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Item type:Publication, Multiplicity dependence of (multi-)strange hadron production in proton-proton collisions at √s = 13 TeV(Springer, 2020-02-01)Abstract The production rates and the transverse momentum distribution of strange hadrons at mid-rapidity ( $$\left| y\right| < 0.5$$ y < 0.5 ) are measured in proton-proton collisions at $$\sqrt{s}$$ s = 13 TeV as a function of the charged particle multiplicity, using the ALICE detector at the LHC. The production rates of $$\mathrm{K}^{0}_{S}$$ K S 0 , $$\Lambda $$ Λ , $$\Xi $$ Ξ , and $$\Omega $$ Ω increase with the multiplicity faster than what is reported for inclusive charged particles. The increase is found to be more pronounced for hadrons with a larger strangeness content. Possible auto-correlations between the charged particles and the strange hadrons are evaluated by measuring the event-activity with charged particle multiplicity estimators covering different pseudorapidity regions. When comparing to lower energy results, the yields of strange hadrons are found to depend only on the mid-rapidity charged particle multiplicity. Several features of the data are reproduced qualitatively by general purpose QCD Monte Carlo models that take into account the effect of densely-packed QCD strings in high multiplicity collisions. However, none of the tested models reproduce the data quantitatively. This work corroborates and extends the ALICE findings on strangeness production in proton-proton collisions at 7 TeV. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Multiplicity dependence of π, K, and p production in pp collisions at √s=13 TeV(Institute for Ionics, 2020-08-01)Abstract This paper presents the measurements of $$\pi ^{\pm }$$ π± , $$\mathrm {K}^{\pm }$$ K± , $$\text {p}$$ p and $$\overline{\mathrm{p}} $$ p¯ transverse momentum ( $$p_{\text {T}}$$ pT ) spectra as a function of charged-particle multiplicity density in proton–proton (pp) collisions at $$\sqrt{s}\ =\ 13\ \text {TeV}$$ s=13TeV with the ALICE detector at the LHC. Such study allows us to isolate the center-of-mass energy dependence of light-flavour particle production. The measurements reported here cover a $$p_{\text {T}}$$ pT range from 0.1 to 20 $$\text {GeV}/c$$ GeV/c and are done in the rapidity interval $$|y|<0.5$$ |y|<0.5 . The $$p_{\text {T}}$$ pT -differential particle ratios exhibit an evolution with multiplicity, similar to that observed in pp collisions at $$\sqrt{s}\ =\ 7\ \text {TeV}$$ s=7TeV , which is qualitatively described by some of the hydrodynamical and pQCD-inspired models discussed in this paper. Furthermore, the $$p_{\text {T}}$$ pT -integrated hadron-to-pion yield ratios measured in pp collisions at two different center-of-mass energies are consistent when compared at similar multiplicities. This also extends to strange and multi-strange hadrons, suggesting that, at LHC energies, particle hadrochemistry scales with particle multiplicity the same way under different collision energies and colliding systems. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Measurement of electrons from heavy-flavour hadron decays as a function of multiplicity in p-Pb collisions at √sNN = 5.02 TeV(Springer, 2020-02-01)Abstract The multiplicity dependence of electron production from heavy-flavour hadron decays as a function of transverse momentum was measured in p-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5.02 TeV using the ALICE detector at the LHC. The measurement was performed in the centre-of-mass rapidity interval −1.07 < ycms< 0.14 and transverse momentum interval 2 < pT< 16 GeV/c. The multiplicity dependence of the production of electrons from heavy-flavour hadron decays was studied by comparing the pT spectra measured for different multiplicity classes with those measured in pp collisions (QpPb) and in peripheral p-Pb collisions (Qcp). The QpPb results obtained are consistent with unity within uncertainties in the measured pT interval and event classes. This indicates that heavy-flavour decay electron production is consistent with binary scaling and independent of the geometry of the collision system. Additionally, the results suggest that cold nuclear matter effects are negligible within uncertainties, in the production of heavy-flavour decay electrons at midrapidity in p-Pb collisions. