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Measurement of D* Mesons in Jets from p+p Collisions at sqrt{s} = 200 GeV

135   0   0.0 ( 0 )
 Added by Xin Dong
 Publication date 2009
  fields
and research's language is English




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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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The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the invariant differential cross section for production of K^0_S , omega, eta prime, and phi mesons in p + p collisions at = 200 GeV. Measurements omega and phi production in different decay channels give consistent results. New results for the phi are in agreement with previously published data and extend the measured pT coverage. The spectral shapes of all hadron transverse momentum distributions measured by PHENIX are well described by a Tsallis distribution functional form with only two parameters, n and T, determining the high-pT and characterizing the low-pT regions of the spectra, respectively. The values of these parameters are very similar for all analyzed meson spectra, but with a lower parameter T extracted for protons. The integrated invariant cross sections calculated from the fitted distributions are found to be consistent with existing measurements and with statistical model predictions.
We report measurements of charmed-hadron ($D^{0}$, $D^{*}$) production cross sections at mid-rapidity in $p$ + $p$ collisions at a center-of-mass energy of 200 GeV by the STAR experiment. Charmed hadrons were reconstructed via the hadronic decays $D^{0}rightarrow K^{-}pi^{+}$, $D^{*+}rightarrow D^{0}pi^{+}rightarrow K^{-}pi^{+}pi^{+}$ and their charge conjugates, covering the $p_T$ range of 0.6$-$2.0 GeV/$c$ and 2.0$-$6.0 GeV/$c$ for $D^{0}$ and $D^{*+}$, respectively. From this analysis, the charm-pair production cross section at mid-rapidity is $dsigma/dy|_{y=0}^{cbar{c}}$ = 170 $pm$ 45 (stat.) $^{+38}_{-59}$ (sys.) $mu$b. The extracted charm-pair cross section is compared to perturbative QCD calculations. The transverse momentum differential cross section is found to be consistent with the upper bound of a Fixed-Order Next-to-Leading Logarithm calculation.
The STAR Collaboration at RHIC has measured two-pion correlation functions from p+p collisions at sqrt(s)=200 GeV. Spatial scales are extracted via a femtoscopic analysis of the correlations, though this analysis is complicated by the presence of strong non-femtoscopic effects. Our results are put into the context of the world dataset of femtoscopy in hadron-hadron collisions. We present the first direct comparison of femtoscopy in p+p and heavy ion collisions, under identical analysis and detector conditions.
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.
130 - Yuhei Morino 2008
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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