A Large Ion Collider Experiment

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ALICE INDICO

update on - 23:31:42

ALICE Calendar

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ALICE is optimized to study the collisions of nuclei at the ultra-relativistic energies provided by the LHC. The aim is to study the physics of strongly interacting matter at the highest energy densities reached so far in the laboratory. In such conditions, an extreme phase of matter - called the quark-gluon plasma - is formed. Our universe is thought to have been in such a primordial state for the first few millionths of a second after the Big Bang, before quarks and gluons were bound together to form protons and neutrons. Recreating this primordial state of matter in the laboratory and understanding how it evolves will allow us to shed light on questions about how matter is organized and the mechanisms that confine quarks and gluons. For this purpose, we are carrying out a comprehensive study of the hadrons, electrons, muons, and photons produced in the collisions of heavy nuclei (²⁰⁸Pb). ALICE is also studying proton-proton and proton-nucleus collisions both as a comparison with nucleus-nucleus collisions and in their own right. In 2021, ALICE completed a significant upgrade of its detectors to further enhance its capabilities and continue its scientific journey at the LHC in Run 3 and 4, until the end of 2032. At the same time, upgrade plans are being made for ALICE 3, the next-generation experiment for LHC Runs 5 and 6.

Recent highlights

A new probe of radial flow

ALICE and ATLAS results demonstrate that the isotropic expansion of the QGP in heavy-ion collisions exhibits clear signatures of collective behaviour: Read more

ALICE Thesis Award 2025

On 15 July 2025, the ALICE collaboration celebrated its PhD thesis award winners during a special function held as a part of the ALICE week collaboration meeting at CERN: Read more

Oxygen collisions at the LHC

Oxygen collisions at the LHC: Collapsing the nuclear wave function: read more ....

