ALICE INDICO

update on - 12:55:15

ALICE Calendar

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The ALICE Collaboration has built a detector 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 is completing a significant upgrade of its detectors to further enhance its capabilities and continue its scientific journey at the LHC for many years to come.

Recent highlights

ALICE briefing for Strangeness in Quark Matter 2022

The ALICE Collaboration reports a wide range of new physics results at the International Conference on Strangeness in Quark Matter (SQM2022) this week (13-17 June 2022). The scope of the conference includes strangeness and heavy-flavour production, as well as correlations and fluctuations, as tools to study the quark-gluon plasma and the strong interaction in nuclei and in compact stars. The ALICE Collaboration participates in SQM2022 with 2 plenary, 26 parallel and 9 poster presenters. Read more...

ALICE makes first direct observation of the dead cone: a fundamental effect in QCD

The ALICE collaboration at the Large Hadron Collider (LHC) has made the first direct observation of the dead-cone effect – a fundamental feature of the theory of the strong force that binds quarks and gluons together into protons, neutrons, and, ultimately, all atomic nuclei. In addition to confirming this effect, the observation, reported in a paper published in Nature, provides direct experimental access to the mass of a single charm quark before it is confined inside hadrons. Read more...

ALICE briefing for LHCP2022

The ALICE Collaboration reports a wide range of new physics results at the Large Hadron Collider Physics conference (LHCP2022) this week (16-21 May 2022). The status of the upgraded detector commissioning for the LHC Run 3, prospects for further upgrades for Run 4, and the completely new heavy-ion detector ALICE 3 for Run 5 and beyond are also presented. The ALICE Collaboration participates in LHCP2022 with 6 plenary, 17 parallel and 11 poster presenters. The plenary presentation on 16 May reports the highlights of new ALICE measurements and the status of the experiment. A selection of these topics is presented in the following sections. Read more...

