50 research outputs found
Inclusive Production Cross Sections from 920 GeV Fixed Target Proton-Nucleus Collisions
Inclusive differential cross sections and
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
GeV in the proton-nucleon system. The ratios of differential
cross sections \rklpa and \rllpa are measured to be and , respectively, for \xf . No significant dependence upon the
target material is observed. Within errors, the slopes of the transverse
momentum distributions also show no significant
dependence upon the target material. The dependence of the extrapolated total
cross sections on the atomic mass of the target material is
discussed, and the deduced cross sections per nucleon 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
Dispersion relation analysis of turbulent magnetic field fluctuations in fast solar wind
Physical processes of the energy transport in solar wind turbulence are a subject of intense studies, and different
ideas exist to explain them. This manuscript describes the investigation of dispersion properties in short-wavelength
magnetic turbulence during a rare high-speed solar wind event with a flow
velocity of about 700 km s<sup>−1</sup> using magnetic field and ion data from the Cluster spacecraft. Using the multi-point
resonator technique, the dispersion relations (i.e., frequency versus wave-number values in the solar wind frame) of
turbulent magnetic fluctuations with wave numbers near the inverse ion inertial length are determined. Three major
results are shown: (1) the wave vectors are uniformly quasi-perpendicular to the mean magnetic field; (2) the
fluctuations show a broad range of frequencies at wavelengths around the ion inertial length; and (3) the direction of
propagation
at the observed wavelengths is predominantly in the sunward direction. These results suggest the
existence of high-frequency dispersion relations partly associated with normal modes on small scales.
Therefore nonlinear energy cascade processes seem to be acting that are not described by wave–wave interactions
Dispersion relation analysis of turbulent magnetic field fluctuations in fast solar wind
Physical processes of the energy transport in solar
wind turbulence are a subject of intense studies, and different
ideas exist to explain them. This manuscript describes the investigation
of dispersion properties in short-wavelength magnetic
turbulence during a rare high-speed solar wind event
with a flow velocity of about 700 km s−1 using magnetic field
and ion data from the Cluster spacecraft. Using the multipoint
resonator technique, the dispersion relations (i.e., frequency
versus wave-number values in the solar wind frame)
of turbulent magnetic fluctuations with wave numbers near
the inverse ion inertial length are determined. Three major
results are shown: (1) the wave vectors are uniformly quasiperpendicular
to the mean magnetic field; (2) the fluctuations
show a broad range of frequencies at wavelengths around the
ion inertial length; and (3) the direction of propagation at the
observed wavelengths is predominantly in the sunward direction.
These results suggest the existence of high-frequency
dispersion relations partly associated with normal modes on
small scales. Therefore nonlinear energy cascade processes
seem to be acting that are not described by wave–wave interactions
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