Combined analysis of world data on nucleon spin structure functions

We analyse the proton, deuteron and neutron spin dependent structure functions at fixed Q^2 = 5 GeV^2. The experimental asymmetries for the proton, neutron and deuteron are compared and found to be consistent. The first moment of the neutron structure function is evaluated using all available data. We find that the Bjorken sum rule is confirmed within an experimental uncertainty of 17%. The quark spin contribution to the nucleon spin is small, and the strange quark spin content is different from zero. Physics Letters B 320 (1994) 400-406 PHYSICS LETTERS B North-Holland Combined analysis of world data on nucleon spin structure functions Spin M u o n Collaborat ion (SMC) B. Adeva s, S. A h m a d q, A. Arvidson v, B. Badelek v,x, M.K. Ballintijn n, G. Bardin r, G. Baum a, P. Berglund g, L. Betev e, I.G. Bird r,l, R. Birsa u, P. Bj6rkholm v, B.E. Bonner q, N. de Botton r, M. Bou temeur y,2, F. Bradamante u, A. Bressan u, A. BriJll e,3, j. Buchanan q, S. Bti l tmann a, E. Burtin r, C. Cavata r, j .p . Chen w, j . Clement q, M. Clocchiatt i u, M.D. Corcoran q, D. Crabb w, J. Cranshaw q, T. f fuhadar d,4, S. Dalla Torre" , R. van Dantzig n, D. Day w, S. Dhawan Y, C. Dulya b, A. Dyring v, S. Eichblatt q, J.C. Faivre r, D. FaschingP, F. Feinstein r, C. Fernandez s,h, B. Frois r, C. Garabatos s,1, J.A. Garzon s,h, T. Gaussiran q, M. Giorgi u, E. von Goeler °, A. Gomez s,h, G. Gracia s, M. Grosse Pe rdekamp b, D. von HarrachJ, T. Hasegawa m,5, N. Hayashi m, C.A. Heusch c, N. Horikawa ra V.W. Hughes Y, G. lgo b, S. I sh imoto m'6, T. Iwata m, M. de JongJ, E.M. Kabul3J, R. Kaiser e, A. Karev i, H.J. Kessler e, T.J. Ketel n, A. Kishi m, Yu. Kisselev i, L. Klos te rmann n, V. Krivokhi j ine i, V. Kukht in i, J. Kyyn~ir~iinen d,g, M. L a m a nna u, U. Landgraf e, K. Lau h, T. Layda e, F. Lehar r, A. de Lesquen r, j. Lichtenstadt t, T. Lindqvist v, M. Li tmaath n, S. Lopez-Ponte s,h, M. Lowe q, A. Magnon d,r, G.K. MallotJ, F. Marie r, A. Mart in ~, J. Mar t ino ~, B. Mayes h, J.S. McCar thy w, G. van Midde lkoop n, D. Miller P, J. Mitchell w, K. Mori m, J. Moromisa to °, G.S. Mutchlerq, J. Nassalski x, L. N a u m a n n d, T.O. Niinikoski d, J.E.J. Oberski n, S. Okumi m, A. Penzo u, G. Perez c,7, F. Per ro t -Kunne r, D. Peshekhonov i, R. Piegaia d,8, L. Pinsky h, S. Pla tchkov r, M. PIo s, D. Pose i, H. Pos tma n, T. Pussieux r, j. Pyrlik h, J.M. Rieubland d, A. Rijllart d, J.B. Roberts q, M. Rodriguez s, E. Rond io x, L. Ropelewski x, A. Rosado l, I. Sabo t, j. Saborido s, A. Sandacz x, D. Sanders h, I. Savin i, P. Schiavon u, K.P. Sch/iler y,9, R. Segel p, R. SeitzJ, S. Sergeev i, F. Sever n,l°, P. Shanahan p, G. Smirnov i, A. Staude e, A. SteinmetzJ, H. S tuh rmann r, K.M. Teichert t, F. Tessarotto u, W. Thiel a, l l, S. Trentalange b, Y. Tzamouran i s h,12, M. Velasco P, J. Vogt e, R. Voss d, R. Weinstein h, C. Whi t ten b, R. Windmolders k, W. Wislicki x, A. Wi tzmann e, A. Yafiez s, A.M. Zanett i ~ and J. Zhao f a University of Bielefeld, Physics Department, 33615 Bielefeld 1, Germany 13 b University of California, Department of Physics, Los Angeles, 90024 CA, USA 14 c University of California, Institute of Particle Physics, Santa Cruz, 95064 CA, USA d CERN, 1211 Geneva 23, Switzerland e University of Freiburg, Physics Department, 79104 Freiburg, Germany 13 f GKSS, 21494 Geesthacht, Germany 13 s Helsinki University of Technology, Low Temperature Laboratory, Otakaari 3A, 02150 Finland h University of Houston, Department of Physics, llouston, 77204-5504 TX, USA and Institute for Beam Particle Dynamics, llouston, 77204-5506 TX, USA t4,15 i JINR, Laboratory of Super High Energy Physics, Dubna, Russia J University of Mainz, Institute for Nuclear Physics, 55099 ~llainz, Germany 13 k University of Mons, Faculty of Science, 7000 Mons, Belgium University of Munich, Physics Department, 80799 ?