HAL (Le Centre pour la Communication Scientifique Directe), Nov 3, 2021
The production of K * (892) 0 and φ (1020) resonances has been measured in p-Pb collisions at √ s... more The production of K * (892) 0 and φ (1020) resonances has been measured in p-Pb collisions at √ s NN = 8.16 TeV using the ALICE detector. Resonances are reconstructed via their hadronic decay channels in the rapidity interval −0.5 < y < 0 and the transverse momentum spectra are measured for various multiplicity classes up to p T = 20 GeV/c for K * (892) 0 and p T = 16 GeV/c for φ (1020). The p T-integrated yields and mean transverse momenta are reported and compared with previous results in pp, p-Pb and Pb-Pb collisions. The x T scaling for K * (892) 0 and φ (1020) resonance production is newly tested in p-Pb collisions and found to hold in the high-p T region at Large Hadron Collider energies. The nuclear modification factors (R pPb) as a function of p T for K * 0 and φ at √ s NN = 8.16 TeV are presented along with the new R pPb measurements of K * 0 , φ , Ξ, and Ω at √ s NN = 5.02 TeV. At intermediate p T (2-8 GeV/c), R pPb of Ξ, Ω show a Cronin-like enhancement, while K * 0 and φ show no or little nuclear modification. At high p T (> 8 GeV/c), the R pPb values of all hadrons are consistent with unity within uncertainties. The R pPb of K * (892) 0 and φ (1020) at √ s NN = 8.16 and 5.02 TeV show no significant energy dependence.
First measurements of balance functions (BFs) of all combinations of identified charged hadron (π... more First measurements of balance functions (BFs) of all combinations of identified charged hadron (π, K, p) pairs in Pb-Pb collisions at √ s NN = 2.76 TeV recorded by the ALICE detector are presented. The BF measurements are carried out as two-dimensional differential correlators versus the relative rapidity (∆y) and azimuthal angle (∆ϕ) of hadron pairs, and studied as a function of collision centrality. The ∆ϕ dependence of BFs is expected to be sensitive to the light quark diffusivity in the quark-gluon plasma. While the BF azimuthal widths of all pairs substantially decrease from peripheral to central collisions, the longitudinal widths exhibit mixed behaviors: BFs of ππ and cross-species pairs narrow significantly in more central collisions, whereas those of KK and pp are found to be independent of collision centrality. This dichotomy is qualitatively consistent with the presence of strong radial flow effects and the existence of two stages of quark production in relativistic heavy-ion collisions. Finally, the first measurements of the collision centrality evolution of BF integrals are presented, with the observation that charge balancing fractions are nearly independent of collision centrality in Pb-Pb collisions. Overall, the results presented provide new and challenging constraints for theoretical models of hadron production and transport in relativistic heavy-ion collisions.
The production of J/ψ is measured as a function of charged-particle multiplicity at forward rapid... more The production of J/ψ is measured as a function of charged-particle multiplicity at forward rapidity in proton-proton (pp) collisions at center-of-mass energies $$ \sqrt{s} $$ s = 5.02 and 13 TeV. The J/ψ mesons are reconstructed via their decay into dimuons in the rapidity interval (2.5 < y < 4.0), whereas the charged-particle multiplicity density (dNch/dη) is measured at midrapidity (|η| < 1). The production rate as a function of multiplicity is reported as the ratio of the yield in a given multiplicity interval to the multiplicity-integrated one. This observable shows a linear increase with charged-particle multiplicity normalized to the corresponding average value for inelastic events (dNch/dη/〈dNch/dη〉), at both the colliding energies. Measurements are compared with available ALICE results at midrapidity and theoretical model calculations. First measurement of the mean transverse momentum (〈pT〉) of J/ψ in pp collisions exhibits an increasing trend as a function of dNch...
