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## ‣ Longitudinal and transverse spin asymmetries for inclusive jet production at mid-rapidity in polarized p+p collisions at root s=200 GeV

Adamczyk, L.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alakhverdyants, A. V.; Alekseev, I.; Alford, J.; Anderson, B. D.; Anson, C. D.; Arkhipkin, D.; Aschenauer, E.; Averichev, G. S.; Balewski, J.; Banerjee, A.; Barnovska, Z.; Beavis, D. R.; Bellwied
Fonte: AMER PHYSICAL SOC; COLLEGE PK Publicador: AMER PHYSICAL SOC; COLLEGE PK
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.93798%
We report STAR measurements of the longitudinal double-spin asymmetry A(LL), the transverse singlespin asymmetry A(N), and the transverse double-spin asymmetries A(Sigma) and A(TT) for inclusive jet production at mid-rapidity in polarized p + p collisions at a center-of-mass energy of root s = 200 GeV. The data represent integrated luminosities of 7.6 pb(-1) with longitudinal polarization and 1.8 pb(-1) with transverse polarization, with 50%-55% beam polarization, and were recorded in 2005 and 2006. No evidence is found for the existence of statistically significant jet A(N), A(Sigma), or A(TT) at mid-rapidity. Recent model calculations indicate the A(N) results may provide new limits on the gluon Sivers distribution in the proton. The asymmetry A(LL) significantly improves the knowledge of gluon polarization in the nucleon.; Offices of NP and HEP within the U.S. DOE Office of Science; Offices of NP and HEP within the U.S. DOE Office of Science; U.S. NSF; U.S. NSF; BMBF of Germany; BMBF of Germany; CNRS/IN2P3, RA, RPL; CNRS/IN2P3, RA, RPL; EMN of France; EMN of France; EPSRC of the United Kingdom; EPSRC of the United Kingdom; FAPESP of Brazil; FAPESP of Brazil; Russian Ministry of Education and Science; Russian Ministry of Education and Science; Ministry of Education and the NNSFC of China; Ministry of Education and the NNSFC of China; IRP and GA of the Czech Republic; IRP and GA of the Czech Republic; FOM of the Netherlands; FOM of the Netherlands; DAE; DAE; DST; DST; CSIR of the Government of India; CSIR of the Government of India; Swiss NSF; Swiss NSF; Polish State Committee for Scientific Research; Polish State Committee for Scientific Research; SRDA of Slovakia; SRDA of Slovakia; Korea Science and Engineering Foundation; Korea Science and Engineering Foundation; Renaissance Technologies Corporation; Renaissance Technologies Corporation; RCF; RCF; NERSC Center; NERSC Center

## ‣ Di-electron spectrum at mid-rapidity in p+p collisions at root s=200 GeV

Adamczyk, L.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alakhverdyants, A. V.; Alekseev, I.; Alford, J.; Anderson, B. D.; Anson, C. D.; Arkhipkin, D.; Aschenauer, E.; Averichev, G. S.; Balewski, J.; Banerjee, A.; Barnovska, Z.; Beavis, D. R.; Bellwied
Fonte: AMER PHYSICAL SOC; COLLEGE PK Publicador: AMER PHYSICAL SOC; COLLEGE PK
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.93798%
We report on the mid-rapidity mass spectrum of di-electrons and cross sections of pseudoscalar and vector mesons via e(+) e(-) decays, from root s = 200 GeV p + p collisions, measured by the large-acceptance experiment STAR at the Relativistic Heavy Ion Collider. The ratio of the di-electron continuum to the combinatorial background is larger than 10% over the entire mass range. Simulations of di-electrons from light-meson decays and heavy-flavor decays (charmonium and open charm correlation) are found to describe the data. The extracted omega -> e(+) e(-) invariant yields are consistent with previous measurements. The mid-rapidity yields (dN/dy) of phi and J/psi are extracted through their di-electron decay channels and are consistent with the previous measurements of phi -> K+ K- and J/psi -> e(+) e(-). Our results suggest a new upper limit of the branching ratio of the eta -> e(+) e(-) of 1.7 x 10(-5) at the 90% confidence level.; RHIC Operations Group; RHIC Operations Group; RCF at BNL; RCF at BNL; NERSC Center at LBNL; NERSC Center at LBNL; Open Science Grid consortium; Open Science Grid consortium; Offices of Nuclear Physics and High Energy Physics within the US Department of Energy Office of Science; Offices of Nuclear Physics and High Energy Physics within the US Department of Energy Office of Science; US NSF; U.S. NSF; Sloan Foundation; Sloan Foundation; DFG cluster of excellence Origin and Structure of the Universe of Germany; DFG cluster of excellence "Origin and Structure of the Universe" of Germany; CNRS/IN2P3; CNRS/IN2P3; FAPESP CNPq of Brazil; FAPESP CNPq of Brazil; Ministry of Education and Science of the Russian Federation; Ministry of Education and Science of the Russian Federation; NNSFC; NNSFC; CAS; CAS; MoST; MoST; MoE of China; MoE of China; GA of the Czech Republic; GA of the Czech Republic; FOM; FOM; NWO of the Netherlands; NWO of the Netherlands; DAE; DAE; DST; DST; CSIR of India; CSIR of India; Polish Ministry of Science and Higher Education; Polish Ministry of Science and Higher Education; Korea Research Foundation; Korea Research Foundation; Ministry of Science...

