55 research outputs found
System size and energy dependence of near-side di-hadron correlations
Two-particle azimuthal () and pseudorapidity ()
correlations using a trigger particle with large transverse momentum () in
+Au, Cu+Cu and Au+Au collisions at =\xspace 62.4 GeV and
200~GeV from the STAR experiment at RHIC are presented. The \ns correlation is
separated into a jet-like component, narrow in both and
, and the ridge, narrow in but broad in .
Both components are studied as a function of collision centrality, and the
jet-like correlation is studied as a function of the trigger and associated
. The behavior of the jet-like component is remarkably consistent for
different collision systems, suggesting it is produced by fragmentation. The
width of the jet-like correlation is found to increase with the system size.
The ridge, previously observed in Au+Au collisions at = 200
GeV, is also found in Cu+Cu collisions and in collisions at
=\xspace 62.4 GeV, but is found to be substantially smaller at
=\xspace 62.4 GeV than at = 200 GeV for the
same average number of participants ().
Measurements of the ridge are compared to models.Comment: 17 pages, 14 figures, submitted to Phys. Rev.
Measurements of and Production in + Collisions at = 200 GeV
We report measurements of charmed-hadron (, ) production cross
sections at mid-rapidity in + collisions at a center-of-mass energy of
200 GeV by the STAR experiment. Charmed hadrons were reconstructed via the
hadronic decays , and their charge conjugates,
covering the range of 0.62.0 GeV/ and 2.06.0 GeV/ for
and , respectively. From this analysis, the charm-pair production cross
section at mid-rapidity is = 170 45
(stat.) (sys.) b. The extracted charm-pair cross section is
compared to perturbative QCD calculations. The transverse momentum differential
cross section is found to be consistent with the upper bound of a Fixed-Order
Next-to-Leading Logarithm calculation.Comment: 15 pages, 16 figures. Revised version submitted to Phys. Rev.
Inclusive charged hadron elliptic flow in Au + Au collisions at = 7.7 - 39 GeV
A systematic study is presented for centrality, transverse momentum ()
and pseudorapidity () dependence of the inclusive charged hadron elliptic
flow () at midrapidity() in Au+Au collisions at
= 7.7, 11.5, 19.6, 27 and 39 GeV. The results obtained with
different methods, including correlations with the event plane reconstructed in
a region separated by a large pseudorapidity gap and 4-particle cumulants
(), are presented in order to investigate non-flow correlations and
fluctuations. We observe that the difference between and
is smaller at the lower collision energies. Values of , scaled by
the initial coordinate space eccentricity, , as a function
of are larger in more central collisions, suggesting stronger collective
flow develops in more central collisions, similar to the results at higher
collision energies. These results are compared to measurements at higher
energies at the Relativistic Heavy Ion Collider ( = 62.4 and 200
GeV) and at the Large Hadron Collider (Pb + Pb collisions at =
2.76 TeV). The values for fixed rise with increasing collision
energy within the range studied (). A comparison to
viscous hydrodynamic simulations is made to potentially help understand the
energy dependence of . We also compare the results to UrQMD
and AMPT transport model calculations, and physics implications on the
dominance of partonic versus hadronic phases in the system created at Beam
Energy Scan (BES) energies are discussed.Comment: 20 pages, 12 figures. Version accepted by PR
Identified hadron compositions in p+p and Au+Au collisions at high transverse momenta at GeV
We report transverse momentum ( GeV/) spectra of , , , ,
, and at mid-rapidity in p+p and Au+Au collisions at
= 200 GeV. Perturbative QCD calculations are consistent with
spectra in p+p collisions but do not reproduce and
spectra. The observed decreasing antiparticle-to-particle ratios with
increasing provide experimental evidence for varying quark and gluon jet
contributions to high- hadron yields. The relative hadron abundances in
Au+Au at GeV/ are measured to be similar to the p+p
results, despite the expected Casimir effect for parton energy loss.Comment: 6 pages, 3 figures, published at PR
Longitudinal and transverse spin asymmetries for inclusive jet production at mid-rapidity in polarized p+p collisions at √s=200 GeV
We report STAR measurements of the longitudinal double-spin asymmetry ALL, the transverse single-spin asymmetry AN, and the transverse double-spin asymmetries AΣ and ATT for inclusive jet production at mid-rapidity in polarized p+p collisions at a center- of-mass energy of √s=200 GeV. The data represent integrated luminosities of 7.6 pb-1 with longitudinal polarization and 1.8 pb- 1 with transverse polarization, with 50%–55% beam polarization, and were recorded in 2005 and 2006. No evidence is found for the existence of statistically significant jet AN, AΣ, or ATT at mid- rapidity. Recent model calculations indicate the AN results may provide new limits on the gluon Sivers distribution in the proton. The asymmetry ALL significantly improves the knowledge of gluon polarization in the nucleon
Longitudinal and transverse spin asymmetries for inclusive jet production at mid-rapidity in polarized p
Transcriptome response of high- and low-light-adapted Prochlorococcus strains to changing iron availability
Prochlorococcus contributes significantly to ocean primary productivity. The link
between primary productivity and iron in specific ocean regions is well established
and iron-limitation of Prochlorococcus cell division rates in these regions has been
demonstrated. However, the extent of ecotypic variation in iron metabolism among
Prochlorococcus and the molecular basis for differences is not understood. Here, we
examine the growth and transcriptional response of Prochlorococcus strains, MED4
and MIT9313, to changing iron concentrations. During steady-state, MIT9313
sustains growth at an order-of-magnitude lower iron concentration than MED4. To
explore this difference, we measured the whole-genome transcriptional response of
each strain to abrupt iron starvation and rescue. Only four of the 1159 orthologs of
MED4 and MIT9313 were differentially-expressed in response to iron in both strains.
However, in each strain, the expression of over a hundred additional genes changed,
many of which are in labile genomic regions, suggesting a role for lateral gene
transfer in establishing diversity of iron metabolism among Prochlorococcus.
Furthermore, we found that MED4 lacks three genes near the iron-deficiency induced
gene (idiA) that are present and induced by iron stress in MIT9313. These genes are
interesting targets for studying the adaptation of natural Prochlorococcus assemblages
to local iron conditions as they show more diversity than other genomic regions in
environmental metagenomic databases.Gordon and Betty Moore FoundationNational Science Foundation (U.S.) (Biological Oceanography)United States. Office of Naval Research (ONR Young Investigator Award)National Science Foundation (U.S.) (Chemical Oceanography)National Science Foundation (U.S.) (Environmental Genomics grants
Vascular Abnormalities of the Breast: Arterial and Venous Disorders, Vascular Masses, and Mimic Lesions with Radiologic-Pathologic Correlation
A double-blind randomized placebo-controlled study of the efficacy and safety of pirlindole, a reversible monoamine oxidase A inhibitor, in the treatment of depression
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