Beam-energy Dependence Of Charge Balance Functions From Au + Au Collisions At Energies Available At The Bnl Relativistic Heavy Ion Collider

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Balance functions have been measured in terms of relative pseudorapidity (Δη) for charged particle pairs at the BNL Relativistic Heavy Ion Collider from Au + Au collisions at sNN=7.7GeV to 200 GeV using the STAR detector. These results are compared with balance functions measured at the CERN Large Hadron Collider from Pb + Pb collisions at sNN=2.76TeV by the ALICE Collaboration. The width of the balance function decreases as the collisions become more central and as the beam energy is increased. In contrast, the widths of the balance functions calculated using shuffled events show little dependence on centrality or beam energy and are larger than the observed widths. Balance function widths calculated using events generated by UrQMD are wider than the measured widths in central collisions and show little centrality dependence. The measured widths of the balance functions in central collisions are consistent with the delayed hadronization of a deconfined quark gluon plasma (QGP). The narrowing of the balance function in central collisions at sNN=7.7 GeV implies that a QGP is still being created at this relatively low energy. © 2016 American Physical Society.942CNPq, Conselho Nacional de Desenvolvimento Científico e TecnológicoMinistry of Education and Science of the Russian FederationMOE, Ministry of Education of the People's Republic of ChinaMOST, Ministry of Science and Technology of the People's Republic of ChinaNRF-2012004024, National Research FoundationNSF, National Stroke FoundationConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

J/ψ Production At Low Pt In Au+au And Cu+cu Collisions At Snn =200 Gev With The Star Detector

