J/psi production as a function of charged-particle multiplicity in p-Pb collisions at root s(NN)=8.16 TeV

Inclusive J/psi yields and average transverse momenta in p-Pb collisions at a center-of-mass energy per nucleon pairs root s(NN) = 8.16 TeV are measured as a function of the charged-particle pseudorapidity density with ALICE. The J/psi mesons are reconstructed at forward (2.03<y(cms)Peer reviewe

Production of K*(892)0 and phi(1020) in pp and Pb-Pb collisions at root s(NN)=5.02 TeV

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Lambda K femtoscopy in Pb-Pb collisions at root s(NN)=2.76 TeV

The first measurements of the scattering parameters of Lambda K pairs in all three charge combinations (Lambda K+, Lambda K-, and Lambda K-S(0)) are presented. The results are achieved through a femtoscopic analysis of Lambda K correlations in Pb-Pb collisions at root s(NN) = 2.76 TeV recorded by ALICE at the Large Hadron Collider. The femtoscopic correlations result from strong final-state interactions and are fit with a parametrization allowing for both the characterization of the pair emission source and the measurement of the scattering parameters for the particle pairs. Extensive studies with the THERMINATOR 2 event generator provide a good description of the nonfemtoscopic background, which results mainly from collective effects, with unprecedented precision. Furthermore, together with HIJING simulations, this model is used to account for contributions from residual correlations induced by feed-down from particle decays. The extracted scattering parameters indicate that the strong force is repulsive in the Lambda K+ interaction and attractive in the Lambda K- interaction. The data hint that the Lambda K-S(0) interaction is attractive; however, the uncertainty of the result does not permit such a decisive conclusion. The results suggest an effect arising either from different quark-antiquark interactions between the pairs (s (s) over bar in Lambda K+ and u (u) over bar in Lambda K-) or from different net strangeness for each system (S = 0 for Lambda K+, and S = -2 for Lambda K-). Finally, the Lambda K systems exhibit source radii larger than expected from extrapolation from identical particle femtoscopic studies. This effect is interpreted as resulting from the separation in space-time of the single-particle Lambda and K source distributions.Peer reviewe

Experimental Evidence for an Attractive p-phi Interaction

This Letter presents the first experimental evidence of the attractive strong interaction between a proton and a phi meson. The result is obtained from two-particle correlations of combined p-phi circle plus (p) over bar-phi pairs measured in high-multiplicity pp collisions at root s = 13 TeV by the ALICE Collaboration. The spin-averaged scattering length and effective range of the p-phi interaction are extracted from the fully corrected correlation function employing the Lednicky-Lyuboshits approach. In particular, the imaginary part of the scattering length vanishes within uncertainties, indicating that inelastic processes do not play a prominent role for the p-phi interaction. These data demonstrate that the interaction is dominated by elastic p-phi scattering. Furthermore, an analysis employing phenomenological Gaussian-and Yukawa-type potentials is conducted. Under the assumption of the latter, the N-phi coupling constant is found to be g(N-phi) = 0.14 +/- 0.03(stat) +/- 0.02(syst). This work provides valuable experimental input to accomplish a self-consistent description of the N-phi interaction, which is particularly relevant for the more fundamental studies on partial restoration of chiral symmetry in nuclear medium.Peer reviewe

Elliptic Flow of Electrons from Beauty-Hadron Decays in Pb-Pb Collisions at root s(NN)=5.02 TeV

The elliptic flow of electrons from beauty hadron decays at midrapidity (vertical bar y vertical bar < 0.8) is measured in Pb-Pb collisions at root s(NN) = 5.02 TeV with the ALICE detector at the LHC. The azimuthal distribution of the particles produced in the collisions can be parametrized with a Fourier expansion, in which the second harmonic coefficient represents the elliptic flow, v(2). The v(2) coefficient of electrons from beauty hadron decays is measured for the first time in the transverse momentum (p(T)) range 1.3- 6 GeV/c in the centrality class 30%-50%. The measurement of electrons from beauty-hadron decays exploits their larger mean proper decay length c tau approximate to 500 mu m compared to that of charm hadrons and most of the other background sources. The v(2) of electrons from beauty hadron decays at midrapidity is found to be positive with a significance of 3.75 sigma. The results provide insights into the degree of thermalization of beauty quarks in the medium. A model assuming full thermalization of beauty quarks is strongly disfavored by the measurement at high p(T), but is in agreement with the results at low p(T). Transport models including substantial interactions of beauty quarks with an expanding strongly interacting medium describe the measurement within uncertainties.Peer reviewe