33 research outputs found
Production of the Charmonium States and in Proton Nucleus Interactions at GeV.
No full textA measurement of the ratio R χ c = ( χ c → J / ψ + γ ) / J / ψ in p C , p Ti , and p W interactions at 920 GeV / c ( √ s = 41.6 GeV ) in the Feynman-x range − 0.35 < x J / ψ F < 0.15 is presented. Both μ + μ − and e + e − J / ψ decay channels are observed with an overall statistics of about 15 000 χ c events, which is by far the largest available sample in pA collisions. The result is R χ c = 0.188 ± 0.013 st + 0.024 − 0.022 sys averaged over the different materials, when no J / ψ and χ c polarizations are considered. The χ c 1 to χ c 2 production ratio R 12 = R χ c 1 / R χ c 2 is measured to be 1.02 ± 0.40 , leading to a cross section ratio σ ( χ c 1 ) σ ( χ c 2 ) = 0.57 ± 0.23 . The dependence of R χ c on the Feynman-x of the J / ψ , x J / ψ F , and its transverse momentum, p J / ψ T , is studied, as well as its dependence on the atomic number, A, of the target. For the first time, an extensive study of possible biases on R χ c and R 12 due to the dependence of acceptance on the polarization states of J / ψ and χ c is performed. By varying the polarization parameter, λ obs , of all produced J / ψ 's by two sigma around the value measured by HERA-B, and considering the maximum variation due to the possible χ c 1 and χ c 2 polarizations, it is shown that R χ c could change by a factor between 1.02 and 1.21 and R 12 by a factor between 0.89 and 1.16
The First-Level Trigger of the HERA-B experiment: performance and expectations
No full textHERA-B is a fixed target spectrometer which uses 920 GeV protons incident on various target materials. The experiment is aimed to study various aspects of beauty and charm physics. The detector is designed to operate at high interaction rates with an average of 4-5 interactions per event. The First-Level Trigger (FLT) is required to reduce the input rate by more than two orders of magnitude while keeping high efficiency for beauty and charm channels. The trigger performs online track reconstruction and takes decisions based on particle momenta or pair masses. A pipeline architecture is implemented on about 100 pipelined hardware processors to perform this job. The working principle and first results of the FLT performance based on the data acquired during the run in the year 2000 are described. (C) 2002 Elsevier Science B.V. All rights reserved
production via chi() decays in 920-GeV pA interactions
No full textUsing data collected by the HERA- B experiment, we have measured the fraction of J / ψ 's produced via radiative χ c decays in interactions of 920 GeV protons with carbon and titanium targets. We obtained R χ c = 0.32±0.06 stat ±0.04 sys for the fraction of J / ψ from χ c decays averaged over proton–carbon and proton–titanium collisions. This result is in agreement with previous measurements and is compared with theoretical predictions
Inclusive V 0 production cross sections from 920 GeV fixed target proton-nucleus collisions
No full textInclusive differential cross sections dσpA/dxF and dσpA/dp2t
for the production of K0S, Λ, and Λ particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to √s = 41.6 GeV in the proton-nucleon system. The ratios of differential cross sections dσpA(K0 S)/dσpA(Λ) and dσpA( ¯ Λ)/dσpA(Λ) are measured to be 6.2 ± 0.5 and 0.66 ± 0.07, respectively, for xF ≈−0.06. No significant dependence upon the target material is observed.
Within errors, the slopes of the transverse momentum distributions dσpA/dp2t also show no significant
dependence upon the target material. The dependence of the extrapolated total cross sections σpA on the atomic mass A of the target material is discussed, and the deduced cross sections per nucleon σpN are compared with results obtained at other energies
Track finding at 10MHz hadronic event rate
No full textHera-B is a fixed target experiment using a halo target inside the HERA proton ring to generate B mesons in 920 GeV proton- nucleus interactions. The first-level trigger (FLT) (see Table I for a list of the acronyms used in this paper) of the experiment has to reduce the primary 10-MHz input rate by a factor 200 in less than 10 mus to make it acceptable to the second level trigger (SLT). The trigger strategy is based on the tracking of charged particles and on the reconstruction of their kinematic parameters. The combination of track pairs can also be used for the final decision. A parallel and pipelined set of approximately 60 dedicated boards was designed and built to perform this job. In this paper, the working principle of the system and some results obtained by analyzing the data collected during the run in the year 2000 are described
Measurement of , , and Production in Fixed Target 920-GeV Proton-Nucleus Collisions.
No full textUdgivelsesdato: October
and Meson Production in Proton-Nucleus Interactions at ~GeV.
No full textThe inclusive production cross sections of the strange vector mesons K*0, K̄*0, and φ have been measured in interactions of 920 GeV protons with C, Ti, and W targets with the HERA-B detector at the HERA storage ring. Differential cross sections as a function of rapidity and transverse momentum have been measured in the central rapidity region and for transverse momenta up to pT = 3.5 GeV/c. The atomic number dependence is parametrised as σpA=σpN*Aα, where σpN is the proton–nucleon cross section. Within the phase space accessible, α(K*0)=0.86±0.03, α(K̄*0)=0.87±0.03, and α(φ)=0.96±0.02. The total proton–nucleon cross sections, determined by extrapolating the differential measurements to full phase space, are σpN→K*0=(5.06±0.54) mb, σpN→K̄*0=(4.02±0.45) mb, and σpN→φ=(1.17±0.11) mb. For all resonances the Cronin effect is observed; compared to the measurements of Cronin et al. for K± mesons, the measured values of α for φ mesons coincide with those of K+ mesons for all transverse momenta, while the enhancement for K*0/K̄*0 mesons is smaller