A measurement of inclusive, prompt, and non-prompt J/ψ production in p−Pb collisions at a nucleon... more A measurement of inclusive, prompt, and non-prompt J/ψ production in p−Pb collisions at a nucleonnucleon centre-of-mass energy √ s NN = 5.02 TeV is presented. The inclusive J/ψ mesons are reconstructed in the dielectron decay channel at midrapidity down to a transverse momentum p T = 0. The inclusive J/ψ nuclear modification factor R pPb is calculated by comparing the new results in p−Pb collisions to a recently measured proton−proton reference at the same centre-of-mass energy. Nonprompt J/ψ mesons, which originate from the decay of beauty hadrons, are separated from promptly produced J/ψ on a statistical basis for p T larger than 1.0 GeV/c. These results are based on the data sample collected by the ALICE detector during the 2016 LHC p−Pb run, corresponding to an integrated luminosity L int = 292 ± 11 µb −1 , which is six times larger than the previous publications. The total uncertainty on the p T-integrated inclusive J/ψ and non-prompt J/ψ cross section are reduced by a factor 1.7 and 2.2, respectively. The measured cross sections and R pPb are compared with theoretical models that include various combinations of cold nuclear matter effects. From the non-prompt J/ψ production cross section, the bb production cross section at midrapidity, dσ bb /dy, and the total cross section extrapolated over full phase space, σ bb , are derived.
Inclusive $\Upsilon$ production in p-Pb interactions is studied at the centre-of-mass energy per ... more Inclusive $\Upsilon$ production in p-Pb interactions is studied at the centre-of-mass energy per nucleon-nucleon collision $\sqrt{s_{\rm{NN}}}$ = 8.16 TeV with the ALICE detector at the CERN LHC. The measurement is performed reconstructing bottomonium resonances via their dimuon decay channel, in the centre-of-mass rapidity intervals $2.03<y_{\rm{cms}}<3.53$ and $-4.46<y_{\rm{cms}}<-2.96$, down to zero transverse momentum. In this work, results on the inclusive $\Upsilon(1\rm{S})$ production cross section as a function of rapidity and transverse momentum are presented. The corresponding nuclear modification factor shows a suppression of the $\Upsilon(1\rm{S})$ yields with respect to pp collisions, both at forward and backward rapidity. This suppression is stronger in the low transverse momentum region and shows no significant dependence on the centrality of the interactions. The inclusive $\Upsilon(2\rm{S})$ nuclear modification factor is also evaluated, suggesting a sup...
This document was prepared by the community that is active in Italy, within INFN (Istituto Nazion... more This document was prepared by the community that is active in Italy, within INFN (Istituto Nazionale di Fisica Nucleare), in the field of ultra-relativistic heavy-ion collisions. The experimental study of the phase diagram of strongly-interacting matter and of the Quark-Gluon Plasma (QGP) deconfined state will proceed, in the next 10-15 years, along two directions: the high-energy regime at RHIC and at the LHC, and the low-energy regime at FAIR, NICA, SPS and RHIC. The Italian community is strongly involved in the present and future programme of the ALICE experiment, the upgrade of which will open, in the 2020s, a new phase of high-precision characterisation of the QGP properties at the LHC. As a complement of this main activity, there is a growing interest in a possible future experiment at the SPS, which would target the search for the onset of deconfinement using dimuon measurements. On a longer timescale, the community looks with interest at the ongoing studies and discussions o...
The inclusive J/ψ elliptic (v2) and triangular (v3) flow coefficients measured at forward rapidit... more 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 int...
We report measurements of the inclusive J/ψ yield and average transverse momentum as a function o... more We report measurements of the inclusive J/ψ yield and average transverse momentum as a function of charged-particle pseudorapidity density dN ch /dη in p-Pb collisions at √ s NN = 5.02 TeV with ALICE at the LHC. The observables are normalised to their corresponding averages in non-single diffractive events. An increase of the normalised J/ψ yield with normalised dN ch /dη, measured at mid-rapidity, is observed at mid-rapidity and backward rapidity. At forward rapidity, a saturation of the relative yield is observed for high charged-particle multiplicities. The normalised average transverse momentum at forward and backward rapidities increases with multiplicity at low multiplicities and saturates beyond moderate multiplicities. In addition, the forward-to-backward nuclear modification factor ratio is also reported, showing an increasing suppression of J/ψ production at forward rapidity with respect to backward rapidity for increasing charged-particle multiplicity.
