Sk Noor Alam

Production of light nuclei and anti-nuclei in pp and Pb-Pb collisions at energies available at the CERN Large Hadron Collider

The production of (anti-)deuteron and (anti-)3He nuclei in Pb–Pb collisions at √ sNN = 2.76 TeV has been studied using the ALICE detector at the LHC. The spectra exhibit a significant hardening with increasing centrality. Combined blast-wave fits of several particles support the interpretation that this behavior is caused by an increase of radial flow. The integrated particle yields are discussed in the context of coalescence and thermal-statistical model expectations. The particle ratios, 3He/d and 3He/p, in Pb–Pb collisions are found to be in agreement with a common chemical freeze-out temperature of Tchem ≈ 156 MeV. These ratios do not vary with centrality which is in agreement with the thermal-statistical model. In a coalescence approach, it excludes models in which nucleus production is proportional to the particle multiplicity and favors those in which it is proportional to the particle density instead. In addition, the observation of 31 anti-tritons in Pb–Pb collisions is reported. For comparison, the deuteron spectrum in pp collisions at √ s = 7 TeV is also presented. While the p/π ratio is similar in pp and Pb–Pb collisions, the d/p ratio in pp collisions is found to be lower by a factor of 2.2 than in Pb–Pb collisions. ∗See Appendix A for the list of collaboration members ar X iv :1 50 6. 08 95 1v 3 [ nu cl -e x] 9 A pr 2 01 6 Production of light (anti-)nuclei in pp and Pb–Pb collisions at LHC energies ALICE Collaboration

Enhanced production of multi-strange hadrons in high-multiplicity proton-proton collisions

At sufficiently high temperature and energy density, nuclear matter undergoes a transition to a phase in which quarks and gluons are not confined: the Quark-Gluon Plasma (QGP) [1]. Such an extreme state of strongly-interacting QCD (Quantum Chromo-Dynamics) matter is produced in the laboratory with high-energy collisions of heavy nuclei, where an enhanced production of strange hadrons is observed [2-6]. Strangeness enhancement, originally proposed as a signature of QGP formation in nuclear collisions [7], is more pronounced for multi-strange baryons. Several effects typical of heavy-ion phenomenology have been observed in high-multiplicity proton-proton (pp) collisions [8,9]. Yet, enhanced production of multi-strange particles has not been reported so far. Here we present the first observation of strangeness enhancement in high-multiplicity pp collisions. We find that the integrated yields of strange and multi-strange particles relative to pions increases significantly with the event charged-particle multiplicity. The measurements are in remarkable agreement with p-Pb collision results [10,11] indicating that the phenomenon is related to the final system created in the collision. In high-multiplicity events strangeness production reaches values similar to those observed in Pb-Pb collisions, where a QGP is formed.

Differential studies of inclusive J/

The production of J/

\psi

\psi

and

and

\psi

\psi(2S)

(2S) production at forward rapidity in Pb-Pb collisions at

was measured with the ALICE detector in Pb-Pb collisions at the LHC. The measurement was performed at forward rapidity (

\mathbf{\sqrt{{\textit s}_{_{NN}}}}

2.5<y<4

= 2.76 TeV

) down to zero transverse momentum (

Measurement of jet quenching with semi-inclusive hadron-jet distributions in central Pb-Pb collisions at sNN=2.76 TeV

p_{\rm T}