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ALICE collaboration

Publications and source records attributed to ALICE collaboration.

5 recordsLinked to original sources
arXiv2024

Recent results and upgrade of the ALICE muon spectrometer

The ALICE experiment at the CERN Large Hadron Collider (LHC) is a multi-purpose particle detector, mainly focused on the study of quark-gluon plasma (QGP) in heavy-ion collisions. In the forward rapidity region, 2.5 $<$ y $<$ 4, ALICE is equipped with a muon spectrometer (MS), which allows to study quarkonia and open heavy-flavor particles, both key probes to investigate QGP properties. Although in LHC Run 1 and 2 many important results were achieved, the front absorber of the MS represented a limit to the physics program, due to the multiple scattering and energy loss in the material. To assess this limitation, a new forward vertex tracker (Muon Forward Tracker, MFT) was installed between the inner tracking system (ITS) and the front absorber. This has enhanced the MS physics performance, enabling the separation of prompt/non-prompt charmonium production at forward rapidity. It will also allow one to reduce the combinatorial background from semi-leptonic decays of kaons and pions. Finally, it will greatly improve the invariant-mass resolution of the low-mass dimuon pairs. Moreover, during the ongoing LHC Run 3, the rate of Pb\textendash{}Pb collisions has been increased from 10~kHz (in Run 2) up to 50~kHz, allowing to collect a data sample about 5 times larger than the one recorded in Run 2. This contribution will provide a brief overview of the MS upgrades and it will focus on the expected physics performance during the LHC Run 3. Some of the preliminary results already obtained will also be shown.

nucl-ex↗
arXiv2017

Underlying Event measurements in pp collisions at $\sqrt{s}$ = 0.9 and 7 TeV with the ALICE experiment at the LHC

We present measurements of Underlying Event observables in pp collisions at $\sqrt{s}$ = 0.9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum $p_{\rm T, LT}$ in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different $p_{\rm T}$ thresholds: 0.15, 0.5 and 1.0 GeV/$c$. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track $p){\rm T}$ threshold considered. Data are compared to Pythia 6.4, Pythia 8.1 and Phojet. On average, all models considered underestimate the multiplicity and summed $p_{\rm T}$ in the Transverse region by about 10-30%.

hep-ex↗
arXiv2015

Precision measurement of the mass difference between light nuclei and anti-nuclei

The measurement of the mass differences for systems bound by the strong force has reached a very high precision with protons and anti-protons. The extension of such measurement from (anti-)baryons to (anti-)nuclei allows one to probe any difference in the interactions between nucleons and anti-nucleons encoded in the (anti-)nuclei masses. This force is a remnant of the underlying strong interaction among quarks and gluons and can be described by effective theories, but cannot yet be directly derived from quantum chromodynamics. Here we report a measurement of the difference between the ratios of the mass and charge of deuterons and anti-deuterons, and $^{3}{\rm He}$ and $^3\overline{\rm He}$ nuclei carried out with the ALICE (A Large Ion Collider Experiment) detector in Pb-Pb collisions at a centre-of-mass energy per nucleon pair of 2.76 TeV. Our direct measurement of the mass-over-charge differences confirm CPT invariance to an unprecedented precision in the sector of light nuclei. This fundamental symmetry of nature, which exchanges particles with anti-particles, implies that all physics laws are the same under the simultaneous reversal of charge(s) (charge conjugation C), reflection of spatial coordinates (parity transformation P) and time inversion (T).

nucl-ex↗
arXiv2001

ALICE, the heavy ion experiment at LHC

ALICE, A Large Ion Collider Experiment, is the future Large Hadron Collider (LHC) experiment at CERN devoted to the physics of Quantum Chromo-thermo-dynamics. Relativistic Heavy-Ion Collisions (HIC) at LHC aim at the production of a plasma of quarks and gluons (QGP). This plasma is expected to be much hotter, bigger and longer than in previous HIC experiments at lower center-of-mass energies. In the ALICE experiment, the ephemeral QGP created during the first stages of the HIC will be studied by the concomitant detection of most of the probes of high temperature strongly interacting matter.

hep-ex↗