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Studies of J/ψ production at forward rapidity in Pb–Pb collisions at √sNN = 5.02 TeV(Springer, 2020-02-01)Abstract The inclusive J/ψ production in Pb–Pb collisions at the center-of-mass energy per nucleon pair $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5.02 TeV, measured with the ALICE detector at the CERN LHC, is reported. The J/ψ meson is reconstructed via the dimuon decay channel at forward rapidity (2.5 < y < 4) down to zero transverse momentum. The suppression of the J/ψ yield in Pb–Pb collisions with respect to binary-scaled pp collisions is quantified by the nuclear modification factor (RAA). The RAA at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5.02 TeV is presented and compared with previous measurements at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 2.76 TeV as a function of the centrality of the collision, and of the J/ψ transverse momentum and rapidity. The inclusive J/ψ RAA shows a suppression increasing toward higher transverse momentum, with a steeper dependence for central collisions. The modification of the J/ψ average transverse momentum and average squared transverse momentum is also studied. Comparisons with the results of models based on a transport equation and on statistical hadronization are carried out. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, J/ψ elliptic and triangular flow in Pb-Pb collisions at √sNN = 5.02 TeV(Springer, 2020-10-01)Abstract The inclusive J/ψ elliptic (v2) and triangular (v3) flow coefficients measured at forward rapidity (2.5 < y < 4) and the v2 measured at midrapidity (|y| < 0.9) in Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5.02 TeV using the ALICE detector at the LHC are reported. The entire Pb-Pb data sample collected during Run 2 is employed, amounting to an integrated luminosity of 750 μb−1 at forward rapidity and 93 μb−1 at midrapidity. The results are obtained using the scalar product method and are reported as a function of transverse momentum pT and collision centrality. At midrapidity, the J/ψ v2 is in agreement with the forward rapidity measurement. The centrality averaged results indicate a positive J/ψ v3 with a significance of more than 5σ at forward rapidity in the pT range 2 < pT< 5 GeV/c. The forward rapidity v2, v3, and v3/v2 results at low and intermediate pT (pT ≲ 8 GeV/c) exhibit a mass hierarchy when compared to pions and D mesons, while converging into a species-independent curve at higher pT. At low and intermediate pT, the results could be interpreted in terms of a later thermalization of charm quarks compared to light quarks, while at high pT, path-length dependent effects seem to dominate. The J/ψ v2 measurements are further compared to a microscopic transport model calculation. Using a simplified extension of the quark scaling approach involving both light and charm quark flow components, it is shown that the D-meson vn measurements can be described based on those for charged pions and J/ψ flow. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Z-boson production in p-Pb collisions at √sNN = 8.16 TeV and Pb-Pb collisions at √sNN = 5.02 TeV(Springer, 2020-09-01)Abstract Measurement of Z-boson production in p-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ sNN = 8.16 TeV and Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ sNN = 5.02 TeV is reported. It is performed in the dimuon decay channel, through the detection of muons with pseudorapidity−4< ημ< −2.5 and transverse momentum $$ {p}_{\mathrm{T}}^{\mu } $$ pTμ >20 GeV/cin the laboratory frame. The invariant yield and nuclear modification factor are measured for opposite-sign dimuons with invariant mass 60< mμμ<120 GeV/c2and rapidity 2.5< $$ {y}_{\mathrm{cms}}^{\mu \mu} $$ ycmsμμ <4. They are presented as a function of rapidity and, for the Pb-Pb collisions, of centrality as well. The results are compared with theoretical calculations, both with and without nuclear modifications to the Parton Distribution Functions (PDFs). In p-Pb collisions the center-of-mass frame is boosted with respect to the laboratory frame, and the measurements cover the backward (−4.46< $$ {y}_{\mathrm{cms}}^{\mu \mu} $$ ycmsμμ < −2.96) and forward (2.03< $$ {y}_{\mathrm{cms}}^{\mu \mu} $$ ycmsμμ <3.53) rapidity regions. For the p-Pb collisions, the results are consistent within experimental and theoretical uncertainties with calculations that include both free-nucleon and nuclear-modified PDFs. For the Pb-Pb collisions, a 3.4σdeviation is seen in the integrated yield between the data and calculations based on the free-nucleon PDFs, while good agreement is found once nuclear modifications are considered. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, J/ψ production as a function of charged-particle multiplicity in p-Pb collisions at √sNN = 8.16 TeV(Springer, 2020-09-01)Abstract Inclusive J/ψ yields and average transverse momenta in p-Pb collisions at a center-of-mass energy per nucleon pair $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 8.16 TeV are measured as a function of the charged-particle pseudorapidity density with ALICE. The J/ψ mesons are reconstructed at forward (2.03 < ycms< 3.53) and backward (−4.46 < ycms< −2.96) center-of-mass rapidity in their dimuon decay channel while the charged-particle pseudorapidity density is measured around midrapidity. The J/ψ yields at forward and backward rapidity normalized to their respective average values increase with the normalized charged-particle pseudorapidity density, the former showing a weaker increase than the latter. The normalized average transverse momenta at forward and backward rapidity manifest a steady increase from low to high charged-particle pseudorapidity density with a saturation beyond the average value. