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Adare, A.,Afanasiev, S.,Aidala, C.,Ajitanand, N. N.,Akiba, Y.,Al-Bataineh, H.,Alexander, J.,Alfred, M.,Aoki, K.,Apadula, N.,Aphecetche, L.,Asai, J.,Atomssa, E. T.,Averbeck, R.,Awes, T. C.,Ayuso, C.,Az American Physical Society 2017 Physical Review C Vol.96 No.2
<P>We report a measurement of e(+)e(-) pairs from semileptonic heavy-flavor decays in p + p collisions at root S-NN = 200 GeV. The e(+)e(-) pair yield from b (b) over bar and c (c) over bar 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 (c) over bar and b (b) over bar production. The data can be well described by all three generators within the detector acceptance. However, when using the generators to extrapolate to 4 pi, significant differences are observed for the total cross section. These difference are less pronounced for b (b) over bar than for c (c) over bar. The same model dependence was observed in already published d + A data. 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.</P>
Aidala, C.,Ajitanand, N. N.,Akiba, Y.,Akimoto, R.,Alexander, J.,Alfred, M.,Aoki, K.,Apadula, N.,Asano, H.,Atomssa, E. T.,Awes, T. C.,Ayuso, C.,Azmoun, B.,Babintsev, V.,Bagoly, A.,Bai, M.,Bai, X.,Banni American Physical Society 2017 Physical Review D Vol.95 No.11
<P>The cross section and transverse single-spin asymmetries of mu(-) and mu(+) from open heavy-flavor decays in polarized p + p collisions at pffisffiffi root 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 ffiffiffi root 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 < vertical bar y vertical bar < 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.</P>
Adare, A.,Aidala, C.,Ajitanand, N. N.,Akiba, Y.,Akimoto, R.,Alexander, J.,Alfred, M.,Andrieux, V.,Aoki, K.,Apadula, N.,Aramaki, Y.,Asano, H.,Atomssa, E. T.,Awes, T. C.,Ayuso, C.,Azmoun, B.,Babintsev, American Physical Society 2017 Physical Review D Vol.95 No.7
<P>Dihadron and isolated direct photon-hadron angular correlations are measured in p + p collisions at root 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(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)(trig)). The Gaussian widths and root mean square of p(out) are reported as a function of the interaction hard scale p(T)(trig) to investigate possible transverse-momentum-dependent evolution differences between the pi(0)-h(+/-) and direct photon-h(+/-) correlations and factorization breaking effects. The widths are found to decrease with p(T)(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.</P>
Adare, A.,Afanasiev, S.,Aidala, C.,Ajitanand, N. N.,Akiba, Y.,Al-Bataineh, H.,Alexander, J.,Aoki, K.,Aramaki, Y.,Atomssa, E. T.,Averbeck, R.,Awes, T. C.,Azmoun, B.,Babintsev, V.,Bai, M.,Baksay, G.,Bak American Physical Society 2016 Physical Review C Vol.93 No.5
<P>Measurements of the anisotropic flow coefficients v(2){Psi(2)}, v(3){Psi(3)}, v(4){Psi(4)}, and v(4){Psi(2)} for identified particles (pi(+/-), K-+/-, and p + (p) over bar) at midrapidity, obtained relative to the event planes Psi(m) at forward rapidities in Au + Au collisions at root s(NN) = 200 GeV, are presented as a function of collision centrality and particle transverse momenta p(T). The v(n) coefficients show characteristic patterns consistent with hydrodynamical expansion of the matter produced in the collisions. For each harmonic n, a modified valence quark-number N-q scaling [plotting v(n){Psi(m)}/(N-q)(n/2) versus transverse kinetic energies (KET)/N-q] is observed to yield a single curve for all the measured particle species for a broad range of KET. A simultaneous blast-wave model fit to the observed v(n){Psi(m)}(p(T)) coefficients and published particle spectra identifies radial flow anisotropies rho(n){Psi(m)} and spatial eccentricities s(n){Psi(m)} at freeze-out. These are generally smaller than the initial-state participant-plane geometric eccentricities epsilon(n){Psi(PP)(m)} as also observed in the final eccentricity from quantum interferometry measurements with respect to the event plane.</P>
