82 research outputs found
First Measurement of the Transverse Spin Asymmetries of the Deuteron in Semi-Inclusive Deep Inelastic Scattering
First measurements of the Collins and Sivers asymmetries of charged hadrons
produced in deep-inelastic scattering of muons on a transversely polarized
6-LiD target are presented. The data were taken in 2002 with the COMPASS
spectrometer using the muon beam of the CERN SPS at 160 GeV/c. The Collins
asymmetry turns out to be compatible with zero, as does the measured Sivers
asymmetry within the present statistical errors.Comment: 6 pages, 2 figure
The COMPASS Experiment at CERN
The COMPASS experiment makes use of the CERN SPS high-intensitymuon and
hadron beams for the investigation of the nucleon spin structure and the
spectroscopy of hadrons. One or more outgoing particles are detected in
coincidence with the incoming muon or hadron. A large polarized target inside a
superconducting solenoid is used for the measurements with the muon beam.
Outgoing particles are detected by a two-stage, large angle and large momentum
range spectrometer. The setup is built using several types of tracking
detectors, according to the expected incident rate, required space resolution
and the solid angle to be covered. Particle identification is achieved using a
RICH counter and both hadron and electromagnetic calorimeters. The setup has
been successfully operated from 2002 onwards using a muon beam. Data with a
hadron beam were also collected in 2004. This article describes the main
features and performances of the spectrometer in 2004; a short summary of the
2006 upgrade is also given.Comment: 84 papes, 74 figure
The LHCb Silicon Tracker
The Silicon Tracker is a large-surface silicon micro-strip detector that covers the full acceptance of the experiment in a single tracking station upstream of the spectrometer magnet and the inner-most part of the three tracking stations downstream of the magnet. Special emphasis has been put on module quality assurance at all stages of the production. Various tests are performed after each production step and each module goes through several burn-in cycles. The design of the LHCb silicon detectors is described and the main lessons learnt from the R&D phase are summarized. Focus will be on the experience from module production and the quality assurance program
Gluon polarization in the nucleon from quasi-real photoproduction of high-pT hadron pairs
We present a determination of the gluon polarization Delta G/G in the
nucleon, based on the helicity asymmetry of quasi-real photoproduction events,
Q^2<1(GeV/c)^2, with a pair of large transverse-momentum hadrons in the final
state. The data were obtained by the COMPASS experiment at CERN using a 160 GeV
polarized muon beam scattered on a polarized 6-LiD target. The helicity
asymmetry for the selected events is = 0.002 +- 0.019(stat.) +-
0.003(syst.). From this value, we obtain in a leading-order QCD analysis Delta
G/G=0.024 +- 0.089(stat.) +- 0.057(syst.) at x_g = 0.095 and mu^2 =~ 3
(GeV}/c)^2.Comment: 10 pages, 3 figure
Design and Production of Detector Modules for the LHCb Silicon Tracker
The LHCb Silicon Tracker will cover a sensitive surface of about 12 m^2 with silicon micro-strip detectors. The production of detector modules is currently coming close to its conclusion. In this paper, the design of the detector modules, the main module production steps, and the module quality assurance programme are described. Selected results from the quality assurance are shown and first lessons are drawn from the experience gained during module production. Presented at the 6th International ``Hiroshima'' Symposium on the Development and Application of Semiconductor Tracking Detectors, Carmel, California, September 11-15, 2006; proceedings submitted for publication in Nucl. Instr. and Meth.~
Performance of Long Ladders for the LHCb Silicon Tracker
The LHCb Silicon Tracker uses detector ladders with readout strips with an effective length of up to 36,cm. Kapton interconnect cables of up to 54,cm in length are employed in between silicon sensors and front-end readout hybrids. Fast front-end readout electronics with a shaping time of around 25,ns are employed to avoid pile-up of events from consecutive LHC bunch crossings. An extensive measurement program as well as simulations have been carried out to study the expected noise performance of these detectors. Presented at the 14th International Workshop on Vertex Detectors, Chuzenji Lake, Nikko, Japan, November 7-11, 2005 Proceedings submitted for publication in Nucl. Instr. and Meth.
A new measurement of the Collins and Sivers asymmetries on a transversely polarised deuteron target
New high precision measurements of the Collins and Sivers asymmetries of
charged hadrons produced in deep-inelastic scattering of muons on a
transversely polarised 6LiD target are presented. The data were taken in 2003
and 2004 with the COMPASS spectrometer using the muon beam of the CERN SPS at
160 GeV/c. Both the Collins and Sivers asymmetries turn out to be compatible
with zero, within the present statistical errors, which are more than a factor
of 2 smaller than those of the published COMPASS results from the 2002 data.
The final results from the 2002, 2003 and 2004 runs are compared with naive
expectations and with existing model calculations.Comment: 40 pages, 28 figure
The Deuteron Spin-dependent Structure Function g1d and its First Moment
We present a measurement of the deuteron spin-dependent structure function
g1d based on the data collected by the COMPASS experiment at CERN during the
years 2002-2004. The data provide an accurate evaluation for Gamma_1^d, the
first moment of g1d(x), and for the matrix element of the singlet axial
current, a0. The results of QCD fits in the next to leading order (NLO) on all
g1 deep inelastic scattering data are also presented. They provide two
solutions with the gluon spin distribution function Delta G positive or
negative, which describe the data equally well. In both cases, at Q^2 = 3
(GeV/c)^2 the first moment of Delta G is found to be of the order of 0.2 - 0.3
in absolute value.Comment: fits redone using MRST2004 instead of MRSV1998 for G(x), correlation
matrix adde
Measurement of the Spin Structure of the Deuteron in the DIS Region
We present a new measurement of the longitudinal spin asymmetry A_1^d and the
spin-dependent structure function g_1^d of the deuteron in the range 1 GeV^2 <
Q^2 < 100 GeV^2 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
6-LiD 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.Comment: 10 pages, 6 figures, subm. to PLB, revised: author list, Fig. 4,
details adde
Production, Commissioning and First Data of the LHCb Silicon Tracker
We give here a short review of the LHCb Silicon Tracker, the main points of the module production and quality control, followed by the commissioning of the detector. Problems that were found during production or commissioning are described and the first performance assessment of the installed detector with “beam data” is given
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