Publications
2011
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(2011) Physical review letters. 107, 25, 252301. Abstract[All authors]
Flow coefficients vn for n=2, 3, 4, characterizing the anisotropic collective flow in Au+Au collisions at √sNN=200GeV, are measured relative to event planes Ψn, determined at large rapidity. We report vn as a function of transverse momentum and collision centrality, and study the correlations among the event planes of different order n. The vn are well described by hydrodynamic models which employ a Glauber Monte Carlo initial state geometry with fluctuations, providing additional constraining power on the interplay between initial conditions and the effects of viscosity as the system evolves. This new constraint can serve to improve the precision of the extracted shear viscosity to entropy density ratio η/s.
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(2011) Physical Review C. 84, 5, 054912. Abstract[All authors]
Heavy quarkonia are observed to be suppressed in relativistic heavy-ion collisions relative to their production in p+p collisions scaled by the number of binary collisions. In order to determine if this suppression is related to color screening of these states in the produced medium, one needs to account for other nuclear modifications including those in cold nuclear matter. In this paper, we present new measurements from the PHENIX 2007 data set of J/ψ yields at forward rapidity (1.2
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(2011) Physical Review C. 84, 4, 044905. Abstract[All authors]
Transverse momentum spectra of electrons (pTe) from semileptonic weak decays of heavy-flavor mesons in the range of 0.3
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(2011) Physics Letters B. 703, 4, p. 428-446 Abstract[All authors]
A search for long-lived charged particles reaching the muon spectrometer is performed using a data sample of 37 pb-1 from pp collisions at √s = 7 TeV collected by the ATLAS detector at the LHC in 2010. No excess is observed above the estimated background. Stable τ over bar sleptons are excluded at 95% CL up to a mass of 136 GeV, in GMSB models with N-5 = 3 ,mmessenger = 250 TeV, sign(μ) = 1 and tan β = 5. Electroweak production of sleptons is excluded up to a mass of 110 GeV. Gluino R-hadrons in a generic interaction model are excluded up to masses of 530 GeV to 544 GeV depending on the fraction of R-hadrons produced as (g) over bar -balls.
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(2011) Physical review letters. 107, 14, 142301. Abstract[All authors]
We present measurements of J/ψ yields in d+Au collisions at √sNN=200GeV recorded by the PHENIX experiment and compare them with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/ψ rapidity (-2.2
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Design, construction, operation and performance of a Hadron Blind Detector for the PHENIX experiment(2011) Nuclear Instruments & Methods In Physics Research Section A-Accelerators Spectrometers Detectors And Associated Equipment. 646, 1, p. 35-58 Abstract[All authors]
A Hadron Blind Detector (HBD) has been developed, constructed and successfully operated within the PHENIX detector at RHIC. The HBD is a Cherenkov detector operated with pure CF4. It has a 50 cm long radiator directly coupled in a windowless configuration to a readout element consisting of a triple GEM stack, with a CsI photocathode evaporated on the top surface of the top GEM and pad readout at the bottom of the stack. This paper gives a comprehensive account of the construction, operation and in-beam performance of the detector.
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(2011) Physical Review C. 84, 2, 024904. Abstract[All authors]
Pair correlations between large transverse momentum neutral pion triggers (pT=4 - 7 GeV/c) and charged hadron partners (pT=3 - 7 GeV/c) in central (0%-20%) and midcentral (20%-60%) Au+Au collisions at √sNN=200 GeV are presented as a function of trigger orientation with respect to the reaction plane. The particles are at larger momentum than where jet shape modifications have been observed, and the correlations are sensitive to the energy loss of partons traveling through hot dense matter. An out-of-plane trigger particle produces only 26±20% of the away-side pairs that are observed opposite of an in-plane trigger particle for midcentral (20%-60%) collisions. In contrast, near-side jet fragments are consistent with no suppression or dependence on trigger orientation with respect to the reaction plane. These observations are qualitatively consistent with a picture of little near-side parton energy loss either due to surface bias or fluctuations and increased away-side parton energy loss due to a long path through the medium. The away-side suppression as a function of reaction-plane angle is shown to be sensitive to both the energy loss mechanism and the space-time evolution of heavy-ion collisions.
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(2011) Physical Review D. 84, 1, 012006. Abstract[All authors]
We report on the event structure and double helicity asymmetry (A LL) of jet production in longitudinally polarized p+p collisions at √s=200GeV. Photons and charged particles were measured by the PHENIX experiment at midrapidity |η|2GeV/c) photon in the event. Event structure, such as multiplicity, pT density and thrust in the PHENIX acceptance, were measured and compared with the results from the pythia event generator and the geant detector simulation. The shape of jets and the underlying event were well reproduced at this collision energy. For the measurement of jet ALL, photons and charged particles were clustered with a seed-cone algorithm to obtain the cluster pT sum (pTreco). The effect of detector response and the underlying events on pTreco was evaluated with the simulation. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order and perturbative quantum chromodynamics jet production cross section. For 4
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(2011) Physical Review C. 83, 6, 064903. Abstract[All authors]
Transverse momentum distributions and yields for π±, K±, p, and p in p+p collisions at √s = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). These data provide important baseline spectra for comparisons with identified particle spectra in heavy ion collisions at RHIC. We present the inverse slope parameter Tinv, mean transverse momentum pT, and yield per unit rapidity dN/dy at each energy, and compare them to other measurements at different √s in p+p and p+p collisions. We also present the scaling properties such as mT scaling and x T scaling on the pT spectra between different energies. To discuss the mechanism of the particle production in p+p collisions, the measured spectra are compared to next-to-leading-order or next-to-leading- logarithmic perturbative quantum chromodynamics calculations.
