The momentum distribution of electrons from decays of heavy flavor (charm and beauty) for midrapidity |y| < 0.35 in p+p collisions at sqrt(s) = 200 GeV has been measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) over the transverse momentum range 0.3 < p_T < 9 GeV/c. Two independent methods have been used to determine the heavy flavor yields, and the results are in good agreement with each other. A fixed-order-plus-next-to-leading-log pQCD calculation agrees with the data within the theoretical and experimental uncertainties, with the data/theory ratio of 1.72 +/- 0.02^stat +/- 0.19^sys for 0.3 < p_T < 9 GeV/c. The total charm production cross section at this energy has also been deduced to be sigma_(c c^bar) = 567 +/- 57^stat +/- 224^sys micro barns.
Heavy-flavor decay electrons invariant differential cross-section An additional 10% normalization uncertainty is to add.
Differential charm cross section To obtain this value, the differential "charm-decay" electrons cross-section, integrated over PT>0.4 GeV/c, has been extrapolated down to PT=0 using the spectrum shape predicted by a fixed-order-plus-next-to-leading-log (FONLL)calculation. The contribution from beauty and beauty cascades, estimated to be 0.1 microbarn, has been substracted, and the c->e branching ratio used was 9.5 +- 1.0%.
Total charm cross section To obtain the total charm cross section, the differential charm cross section has been extrapolated to the whole rapidity range, using a HVQMNR rapidity distribution with aCTEQ5M PDF.
J/Psi production in p+p collisions at sqrt(s) = 200 GeV has been Measured in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) over a rapidity range of -2.2 < y < 2.2 and a transverse momentum range of 0 < pT < 9 GeV/c. The statistics available allow a detailed measurement of both the pT and rapidity distributions and are sufficient to constrain production models. The total cross section times branching ratio determined for J/Psi production is B_{ll} sigma_pp^J/psi = 178 +/- 3(stat) +/- 53(syst) +/- 18(norm) nb.
J/PSI differential cross section, times dilepton branching ratio, versus transverse momentum PT, at mid rapidity : -0.35<y<0.35.
J/PSI differential cross section, times dilepton branching ratio, versus transverse momentum PT, at forward rapidities : absolute value of y belongs to [1.2;2.2].
Mean PT^2 value at mid rapidities : -0.35<y<0.35 The mean PT is obtained with a phenomonological fit of the J/PSI distribution in PT of the form (1/(2*PI*PT))*D(SIG)/DPT = A ( 1+(PT/B)^2)^-6 .The systematic error includes the incertainty from the maximum shape deviation permitted by the point-to-point correlated errors and from allowing the exponent of the fit fonctionto be a free parameter.
The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) has measured J/psi production for rapidities 2.2 < y < 2.2 in Au+Au collisions at sqrt(s_NN) = 200 GeV. The J/psi invariant yield and nuclear modification factor R_AA as a function of centrality, transverse momentum and rapidity are reported. A suppression of J/psi relative to binary collision scaling of proton-proton reaction yields is observed. Models which describe the lower energy J/Psi data at the Super Proton Synchrotron (SPS) invoking only J/psi destruction based on the local medium density would predict a significantly larger suppression at RHIC and more suppression at mid rapidity than at forward rapidity. Both trends are contradicted by our data.
J/PSI invariant yield versus transverse momentum for 0-20%, 20-40%, 40-60%, 60-92% centrality at mid rapidity :,-0.35<y<0.35 An up/down correction, to translate each point at the center of it's relative bin, have been applied to the data.
J/PSI invariant yield versus transverse momentum for 0-20%, 20-40%, 40-60%, 60-92% centrality at forward rapidities : absolute value of y belongs to [1.2;2.2] An up/down correction, to translate each point at the center of it's relative bin, have been applied to the data.
Mean PT^2 values for different bins of centrality, at mid rapidities :-0.35<y<0.35,.
We present the first measurement of photoproduction of J/psi and of two-photon production of high-mass e+e- pairs in electromagnetic (or ultra-peripheral) nucleus-nucleus interactions, using Au+Au data at sqrt(s_NN) = 200 GeV. The events are tagged with forward neutrons emitted following Coulomb excitation of one or both Au^{star} nuclei. The event sample consists of 28 events with m_{e+e-} > 2 GeV/c^2 with zero like-sign background. The measured cross sections at midrapidity of d\sigma / dy (J/psi + Xn, y=0) = 76 +/- 33 (stat) +/- 11 (syst) micro b and d^2\sigma/dm dy (e^+e^- + Xn, y=0) = 86 +/- 23 (stat) +/- 16 (syst) micro b/(GeV/c^2) for m_{e+e-} \in [2.0,2.8] GeV/c^2 are consistent with various theoretical predictions.
