362 research outputs found
Direct Photon Measurements at PHENIX
PHENIX has measured direct photons in p+p and Au+Au collisions at
sqrt{s_{NN}}=200 GeV. The p+p measurement is in good agreement with pQCD
expectations. The nuclear modification factor in Au+Au is found to be
consistent with unity for all centralities, and is compared to theoretical
models. The data are found in agreement with models that take into account
initial state modifications, as well as with those that account also for final
state modifications.Comment: 2 pages, 2 figures, to appear in the proceedings of Hard Probes 201
Anomalous \phi Meson Suppression in Au+Au Collisions at \sqrt{s_{NN}}=200 GeV Measured by the PHENIX Experiment at RHIC
The PHENIX experiment at RHIC has measured the \phi-meson production at
mid-rapidity in p+p, d+Au, Cu+Cu and Au+Au collisions at \sqrt{s_{NN}}=200 GeV
via the K^+K^- decay mode. The transverse momentum spectra of the \phi-meson
and the nuclear modification factor as a function of centrality are reviewed
here.Comment: 4 pages, 4 figures; To appear in the conference proceedings for Quark
Matter 2009, March 30 - April 4, Knoxville, Tennesse
Diagnosing Energy Loss: PHENIX Results on High-pT Hadron Spectra
Measurements of inclusive spectra of hadrons at large transverse momentum
over a broad range of energy in different collision systems have been performed
with the PHENIX experiment at RHIC. The data allow to study the energy and
system size dependence of the suppression observed in RAA of high-pT hadrons at
sqrt(s_NN)= 200 GeV. Due to the large energy range from sqrt(s_NN)= 22 GeV to
200 GeV, the results can be compared to results from CERN SPS at a similar
energy. The large Au+Au dataset from the 2004 run of RHIC also allows to
constrain theoretical models that describe the hot and dense matter produced in
such collisions. Investigation of particle ratios such as eta/pi0 helps
understanding the mechanisms of energy loss.Comment: 4 pages, 6 figures. To appear in the proceedings of the 19th
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(Quark Matter 2006), Shanghai, China, November 14-20, 200
Measurements of Hard-Scattering by PHENIX at RHIC
Hard-scattering in p-p collisions was discovered in 1972 at the CERN-ISR, the
first hadron collider. Techniques were developed and several hard-processes
were discovered which form the basis for many of the measurements made in p-p
and Au+Au collisions at RHIC. Recent measurements of hard-scattering and
related reactions by the PHENIX experiment at RHIC are presented in this
context.Comment: 6 pages, 12 figures, Proceedings of Hadron Collider Physics Symposium
2007, La Biodola, Isola d'Elba (Italy), May 20-26, 200
Measurements of double-helicity asymmetries in inclusive production in longitudinally polarized collisions at GeV
We report the double helicity asymmetry, , in inclusive
production at forward rapidity as a function of transverse momentum
and rapidity . The data analyzed were taken during
GeV longitudinally polarized collisions at the Relativistic Heavy Ion
Collider (RHIC) in the 2013 run using the PHENIX detector. At this collision
energy, particles are predominantly produced through gluon-gluon
scatterings, thus is sensitive to the gluon polarization
inside the proton. We measured by detecting the decay
daughter muon pairs within the PHENIX muon spectrometers in the
rapidity range . In this kinematic range, we measured the
to be ~(stat)~~(syst). The
can be expressed to be proportional to the product of the
gluon polarization distributions at two distinct ranges of Bjorken : one at
moderate range where recent RHIC data of jet and
double helicity spin asymmetries have shown evidence for significant gluon
polarization, and the other one covering the poorly known small- region . Thus our new results could be used to further
constrain the gluon polarization for .Comment: 335 authors, 10 pages, 4 figures, 3 tables, 2013 data. Version
accepted for publication by Phys. Rev. D. Plain text data tables for the
points plotted in figures for this and previous PHENIX publications are (or
will be) publicly available at http://www.phenix.bnl.gov/papers.htm
Inclusive cross section and double helicity asymmetry for \pi^0 production in p+p collisions at sqrt(s)=200 GeV: Implications for the polarized gluon distribution in the proton
The PHENIX experiment presents results from the RHIC 2005 run with polarized
proton collisions at sqrt(s)=200 GeV, for inclusive \pi^0 production at
mid-rapidity. Unpolarized cross section results are given for transverse
momenta p_T=0.5 to 20 GeV/c, extending the range of published data to both
lower and higher p_T. The cross section is described well for p_T < 1 GeV/c by
an exponential in p_T, and, for p_T > 2 GeV/c, by perturbative QCD. Double
helicity asymmetries A_LL are presented based on a factor of five improvement
in uncertainties as compared to previously published results, due to both an
improved beam polarization of 50%, and to higher integrated luminosity. These
measurements are sensitive to the gluon polarization in the proton, and exclude
maximal values for the gluon polarization.Comment: 375 authors, 7 pages, 3 figures. Submitted to Phys. Rev. D, Rapid
Communications. Plain text data tables for the points plotted in figures for
this and previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
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