Observation of a New Type of Low Frequency Waves at Comet 67P/Churyumov-Gerasimenko

We report on magnetic field measurements made in the innermost coma of 67P/Churyumov-Gerasimenko in its low activity state. Quasi-coherent, large-amplitude ($\delta B/B \sim 1$), compressional magnetic field oscillations at $\sim$ 40 mHz dominate the immediate plasma environment of the nucleus. This differs from previously studied comet-interaction regions where waves at the cometary ion gyro-frequencies are the main feature. Thus classical pick-up ion driven instabilities are unable to explain the observations. We propose a cross-field current instability associated with newborn cometary ion currents as a possible source mechanism.Comment: 6 pages, 3 Figure

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

A Statistical Method for Luminosity Monitoring in High Energy Collider Experiments.

A statistical method which uses a combination of two subdetectors to monitor the luminosity in high energy interactions is presented. To illustrate its performance, this method was applied to random triggered minimum bias data collected in the commissioning period of the HERA-B experiment in spring 2000. It is found that luminosity estimates with an intrinsic systematic error of 3% can be obtained

A Statistical Method for Luminosity Monitoring in High Energy Collider Experiments.

A statistical method which uses a combination of two subdetectors to monitor the luminosity in high energy interactions is presented. To illustrate its performance, this method was applied to random triggered minimum bias data collected in the commissioning period of the HERA-B experiment in spring 2000. It is found that luminosity estimates with an intrinsic systematic error of 3% can be obtained

Characterization of silicon microstrip detectors using an infrared laser system

An infrared laser system with variable wavelength is used to study fundamental properties of silicon microstrip detectors. Results of measurements concerning charge sharing among adjacent readout strips and depletion mapping are presented. The results are interpreted in a model framework which describes the charge sharing with the help of the so-called η-function. The wavelength dependence of the η-function is studied. Surface effects important for short wavelengths are observed

Radiation hardness of the HERA-B double-sided silicon strip detectors

Irradiation studies of double-sided silicon strip-detectors for the HERA-B experiment have been performed using a setup at a 21 MeV proton beam. A novel method of fluence monitoring has been implemented. The study presented here gives results of a non- uniform irradiation of two HERA-B detector modules built with double-sided detectors made of oxygenated as well as non- oxygenated wafers. The maximum exposed fluence corresponds to about 3 x 10(14) MIP/cm(2). The characterization of the detectors was done with a laser and a Ru-106 source. In regions of low-radiation dose, signal over noise ratios of 22 and 16 were measured for n- and p-side, respectively. In the region of maximum fluence, SIN values of approximate to17 and approximate to15 were obtained at a bias voltage of 450 V for n- and p- strips, respectively. Our measurements establish for both detector types full functionality at fluences varying by two orders of magnitude. Standard and oxygenated detectors do not show any significant difference. (C) 2002 Elsevier Science B.V. All rights reserved