It has been postulated that partonic orbital angular momentum can lead to a significant double-helicity dependence in the net transverse momentum of Drell-Yan dileptons produced in longitudinally polarized p+p collisi...
It has been postulated that partonic orbital angular momentum can lead to a significant double-helicity dependence in the net transverse momentum of Drell-Yan dileptons produced in longitudinally polarized p+p collisions. Analogous effects are also expected for dijet production. If confirmed by experiment, this hypothesis, which is based on semiclassical arguments, could lead to a new approach for studying the contributions of orbital angular momentum to the proton spin. We report the first measurement of the double-helicity dependence of the dijet transverse momentum in longitudinally polarized p+p collisions at s=200 GeV from data taken by the PHENIX experiment in 2005 and 2006. The analysis deduces the transverse momentum of the dijet from the widths of the near- and far-side peaks in the azimuthal correlation of the dihadrons. When averaged over the transverse momentum of the triggered particle, the difference of the root mean square of the dijet transverse momentum between like- and unlike-helicity collisions is found to be −37±88stat±14syst MeV/c.
The production of e+e− pairs for me+e−<0.3 GeV/c2 and 1<pT<5 GeV/c is measured in p+p and Au+Au collisions at sNN=200 GeV. An enhanced yield above hadronic sources is observed. Treating the excess as photo...
详细信息
The production of e+e− pairs for me+e−<0.3 GeV/c2 and 1
We report the first measurement of transverse single-spin asymmetries in J/ψ production from transversely polarized p+p collisions at s=200 GeV with data taken by the PHENIX experiment in 2006 and 2008. The measurem...
We report the first measurement of transverse single-spin asymmetries in J/ψ production from transversely polarized p+p collisions at s=200 GeV with data taken by the PHENIX experiment in 2006 and 2008. The measurement was performed over the rapidity ranges 1.2<|y|<2.2 and |y|<0.35 for transverse momenta up to 6 GeV/c. J/ψ production at the Relativistic Heavy Ion Collider is dominated by processes involving initial-state gluons, and transverse single-spin asymmetries of the J/ψ can provide access to gluon dynamics within the nucleon. Such asymmetries may also shed light on the long-standing question in QCD of the J/ψ production mechanism. Asymmetries were obtained as a function of J/ψ transverse momentum and Feynman-x, with a value of −0.086±0.026stat±0.003syst in the forward region. This result suggests possible nonzero trigluon correlation functions in transversely polarized protons and, if well defined in this reaction, a nonzero gluon Sivers distribution function.
New measurements by the PHENIX experiment at the Relativistic Heavy Ion Collider for η production at midrapidity as a function of transverse momentum (pT) and collision centrality in sNN=200 GeV Au+Au and p+p collisi...
New measurements by the PHENIX experiment at the Relativistic Heavy Ion Collider for η production at midrapidity as a function of transverse momentum (pT) and collision centrality in sNN=200 GeV Au+Au and p+p collisions are presented. They indicate nuclear modification factors (RAA) which are similar in both magnitude and trend to those found in earlier π0 measurements. Linear fits to RAA as a function of pT in 5–20 GeV/c show that the slope is consistent with zero within two standard deviations at all centralities, although a slow rise cannot be excluded. Having different statistical and systematic uncertainties, the π0 and η measurements are complementary at high pT; thus, along with the extended pT range of these data they can provide additional constraints for theoretical modeling and the extraction of transport properties.
PHENIX has measured the e+e− pair continuum in sNN=200 GeV Au+Au and p+p collisions over a wide range of mass and transverse momenta. The e+e− yield is compared to the expectations from hadronic sources, based on PHEN...
PHENIX has measured the e+e− pair continuum in sNN=200 GeV Au+Au and p+p collisions over a wide range of mass and transverse momenta. The e+e− yield is compared to the expectations from hadronic sources, based on PHENIX measurements. In the intermediate-mass region, between the masses of the ϕ and the J/ψ meson, the yield is consistent with expectations from correlated cc̄ production, although other mechanisms are not ruled out. In the low-mass region, below the ϕ, the p+p inclusive mass spectrum is well described by known contributions from light meson decays. In contrast, the Au+Au minimum bias inclusive mass spectrum in this region shows an enhancement by a factor of 4.7±0.4stat±1.5syst±0.9model. At low mass (mee<0.3 GeV/c2) and high pT (1
The Large Area Telescope on board the Fermi satellite (Fermi LAT) detected more than 1.6×106 cosmic-ray electrons/positrons with energies above 60 GeV during its first year of operation. The arrival directions of...
The Large Area Telescope on board the Fermi satellite (Fermi LAT) detected more than 1.6×106 cosmic-ray electrons/positrons with energies above 60 GeV during its first year of operation. The arrival directions of these events were searched for anisotropies of angular scale extending from ∼10° up to 90°, and of minimum energy extending from 60 GeV up to 480 GeV. Two independent techniques were used to search for anisotropies, both resulting in null results. Upper limits on the degree of the anisotropy were set that depended on the analyzed energy range and on the anisotropy’s angular scale. The upper limits for a dipole anisotropy ranged from ∼0.5% to ∼10%.
作者:
H.Y.FUY.KATSUMURAM.Z.LINY.MUROYAK.HATAW.E WANGG.Z.WUAdvanced Science Research Center
Japan Atomic Energy Agency2-4 Shirakata ShiraneTokaimuraNakagunIbaraki 319-1 195Japan Advanced Science Research CenterJapan Atomic Energy Agency2-4 Shirakata ShiraneTokaimuraNakagunIbaraki 319-1 195Japan Nuclear Professional SchoolSchool of EngineeringThe University of Tokyo2-22 Shirakata shiraneTokaimuraNakagunIbaraki 319-1188Japan Shanghai Institute of Applied Physics
Chinese Academy of SciencesNo 2019Jialuo RoadShanghai2018800China Nuclear Professional SchoolSchool of EngineeringThe University of Tokyo2-22 Shirakata shiraneTokaimuraNakagunIbaraki 319-1188Japan
The γd→K+K−pn reaction has been studied to search for the evidence of the Θ+ by detecting K+K− pairs at forward angles. The Fermi-motion-corrected nK+ invariant mass distribution shows a narrow peak at 1.524±0...
The γd→K+K−pn reaction has been studied to search for the evidence of the Θ+ by detecting K+K− pairs at forward angles. The Fermi-motion-corrected nK+ invariant mass distribution shows a narrow peak at 1.524±0.002+0.003 GeV/c2. The statistical significance of the peak calculated from a shape analysis is 5.1 σ, and the differential cross section for the γn→K−Θ+ reaction is estimated to be 12±2 nb/sr in the photon energy range from 2.0 to 2.4 GeV in the LEPS angular range by assuming the isotropic production of the Θ+ in the γn center-of-mass system. The obtained results support the existence of the Θ+.
Photoproduction of Λ(1520) with liquid hydrogen and deuterium targets was examined at photon energies below 2.4 GeV in the SPring-8 LEPS experiment. For the first time, the differential cross sections were measured a...
详细信息
Photoproduction of Λ(1520) with liquid hydrogen and deuterium targets was examined at photon energies below 2.4 GeV in the SPring-8 LEPS experiment. For the first time, the differential cross sections were measured at low energies and with a deuterium target. A large asymmetry of the production cross sections from protons and neutrons was observed at backward K+/0 angles. This suggests the importance of the contact term, which coexists with t-channel K exchange under gauge invariance. This interpretation was compatible with the differential cross sections, decay asymmetry, and photon beam asymmetry measured in the production from protons at forward K+ angles.
暂无评论