J/PSI N for ultra peripheral Au+Au reactions. The values has been obtained from the fit of the number of counts as a function of the mass of the e+e- pairs detected. The J/PSI pick has been fixed at the known mass ofJ/PSI : 3.097 GeV/c2.
e+e- pairs N in ultra peripherals Au + Au reactions. The values has been obtained from the fit of the number of counts as a function of the mass of the e+e- pairs.The results are given for 3 intervals of masses of the electron pair : 2.0 to 2.3, 2.3 to 2.8 and 2.0 to 2.8 Gev/c2.
J/PSI production cross section at mid rapidity for ultra peripheral Au+Au reactions.
The momentum distribution of electrons from semi-leptonic decays of charm and bottom for mid-rapidity |y|<0.35 in p+p collisions at sqrt(s)=200 GeV is measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) over the transverse momentum range 2 < p_T < 7 GeV/c. The ratio of the yield of electrons from bottom to that from charm is presented. The ratio is determined using partial D/D^bar --> e^{+/-} K^{-/+} X (K unidentified) reconstruction. It is found that the yield of electrons from bottom becomes significant above 4 GeV/c in p_T. A fixed-order-plus-next-to-leading-log (FONLL) perturbative quantum chromodynamics (pQCD) calculation agrees with the data within the theoretical and experimental uncertainties. The extracted total bottom production cross section at this energy is \sigma_{b\b^bar}= 3.2 ^{+1.2}_{-1.1}(stat) ^{+1.4}_{-1.3}(syst) micro b.
Bottom contribution to the electrons from heavy flavor decay as a function of PT. These values has been obtained using g3data software which to extract the data from the plot and should therefore be used with caution. The g3data program indicates an extra uncertainty of 0.01 on these values.
Differential bottom production cross section at mid rapidity (y=0) To obtain this value, the differential "bottom-decay" electrons cross-section has been extrapolated to PT=0 using the spectrum shape predicted by pQCD. The b->e branching ratio used was 10 +-1%.
Invariant cross section of electrons from heavy flavor decay versus PT These values has been obtained using g3data software which to extract the data from the plot and should therefore be used with caution. The values in the last column indicate the level of uncertainty intoduced by g3data.
The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) has measured electrons from heavy flavor (charm and bottom) decays for 0.3 < p_T < 9 GeV/c at midrapidity (|y| < 0.35) in Au+Au collisions at sqrt(s_NN) = 200 GeV. The nuclear modification factor R_AA relative to p+p collisions shows a strong suppression in central Au+Au collisions, indicating substantial energy loss of heavy quarks in the medium produced at RHIC. A large azimuthal anisotropy, v_2, with respect to the reaction plane is observed for 0.5 < p_T < 5 GeV/c indicating non-zero heavy flavor elliptic flow. Both R_AA and v_2 show a p_T dependence different from those of neutral pions. A comparison to transport models which simultaneously describe R_AA(p_T) and v_2(p_T) suggests that the viscosity to entropy density ratio is close to the conjectured quantum lower bound, i.e., near a perfect fluid.
Invariant yield of electrons from heavy-flavor decays for 0-10% central collisions, versus PT.
Invariant yield of electrons from heavy-flavor decays for 10-20% central collisions, versus PT.
Invariant yield of electrons from heavy-flavor decays for 20-40% central collisions, versus PT.
Transverse momentum distributions and yields for $\pi^{\pm}$, $K^{\pm}$, $p$ and $\bar{p}$ in $p+p$ collisions at $\sqrt{s}$=200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). These data provide important baseline spectra for comparisons with identified particle spectra in heavy ion collisions at RHIC. We present the inverse slope parameter $T_{\rm inv}$, mean transverse momentum $<p_T>$ and yield per unit rapidity $dN/dy$ at each energy, and compare them to other measurements at different $\sqrt{s}$ in $p+p$ and $p+\bar{p}$ collisions. We also present the scaling properties such as $m_T$ scaling, $x_T$ scaling on the $p_T$ spectra between different energies. To discuss the mechanism of the particle production in $p+p$ collisions, the measured spectra are compared to next-to-leading-order or next-to-leading-logarithmic perturbative quantum chromodynamics calculations.
Invariant cross sections for inclusive PI+ and PI- production in P P collisions at a centre-of-mass energy of 200 GeV. There is an additional normalization uncertainty of 9.7 PCT.