The inclusive J/ψ production in Pb–Pb collisions at the center-of-mass energy per nucleon pair $$... more The inclusive J/ψ production in Pb–Pb collisions at the center-of-mass energy per nucleon pair $$ \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....
The azimuthal anisotropy coefficient v_{2} of prompt D^{0}, D^{+}, D^{*+}, and D_{s}^{+} mesons w... more The azimuthal anisotropy coefficient v_{2} of prompt D^{0}, D^{+}, D^{*+}, and D_{s}^{+} mesons was measured in midcentral (30%-50% centrality class) Pb-Pb collisions at a center-of-mass energy per nucleon pair sqrt[s_{NN}]=5.02 TeV, with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decays at midrapidity, |y|<0.8, in the transverse momentum interval 1<p_{T}<24 GeV/c. The measured D-meson v_{2} has similar values as that of charged pions. The D_{s}^{+} v_{2}, measured for the first time, is found to be compatible with that of nonstrange D mesons. The measurements are compared with theoretical calculations of charm-quark transport in a hydrodynamically expanding medium and have the potential to constrain medium parameters.
According to a conjecture, all 5d SCFTs should be obtainable by rankpreserving RG flows of 6d SCF... more According to a conjecture, all 5d SCFTs should be obtainable by rankpreserving RG flows of 6d SCFTs compactified on a circle possibly twisted by a background for the discrete global symmetries around the circle. For a 6d SCFT admitting an F-theory construction, its untwisted compactification admits a dual M-theory description in terms of a "parent" Calabi-Yau threefold which captures the Coulomb branch of the compactified 6d SCFT. The RG flows to 5d SCFTs can then be identified with a sequence of flop transitions and blowdowns of the parent Calabi-Yau leading to "descendant" Calabi-Yau threefolds which describe the Coulomb branches of the resulting 5d SCFTs. An explicit description of parent Calabi-Yaus is known for untwisted compactifications of rank one 6d SCFTs. In this paper, we provide a description of parent Calabi-Yaus for untwisted compactifications of arbitrary rank 6d SCFTs. Since 6d SCFTs of arbitrary rank can be viewed as being constructed out of rank one SCFTs, we accomplish the extension to arbitrary rank by identifying a prescription for gluing together Calabi-Yaus associated to rank one 6d SCFTs.
The production of muons from heavy-flavour hadron decays in p-Pb collisions at √ s NN = 5.02 TeV ... more The production of muons from heavy-flavour hadron decays in p-Pb collisions at √ s NN = 5.02 TeV was studied for 2 < p T < 16 GeV/c with the ALICE detector at the CERN LHC. The measurement was performed at forward (p-going direction) and backward (Pb-going direction) rapidity, in the ranges of rapidity in the centre-of-mass system (cms) 2.03 < y cms < 3.53 and −4.46 < y cms < −2.96, respectively. The production cross sections and nuclear modification factors are presented as a function of transverse momentum (p T). At forward rapidity, the nuclear modification factor is compatible with unity while at backward rapidity, in the interval 2.5 < p T < 3.5 GeV/c, it is above unity by more than 2σ. The ratio of the forward-to-backward production cross sections is also measured in the overlapping interval 2.96 < |y cms | < 3.53 and is smaller than unity by 3.7σ in 2.5 < p T < 3.5 GeV/c. The data are described by model calculations including cold nuclear matter effects.
We have performed the first measurement of the coherent ψ(2S) photo-production cross section in u... more We have performed the first measurement of the coherent ψ(2S) photo-production cross section in ultraperipheral Pb-Pb collisions at the LHC. This charmonium excited state is reconstructed via the ψ(2S) → l + l − and ψ(2S) → J/ψπ + π − decays, where the J/ψ decays into two leptons. The analysis is based on an event sample corresponding to an integrated luminosity of about 22 μb −1. The cross section for coherent ψ(2S) production in the rapidity interval −0.9 < y < 0.9 is dσ coh ψ(2S) /dy = 0.83 ± 0.19 stat + syst mb. The ψ(2S) to J/ψ coherent cross section ratio is 0.34 +0.08 −0.07 (stat + syst). The obtained results are compared to predictions from theoretical models.
