3,416 research outputs found
Recent STAR results in high-energy polarized proton-proton collisions at RHIC
The STAR experiment at the Relativistic Heavy-Ion Collider at Brookhaven
National Laboratory is carrying out a spin physics program in high-energy
polarized collisions at GeV to gain a
deeper insight into the spin structure and dynamics of the proton.
One of the main objectives of the spin physics program at RHIC is the
extraction of the polarized gluon distribution function based on measurements
of gluon initiated processes, such as hadron and jet production. The STAR
detector is well suited for the reconstruction of various final states
involving jets, , , e and , which allows to
measure several different processes. Recent results will be shown on the
measurement of jet production and hadron production at GeV. The
RHIC spin physics program has recently completed the first data taking period
in 2009 of polarized collisions at GeV. This
opens a new era in the study of the spin-flavor structure of the proton based
on the production of bosons. Recent STAR results on the first
measurement of boson production in polarized collisions
will be shown.Comment: 10 pages, 9 figures, Talk presented at the 26th Winter Workshop on
Nuclear Dynamics, Ocho Rios, Jamaica, January 2-9, 2010 to be published in
Journal of Physics: Conference Series (JPCS) The author may be contacted via:
[email protected]
Recent high pT measurements in STAR
After five years of data taking, the STAR experiment at the Relativistic
Heavy Ion Collider (RHIC) at Brookhaven National Laboratory provides precise
measurements of particle production at high transverse momentum in p-p, d-Au,
and Au-Au collisions at sqrt(s) = 200 GeV. We review recent results on the
flavor dependence of high pT particle suppression and hadron particle spectra
at sqrt(s) = 62.4 GeV. New results on two-particle angular correlations for
identified trigger particles and for low momentum associated charged hadrons in
p-p and Au-Au as well as near-side correlations will be presented
and discussed.Comment: 5th International Conference on Physics and Astrophysics of Quark
Gluon Plasma, Calcutta. 8 pages, 10 figures, submitted to J. Phys. G: Nucl.
Part. Phy
Non Photonic e-D0 correlations in p+p and Au+Au collisions at sqrt(s)NN=200 GeV
The sum of charm and beauty in Au+Au collisions at 200 GeV measured through
nonphotonic electrons, show similar suppression at high pT as light hadrons, in
contrast to expectations based on the dead cone effect. To understand this
observation, it is important to separate the charm and beauty components.
Non-photonic electron-D0 and electron-hadron azimuthal angular correlations are
used to disentangle the contributions from charm and beauty decays. The beauty
contribution in p+p collisions at 200 GeV is found to be comparable to charm at
pT 5.5 GeV, indicating that beauty may contribute significantly to the non
photonic electrons from heavy flavour decays in Au+Au data at high pT.
Furthermore, in Au+Au collisions we present the status of D0 meson
reconstruction using microvertexing techniques made possible with the addition
of the silicon detectors.Comment: 10th Conference on the Intersections of Particle and Nuclear Physics
(CIPANP 2009), San Diego, USA, 26-31 May 200
Event by Event Net Charge Fluctuations
We present analyses of event-by-event dynamical net charge fluctuations
measured in 130 and 200 GeV Au Au collisions with the STAR detector. The
dynamical net charge fluctuations are evaluated using the
observable. Dynamical fluctuations measured in Au Au collisions at 130 and 200
GeV are finite, and exceed charge conservation limits. They deviate from a
perfect 1/N scaling and provide an indication that the collision dynamics
varies with collision centrality.Comment: 6 pages, 3 figures, Proc of 19th Nuclear Dynamics Conf at
Breckenridge, Colorado, Feb 8-15, 200
Flow and non-flow correlations from four-particle multiplets in STAR
Elliptic flow results are presented for Au + Au collisions at
GeV in RHIC. This signal is investigated as a function of transverse
momentum, rapidity and centrality. Results from four-particle correlation
analysis, which can filter out contributions to the flow signal from
correlations unrelated to the event reaction plane (``non-flow''), are
presented and compared to the conventional method, in which non-flow effects
are treated as part of the systematic uncertainty.Comment: 5 pages, 4 figures, uses the class "aipproc
