Персона: Рябов, Виктор Германович
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Measurement of charm and bottom production from semileptonic hadron decays in p plus p collisions at root s=200 GeV
Measurements of the differential production of electrons from open-heavy-flavor hadrons with charm-and bottom-quark content in p + p collisions at root s = 200 GeV are presented. The measurements proceed through displaced-vertex analyses of electron tracks from the semileptonic decay of charm and bottom hadrons using the PHENIX silicon-vertex detector. The relative contribution of electrons from bottom decays to inclusive heavy-flavor-electron production is found to be consistent with fixed-order-plus-next-to-leading-log perturbative-QCD calculations within experimental and theoretical uncertainties. These new measurements in p + p collisions provide a precision baseline for comparable forthcoming measurements in A + A collisions.
Measurements of charm, bottom, and Drell-Yan via dimuons in p plus p and p plus Au collisions at root S-NN=200 GeV with PHENIX at RHIC
Dilepton spectra are a classic probe to study ultra-relativistic heavy ion collisions. At RHIC energies, the dimuon continuum is dominated by correlated pairs from semi-leptonic decays of charm and bottom hadrons and the Drell-Yan process. The dimuon spectra contain information on heavy flavor angular correlations, which can constrain the relative contributions from different heavy flavor production mechanisms. Studying heavy flavor correlations in p+Au collisions may provide further insight on cold nuclear matter effects. Measurements of the Drell-Yan cross-section can provide constraints to PDFs, as well as further our understanding in initial state interactions in p+Au collisions. In this talk, we report measurements of pp pairs from charm, bottom, and Drell-Yan in p+p and p+Au collisions at root S-NN = 200 GeV. A further shape analysis is applied to the heavy flavor pair correlations to extract the relative contributions to heavy flavor production mechanisms.
Transverse-single-spin asymmetries of charged pions at midrapidity in transversely polarized p+p collisions at s=200 GeV
© 2022 authors. Published by the American Physical Society.In 2015, the PHENIX Collaboration has measured single-spin asymmetries for charged pions in transversely polarized p+p collisions at the center-of-mass energy of s=200 GeV. The pions were detected at central rapidities of |η|<0.35. The single-spin asymmetries are consistent with zero for each charge individually, as well as consistent with the previously published neutral-pion asymmetries in the same rapidity range. However, they show a slight indication of charge-dependent differences which may suggest a flavor dependence in the underlying mechanisms that create these asymmetries.
Nuclear-modification factor of charged hadrons at forward and backward rapidity in p plus Al and p plus Au collisions at root S-NN=200 GeV
The PHENIX experiment has studied nuclear effects in p + Al and p + Au collisions at root S-NN = 200GeV on charged hadron production at forward rapidity (1.4 < eta < 2.4, p-going direction) and backward rapidity (-2.2 < eta < -1.2, A-going direction). Such effects are quantified by measuring nuclear modification factors as a function of transverse momentum and pseudorapidity in various collision multiplicity selections. In central p + Al and p + Au collisions, a suppression (enhancement) is observed at forward (backward) rapidity compared to the binary scaled yields in p + p collisions. The magnitude of enhancement at backward rapidity is larger in p + Au collisions than in p + Al collisions, which have a smaller number of participating nucleons. However, the results at forward rapidity show a similar suppression within uncertainties. The results in the integrated centrality are compared with calculations using nuclear parton distribution functions, which show a reasonable agreement at the forward rapidity but fail to describe the backward rapidity enhancement.
Hadronic Resonances as Probes for the Late Hadronic Phase in Heavy Ion Collisions at NICA Energies
Measurement of charged pion double spin asymmetries at midrapidity in longitudinally polarized p plus p collisions at root s=510 GeV
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the longitudinal double spin asymmetries, A(LL), for charged pions at midrapidity (vertical bar eta vertical bar < 0.35) in longitudinally polarized p + p collisions at root s. = 510 GeV. These measurements are sensitive to the gluon spin contribution to the total spin of the proton in the parton momentum fraction x range between 0.04 and 0.09. One can infer the sign of the gluon polarization from the ordering of pion asymmetries with charge alone. The asymmetries are found to be consistent with global quantum-chromodynamics fits of deep-inelastic scattering and data at root s = 200 GeV, which show a nonzero positive contribution of gluon spin to the proton spin.
Prospects for Photon Conversion Measurements in the Future MPD Experiment at NICA
Transverse single spin asymmetries of forward neutrons in p+p, p+Al, and p+Au collisions at sNN =200 GeV as a function of transverse and longitudinal momenta
© 2022 authors. Published by the American Physical Society.In 2015 the PHENIX collaboration at the Relativistic Heavy Ion Collider recorded p+p, p+Al, and p+Au collision data at center of mass energies of sNN=200 GeV with the proton beam(s) transversely polarized. At very forward rapidities η>6.8 relative to the polarized proton beam, neutrons were detected either inclusively or in (anti)correlation with detector activity related to hard collisions. The resulting single spin asymmetries, that were previously reported, have now been extracted as a function of the transverse momentum of the neutron as well as its longitudinal momentum fraction xF. The explicit kinematic dependence, combined with the correlation information allows for a closer look at the interplay of different mechanisms suggested to describe these asymmetries, such as hadronic interactions or electromagnetic interactions in ultraperipheral collisions, UPC. Events that are correlated with a hard collision indeed display a mostly negative asymmetry that increases in magnitude as a function of transverse momentum with only little dependence on xF. In contrast, events that are not likely to have emerged from a hard collision display positive asymmetries for the nuclear collisions with a kinematic dependence that resembles that of a UPC based model. Because the UPC interaction depends strongly on the charge of the nucleus, those effects are very small for p+p collisions, moderate for p+Al collisions, and large for p+Au collisions.
J/psi and psi(2S) production at forward rapidity in p plus p collisions at root s=510 GeV
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section, mean transverse momentum, mean transverse momentum squared of inclusive J/psi, and cross section ratio of psi(2S) to J/psi at forward rapidity in p + p collisions at root s = 510 GeV via the dimuon decay channel. Comparison is made to inclusive J/psi cross sections measured at root s = 200 GeV and 2.76-13 TeV. The result is also compared to leading-order nonrelativistic QCD calculations coupled to a color-glass-condensate description of the low-x gluons in the proton at low transverse momentum (p(T)) and to next-to-leading order nonrelativistic QCD calculations for the rest of the p(T) range. These calculations overestimate the data at low p(T). While consistent with the data within uncertainties above approximate to 3 GeV/c, the calculations are systematically below the data. The total cross section times the branching ratio is BR d sigma(J/)(psi)(pp) / dy(1.2 < vertical bar y vertical bar < 2.2,0 < p(T) < 10 GeV/c) = 54.3 +/- 0.5(stat) +/- 5.5(syst) nb.