Journal
PHYSICS LETTERS B
Volume 693, Issue 3, Pages 227-235Publisher
ELSEVIER
DOI: 10.1016/j.physletb.2010.08.034
Keywords
COMPASS; Semi-inclusive deep inelastic scattering; Spin; Structure function; Parton distribution functions
Funding
- Czech Republic MEYS [ME492, LA242]
- SAIL (CSR), Govt. of India
- CERN-RFBR [08-02-91009]
- Portuguese Fa - Fundacao para a Ciencia e Tecnologia [POCTI/FNU/49501/2002, POCTI/FNU/50192/2003]
- MEXT
- JSPS [18002006, 20540299, 18540281]
- Daiko Foundation and Yamada Foundation
- DFG
- Israel Academy of Sciences and Humanities
- Ministry of Science and Higher Education [41/N-CERN/2007/0]
- Fundação para a Ciência e a Tecnologia [POCTI/FNU/49501/2002] Funding Source: FCT
- Grants-in-Aid for Scientific Research [18002006, 18540281, 20540299] Funding Source: KAKEN
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Double-spin asymmetries for production of charged pions and kaons in semi-inclusive deep-inelastic muon scattering have been measured by the COMPASS experiment at CERN. The data, obtained by scattering a 160 GeV muon beam off a longitudinally polarised NH3 target, cover a range of the Bjorken variable x between 0.004 and 0.7. A leading order evaluation of the helicity distributions for the three lightest quarks and antiquark flavours derived from these asymmetries and from our previous deuteron data is presented. The resulting values of the sea quark distributions are small and do not show any sizable dependence on x in the range of the measurements. No significant difference is observed between the strange and antistrange helicity distributions, both compatible with zero. The integrated value of the flavour asymmetry of the helicity distribution of the light-quark sea, Delta(u) over bar - Delta(d) over bar, is found to be slightly positive, about 1.5 standard deviations away from zero. (C) 2010 Elsevier B.V. All rights reserved.
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