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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>
PHENIX Collaboration,Afanasiev, S.,Aidala, C.,Ajitanand, N.N.,Akiba, Y.,Alexander, J.,Al-Jamel, A.,Aoki, K.,Aphecetche, L.,Armendariz, R.,Aronson, S.H.,Averbeck, R.,Awes, T.C.,Azmoun, B.,Babintsev, V. North-Holland Pub. Co 2009 Physics letters: B Vol.679 No.4
We present the first measurement of photoproduction of J/ψ and of two-photon production of high-mass e<SUP>+</SUP>e<SUP>-</SUP> pairs in electromagnetic (or ultra-peripheral) nucleus-nucleus interactions, using Au+Au data at s<SUB>NN</SUB>=200 GeV. The events are tagged with forward neutrons emitted following Coulomb excitation of one or both Au<SUP>@</SUP>? nuclei. The event sample consists of 28 events with m<SUB>e<</SUB>SUP><SUB><</SUB>/SUP>+<SUB>e<</SUB>SUP><SUB><</SUB>/SUP>->2 GeV/c<SUP>2</SUP> with zero like-sign background. The measured cross sections at midrapidity of dσ/dy(J/ψ+Xn,y=0)=76+/-33(stat)+/-11(syst) μb and d<SUP>2</SUP>σ/dmdy(e<SUP>+</SUP>e<SUP>-</SUP>+Xn,y=0)=86+/-23(stat)+/-16(syst) μb/(GeV/c<SUP>2</SUP>) for m<SUB>e<</SUB>SUP><SUB><</SUB>/SUP>+<SUB>e<</SUB>SUP><SUB><</SUB>/SUP>-@?[2.0,2.8] GeV/c<SUP>2</SUP> have been compared and found to be consistent with models for photoproduction of J/ψ and QED based calculations of two-photon production of e<SUP>+</SUP>e<SUP>-</SUP> pairs.
Aidala, C.,Akiba, Y.,Alfred, M.,Andrieux, V.,Aoki, K.,Apadula, N.,Asano, H.,Ayuso, C.,Azmoun, B.,Babintsev, V.,Bagoly, A.,Bandara, N. S.,Barish, K. N.,Bathe, S.,Bazilevsky, A.,Beaumier, M.,Belmont, R. American Physical Society 2018 Physical review letters Vol.120 No.2
<P>During 2015, the Relativistic Heavy Ion Collider (RHIC) provided collisions of transversely polarized protons with Au and Al nuclei for the first time, enabling the exploration of transverse-single-spin asymmetries with heavy nuclei. Large single-spin asymmetries in very forward neutron production have been previously observed in transversely polarized p+p collisions at RHIC, and the existing theoretical framework that was successful in describing the single-spin asymmetry in p+p collisions predicts only a moderate atomic-mass-number (A) dependence. In contrast, the asymmetries observed at RHIC in p+A collisions showed a surprisingly strong A dependence in inclusive forward neutron production. The observed asymmetry in p+Al collisions is much smaller, while the asymmetry in p+Au collisions is a factor of 3 larger in absolute value and of opposite sign. The interplay of different neutron production mechanisms is discussed as a possible explanation of the observed A dependence.</P>
Aidala, C.,Akiba, Y.,Alfred, M.,Andrieux, V.,Aoki, K.,Apadula, N.,Asano, H.,Ayuso, C.,Azmoun, B.,Babintsev, V.,Bandara, N. S.,Barish, K. N.,Bathe, S.,Bazilevsky, A.,Beaumier, M.,Belmont, R.,Berdnikov, American Physical Society 2017 Physical Review C Vol.95 No.3
<P>We present measurements of long-range angular correlations and the transverse momentum dependence of elliptic flow v(2) in high-multiplicity p + Au collisions at root S-NN = 200 GeV. A comparison of these results to previous measurements in high-multiplicity d + Au and He-3+Au collisions demonstrates a relation between v(2) and the initial collision eccentricity epsilon(2), suggesting that the observed momentum-space azimuthal anisotropies in these small systems have a collective origin and reflect the initial geometry. Good agreement is observed between the measured v(2) and hydrodynamic calculations for all systems, and an argument disfavoring theoretical explanations based on initial momentum-space domain correlations is presented. The set of measurements presented here allows us to leverage the distinct intrinsic geometry of each of these systems to distinguish between different theoretical descriptions of the long-range correlations observed in small collision systems.</P>
Cross section forbb¯production via dielectrons ind+ Au collisions at<sub>sNN</sub>=200GeV
Adare, A.,Aidala, C.,Ajitanand, N. N.,Akiba, Y.,Al-Bataineh, H.,Alexander, J.,Angerami, A.,Aoki, K.,Apadula, N.,Aramaki, Y.,Atomssa, E. T.,Averbeck, R.,Awes, T. C.,Azmoun, B.,Babintsev, V.,Bai, M.,Bak American Physical Society 2015 PHYSICAL REVIEW C - Vol.91 No.1