The production of J/ψ mesons is studied in proton-lead collisions at the centre-of-mass energy pe... more The production of J/ψ mesons is studied in proton-lead collisions at the centre-of-mass energy per nucleon pair √ s N N = 8.16 TeV with the LHCb detector at the LHC. The double differential crosssections of prompt and nonprompt J/ψ production are measured as a function of the J/ψ transverse momentum and rapidity in the nucleon-nucleon centre-of-mass frame. Forward-to-backward ratios and nuclear modification factors are determined. The results are compared with theoretical calculations based on collinear factorisation using nuclear parton distribution functions, on the colour glass condensate or on coherent energy loss models.
We report on the first measurement of an excess in the yield of J/ψ at very low transverse moment... more We report on the first measurement of an excess in the yield of J/ψ at very low transverse momentum (p_{T}<0.3 GeV/c) in peripheral hadronic Pb-Pb collisions at sqrt[s_{NN}]=2.76 TeV, performed by ALICE at the CERN LHC. Remarkably, the measured nuclear modification factor of J/ψ in the rapidity range 2.5<y<4 reaches about 7 (2) in the p_{T} range 0-0.3 GeV/c in the 70%-90% (50%-70%) centrality class. The J/ψ production cross section associated with the observed excess is obtained under the hypothesis that coherent photoproduction of J/ψ is the underlying physics mechanism. If confirmed, the observation of J/ψ coherent photoproduction in Pb-Pb collisions at impact parameters smaller than twice the nuclear radius opens new theoretical and experimental challenges and opportunities. In particular, coherent photoproduction accompanying hadronic collisions may provide insight into the dynamics of photoproduction and nuclear reactions, as well as become a novel probe of the qua...
The European physical journal. C, Particles and fields
The production of K[Formula: see text](892)[Formula: see text] and [Formula: see text](1020) meso... more The production of K[Formula: see text](892)[Formula: see text] and [Formula: see text](1020) mesons has been measured in p-Pb collisions at [Formula: see text][Formula: see text] 5.02 TeV. K[Formula: see text] and [Formula: see text] are reconstructed via their decay into charged hadrons with the ALICE detector in the rapidity range [Formula: see text]. The transverse momentum spectra, measured as a function of the multiplicity, have a p[Formula: see text] range from 0 to 15 GeV/c for K[Formula: see text] and from 0.3 to 21 GeV/c for [Formula: see text]. Integrated yields, mean transverse momenta and particle ratios are reported and compared with results in pp collisions at [Formula: see text][Formula: see text] 7 TeV and Pb-Pb collisions at [Formula: see text][Formula: see text] 2.76 TeV. In Pb-Pb and p-Pb collisions, K[Formula: see text] and [Formula: see text] probe the hadronic phase of the system and contribute to the study of particle formation mechanisms by comparison with ot...
The nuclear modification factor, R AA , of the prompt charmed mesons D 0 , D + and D * + , and th... more The nuclear modification factor, R AA , of the prompt charmed mesons D 0 , D + and D * + , and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at a centre-of-mass energy √ s NN = 2.76 TeV in two transverse momentum intervals, 5 < p T < 8 GeV/c and 8 < p T < 16 GeV/c, and in six collision centrality classes. The R AA shows a maximum suppression of a factor of 5-6 in the 10% most central collisions. The suppression and its centrality dependence are compatible within uncertainties with those of charged pions. A comparison with the R AA of non-prompt J/ψ from B meson decays, measured by the CMS Collaboration, hints at a larger suppression of D mesons in the most central collisions.
