121 research outputs found
Strangelet search at RHIC
Two position sensitive Shower Maximum Detector (SMDs) for Zero-Degree
Calorimeters (ZDCs) were installed by STAR before run 2004 at both upstream and
downstream from the interaction point along the beam axis where particles with
small rigidity are swept away by strong magnetic field. The ZDC-SMDs provides
information about neutral energy deposition as a function of transverse
position in ZDCs. We report the preliminary results of strangelet search from a
triggered data-set sampling 100 million Au+Au collisions at top RHIC energy.Comment: Strange Quark Matter 2004 conference proceedin
Correlations in STAR: interferometry and event structure
STAR observes a complex picture of RHIC collisions where correlation effects
of different origins -- initial state geometry, semi-hard scattering,
hadronization, as well as final state interactions such as quantum intensity
interference -- coexist. Presenting the measurements of flow, mini-jet
deformation, modified hadronization, and the Hanbury Brown and Twiss effect, we
trace the history of the system from the initial to the final state. The
resulting picture is discussed in the context of identifying the relevant
degrees of freedom and the likely equilibration mechanism.Comment: 8 pages, 6 figures, plenary talk at the 5th International Conference
on Physics and Astrophysics of Quark Gluon Plasma, to appear in Journal of
Physics G (http://www.iop.org
Multiplicity and Pseudorapidity Distributions of Charged Particles and Photons at Forward Pseudorapidity in Au + Au Collisions at sqrt{s_NN} = 62.4 GeV
We present the centrality dependent measurement of multiplicity and
pseudorapidity distributions of charged particles and photons in Au + Au
collisions at sqrt{s_NN} = 62.4 GeV. The charged particles and photons are
measured in the pseudorapidity region 2.9 < eta < 3.9 and 2.3 < eta < 3.7,
respectively. We have studied the scaling of particle production with the
number of participating nucleons and the number of binary collisions. The
photon and charged particle production in the measured pseudorapidity range has
been shown to be consistent with energy independent limiting fragmentation
behavior. The photons are observed to follow a centrality independent limiting
fragmentation behavior while for the charged particles it is centrality
dependent. We have carried out a comparative study of the pseudorapidity
distributions of positively charged hadrons, negatively charged hadrons,
photons, pions, net protons in nucleus--nucleus collisions and pseudorapidity
distributions from p+p collisions. From these comparisons we conclude that
baryons in the inclusive charged particle distribution are responsible for the
observed centrality dependence of limiting fragmentation. The mesons are found
to follow an energy independent behavior of limiting fragmentation while the
behavior of baryons seems to be energy dependent.Comment: 17 pages and 20 figure
Longitudinal double-spin asymmetry and cross section for inclusive jet production in polarized proton collisions at sqrt(s) = 200 GeV
We report a measurement of the longitudinal double-spin asymmetry A_LL and
the differential cross section for inclusive midrapidity jet production in
polarized proton collisions at sqrt(s)=200 GeV. The cross section data cover
transverse momenta 5 < pT < 50 GeV/c and agree with next-to-leading order
perturbative QCD evaluations. The A_LL data cover 5 < pT < 17 GeV/c and
disfavor at 98% C.L. maximal positive gluon polarization in the polarized
nucleon.Comment: 6 pages, 3 figures. Minor changes from review process in Phys. Rev.
Lett. Plain text tables of data in STAR publications may be found at
http://www.star.bnl.gov/central/publications
Identified baryon and meson distributions at large transverse momenta from Au+Au collisions at GeV
Transverse momentum spectra of , and up to 12 GeV/c
at mid-rapidity in centrality selected Au+Au collisions at GeV are presented. In central Au+Au collisions, both and
show significant suppression with respect to binary scaling at
4 GeV/c. Protons and anti-protons are less suppressed than
, in the range 1.5 6 GeV/c. The and
ratios show at most a weak dependence and no significant
centrality dependence. The ratios in central Au+Au collisions approach
the values in p+p and d+Au collisions at 5 GeV/c. The results at high
indicate that the partonic sources of , and have
similar energy loss when traversing the nuclear medium.Comment: 6 pages, 4 figure
Neutral Kaon Interferometry in Au+Au collisions at sqrt(s_NN) = 200 GeV
We present the first statistically meaningful results from two-K0s
interferometry in heavy-ion collisions. A model that takes the effect of the
strong interaction into account has been used to fit the measured correlation
function. The effects of single and coupled channel were explored. At the mean
transverse mass m_T = 1.07 GeV, we obtain the values R = 4.09 +/- 0.46 (stat.)
+/- 0.31 (sys) fm and lambda = 0.92 +/- 0.23 (stat) +/- 0.13 (sys), where R and
lambda are the invariant radius and chaoticity parameters respectively. The
results are qualitatively consistent with m_T systematics established with
pions in a scenario characterized by a strong collective flow.Comment: 11 pages, 10 figure
Azimuthal anisotropy and correlations at large transverse momenta in p+p and Au+Au collisions at sqrt[sNN] = 200 GeV
Results on high transverse momentum charged particle emission with respect to the reaction plane are presented for Au+Au collisions at sqrt[sNN]=200 GeV. Two- and four-particle correlations results are presented as well as a comparison of azimuthal correlations in Au+Au collisions to those in p+p at the same energy. The elliptic anisotropy v2 is found to reach its maximum at pt~3 GeV/c, then decrease slowly and remain significant up to pt ~ 7-10 GeV/c. Stronger suppression is found in the back-to-back high-pt particle correlations for particles emitted out of plane compared to those emitted in plane. The centrality dependence of v2 at intermediate pt is compared to simple models based on jet quenching
Longitudinal double-spin asymmetry for inclusive jet production in p+p collisions at sqrt(s)=200 GeV
We report a new STAR measurement of the longitudinal double-spin asymmetry
A_LL for inclusive jet production at mid-rapidity in polarized p+p collisions
at a center-of-mass energy of sqrt(s) = 200 GeV. The data, which cover jet
transverse momenta 5 < p_T < 30 GeV/c, are substantially more precise than
previous measurements. They provide significant new constraints on the gluon
spin contribution to the nucleon spin through the comparison to predictions
derived from one global fit of polarized deep-inelastic scattering
measurements.Comment: 7 pages, 4 figures + 1 tabl
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