Latest ALICE Submissions

${\rm f}_{0}(980)$ production in inelastic pp collisions at $\sqrt{s} = 5.02$ TeVThe measurement of the production of ${\rm f}_{0}(980)$ in inelastic pp collisions at $\sqrt{s} = 5.02$ TeV is presented. This is the first reported measurement of inclusive ${\rm f}_{0}(980)$ production at LHC energies. The production is measured at midrapidity, $\|y\| < ~ 0.5$, in a wide transverse momentum range, $0 < ~ p_{\rm T} < ~ 16$ GeV/$c$, by reconstructing the resonance in the ${\rm f}_{0}(980) \rightarrow \pi^{+}\pi^{-}$ hadronic decay channel using the ALICE detector. The $p_{\rm T}$-differential yields are compared to those of pions, protons and $\phi$ mesons as well as to predictions from the HERWIG 7.2 QCD-inspired Monte Carlo event generator and calculations from a coalescence model that uses the AMPT model as an input. The ratio of the $p_{\rm T}$-integrated yield of ${\rm f}_{0}(980)$ relative to pions is compared to measurements in ${\rm e}^{+}{\rm e}^{-}$ and pp collisions at lower energies and predictions from statistical hadronisation models and HERWIG 7.2. A mild collision energy dependence of the ${\rm f}_{0}(980)$ to pion production is observed in pp collisions from SPS to LHC energies. All considered models underpredict the $p_{\rm T}$-integrated ${\rm f}_{0}(980)/(\pi^{+}+\pi^{-})$ ratio. The prediction from the $\gamma_{\rm s}$-CSM model assuming a zero total strangeness content of ${\rm f}_{0}(980)$ is consistent with the data within 1.9$\sigma$ and is the closest to the data. The results provide an essential reference for future measurements of the particle yield and nuclear modification in p$-$Pb and Pb$-$Pb collisions, which have been proposed to be instrumental to probe the elusive nature and quark composition of the ${\rm f}_{0}(980)$ scalar meson.	2206.06216
Anisotropic flow and flow fluctuations of identified hadrons in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeVThe first measurements of elliptic flow of $\pi^\pm$, ${\rm K}^\pm$, p+$\overline{\rm p}$, ${\rm K_{S}^0}$, $\Lambda$+$\overline{\Lambda}$, $\phi$, $\Xi^-$+$\Xi^+$, and $\Omega^-$+$\Omega^+$ using multiparticle cumulants in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV are presented. Results obtained with two- ($v_2\{2\}$) and four-particle cumulants ($v_2\{4\}$) are shown as a function of transverse momentum, $p_{\rm T}$, for various collision centrality intervals. Combining the data for both $v_2\{2\}$ and $v_2\{4\}$ also allows us to report the first measurements of the mean elliptic flow, elliptic flow fluctuations, and relative elliptic flow fluctuations for various hadron species. These observables probe the event-by-event eccentricity fluctuations in the initial state and the contributions from the dynamic evolution of the expanding quark-gluon plasma. The characteristic features observed in previous $p_{\rm T}$-differential anisotropic flow measurements for identified hadrons with two-particle correlations, namely the mass ordering at low $p_{\rm T}$ and the approximate scaling with the number of constituent quarks at intermediate $p_{\rm T}$, are similarly present in the four-particle correlations and the combinations of $v_2\{2\}$ and $v_2\{4\}$. In addition, a particle species dependence of flow fluctuations is observed that could indicate a significant contribution from final state hadronic interactions. The comparison between experimental measurements and CoLBT model calculations, which combine the various physics processes of hydrodynamics, quark coalescence, and jet fragmentation, illustrates their importance over a wide $p_{\rm T}$ range.	2206.04587
Observation of flow angle and flow magnitude fluctuations in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV at the LHCThis Letter reports on the first measurements of transverse momentum dependent flow angle $\Psi_n$ and flow magnitude $v_n$ fluctuations, determined using new four-particle correlators. The measurements are performed for various centralities in Pb-Pb collisions at a centre-of-mass energy of $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE at the LHC. Both flow angle and flow magnitude fluctuations are observed in the presented centrality ranges and are strongest in the most central collisions and for a transverse momentum $p_{\rm T}>2$ GeV/$c$. Comparison with theoretical models, including iEBE-VISHNU, MUSIC, and AMPT, show that the measurements bring novel insights into the fluctuating initial conditions that are not well known. In addition, these new results exhibit unique sensitivities to the specific shear viscosity, $\eta/s$, of the quark--gluon plasma (QGP) and to the initial state of the heavy-ion collisions. As such fluctuations are getting stronger with increasing $p_{\rm T}$, a re-examination of existing models is needed to have a more precise and unbiased extraction of properties of the QGP.	2206.04574
Towards the understanding of the genuine three-body interaction for p$-$p$-$p and p$-$p$-Λ$Three-body nuclear forces play an important role in the structure of nuclei and hypernuclei and are also incorporated in models to describe the dynamics of dense baryonic matter, such as in neutron stars. So far, only indirect measurements anchored to the binding energies of nuclei can be used to constrain the three-nucleon force, and if hyperons are considered, the scarce data on hypernuclei impose only weak constraints on the three-body forces. In this work, we present the first direct measurement of the p$-$p$-$p and p$-$p$-\Lambda$ systems in terms of three-particle mixed moments carried out for pp collisions at $\sqrt{s}$ = 13 TeV. Three-particle cumulants are extracted from the normalised mixed moments by applying the Kubo formalism, where the three-particle interaction contribution to these moments can be isolated after subtracting the known two-body interaction terms. A negative cumulant is found for the p$-$p$-$p system, hinting to the presence of a residual three-body effect while for p$-$p$-\Lambda$ the cumulant is consistent with zero. This measurement demonstrates the accessibility of three-baryon correlations at the LHC.	2206.03344
Closing in on critical net-baryon fluctuations at LHC energies: cumulants up to third order in Pb$-$Pb collisionsFluctuation measurements are important sources of information on the mechanism of particle production at LHC energies. This article reports the first experimental results on third-order cumulants of the net-proton distributions in Pb$-$Pb collisions at a center-of-mass energy $\sqrt{s_{\rm NN}} = 5.02$ TeV recorded by the ALICE detector. The results on the second-order cumulants of net-proton distributions at $\sqrt{s_{\rm NN}} = 2.76$ and $5.02$ TeV are also discussed in view of effects due to the global and local baryon number conservation. The results demonstrate the presence of long-range rapidity correlations between protons and antiprotons. Such correlations originate from the early phase of the collision. The experimental results are compared with HIJING and EPOS model calculations, and the dependence of the fluctuation measurements on the phase-space coverage is examined in the context of lattice quantum chromodynamics (LQCD) and hadron resonance gas (HRG) model estimations. The measured third-order cumulants are consistent with zero within experimental uncertainties of about 4% and are described well by LQCD and HRG predictions.	2206.03343

See all submissions...

Upcoming Conferences (Next Week)

QCD22 - Montpellier

ICHEP2022 XLI International Conference on High Energy Physics

See all conferences...

Jobs info

Job - vacancy notice in the CernVM team in CERN's EP-SFT group (22-06-2022)

Job - Post-doctoral position for working on sPHENIX at Baruch College, CUNY (22-06-2022)

Job - Phd Student and Post-Doc in Neutrino Physics (07-06-2022)

Job - 2 positions to work on the upgrade of the LHCb experiment at the Universitat de Barcelona (03-06-2022)

ALICE Job - PhD student position opening at Warsaw University of Technology (01-06-2022)

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.