The J/ψ pT spectrum and nuclear modification factor (RAA) are reported for pT<5GeV/c and |y|<1 from 0% to 60% central Au+Au and Cu+Cu collisions at sNN=200GeV at STAR. A significant suppression of pT-integrated J/ψ production is observed in central Au+Au events. The Cu+Cu data are consistent with no suppression, although the precision is limited by the available statistics. RAA in Au+Au collisions exhibits a strong suppression at low transverse momentum and gradually increases with pT. The data are compared to high-pT STAR results and previously published BNL Relativistic Heavy Ion Collider results. Comparing with model calculations, it is found that the invariant yields at low pT are significantly above hydrodynamic flow predictions but are consistent with models that include color screening and regeneration. © 2014 American Physical Society.902CNRS/IN2P3; NSF; Arthritis National Research Foundation; NRF-2012004024; ANRF; Arthritis National Research FoundationMatsui, T., Satz, H., (1986) Phys Lett. B, 178, p. 416. , PYLBAJ 0370-2693 10.1016/0370-2693(86)91404-8Digal, S., Petreczky, P., Satz, H., (2001) Phys. Rev. D, 64, p. 094015. , 0556-2821 10.1103/PhysRevD.64.094015Karsch, F., Kharzeev, D., Satz, H., Sequential charmonium dissociation (2006) Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 637 (1-2), pp. 75-80. , DOI 10.1016/j.physletb.2006.03.078, PII S037026930600445XBraun-Munzinger, P., Stachel, J., The quest for the quark-gluon plasma (2007) Nature, 448 (7151), pp. 302-309. , DOI 10.1038/nature06080, PII NATURE06080Abreu, M.C., (1999) Phys. Lett. B, 449, p. 128. , (NA38 Collaboration),. PYLBAJ 0370-2693 10.1016/S0370-2693(99)00057-XAbreu, M.C., (1997) Phys. Lett. B, 410, p. 327. , (NA50 Collaboration),. PYLBAJ 0370-2693 10.1016/S0370-2693(97)00914-3Arnaldi, R., Banicz, K., Castor, J., Chaurand, B., Cicalo, C., Colla, A., Cortese, P., Wohri, H.K., J/ψ production in indium-indium collisions at 158GeV/nucleon (2007) Physical Review Letters, 99 (13), p. 132302. , http://oai.aps.org/oai?verb=GetRecord&Identifier=oai:aps.org: PhysRevLett.99.132302&metadataPrefix=oai_apsmeta_2, DOI 10.1103/PhysRevLett.99.132302Adare, A., Afanasiev, S., Aidala, C., Ajitanand, N.N., Akiba, Y., Al-Bataineh, H., Alexander, J., Al-Jamel, A., J/ψ production versus centrality, transverse momentum, and rapidity in Au+Au collisions at s NN=200 GeV (2007) Physical Review Letters, 98 (23), p. 232301. , http://oai.aps.org/oai?verb=GetRecord&Identifier=oai:aps.org: PhysRevLett.98.232301&metadataPrefix=oai_apsmeta_2, DOI 10.1103/PhysRevLett.98.232301Adamczyk, L., (2013) Phys. Lett. B, 722, p. 55. , (STAR Collaboration),. PYLBAJ 0370-2693 10.1016/j.physletb.2013.04.010Abelev, B., (2012) Phys. Rev. Lett., 109, p. 072301. , (ALICE Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.109.072301Chatrchyan, S., (2012) J. High Energy Phys., (5), p. 063. , (CMS Collaboration),. JHEPFG 1029-8479 10.1007/JHEP05(2012)063Braun-Munzinger, P., Stachel, J., (2000) Phys. Lett. B, 490, p. 196. , PYLBAJ 0370-2693 10.1016/S0370-2693(00)00991-6Grandchamp, L., Rapp, R., (2002) Nucl. Phys. A, 709, p. 415. , NUPABL 0375-9474 10.1016/S0375-9474(02)01027-8Gavin, S., Vogt, R., (1996) Nucl. Phys. A, 610, p. 442. , NUPABL 0375-9474 10.1016/S0375-9474(96)00376-4Capella, A., (1997) Phys. Lett. B, 393, p. 431. , PYLBAJ 0370-2693 10.1016/S0370-2693(96)01650-4Karsch, F., Petronzio, P., (1988) Z. Phys. C, 37, p. 627. , ZPCFD2 0170-9739 10.1007/BF01549724Adare, A., (2012) Phys. Rev. D, 85, p. 092004. , (PHENIX Collaboration),. 10.1103/PhysRevD.85.092004Charm, beauty and charmonium production at HERA-B (2005) European Physical Journal C, 43 (1-4), pp. 179-186. , DOI 10.1140/epjc/s2005-02308-8Vogt, R., Shadowing and absorption effects on J/ψ production in da collisions (2005) Physical Review C - Nuclear Physics, 71 (5), pp. 1-11. , http://oai.aps.org/oai/?verb=ListRecords&metadataPrefix= oai_apsmeta_2&set=journal:PRC:71, DOI 10.1103/PhysRevC.71.054902, 054902Gavin, S., Gyulassy, M., (1988) Phys. Lett. B, 214, p. 241. , PYLBAJ 0370-2693 10.1016/0370-2693(88)91476-1Noble, J.V., (1981) Phys. Rev. Lett., 46, p. 412. , PRLTAO 0031-9007 10.1103/PhysRevLett.46.412Tram, V., Arleo, F., (2009) Eur. Phys. J. C, 61, p. 847. , EPCFFB 1434-6044 10.1140/epjc/s10052-009-0864-yAlde, D., Baer, H., Carey, T., Garvey, G., Klein, A., (1991) Phys. Rev. Lett., 66, p. 133. , PRLTAO 0031-9007 10.1103/PhysRevLett.66.133Leitch, M., (1992) Nucl. Phys. A, 544, p. 197. , (E772 and E789 Collaboration),. NUPABL 0375-9474 10.1016/0375-9474(92) 90574-4Leitch, M., (2000) Phys. Rev. Lett., 84, p. 3256. , (NuSea Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.84.3256Alessandro, B., Alexa, C., Arnaldi, R., Atayan, M., Baglin, C., Baldit, A., Beole, S., Willis, N., Charmonium production and nuclear absorption in p-A interactions at 450 GeV (2004) European Physical Journal C, 33 (1), pp. 31-40. , DOI 10.1140/epjc/s2003-01539-yAlessandro, B., Alexa, C., Arnaldi, R., Atayan, M., Beole, S., Boldea, V., Bordalo, P., Wu, T., A new measurement of J/ψ suppression in Pb-Pb collisions at 158 GeV per nucleon (2005) European Physical Journal C, 39 (3), pp. 335-345. , DOI 10.1140/epjc/s2004-02107-9Arnaldi, R., (2012) Phys. Lett. B, 706, p. 263. , (NA60 Collaboration),. PYLBAJ 0370-2693 10.1016/j.physletb.2011.11.042Adare, A., (2013) Phys. Rev. C, 87, p. 034904. , (PHENIX Collaboration),. 