Dilepton mass spectra in p+p collisions at s=200 GeV and the contribution from open charm
PHENIX Collaboration,Adare, A.,Afanasiev, S.,Aidala, C.,Ajitanand, N.N.,Akiba, Y.,Al-Bataineh, H.,Alexander, J.,Aoki, K.,Aphecetche, L.,Armendariz, R.,Aronson, S.H.,Asai, J.,Atomssa, E.T.,Averbeck, R. North-Holland Pub. Co 2009 Physics letters: B Vol.670 No.4
<P>PHENIX has measured the electron-positron pair mass spectrum from 0 to 8 GeV/c(2) in p + p collisions at root s = 200 GeV. The contributions from light meson decays to e(+)e(-) pairs have been determined based on measurements of hadron production cross sections by PHENIX. Within the systematic uncertainty of similar to 20% they account for all e(+)e(-) pairs in the mass region below similar to 1 GeV/c(2). The e(+)e(-) pair yield remaining after subtracting these contributions is dominated by semileptonic decays of charmed hadrons correlated through flavor conservation. Using the spectral shape predicted by PYTHIA, we estimate the charm production cross section to be 544 +/- 39(stat) +/- 142(syst) +/- 200(model) pb. which is consistent with QCD calculations and measurements of single leptons by PHENIX. (C) 2008 Elsevier BV. All rights reserved.</P>
Adare, A.,Aidala, C.,Ajitanand, N. N.,Akiba, Y.,Akimoto, R.,Al-Bataineh, H.,Alexander, J.,Alfred, M.,Angerami, A.,Aoki, K.,Apadula, N.,Aramaki, Y.,Asano, H.,Atomssa, E. T.,Averbeck, R.,Awes, T. C.,Azm American Physical Society 2014 PHYSICAL REVIEW D - Vol.90 No.7
<P>We present a measurement of the cross section and transverse single-spin asymmetry (AN) for. mesons at large pseudorapidity from root s = 200 GeV p up arrow + p collisions. The measured cross section for 0.5 < p(T) < 5.0 GeV/c and 3.0 < vertical bar eta vertical bar < 3.8 is well described by a next-to-leading-order perturbative-quantum-chromodynamics calculation. The asymmetries A(N) have been measured as a function of Feynman-x (x(F)) from 0.2 < vertical bar x(F)vertical bar < 0.7, as well as transverse momentum (p(T)) from 1.0 < p(T) < 4.5 GeV/c. The asymmetry averaged over positive x(F) is < A(N)> = 0.061 +/- 0.014. The results are consistent with prior transverse single-spin measurements of forward eta and pi(0) mesons at various energies in overlapping x(F) ranges. Comparison of different particle species can help to determine the origin of the large observed asymmetries in p up arrow + p collisions.</P>
Angular decay coefficients of J/ψ mesons at forward rapidity from p+p collisions at s=510 GeV
Adare, A.,Aidala, C.,Ajitanand, N. N.,Akiba, Y.,Akimoto, R.,Alfred, M.,Andrieux, V.,Aoki, K.,Apadula, N.,Aramaki, Y.,Asano, H.,Atomssa, E. T.,Awes, T. C.,Ayuso, C.,Azmoun, B.,Babintsev, V.,Bai, M.,Ban American Physical Society 2017 Physical Review D Vol.95 No.9
<P>We report the first measurement of the full angular distribution for inclusive J/psi -> mu(+)mu(-) decays in p + p collisions at root 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 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.</P>
Measurements of B→J/ψ at forward rapidity in p+p collisions at s=510 GeV
Aidala, C.,Ajitanand, N. N.,Akiba, Y.,Akimoto, R.,Alexander, J.,Alfred, M.,Aoki, K.,Apadula, N.,Asano, H.,Atomssa, E. T.,Attila, A.,Awes, T. C.,Ayuso, C.,Azmoun, B.,Babintsev, V.,Bai, M.,Bai, X.,Banni American Physical Society 2017 Physical Review D Vol.95 No.9