HAL (Le Centre pour la Communication Scientifique Directe), Nov 3, 2021
The production of K * (892) 0 and φ (1020) resonances has been measured in p-Pb collisions at √ s... more The production of K * (892) 0 and φ (1020) resonances has been measured in p-Pb collisions at √ s NN = 8.16 TeV using the ALICE detector. Resonances are reconstructed via their hadronic decay channels in the rapidity interval −0.5 < y < 0 and the transverse momentum spectra are measured for various multiplicity classes up to p T = 20 GeV/c for K * (892) 0 and p T = 16 GeV/c for φ (1020). The p T-integrated yields and mean transverse momenta are reported and compared with previous results in pp, p-Pb and Pb-Pb collisions. The x T scaling for K * (892) 0 and φ (1020) resonance production is newly tested in p-Pb collisions and found to hold in the high-p T region at Large Hadron Collider energies. The nuclear modification factors (R pPb) as a function of p T for K * 0 and φ at √ s NN = 8.16 TeV are presented along with the new R pPb measurements of K * 0 , φ , Ξ, and Ω at √ s NN = 5.02 TeV. At intermediate p T (2-8 GeV/c), R pPb of Ξ, Ω show a Cronin-like enhancement, while K * 0 and φ show no or little nuclear modification. At high p T (> 8 GeV/c), the R pPb values of all hadrons are consistent with unity within uncertainties. The R pPb of K * (892) 0 and φ (1020) at √ s NN = 8.16 and 5.02 TeV show no significant energy dependence.
First measurements of balance functions (BFs) of all combinations of identified charged hadron (π... more First measurements of balance functions (BFs) of all combinations of identified charged hadron (π, K, p) pairs in Pb-Pb collisions at √ s NN = 2.76 TeV recorded by the ALICE detector are presented. The BF measurements are carried out as two-dimensional differential correlators versus the relative rapidity (∆y) and azimuthal angle (∆ϕ) of hadron pairs, and studied as a function of collision centrality. The ∆ϕ dependence of BFs is expected to be sensitive to the light quark diffusivity in the quark-gluon plasma. While the BF azimuthal widths of all pairs substantially decrease from peripheral to central collisions, the longitudinal widths exhibit mixed behaviors: BFs of ππ and cross-species pairs narrow significantly in more central collisions, whereas those of KK and pp are found to be independent of collision centrality. This dichotomy is qualitatively consistent with the presence of strong radial flow effects and the existence of two stages of quark production in relativistic heavy-ion collisions. Finally, the first measurements of the collision centrality evolution of BF integrals are presented, with the observation that charge balancing fractions are nearly independent of collision centrality in Pb-Pb collisions. Overall, the results presented provide new and challenging constraints for theoretical models of hadron production and transport in relativistic heavy-ion collisions.
The production of J/ψ is measured as a function of charged-particle multiplicity at forward rapid... more The production of J/ψ is measured as a function of charged-particle multiplicity at forward rapidity in proton-proton (pp) collisions at center-of-mass energies $$ \sqrt{s} $$ s = 5.02 and 13 TeV. The J/ψ mesons are reconstructed via their decay into dimuons in the rapidity interval (2.5 < y < 4.0), whereas the charged-particle multiplicity density (dNch/dη) is measured at midrapidity (|η| < 1). The production rate as a function of multiplicity is reported as the ratio of the yield in a given multiplicity interval to the multiplicity-integrated one. This observable shows a linear increase with charged-particle multiplicity normalized to the corresponding average value for inelastic events (dNch/dη/〈dNch/dη〉), at both the colliding energies. Measurements are compared with available ALICE results at midrapidity and theoretical model calculations. First measurement of the mean transverse momentum (〈pT〉) of J/ψ in pp collisions exhibits an increasing trend as a function of dNch...
