Phys. Rev. C 99, 034908 (2019) We report a new measurement of $D^0$-meson production at mid-rapidity
($|y|$\,$<$\,1) in Au+Au collisions at ${\sqrt{s_{\rm NN}} = \rm{200\,GeV}}$
utilizing the Heavy ...Flavor Tracker, a high resolution silicon detector at the
STAR experiment.
Invariant yields of $D^0$-mesons with transverse momentum $p_{T}$ $\lesssim
9$\,GeV/$c$ are reported in various centrality bins (0--10\%, 10--20\%,
20--40\%, 40--60\% and 60--80\%). Blast-Wave thermal models are used to fit the
$D^0$-meson $p_{T}$ spectra to study $D^0$ hadron kinetic freeze-out
properties. The average radial flow velocity extracted from the fit is
considerably smaller than that of light hadrons ($\pi,K$ and $p$), but
comparable to that of hadrons containing multiple strange quarks
($\phi,\Xi^-$), indicating that $D^0$ mesons kinetically decouple from the
system earlier than light hadrons. The calculated $D^0$ nuclear modification
factors re-affirm that charm quarks suffer large amount of energy loss in the
medium, similar to those of light quarks for $p_{T}$\,$>$\,4\,GeV/$c$ in
central 0--10\% Au+Au collisions. At low $p_{T}$, the nuclear modification
factors show a characteristic structure qualitatively consistent with the
expectation from model predictions that charm quarks gain sizable collective
motion during the medium evolution. The improved measurements are expected to
offer new constraints to model calculations and help gain further insights into
the hot and dense medium created in these collisions.
We summarize and critically evaluate the available data on nuclear fusion cross sections important to energy generation in the Sun and other hydrogen-burning stars and to solar neutrino production. ...Recommended values and uncertainties are provided for key cross sections, and a recommended spectrum is given for 8B solar neutrinos. We also discuss opportunities for further increasing the precision of key rates, including new facilities, new experimental techniques, and improvements in theory. This review, which summarizes the conclusions of a workshop held at the Institute for Nuclear Theory, Seattle, in January 2009, is intended as a 10-year update and supplement to Reviews of Modern Physics 70 (1998) 1265.
The {beta}-delayed {gamma} and proton decay of {sup 23}Al has been studied with an alternative detector setup at the focal plane of the momentum achromat recoil separator MARS at Texas A and M ...University. We could detect protons down to an energy of 200 keV and determine the corresponding branching ratios. Contrary to results of previous {beta}-decay studies, no strong proton intensity from the decay of the isobaric analog state (IAS) of the {sup 23}Al ground state at E{sub x}=7803 keV in {sup 23}Mg was observed. Instead we assign the observed low-energy group E{sub p,c.m.}=206 keV to the decay from a state that is 16 keV below the IAS. We measured both proton and gamma branches from the decay of this state at E{sub x}=7787 keV in {sup 23}Mg, which is a very rare case in the literature. Combining our data with its measured lifetime, we determine its resonance strength to be {omega}{gamma}=1.4{sub -0.4}{sup +0.5} meV. The value is in agreement with older direct measurements, but disagrees with a recent direct measurement. This state is the most important resonance for the radiative proton capture {sup 22}Na(p,{gamma}){sup 23}Mg in some astrophysical environments, such as novae.
Phys. Rev. D 99, 051102 (2019) We report new STAR measurements of the single-spin asymmetries $A_L$ for
$W^+$ and $W^-$ bosons produced in polarized proton--proton collisions at
$\sqrt{s}$ = 510 GeV ...as a function of the decay-positron and decay-electron
pseudorapidity. The data were obtained in 2013 and correspond to an integrated
luminosity of 250 pb$^{-1}$. The results are combined with previous results
obtained with 86 pb$^{-1}$. A comparison with theoretical expectations based on
polarized lepton-nucleon deep-inelastic scattering and prior polarized
proton--proton data suggests a difference between the $\bar{u}$ and $\bar{d}$
quark helicity distributions for $0.05 < x < 0.25$. In addition, we report new
results for the double-spin asymmetries $A_{LL}$ for $W^\pm$, as well as $A_L$
for $Z/\gamma^*$ production and subsequent decay into electron--positron pairs.
We report STAR results on the azimuthal anisotropy parameter v(2) for strange particles K(0)(S), Lambda, and Lambda at midrapidity in Au+Au collisions at sqrts(NN)=130 GeV at the Relativistic Heavy ...Ion Collider. The value of v(2) as a function of transverse momentum, p(t), of the produced particle and collision centrality is presented for both particles up to p(t) approximately 3.0 GeV/c. A strong p(t) dependence in v(2) is observed up to 2.0 GeV/c. The v(2) measurement is compared with hydrodynamic model calculations. The physics implications of the p(t) integrated v(2) magnitude as a function of particle mass are also discussed.
Molecular structures in T = 1 states of 10 B Kuchera, A. N.; Rogachev, G. V.; Goldberg, V. Z. ...
Physical review. C, Nuclear physics,
11/2011, Letnik:
84, Številka:
5
Journal Article
Two-particle correlation measurements projected onto two-dimensional, transverse rapidity coordinates (\(y_{T1},y_{T2}\)), allow access to dynamical properties of the QCD medium produced in ...relativistic heavy-ion collisions that angular correlation measurements are not sensitive to. We report non-identified charged-particle correlations for Au + Au minimum-bias collisions at \(\sqrt{s_{\rm NN}}\) = 200 GeV taken by the STAR experiment at the Relativistic Heavy-Ion Collider (RHIC). Correlations are presented as 2D functions of transverse rapidity for like-sign, unlike-sign and all charged-particle pairs, as well as for particle pairs whose relative azimuthal angles lie on the near-side, the away-side, or at all relative azimuth. The correlations are constructed using charged particles with transverse momentum \(p_T \geq 0.15\) GeV/\(c\), pseudorapidity from \(-\)1 to 1, and azimuthal angles from \(-\pi\) to \(\pi\). The significant correlation structures that are observed evolve smoothly with collision centrality. The major correlation features include a saddle shape plus a broad peak with maximum near \(y_T \approx 3\), corresponding to \(p_T \approx\) 1.5 GeV/\(c\). The broad peak is observed in both like- and unlike-sign charge combinations and in near- and away-side relative azimuthal angles. The all-charge, all-azimuth correlation measurements are compared with the theoretical predictions of {\sc hijing} and {\sc epos}. The results indicate that the correlations for peripheral to mid-central collisions can be approximately described as a superposition of nucleon + nucleon collisions with minimal effects from the QCD medium. Strong medium effects are indicated in mid- to most-central collisions.
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