## ‣ Longitudinal and transverse spin asymmetries for inclusive jet production at mid-rapidity in polarized p+p collisions at root s=200 GeV

Adamczyk, L.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alakhverdyants, A. V.; Alekseev, I.; Alford, J.; Anderson, B. D.; Anson, C. D.; Arkhipkin, D.; Aschenauer, E.; Averichev, G. S.; Balewski, J.; Banerjee, A.; Barnovska, Z.; Beavis, D. R.; Bellwied
Fonte: Amer Physical Soc; College Pk Publicador: Amer Physical Soc; College Pk
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.93798%
We report STAR measurements of the longitudinal double-spin asymmetry A(LL), the transverse singlespin asymmetry A(N), and the transverse double-spin asymmetries A(Sigma) and A(TT) for inclusive jet production at mid-rapidity in polarized p + p collisions at a center-of-mass energy of root s = 200 GeV. The data represent integrated luminosities of 7.6 pb(-1) with longitudinal polarization and 1.8 pb(-1) with transverse polarization, with 50%-55% beam polarization, and were recorded in 2005 and 2006. No evidence is found for the existence of statistically significant jet A(N), A(Sigma), or A(TT) at mid-rapidity. Recent model calculations indicate the A(N) results may provide new limits on the gluon Sivers distribution in the proton. The asymmetry A(LL) significantly improves the knowledge of gluon polarization in the nucleon.

## ‣ Di-electron spectrum at mid-rapidity in p+p collisions at root s=200 GeV

Adamczyk, L.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alakhverdyants, A. V.; Alekseev, I.; Alford, J.; Anderson, B. D.; Anson, C. D.; Arkhipkin, D.; Aschenauer, E.; Averichev, G. S.; Balewski, J.; Banerjee, A.; Barnovska, Z.; Beavis, D. R.; Bellwied
Fonte: Amer Physical Soc; College Pk Publicador: Amer Physical Soc; College Pk
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.93798%
We report on the mid-rapidity mass spectrum of di-electrons and cross sections of pseudoscalar and vector mesons via e(+) e(-) decays, from root s = 200 GeV p + p collisions, measured by the large-acceptance experiment STAR at the Relativistic Heavy Ion Collider. The ratio of the di-electron continuum to the combinatorial background is larger than 10% over the entire mass range. Simulations of di-electrons from light-meson decays and heavy-flavor decays (charmonium and open charm correlation) are found to describe the data. The extracted omega -> e(+) e(-) invariant yields are consistent with previous measurements. The mid-rapidity yields (dN/dy) of phi and J/psi are extracted through their di-electron decay channels and are consistent with the previous measurements of phi -> K+ K- and J/psi -> e(+) e(-). Our results suggest a new upper limit of the branching ratio of the eta -> e(+) e(-) of 1.7 x 10(-5) at the 90% confidence level.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

