Recently, multiparticle-correlation measurements of relativistic p/d/^{3}He+Au, p+Pb, and even p+p collisions show surprising collective signatures. Here, we present beam-energy-scan measurements of ...two-, four-, and six-particle angular correlations in d+Au collisions at sqrts_{NN}=200, 62.4, 39, and 19.6 GeV. We also present measurements of two- and four-particle angular correlations in p+Au collisions at sqrts_{NN}=200 GeV. We find the four-particle cumulant to be real valued for d+Au collisions at all four energies. We also find that the four-particle cumulant in p+Au has the opposite sign as that in d+Au. Further, we find that the six-particle cumulant agrees with the four-particle cumulant in d+Au collisions at 200 GeV, indicating that nonflow effects are subdominant. These observations provide strong evidence that the correlations originate from the initial geometric configuration, which is then translated into the momentum distribution for all particles, commonly referred to as collectivity.
We present measurements of the cross section and double-helicity asymmetry ALL of direct-photon production in p→+p→ collisions at s=510 GeV. The measurements have been performed at midrapidity (|η|
We synthesized 1-ethylimidazolyl-substituted nitronyl nitroxides,
i.e.
, 2-(1-ethylimidazol-4-yl)- (L
4Et
) and 2-(1-ethylimidazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1
H
-imidazole 3-oxide-1-oxyl ...(L
5Et
). The stable radical L
5Et
is an ethyl analog of 2-(1-methylimidazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1
H
-imidazole 3-oxide-1-oxyl (L
5Me
) described earlier, the reaction of which with Cu(hfac)
2
(hfac is 1,1,1,5,5,5-hexafluoropentane-2,4-dionate) leads to the formation of the Cu(hfac)
2
(L
5Me
)
2
jumping crystals. The reaction of Cu(hfac)
2
with L
5Et
with reagent ratios 1: 2 and 1: 1 yields heterospin complexes Cu(hfac)
2
(L
5Et
)
2
and Cu(hfac)
2
L
5Et
2
, respectively. X-ray diffraction study of the mononuclear complex Cu(hfac)
2
(L
5Et
)
2
determined that the compound has a packing similar to that of jumping crystals studied earlier, with the only difference being that the O...O contacts between neigh- boring nitroxide groups were found to be 0.3—0.5 Å longer than in Cu(hfac)
2
(L
5Me
)
2
. As a result of the lengthening of these contacts, Cu(hfac)
2
(L
5Et
)
2
crystals lack chemomechanical activi- ty. We found that when cooling crystals of binuclear complex Cu(hfac)
2
L
5Et
2
below 50 K, the antiferromagnetic exchange between unpaired electrons of the >N—•O groups of neighboring molecules leads to the full spin-pairing of the nitroxides, with only the Cu
2+
ions contributing to the residual paramagnetism of the compound.
Reported here are transverse single-spin asymmetries (AN) in the production of charged hadrons as a function of transverse momentum (pT) and Feynman-x (xF) in polarized p↑ + p, p↑ + Al, and p↑ + Au ...collisions at $\sqrt{^SNN}$ = 200 GeV. The measurements have been performed at forward and backward rapidity (1.4 < |η| < 2.4) over the range of 1.5 GeV /c < pT < 7.0 GeV /c and 0.04 < |xF| < 0.2. A nonzero asymmetry is observed for positively charged hadrons at forward rapidity (xF > 0) in p↑ + p collisions, whereas the p↑ + Al and p↑ + Au results show smaller asymmetries. This finding provides new opportunities to investigate the origin of transverse single-spin asymmetries and a tool to study nuclear effects in p + A collisions.
Polarized proton-proton collisions provide leading-order access to gluons, presenting an opportunity to constrain gluon spin-momentum correlations within transversely polarized protons and enhance ...our understanding of the three-dimensional structure of the proton. Midrapidity open-heavy-flavor production at $\sqrt{s}$ = 200 GeV is dominated by gluon-gluon fusion, providing heightened sensitivity to gluon dynamics relative to other production channels. Transverse single-spin asymmetries of positrons and electrons from heavy-flavor hadron decays are measured at midrapidity using the PHENIX detector at the Relativistic Heavy Ion Collider. These charge-separated measurements are sensitive to gluon correlators that can in principle be related to gluon orbital angular momentum via model calculations. Explicit constraints on gluon correlators are extracted for two separate models, one of which had not been constrained previously.
The cross section and transverse single-spin asymmetries of μ− and μ+ from open heavy-flavor decays in polarized p+p collisions at 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 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<pT<7 GeV/c for the cross section and 1.25<pT<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.
Presented are the first measurements of the transverse single-spin asymmetries ($A_N$) for neutral pions and eta mesons in $\textit{p}$ + Au and $\textit{p}$ + Al collisions at $\sqrt{s_{NN}}$ = 200 ...GeV in the pseudorapidity range |$\textit{η}$| < 0.35 with the PHENIX detector at the Relativistic Heavy Ion Collider. The asymmetries are consistent with zero, similar to those for midrapidity neutral pions and eta mesons produced in $\textit{p}$ + $\textit{p}$ collisions. These measurements show no evidence of additional effects that could potentially arise from the more complex partonic environment present in proton-nucleus collisions.
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