21 research outputs found
Observation of Transverse Spin-Dependent Azimuthal Correlations of Charged Pion Pairs in at GeV
We report the observation of transverse polarization-dependent azimuthal
correlations in charged pion pair production with the STAR experiment in
collisions at RHIC. These correlations directly probe quark
transversity distributions. We measure signals in excess of five standard
deviations at high transverse momenta, at high pseudorapidities eta>0.5, and
for pair masses around the mass of the rho-meson. This is the first direct
transversity measurement in p+p collisions. Comparing the results to data from
lepton-nucleon scattering will test the universality of these spin-dependent
quantities.Comment: 11 pages, 5 figures, 15 tables. Submitted to PR
Energy dependence of acceptance-corrected dielectron excess mass spectrum at mid-rapidity in Au+Au collisions at and 200 GeV
The acceptance-corrected dielectron excess mass spectra, where the known
hadronic sources have been subtracted from the inclusive dielectron mass
spectra, are reported for the first time at mid-rapidity in
minimum-bias Au+Au collisions at = 19.6 and 200 GeV. The excess
mass spectra are consistently described by a model calculation with a broadened
spectral function for GeV/. The integrated
dielectron excess yield at = 19.6 GeV for
GeV/, normalized to the charged particle multiplicity at mid-rapidity, has
a value similar to that in In+In collisions at = 17.3 GeV. For
= 200 GeV, the normalized excess yield in central collisions is
higher than that at = 17.3 GeV and increases from peripheral to
central collisions. These measurements indicate that the lifetime of the hot,
dense medium created in central Au+Au collisions at = 200 GeV
is longer than those in peripheral collisions and at lower energies.Comment: 9 pages, 6 figure
Long-range pseudorapidity dihadron correlations in +Au collisions at GeV
Dihadron angular correlations in +Au collisions at
GeV are reported as a function of the measured zero-degree calorimeter neutral
energy and the forward charged hadron multiplicity in the Au-beam direction. A
finite correlated yield is observed at large relative pseudorapidity
() on the near side (i.e. relative azimuth ). This
correlated yield as a function of appears to scale with the
dominant, primarily jet-related, away-side () yield. The
Fourier coefficients of the correlation, , have a strong dependence. In addition, it is
found that is approximately inversely proportional to the mid-rapidity
event multiplicity, while is independent of it with similar magnitude
in the forward (-going) and backward (Au-going) directions.Comment: 8 pages, 4 figure
Effect of event selection on jetlike correlation measurement in +Au collisions at GeV
Dihadron correlations are analyzed in GeV +Au
collisions classified by forward charged particle multiplicity and zero-degree
neutral energy in the Au-beam direction. It is found that the jetlike
correlated yield increases with the event multiplicity. After taking into
account this dependence, the non-jet contribution on the away side is minimal,
leaving little room for a back-to-back ridge in these collisions.Comment: 7 pages, 3 figure
Energy dependence of acceptance-corrected dielectron excess mass spectrum at mid-rapidity in Au + Au collisions at s NN = 19.6 and 200 GeV
The acceptance-corrected dielectron excess mass spectra, where the known hadronic sources have been subtracted from the inclusive dielectron mass spectra, are reported for the first time at mid-rapidity |yee|<1 in minimum-bias Au+Au collisions at âsNN=19.6 and 200 GeV. The excess mass spectra are consistently described by a model calculation with a broadened Ï spectral function for Mee<1.1 GeV/c2. The integrated dielectron excess yield at âsNN=19.6 GeV for 0.
Effect of event selection on jetlike correlation measurement in d+Au collisions at sNN=200Â GeV
AbstractDihadron correlations are analyzed in sNN=200Â GeV d+Au collisions classified by forward charged particle multiplicity and zero-degree neutral energy in the Au-beam direction. It is found that the jetlike correlated yield increases with the event multiplicity. After taking into account this dependence, the non-jet contribution on the away side is minimal, leaving little room for a back-to-back ridge in these collisions
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Effect of event selection on jetlike correlation measurement in d + Au collisions at âsNN = 200 GeV
Dihadron correlations are analyzed in âsNN = 200 GeV d + Au collisions classified by forward charged particle multiplicity and zero-degree neutral energy in the Au-beam direction. It is found that the jetlike correlated yield increases with the event multiplicity. After taking into account this dependence, the non-jet contribution on the away side is minimal, leaving little room for a back-to-back ridge in these collisions
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Energy dependence of acceptance-corrected dielectron excess mass spectrum at mid-rapidity in Au+Au collisions at âsNN=19.6 and 200 GeV
The acceptance-corrected dielectron excess mass spectra, where the known hadronic sources have been subtracted from the inclusive dielectron mass spectra, are reported for the first time at mid-rapidity |yee|<1 in minimum-bias Au+Au collisions at âsNN=19.6 and 200 GeV. The excess mass spectra are consistently described by a model calculation with a broadened Ï spectral function for Mee<1.1 GeV/c2. The integrated dielectron excess yield at âsNN=19.6 GeV for 0.
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Long-range pseudorapidity dihadron correlations in d + Au collisions at âsNN = 200 GeV
Dihadron angular correlations in d + Au collisions at âsNN = 200 GeV are reported as a function of the measured zero-degree calorimeter neutral energy and the forward charged hadron multiplicity in the Au-beam direction. A finite correlated yield is observed at large relative pseudorapidity (Ύη) on the near side (i.e. relative azimuth ÎŽÏ~0). This correlated yield as a function of Ύη appears to scale with the dominant, primarily jet-related, away-side (ÎŽÏ~Ï) yield. The Fourier coefficients of the ÎŽÏ correlation, Vn=ăcos n ÎŽ Ïă, have a strong Ύη dependence. In addition, it is found that V1 is approximately inversely proportional to the mid-rapidity event multiplicity, while V2 is independent of it with similar magnitude in the forward (d-going) and backward (Au-going) directions