¢lunich, Germany 13 ra Nagoya University, Department of Physics, Furo-Cho, Chilcusa-Ku, 464 Nagoya, Japan 16 n NIKltEF, Delft University of Technology, FOM and Free University, 1009 AJ Amsterdam, The Netherlands 17 o Northeastern University, Department of Physics, Boston, 02115 MA, USA 15 400 Elsevier Science B.V. SSDI 0 3 7 0 2 6 9 3 ( 9 3 ) E I 5 5 8 F Volume 320, number 3,4 PHYSICS LETTERS B 13 January 1994 P Northwestern University, Department of Physics, Evanston, 60208 IL, USA 14,15 q Rice University, Bonner Laboratory, Houston, 77251-1892 TX, USA 14 r DAPNIA, CEN Saclay, 91191 Gifsur-Yvette, France s University of Santiago, Department of Particle Physics, 15706 Santiago de Compostela, Spain 18 t Tel Aviv University, School of Physics, 69978 Tel Aviv, Israel 19 u INFN Trieste and University" of Trieste, Department of Physics, 34127 Trieste, Italy v Uppsala University, Department of Radiation Sciences, 75121 Uppsala, Sweden w University of Virginia, Department of Physics, Charlottesville, 22901 VA, USA 15 x Warsaw University and Soltan Institute for Nuclear Studies, 00681 Warsaw, Poland 2° Y Yale University, Department of Physics, New Haven, 06511 CT, USA 14 Received 1 December 1993 Editor: L. Montanet We analyse the proton, deuteron and neutron spin dependent structure functions at fixed Q2 = 5 GeV 2. The experimental asymmetries for the proton, neutron and deuteron are compared and found to be consistent. The first moment of the neutron structure function is evaluated using all available data. We find that the Bjorken sum rule is confirmed within an experimental uncertainty of 17%. The quark spin contribution to the nucleon spin is small, and the strange quark spin content is different from zero. 1 Now at CERN, 1211 Geneva 23, Switzerland. 2 Now at University of Montreal, PQ, H3C 3J7, Montreal, Canada. 3 Now at Max Planck Institute, Heidelberg, Germany. 4 Permanent address: Bogazi~i University, Bebek, lstanbul, Turkey. s Permanent address: Miyazaki University, 88921 Miyazaki-Shi, Japan. 6 Permanent address: KEK, 305 Ibaraki-Ken, Japan. 7 Permanent address: University of Honduras, Physics Department, Tegucigalpa, Honduras. s Permanent address: University of Buenos Aires, Physics Department, 1428 Buenos Aires, Argentina. 9 Now at SSC Laboratory, Dallas, 75237 TX, USA. l0 Now at ESRF, 38043 Grenoble, France. 11 Now at Philips Kommunikations-lndustrie AG, NiJrnberg, Germany. 12 Now at University of Virginia, Dept. of Physics, Charlottesville, 22901 VA, USA. 13 Supported by Bundesministerium t'fir Forschung und Technologie. 14 Supported by the Department of Energy. 15 Supported by the National Science Foundation. 16 Supported by Ishida Foundation, Mitsubishi Foundation and Monbusho International Science Research Program. 17 Supported by the National Science Foundation of the Netherlands. 18 Supported by Comision Interministerial de Ciencia y Tecnologia. 19 Supported by the US-Israel Binational Science Foundation, Jerusalem, Israel. 20 Supported by KBN. Recently, experimental results on the spin dependent structure functions of the deuteron gd (X) [ 1 ] and of the neutron g~(x ) [2] have been reported by the Spin Muon Collaboration (SMC) and by the E 142 Collaboration. Different conclusions have been reached from the analysis of these results. The conclusions from the deuteron experiment at CERN [ 1 ] agree with those of the earlier proton experiments E80 and E130 at SLAC [3] and EMC at CERN [4]. The first moment ~d = f0 l gd dx is smaller than the prediction of the Ellis-Jaffe sum rule [5]. The fraction of the nucleon spin carried by quark spins AS is small and the fraction of the nucleon spin carried by strange quarks A~ is appreciable and negative. On the other hand, the results from the E142 Collaboration at SLAC [2] agree with the prediction of the EllisJaffe sum rule, AS is large and As is consistent with zero (see table 1). Both the SMC and the E142 Collaboration have tested the fundamental Bjorken sum rule [6], combining their results with those from the proton experiments. The results from the SMC analysis [l ] confirm the validity of the Bjorken sum rule, while E142 [2] reports a two standard deviation difference. These results were reanalysed in refs. [7,8], where the Q2 dependence of the sum rules, target mass and higher-order corrections were taken into account. In the present paper, we investigate the Q2 dependence of the data and focus our analysis on the consistency