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(2011) Physical Review C. 83, 4, 044912. Abstract[All authors]
Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled p+p collisions. These measurements indicate that charm and bottom quarks interact with the hot dense matter produced in heavy-ion collisions much more than expected. Here we extend these studies to two-particle correlations where one particle is an electron from the decay of a heavy-flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interactions between heavy quarks and the matter, such as whether the modification of the away-side-jet shape seen in hadron-hadron correlations is present when the trigger particle is from heavy-meson decay and whether the overall level of away-side-jet suppression is consistent. We statistically subtract correlations of electrons arising from background sources from the inclusive electron-hadron correlations and obtain two-particle azimuthal correlations at √sNN=200 GeV between electrons from heavy-flavor decay with charged hadrons in p+p and also first results in Au+Au collisions. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to p+p collisions.
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(2011) Physical Review D. 83, 5, 052004. Abstract[All authors]
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the invariant differential cross section for production of KS0, ω, η, and φ mesons in p+p collisions at √s=200GeV. Measurements of ω and φ production in different decay channels give consistent results. New results for the ω are in agreement with previously published data and extend the measured pT coverage. The spectral shapes of all hadron transverse momentum distributions measured by PHENIX are well described by a Tsallis distribution functional form with only two parameters, n and T, determining the high-pT and characterizing the low-pT regions of the spectra, respectively. The values of these parameters are very similar for all analyzed meson spectra, but with a lower parameter T extracted for protons. The integrated invariant cross sections calculated from the fitted distributions are found to be consistent with existing measurements and with statistical model predictions.
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(2011) Nuovo Cimento della Societa Italiana di Fisica C. 34, 2, p. 109-117 Abstract
This proceeding gives the most complete review of the measurements of the ø-meson production in relativistic heavy ion and proton-proton collisions performed by the PHENIX experiment at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. The measurements of the f-meson are consistent in the analysis of various decay modes, using different techniques. The results show expected similarities when analyzed in Au + Au and Cu + Cu collision systems for the corresponding centrality classes. In other systems PHENIX observes not only the difference between the suppression of f-meson and the proton, reflecting generally different behavior between mesons and baryons, but also a significant difference in suppression of different mesons. These results are hard to explain due to the mass or quark content of the f-meson. PACS 21.65.Jk-Mesons in nuclear matter. PACS 25.75.Dw-Particle and resonance production.
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(2011) Journal Of Physics G-Nuclear And Particle Physics. 38, 2, 25002. Abstract
Based on the statistical hadronizationmodel, we obtain quantitative predictions for the relative abundances of hadron species in pp collisions at the LHC. By using the parameters of the model determined at √s = 200 GeV, and extrapolating the overall normalization from pp̄ collisions at the SPS and Tevatron, we find that the expected rapidity densities are almost grandcanonical. Therefore, at LHC the ratios between different species become essentially energy-independent, provided that the hadronization temperature TH and the strangeness suppression factor γS retain the stable values observed in the presently explored range of pp and pp̄ collisions.
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(2011) Physical review letters. 106, 6, 062001. Abstract[All authors]
Large parity-violating longitudinal single-spin asymmetries ALe +=-0.86-0.14+0.30 and ALe-=0.88-0.71+0.12 are observed for inclusive high transverse momentum electrons and positrons in polarized p+p collisions at a center-of-mass energy of √s=500GeV with the PHENIX detector at RHIC. These e± come mainly from the decay of W± and Z0 bosons, and their asymmetries directly demonstrate parity violation in the couplings of the W± to the light quarks. The observed electron and positron yields were used to estimate W ± boson production cross sections for the e± channels of σ(pp→W+X)×BR(W+→e +νe)=144.1±21.2(stat)-10.3+3.4(syst)±21. 6(norm)pb, and σ(pp→W-X)×BR(W -→e-ν̄e)=31.7±12.1(stat)-8. 2+10.1(syst)±4.8(norm)pb.
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(2011) Physical Review C. 83, 2, 024909. Abstract[All authors]
The PHENIX experiment at the Relativistic Heavy Ion Collider has performed systematic measurements of φ meson production in the K+K - decay channel at midrapidity in p+p, d+Au, Cu+Cu, and Au+Au collisions at √sNN=200GeV. Results are presented on the φ invariant yield and the nuclear modification factor RAA for Au+Au and Cu+Cu, and RdA for d+Au collisions, studied as a function of transverse momentum (1
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(2011) Physical Review D. 83, 3, 032001. Abstract[All authors]
Measurements of double-helicity asymmetries in inclusive hadron production in polarized p+p collisions are sensitive to helicity-dependent parton distribution functions, in particular, to the gluon helicity distribution, Δg. This study focuses on the extraction of the double-helicity asymmetry in η production (p→+p→→η+X), the η cross section, and the η/π0 cross section ratio. The cross section and ratio measurements provide essential input for the extraction of fragmentation functions that are needed to access the helicity-dependent parton distribution functions.