Latest ALICE Submissions

Multiplicity dependence of K$^(892)^{\pm}$ production in pp collisions at $\sqrt{s}$ = 13 TeVThe first results of K$^$(892)$^{\pm}$ production at midrapidity ($\|y\| < ~ 0.5$) in pp collisions at $\sqrt{s} = 13$ TeV as a function of the event multiplicity are presented. The K$^$(892)$^{\pm}$ has been reconstructed via its hadronic decay channel K$^$(892)$^{\pm} \rightarrow \pi^{\pm} + K_{\rm S}^0$ using the ALICE detector at the LHC. For each multiplicity class the differential transverse momentum ($p_{\rm T}$) spectrum, the mean transverse momentum $\langle p_{\rm T} \rangle$, the $p_{\rm T}$-integrated yield (d$N$/d$y$), and the ratio of the K$^$(892)$^{\pm}$ to $K_{\rm S}^0$ yields are reported. These are consistent with previous K$^$(892)$^0$ resonance results with a higher level of precision. Comparisons with phenomenological models such as PYTHIA6, PYTHIA8, EPOS-LHC, and DIPSY are also discussed. A first evidence of a significant K$^$(892)$^{\pm}$/$K_{\rm S}^0$ suppression in pp collisions is observed at a 7$\sigma$ level passing from low to high multiplicity events. The ratios of the $p_{\rm T}$-differential yields of K$^$(892)$^{\pm}$ and $K_{\rm S}^0$ in high and low multiplicity events are also presented along with their double ratio. For $p_{\rm T} \lesssim 2$ GeV/$c$ this double ratio persists below unity by more than $3\sigma$ suggesting that the suppression affects mainly low $p_{\rm T}$ resonances. The measured decreasing trend of the K$^*$(892)$^{\pm}$/$K_{\rm S}^0$ ratio with increasing multiplicity, which in heavy-ion collisions is typically attributed to the rescattering of decay particles of the short-lived resonances, is reproduced by the EPOS-LHC model without the use of hadronic afterburners.	2507.19332
Multiplicity dependence of f$_0$(980) production in pp collisions at $\sqrt{s} = 13$ TeV The dependence of f$_0$(980) production on the final-state charged-particle multiplicity is reported for proton-proton (pp) collisions at the centre-of-mass energy, $\sqrt{s}= 13$ TeV. The production of f$_0$(980) is measured with the ALICE detector via the f$_0(980) \rightarrow \pi^{+}\pi^{-}$ decay channel in a midrapidity region of $\|y\| < ~ 0.5$. The evolution of the integrated yields and mean transverse momentum of f$_{0}$(980) as a function of charged-particle multiplicity measured in pp at $\sqrt{s} = 13$ TeV follows the trends observed in pp at $\sqrt{s} = 5.02$ TeV and in proton-lead (p-Pb) collisions at $\sqrt{s_{\rm{NN}}} = 5.02$ TeV. Particle yield ratios of f$_{0}$(980) to $\pi^{\pm}$ and K$^{*}$(892)$^{0}$ are found to decrease with increasing charged-particle multiplicity. These particle ratios are compared with calculations from the canonical statistical thermal model as a function of charged-particle multiplicity. The thermal model calculations provide a better description of the decreasing trend of particle ratios when no strange or antistrange quark composition for f$_{0}$(980) is assumed, which suggests that the tetraquark interpretation of the f$_{0}$(980) is disfavored.	2507.19347
Medium-induced modification of azimuthal correlations of electrons from heavy-flavor hadron decays with charged particles in Pb-Pb collisions at $\sqrt{s_{\rm{NN}} = 5.02}$ TeV The azimuthal-correlation distributions between electrons from the decays of heavy-flavor hadrons and associated charged particles in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV are reported for the 0-10% and 30-50% centrality classes. This is the first measurement to provide access to the azimuthal-correlation observables in the heavy-flavor sector in Pb-Pb collisions. The analysis is performed for trigger electrons from heavy-flavor hadron decays with transverse momentum $4 < ~ p_{\rm T}^{\rm e} < ~ 16$ GeV/$c$, considering associated particles within the transverse-momentum range $1 < ~ p_{\rm T}^{\rm assoc} < ~ 7$ GeV/$c$, and a pseudorapidity difference of $\|\Delta\eta\| < ~ 1$ between the trigger electron and associated particles. The per-trigger nuclear modification factor ($I_{\rm AA}$) is calculated to compare the near- and away-side peak yields to those in pp collisions at $\sqrt{s} = 5.02$ TeV. In 0-10% central collisions, the $I_{\rm AA}$ indicates a hint of enhancement of associated-particle yields with $p_{\rm T} < ~ 3$ GeV/$c$ on the near side, and a suppression of yields with $p_{\rm T} > 4$ GeV/$c$ on the away side. The $I_{\rm AA}$ for electron triggers from heavy-flavor hadron decays is compared with that for light-flavor and strange-particle triggers to investigate the dependence on different fragmentation processes and parton-medium dynamics, and is found to be the same within uncertainties.	2507.13197
