ALICE mission

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

 

Recent highlights

ICHEP 2024 is taking place at Prague (18 - 24 July). ALICE has a major presence in the Conference: Read more
The ALICE collaboration week was held at CERN from 8 to 12 July 2024. The ALICE Summer party took place on 10 July, attended by ~300 ALICE collaborators and friends: Read more
On 9 July 2024, the ALICE collaboration celebrated its PhD thesis award winners in a special function organised as a part of the ALICE week collaboration meeting at CERN: Read more

Latest ALICE Submissions

Measurement of beauty production via non-prompt charm hadrons in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV The production cross sections of $\mathrm {D^0}$, $\mathrm {D^+}$, and $\mathrm {\Lambda_{c}^{+}}$ hadrons originating from beauty-hadron decays (i.e. non-prompt) were measured for the first time at midrapidity in proton$-$lead (p$-$Pb) collisions at the center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV. Nuclear modification factors ($R_{\mathrm {pPb}}$) of non-prompt $\mathrm {D^0}$, $\mathrm {D^+}$, and $\mathrm {\Lambda_{c}^{+}}$ are calculated as a function of the transverse momentum ($p_{\mathrm T}$) to investigate the modification of the momentum spectra measured in p$-$Pb collisions with respect to those measured in proton$-$proton (pp) collisions at the same energy. The $R_{\mathrm {pPb}}$ measurements are compatible with unity and with the measurements in the prompt charm sector, and do not show a significant $p_{\mathrm T}$ dependence. The $p_{\mathrm T}$-integrated cross sections and $p_{\mathrm T}$-integrated $R_{\mathrm {pPb}}$ of non-prompt $\mathrm {D^0}$ and $\mathrm {D^+}$ mesons are also computed by extrapolating the visible cross sections down to $p_{\mathrm T}$ = 0. The non-prompt D-meson $R_{\mathrm {pPb}}$ integrated over $p_{\mathrm T}$ is compatible with unity and with model calculations implementing modification of the parton distribution functions of nucleons bound in nuclei with respect to free nucleons. The non-prompt $\mathrm {\Lambda_{c}^{+}/D^{0}}$ and $\mathrm{D^+/D^0}$ production ratios are computed to investigate hadronisation mechanisms of beauty quarks into mesons and baryons. The measured ratios as a function of $p_{\mathrm T}$ display a similar trend to that measured for charm hadrons in the same collision system.
2407.10593
Rapidity dependence of antideuteron coalescence in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE The production yields of antideuterons and antiprotons are measured in pp collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV, as a function of transverse momentum ($p_{\rm T}$) and rapidity ($y$), for the first time up to $|y|= 0.7$. The measured spectra are used to study the $p_{\rm T}$ and rapidity dependence of the coalescence parameter $B_2$, which quantifies the coalescence probability of antideuterons. The $p_{\rm T}$ and rapidity dependence of the obtained $B_2$ is extrapolated for $p_{\rm T}> 1.7$ GeV/$c$ and $|y|>0.7$ using the phenomenological antideuteron production model implemented in PYTHIA 8.3 as well as a baryon coalescence afterburner model based on EPOS 3. Such measurements are of interest to the astrophysics community, since they can be used for the calculation of the flux of antinuclei from cosmic rays, in combination with coalescence models.
2407.10527
Measurement of the inclusive isolated-photon production cross section in pp collisions at $\sqrt{s}$ = 13 TeV The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at centre-of-momentum energy of $\sqrt{s}=13$ TeV collected during the LHC Run 2 data-taking period. The measurement is performed by combining the measurements of the electromagnetic calorimeter EMCal and the central tracking detectors ITS and TPC, covering a pseudorapidity range of $|\eta^{\gamma}| < ~0.67$ and a transverse momentum range of $7 < ~p_{\rm T}^{\gamma} < ~200$ GeV/$c$. The result extends to lower $p_{\rm T}^{\gamma}$ and $x_{\rm T}^{\gamma} = 2p_{\rm T}^{\gamma}/\sqrt{s}$ ranges, the lowest $x_{\rm T}^{\gamma}$ of any isolated photon measurements to date, extending significantly those measured by the ATLAS and CMS experiments towards lower $p_{\rm T}^{\gamma}$ at the same collision energy with a small overlap between the measurements. The measurement is compared with next-to-leading order perturbative QCD calculations and the results from the ATLAS and CMS experiments as well as with measurements at other collision energies. The measurement and theory prediction are in agreement with each other within the experimental and theoretical uncertainties.
2407.01165
Measurement of the production and elliptic flow of (anti)nuclei in Xe-Xe collisions at $\sqrt{s_{\rm NN}}$ = 5.44 TeV Measurements of (anti)deuteron and (anti)$^3$He production in the rapidity range $ |y| < ~ $ 0.5 as a function of the transverse momentum and event multiplicity in Xe$-$Xe collisions at a center-of-mass energy per nucleon$-$nucleon pair of $\sqrt{s_{\rm NN}}$ = 5.44 TeV are presented. The coalescence parameters $B_2$ and $B_3$ are measured as a function of the transverse momentum per nucleon. The ratios between (anti)deuteron and (anti)$^3$He yields and those of (anti)protons and pions are reported as a function of the mean charged-particle multiplicity density, and compared with two implementations of the statistical hadronization model (SHM) and with coalescence predictions. The elliptic flow of (anti)deuterons is measured for the first time in Xe$-$Xe collisions and shows features similar to those already observed in Pb$-$Pb collisions, i.e., the mass ordering at low transverse momentum and the meson$-$baryon grouping at intermediate transverse momentum. The production of nuclei is particularly sensitive to the chemical freeze-out temperature of the system created in the collision, which is extracted from a grand-canonical-ensemble-based thermal fit, performed for the first time including light nuclei along with light-flavor hadrons in Xe$-$Xe collisions. The extracted chemical freeze-out temperature $T_{\rm chem}$ = (154.2 $\pm$ 1.1) MeV in Xe$-$Xe collisions is similar to that observed in Pb$-$Pb collisions and close to the crossover temperature predicted by lattice QCD calculations.
2405.19826
Measurement of ${}_Λ^{3}\mathrm{H}$ production in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeVThe first measurement of $_{\Lambda}^{3}\mathrm{H}$ and $^3_ {\overline{\Lambda}}\overline{\mathrm{H}}$ differential production with respect to transverse momentum and centrality in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV is presented. The $_{\Lambda}^{3}\mathrm{H}$ has been reconstructed via its two-charged-body decay channel, i.e., $_{\Lambda}^{3}\mathrm{H} \rightarrow {}^{3}\mathrm{He} + \pi^{-}$. A Blast-Wave model fit of the $p_{\rm T}$-differential spectra of all nuclear species measured by the ALICE collaboration suggests that the $_{\Lambda}^{3}\mathrm{H}$ kinetic freeze-out surface is consistent with that of other nuclei. The ratio between the integrated yields of $_{\Lambda}^{3}\mathrm{H}$ and $^3\mathrm{He}$ is compared to predictions from the statistical hadronisation model and the coalescence model, with the latter being favoured by the presented measurements.
2405.19839
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Upcoming Conferences (Next Week)

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.