Inclusive J/ψ/\psi production in Pb-Pb collisions at sNN=5.02\sqrt{s_\textrm{NN}}=5.02 TeV with ALICE

The J$/\psi$ mesons is a bound state of a charm quark and its anti-quark. The production of J$/\psi$ mesons serves as an important probe of the quark-gluon plasma (QGP) formed in heavy-ion collisions. The presence of the deconfined strongly interacting medium results in the color screening of the potential between charm quarks and anti-quarks created during hard scattering processes. At sufficiently high collision energies such as the LHC energy, the large abundance of produced charm quarks leads to the (re)generation of J$/\psi$ mesons during the QGP evolution and/or at the phase boundary. In this work, the J$/\psi$ production yield in Pb-Pb collisions at $\sqrt{s_\textrm{NN}}=5.02$ TeV recorded by ALICE is measured at midrapidity via the dielectron decay channel J$/\psi \rightarrow \textrm{e}^+\textrm{e}^-$ as a function of centrality and as a function of transverse momentum down to $p_\textrm{T}=0.15$ GeV/$c$ in the most central and semi-central collisions. The J$/\psi$ nuclear modification factor $R_\textrm{AA}$ increases slightly from semi-central to the most central collisions. The $p_\textrm{T}$-differential J$/\psi$ $R_\textrm{AA}$ shows a large suppression of the J$/\psi$ yield at high $p_\textrm{T}$ and the J$/\psi$ $R_\textrm{AA}$ increases with decreasing $p_\textrm{T}$. The measurement is compared to other experimental results and to model calculations. The presented results strongly support picture of (re)generation as an important J$/\psi$ production mechanism at the LHC especially significant at low $p_\textrm{T}$ and at midrapidity

Recent results on hard and rare probes from ALICE

In high-energy hadronic collisions, hard parton scatterings with large momentum transfers are prerequisites for the formation of hard and rare probes. In heavy-ion collisions, these probes$-$final state particles related to the early hard-parton scatterings$-$serve as a powerful tool to explore the whole evolution of the medium including the quark$-$gluon plasma (QGP) stage. Hard probes in proton-proton (pp) collisions test perturbative quantum chromodynamics (pQCD) processes and hadronization, and provide a reference for the nuclear collision systems. High-multiplicity pp collisions provide a bridge to heavy-ion collisions, due to their large event activity. Heavy-flavor hadrons containing at least one charm or beauty quark belong to the hard and rare probes. Recently, ALICE has measured a broad palette of heavy-flavour baryons allowing to shed more light on charm fragmentation. Measurements of charmonium production as a function of the event multiplicity can provide insight into the interplay between charmonium-production processes and soft processes driving the multiplicity. ALICE has investigated the multiplicity dependence of J/$\psi$ production at midrapidity and the ratio of $\psi \rm (2S)$ to J/$\psi$ yields at forward rapidity. The charm and beauty cross sections can be constrained by fits of Monte-Carlo generators to the measured dielectron continuum.In high-energy hadronic collisions, hard parton scatterings with large momentum transfers are prerequisites for the formation of hard and rare probes. In heavy-ion collisions, these probes---final state particles related to the early hard-parton scatterings---serve as a powerful tool to explore the whole evolution of the medium including the quark--gluon plasma (QGP) stage. Hard probes in proton-proton (pp) collisions test perturbative quantum chromodynamics (pQCD) processes and hadronization, and provide a reference for the nuclear collision systems. High-multiplicity pp collisions provide a bridge to heavy-ion collisions, due to their large event activity. Heavy-flavor hadrons containing at least one charm or beauty quark belong to the hard and rare probes. Recently, ALICE has measured a broad palette of heavy-flavour baryons allowing to shed more light on charm fragmentation. Measurements of charmonium production as a function of the event multiplicity can provide insight into the interplay between charmonium-production processes and soft processes driving the multiplicity. ALICE has investigated the multiplicity dependence of J/$\psi$ production at midrapidity and the ratio of $\psi \rm (2S)$ to J/$\psi$ yields at forward rapidity. The charm and beauty cross sections can be constrained by fits of Monte-Carlo generators to the measured dielectron continuum

Inclusive J/ψ production in Pb–Pb collisions at √s_NN = 5.02 TeV with ALICE

The J/ψ mesons is a bound state of a charm quark and its anti-quark. The production of J/ψ mesons serves as an important probe of the quark-gluon plasma (QGP) formed in heavy-ion collisions. The presence of the deconfined strongly interacting medium results in the color screening of the potential between charm quarks and anti-quarks created during hard scattering processes. At sufficiently high collision energies such as the LHC energy, the large abundance of produced charm quarks leads to the (re)generation of J/ψ mesons during the QGP evolution and/or at the phase boundary. In this work, the J/ψ production yield in Pb–Pb collisions at √s_NN = 5.02 TeV recorded by ALICE is measured at midrapidity via the dielectron decay channel J/ψ → e+e− as a function of centrality and as a function of transverse momentum down to p_T = 0.15 GeV/c in the most central and semi-central collisions. The J/ψ nuclear modification factor R_AA increases slightly from semi-central to the most central collisions. The p_T -differential J/ψ R_AA shows a large suppression of the J/ψ yield at high p_T and the J/ψ R_AA increases with decreasing p_T. The measurement is compared to other experimental results and to model calculations. The presented results strongly support picture of (re)generation as an important J/ψ production mechanism at the LHC especially significant at low p T and at midrapidity

Age-dependent human β cell proliferation induced by glucagon-like peptide 1 and calcineurin signaling.