$\overlineΣ^{\pm}$ production in pp and p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE The transverse momentum spectra and integrated yields of $\overline{\Sigma}^{\pm}$ have been measured in pp and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV with the ALICE experiment. Measurements are performed via the newly accessed decay channel $\overline{\Sigma}^{\pm} \rightarrow {\rm\overline{n}}\pi^{\pm}$. A new method of antineutron reconstruction with the PHOS electromagnetic spectrometer is developed and applied to this analysis. The $p_{\rm T}$ spectra of $\overline{\Sigma}^{\pm}$ are measured in the range $0.5 < ~ p_{\rm T} < ~ 3$ GeV/$c$ and compared to predictions of the PYTHIA 8, DPMJET, PHOJET, EPOS LHC and EPOS4 models. The EPOS LHC and EPOS4 models provide the best descriptions of the measured spectra both in pp and p-Pb collisions, while models which do not account for multiparton interactions provide a considerably worse description at high $p_{\rm T}$. The total yields of $\overline{\Sigma}^{\pm}$ in both pp and p-Pb collisions are compared to predictions of the Thermal-FIST model and dynamical models PYTHIA 8, DPMJET, PHOJET, EPOS LHC and EPOS4. All models reproduce the total yields in both colliding systems within uncertainties. The nuclear modification factors $R_{\rm pPb}$ for both $\overline{\Sigma}^{+}$ and $\overline{\Sigma}^{-}$ are evaluated and compared to those of protons, $\Lambda$ and $\Xi$ hyperons, and predictions of EPOS LHC and EPOS4 models. No deviations of $R_{\rm pPb}$ for $\overline{\Sigma}^{\pm}$ from the model predictions or measurements for other hadrons are found within uncertainties.	2507.13183
Study of $\langle p_{\mathrm{T}} \rangle$ and its higher moments, and extracting the speed of sound in $\mathrm{Pb}-\mathrm{Pb}$ collisions with ALICEUltrarelativistic heavy-ion collisions produce a state of hot and dense strongly interacting QCD matter called quark--gluon plasma (QGP). On an event-by-event basis, the volume of the QGP in ultra-central collisions is mostly constant, while its total entropy can vary significantly due to quantum fluctuations, leading to variations in the temperature of the system. Exploiting this unique feature of ultra-central collisions, allows to interpret the correlation of the mean transverse momentum $(\langle p_{\mathrm{T}} \rangle)$ of produced charged hadrons and the number of charged hadrons as a measure for the speed of sound, $c_{s}$. The speed of sound, $c_{s}$, which is related to the speed at which compression waves travel in a certain type of medium, in this case the QGP, is determined by fitting the relative increase of the $\langle p_{\mathrm{T}} \rangle$ with respect to the relative change of the average charged-particle density $(\langle \mathrm{d}N_\mathrm{ch}/\mathrm{d}\eta \rangle)$ measured at midrapidity. This study reports the variance, skewness, and kurtosis of the event-by-event transverse momentum per charged particle $([p_{\mathrm{T}}])$ distribution, as well as the $\langle p_{\mathrm{T}} \rangle$ of charged particles in ultra-central Pb--Pb collisions at center-of-mass energy of 5.02 TeV per nucleon pair using the ALICE detector. Different centrality estimators based on charged-particle multiplicity or the transverse energy of the event are used to select ultra-central collisions. By ensuring a pseudorapidity gap between the region used to define the centrality and the region to perform the measurement, the influence of biases and their potential effects on the rise of the mean transverse momentum is tested. The measured $c_{s}^{2}$ is found to strongly depend on the type of the centrality estimator and ranges between $0.115 \pm 0.0028 \, \mathrm{(stat)} \pm 0.0065 \, \mathrm{(syst)}$ and $0.437 \pm 0.0018 \, \mathrm{(stat)} \pm 0.0184 \, \mathrm{(syst)}$ in natural units. The self-normalized variance shows a steep decrease towards ultra-central collisions, while the self-normalized skewness show a maximum, followed by fast decrease. These non-Gaussian features are understood in terms of the vanishing of the impact parameter fluctuations contributing to the event-to-event $[p_{\mathrm{T}}]$ distribution.	2506.10394

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Upcoming Conferences (Next Week)

Quantum25

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Jobs info

ALICE Job - Post-doc Position | Stefan Meyer Institute, Austrian Academy of Sciences (08-07-2025 )

ALICE Job - PhD Position | Stefan Meyer Institute, Austrian Academy of Sciences (08-07-2025 )

ALICE Job - PhD Research Fellow in Experimental Subatomic Physics | University of Bergen (08-07-2025 )

ALICE Job - Open Call for Female Candidates: Professor Position in the Institute of Pure and Applied Sciences | University of Tsukuba (03-07-2025 )

Job - 20 faculty positions (Women-only, Univ. of Tsukuba) (26-06-2025 )

Diversity and Inclusivity in ALICE

The ALICE Collaboration embraces and values the diversity of its team members and colleagues. We are committed to fostering an inclusive environment for all people regardless of their nationality/culture, profession, age/generation, family situation and gender, as well as individual differences such as but not limited to ethnic origin, sexual orientation, belief, disability, or opinions provided that they are consistent with the Organization’s values.