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Register a new userMeasurement of charm and bottom production in p+p collisions at $sqrt{s}$ = 200 GeV at RHIC-PHENIX
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Yuhei Morino
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RHIC-PHENIX has observed a large suppression pattern and azimuthal anisotropy of non-photonic electron at mid-rapidity ($midetamid<0.35$) in Au+Au collisions at $sqrt{s_{NN}} = 200$ GeV. To understand these results and the interaction of heavy quarks in the hot and dense medium, experimental determination of production ratio of charm over bottom is one of the most important topics, since the behavior of bottom may differ from charm in the medium. We measured the ratio of charm over bottom and total cross section of bottom via partial reconstruction of D$^0$$to$e$^+$ K$^-$ $ u_e$ decay in p+p collisions at $sqrt{s} = 200$ GeV. Total cross sections of charm and bottom were also measured via di-electron continuum in p+p collisions at $sqrt{s} = 200$ GeV.
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Measurements of the differential production of electrons from open-heavy-flavor hadrons with charm- and bottom-quark content in $p$$+$$p$ collisions at $sqrt{s}=200$ GeV are presented. The measurements proceed through displaced-vertex analyses of electron tracks from the semileptonic decay of charm and bottom hadrons using the PHENIX silicon-vertex detector. The relative contribution of electrons from bottom decays to inclusive heavy-flavor-electron production is found to be consistent with fixed-order-plus-next-to-leading-log perturbative-QCD calculations within experimental and theoretical uncertainties. These new measurements in $p$$+$$p$ collisions provide a precision baseline for comparable forthcoming measurements in A$+$A collisions.
The differential cross section for the production of direct photons in p+p collisions at sqrt(s)=200 GeV at midrapidity was measured in the PHENIX detector at the Relativistic Heavy Ion Collider. Inclusive-direct photons were measured in the transverse-momentum range from 5.5--25 GeV/c, extending the range beyond previous measurements. Event structure was studied with an isolation criterion. Next-to-leading-order perturbative-quantum-chromodynamics calculations give a good description of the spectrum. When the cross section is expressed versus x_T, the PHENIX data are seen to be in agreement with measurements from other experiments at different center-of-mass energies.
Particle production sensitive to non-factorizable and non-perturbative processes that contribute to the underlying event associated with a high transverse momentum ($p_{T}$) jet in proton+proton collisions at $sqrt{s}$=200 GeV is studied with the STAR detector. Each event is divided into three regions based on the azimuthal angle with respect to the highest-$p_{T}$ jet direction: in the leading jet direction (Toward), opposite to the leading jet (Away), and perpendicular to the leading jet (Transverse). In the Transverse region, the average charged particle density is found to be between 0.4 and 0.6 and the mean transverse momentum, $langle p_{T}rangle$, between 0.5-0.7 GeV/$c$ for particles with $p_{T}$$>$0.2 GeV/$c$ at mid-pseudorapidity ($|eta|$$<$1) and jet $p_{T}$$>$15 GeV/$c$. Both average particle density and $langle p_{T}rangle$ depend weakly on the leading jet $p_{T}$. Closer inspection of the Transverse region hints that contributions to the underlying event from initial- and final-state radiation are significantly smaller in these collisions than at the higher energies, up to 13 TeV, recorded at the LHC. Underlying event measurements associated with a high-$p_{T}$ jet will contribute to our understanding of QCD processes at hard and soft scales at RHIC energies, as well as provide constraints to modeling of underlying event dynamics.
We report on charmonium measurements [J/psi(1S), psi(2S), and chi_c(1P)] in p+p collisions at sqrt(s)=200 GeV. We find that the fraction of J/psi coming from the feed-down decay of psi and chi_c in the midrapidity region ($|eta|<0.35$) is 9.6+/-2.4% and 32+/-9%, respectively. We also report new, higher statistics p_T and rapidity dependencies of the J/psi yield via dielectron decay in the same midrapidity range and at forward rapidity (1.2<|eta|<2.4) via dimuon decay. These results are compared with measurements from other experiments and discussed in the context of current charmonium production models.
We report the measurement of charged $D^*$ mesons in inclusive jets produced in proton-proton collisions at a center of mass energy $sqrt{s}$ = 200 GeV with the STAR experiment at RHIC. For $D^{*}$ mesons with fractional momenta $0.2 < z < 0.5$ in inclusive jets with 11.5 GeV mean transverse energy, the production rate is found to be $N(D^{*+}+D^{*-})/N(mathrm{jet}) = 0.015 pm 0.008 (mathrm{stat}) pm 0.007 (mathrm{sys})$. This rate is consistent with perturbative QCD evaluation of gluon splitting into a pair of charm quarks and subsequent hadronization.
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