Inclusive V0V^0 Production Cross Sections from 920 GeV Fixed Target Proton-Nucleus Collisions

Inclusive differential cross sections $d\sigma_{pA}/dx_F$ and $d\sigma_{pA}/dp_t^2$ for the production of \kzeros, \lambdazero, and \antilambda 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 $\sqrt {s} = 41.6$ GeV in the proton-nucleon system. The ratios of differential cross sections \rklpa and \rllpa are measured to be $6.2\pm 0.5$ and $0.66\pm 0.07$, respectively, for \xf $\approx-0.06$. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions $d\sigma_{pA}/dp_t^2$ also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections $\sigma_{pA}$ on the atomic mass $A$ of the target material is discussed, and the deduced cross sections per nucleon $\sigma_{pN}$ are compared with results obtained at other energies.Comment: 17 pages, 7 figures, 5 table

The QCD transition temperature: results with physical masses in the continuum limit II.

We extend our previous study [Phys. Lett. B643 (2006) 46] of the cross-over temperatures (T_c) of QCD. We improve our zero temperature analysis by using physical quark masses and finer lattices. In addition to the kaon decay constant used for scale setting we determine four quantities (masses of the \Omega baryon, K^*(892) and \phi(1020) mesons and the pion decay constant) which are found to agree with experiment. This implies that --independently of which of these quantities is used to set the overall scale-- the same results are obtained within a few percent. At finite temperature we use finer lattices down to a <= 0.1 fm (N_t=12 and N_t=16 at one point). Our new results confirm completely our previous findings. We compare the results with those of the 'hotQCD' collaboration.Comment: 19 pages, 8 figures, 3 table

Aufbau und Charakterisierung des schnellen Kontrollsystem fuer das Experiment HERA - B

The experiment HERA-B is currently under construction at the Deutsches Elektronen Synchrotron DESY in Hamburg and, upon completion, will investigate CP-violation in decays of B-mesons. The central challenges for this experiment are a high density of particle tracks in the detector (about 200 tracks per event) and an extremely small signal-to-background-ratio (10&quot;-&quot;1&quot;1 for the decay channel B#-&gt;#J/#psi#K_s&quot;0#-&gt;#l&quot;+l&quot;-#pi#&quot;+#pi#&quot;-). Data from 540,000 channels must be processed an event rate of 10 MHz and a first level trigger rate of 50 kHz without deadtime. A novel fast control system has been developed to distribute time references, trigger information and test signals to the front end electroncis of all detector components as well as for some first level trigger control functions. This thesis starts with an introduction to the experiment and a detailed description of the data acquisition system which leads to the requirements for the fast control system. The motivation is followed by a description of the fast control hard- and software. The time references and trigger signals, which are distributed by the system, are characterized. Successful synchronization of the detector components is shown by means of data from the 1998 HERA - B -operation. Finally some possibilities the system provides for investigating the first level trigger and potential biases the fast control system might give to HERA - B measurements are discussed. (orig.)SIGLEAvailable from TIB Hannover: RR 8919(1999-016) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

The Outer Tracker Detector of the HERA-B Experiment. Part III: Operation and Performance.

In this paper we describe the operation and performance of the HERA-B Outer Tracker, a 112674 channel system of planar drift tube layers. The performance of the HERA-B Outer Tracker system fullfilled all requirements for stable and efficient operation in a hadronic environment, thus confirming the adequacy of the honeycomb drift tube technology and of the front-end readout system. The detector was stably operated with a gas gain of 30000 in an Ar/CF4/CO2 (65:30:5) gas mixture, yielding a good efficiency for triggering and track reconstruction, larger than 95 % for tracks with momenta above 5 GeV/c. The hit resolution of the drift cells was 300 to 320 micrometers and the relative momentum resolution can be described as: sigma(p)/p (in %) = (1.61 +- 0.02) + (0.0051 +- 0.0006) p. At the end of the HERA-B running no aging effects in the Outer Tracker cells were observed.Comment: 38 pages, 20 figures. v2: Added clarifications about trigger efficiency, momentum resolution and alignment precision. Corrected typos. Improved figure qualit

J/ψJ/\psi production via chi(cc) decays in 920-GeV pA interactions

Using 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