We have measured the cross section and single spin asymmetries from forward \(W^{\pm}\rightarrow\mu^{\pm}\nu\) production in longitudinally polarized $p$$+$$p\( collisions at \)\sqrt{s}=510$ GeV ...using the PHENIX detector at the Relativistic Heavy Ion Collider. The cross sections are consistent with previous measurements at this collision energy, while the most forward and backward longitudinal single spin asymmetries provide new insights into the sea quark helicities in the proton. The charge of the W bosons provides a natural flavor separation of the participating partons.
Phys. Rev. C 90 064908 (2014) We report on $J/\psi$ production from asymmetric Cu+Au heavy-ion collisions
at $\sqrt{s_{_{NN}}}$=200 GeV at the Relativistic Heavy Ion Collider at both
forward ...(Cu-going direction) and backward (Au-going direction) rapidities. The
nuclear modification of $J/\psi$ yields in Cu$+$Au collisions in the Au-going
direction is found to be comparable to that in Au$+$Au collisions when plotted
as a function of the number of participating nucleons. In the Cu-going
direction, $J/\psi$ production shows a stronger suppression. This difference is
comparable in magnitude and has the same sign as the difference expected from
shadowing effects due to stronger low-$x$ gluon suppression in the larger Au
nucleus. The relative suppression is opposite to that expected from hot nuclear
matter dissociation, since a higher energy density is expected in the Au-going
direction.
In the 1990s, a novel semiconductor photon-sensor operated in Geiger-mode was invented in Russia (Silicon PhotoMultiplier), which consists of many tiny pixels and has a single photon level ...sensitivity. Since then, various types of the sensor with this scheme, Pixelized Photon Detectors (PPD), have been developed in many places in the world. For instance, Hamamatsu Photonics K.K. in Japan produces the PPD as a Multi-Pixel Photon Counter. While the internal mechanisms of the PPD have been intensively studied in recent years, the existing models do not succeeded to fully reproduce the output characteristic, such as waveforms at low temperature. We have developed a new model with the transient multiplication and quenching of the realistic avalanche process and have succeeded in reproducing the output waveform of the PPD at various temperature. In this paper, we discuss our improved model.
A hepatitis B virus (HBV) carrier with marked retention of indocyanine green (ICG) and sulfobromophthalein (BSP) was admitted to our hospital for assessment of liver function. On admission, he was ...asymptomatic and blood chemistry tests showed normal values for transaminases and bilirubin. Serum hepatitis B surface antigen (HBsAg) and antibody to hepatitis B e antigen (anti-HBe) were positive. A history of drug abuse or alcoholism was denied. Dye excretion tests revealed marked retention of ICG (R15 = 70%) and BSP (R45 = 23%). Histopathological examination of a liver biopsy specimen obtained during laparoscopic observation showed chronic persistent hepatitis (CPH). Familial research of the patient failed to prove the existence of dye excretory defect in his siblings. Usual cases of CPH due to continuous HBV infection do not show such severe disturbance of organic anion transport. This pattern of the dye excretory defect with CPH has not been reported. Although the relationship between this dye excretory defect and HBV infection is unclear, the existence of the constitutional dye excretory defect due to abnormal organic anion transport in the liver might be considered.
The fraction of \(J/\psi\) mesons which come from B-meson decay, \(\textrm{F}_{B{\rightarrow}J/\psi}\), is measured for J/\(\psi\) rapidity \mbox{\(1.2<|y|<2.2\)} and \(p_T>0\) in \(p\)+\(p\) and ...Cu+Au collisions at \(\sqrt{s_{_{NN}}}\)=200 GeV with the PHENIX detector. The extracted fraction is \(\textrm{F}_{B{\rightarrow}J/\psi}\) = 0.025 \(\pm\) 0.006(stat) \(\pm\) 0.010(syst) for \(p\)+\(p\) collisions. For Cu+Au collisions, \(\textrm{F}_{B{\rightarrow}J/\psi}\) is 0.094 \(\pm\) 0.028(stat) \(\pm\) 0.037(syst) in the Au-going direction (\(-2.2<y<-1.2\)) and 0.089 \(\pm\) 0.026(stat) \(\pm\) 0.040(syst) in the Cu-going direction (\(1.2<y<2.2\)). The nuclear modification factor, \(R_{\rm CuAu}\), of B mesons in Cu+Au collisions is consistent with binary scaling of measured yields in \(p\)+\(p\) at both forward and backward rapidity.
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 \(b\bar{b}\) cross section per unit rapidity (\(d\sigma/dy(pp{\rightarrow}b\bar{b})\)) 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.
