Abstract
Jets of collimated particles serve a multitude of purposes in high energy collisions. Recently, studies of jet interaction with the quark-gluon plasma (QGP) created in high energy heavy ion ...collisions are of growing interest, particularly towards understanding partonic energy loss in the QGP medium and its related modifications of the jet shower and fragmentation. Since the QGP is a colored medium, the extent of jet quenching and consequently, the transport properties of the medium are expected to be sensitive to fundamental properties of the jets such as the flavor of the parton that initiates the jet. Identifying the jet flavor enables an extraction of the mass dependence in jet-QGP interactions. We present a novel approach to tagging heavy-flavor jets at collider experiments utilizing the information contained within jet constituents via the model architecture. We show the performance of this model in proton-proton collisions at center of mass energy √(s) = 200 GeV as characterized by common metrics and showcase its ability to extract high purity heavy-flavor jet sample at various jet momenta and realistic production cross-sections including a brief discussion on the impact of out-of-time pile-up. Such studies open new opportunities for future high purity heavy-flavor measurements at jet energies accessible at current and future collider experiments.
The measurement of the production of charm jets, identified by the presence of a D$^{0}$ meson in the jet constituents, is presented in proton–proton collisions at centre-of-mass energies of $ ...\sqrt{s} $ = 5.02 and 13 TeV with the ALICE detector at the CERN LHC. The D$^{0}$ mesons were reconstructed from their hadronic decay D$^{0}$ → K$^{−}$π$^{+}$ and the respective charge conjugate. Jets were reconstructed from D$^{0}$-meson candidates and charged particles using the anti-k$_{T}$ algorithm, in the jet transverse momentum range 5 < p$_{T,chjet}$< 50 GeV/c, pseudorapidity |η$_{jet}$| < 0.9 − R, and with the jet resolution parameters R = 0.2, 0.4, 0.6. The distribution of the jet momentum fraction carried by a D$^{0}$ meson along the jet axis $ \left({z}_{\Big\Vert}^{\textrm{ch}}\right) $ was measured in the range 0.4 <$ {z}_{\Big\Vert}^{\textrm{ch}} $< 1.0 in four ranges of the jet transverse momentum. Comparisons of results for different collision energies and jet resolution parameters are also presented. The measurements are compared to predictions from Monte Carlo event generators based on leading-order and next-to-leading-order perturbative quantum chromodynamics calculations. A generally good description of the main features of the data is obtained in spite of a few discrepancies at low p$_{T,chjet}$. Measurements were also done for R = 0.3 at $ \sqrt{s} $ = 5.02 and are shown along with their comparisons to theoretical predictions in an appendix to this paper.graphic not available: see fulltext
We present results on two-particle azimuthal correlations of neutral strange baryons (Λ, Λ̄) and mesons (KS0) for pT=2–6 GeV/c associated with non-identified charged particles in d+Au and Au+Au ...collisions at =200 GeV measured by the STAR experiment. We investigate in detail the associated yield of charged particles as a function centrality of the collision and transverse momentum of trigger and associated particles to look for possible flavor, baryon/meson and particle/anti-particle differences. We compare our results to the proton and pion triggered correlations as well as to a fragmentation and recombination model.
Differential triangular flow, v3(pT), of negative pions is measured at sNN=17.3 GeV around midrapidity by the CERES/NA45 experiment at CERN in central PbAu collisions in the range 0–30% with a mean ...centrality of 5.5%. This is the first measurement as a function of transverse momentum of the triangular flow at SPS energies. The pT range extends from about 0.05 GeV/c to more than 2 GeV/c. The triangular flow magnitude, corrected for the HBT effects, is smaller by a factor of about 2 than the one measured by the PHENIX experiment at RHIC and the ALICE experiment at the LHC. Within the analyzed range of central collisions no significant centrality dependence is observed. The data are found to be well described by a viscous hydrodynamic calculation combined with an UrQMD cascade model for the late stages.
Electroosmotic flow in a hydrodynamically closed capillary zone electrophoresis (CZE) separation compartment must be minimized to achieve high efficiency CZE separations. A group of eight potential ...electroosmotic flow suppressors was investigated in this context for the separations in fluorinated ethylene–propylene capillary tubes. The suppressors included water soluble methylhydroxyethyl derivatives of cellulose, polyvinylalcohol, polyvinylpyrrolidones and polyethyleneglycols of different molecular masses and Triton X-100. Methylhydroxyethylcellulose derivatives and polyvinylalcohol were found to provide the highest separation efficiencies for a group of model anions when the electroosmotic flow suppressors were used as the carrier electrolyte additives. Using a methylhydroxyethylcellulose coated separation compartment very significant improvements in the separation efficiencies were achieved for polyvinylpyrrolidones and polyethyleneglycols applied in the carrier electrolyte solutions. For example, polyvinylpyrrolidone K 90 applied in this way gave for some of the model analytes the plate height values approaching those estimated in the calculations as theoretical limits for our experimental conditions (H≈3.5 μm). CZE experiments with albumin and γ-globulin showed that the use of methylhydroxyethylcellulose derivative in the carrier electrolyte solution at pH=9.2 was effective in eliminating potential disturbances in the separation efficiencies of the analytes due to adsorption of the proteins.
Differential elliptic flow spectra v2(pT) of π−, KS0, p, Λ have been measured at sNN=17.3 GeV around midrapidity by the CERN-CERES/NA45 experiment in mid-central Pb+Au collisions (10% of σgeo). The ...pT range extends from about 0.1 GeV/c (0.55 GeV/c for Λ) to more than 2 GeV/c. Protons below 0.4 GeV/c are directly identified by dE/dx. At higher pT, proton elliptic flow is derived as a constituent, besides π+ and K+, of the elliptic flow of positive pion candidates. This retrieval requires additional inputs: (i) of the particle composition, and (ii) of v2(pT) of positive pions. For (i), particle ratios obtained by NA49 are adapted to CERES conditions; for (ii), the measured v2(pT) of negative pions is substituted, assuming π+ and π− elliptic flow magnitudes to be sufficiently close. The v2(pT) spectra are compared to ideal-hydrodynamics calculations. In synopsis of the series π−–KS0–p–Λ, flow magnitudes are seen to fall with decreasing pT progressively even below hydro calculations with early kinetic freeze-out (Tf=160 MeV) leaving not much time for hadronic evolution. The proton v2(pT) data show a downward swing towards low pT with excursions into negative v2 values. The pion-flow isospin asymmetry observed recently by STAR at RHIC, invalidating in principle our working assumption, is found in its impact on proton flow bracketed from above by the direct proton flow data, and not to alter any of our conclusions. Results are discussed in perspective of recent viscous hydrodynamics studies which focus on late hadronic stages.
We report on results of a measurement of {phi} meson production in central Pb-Au collisions at E{sub lab}=158A GeV. For the first time in the history of high energy heavy-ion collisions, {phi} mesons ...were reconstructed both in the K{sup +}K{sup -} and the dilepton decay channels in the same experiment. This measurement yields rapidity densities near midrapidity, from the two decay channels, of 2.05{+-}0.14(stat){+-}0.25(syst) and 2.04{+-}0.49(stat){+-}0.32(syst), respectively. The shape of the measured transverse momentum spectrum is also in close agreement in both decay channels. The data rule out a possible enhancement of the {phi} yield in the leptonic over the hadronic decay channel of a factor 1.6 or larger at the 95% C.L. This rules out the discrepancy reported in the literature between measurements of the hadronic and dimuon decay channels by two different experiments.
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