## ‣ Energy and centrality dependence of mid-rapidity charged particle multiplicity in relativistic heavy-ion collisions

Decowski, MichaÅ Patrick, 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 200 p.; 14211807 bytes; 14211563 bytes; application/pdf; application/pdf
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The properties of quantum chromodynamics (QCD), the modern theory of the strong interaction, can be investigated through the study of relativistic nucleus-nucleus collisions. Recently, the Relativistic Heavy-Ion Collider (RHIC) was completed and started taking data at ten times higher center-of-mass energies than the previous most energetic heavy-ion collisions. This thesis presents some of the first measurements at RHIC from any experiment. The PHOBOS detector is used to measure the charged particle pseudo-rapidity density at mid-rapidity (i.e., in [eta] < 1) as a function of collision energy and centrality. The multiplicity is measured by counting short tracks in the silicon spectrometer; the centrality measurement uses two scintillator detectors covering 3 < [eta] < 4.5. The charged particle multiplicity at mid-rapidity for the 6% most central collisions is 379 +/- 9(stat.) +/- 42(syst.), 555 +/- 3(stat.) +/- 35(syst.) and 661 +/- 4(stat.) +/- 40(syst.) for [the square root of] SNN=56 GeV, 130 GeV and 200 GeV respectively. The charged particle multiplicity is compared to results obtained in heavy-ion experiments at lower energies and to results obtained in pp(pÌ) collisions. When normalizing the multiplicity to the number of participant pairs...

## ‣ Di-electron spectrum at mid-rapidity in p + p collisions at √ s = 200 GeV

STAR Collaboration; Butterworth, J.; Eppley, J.; Geurts, F.; Llope, W.J.; McDonald, D.; Yepes, P.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.93798%
We report on the mid-rapidity mass spectrum of di-electrons and cross sections of pseudoscalar and vector mesons via e + e − decays, from √ s = 200 GeV p + p collisions, measured by the large-acceptance experiment STAR at the Relativistic Heavy Ion Collider. The ratio of the di-electron continuum to the combinatorial background is larger than 10% over the entire mass range. Simulations of di-electrons from light-meson decays and heavy-flavor decays (charmonium and open charm correlation) are found to describe the data. The extracted ω → e + e − invariant yields are consistent with previous measurements. The mid-rapidity yields (dN/dy) of φ and J/ψ are extracted through their di-electron decay channels and are consistent with the previous measurements of φ → K + K − and J/ψ → e + e −. Our results suggest a new upper limit of the branching ratio of the η → e + e − of 1.7 × 10−5 at the 90% confidence level.

## ‣ Di-electron spectrum at mid-rapidity in p+p collisions at √s=200 GeV

STAR Collaboration; Butterworth, J.; Eppley, G.; Geurts, F.; Llope, W.J.; McDonald, D.; Roberts, J.B.; Xin, K.; Yepes, P.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.93798%
We report on the mid-rapidity mass spectrum of di-electrons and cross sections of pseudoscalar and vector mesons via e+e− decays, from √s=200 GeV p+p collisions, measured by the large-acceptance experiment STAR at the Relativistic Heavy Ion Collider. The ratio of the di-electron continuum to the combinatorial background is larger than 10% over the entire mass range. Simulations of di-electrons from light-meson decays and heavy-flavor decays (charmonium and open charm correlation) are found to describe the data. The extracted ω→e+e− invariant yields are consistent with previous measurements. The mid-rapidity yields (dN/dy) of φ and J/ψ are extracted through their di-electron decay channels and are consistent with the previous measurements of φ→K+K− and J/ψ→e+e−. Our results suggest a new upper limit of the branching ratio of the η→e+e− of 1.7×10−5 at the 90% confidence level.

## ‣ Longitudinal and transverse spin asymmetries for inclusive jet production at mid-rapidity in polarized p+p collisions at √s=200  GeV

STAR Collaboration; Butterworth, J.; Eppley, G.; Geurts, F.; Llope, W.J.; McDonald, D.; Roberts, J.B.; Xin, K.; Yepes, P.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.93798%
We report STAR measurements of the longitudinal double-spin asymmetry ALL, the transverse single-spin asymmetry AN, and the transverse double-spin asymmetries AΣ and ATT for inclusive jet production at mid-rapidity in polarized p+p collisions at a center-of-mass energy of √s=200  GeV. The data represent integrated luminosities of 7.6  pb−1 with longitudinal polarization and 1.8  pb−1 with transverse polarization, with 50%–55% beam polarization, and were recorded in 2005 and 2006. No evidence is found for the existence of statistically significant jet AN, AΣ, or ATT at mid-rapidity. Recent model calculations indicate the AN results may provide new limits on the gluon Sivers distribution in the proton. The asymmetry ALL significantly improves the knowledge of gluon polarization in the nucleon.

