We present a measurement of the cross section and transverse single-spin asymmetry ($A_N$) for $\eta$ mesons at large pseudorapidity from $\sqrt{s}=200$~GeV $p^{\uparrow}+p$ collisions. The measured cross section for $0.5
The measured ETA meson cross section, E*D3(SIG)/DP**3, versus PT at forward rapidity. The statistical and systematic uncertainties are type-A and type-B uncertainties respectively.
ASYM(PEAK) and ASYM(BG) for ETA mesons measured as a function of XF in the range 0.3 < ABS(XF) < 0.7 from the 4X4B triggered dataset. The values represented are the weighted mean of the South and North MPC (Muon Piston Calorimeter). The uncertainties listed are statistical only.
ASYM for ETA mesons measured as a function of XF in the range 0.2 < ABS(XF) < 0.7. Uncertainties listed are those due to the statistics, the XF uncorrelated uncertainties due to extracting the yields, and the correlated relative luminosity uncertainty.
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 $1
Differential cross sections of (OMEGA + RHO) and PHI as functions of PT. The statistical uncertainty includes the type-A systematic uncertainty. The systematic uncertainty is the type-B systematic uncertainty.
Differential cross sections of (OMEGA + RHO) and PHI as functions of rapidity. The statistical uncertainty includes the type-A systematic uncertainty. The systematic uncertainty is the type-B systematic uncertainty.
N(PHI) / ( N(OMEGA) + N(RHO) ) as a function of PT. The statistical uncertainty includes the type-A systematic uncertainty. The systematic uncertainty is the type-B systematic uncertainty.
The PHENIX experiment at RHIC has measured the centrality dependence of the direct photon yield from Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV down to $p_T=0.4$ GeV/$c$. Photons are detected via photon conversions to $e^+e^-$ pairs and an improved technique is applied that minimizes the systematic uncertainties that usually limit direct photon measurements, in particular at low $p_T$. We find an excess of direct photons above the $N_{\rm coll}$-scaled yield measured in $p$$+$$p$ collisions. This excess yield is well described by an exponential distribution with an inverse slope of about 240 MeV/$c$ in the $p_T$ range from 0.6--2.0 GeV/$c$. While the shape of the $p_T$ distribution is independent of centrality within the experimental uncertainties, the yield increases rapidly with increasing centrality, scaling approximately with $N_{\rm part}^\alpha$, where $\alpha=1.48{\pm}0.08({\rm stat}){\pm}0.04({\rm syst})$.
Ratio $R_{\gamma}$ as function of photon $p_T$ from the 2007 and 2010 data sets in minimum-bias Au+Au collisions, and the $R_{\gamma}$ in the combined 2007+2010 measurement.
Ratio $R_{\gamma}$ as function of photon $p_T$ for the combined 2007 and 2010 data sets in different centrality bins.
Direct photon $p_T$ spectra in different centrality bins.
We report a measurement of $e^+e^-$ pairs from semileptonic heavy-flavor decays in $d$$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. Exploring the mass and transverse-momentum dependence of the yield, the bottom decay contribution can be isolated from charm, and quantified by comparison to {\sc pythia} and {\sc mc@nlo} simulations. The resulting $b\bar{b}$-production cross section is $\sigma^{d{\rm Au}}_{b\bar{b}}=1.37{\pm}0.28({\rm stat}){\pm}0.46({\rm syst})$~mb, which is equivalent to a nucleon-nucleon cross section of $\sigma^{NN}_{bb}=3.4\pm0.8({\rm stat}){\pm}1.1({\rm syst})\ \mu$b.
$b\bar{b}$ cross section
We present azimuthal angular correlations between charged hadrons and energy deposited in calorimeter towers in central $d$$+$Au and minimum bias $p$$+$$p$ collisions at $\sqrt{s_{_{NN}}}=200$ GeV. The charged hadron is measured at midrapidity $|\eta|<0.35$, and the energy is measured at large rapidity ($-3.7<\eta<-3.1$, Au-going direction). An enhanced near-side angular correlation across $|\Delta\eta| >$ 2.75 is observed in $d$$+$Au collisions. Using the event plane method applied to the Au-going energy distribution, we extract the anisotropy strength $v_2$ for inclusive charged hadrons at midrapidity up to $p_T=4.5$ GeV/$c$. We also present the measurement of $v_2$ for identified $\pi^{\pm}$ and (anti)protons in central $d$$+$Au collisions, and observe a mass-ordering pattern similar to that seen in heavy ion collisions. These results are compared with viscous hydrodynamic calculations and measurements from $p$$+$Pb at $\sqrt{s_{_{NN}}}=5.02$ TeV. The magnitude of the mass-ordering in $d$$+$Au is found to be smaller than that in $p$$+$Pb collisions, which may indicate smaller radial flow in lower energy $d$$+$Au collisions.