A measurement of inclusive, prompt, and non-prompt J/ψ production in p−Pb collisions at a nucleon... more A measurement of inclusive, prompt, and non-prompt J/ψ production in p−Pb collisions at a nucleonnucleon centre-of-mass energy √ s NN = 5.02 TeV is presented. The inclusive J/ψ mesons are reconstructed in the dielectron decay channel at midrapidity down to a transverse momentum p T = 0. The inclusive J/ψ nuclear modification factor R pPb is calculated by comparing the new results in p−Pb collisions to a recently measured proton−proton reference at the same centre-of-mass energy. Nonprompt J/ψ mesons, which originate from the decay of beauty hadrons, are separated from promptly produced J/ψ on a statistical basis for p T larger than 1.0 GeV/c. These results are based on the data sample collected by the ALICE detector during the 2016 LHC p−Pb run, corresponding to an integrated luminosity L int = 292 ± 11 µb −1 , which is six times larger than the previous publications. The total uncertainty on the p T-integrated inclusive J/ψ and non-prompt J/ψ cross section are reduced by a factor 1.7 and 2.2, respectively. The measured cross sections and R pPb are compared with theoretical models that include various combinations of cold nuclear matter effects. From the non-prompt J/ψ production cross section, the bb production cross section at midrapidity, dσ bb /dy, and the total cross section extrapolated over full phase space, σ bb , are derived.
Inclusive $\Upsilon$ production in p-Pb interactions is studied at the centre-of-mass energy per ... more Inclusive $\Upsilon$ production in p-Pb interactions is studied at the centre-of-mass energy per nucleon-nucleon collision $\sqrt{s_{\rm{NN}}}$ = 8.16 TeV with the ALICE detector at the CERN LHC. The measurement is performed reconstructing bottomonium resonances via their dimuon decay channel, in the centre-of-mass rapidity intervals $2.03<y_{\rm{cms}}<3.53$ and $-4.46<y_{\rm{cms}}<-2.96$, down to zero transverse momentum. In this work, results on the inclusive $\Upsilon(1\rm{S})$ production cross section as a function of rapidity and transverse momentum are presented. The corresponding nuclear modification factor shows a suppression of the $\Upsilon(1\rm{S})$ yields with respect to pp collisions, both at forward and backward rapidity. This suppression is stronger in the low transverse momentum region and shows no significant dependence on the centrality of the interactions. The inclusive $\Upsilon(2\rm{S})$ nuclear modification factor is also evaluated, suggesting a sup...
This document was prepared by the community that is active in Italy, within INFN (Istituto Nazion... more This document was prepared by the community that is active in Italy, within INFN (Istituto Nazionale di Fisica Nucleare), in the field of ultra-relativistic heavy-ion collisions. The experimental study of the phase diagram of strongly-interacting matter and of the Quark-Gluon Plasma (QGP) deconfined state will proceed, in the next 10-15 years, along two directions: the high-energy regime at RHIC and at the LHC, and the low-energy regime at FAIR, NICA, SPS and RHIC. The Italian community is strongly involved in the present and future programme of the ALICE experiment, the upgrade of which will open, in the 2020s, a new phase of high-precision characterisation of the QGP properties at the LHC. As a complement of this main activity, there is a growing interest in a possible future experiment at the SPS, which would target the search for the onset of deconfinement using dimuon measurements. On a longer timescale, the community looks with interest at the ongoing studies and discussions o...
The inclusive J/ψ elliptic (v2) and triangular (v3) flow coefficients measured at forward rapidit... more 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}}} $$ s NN = 5.02 TeV using the ALICE detector at the LHC are reported. The entire Pb-Pb data sample collected during Run 2 is employed, amounting to an integrated luminosity of 750 μb−1 at forward rapidity and 93 μb−1 at midrapidity. The results are obtained using the scalar product method and are reported as a function of transverse momentum pT and collision centrality. At midrapidity, the J/ψ v2 is in agreement with the forward rapidity measurement. The centrality averaged results indicate a positive J/ψ v3 with a significance of more than 5σ at forward rapidity in the pT range 2 < pT< 5 GeV/c. The forward rapidity v2, v3, and v3/v2 results at low and intermediate pT (pT ≲ 8 GeV/c) exhibit a mass hierarchy when compared to pions and D mesons, while converging int...
