33 research outputs found
Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions
The HERA-B collaboration has studied the production of charmonium and open
charm states in collisions of 920 GeV protons with wire targets of different
materials. The acceptance of the HERA-B spectrometer covers negative values of
xF up to xF=-0.3 and a broad range in transverse momentum from 0.0 to 4.8
GeV/c. The studies presented in this paper include J/psi differential
distributions and the suppression of J/psi production in nuclear media.
Furthermore, production cross sections and cross section ratios for open charm
mesons are discussed.Comment: 5 pages, 9 figures, to be published in the proceedings of the 6th
International Conference on Hyperons, Charm & Beauty Hadrons (BEACH04),
Chicago, IL, June 27 - July 3, 200
Search for the Flavor-Changing Neutral Current Decay with the HERA-B Detector
We report on a search for the flavor-changing neutral current decay using events recorded with a dimuon trigger in
interactions of 920 GeV protons with nuclei by the HERA-B experiment. We find
no evidence for such decays and set a 90% confidence level upper limit on the
branching fraction .Comment: 17 pages, 4 figures (of which 1 double), paper to be submitted to
Physics Letters
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
DIRAC Experiment and Test of Low-Energy QCD
The low-energy QCD predictions to be tested by the DIRAC experiment are revised. The experimental method, the setup characteristics and capabilities, along with first experimental results are reported. Preliminary analysis shows good detector performance: alignment error via mass measurement with , relative momentum resolution , and evidence for $\pi^
Limits for the central production of Î+ and Îââ pentaquarks in 920-GeV pA collisions
We have searched for Î+(1540) and Îââ(1862) pentaquark candidates in proton-inducedreactions on C, Ti, and W targets at midrapidity and sâ=41.6ââGeV. In 2Ă108 inelastic eventswe find no evidence for narrow (Ïâ5ââMeV) signals in the Î+âpK0S and ÎâââÎâÏâ channels; our 95% C.L. upper limits (UL) forthe inclusive production cross section times branching fraction BâdÏ/dy $y â0 are (4-16) ÎŒb/N for a Î+ mass between 1521 and 1555 MeV,and 2.5ÎŒb/N for the Îââ. The UL of the yield ratio of Î+/Î(1520)<(3-12)% is significantly lower than model predictions.Our UL of BâÎââ/Î(1530)0<4% is at variance with the results that have provided the first evidencefor the Îââ
The time-of-flight detector of the DIRAC experiment
The construction and performance of a large area time-of-flight detector for the DIRAC experiment at CERN is reported. With an average time resolution of 123 ps per counter at rates up to 1 MHz, it allows excellent separation of ppi**- from pi**+pi**- pairs up to 4.6 GeV/c momentum, as well as of Coulomb-correlated pion pairs from accidentals. The optimization of scintillator material, photomultiplier performance and readout electronics is described
Test of chiral perturbation theory with DIRAC at CERN
The DIRAC experiment at CERN aims to form pi /sup +/ pi /sup -/ atomic states and to measure their lifetime with 10% accuracy. This will give a precision of 5% in the determination of pi pi S-wave scattering lengths, of the same level of Chiral Perturbation Theory calculations. In this way a crucial test on the theory validity would be performed. (13 refs)