12 research outputs found
Measurement of the J/Psi Production Cross Section in 920 GeV/c Fixed-Target Proton-Nucleus Interactions
The mid-rapidity (dsigma_(pN)/dy at y=0) and total sigma_(pN) production
cross sections of J/Psi mesons are measured in proton-nucleus interactions.
Data collected by the HERA-B experiment in interactions of 920 GeV/c protons
with carbon, titanium and tungsten targets are used for this analysis. The
J/Psi mesons are reconstructed by their decay into lepton pairs. The total
production cross section obtained is sigma_(pN)(J/Psi) = 663 +- 74 +- 46
nb/nucleon. In addition, our result is compared with previous measurements
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Spectroscopy and New Particles in BaBar
Results on charmonium states and searches for pentaquark states at the BABAR experiment are presented
Kinematic distributions and nuclear effects of J/psi production in 920-GeV fixed-target proton-nucleus collisions
Measurements of the kinematic distributions of mesons produced in C, Ti and W collisions at in the Feynman- region and for transverse momentum up to are presented. The and dependencies of the nuclear suppression parameter, , are also given. The results are based on mesons in both the and decay channels. The data have been collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The measurement explores the negative region of for the first time. The average value of in the measured region is . The data suggest that the strong nuclear suppression of production previously observed at high turns into an enhancement at negative
Polarization of and in 920-GeV Fixed-Target Proton-Nucleus Collisions
A measurement of the polarization of Lambda and Anti-Lambda baryons produced
in pC and pW collisions at sqrt(s)=41.6 GeV has been performed with the HERA-B
spectrometer. The measurements cover the kinematic range of 0.6 GeV/c < p_T<1.2
GeV/c in transverse momentum and -0.15<x_F<0.01 in Feynman-x. The polarization
results from the two different targets agree within the statistical error. In
the combined data set, the largest deviation from zero, +0.054 +- 0.029, is
measured for x_F < -0.07. Zero polarization is expected at x_F=0 in the absence
of nuclear effects. The polarization results for the Lambda agree with a
parametrization of previous measurements which were performed at positive x_F
values, where the Lambda polarization is negative. Results of Anti-Lambda
polarization measurements are consistent with zero.Comment: 11 pages, 3 figure