A Large Ion Collider Experiment

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ALICE INDICO

update on - 16:17:58

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

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 ....

Oxygen Run at the LHC gets underway

proton-Oxygen Run at LHC ongoing, will be followed by Oxygen-Oxygen data taking: read more ....

Latest ALICE Submissions

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
Femtoscopic study of the proton-proton and proton-deuteron systems in heavy-ion collisions at the LHC This work reports femtoscopic correlations of p$-$p ($\bar{\rm p}-\bar{\rm p}$) and p$-$d ($\bar{\rm p}-\bar{\rm d}$) pairs measured in Pb$-$Pb collisions at center-of-mass energy $\sqrt{s_{\rm NN}}$ = 5.02 TeV by the ALICE Collaboration. A fit to the measured proton-proton correlation functions allows one to extract the dependence of the nucleon femtoscopic radius of the particle-emitting source on the pair transverse mass ($m_\text{T}$) and on the average charge particle multiplicity $\langle\text{dN}_\text{ch}/\text{d}\eta\rangle^{1/3}$ for three centrality intervals (0$-$10$\%$, 10$-$30$\%$, 30$-$50$\%$). In both cases, the expected power-law and linear scalings are observed, respectively. The measured p$-$d correlations can be described by both two- and three-body calculations, indicating that the femtoscopy observable is not sensitive to the short-distance features of the dynamics of the p$-$(p$-$n) system, due to the large inter-particle distances in Pb$-$Pb collisions at the LHC. Indeed, in this study, the minimum measured femtoscopic source sizes for protons and deuterons have a minimum value at $2.73^{+0.05}_{-0.05}$ and $3.10^{+1.04}_{-0.86}$ fm, respectively, for the 30$-$50$\%$ centrality collisions. Moreover, the $m_{\rm{T}}$-scaling obtained for the p$-$p and p$-$d systems is compatible within 1$\sigma$ of the uncertainties. These findings provide new input for fundamental studies on the production of light (anti)nuclei under extreme conditions.	2505.01061
Long-range transverse momentum correlations and radial flow in Pb$-$Pb collisions at the LHC This Letter presents measurements of long-range transverse-momentum correlations using a new observable, $v_{0}(p_\mathrm{T})$, which serves as a probe of radial flow and medium properties in heavy-ion collisions. Results are reported for inclusive charged particles, pions, kaons, and protons across various centrality intervals in Pb$-$Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV, recorded by the ALICE detector. A pseudorapidity-gap technique, similar to that used in anisotropic-flow studies, is employed to suppress short-range correlations. At low $p_\mathrm{T}$, a characteristic mass ordering consistent with hydrodynamic collective flow is observed. At higher $p_\mathrm{T}$ ($> 3$ GeV/$c$), protons exhibit larger $v_{0}(p_\mathrm{T})$ than pions and kaons, in agreement with expectations from quark-recombination models. These results are sensitive to the bulk viscosity and the equation of state of the QCD medium formed in heavy-ion collisions.	2504.04796
Energy-energy correlators in charm-tagged jets in proton-proton collisions at $\mathbf{\sqrt{s} = 13}$ TeV In this letter, we present the first measurement of the energy-energy correlator (EEC) in charm-tagged jets from proton-proton (pp) collisions at $\sqrt{s} = 13$ TeV. EECs probe the structure of QCD radiation, providing a unique test of mass-dependent effects in parton showers involving a charm quark and offering a distinct view into non-perturbative phenomena, including the hadronization process. The EEC is measured for charm-tagged jets and flavor-untagged (inclusive) jets with transverse momenta of $10 < ~ p_{\rm T} < ~ 30$ GeV/$c$, where charm-quark mass effects are significant. We observe a significant suppression of the EEC amplitude in charm jets compared to inclusive ones, consistent with the expected suppression of radiation from massive quarks -- a fundamental prediction of QCD. Despite the significant amplitude difference, the observed peak positions of the charm and inclusive-jet EEC are similar, indicating a complex interplay between Casimir factor (differentiating quark and gluon jets), and quark-mass (dead-cone) effects in the QCD parton shower as well as subsequent hadronization effects. Comparisons with next-to-leading order calculations and various Monte Carlo event generators reveal the sensitivity of this observable to both mass effects in the parton shower and hadronization process. These results provide new constraints on theoretical models of heavy-quark jets and offer insights into the parton-to-hadron transition in QCD.	2504.03431
Centrality dependence of charged-particle pseudorapidity density at midrapidity in Pb-Pb collisions at $\mathbf{\sqrt{\textit{s}_{\rm NN}} = 5.36}$ TeV The ALICE Collaboration reports its first LHC Run 3 measurements of charged-particle pseudorapidity density at midrapidity in Pb-Pb collisions at a centre-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=5.36$ TeV. Particle multiplicity in high-energy collisions characterises the system geometry, constrains particle-production mechanisms, and is used to estimate initial energy density. Multiplicity also acts as a reference for subsequent measurements as a function of centrality. In this letter, for the first time, charged particles are reconstructed using the upgraded ALICE Inner Tracking System and Time Projection Chamber, while the collision centrality is determined by measuring charged-particle multiplicities with the Fast Interaction Trigger system. Pseudorapidity density, ${\rm d}N_{\rm ch}/{\rm d}\eta$, is presented, averaged over events, for various centrality classes. Results are shown as a function of pseudorapidity and the average number of participating nucleons ($\langle N_{\mathrm{part}}\rangle$) in the collision. The average charged-particle pseudorapidity density ($\langle {\rm d}N_{\rm ch}/{\rm d}\eta \rangle$) at midrapidity ($\|\eta\| < ~0.5$) is 2047 $\pm$ 54 for the 5% most central collisions. The value of $\langle {\rm d}N_{\rm ch}/{\rm d}\eta \rangle$ normalised to $\langle N_{\mathrm{part}}\rangle/2$ as a function of $\sqrt{s_{\mathrm{NN}}}$ follows the trend established in previous measurements in heavy-ion collisions. Theoretical models based on mechanisms for particle production in nuclear collisions that involve the formation of quark-gluon plasma medium and models based on individual nucleon-nucleon interactions are compared to the data.	2504.02505

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Upcoming Conferences (Next Week)

XXXVII International Workshop on High Energy Physics “Diffraction of hadrons: Experiment, Theory, Phenomenology”

European Congress of Physics 2025

See all conferences...

Jobs info

ALICE Job - PhD Positions | Bari University, INFN (14-07-2025 )

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 )

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.