165 research outputs found
Three-Particle Correlations from Parton Cascades in Au+Au Collisions
We present a study of three-particle correlations among a trigger particle
and two associated particles in Au + Au collisions at = 200 GeV
using a multi-phase transport model (AMPT) with both partonic and hadronic
interactions. We found that three-particle correlation densities in different
angular directions with respect to the triggered particle (`center', `cone',
`deflected', `near' and `near-away') increase with the number of participants.
The ratio of `deflected' to `cone' density approaches to 1.0 with the
increasing of number of participants, which indicates that partonic Mach-like
shock waves can be produced by strong parton cascades in central Au+Au
collisions.Comment: 9 pages, 6 figures; Final version to appear in Physics Letters
Quantifying atmospheric nitrogen deposition through a nationwide monitoring network across China
A Nationwide Nitrogen Deposition Monitoring Network (NNDMN) containing 43 monitoring sites was established in China to measure gaseous NH3, NO2, and HNO3 and particulate NH4+ and NO3− in air and/or precipitation from 2010 to 2014. Wet/bulk deposition fluxes of Nr species were collected by precipitation gauge method and measured by continuous-flow analyzer; dry deposition fluxes were estimated using airborne concentration measurements and inferential models. Our observations reveal large spatial variations of atmospheric Nr concentrations and dry and wet/bulk Nr deposition. On a national basis, the annual average concentrations (1.3–47.0 μg N m−3) and dry plus wet/bulk deposition fluxes (2.9–83.3 kg N ha−1 yr−1) of inorganic Nr species are ranked by land use as urban > rural > background sites and by regions as north China > southeast China > southwest China > northeast China > northwest China > Tibetan Plateau, reflecting the impact of anthropogenic Nr emission. Average dry and wet/bulk N deposition fluxes were 20.6 ± 11.2 (mean ± standard deviation) and 19.3 ± 9.2 kg N ha−1 yr−1 across China, with reduced N deposition dominating both dry and wet/bulk deposition. Our results suggest atmospheric dry N deposition is equally important to wet/bulk N deposition at the national scale. Therefore, both deposition forms should be included when considering the impacts of N deposition on environment and ecosystem health
Partonic flow and -meson production in Au+Au collisions at = 200 GeV
We present first measurements of the -meson elliptic flow
() and high statistics distributions for different
centralities from = 200 GeV Au+Au collisions at RHIC. In
minimum bias collisions the of the meson is consistent with the
trend observed for mesons. The ratio of the yields of the to those of
the as a function of transverse momentum is consistent with a model
based on the recombination of thermal quarks up to GeV/,
but disagrees at higher momenta. The nuclear modification factor () of
follows the trend observed in the mesons rather than in
baryons, supporting baryon-meson scaling. Since -mesons are
made via coalescence of seemingly thermalized quarks in central Au+Au
collisions, the observations imply hot and dense matter with partonic
collectivity has been formed at RHIC.Comment: 6 pages, 4 figures, submit to PR
Plasma Wakefield Acceleration with a Modulated Proton Bunch
The plasma wakefield amplitudes which could be achieved via the modulation of
a long proton bunch are investigated. We find that in the limit of long bunches
compared to the plasma wavelength, the strength of the accelerating fields is
directly proportional to the number of particles in the drive bunch and
inversely proportional to the square of the transverse bunch size. The scaling
laws were tested and verified in detailed simulations using parameters of
existing proton accelerators, and large electric fields were achieved, reaching
1 GV/m for LHC bunches. Energy gains for test electrons beyond 6 TeV were found
in this case.Comment: 9 pages, 7 figure
The energy dependence of angular correlations inferred from mean- fluctuation scale dependence in heavy ion collisions at the SPS and RHIC
We present the first study of the energy dependence of angular
correlations inferred from event-wise mean transverse momentum
fluctuations in heavy ion collisions. We compare our large-acceptance
measurements at CM energies $\sqrt{s_{NN}} =$ 19.6, 62.4, 130 and 200 GeV to
SPS measurements at 12.3 and 17.3 GeV. $p_t$ angular correlation structure
suggests that the principal source of $p_t$ correlations and fluctuations is
minijets (minimum-bias parton fragments). We observe a dramatic increase in
correlations and fluctuations from SPS to RHIC energies, increasing linearly
with $\ln \sqrt{s_{NN}}$ from the onset of observable jet-related
fluctuations near 10 GeV.Comment: 10 pages, 4 figure
Measurement of Transverse Single-Spin Asymmetries for Di-Jet Production in Proton-Proton Collisions at GeV
We report the first measurement of the opening angle distribution between
pairs of jets produced in high-energy collisions of transversely polarized
protons. The measurement probes (Sivers) correlations between the transverse
spin orientation of a proton and the transverse momentum directions of its
partons. With both beams polarized, the wide pseudorapidity () coverage for jets permits separation of Sivers functions for the valence
and sea regions. The resulting asymmetries are all consistent with zero and
considerably smaller than Sivers effects observed in semi-inclusive deep
inelastic scattering (SIDIS). We discuss theoretical attempts to reconcile the
new results with the sizable transverse spin effects seen in SIDIS and forward
hadron production in pp collisions.Comment: 6 pages total, 1 Latex file, 3 PS files with figure
Effect of event selection on jetlike correlation measurement in d+Au collisions at sNN=200 GeV
AbstractDihadron correlations are analyzed in sNN=200 GeV d+Au collisions classified by forward charged particle multiplicity and zero-degree neutral energy in the Au-beam direction. It is found that the jetlike correlated yield increases with the event multiplicity. After taking into account this dependence, the non-jet contribution on the away side is minimal, leaving little room for a back-to-back ridge in these collisions
J/ψ polarization in p+p collisions at s=200 GeV in STAR
AbstractWe report on a polarization measurement of inclusive J/ψ mesons in the di-electron decay channel at mid-rapidity at 2<pT<6 GeV/c in p+p collisions at s=200 GeV. Data were taken with the STAR detector at RHIC. The J/ψ polarization measurement should help to distinguish between different models of the J/ψ production mechanism since they predict different pT dependences of the J/ψ polarization. In this analysis, J/ψ polarization is studied in the helicity frame. The polarization parameter λθ measured at RHIC becomes smaller towards high pT, indicating more longitudinal J/ψ polarization as pT increases. The result is compared with predictions of presently available models
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
Longitudinal Double-Spin Asymmetry and Cross Section for Inclusive Jet Production in Polarized Proton Collisions at √s = 200 GeV
We report a measurement of the longitudinal double-spin asymmetry ALL and the differential cross section for inclusive midrapidity jet production in polarized proton collisions at √s=200 GeV. The cross section data cover transverse momenta
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