Measurements of μ μ pairs from open heavy flavor and Drell-Yan in p + p collisions at s = 200 GeV
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Engineering topics
Bathe, S.
Publications and source records attributed to Bathe, S..
Multiparticle azimuthal correlations for extracting event-by-event elliptic and triangular flow in Au + Au collisions at s N N = 200 GeV
Here, we present measurements of elliptic and triangular azimuthal anisotropy of charged particles detected at forward rapidity 1 < |η| < 3 in Au + Au collisions at √ s NN = 200 GeV, as a function of centrality. The multiparticle cumulant technique is used to obtain the elliptic flow coefficients v 2 {2}, v 2 {4}, v 2 {6}, and v 2 {8}, and triangular flow coefficients v3{2} and v3{4}. Using the small-variance limit, we estimate the mean and variance of the event-by-event v 2 distribution from v 2 {2} and v 2 {4}. In a complementary analysis, we also use a folding procedure to study the distributions of v 2 and v 3 directly, extracting both the mean and variance. Implications for initial geometrical fluctuations and their translation into the final-state momentum distributions are discussed.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Production of π 0 and η mesons in Cu + Au collisions at s N N = 200 GeV
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Low-momentum direct-photon measurement in Cu + Cu collisions at s N N = 200 GeV
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Measurement of ϕ -meson production at forward rapidity in p + p collisions at s = 510 GeV and its energy dependence from s = 200 GeV to 7 TeV
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Pseudorapidity Dependence of Particle Production and Elliptic Flow in Asymmetric Nuclear Collisions of p + Al , p + Au , d + Au , and He 3 + Au at s N N = 200 GeV
Asymmetric nuclear collisions of p + Al , p + Au , d + Au , and He 3 + Au at s N N = 200 GeV rovide an excellent laboratory for understanding particle production, as well as exploring interactions among these particles after their initial creation in the collision. We present measurements of charged hadron production dN ch /dη in all such collision systems over a broad pseudorapidity range and as a function of collision multiplicity. A simple wounded quark model is remarkably successful at describing the full data set. We also measure the elliptic flow v 2 over a similarly broad pseudorapidity range. These measurements provide key constraints on models of particle emission and their translation into flow.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Nonperturbative transverse-momentum-dependent effects in dihadron and direct photon-hadron angular correlations in p + p collisions at s = 200 GeV
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Cross section and longitudinal single-spin asymmetry A L for forward W ± → μ ± ν production in polarized p + p collisions at s = 510 GeV
We have measured the cross section and single-spin asymmetries from forward W ± → μ ± ν production in longitudinally polarized $p+p$ collisions at $\sqrt{s}=510\text{ }\text{ }\mathrm{GeV}$ 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.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Single-spin asymmetry of J / ψ production in p + p , p + Al , and p + Au collisions with transversely polarized proton beams at s N N = 200 GeV
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Lévy-stable two-pion Bose-Einstein correlations in s NN = 200 GeV Au + Au collisions
Here, we present a detailed measurement of charged two-pion correlation functions in 0–30% centrality √ s NN = 200 GeV Au + Au collisions by the PHENIX experiment at the Relativistic Heavy Ion Collider. The data are well described by Bose-Einstein correlation functions stemming from Lévy-stable source distributions. Using a fine transverse momentum binning, we extract the correlation strength parameter λ, the Lévy index of stability α, and the Lévy length scale parameter R as a function of average transverse mass of the pair m T . We find that the positively and the negatively charged pion pairs yield consistent results, and their correlation functions are represented, within uncertainties, by the same Lévy-stable source functions. The λ(m T ) measurements indicate a decrease of the strength of the correlations at low m T . The Lévy length scale parameter R(m T ) decreases with increasing m T , following a hydrodynamically predicted type of scaling behavior. The values of the Lévy index of stability α are found to be significantly lower than the Gaussian case of α = 2, but also significantly larger than the conjectured value that may characterize the critical point of a second-order quark-hadron phase transition.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Measurements of mass-dependent azimuthal anisotropy in central p + Au, d + Au, and He 3 + Au collisions at s N N = 200 GeV