## ‣ Measurement of prompt J/psi and beauty hadron production cross sections at mid-rapidity in pp collisions at root s=7 TeV

Fonte: SPRINGER; NEW YORK Publicador: SPRINGER; NEW YORK
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at root s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L-int = 5.6 nb(-1). The fraction of J/psi from the decay of long-lived beauty hadrons was determined for J/psi candidates with transverse momentum p(t) > 1,3 GeV/c and rapidity vertical bar y vertical bar < 0.9. The cross section for prompt J/psi mesons, i.e. directly produced J/psi and prompt decays of heavier charmonium states such as the psi(2S) and chi(c) resonances, is sigma(prompt J/psi) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 8.3 +/- 0.8(stat.) +/- 1.1 (syst.)(-1.4)(+1.5) (syst. pol.) mu b. The cross section for the production of b-hadrons decaying to J/psi with p(t) > 1.3 GeV/c and vertical bar y vertical bar < 0.9 is a sigma(J/psi <- hB) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 1.46 +/- 0.38 (stat.)(-0.32)(+0.26) (syst.) mu b. The results are compared to QCD model predictions. The shape of the p(t) and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the b (b) over bar pair total cross section and d sigma/dy at mid-rapidity.; Calouste Gulbenkian Foundation from Lisbon and Swiss Fonds Kidagan...

## ‣ Measurement of prompt J/psi and beauty hadron production cross sections at mid-rapidity in pp collisions at root s=7 TeV

Fonte: Springer; New York Publicador: Springer; New York
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
48.06546%
The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at root s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L-int = 5.6 nb(-1). The fraction of J/psi from the decay of long-lived beauty hadrons was determined for J/psi candidates with transverse momentum p(t) > 1,3 GeV/c and rapidity vertical bar y vertical bar < 0.9. The cross section for prompt J/psi mesons, i.e. directly produced J/psi and prompt decays of heavier charmonium states such as the psi(2S) and chi(c) resonances, is sigma(prompt J/psi) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 8.3 +/- 0.8(stat.) +/- 1.1 (syst.)(-1.4)(+1.5) (syst. pol.) mu b. The cross section for the production of b-hadrons decaying to J/psi with p(t) > 1.3 GeV/c and vertical bar y vertical bar < 0.9 is a sigma(J/psi <- hB) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 1.46 +/- 0.38 (stat.)(-0.32)(+0.26) (syst.) mu b. The results are compared to QCD model predictions. The shape of the p(t) and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the b (b) over bar pair total cross section and d sigma/dy at mid-rapidity.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

## ‣ Measurement of prompt J/psi and beauty hadron production cross sections at mid-rapidity in pp collisions at sqrt(s) = 7 TeV

The ALICE Collaboration
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
48.151816%
The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at sqrt{s}=7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L_int = 5.6nb-1. The fraction of J/psi from the decay of long-lived beauty hadrons was determined for J/psi candidates with transverse momentum p_t>1.3 GeV/c and rapidity |y|<0.9. The cross section for prompt J/psi mesons, i.e. directly produced J/psi and prompt decays of heavier charmonium states such as the Psi(2S) and Csi_c resonances, is sigma_prompt-J/psi(pt > 1.3 GeV/c, |y| < 0.9) = 8.3 +- 0.8(stat.) +- 1.1(syst.) + 1.5 - 1.4(syst. pol.) micro barn. The cross section for the production of b-hadrons decaying to J/psi with p_t>1.3 GeV/c and |y|<0.9 is sigma_{J/psi<-h_B} = 1.46 +- 0.38(stat.) + 0.26 -0.32(syst.) micro barn. The results are compared to QCD model predictions. The shape of the p_t and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the b-bbar pair total cross section and dsigma/dy at mid-rapidity.; Comment: The most important modification with respect to v1 is a correction factor that is applied to all cross section values, which comes from the Erratum to "K. Aamodt et al. (ALICE Collaboration)...