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Measurement of nuclear effects on ψ(2S) production in p-Pb collisions at √sNN = 8.16 TeV(Springer, 2020-07-01)A bstract Inclusive ψ (2S) production is measured in p-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 8 . 16 TeV, using the ALICE detector at the CERN LHC. The production of ψ (2S) is studied at forward (2 . 03 < y cms < 3 . 53) and backward ( − 4 . 46 < y cms < − 2 . 96) centre-of-mass rapidity and for transverse momentum p T < 12 GeV/ c via the decay to muon pairs. In this paper, we report the integrated as well as the y cms - and p T -differential inclusive production cross sections. Nuclear effects on ψ (2S) production are studied via the determination of the nuclear modification factor that shows a strong suppression at both forward and backward centre-of-mass rapidities. Comparisons with corresponding results for inclusive J/ ψ show a similar suppression for the two states at forward rapidity (p-going direction), but a stronger suppression for ψ (2S) at backward rapidity (Pb-going direction). As a function of p T , no clear dependence of the nuclear modification factor is found. The relative size of nuclear effects on ψ (2S) production compared to J/ ψ is also studied via the double ratio of production cross sections [ σ ψ (2S) /σ J /ψ ]pPb / [ σ ψ (2S) /σ J /ψ ] pp between p-Pb and pp collisions. The results are compared with theoretical models that include various effects related to the initial and final state of the collision system and also with previous measurements at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5 . 02 TeV.1 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Pseudorapidity distributions of charged particles as a function of mid- and forward rapidity multiplicities in pp collisions at √s = 5.02, 7 and 13 TeV(Springer Science and Business Media Deutschland GmbH, 2021-07-01)The multiplicity dependence of the pseudorapidity density of charged particles in proton–proton (pp) collisions at centre-of-mass energies $$\sqrt{s}~=~5.02$$ s = 5.02 , 7 and 13 TeV measured by ALICE is reported. The analysis relies on track segments measured in the midrapidity range ( $$|\eta | < 1.5$$ | η | < 1.5 ). Results are presented for inelastic events having at least one charged particle produced in the pseudorapidity interval $$|\eta |<1$$ | η | < 1 . The multiplicity dependence of the pseudorapidity density of charged particles is measured with mid- and forward rapidity multiplicity estimators, the latter being less affected by autocorrelations. A detailed comparison with predictions from the PYTHIA 8 and EPOS LHC event generators is also presented. The results can be used to constrain models for particle production as a function of multiplicity in pp collisions. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Centrality dependence of J/ψ and ψ(2S) production and nuclear modification in p-Pb collisions at √sNN = 8.16 TeV(Springer Science and Business Media Deutschland GmbH, 2021-02-01)The inclusive production of the J/ψ and ψ(2S) charmonium states is studied as a function of centrality in p-Pb collisions at a centre-of-mass energy per nucleon pair $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 8.16 TeV at the LHC. The measurement is performed in the dimuon decay channel with the ALICE apparatus in the centre-of-mass rapidity intervals −4.46 < ycms< −2.96 (Pb-going direction) and 2.03 < ycms< 3.53 (p-going direction), down to zero transverse momentum (pT). The J/ψ and ψ(2S) production cross sections are evaluated as a function of the collision centrality, estimated through the energy deposited in the zero degree calorimeter located in the Pb-going direction. The pT-differential J/ψ production cross section is measured at backward and forward rapidity for several centrality classes, together with the corresponding average 〈pT〉 and $$ \left\langle {p}_{\mathrm{T}}^2\right\rangle $$ p T 2 values. The nuclear effects affecting the production of both charmonium states are studied using the nuclear modification factor. In the p-going direction, a suppression of the production of both charmonium states is observed, which seems to increase from peripheral to central collisions. In the Pb-going direction, however, the centrality dependence is different for the two states: the nuclear modification factor of the J/ψ increases from below unity in peripheral collisions to above unity in central collisions, while for the ψ(2S) it stays below or consistent with unity for all centralities with no significant centrality dependence. The results are compared with measurements in p-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5.02 TeV and no significant dependence on the energy of the collision is observed. Finally, the results are compared with theoretical models implementing various nuclear matter effects.