Dihadron and isolated direct photon-hadron angular correlations are measured in $p$$+$$p\( collisions at \)\sqrt{s}=510\( GeV. Correlations of charged hadrons of \)0.7<p_T<10\( GeV/\)c\( with ...\)\pi^0\( mesons of \)4<p_T<15\( GeV/\)c\( or isolated direct photons of \)7<p_T<15\( GeV/\)c\( are used to study nonperturbative effects generated by initial-state partonic transverse momentum and final-state transverse momentum from fragmentation. The nonperturbative behavior is characterized by measuring the out-of-plane transverse momentum component \)p_{\rm out}\( perpendicular to the axis of the trigger particle, which is the high-\)p_T\( direct photon or \)\pi^0\(. Nonperturbative evolution effects are extracted from Gaussian fits to the away-side inclusive-charged-hadron yields for different trigger-particle transverse momenta (\)p_T^{\rm trig}\(). The Gaussian widths and root mean square of \)p_{\rm out}\( are reported as a function of the interaction hard scale \)p_T^{\rm trig}\( to investigate possible transverse-momentum-dependent evolution differences between the \)\pi^0\(-h\)^\pm\( and direct photon-h\)^\pm\( correlations and factorization breaking effects. The widths are found to decrease with \)p_T^{\rm trig}\(, which indicates that the Collins-Soper-Sterman soft factor is not driving the evolution with the hard scale in nearly back-to-back dihadron and direct photon-hadron production in \)p$$+$$p$ collisions. This behavior is in contrast to Drell-Yan and semi-inclusive deep-inelastic scattering measurements.
The cross section and transverse single-spin asymmetries of \(\mu^{-}\) and \(\mu^{+}\) from open heavy-flavor decays in polarized \(p\)+\(p\) collisions at \(\sqrt{s}=200\) GeV were measured by the ...PHENIX experiment during 2012 at the Relativistic Heavy Ion Collider. Because heavy-flavor production is dominated by gluon-gluon interactions at \(\sqrt{s}=200\) GeV, these measurements offer a unique opportunity to obtain information on the trigluon correlation functions. The measurements are performed at forward and backward rapidity (\(1.4<|y|<2.0\)) over the transverse momentum range of \(1.25<p_T<7\) GeV/\(c\) for the cross section and \(1.25<p_T<5\) GeV/\(c\) for the asymmetry measurements. The obtained cross section is compared to a fixed-order-plus-next-to-leading-log perturbative-quantum-chromodynamics calculation. The asymmetry results are consistent with zero within uncertainties, and a model calculation based on twist-3 three-gluon correlations agrees with the data.
The PHENIX collaboration presents a concept for a major upgrade to the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). This upgrade, referred to as sPHENIX, brings exciting new ...capability to the RHIC program by opening new and important channels for experimental investigation and utilizing fully the luminosity of the recently upgraded RHIC facility. sPHENIX enables a compelling jet physics program that will address fundamental questions about the nature of the strongly coupled quark-gluon plasma discovered experimentally at RHIC to be a perfect fluid. The upgrade concept addresses specific questions whose answers are necessary to advance our understanding of the quark-gluon plasma: (1) How to reconcile the observed strongly coupled quark-gluon plasma with the asymptotically free theory of quarks and gluons? (2) What are the dynamical changes to the quark-gluon plasma in terms of quasiparticles and excitations as a function of temperature? (3) How sharp is the transition of the quark-gluon plasma from the most strongly coupled regime near Tc to a weakly coupled system of partons known to emerge at asymptotically high temperatures? In three Appendices, we detail the additional physics capabilities gained through further upgrades: (A) two midrapidity detector additions, (B) a forward rapidity upgrade, and (C) an evolution to an ePHENIX detector suitable for a future Electron Ion Collider at RHIC.
Measurements of anisotropic flow Fourier coefficients (\(v_n\)) for inclusive charged particles and identified hadrons \(\pi^{\pm}\), \(K^{\pm}\), \(p\), and \(\bar{p}\) produced at midrapidity in ...Cu+Au collisions at \(\sqrt{s_{_{NN}}}=200\) GeV are presented. The data were collected in 2012 by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). The particle azimuthal distributions with respect to different order symmetry planes \(\Psi_n\), for \(n\)~=~1, 2, and 3 are studied as a function of transverse momentum \(p_T\) over a broad range of collisions centralities. Mass ordering, as expected from hydrodynamic flow, is observed for all three harmonics. The charged-particle results are compared to hydrodynamical and transport model calculations. We also compare these Cu\(+\)Au results with those in Cu\(+\)Cu and Au\(+\)Au collisions at the same \(\sqrt{s_{_{NN}}}\), and find that the \(v_2\) and \(v_3\), as a function of transverse momentum, follow a common scaling with \(1/(\varepsilon_n N_{\rm part}^{1/3})\).
