We report precision measurements of the Feynman x (xF) dependence, and first measurements of the transverse momentum (pT) dependence, of transverse single-spin asymmetries for the production of pi0 ...mesons from polarized proton collisions at sqrts = 200 GeV. The xF dependence of the results is in fair agreement with perturbative QCD model calculations that identify orbital motion of quarks and gluons within the proton as the origin of the spin effects. Results for the pT dependence at fixed xF are not consistent with these same perturbative QCD-based calculations.
The momentum dispersion of the proton beam extracted from the vacuum chamber of the U-70 accelerator by channeling was measured for the first time. At an 80-mrad bending angle of the Si single ...crystal, the following beam parameters were attained: an intensity of 10
7
protons/s for 10
12
protons/s hitting the crystal, momentum dispersion of the beam Δ
p
/
p
= 0.13%, and a background particle admixture of 0.03% or less.
The single-spin asymmetry
A
N
in the reaction
π
−
+
d
↑
→
π
0
+
X
in the beam-fragmentation region at the energy of 40 GeV was investigated by using the PROZA setup installed at the U-70 accelerator ...of the Institute for High Energy Physics (IHEP, Protvino). It was measured to be
A
N
= (13.6 ± 2.6(stat.) ± 2.0(syst.))% in the intervals 0.7 <
x
F
< 1.0 and 1.0 <
p
T
< 1.8 GeV/
c
. The results agree with the asymmetry of
π
0
mesons in the charge-exchange reaction
π
−
+
p
↑
→
π
0
+
n
at the same values of the transverse momentum and beam energy. The asymmetry in the reaction
K
−
+
d
↑
→
π
0
+
X
was simultaneously measured and found to be
A
N
= (11 ± 14)% for
p
T
> 1.2 GeV/
c
.
Studies of the radiation hardness of lead tungstate crystals produced by the Bogoroditsk Techno-Chemical Plant in Russia and the Shanghai Institute of Ceramics in China have been carried out at IHEP, ...Protvino. The crystals were irradiated by a 40GeV pion beam. After full recovery, the same crystals were irradiated using a 137Csγ-ray source. The dose rate profiles along the crystal length were observed to be quite similar. We compare the effects of the two types of radiation on the crystal's light output.
We report the first measurement of the opening angle distribution between pairs of jets produced in high-energy collisions of transversely polarized protons. The measurement probes (Sivers) ...correlations between the transverse spin orientation of a proton and the transverse momentum directions of its partons. With both beams polarized, the wide pseudorapidity (-1< or = eta < or = +2) coverage for jets permits separation of Sivers functions for the valence and sea regions. The resulting asymmetries are all consistent with zero and considerably smaller than Sivers effects observed in semi-inclusive deep inelastic scattering. We discuss theoretical attempts to reconcile the new results with the sizable transverse spin effects seen in semi-inclusive deep inelastic scattering and forward hadron production in pp collisions.
We present first measurements of the phi-meson elliptic flow (v2(pT)) and high-statistics pT distributions for different centralities from radical sNN=200 GeV Au+Au collisions at RHIC. In minimum ...bias collisions the v2 of the phi meson is consistent with the trend observed for mesons. The ratio of the yields of the Omega to those of the phi as a function of transverse momentum is consistent with a model based on the recombination of thermal s quarks up to pT approximately 4 GeV/c, but disagrees at higher momenta. The nuclear modification factor (R CP) of phi follows the trend observed in the K S 0 mesons rather than in Lambda baryons, supporting baryon-meson scaling. These data are consistent with phi mesons in central Au+Au collisions being created via coalescence of thermalized s quarks and the formation of a hot and dense matter with partonic collectivity at RHIC.
We report on the performance of a monitoring system for a prototype calorimeter for the BTeV experiment that uses lead tungstate crystals coupled with photomultiplier tubes. The tests were carried ...out at the 70-GeV accelerator complex at Protvino, Russia.
Spin Physics Program At IHEP-Protvino Mochalov, V V; Vasiliev, A N; Bazhanov, N A ...
AIP conference proceedings,
10/2008, Volume:
1149
Journal Article
Peer reviewed
A new single-spin asymmetry A(N) measurement has been carried out at IHEP at SO GeV. A(N) was found to be -(6.2plus/minus 1.5)% in the polarized target fragmentation region at -0.6 < x(f) < -0.25. ...The result proves that asymmetry does not depend on beam energy. A review of polarization results from Protvino as well as a proposal of the new experiment SPASCHARM are also presented.
The STAR collaboration at the BNL Relativistic Heavy-Ion Collider (RHIC) reports measurements of the inclusive yield of nonphotonic electrons, which arise dominantly from semileptonic decays of heavy ...flavor mesons, over a broad range of transverse momenta (1.2<p(T)<10 GeV/c) in p+p, d+Au, and Au+Au collisions at sqrts_{NN}=200 GeV. The nonphotonic electron yield exhibits an unexpectedly large suppression in central Au+Au collisions at high p(T), suggesting substantial heavy-quark energy loss at RHIC. The centrality and p(T) dependences of the suppression provide constraints on theoretical models of suppression.
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