$c_2$ ($p_T$) for track lower-tower pairs from 0-5% $d$+Au collisions and $c_2$ ($p_T$) for pairs in minimum bias $p$+$p$ collisions times the dilution factor.
Measured $v_2$ for midrapidity charged tracks in 0-5% central $d$+Au at $\sqrt{s_{NN}}$ = 200 GeV using the event plane method.
Measured $v_2$ ($p_T$) for identified pions, each charged combined, 0-5% central $d$+Au collisions at RHIC.
Measurements of bottomonium production in heavy ion and $p$$+$$p$ collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The inclusive yield of the three $\Upsilon$ states, $\Upsilon(1S+2S+3S)$, was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au$+$Au and $p$$+$$p$ collisions at $\sqrt{s_{_{NN}}}=200$ GeV. The $\Upsilon(1S+2S+3S)\rightarrow e^+e^-$ differential cross section at midrapidity was found to be $B_{\rm ee} d\sigma/dy =$ 108 $\pm$ 38 (stat) $\pm$ 15(syst) $\pm$ 11 (luminosity) pb in $p$$+$$p$ collisions. The nuclear modification factor in the 30\% most central Au$+$Au collisions indicates a suppression of the total $\Upsilon$ state yield relative to the extrapolation from $p$$+$$p$ collision data. The suppression is consistent with measurements made by STAR at RHIC and at higher energies by the CMS experiment at the Large Hadron Collider.
Summary of the measured $\Upsilon$ invariant multiplicities, $BdN/dy$, for one $p + p$ three Au + Au data sets.
Summary of the measured $\Upsilon$ nuclear modification factors, $R_{AA}$, for Au + Au data sets.
Summary of the measured $\Upsilon$ nuclear modification factors, $R_{AA}$, for Au + Au data sets.
Results are presented from data recorded in 2009 by the PHENIX experiment at the Relativistic Heavy Ion Collider for the double-longitudinal spin asymmetry, $A_{LL}$, for $\pi^0$ and $\eta$ production in $\sqrt{s} = 200$ GeV polarized $p$$+$$p$ collisions. Comparison of the $\pi^0$ results with different theory expectations based on fits of other published data showed a preference for small positive values of gluon polarization, $\Delta G$, in the proton in the probed Bjorken $x$ range. The effect of adding the new 2009 \pz data to a recent global analysis of polarized scattering data is also shown, resulting in a best fit value $\Delta G^{[0.05,0.2]}_{\mbox{DSSV}} = 0.06^{+0.11}_{-0.15}$ in the range $0.05
PI0 ASYM(LL) measurements from 2005.
PI0 ASYM(LL) measurements from 2006.
PI0 ASYM(LL) measurements from 2009.
Charged-pion-interferometry measurements were made with respect to the 2$^{\rm nd}$- and 3$^{\rm rd}$-order event plane for Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. A strong azimuthal-angle dependence of the extracted Gaussian-source radii was observed with respect to both the 2$^{\rm nd}$- and 3$^{\rm rd}$-order event planes. The results for the 2$^{\rm nd}$-order dependence indicate that the initial eccentricity is reduced during the medium evolution, but not reversed in the final state, which is consistent with previous results. In contrast, the results for the 3$^{\rm rd}$-order dependence indicate that the initial triangular shape is significantly reduced and potentially reversed by the end of the medium evolution, and that the 3$^{\rm rd}$-order oscillations are largely dominated by the dynamical effects from triangular flow.
The azimuthal dependence of $R^2_s$, $R^2_o$, $R^2_l$, and $R^2_{os}$ for charged pions in 0.2 < $k_T$ < 2.0 GeV/$c$ with respect to second-(a)-(d) and third-order (e)-(h) event plane in Au + Au collisions at $\sqrt{S_{NN}}$ 200 GeV.