Inadequate pancreatic β cell function underlies type 1 and type 2 diabetes mellitus. Strategies to expand functional cells have focused on discovering and controlling mechanisms that limit the proliferation of human β cells. Here, we developed an engraftment strategy to examine age-associated human islet cell replication competence and reveal mechanisms underlying age-dependent decline of β cell proliferation in human islets. We found that exendin-4 (Ex-4), an agonist of the glucagon-like peptide 1 receptor (GLP-1R), stimulates human β cell proliferation in juvenile but not adult islets. This age-dependent responsiveness does not reflect loss of GLP-1R signaling in adult islets, since Ex-4 treatment stimulated insulin secretion by both juvenile and adult human β cells. We show that the mitogenic effect of Ex-4 requires calcineurin/nuclear factor of activated T cells (NFAT) signaling. In juvenile islets, Ex-4 induced expression of calcineurin/NFAT signaling components as well as target genes for proliferation-promoting factors, including NFATC1, FOXM1, and CCNA1. By contrast, expression of these factors in adult islet β cells was not affected by Ex-4 exposure. These studies reveal age-dependent signaling mechanisms regulating human β cell proliferation, and identify elements that could be adapted for therapeutic expansion of human β cells. J Clin Invest 2017 Oct 2; 127(10):3835-3844

Production of K∗(892)0^{*}(892)^{0} and ϕ(1020)\phi(1020) in pp and Pb-Pb collisions at sNN=5.02\sqrt{s_{\rm NN}} = 5.02 TeV

The production of K$^{*}(892)^{0}$ and $\phi(1020)$ mesons in proton-proton (pp) and lead-lead (Pb-Pb) collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV has been measured using the ALICE detector at the Large Hadron Collider (LHC). The transverse momentum ($p_{\mathrm{T}}$) distributions of K$^{*}(892)^{0}$ and $\phi(1020)$ mesons have been measured at midrapidity $(|y| 8$ GeV$/c$, the $R_{\rm AA}$ values of K$^{*}(892)^{0}$ and $\phi(1020)$ are below unity and observed to be similar to those of pions, kaons, and (anti)protons. The $R_{\rm AA}$ values at high $p_{\mathrm T}$ for K$^{*}(892)^{0}$ and $\phi(1020)$ mesons are in agreement within uncertainties for $\sqrt{s_\mathrm{NN}} = 5.02$ and 2.76 TeV

Study of very forward energy and its correlation with particle production at midrapidity in pp and p-Pb collisions at the LHC

International audienceThe energy deposited at very forward rapidities (very forward energy) is a powerful tool for characterising proton fragmentation in pp and p-Pb collisions. The correlation of very forward energy with particle production at midrapidity provides direct insights into the initial stages and the subsequent evolution of the collision. Furthermore, the correlation with the production of particles with large transverse momenta at midrapidity provides information complementary to the measurements of the underlying event, which are usually interpreted in the framework of models implementing centrality-dependent multiple parton interactions.Results about very forward energy, measured by the ALICE zero degree calorimeters (ZDCs), and its dependence on the activity measured at midrapidity in pp collisions at $\sqrt{s}$ = 13 TeV and in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 8.16 TeV are discussed. The measurements performed in pp collisions are compared with the expectations of three hadronic interaction event generators: PYTHIA 6 (Perugia 2011 tune), PYTHIA 8 (Monash tune), and EPOS LHC. These results provide new constraints on the validity of models in describing the beam remnants at very forward rapidities, where perturbative QCD cannot be used.[graphic not available: see fulltext

Production of K∗(892)0^{*}(892)^{0} and ϕ(1020)\phi(1020) in pp and Pb-Pb collisions at sNN=5.02\sqrt{s_{\rm NN}} = 5.02 TeV

The production of K$^{*}(892)^{0}$ and $\phi(1020)$ mesons in proton-proton (pp) and lead-lead (Pb-Pb) collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV has been measured using the ALICE detector at the Large Hadron Collider (LHC). The transverse momentum ($p_{\mathrm{T}}$) distributions of K$^{*}(892)^{0}$ and $\phi(1020)$ mesons have been measured at midrapidity $(|y| 8$ GeV$/c$, the $R_{\rm AA}$ values of K$^{*}(892)^{0}$ and $\phi(1020)$ are below unity and observed to be similar to those of pions, kaons, and (anti)protons. The $R_{\rm AA}$ values at high $p_{\mathrm T}$ for K$^{*}(892)^{0}$ and $\phi(1020)$ mesons are in agreement within uncertainties for $\sqrt{s_\mathrm{NN}} = 5.02$ and 2.76 TeV

Forward rapidity J/ψ production as a function of charged-particle multiplicity in pp collisions at s \sqrt{s} = 5.02 and 13 TeV

International audienceThe 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 $\sqrt{s}$ = 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 (dN$_{ch}$/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 (dN$_{ch}$/dη/〈dN$_{ch}$/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 (〈p$_{T}$〉) of J/ψ in pp collisions exhibits an increasing trend as a function of dN$_{ch}$/dη/〈dN$_{ch}$/dη〉 showing a saturation towards high charged-particle multiplicities.[graphic not available: see fulltext