20 research outputs found

    Students' participation in collaborative research should be recognised

    No full text
    Letter to the editor

    Systematic study of flow vector decorrelation in sNN=5.02\mathbf{\sqrt{\textit{s}_{_{\bf NN}}}=5.02} TeV Pb-Pb collisions

    No full text
    International audienceMeasurements of the pTp_{\rm T}-dependent flow vector fluctuations in Pb-Pb collisions at sNN=5.02 TeV\sqrt{s_{_{\rm NN}}} = 5.02~\mathrm{TeV} using azimuthal correlations with the ALICE experiment at the LHC are presented. A four-particle correlation approach [1] is used to quantify the effects of flow angle and magnitude fluctuations separately. This paper extends previous studies to additional centrality intervals and provides measurements of the pTp_{\rm T}-dependent flow vector fluctuations at sNN=5.02 TeV\sqrt{s_{_{\rm NN}}} = 5.02~\mathrm{TeV} with two-particle correlations. Significant pTp_{\rm T}-dependent fluctuations of the V2\vec{V}_{2} flow vector in Pb-Pb collisions are found across different centrality ranges, with the largest fluctuations of up to \sim15% being present in the 5% most central collisions. In parallel, no evidence of significant pTp_{\rm T}-dependent fluctuations of V3\vec{V}_{3} or V4\vec{V}_{4} is found. Additionally, evidence of flow angle and magnitude fluctuations is observed with more than 5σ5\sigma significance in central collisions. These observations in Pb-Pb collisions indicate where the classical picture of hydrodynamic modeling with a common symmetry plane breaks down. This has implications for hard probes at high pTp_{\rm T}, which might be biased by pTp_{\rm T}-dependent flow angle fluctuations of at least 23% in central collisions. Given the presented results, existing theoretical models should be re-examined to improve our understanding of initial conditions, quark--gluon plasma (QGP) properties, and the dynamic evolution of the created system

    Measurement of Ωc0\Omega^0_{\rm c} baryon production and branching-fraction ratio BR(Ωc0Ωe+νe)/BR(Ωc0Ωπ+){\rm BR(\Omega^0_c \rightarrow \Omega^- e^+\nu_e)} / {\rm BR(\Omega^0_c \rightarrow \Omega^- \pi^+)} in pp collisions at s\sqrt{s} = 13 TeV

    No full text
    International audienceThe inclusive production of the charm-strange baryon Ωc0\Omega^{0}_{\rm c} is measured for the first time via its semileptonic decay into Ωe+νe\Omega^{-}\rm e^{+}\nu_{e} at midrapidity (y<0.8|y|<0.8) in proton-proton (pp) collisions at the centre-of-mass energy s=13\sqrt{s}=13 TeV with the ALICE detector at the LHC. The transverse momentum (pTp_{\rm T}) differential cross section multiplied by the branching ratio is presented in the interval 2<pT<12 GeV/c2<p_{\rm T}<12~{\rm GeV}/c. The branching-fraction ratio BR(Ωc0Ωe+νe)/BR(Ωc0Ωπ+){\rm BR}(\Omega^0_{\rm c} \rightarrow \Omega^{-}{\rm e}^{+}\nu_{\rm e})/ {\rm BR}(\Omega^0_{\rm c} \rightarrow \Omega^{-}{\pi}^{+}) is measured to be 1.12 ±\pm 0.22 (stat.) ±\pm 0.27 (syst.). Comparisons with other experimental measurements, as well as with theoretical calculations, are presented

    Exclusive four pion photoproduction in ultraperipheral Pb-Pb collisions at sNN=5.02\sqrt{s_{\rm NN}} = 5.02 TeV

    No full text
    International audienceThe intense photon fluxes from relativistic nuclei provide an opportunity to study photonuclear interactions in ultraperipheral collisions. The measurement of coherently photoproduced π+ππ+π\pi^+\pi^-\pi^+\pi^- final states in ultraperipheral Pb-Pb collisions at sNN=5.02\sqrt{s_{\mathrm{NN}}}=5.02 TeV is presented for the first time. The cross section, dσ\sigma/dyy, times the branching ratio (ρπ+π+ππ\rho\rightarrow \pi^+ \pi^+ \pi^- \pi^-) is found to be 47.8±2.3 (stat.)±7.7 (syst.)47.8\pm2.3~\rm{(stat.)}\pm7.7~\rm{(syst.)} mb in the rapidity interval y<0.5|y| < 0.5. The invariant mass distribution is not well described with a single Breit-Wigner resonance. The production of two interfering resonances, ρ(1450)\rho(1450) and ρ(1700)\rho(1700), provides a good description of the data. The values of the masses (mm) and widths (Γ\Gamma) of the resonances extracted from the fit are m1=1385±14 (stat.)±3 (syst.)m_{1}=1385\pm14~\rm{(stat.)}\pm3~\rm{(syst.)} MeV/c2c^2, Γ1=431±36 (stat.)±82 (syst.)\Gamma_{1}=431\pm36~\rm{(stat.)}\pm82~\rm{(syst.)} MeV/c2c^2, m2=1663±13 (stat.)±22 (syst.)m_{2}=1663\pm13~\rm{(stat.)}\pm22~\rm{(syst.)} MeV/c2c^2 and Γ2=357±31 (stat.)±49 (syst.)\Gamma_{2}=357 \pm31~\rm{(stat.)}\pm49~\rm{(syst.)} MeV/c2c^2, respectively. The measured cross sections times the branching ratios are compared to recent theoretical predictions

    Measurement of beauty-quark production in pp collisions at s=13\sqrt{s}=13 TeV via non-prompt D mesons

