $(|y|<0.7)$ using a charged-track based isolation momentum $p_{\text{T}}^{\text{iso,~ch}}<1.5\text{GeV}/c$ in a cone with radius $R=0.4$. The data for both collision systems are well reproduced by perturbative QCD (pQCD) calculations at next-to-leading order (NLO) using recent parton distribution functions for free (PDF) and bound (nPDF) nucleons. Furthermore, the nuclear modification factor $R_{\text{pA}}$ for both collision energies is consistent with unity for $p_{\text{T}}>20\text{GeV}/c$. However, deviations from unity ($R_{\text{pA}}<1$) of up to 20% are observed for $p_{\text{T}}<20\text{GeV}/c$ with limited significance, indicating the possible presence of nuclear effects in the initial state of the collision. The suppression increases with decreasing $p_{\text{T}}$ with a significance of $2.3\text{upsigma}$ for a non-zero slope and yields $R_{\text{pA}}<1$ with a significance of $1.8\text{upsigma}$ at $\sqrt{s_{\text{NN}}}=8.16\text{TeV}$ for $p_{\text{T}}<20\text{GeV}/c$. In addition, a significance of $1.1\text{upsigma}$ is observed for $R_{\text{pA}}<1$ at the lower collision energy $\sqrt{s_{\text{NN}}}=5.02\text{TeV}$ for $p_{\text{T}}<14\text{GeV}/c$. The magnitude and shape of the suppression are consistent with pQCD predictions at NLO using nPDFs that incorporate nuclear shadowing effects in the Pb nucleus. [Close] Measurement of isolated prompt photon production in pp and p–Pb collisions at the LHC
   S. Acharya, A. Agarwal, G. Aglieri Rinella et al. (ALICE Collaboration)
   Eur.Phys.J.C 85 (2025), 1407
   [Abstract] [arXiv:2502.18054] [DOI] [INSPIRE] [PDF] (3 citations)

3. Abstract: The p${}_T$-differential cross section of ω meson production in pp collisions at $\sqrt{s}$ = 13 TeV at midrapidity (|y| < 0.5) was measured with the ALICE detector at the LHC, covering an unprecedented transverse-momentum range of 1.6 < p${}_T$< 50 GeV/c. The meson is reconstructed via the ω → π${}^{+}$π${}^{-}$π${}^0$ decay channel. The results are compared with various theoretical calculations: PYTHIA8.2 with the Monash 2013 tune overestimates the data by up to 50%, whereas good agreement is observed with Next-to-Leading Order (NLO) calculations incorporating ω fragmentation using a broken SU(3) model. The ω/π${}^0$ ratio is presented and compared with theoretical calculations and the available measurements at lower collision energies. The presented data triples the p${}_T$ ranges of previously available measurements. A constant ratio of C${}^{\omega /\pi 0}$ = 0.578 ± 0.006 (stat.) ± 0.013 (syst.) is found above a transverse momentum of 4 GeV/c, which is in agreement with previous findings at lower collision energies within the systematic and statistical uncertainties.[graphic not available: see fulltext] [Close] Measurement of ω meson production in pp collisions at $\sqrt{s}$ = 13 TeV
   S. Acharya, D. Adamova, A. Agarwal et al. (ALICE Collaboration)
   JHEP 04 (2025), 067
   [Abstract] [arXiv:2411.09432] [DOI] [INSPIRE] [PDF] (2 citations)

