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Register a new userAngular decay coefficients of $J/psi$ mesons at forward rapidity from $p+p$ collisions at $sqrt{s}=510$ GeV
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We report the first measurement of the full angular distribution for inclusive $J/psirightarrowmu^{+}mu^{-}$ decays in $p$$+$$p$ collisions at $sqrt{s}=510$ GeV. The measurements are made for $J/psi$ transverse momentum $2<p_{T}<10$ GeV/$c$ and rapidity $1.2<y<2.2$ in the Helicity, Collins-Soper, and Gottfried-Jackson reference frames. In all frames the polar coefficient $lambda_{theta}$ is strongly negative at low $p_{T}$ and becomes close to zero at high $p_{T}$, while the azimuthal coefficient $lambda_{phi}$ is close to zero at low $p_{T}$, and becomes slightly negative at higher $p_{T}$. The frame-independent coefficient $tilde{lambda}$ is strongly negative at all $p_{T}$ in all frames. The data are compared to the theoretical predictions provided by nonrelativistic quantum chromodynamics models.
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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 pp collisions at sqrts = 510 GeV via the dimuon decay channel. Comparison is made to inclusive $J/psi$ cross sections measured at sqrts = 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 $approx3$ GeV/$c$, the calculations are systematically below the data. The total cross section times the branching ratio is BR $dsigma^{J/psi}_{pp}/dy (1.2<|y|<2.2, 0<p_T<10~mbox{GeV/$c$}) =$ 54.3 $pm$ 0.5 (stat) $pm$ 5.5 (syst) nb.
We report the first measurement of the fraction of $J/psi$ mesons coming from $B$-meson decay ($F_{B{rightarrow}J/psi}$) in $p$+$p$ collisions at $sqrt{s}=$ 510 GeV. The measurement is performed using the forward silicon vertex detector and central vertex detector at PHENIX, which provide precise tracking and distance-of-closest-approach determinations, enabling the statistical separation of $J/psi$ due to $B$-meson decays from prompt $J/psi$. The measured value of $F_{B{rightarrow}J/psi}$ is 8.1%$pm$2.3% (stat)$pm$1.9% (syst) for $J/psi$ with transverse momenta $0<p_T<5$ GeV/$c$ and rapidity $1.2<|y|<2.2$. The measured fraction $F_{B{rightarrow}J/psi}$ at PHENIX is compared to values measured by other experiments at higher center of mass energies and to fixed-order-next-to-leading-logarithm and color-evaporation-model predictions. The $bbar{b}$ cross section per unit rapidity ($dsigma/dy(pp{rightarrow}bbar{b})$) extracted from the obtained $F_{B{rightarrow}J/psi}$ and the PHENIX inclusive $J/psi$ cross section measured at 200 GeV scaled with color-evaporation-model calculations, at the mean $B$ hadron rapidity $y={pm}1.7$ in 510 GeV $p$$+$$p$ collisions, is $3.63^{+1.92}_{-1.70}mu$b, and it is consistent with the fixed-order-next-to-leading-logarithm calculations.
The cross section of bottom quark-antiquark ($bbar{b}$) production in $p$+$p$ collisions at $sqrt{s}=510$ GeV is measured with the PHENIX detector at the Relativistic Heavy Ion Collider. The results are based on the yield of high mass, like-sign muon pairs measured within the PHENIX muon arm acceptance ($1.2<|y|<2.2$). The $bbar{b}$ signal is extracted from like-sign dimuons by utilizing the unique properties of neutral $B$ meson oscillation. We report a differential cross section of $dsigma_{bbar{b}rightarrow mu^pmmu^pm}/dy = 0.16 pm 0.01~(mbox{stat}) pm 0.02~(mbox{syst}) pm 0.02~(mbox{global})$ nb for like-sign muons in the rapidity and $p_T$ ranges $1.2<|y|<2.2$ and $p_T>1$ GeV/$c$, and dimuon mass of 5--10 GeV/$c^2$. The extrapolated total cross section at this energy for $bbar{b}$ production is $13.1 pm 0.6~(mbox{stat}) pm 1.5~(mbox{syst}) pm 2.7~(mbox{global})~mu$b. The total cross section is compared to a perturbative quantum chromodynamics calculation and is consistent within uncertainties. The azimuthal opening angle between muon pairs from $bbar{b}$ decays and their $p_T$ distributions are compared to distributions generated using {sc ps pythia 6}, which includes next-to-leading order processes. The azimuthal correlations and pair $p_T$ distribution are not very well described by {sc pythia} calculations, but are still consistent within uncertainties. Flavor creation and flavor excitation subprocesses are favored over gluon splitting.
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 $1.2<|y|<2.2$: $dsigma/dy(omega+rhorightarrowmumu) = 80 pm 6 mbox{(stat)} pm 12 mbox{(syst)}$ nb and $dsigma/dy(phirightarrowmumu) = 27 pm 3 mbox{(stat)} pm 4 mbox{(syst)}$ nb. These results are compared with midrapidity measurements and calculations.
We report the double helicity asymmetry, $A_{LL}^{J/psi}$, in inclusive $J/psi$ production at forward rapidity as a function of transverse momentum $p_T$ and rapidity $|y|$. The data analyzed were taken during $sqrt{s}=510$ GeV longitudinally polarized $p$$+$$p$ collisions at the Relativistic Heavy Ion Collider (RHIC) in the 2013 run using the PHENIX detector. At this collision energy, $J/psi$ particles are predominantly produced through gluon-gluon scatterings, thus $A_{LL}^{J/psi}$ is sensitive to the gluon polarization inside the proton. We measured $A_{LL}^{J/psi}$ by detecting the decay daughter muon pairs $mu^+ mu^-$ within the PHENIX muon spectrometers in the rapidity range $1.2<|y|<2.2$. In this kinematic range, we measured the $A_{LL}^{J/psi}$ to be $0.012 pm 0.010$~(stat)~$pm$~$0.003$(syst). The $A_{LL}^{J/psi}$ can be expressed to be proportional to the product of the gluon polarization distributions at two distinct ranges of Bjorken $x$: one at moderate range $x approx 0.05$ where recent RHIC data of jet and $pi^0$ double helicity spin asymmetries have shown evidence for significant gluon polarization, and the other one covering the poorly known small-$x$ region $x approx 2times 10^{-3}$. Thus our new results could be used to further constrain the gluon polarization for $x< 0.05$.
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