Invariant cross sections for inclusive K+ and K- production in P P collisions at a centre-of-mass energy of 200 GeV. There is an additional normalization uncertainty of 9.7 PCT.
Invariant cross sections for inclusive P and PBAR production in P P collisions at a centre-of-mass energy of 200 GeV with feed-down weak decay corrections NOT applied. There is an additional normalization uncertainty of 9.7 PCT.
The PHENIX collaboration at the Relativistic Heavy Ion Collider (RHIC) reports measurements of azimuthal dihadron correlations near midrapidity in $d$$+$Au collisions at $\sqrt{s_{_{NN}}}$=200 GeV. These measurements complement recent analyses by experiments at the Large Hadron Collider (LHC) involving central $p$$+$Pb collisions at $\sqrt{s_{_{NN}}}$=5.02 TeV, which have indicated strong anisotropic long-range correlations in angular distributions of hadron pairs. The origin of these anisotropies is currently unknown. Various competing explanations include parton saturation and hydrodynamic flow. We observe qualitatively similar, but larger, anisotropies in $d$$+$Au collisions compared to those seen in $p$$+$Pb collisions at the LHC. The larger extracted $v_2$ values in $d$$+$Au collisions at RHIC are consistent with expectations from hydrodynamic calculations owing to the larger expected initial-state eccentricity compared with that from $p$$+$Pb collisions. When both are divided by an estimate of the initial-state eccentricity the scaled anisotropies follow a common trend with multiplicity that may extend to heavy ion data at RHIC and the LHC, where the anisotropies are widely thought to arise from hydrodynamic flow.
The second-order pair anisotropy, c2, of the central collision excess as a function of associated particle pT.
The third-order pair anisotropy, c3, of the central collision excess as a function of associated particle pT.
Charged hadron second-order anisotropy, v2, as a function of pT.
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured low mass vector meson, $\omega$, $\rho$, and $\phi$, production through the dimuon decay channel at forward rapidity ($1.2<|y|<2.2$) in $p$$+$$p$ collisions at $\sqrt{s}=200$ GeV. The differential cross sections for these mesons are measured as a function of both $p_T$ and rapidity. We also report the integrated differential cross sections over $1<p_T<7$ GeV/$c$ and $1.2<|y|<2.2$: $d\sigma/dy(\omega+\rho\rightarrow\mu\mu) = 80 \pm 6 \mbox{(stat)} \pm 12 \mbox{(syst)}$ nb and $d\sigma/dy(\phi\rightarrow\mu\mu) = 27 \pm 3 \mbox{(stat)} \pm 4 \mbox{(syst)}$ nb. These results are compared with midrapidity measurements and calculations.
Differential cross sections of (OMEGA + RHO) and PHI as functions of PT. The statistical uncertainty includes the type-A systematic uncertainty. The systematic uncertainty is the type-B systematic uncertainty.
Differential cross sections of (OMEGA + RHO) and PHI as functions of rapidity. The statistical uncertainty includes the type-A systematic uncertainty. The systematic uncertainty is the type-B systematic uncertainty.
N(PHI) / ( N(OMEGA) + N(RHO) ) as a function of PT. The statistical uncertainty includes the type-A systematic uncertainty. The systematic uncertainty is the type-B systematic uncertainty.
The PHENIX experiement has measured the electron-positron pair mass spectrum from 0 to 8 GeV/c^2 in p+p collisions at sqrt(s)=200 GeV. The contributions from light meson decays to e^+e^- pairs have been determined based on measurements of hadron production cross sections by PHENIX. They account for nearly all e^+e^- pairs in the mass region below 1 GeV/c^2. The e^+e^- pair yield remaining after subtracting these contributions is dominated by semileptonic decays of charmed hadrons correlated through flavor conservation. Using the spectral shape predicted by PYTHIA, we estimate the charm production cross section to be 544 +/- 39(stat) +/- 142(syst) +/- 200(model) \mu b, which is consistent with QCD calculations and measurements of single leptons by PHENIX.
Differential charm cross section at mid rapidity An additional +-39.5 microbarn error, due to the validity of the model used to extrapolate the data, is not included The contribution from beauty estimated to be 3.7 microbarn, has been subtracted. The c->e branching ratio used was 9.5 +-1.0%.
Total charm cross section An additional systemactic error of +- 200 microbarn, due to the validity of the model used to extrapolate the data, is not included. To obtain the total charm cross section, the differential charm cross section has been extrapolated to the whole rapidity range, using a HVQMNR rapidity distribution with aCTEQ5M PDF.
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