4. Abstract: The ALICE Collaboration at the CERN LHC has measured the inclusive production cross section of isolated photons at midrapidity as a function of the photon transverse momentum ($p_{\text{T}}^{\gamma }$), in Pb–Pb collisions in different centrality intervals, and in pp collisions, at centre-of-momentum energy per nucleon pair of $\sqrt{s_{\text{NN}}}=5.02$ TeV. The photon transverse momentum range is between 10–14 and 40–140 GeV/$c$, depending on the collision system and on the Pb–Pb centrality class. The result extends to lower $p_{\text{T}}^{\gamma }$ than previously published results by the ATLAS and CMS experiments at the same collision energy. The covered pseudorapidity range is $|{\eta }^{\gamma }|<0.67$. The isolation selection is based on a charged particle isolation momentum threshold $p_{\text{T}}^{\mathrm{iso},\mathrm{ch}}=1.5$ GeV/$c$ within a cone of radii $R=0.2$ and 0.4. The nuclear modification factor is calculated and found to be consistent with unity in all centrality classes, and also consistent with the HG-PYTHIA model, which describes the event selection and geometry biases that affect the centrality determination in peripheral Pb–Pb collisions. The measurement is compared to next-to-leading order perturbative QCD calculations and to the measurements of isolated photons and Z${}^0$ bosons from the CMS experiment, which are all found to be in agreement. [Close] Measurement of the inclusive isolated-photon production cross section in pp and Pb–Pb collisions at $\sqrt{{\mathit{\text{s}}}_{\mathbf{NN}}}\mathbf{=}\mathbf{5.02}$ TeV
   S. Acharya, A. Agarwal, G. Aglieri Rinella et al. (ALICE Collaboration)
   Eur.Phys.J.C 85 (2025), 553
   [Abstract] [arXiv:2409.12641] [DOI] [INSPIRE] [PDF] (9 citations)

5. Abstract: 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. [Close] Assessing the mental health state of LHC scientists
   F. Jonas, L. Quaglia, C. Reetz, H. Bossi, S. Rasanen, S. Speziali, K. Coldham (ALICE Collaboration)
   (2025)
   [Abstract] [INSPIRE] [PDF] (0 citations)

6. Abstract: 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 pseudorapidity $3.2<\eta <5.8$. 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. Furthermore, FoCal will enable to carry out inclusive and correlation measurements of photons, neutral mesons, and jets in hadronic \pp\ and \pPb\ collisions, as well as J/$\psi$ production in ultra-peripheral \pPb\ and \PbPb\ collisions, and hence significantly enhances 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 $x\sim {10}^{-6}$. [Close] Technical Design Report of the ALICE Forward Calorimeter (FoCal)
   (ALICE Collaboration)
   Preprint (2024)
   [Abstract] [INSPIRE] (23 citations)

7. Abstract: We present the performance of a full-length prototype of theALICE Forward Calorimeter (FoCal). The detector is composed of asilicon-tungsten electromagnetic sampling calorimeter withlongitudinal and transverse segmentation (FoCal-E) of about 20X${}_0$ and a hadronic copper-scintillating-fiber calorimeter (FoCal-H) ofabout 5λ${}_{int}$. The data were taken in various testbeam campaigns between 2021 and 2023 at the CERN PS and SPS beamlines with hadron beams up to energies of 350 GeV, and electronbeams up to 300 GeV. Regarding FoCal-E, we report acomprehensive analysis of its response to minimum ionizing particlesacross all pad layers, employing various operational modes includingdifferent pre-amplifier and bias voltage settings. The longitudinalshower profile of electromagnetic showers is measured with alayer-wise segmentation of 1X${}_0$. As a projection to theperformance of the final detector in electromagnetic showers, wedemonstrate linearity in the full energy range, and show that theenergy resolution fulfills the requirements for the physics needs.Additionally, the performance to separate two-showers events wasstudied by quantifying the transverse shower width. RegardingFoCal-H, we report a detailed analysis of the response to hadronbeams between 60 and 350 GeV. The results are compared tosimulations obtained with a Geant4 model of the test beamsetup, which in particular for FoCal-E are in good agreement withthe data. The energy resolution of FoCal-E was found to be lowerthan 3% at energies larger than 100 GeV. The response ofFoCal-H to hadron beams was found to be linear, albeit with asignificant intercept that is about factor 2 larger than insimulations. Its resolution, which is non-Gaussian and generallylarger than in simulations, was quantified using the FWHM, anddecreases from about 16% at 100 GeV to about 11% at 350 GeV.The discrepancy to simulations, which is particularly evident at lowhadron energies, needs to be further investigated. [Close] Performance of the electromagnetic and hadronic prototype segments of the ALICE Forward Calorimeter
   M. Aehle, J. Alme, C. Arata, I. Arsene, I. Bearden, T. Bodova, V. Borshchov, O. Bourrion, M. Bregant, A. Brink, V. Buchakchiev, A. Buhl, T. Chujo, L. Dufke, V. Eikeland, M. Fasel, N. Gauger, A. Gautam, A. Ghimouz, Y. Goto et al.
   JINST 19 (2024), P07006
   [Abstract] [arXiv:2311.07413] [DOI] [INSPIRE] [PDF] (11 citations)