## ‣ Jet-like correlations between Forward- and Mid- rapidity in p+p, d+Au and Au+Au collisions from STAR at 200 GeV

Molnar, Levente
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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In this proceedings we present STAR measurements of two particle azimuthal correlations between trigger particles at mid-rapidity ($|\eta|<$ 1) and associated particles at forward rapidities (2.7 $<|\eta|<$ 3.9) in p+p, d+Au and Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV. Two particle azimuthal correlations between a mid-rapidity trigger particle and forward-rapidity associated particles preferably probe large-x quarks scattered off small-x gluons in RHIC collisions. Comparison of the separate d- and Au-side measurements in d+Au collisions may potentially probe gluon saturation and the presence of Color Glass Condensate. In Au+Au collisions quark energy loss can be probed at large rapidities, which may be different from gluon energy loss measured at mid-rapidity.; Comment: Quark Matter 06 Conference proceedings, submitted to Journal of Phys. G

## ‣ Proton and Antiproton Distributions at Mid-Rapidity in Proton-Nucleus and Sulphur-Nucleus Collisions

NA44 Collaboration; al, I. G. Bearden et
Tipo: Artigo de Revista Científica
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Experiment NA44 has measured proton and antiproton distributions at mid-rapidity in sulphur and proton collisions with nuclear targets at 200 and 450 GeV/c per nucleon respectively. The inverse slopes of transverse mass distributions increase with system size for both protons and antiprotons but are slightly lower for antiprotons. this could happen if antiprotons are annihilated in the nuclear medium. The antiproton yield increases with system size and centrality and is largest at mid-rapdity. The proton yield also increases with system size and centrality, but decreases from backward rapidity to midrapidity. The stopping of protons at these energies lies between the full stopping and nuclear transparency scenarios. The data are in reasonable agreement with RQMD predictions except for the antiproton yields from sulphur-nucleus collisions. PACS numbers 25.75.-q 13.85.-t 13.60.Rj; Comment: 31 pages plain latex, 12 eps figures, submitted to Phys. Rev. C 1st author changed to I. G. Bearden. Figs 11 and 12 reordered and reference 17 corrected. Fig 12 made more explicit and the corresponding discussion clarified

## ‣ Charged-particle multiplicity density at mid-rapidity in central Pb-Pb collisions at sqrt(sNN) = 2.76 TeV

ALICE collaboration; Aamodt, K.; Abelev, B.; Quintana, A. Abrahantes; Adamová, D.; Adare, A. M.; Aggarwal, M. M.; Rinella, G. Aglieri; Agocs, A. G.; Salazar, S. Aguilar; Ahammed, Z.; Masoodi, A. Ahmad; Ahmad, N.; Ahn, S. U.; Akindinov, A.; Aleksandrov, D
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
48.06546%
The first measurement of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at a centre-of-mass energy per nucleon pair sqrt(sNN) = 2.76 TeV is presented. For an event sample corresponding to the most central 5% of the hadronic cross section the pseudo-rapidity density of primary charged particles at mid-rapidity is 1584 +- 4 (stat) +- 76 (sys.), which corresponds to 8.3 +- 0.4 (sys.) per participating nucleon pair. This represents an increase of about a factor 1.9 relative to pp collisions at similar collision energies, and about a factor 2.2 to central Au-Au collisions at sqrt(sNN) = 0.2 TeV. This measurement provides the first experimental constraint for models of nucleus-nucleus collisions at LHC energies.; Comment: 10 pages (first 6 authors), 4 figures

## ‣ Mid-rapidity charge distribution in peripheral heavy ion collisions

Morawetz, Klaus; Lipavský, Pavel; Normand, Jaques; Cussol, Daniel; Colin, Jean; Tamain, Bernard
Tipo: Artigo de Revista Científica
Português
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The charge density distribution with respect to the velocity of matter produced in peripheral heavy ion reactions around Fermi energy is investigated. The experimental finding of enhancement of mid-rapidity matter shows the necessity to include correlations beyond BUU which was performed in the framework of nonlocal kinetic theory. Different theoretical improvements are discussed. While the in-medium cross section changes the number of collisions, it leaves the transferred energy almost unchanged. In contrast the nonlocal scenario changes the energy transferred during collisions and leads to an enhancement of mid-rapidity matter. The renormalisation of quasiparticle energies can be included in nonlocal scenarios and leads to a further enhancement of mid-rapidity matter distribution. This renormalisation is accompanied by a dynamical softening of the equation of state seen in longer oscillation periods of the excited compressional collective mode. We propose to include quasiparticle renormalisation by using the Pauli-rejected collisions which circumvent the problem of backflows in Landau theory. Using the maximum relative velocity of projectile and target like fragments we associate experimental events with impact parameters of the simulations. For peripheral collisions we find a reasonable agreement between experiment and theory. For more central collisions...