    No full text
    International audienceThe pTp_{\rm T}-differential production cross sections of non-prompt D0{\rm D^0}, D+{\rm D^+}, and Ds+{\rm D_s^+} mesons originating from beauty-hadron decays are measured in proton-proton collisions at a centre-of-mass energy s\sqrt{s} of 13 TeV. The measurements are performed at midrapidity, y<0.5|y| < 0.5, with the data sample collected by ALICE from 2016 to 2018. The results are in agreement with predictions from several perturbative QCD calculations. The fragmentation fraction of beauty quarks to strange mesons divided by the one to non-strange mesons, fs/(fu+fd)f_{\rm{s}}/(f_{\rm{u}} + f_{\rm{d}}), is found to be 0.114±0.016 (stat.)±0.006 (syst.)±0.003 (BR)±0.003 (extrap.)0.114 \pm 0.016~{\rm (stat.)} \pm 0.006~{\rm (syst.)} \pm 0.003~{\rm (BR)} \pm 0.003~{\rm (extrap.)}. This value is compatible with previous measurements at lower centre-of-mass energies and in different collision systems in agreement with the assumption of universality of fragmentation functions. In addition, the dependence of the non-prompt D meson production on the centre-of-mass energy is investigated by comparing the results obtained at s=5.02\sqrt{s} = 5.02 and 13 TeV, showing a hardening of the non-prompt D-meson pTp_{\rm T}-differential production cross section at higher s\sqrt{s}. Finally, the bb{\rm b\overline{b}} production cross section per unit of rapidity at midrapidity is calculated from the non-prompt D0{\rm D^0}, D+{\rm D^+}, Ds+{\rm D_s^+}, and Λc+\Lambda_{\rm c}^+ hadron measurements, obtaining ${\rm d}\sigma/{\rm d}y = 75.2\pm 3.2~(\mathrm{stat.}) \pm 5.2~(\mathrm{syst.})^{+12.3}_{-3.2} ~(\mathrm{extrap.})\text{ } \rm \mu b \;.

    Measurement of beauty-quark production in pp collisions at s=13\sqrt{s}=13 TeV via non-prompt D mesons

    No full text
    International audienceThe pTp_{\rm T}-differential production cross sections of non-prompt D0{\rm D^0}, D+{\rm D^+}, and Ds+{\rm D_s^+} mesons originating from beauty-hadron decays are measured in proton-proton collisions at a centre-of-mass energy s\sqrt{s} of 13 TeV. The measurements are performed at midrapidity, y<0.5|y| < 0.5, with the data sample collected by ALICE from 2016 to 2018. The results are in agreement with predictions from several perturbative QCD calculations. The fragmentation fraction of beauty quarks to strange mesons divided by the one to non-strange mesons, fs/(fu+fd)f_{\rm{s}}/(f_{\rm{u}} + f_{\rm{d}}), is found to be 0.114±0.016 (stat.)±0.006 (syst.)±0.003 (BR)±0.003 (extrap.)0.114 \pm 0.016~{\rm (stat.)} \pm 0.006~{\rm (syst.)} \pm 0.003~{\rm (BR)} \pm 0.003~{\rm (extrap.)}. This value is compatible with previous measurements at lower centre-of-mass energies and in different collision systems in agreement with the assumption of universality of fragmentation functions. In addition, the dependence of the non-prompt D meson production on the centre-of-mass energy is investigated by comparing the results obtained at s=5.02\sqrt{s} = 5.02 and 13 TeV, showing a hardening of the non-prompt D-meson pTp_{\rm T}-differential production cross section at higher s\sqrt{s}. Finally, the bb{\rm b\overline{b}} production cross section per unit of rapidity at midrapidity is calculated from the non-prompt D0{\rm D^0}, D+{\rm D^+}, Ds+{\rm D_s^+}, and Λc+\Lambda_{\rm c}^+ hadron measurements, obtaining ${\rm d}\sigma/{\rm d}y = 75.2\pm 3.2~(\mathrm{stat.}) \pm 5.2~(\mathrm{syst.})^{+12.3}_{-3.2} ~(\mathrm{extrap.})\text{ } \rm \mu b \;.

    Measurement of Ωc0\Omega^0_{\rm c} baryon production and branching-fraction ratio BR(Ωc0Ωe+νe)/BR(Ωc0Ωπ+){\rm BR(\Omega^0_c \rightarrow \Omega^- e^+\nu_e)} / {\rm BR(\Omega^0_c \rightarrow \Omega^- \pi^+)} in pp collisions at s\sqrt{s} = 13 TeV

    No full text
    International audienceThe inclusive production of the charm-strange baryon Ωc0\Omega^{0}_{\rm c} is measured for the first time via its semileptonic decay into Ωe+νe\Omega^{-}\rm e^{+}\nu_{e} at midrapidity (y<0.8|y|<0.8) in proton-proton (pp) collisions at the centre-of-mass energy s=13\sqrt{s}=13 TeV with the ALICE detector at the LHC. The transverse momentum (pTp_{\rm T}) differential cross section multiplied by the branching ratio is presented in the interval 2<pT<12 GeV/c2<p_{\rm T}<12~{\rm GeV}/c. The branching-fraction ratio BR(Ωc0Ωe+νe)/BR(Ωc0Ωπ+){\rm BR}(\Omega^0_{\rm c} \rightarrow \Omega^{-}{\rm e}^{+}\nu_{\rm e})/ {\rm BR}(\Omega^0_{\rm c} \rightarrow \Omega^{-}{\pi}^{+}) is measured to be 1.12 ±\pm 0.22 (stat.) ±\pm 0.27 (syst.). Comparisons with other experimental measurements, as well as with theoretical calculations, are presented
    corecore