8. Abstract: 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 pseudo-rapidity interval of $3.2<\eta <5.8$. The FoCal design is optimized to measure isolated photons at forward rapidity for $p_{\mathrm{T}}\gtrsim 4$ GeV/$c$, as well as neutral hadrons, vector mesons, and jets. Measurements of the inclusive distributions and correlations of these observables probe the structure of matter down to $x\sim {10}^{-6}$, providing incisive tests of linear and non-linear QCD evolution at low $x$. This document presents current projections of the FoCal measurement performance for these observables. [Close] Physics performance of the ALICE Forward Calorimeter upgrade
   (ALICE Collaboration)
   (2023)
   [Abstract] [INSPIRE] [PDF] (7 citations)

9. Abstract: 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 $p_{\mathrm{T}}\gtrsim 4$ 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. [Close] Physics of the ALICE Forward Calorimeter upgrade
   (ALICE Collaboration)
   (2023)
   [Abstract] [INSPIRE] [PDF] (17 citations)

10. Abstract: The performance of the electromagnetic calorimeter of theALICE experiment during operation in 2010–2018 at the Large HadronCollider is presented. After a short introduction into the design,readout, and trigger capabilities of the detector, the proceduresfor data taking, reconstruction, and validation are explained. Themethods used for the calibration and various derived corrections arepresented in detail. Subsequently, the capabilities of thecalorimeter to reconstruct and measure photons, light mesons,electrons and jets are discussed. The performance of thecalorimeter is illustrated mainly with data obtained with test beamsat the Proton Synchrotron and Super Proton Synchrotron or inproton-proton collisions at √s = 13 TeV, and compared tosimulations. [Close] Performance of the ALICE Electromagnetic Calorimeter
    S. Acharya, D. Adamova, A. Adler et al. (ALICE Collaboration)
    JINST 18 (2023), P08007
    [Abstract] [arXiv:2209.04216] [DOI] [INSPIRE] [PDF] (35 citations)

11. Abstract: Recent data on the nuclear modification of $W$ and $Z$ boson production measured by the ATLAS collaboration in PbPb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$ 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 with 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. [Close] Centrality dependence of electroweak boson production in PbPb collisions at the CERN Large Hadron Collider
    F. Jonas, C. Loizides
    Phys.Rev.C 104 (2021), 044905
    [Abstract] [arXiv:2104.14903] [DOI] [INSPIRE] (12 citations)

12. Abstract: 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 ~${10}^{-6}$ [Close] Letter of Intent: A Forward Calorimeter (FoCal) in the ALICE experiment
    (ALICE Collaboration)
    Preprint (2020)
    [Abstract] [INSPIRE] [PDF] (56 citations)

13. Abstract: The invariant differential cross section of inclusive $\omega (782)$ meson production at midrapidity ($|y|<0.5$) in pp collisions at $\sqrt{s}=7\text{TeV}$ was measured with the ALICE detector at the LHC over a transverse momentum range of $2<p_{\mathrm{T}}<17\text{GeV}/c$. The $\omega$ meson was reconstructed via its $\omega \to {\pi }^{+}{\pi }^{-}{\pi }^0$ 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 $6\text{GeV}/c$, while it overestimates the data by up to 50% for higher $p_{\mathrm{T}}$. 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 $p_{\mathrm{T}}$ range and the ratio is constant with $C^{\omega /{\pi }^0}=0.67\pm 0.03\text{~(stat)~}\pm 0.04\text{~(sys)~}$ above a transverse momentum of $2.5\text{GeV}/c$. [Close] Production of $\omega$ mesons in pp collisions at $\sqrt{\mathbf{s}}\mathbf{=}\mathbf{7}\mathbf{\text{TeV}}$
    S. Acharya, D. Adamova, A. Adler et al. (ALICE Collaboration)
    Eur.Phys.J.C 80 (2020), 1130
    [Abstract] [arXiv:2007.02208] [DOI] [INSPIRE] [PDF] (16 citations)

Talks

Selected talks and posters in chronological order.