## ‣ Directed flow of charged particles at mid-rapidity relative to the spectator plane in Pb-Pb collisions at $\sqrt{s_\rm{NN}}$=2.76 TeV

ALICE Collaboration
Tipo: Artigo de Revista Científica
Português
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The directed flow of charged particles at mid-rapidity is measured in Pb-Pb collisions at $\sqrt{s_\rm{NN}}=2.76$ TeV relative to the collision symmetry plane defined by the spectator nucleons. A negative slope of the rapidity-odd directed flow component with approximately 3 times smaller magnitude than found at the highest RHIC energy is observed. This suggests a smaller longitudinal tilt of the initial system and disfavors the strong fireball rotation predicted for the LHC energies. The rapidity-even directed flow component is measured for the first time with spectators and found to be independent of pseudorapidity with a sign change at transverse momenta $p_{\rm T}$ between $1.2$ and $1.7$ GeV/$c$. Combined with the observation of a vanishing rapidity-even $p_{\rm T}$ shift along the spectator deflection this is strong evidence for dipole-like initial density fluctuations in the overlap zone of the nuclei. Similar trends in the rapidity-even directed flow and the estimate from two-particle correlations at mid-rapidity, which is larger by about a factor of 40, indicate a weak correlation between fluctuating participant and spectator symmetry planes. These observations open new possibilities for investigation of the initial conditions in heavy-ion collisions with spectator nucleons.; Comment: 17 pages...

## ‣ J$\psi$ nuclear modification factor at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{NN}}=$2.76 TeV

Arsene, Ionut-Cristian; Collaboration, for the ALICE
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We report on the J$\psi$ nuclear modification factor $R_{\rm AA}$ at mid-rapidity ($|y|<0.9$) in Pb-Pb collisions at $\sqrt{s_{NN}}=$2.76 TeV measured by ALICE. J$\psi$ candidates are reconstructed using their $e^+e^-$ decay channel. The kinematical coverage extends to zero transverse momentum allowing the measurement of integrated cross sections. We show the centrality dependence of the J$\psi$ $R_{\rm AA}$ at mid-rapidity compared to the results from PHENIX at mid-rapidity and ALICE results at forward-rapidity. We also discuss comparisons to calculations from theoretical models.; Comment: Proceedings for the Quark Matter Conference, Washington, 13-18 August 2012. To be published in Nuclear Physics A

## ‣ Forward- and Mid-Rapidity Jet-like correlations

Wang, Fuqiang; Collaboration, for the STAR
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
48.35986%
Mid-rapidity azimuthal correlations probe di-jets originating mainly from gluon-gluon hard-scattering. Measurements of such correlations have revealed significant (gluon-)jet modification in central Au+Au collisions. Azimuthal correlations of hadrons at forward rapidity with a mid-rapidity high-$\pt$ hadron, on the other hand, probe asymmetric partonic scatterings involving large-x quarks and small-x gluons. We present preliminary results from STAR on correlations of charged hadrons at forward rapidity in the forward TPCs ($2.7<|\eta|<3.9$, $\pt<2$ GeV/$c$) with high-$\pt$ charged hadrons at mid-rapidity from the main TPC ($|\eta|<1$, $\pt>3$ GeV/$c$) in $pp$, d+Au, and Au+Au collisions at $\snn=200$ GeV. The implications of the results for small-x gluon distributions (Color Glass Condensate formation) and the energy loss of quark jets at forward rapidity in nuclear medium are discussed. %Their measurements in d+Au collisions, separately at the d-side and the Au-side, may be sensitive to Color Glass Condensate in the Au-nucleus. Their measurements in Au+Au collisions may probe quark-jet modification in nuclear medium.; Comment: Invited talk at the XIth International Workshop on Correlation and Fluctuation in Multiparticle Production...

## ‣ Mid-rapidity anti-proton to proton ratio from Au+Au collisions at $\sqrt{s_{NN}} = 130$ GeV

Tipo: Artigo de Revista Científica
We report results on the ratio of mid-rapidity anti-proton to proton yields in Au+Au collisions at $\rts = 130$ GeV per nucleon pair as measured by the STAR experiment at RHIC. Within the rapidity and transverse momentum range of $|y|<0.5$ and 0.4 \$