<P>We report the first measurement of the fraction of J/psi mesons coming from B-meson decay (F (B -> J/psi)) in p + p collisions at root 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=. due to B-meson decays from prompt J/psi. The measured value of F (B -> J/psi) is 8.1% +/- 2.3% (stat) +/- 1.9% (syst) for J/psi with transverse momenta 0 < p(T) < 5 GeV/c and rapidity 1.2 < vertical bar y vertical bar < 2.2. The measured fraction F (B -> J/psi) at PHENIX is compared to values measured by other experiments at higher center of mass energies and to fixed-order-next-toleading- logarithm and color-evaporation-model predictions. The b (b) over bar cross section per unit rapidity [d sigma/dy(pp -> b (b) over bar)] extracted from the obtained F (B -> 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 = +/- 1.7 in 510 GeV p + p collisions, is 3.63(-1.70)(+1.92) mu b. It is consistent with the fixed-order-next-toleading- logarithm calculations.</P>
Adare, A.,Aidala, C.,Ajitanand, N. N.,Akiba, Y.,Akimoto, R.,Alfred, M.,Apadula, N.,Aramaki, Y.,Asano, H.,Atomssa, E. T.,Awes, T. C.,Azmoun, B.,Babintsev, V.,Bai, M.,Bandara, N. S.,Bannier, B.,Barish, American Physical Society 2016 Physical Review D Vol.94 No.11
<P>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 root s = 510 GeV longitudinally polarized p + p collisions at the Relativistic Heavy Ion Collider 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 +/- 0.010 (stat) +/- 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 approximate to 5 x 10(-2) where recent 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 approximate to 2 x 10(-3). Thus our new results could be used to further constrain the gluon polarization for x < 5 x 10(-2).</P>
ForwardJ/ψproduction in U + U collisions at<sub>sNN</sub>=193GeV
Adare, A.,Aidala, C.,Ajitanand, N. N.,Akiba, Y.,Akimoto, R.,Alexander, J.,Alfred, M.,Aoki, K.,Apadula, N.,Asano, H.,Atomssa, E. T.,Awes, T. C.,Azmoun, B.,Babintsev, V.,Bai, M.,Bai, X.,Bandara, N. S.,B American Physical Society 2016 Physical Review C Vol.93 No.3
<P>The invariant yields, dN/dy, for J/psi production at forward rapidity (1.2 < vertical bar y vertical bar < 2.2) in U + U collisions at root S-NN = 193 GeV have been measured as a function of collision centrality. The invariant yields and nuclear-modification factor R-AA are presented and compared with those from Au + Au collisions in the same rapidity range. Additionally, the direct ratio of the invariant yields from U + U and Au + Au collisions within the same centrality class is presented, and used to investigate the role of c (c) over bar coalescence. Two different parametrizations of the deformed Woods-Saxon distribution were used in Glauber calculations to determine the values of the number of nucleon-nucleon collisions in each centrality class, N-coll, and these were found to give significantly different Ncoll values. Results using N-coll values from both deformed Woods-Saxon distributions are presented. The measured ratios show that the J/psi suppression, relative to binary collision scaling, is similar in U + U and Au + Au for peripheral and midcentral collisions, but that J/psi show less suppression for the most central U + U collisions. The results are consistent with a picture in which, for central collisions, increase in the J/psi yield due to c (c) over bar coalescence becomes more important than the decrease in yield due to increased energy density. For midcentral collisions, the conclusions about the balance between c (c) over bar coalescence and suppression depend on which deformed Woods-Saxon distribution is used to determine N-coll.</P>