We report measurements of the inclusive J/ψ yield and average transverse momentum as a function o... more We report measurements of the inclusive J/ψ yield and average transverse momentum as a function of charged-particle pseudorapidity density dN ch /dη in p-Pb collisions at √ s NN = 5.02 TeV with ALICE at the LHC. The observables are normalised to their corresponding averages in non-single diffractive events. An increase of the normalised J/ψ yield with normalised dN ch /dη, measured at mid-rapidity, is observed at mid-rapidity and backward rapidity. At forward rapidity, a saturation of the relative yield is observed for high charged-particle multiplicities. The normalised average transverse momentum at forward and backward rapidities increases with multiplicity at low multiplicities and saturates beyond moderate multiplicities. In addition, the forward-to-backward nuclear modification factor ratio is also reported, showing an increasing suppression of J/ψ production at forward rapidity with respect to backward rapidity for increasing charged-particle multiplicity.
The inclusive J/ψ production in Pb–Pb collisions at the center-of-mass energy per nucleon pair $$... more 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....
The azimuthal anisotropy coefficient v_{2} of prompt D^{0}, D^{+}, D^{*+}, and D_{s}^{+} mesons w... more The azimuthal anisotropy coefficient v_{2} of prompt D^{0}, D^{+}, D^{*+}, and D_{s}^{+} mesons was measured in midcentral (30%-50% centrality class) Pb-Pb collisions at a center-of-mass energy per nucleon pair sqrt[s_{NN}]=5.02 TeV, with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decays at midrapidity, |y|<0.8, in the transverse momentum interval 1<p_{T}<24 GeV/c. The measured D-meson v_{2} has similar values as that of charged pions. The D_{s}^{+} v_{2}, measured for the first time, is found to be compatible with that of nonstrange D mesons. The measurements are compared with theoretical calculations of charm-quark transport in a hydrodynamically expanding medium and have the potential to constrain medium parameters.
According to a conjecture, all 5d SCFTs should be obtainable by rankpreserving RG flows of 6d SCF... more According to a conjecture, all 5d SCFTs should be obtainable by rankpreserving RG flows of 6d SCFTs compactified on a circle possibly twisted by a background for the discrete global symmetries around the circle. For a 6d SCFT admitting an F-theory construction, its untwisted compactification admits a dual M-theory description in terms of a "parent" Calabi-Yau threefold which captures the Coulomb branch of the compactified 6d SCFT. The RG flows to 5d SCFTs can then be identified with a sequence of flop transitions and blowdowns of the parent Calabi-Yau leading to "descendant" Calabi-Yau threefolds which describe the Coulomb branches of the resulting 5d SCFTs. An explicit description of parent Calabi-Yaus is known for untwisted compactifications of rank one 6d SCFTs. In this paper, we provide a description of parent Calabi-Yaus for untwisted compactifications of arbitrary rank 6d SCFTs. Since 6d SCFTs of arbitrary rank can be viewed as being constructed out of rank one SCFTs, we accomplish the extension to arbitrary rank by identifying a prescription for gluing together Calabi-Yaus associated to rank one 6d SCFTs.
The production of muons from heavy-flavour hadron decays in p-Pb collisions at √ s NN = 5.02 TeV ... more The production of muons from heavy-flavour hadron decays in p-Pb collisions at √ s NN = 5.02 TeV was studied for 2 < p T < 16 GeV/c with the ALICE detector at the CERN LHC. The measurement was performed at forward (p-going direction) and backward (Pb-going direction) rapidity, in the ranges of rapidity in the centre-of-mass system (cms) 2.03 < y cms < 3.53 and −4.46 < y cms < −2.96, respectively. The production cross sections and nuclear modification factors are presented as a function of transverse momentum (p T). At forward rapidity, the nuclear modification factor is compatible with unity while at backward rapidity, in the interval 2.5 < p T < 3.5 GeV/c, it is above unity by more than 2σ. The ratio of the forward-to-backward production cross sections is also measured in the overlapping interval 2.96 < |y cms | < 3.53 and is smaller than unity by 3.7σ in 2.5 < p T < 3.5 GeV/c. The data are described by model calculations including cold nuclear matter effects.
