A scintillating fibre hodoscope for high rate applications Bisplinghoff, J; Eversheim, D; Eyrich, W ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2002, Letnik:
490, Številka:
1
Journal Article
Recenzirano
A scintillating fibre hodoscope was developed for application in a high rate environment such as the central region of external beam experiments. It accommodates rates of several
10
6
s
−1
per fibre ...channel while maintaining a time resolution of about
400
ps
. Its central elements are highly efficient radiation-hard scintillating fibres and a photomultiplier tube capable of operating at such rates without appreciable loss of signal amplitude.
We present a new measurement of the longitudinal spin asymmetry A1d and the spin-dependent structure function g1d of the deuteron in the range 1<Q2<100 GeV2 and 0.004<x<0.7. The data were obtained by ...the COMPASS experiment at CERN using a 160 GeV polarised muon beam and a large polarised 6LiD target. The results are in agreement with those from previous experiments and improve considerably the statistical accuracy in the region 0.004<x<0.03.
The first detailed measurement of the dependence on target nuclear mass of the average squared transverse momentum 〈pt2〉 of π+, π−, and K+ mesons from deep-inelastic lepton scattering is obtained as ...a function of several kinematic variables. The data were accumulated at the Hermes experiment at Desy, in which the Hera 27.6 GeV lepton beam was scattered off several nuclear gas targets. The average squared transverse momentum was clearly observed to increase with atomic mass number. The effect increases as a function of Q2 and x and remains constant as a function of both the virtual photon energy ν and the fractional hadron energy z, except that it vanishes as z approaches unity.
Observations of the globular clusters (GCs) NGC 6388 and M15 were carried out by the High Energy Stereoscopic System array of Cherenkov telescopes for a live time of 27.2 and 15.2 hr, respectively. ...No gamma-ray signal is found at the nominal target position of NGC 6388 and M15. In the primordial formation scenario, GCs are formed in a dark matter (DM) halo and DM could still be present in the baryon-dominated environment of GCs. This opens the possibility of observing a DM self-annihilation signal. The DM content of the GCs NGC 6388 and M15 is modeled taking into account the astrophysical processes that can be expected to influence the DM distribution during the evolution of the GC: the adiabatic contraction of DM by baryons, the adiabatic growth of a black hole in the DM halo, and the kinetic heating of DM by stars. Ninety-five percent confidence level exclusion limits on the DM particle velocity-weighted annihilation cross section are derived for these DM halos. In the TeV range, the limits on the velocity-weighted annihilation cross section are derived at the 10--25 cm3 s--1 level and a few 10--24 cm3 s--1 for NGC 6388 and M15, respectively.
Longitudinal double-spin asymmetries of charged hadrons with high transverse momentum
p
T
have been measured in electroproduction using the H
ermes
detector at H
era
. Processes involving gluons in ...the nucleon have been enhanced relative to others by selecting hadrons with
p
T
typically above 1 GeV. In this kinematic domain the gluon polarization has been extracted in leading order making use of the model embedded in the Monte Carlo Generator P
ythia
6.2. The gluon polarization obtained from single inclusive hadrons in the
p
T
range 1 GeV <
p
T
< 2.5 GeV using a deuterium target is
at a scale
and
. For different final states and kinematic domains, consistent values of
have been found within statistical uncertainties using hydrogen and deuterium targets.
Hard exclusive electroproduction of
ω
mesons is studied with the HERMES spectrometer at the DESY laboratory by scattering 27.6 GeV positron and electron beams off a transversely polarized hydrogen ...target. The amplitudes of five azimuthal modulations of the single-spin asymmetry of the cross section with respect to the transverse proton polarization are measured. They are determined in the entire kinematic region as well as for two bins in photon virtuality and momentum transfer to the nucleon. Also, a separation of asymmetry amplitudes into longitudinal and transverse components is done. These results are compared to a phenomenological model that includes the pion pole contribution. Within this model, the data favor a positive
π
ω
transition form factor.
A recoil detector will be installed surrounding the internal gas target of the HERMES experiment at DESY. The recoil detector will improve the selection of exclusive events by a direct measurement of ...the momentum and track direction of the recoiling particle. The innermost layer of this recoil detector is a new silicon strip detector (SSD). Since Monte Carlo simulations predict proton momenta as low as 100 MeV/c, the SSD will be placed inside the HERA vacuum. A new setup of the electronics enables a dynamic range from below 4 fC at a signal-to-noise ratio of 6.8 up to 270 fC. In this paper, the assembly of the first module and the final setup within the HERMES experiment will be presented. Results from charge-injection tests of a prototype module are given.
Polarisation asymmetries are measured for the hard exclusive leptoproduction of real photons from a longitudinally polarised hydrogen target. These asymmetries arise from the deeply virtual Compton ...scattering and Bethe-Heitler processes. From the data are extracted two asymmetries in the azimuthal distribution of produced real photons about the direction of the exchanged virtual photon:
with respect to the target polarisation and
with respect to the product of the beam and target polarisations. Results for both asymmetries are compared to the predictions from a generalised parton distribution model. The sin φ and cos(0φ) amplitudes observed respectively for the
and
asymmetries are compatible with the sizeable predictions from the model. Unexpectedly, a sin(2φ) modulation in the
asymmetry with a magnitude similar to that of the sin φ modulation is observed.
Azimuthal asymmetries in exclusive electroproduction of a real photon from a longitudinally polarized deuterium target are measured with respect to target polarization alone and with respect to ...target polarization combined with beam helicity and/or beam charge. The asymmetries appear in the distribution of the real photons in the azimuthal angle
ϕ around the virtual photon direction, relative to the lepton scattering plane. The asymmetries arise from the deeply virtual Compton scattering process and its interference with the Bethe–Heitler process. The results for the beam-charge and beam-helicity asymmetries from a tensor polarized deuterium target with vanishing vector polarization are shown to be compatible with those from an unpolarized deuterium target, which is expected for incoherent scattering dominant at larger momentum transfer. Furthermore, the results for the single target-spin asymmetry and for the double-spin asymmetry are found to be compatible with the corresponding asymmetries previously measured on a hydrogen target. For coherent scattering on the deuteron at small momentum transfer to the target, these findings imply that the tensor contribution to the cross section is small. Furthermore, the tensor asymmetry is found to be compatible with zero.
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