10.1103/PhysRevC.87.034904Adare, A., (2013) Phys. Rev. Lett., 111, p. 202301. , (PHENIX Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.111.202301Adare, A., (2011) Phys. Rev. Lett., 107, p. 142301. , (PHENIX Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.107.142301Zhao, X., Rapp, R., (2010) Phys. Rev. C, 82, p. 064905. , PRVCAN 0556-2813 10.1103/PhysRevC.82.064905Adamczyk, L., (2013) Phys. Rev. Lett., 111, p. 052301. , (STAR Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.111.052301Ackermann, K.H., Adams, N., Adler, C., Ahammed, Z., Ahmad, S., Allgower, C., Amonett, J., Harris, J.W., STAR detector overview (2003) Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 499 (2-3), pp. 624-632. , DOI 10.1016/S0168-9002(02)01960-5Llope, W.J., (2004) Nucl. Instrum. Methods Phys. Res., Sect. A, 522, p. 252. , NIMAER 0168-9002 10.1016/j.nima.2003.11.414Adler, C., Denisov, A., Garcia, E., Murray, M., Strobele, H., White, S., The RHIC zero-degree calorimeters (2003) Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 499 (2-3), pp. 433-436. , DOI 10.1016/j.nima.2003.08.112Llope, W., (2012) Nucl. Instrum. Methods Phys. Res., Sect. A, 661, pp. S110. , (Suppl. 1),. NIMAER 0168-9002 10.1016/j.nima.2010.07.086Reed, R., (2010) J. Phys.: Conf. Ser., 219, p. 03020. , 1742-6596 10.1088/1742-6596/219/3/032020Beringer, J., (2012) Phys. Rev. D, 86, p. 010001. , (Particle Data Group),. 10.1103/PhysRevD.86.010001Beddo, M., Bielick, E., Fornek, T., Guarino, V., Hill, D., Krueger, K., LeCompte, T., Suaide, A.A.P., The STAR barrel electromagnetic calorimeter (2003) Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 499 (2-3), pp. 725-739. , DOI 10.1016/S0168-9002(02)01970-8Miller, M.L., Reygers, K., Sanders, S.J., Steinberg, P., (2007) Annu. Rev. Nucl. Part. Sci., 57, p. 205. , ARPSDF 0163-8998 10.1146/annurev.nucl.57.090506.123020Abelev, B.I., (2009) Phys. Lett. B, 673, p. 183. , (STAR Collaboration),. PYLBAJ 0370-2693 10.1016/j.physletb.2009.02.037Bichsel, H., A method to improve tracking and particle identification in TPCs and silicon detectors (2006) Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 562 (1), pp. 154-197. , DOI 10.1016/j.nima.2006.03.009, PII S0168900206005353Shao, M., (2006) Nucl. Instrum. Methods Phys. Res., Sect. A, 558, p. 419. , NIMAER 0168-9002 10.1016/j.nima.2005.11.251Abelev, B.I., (2009) Phys. Rev. C, 79, p. 034909. , (STAR Collaboration),. PRVCAN 0556-2813 10.1103/PhysRevC.79.034909Adamczyk, L., (STAR Collaboration), arXiv:1402.1791Spiridonov, A., arXiv:hep-ex/0510076Abelev, B.I., (2009) Phys. Rev. C, 80, p. 041902. , (STAR Collaboration),. PRVCAN 0556-2813 10.1103/PhysRevC.80.041902Tang, Z., Xu, Y., Ruan, L., Van Buren, G., Wang, F., Xu, Z., (2009) Phys. Rev. C, 79, p. 051901. , PRVCAN 0556-2813 10.1103/PhysRevC.79.051901Tang, Z., Yi, L., Ruan, L., Shao, M., Chen, H., (2013) Chin. Phys. Lett., 30, p. 031201. , CPLEEU 0256-307X 10.1088/0256-307X/30/3/031201Adare, A., (2010) Phys. Rev. D, 82, p. 012001. , (PHENIX Collaboration),. 10.1103/PhysRevD.82.012001Liu, Y., Qu, Z., Xu, N., Zhuang, P., (2009) Phys. Lett. B, 678, p. 72. , PYLBAJ 0370-2693 10.1016/j.physletb.2009.06.006Heinz, U.W., Shen, C., (private communication)Adare, A., (2008) Phys. Rev. Lett., 101, p. 122301. , (PHENIX Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.101.122301Adams, J., (2003) Phys. Rev. Lett, 91, p. 172302. , (STAR Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.91.172302Adare, A., Afanasiev, S., Aidala, C., Ajitanand, N.N., Akiba, Y., Al-Bataineh, H., Alexander, J., Aoki, K., J/ψ Production versus transverse momentum and rapidity in p+p collisions at s=200GeV (2007) Physical Review Letters, 98 (23), p. 232002. , http://oai.aps.org/oai?verb=GetRecord&Identifier=oai:aps.org: PhysRevLett.98.232002&metadataPrefix=oai_apsmeta_2, DOI 10.1103/PhysRevLett.98.232002Zhao, X., Rapp, R., (2008) Phys. Lett. B, 664, p. 253. , PYLBAJ 0370-2693 10.1016/j.physletb.2008.03.06

Measurement of longitudinal spin asymmetries for weak boson production in polarized proton-proton collisions at RHIC

We report measurements of single and double spin asymmetries for $W^{\pm}$ and $Z/\gamma^*$ boson production in longitudinally polarized $p+p$ collisions at $\sqrt{s} = 510$ GeV by the STAR experiment at RHIC. The asymmetries for $W^{\pm}$ were measured as a function of the decay lepton pseudorapidity, which provides a theoretically clean probe of the proton's polarized quark distributions at the scale of the $W$ mass. The results are compared to theoretical predictions, constrained by recent polarized DIS measurements, and show a preference for a sizable, positive up antiquark polarization in the range $0.05<x<0.2$