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Title: Nucleon spin structure studies at COMPASS

Abstract

One of the main goal of the COMPASS experiment at CERN is the study of the spin structure of the nucleon in DIS, by scattering 160 GeV polarized muon beam on a longitudinally (or transversely) polarized 6LiD target. Besides the scattered muon, the particles produced in the deep inelastic scattering are detected by a two stage magnetic spectrometer equipped with state of the art tracking and particle ID detectors.The emphasis of COMPASS muon program is the direct determination of the gluon polarization {delta}G/G, accessed via asymmetries involving photon-gluon fusion mechanism (PGF). Both open charm production (detecting D0's), as well as production of height pT hadron pairs are used to tag PGF. Preliminary results for {delta}G/G based on the analysis of 2002 and 2003 data are shown. In addition, improved measurement of the deuteron structure function g{sub 1}{sup d} at small x, as well as studies of transverse distribution functions in the deuteron by measuring Collins and Sivers azimuthal asymmetries, are reported.

Authors:
 [1]
  1. CEA/DAPNIA/SPhN, CE Saclay, F-91191 Gif-sur-Yvette CEDEX (France)
Publication Date:
OSTI Identifier:
20798100
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 814; Journal Issue: 1; Conference: 11. international conference on hadron spectroscopy, Rio de Janeiro (Brazil), 21-26 Aug 2005; Other Information: DOI: 10.1063/1.2176512; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ASYMMETRY; CERN; DEEP INELASTIC SCATTERING; DEUTERONS; DISTRIBUTION FUNCTIONS; GEV RANGE; GLUONS; MAGNETIC SPECTROMETERS; MUON BEAMS; MUONS; NUCLEONS; PARTICLE STRUCTURE; PHOTONS; POLARIZATION; POLARIZED BEAMS; POLARIZED TARGETS; SPIN; STRUCTURE FUNCTIONS

Citation Formats

Marchand, Claude. Nucleon spin structure studies at COMPASS. United States: N. p., 2006. Web. doi:10.1063/1.2176512.
Marchand, Claude. Nucleon spin structure studies at COMPASS. United States. doi:10.1063/1.2176512.
Marchand, Claude. Sat . "Nucleon spin structure studies at COMPASS". United States. doi:10.1063/1.2176512.
@article{osti_20798100,
title = {Nucleon spin structure studies at COMPASS},
author = {Marchand, Claude},
abstractNote = {One of the main goal of the COMPASS experiment at CERN is the study of the spin structure of the nucleon in DIS, by scattering 160 GeV polarized muon beam on a longitudinally (or transversely) polarized 6LiD target. Besides the scattered muon, the particles produced in the deep inelastic scattering are detected by a two stage magnetic spectrometer equipped with state of the art tracking and particle ID detectors.The emphasis of COMPASS muon program is the direct determination of the gluon polarization {delta}G/G, accessed via asymmetries involving photon-gluon fusion mechanism (PGF). Both open charm production (detecting D0's), as well as production of height pT hadron pairs are used to tag PGF. Preliminary results for {delta}G/G based on the analysis of 2002 and 2003 data are shown. In addition, improved measurement of the deuteron structure function g{sub 1}{sup d} at small x, as well as studies of transverse distribution functions in the deuteron by measuring Collins and Sivers azimuthal asymmetries, are reported.},
doi = {10.1063/1.2176512},
journal = {AIP Conference Proceedings},
number = 1,
volume = 814,
place = {United States},
year = {Sat Feb 11 00:00:00 EST 2006},
month = {Sat Feb 11 00:00:00 EST 2006}
}
  • The COMPASS experiment at CERN investigates nucleon structure and spectroscopy with high-intensity muon and hadron beams. Between 2002 and 2004 COMPASS has mainly concentrated on the spin structure of the nucleon via deep-inelastic scattering of polarized muons on polarized nucleons. First results include measurements of the gluon contribution to the nucleon spin via charm production and high-pt pairs, {lambda} polarization, vector-meson production, Collins and Sivers asymmetries, inclusive and semi-inclusive deep-inelastic scattering asymmetries and a search for pentaquark states. A short overview of these results is presented.
  • Highlights of the nucleon spin studies from the COMPASS experiment at CERN are presented. Three independent measurements of the gluon polarization give values compatible with zero for x close to 0.1. The quark helicity distributions are determined for all flavors. On the transversity side, Collins and Sivers asymmetries are measured for proton and deuteron targets. Plans for COMPASS-II include DVCS as well as polarized Drell-Yan measurements.
  • An overview of the muon part of the COMPASS results related to the spin structure of the nucleon is given.
  • The measurement of the gluon contribution to the nucleon spin {delta}G is one of the main goals of the COMPASS experiment located at the CERN Super Proton Synchrotron. The key reaction is the photon gluon fusion to D (D-bar) -mesons. The status of the analysis of the D0- and D*-events is shown as well as the expected statistical error of {delta}G/G from the first 3 years of data taking.
  • A new measurement of the longitudinal spin asymmetry A{sub 1}{sup d} and the spin dependent structure function g{sub 1}{sup d} of the deuteron is presented in the Q2 range from 1GeV2 to 100GeV2 and the x range from 0.004 to 0.7. The data were taken in 2002 and 2003 with the COMPASS experiment at CERN, scattering 160 GeV2 polarised muons off a large polarised 6LiD target. While significantly improving statistical accuracy in the low x region the data agree nicely with previous experiments.