Here, we present measurements of the transverse-momentum dependence of elliptic flow v 2 for identified pions and (anti)protons at midrapidity (|η| < 0.35), in 0%–5% central p+Au and 3 He+Au collisions at √ s NN = 200 GeV. When taken together with previously published measurements in d + Au collisions at √ s NN = 200 GeV, the results cover a broad range of small-collision-system multiplicities and intrinsic initial geometries. We observe a clear mass-dependent splitting of v 2 (p T ) in d + Au and 3 He + Au collisions, just as in large nucleus-nucleus (A + A) collisions, and a smaller splitting in p + Au collisions. Both hydrodynamic and transport model calculations successfully describe the data at low p T (< 1.5GeV/c), but fail to describe various features at higher p T . In all systems, the v 2 values follow an approximate quark-number scaling as a function of the hadron transverse kinetic energy per constituent quark (KE T /n q ), which was also seen previously in A + A collisions.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Measurements of Multiparticle Correlations in d + Au Collisions at 200, 62.4, 39, and 19.6 GeV and p + Au Collisions at 200 GeV and Implications for Collective Behavior
Recently, multiparticle-correlation measurements of relativistic p/d/ 3 He + Au, p + Pb, and even p + p collisions show surprising collective signatures. In this paper, we present beam-energy-scan measurements of two-, four-, and six-particle angular correlations in d + Au collisions at √ s 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 √ s 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. Finally, 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.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Nuclear Dependence of the Transverse-Single-Spin Asymmetry for Forward Neutron Production in Polarized p + A Collisions at s N N = 200 GeV
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
B -meson production at forward and backward rapidity in p + p and Cu + Au collisions at s N N = 200 GeV
The fraction of J/Ψ mesons which come from B-meson decay, F B→J/Ψ , is measured in this paper for J/Ψ rapidity 1.2 < |y| < 2.2 and p T > 0 in p + p and Cu+Au collisions at √ s NN = 200 GeV with the PHENIX detector. The extracted fraction is F B→J/Ψ = 0.025 ± 0.006 (stat) ± 0.010(syst) for p + p collisions. For Cu+Au collisions, F B→J/Ψ is 0.094 ± 0.028 (stat) ± 0.037(syst) in the Au-going direction (-2.2 < y < -1.2) and 0.089 ± 0.026(stat) ± 0.040(syst) in the Cu-going direction (1.2 < y < 2.2). Finally, the nuclear modification factor, R 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.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Measurements of e + e - pairs from open heavy flavor in p + p and d + A collisions at s NN = 200 GeV
In this paper, we report a measurement of e + e - pairs from semileptonic heavy-flavor decays in p + p collisions at √sNN = 200 GeV. The e + e - pair yield from $b\overline{b}$ and $c\overline{c}$ is separated by exploiting a double differential fit done simultaneously in dielectron invariant mass and p T . We used three different event generators, pythia, mc@nlo, and powheg, to simulate the e + e - spectra from $c\overline{c}$ and $b\overline{b}$ production. The data can be well described by all three generators within the detector acceptance. However, when using the generators to extrapolate to 4π, significant differences are observed for the total cross section. These difference are less pronounced for $b\overline{b}$ than for $c\overline{c}$. The same model dependence was observed in already published d + A data. Lastly, the p + p data are also directly compared with d + A data in mass and p T , and within the statistical accuracy no nuclear modification is seen.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Cross section and transverse single-spin asymmetry of muons from open heavy-flavor decays in polarized p + p collisions at s = 200 ? ? GeV
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 in this paper 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 < 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. Finally, the asymmetry results are consistent with zero within uncertainties, and a model calculation based on twist-3 three-gluon correlations agrees with the data.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Measurements of B → J / ψ at forward rapidity in p + p collisions at s = 510 GeV
In this paper, we report the first measurement of the fraction of J / ψ mesons coming from Β-meson decay (F Β→ J / ψ ) in p + p collisions at 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 / ψ due to Β-meson decays from prompt J / ψ . The measured value of F Β→ J / ψ is 8.1% ± 2.3%(stat) ± 1.9%(syst) for J / ψ with transverse momenta 0 < p T < 5 GeV / c and rapidity 1.2 < |y| < 2.2. The measured fraction F Β→ J / ψ 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 bb cross section per unit rapidity [dσ / dy(pp → bb)] extracted from the obtained F Β→ J / ψ and the PHENIX inclusive J / ψ cross section measured at 200 GeV scaled with color-evaporation-model calculations, at the mean Β hadron rapidity y = ±1.7 in 510 GeV p + p collisions, is 3.63 +1.92 -1.70 μb. Finally, it is consistent with the fixed-order-next-to-leading-logarithm calculations.
74 ATOMIC AND MOLECULAR PHYSICS↗