The azimuthal dependence of $R^2_s$, $R^2_o$, $R^2_l$, and $R^2_{os}$ for charged pions in 0.2 < $k_T$ < 2.0 GeV/$c$ with respect to second-(a)-(d) and third-order (e)-(h) event plane in Au + Au collisions at $\sqrt{S_{NN}}$ 200 GeV.
The solid points are the oscillation amplitudes relative to the average of HBT radii for four different combinations (a) $2R^{2}_{s,n}/R^{2}_{s,0}$, (b) $2R^{2}_{os,n}/R^{2}_{s,0}$, (c) $2R^{2}_{o,n}/R^{2}_{o,0}$, and (d) $2R^{2}_{o,n}/R^{2}_{s,0}$ as a function of initial spatial anisotropy ($\varepsilon_{n}$), which are calculated using the Glauber model.
Measurements of the midrapidity transverse energy distribution, $d\Et/d\eta$, are presented for $p$$+$$p$, $d$$+$Au, and Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV and additionally for Au$+$Au collisions at $\sqrt{s_{_{NN}}}=62.4$ and 130 GeV. The $d\Et/d\eta$ distributions are first compared with the number of nucleon participants $N_{\rm part}$, number of binary collisions $N_{\rm coll}$, and number of constituent-quark participants $N_{qp}$ calculated from a Glauber model based on the nuclear geometry. For Au$+$Au, $\mean{d\Et/d\eta}/N_{\rm part}$ increases with $N_{\rm part}$, while $\mean{d\Et/d\eta}/N_{qp}$ is approximately constant for all three energies. This indicates that the two component ansatz, $dE_{T}/d\eta \propto (1-x) N_{\rm part}/2 + x N_{\rm coll}$, which has been used to represent $E_T$ distributions, is simply a proxy for $N_{qp}$, and that the $N_{\rm coll}$ term does not represent a hard-scattering component in $E_T$ distributions. The $dE_{T}/d\eta$ distributions of Au$+$Au and $d$$+$Au are then calculated from the measured $p$$+$$p$ $E_T$ distribution using two models that both reproduce the Au$+$Au data. However, while the number-of-constituent-quark-participant model agrees well with the $d$$+$Au data, the additive-quark model does not.
Et EMC distributions for sqrt(sNN) = 62.4 GeV Au+Au collisions shown in 5% wide centrality bins.
Et EMC distributions for sqrt(sNN) = 62.4 GeV Au+Au collisions shown in 5% wide centrality bins.
Et EMC distributions for sqrt(sNN) = 62.4 GeV Au+Au collisions shown in 5% wide centrality bins.
Measurements of transverse-single-spin asymmetries ($A_{N}$) in $p$$+$$p$ collisions at $\sqrt{s}=$62.4 and 200 GeV with the PHENIX detector at RHIC are presented. At midrapidity, $A_{N}$ is measured for neutral pion and eta mesons reconstructed from diphoton decay, and at forward rapidities, neutral pions are measured using both diphotons and electromagnetic clusters. The neutral-pion measurement of $A_{N}$ at midrapidity is consistent with zero with uncertainties a factor of 20 smaller than previous publications, which will lead to improved constraints on the gluon Sivers function. At higher rapidities, where the valence quark distributions are probed, the data exhibit sizable asymmetries. In comparison with previous measurements in this kinematic region, the new data extend the kinematic coverage in $\sqrt{s}$ and $p_T$, and it is found that the asymmetries depend only weakly on $\sqrt{s}$. The origin of the forward $A_{N}$ is presently not understood quantitatively. The extended reach to higher $p_T$ probes the transition between transverse momentum dependent effects at low $p_T$ and multi-parton dynamics at high $p_T$.
Neutral pion $A_N$ at $\sqrt{s} = 62.4$ GeV as a function of $x_F$ in pseudorapidity $3.1 < |\eta| < 3.5$, with statistical and systematic uncertainties.
Neutral pion $A_N$ at $\sqrt{s} = 62.4$ GeV as a function of $x_F$ in pseudorapidity $3.5 < |\eta| < 3.8$, with statistical and systematic uncertainties.
Neutral pion $A_N$ at $\sqrt{s}$ = 62.4 GeV as function of transverse momentum $p_T$.
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