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Title: Boer-Mulders effect in unpolarized SIDIS: An analysis of the COMPASS and HERMES data on the $$\cos 2 \phi$$ asymmetry

We present a phenomenological analysis of the $$\cos 2 \phi$$ asymmetry recently measured by the COMPASS and HERMES collaborations in unpolarized semi-inclusive deep inelastic scattering. In the kinematical regimes explored by these experiments the asymmetry arises from transverse-spin and intrinsic transverse-momentum effects. We consider the leading-twist contribution, related to the so-called Boer-Mulders transverse-polarization distribution $$h_1^{\perp}(x, k_T^2)$$, and the twist-4 Cahn contribution, involving unpolarized transverse-momentum distribution functions. We show that a reasonably good fit of the data is achieved with a Boer-Mulders function consistent with the main theoretical expectations. Lastly, our conclusion is that the COMPASS and HERMES measurements represent the first experimental evidence of the Boer-Mulders effect in SIDIS.
Authors:
;  [1] ;  [2]
  1. Univ. del Piemonte Orientale "A. Avogadro", and INFN, Gruppo Collegato di Alessandria, Alessandria (Italy)
  2. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Publication Date:
OSTI Identifier:
982198
Report Number(s):
JLAB-THY--09-1121; DOE/OR/23177--1071
Journal ID: ISSN 1550-7998; PRVDAQ; TRN: US201013%%358
Grant/Contract Number:
AC05-06OR23177
Type:
Accepted Manuscript
Journal Name:
Physical Review. D, Particles, Fields, Gravitation and Cosmology
Additional Journal Information:
Journal Volume: 81; Journal Issue: 11; Journal ID: ISSN 1550-7998
Publisher:
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ASYMMETRY; DEEP INELASTIC SCATTERING; DISTRIBUTION; DISTRIBUTION FUNCTIONS; TRANSVERSE MOMENTUM