First experience and results from the HERA- B vertex detector system Bauer, C.; Baumann, I.; Bräuer, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/1998, Letnik:
418, Številka:
1
Journal Article
Recenzirano
The HERA-
B collaboration is building a detector to realize the ambitious goal of observing CP violation in decays of neutral B-mesons. A central element of the apparatus is the silicon vertex ...detector used to selectively trigger on these decays in a high charged particle multiplicity background environment and to reconstruct secondary vertices from such decays with high precision. The vertex detector, the supporting infrastructure and first results using prototype detectors are described. Results include imaging of the proton interaction region on the HERA-
B target, hit distributions in the detector planes, and alignment of the detectors with each other and the target.
Test of internal halo targets in the HERA proton ring Hast, C.; Ehret, K.; Hofmann, W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/1995, Letnik:
354, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Internal wire targets in the halo of stored proton beams provide a line source of proton-nucleus interactions for highest-rate fixed target experiments. We have studied such internal halo targets at ...the 820 GeV proton ring of the HERA ep collider. The tests showed that most of the protons in the beam halo — which would otherwise hit the collimators — can be brought to interaction in a relatively thin target wire at distances of 7 to 8 beam widths from the center of the beam. At less than 10% of the HERA total design current, and less than 20% of the current per bunch, interaction rates up to 8 MHz were observed, corresponding to more than 2 interactions per bunch crossing. The halo targets were used in parallel to the HERA luminosity operation; no significant disturbances of the HERA ep experiments, of the machine stability or beam quality were observed. We present data on the steady-state and transient behaviour of interaction rates and discuss the interpretation in terms of a simple beam dynamics model. Issues of short-, medium- and long-term rate fluctuations and of rate stabilization by feedback are addressed.
Using data collected by the HERA-B experiment, we have measured the fraction of J/ψ's produced via radiative χc decays in interactions of 920 GeV protons with carbon and titanium targets. We obtained ...Rχc=0.32±0.06stat±0.04sys for the fraction of J/ψ from χc decays averaged over proton–carbon and proton–titanium collisions. This result is in agreement with previous measurements and is compared with theoretical predictions.
The tentacles of the terrestrial snail Achatina fulica contain an epithelium at their tips which is specialized for olfaction. The histology of the snail's olfactory organ bears a striking ...resemblance to that of the olfactory mucosa in the nose of vertebrates, where the receptor cell population is known to undergo a continuous process of renewal. In the present experiments, 3Hthymidine was delivered as a single pulse that was determined to have a maximum duration of about 1 h. Thirty minutes after an injection of 3Hthymidine, presumptive precursor cells were found labeled within, or at the edges of, receptor cell lobules. At later survival times, label was seen over cells that were identified as receptors. The mean position of the labeled cells within the layer of receptor cells became progressively more superficial with increasing survival times, indicating an upward migration of newly differentiated cells. The labeling index in the snail is ca. 0.7%, compared to 0.9% in the mouse. The turnover time is about 45 days, compared to 30-45 days in the mouse.
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.
The coastal areas of the Southern Baltic Sea are highly productive ecosystems due to a high nutrient loading via rivers, non-point sources and frequent upwelling. The organic carbon production of ...these areas contributes to final carbon deposition in deeper basins of the Southern Baltic Sea by horizontal near-bottom transport processes, followed by littoral secondary production and biogeochemical cycles in the deeper areas. Seasonal investigations concerning the major driving forces of primary and bacterial production at two Southern Baltic Sea coastal areas with different degrees of eutrophication have been performed. The hypertrophic study site, Koserow, influenced by high nutrient loading from the River Oder, was characterised by high primary production rates and high phytoplankton biomass, compared with the meso-/eutrophic site, Tromper Wiek. At both sites a typical seasonal phytoplankton succession was found. Numerical integration of phytoplankton photosynthesis showed that the plankton community at Koserow acted as a potential net source of organic matter whereas Tromper Wiek seemed to be a potential sink of organic carbon. At both study sites, bacterial secondary production was limited by temperature only, which could be explained by a high proportion of detritus associated bacteria, not directly dependent on DOM exudation of the phytoplankton community. This was supported by underwater camera observations and investigations of the benthic fauna, both indicating a high potential for aggregation and sedimentation.
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