We have performed the first measurement of the coherent ψ(2S) photo-production cross section in u... more We have performed the first measurement of the coherent ψ(2S) photo-production cross section in ultraperipheral Pb-Pb collisions at the LHC. This charmonium excited state is reconstructed via the ψ(2S) → l + l − and ψ(2S) → J/ψπ + π − decays, where the J/ψ decays into two leptons. The analysis is based on an event sample corresponding to an integrated luminosity of about 22 μb −1. The cross section for coherent ψ(2S) production in the rapidity interval −0.9 < y < 0.9 is dσ coh ψ(2S) /dy = 0.83 ± 0.19 stat + syst mb. The ψ(2S) to J/ψ coherent cross section ratio is 0.34 +0.08 −0.07 (stat + syst). The obtained results are compared to predictions from theoretical models.
The production of J/ψ mesons is studied in proton-lead collisions at the centre-of-mass energy pe... more The production of J/ψ mesons is studied in proton-lead collisions at the centre-of-mass energy per nucleon pair √ s N N = 8.16 TeV with the LHCb detector at the LHC. The double differential crosssections of prompt and nonprompt J/ψ production are measured as a function of the J/ψ transverse momentum and rapidity in the nucleon-nucleon centre-of-mass frame. Forward-to-backward ratios and nuclear modification factors are determined. The results are compared with theoretical calculations based on collinear factorisation using nuclear parton distribution functions, on the colour glass condensate or on coherent energy loss models.
We report on the first measurement of an excess in the yield of J/ψ at very low transverse moment... more We report on the first measurement of an excess in the yield of J/ψ at very low transverse momentum (p_{T}<0.3 GeV/c) in peripheral hadronic Pb-Pb collisions at sqrt[s_{NN}]=2.76 TeV, performed by ALICE at the CERN LHC. Remarkably, the measured nuclear modification factor of J/ψ in the rapidity range 2.5<y<4 reaches about 7 (2) in the p_{T} range 0-0.3 GeV/c in the 70%-90% (50%-70%) centrality class. The J/ψ production cross section associated with the observed excess is obtained under the hypothesis that coherent photoproduction of J/ψ is the underlying physics mechanism. If confirmed, the observation of J/ψ coherent photoproduction in Pb-Pb collisions at impact parameters smaller than twice the nuclear radius opens new theoretical and experimental challenges and opportunities. In particular, coherent photoproduction accompanying hadronic collisions may provide insight into the dynamics of photoproduction and nuclear reactions, as well as become a novel probe of the qua...
The European physical journal. C, Particles and fields
The production of K[Formula: see text](892)[Formula: see text] and [Formula: see text](1020) meso... more The production of K[Formula: see text](892)[Formula: see text] and [Formula: see text](1020) mesons has been measured in p-Pb collisions at [Formula: see text][Formula: see text] 5.02 TeV. K[Formula: see text] and [Formula: see text] are reconstructed via their decay into charged hadrons with the ALICE detector in the rapidity range [Formula: see text]. The transverse momentum spectra, measured as a function of the multiplicity, have a p[Formula: see text] range from 0 to 15 GeV/c for K[Formula: see text] and from 0.3 to 21 GeV/c for [Formula: see text]. Integrated yields, mean transverse momenta and particle ratios are reported and compared with results in pp collisions at [Formula: see text][Formula: see text] 7 TeV and Pb-Pb collisions at [Formula: see text][Formula: see text] 2.76 TeV. In Pb-Pb and p-Pb collisions, K[Formula: see text] and [Formula: see text] probe the hadronic phase of the system and contribute to the study of particle formation mechanisms by comparison with ot...
The nuclear modification factor, R AA , of the prompt charmed mesons D 0 , D + and D * + , and th... more The nuclear modification factor, R AA , of the prompt charmed mesons D 0 , D + and D * + , and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at a centre-of-mass energy √ s NN = 2.76 TeV in two transverse momentum intervals, 5 < p T < 8 GeV/c and 8 < p T < 16 GeV/c, and in six collision centrality classes. The R AA shows a maximum suppression of a factor of 5-6 in the 10% most central collisions. The suppression and its centrality dependence are compatible within uncertainties with those of charged pions. A comparison with the R AA of non-prompt J/ψ from B meson decays, measured by the CMS Collaboration, hints at a larger suppression of D mesons in the most central collisions.
Uploads
Papers by Ester Casula