Measurement of the deuteron spin structure function g x 1 2 2 2 for 1 GeV c Q 40 GeV c

C New D measurements are reported on the deuteron spin structure function g E d F . These results were obtained from deep 1 inelastic scattering of 48.3 GeV electrons on polarized deuterons in the kinematic range 0.01 G x H I 0.9 J and 1 K Q L 2 M 40 N O 2 P 6 2 Q R GeV S T c U . These are the first high dose electron scattering data obtained using lithium deuteride Li H as the target material. Extrapolations of the data were performed to obtain moments of g E d F , V including W d F , V and the net quark polarization 1 1 X Y . Z 1999 Elsevier Science B.V. All rights reserved. PACS: 13.88. [ e; 13.60.Hb; 27.10. \ h; 29.25.Pj ] ^ Polarized deep inelastic scattering 1–5 is a powerful _ tool for studying the internal spin structure of the ` proton and neutron. The longitudinal spin struca 2 b c ture ` function g x d ,Q so obtained is sensitive to the 1 e 2 b f g h 2 b i quark j spin distributions k q x l ,Q m q x l ,Q n o p 2 b q r s q x l ,Q , where the up down arrow refers to t u quark j polarization parallel anti-parallel to the nucleon v polarization. These quantities depend on x w , the fractional momentum carried by the struck parton, and x Q b , the four-momentum transfer squared of the exchanged _ virtual photon. In this Letter, we report on y new precision measurements of the deuteron spin structure function g d d z from the SLAC E155 experi1 ment, which ran in early 1997. These measurements, covering v the range 0.01 { x w | 0.9 } and 1 ~ Q  40 €  2 GeV ‚ ƒ c v , are a significant improvement over previ„ … ous y deuteron measurements at SLAC 1 . E155 is the first † high dose electron scattering experiment to use 6 2 ‡ ˆ 6 ‡ ‰ polarized Š Li H i.e. LiD as the deuteron target 1 Present address: College of William and Mary, Williamsburg, Virginia 23187. 2 Permanent Address: Institut des Sciences Nucleaires, ́ IN2P3‹ CNRS, 38026 Grenoble Cedex, France. 3 Œ Present Address: Duke University, TUNL, Durham, North Carolina 27708. 4  Present Address: St. Norbert College, De Pere, Wisconsin 54115. 5 Ž Present Address: Lawrence Livermore National Laboratory, Livermore, California 94551. material.  These data on an isoscalar target provide a particularly Š strong constraint on the net quark polarization,  ‘ ’ “ ” u • – — d ˜ ™ s š . The › ratio of g d to ` the unpolarized structure func1 tion ` F œ can v be determined from measured longitudi1 nal  asymmetries A ž using Ÿ g d ¡ F ¢ A £ d ¤ g d ¥ F 2 Mx ¦ 2 E § ̈ , © a « ¬ ­ ®