1. ALICE overview: hard probes and nPDFs [talk]
   Light ion collisions at the LHC 2025
   December 2025.
   [Slides]

2. Prompt photon measurements in small systems with ALICE [poster]
   31st Quark Matter Conference
   September 2025.
   [Slides]

3. ALICE status report [plenary talk]
   161th LHCC Meeting OPEN Session
   March 2025.
   [Slides]

4. High-density QCD physics and the study of the QGP in the high-lumi LHC era [talk]
   Workshop on High Luminosity LHC and Hadron Colliders
   October 2024.
   [Slides]

5. Future Facilities: Heavy-ion physics at the LHC [plenary talk]
   12th Hard Probes conference
   September 2024.
   [Slides]

6. ALICE studies and plans in hadronic proton-nucleus collisions at the LHC [talk]
   Physics with high-luminosity proton-nucleus collisions at the LHC - Workshop
   July 2024.
   [Slides]

7. Heavy-ion physics at the HL-LHC experiments [multi-exp talk]
   12th LHCP conference
   June 2024.
   [Slides]

8. Prompt photons: A versatile probe for heavy-ion collisions [talk]
   ALICE USA meeting at Yale
   May 2024.

9. Connecting forward LHC and the EIC: the ALICE FoCal upgrade [talk]
   Joint ECFA-NuPECC-APPEC activity workshop: Synergies between the EIC and the LHC
   December 2023.
   [Slides]

10. The ALICE Forward Calorimeter (FoCal) upgrade: physics program and prototype performance [poster]
    156th LHCC Meeting
    November 2023.
    [Slides]

11. Measuring prompt photon production with the ALICE Forward Calorimeter (FoCal) upgrade [talk & poster]
    798. WE-Heraeus-Seminar: Forward Physics and QCD at the LHC and EIC
    October 2023.

12. Forward Calorimeter (FoCal): Physics and performance [talk]
    30th Quark Matter Conference
    September 2023.
    [Slides]

13. Probing the initial state of nuclear collisions using isolated prompt photons with ALICE [talk]
    11th Hard Probes Conference
    March 2023.
    [Slides]

14. Isolated photon production in pp and p--Pb collisions at $\sqrts [talk]
    ALICE USA meeting
    May 2022.
    [Slides]

15. Prompt photon physics with the ALICE FoCal [talk]
    Forward QCD: open questions and future directions (workshop)
    May 2022.
    [Slides]

16. Probing the initial state of nuclear collisions with isolated photons at the LHC [talk]
    Invited speaker at Oak Ridge National Laboratory physics division seminar
    May 2022.
    [Slides]

17. Probing the initial state of nuclear collisions with isolated photons at the LHC [talk]
    Invited speaker at Institute for Nuclear Physics (Münster) seminar
    June 2022.

18. $\omega$ and ${\eta }^{\prime }$ production in proton-proton collisions at the LHC measured with ALICE [talk]
    40th ICHEP conference
    June 2020.
    [Slides]

19. Measurement of $\omega$ mesons in pp collisions at $\sqrts [talk]
    Talk at DPG Spring Meeting
    June 2019.

20. Measurement of $\omega$ and $\eta$ mesons via their three pion decay with ALICE in pp collisions at $\sqrts [poster]
    137th LHCC meeting
    June 2019.
    [Slides]

21. Measurement of $\omega$ and $\eta$ mesons via their three pion decay with ALICE in pp collisions at $\sqrts [poster]
    DPG Spring Meeting
    June 2018.

22. Kinematic cuts for $\omega$ reconstruction in ALICE [talk]
    ALICE Germany Meeting
    June 2016.

Curriculum Vitae

Acknowledgements

This website is based on the latex-css project by Vincent Dörig. I have heavily modified itto include things I need, such as a moving sidebar, inspire-hep pulling for abstract and journal information for the publications, as well as the abstract display in the sidebar. I thank INSPIRE-HEP for making their REST API publicly available. As I am a physicist and not a web developer, this would not have been possible without the help of LLMs, in particular Google Gemini 3 Pro. The source code for this website is freely available on GitHub under the MIT license.

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