Recent results from the STAR spin program at RHIC
The STAR experiment uses polarized p+p collisions at RHIC to determine the
contributions to the spin of the proton from gluon spin and from orbital
angular momentum of the quarks and gluons. Selective STAR measurements of the
longitudinal double spin asymmetry for inclusive jet and inclusive hadron
production are presented here. In addition, we report measurements of the
transverse spin asymmetry for di-jet production at mid-rapidity and the
transverse single-spin asymmetry for forward pi0 productionComment: 4 pages, 5 figures, presented at GHP06 conferenc
Heavy ion collisions: Correlations and Fluctuations in particle production
Correlations and fluctuations (the latter are directly related to the
2-particle correlations) is one of the important directions in analysis of
heavy ion collisions. At the current stage of RHIC exploration, when the
details matter, basically any physics question is addressed with help of
correlation techniques. In this talk I start with a general introduction to the
correlation and fluctuation formalism and discuss weak and strong sides of
different type of observables. In more detail, I discuss the two-particle
correlations/\mpt fluctuations. In spite of not observing any dramatic
changes in the event-by-event fluctuations with energy, which would indicate a
possible phase transition, such correlations measurements remain an interesting
and important subject, bringing valuable information. Lastly, I show how radial
flow can generate characteristic azimuthal, transverse momentum and rapidity
correlations, which could qualitatively explain many of recently observed
phenomena in nuclear collisions.Comment: 8 pages, 8 figures. Invited talk at 5th International Conference on
Physics and Astrophysics of Quark Gluon Plasma, February 8-12, 2005, Salt
Lake City, Kolkata, Indi
Search for Conical Emission with Three-Particle Correlations
We present preliminary STAR results on 3-particle azimuthal angle correlation
studies in Au+Au collisions at = 200 GeV. The studies are
carried out at mid-rapidity between a trigger particle with 3 4 GeV/c and two associated particles in 1 2 GeV/c. A
cumulant analysis reveals finite 3-particle azimuthal correlations, dominated
by near and away side particle correlations consistent with jet production, and
jet-flow correlations. We use a two-component model to remove underlying
background correlations. This analysis indicates the presence of the conical
emission signals in central Au+Au collisions within the model assumptions about
background composition and normalization.Comment: Proceedings for STAR talk presented at Quark Matter 2006, 4 pages 2
figures, Version 2: typos corrected, references adde
Azimuth Quadrupole Systematics in Au-Au Collisions
We have measured -dependent two-particle number correlations on azimuth
and pseudorapidity for eleven centralities of and 200~GeV
Au-Au collisions at STAR. 2D fits to these angular correlations isolate the
azimuth quadrupole amplitude, denoted , from
localized same-side correlations. Event-plane measurements within
the STAR TPC acceptance can be expressed as a sum of the azimuth quadrupole and
the quadrupole component of the same-side peak. can be
transformed to reveal quadrupole spectra which are approximately
described by a fixed transverse boost and universal L\'evy form nearly
independent of centrality. A parametrization of can be
factored into centrality and -dependent pieces with a simple
dependence above 0.75 GeV/c. Results from STAR are compared to published data
and model predictions.Comment: Conference proceedings for Hot Quarks 201
Open heavy flavor production at RHIC
The study of heavy flavor production in relativistic heavy ion collisions is
an extreme experimental challenge but provides important information on the
properties of the Quark-Gluon Plasma (QGP) created in Au+Au collisions at RHIC.
Heavy-quarks are believed to be produced in the initial stages of the
collision, and are essential on the understanding of parton energy loss in the
dense medium created in such environment. Moreover, heavy-quarks can help to
investigate fundamental properties of QCD in elementary p+p collisions. In this
work we review recent results on heavy flavor production and their interaction
with the hot and dense medium at RHIC.Comment: Quark Matter 2006 proceedings, 8 pages, 5 figure
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