Flavour separation of helicity distributions from deep inelastic muon-deuteron scattering RID D-4627-2011

Alekseev, M; Alexakhin, Vy; Alexandrov, Y; Alexeev, Gd; Amoroso, A; Austregesilo, A; Badelek, B; Balestra, F; Ball, J; Barth, J; Baum, G; Bedfer, Y; Bernhard, J; Bertini, R; Bettinelli, M; Birsa, R; Bisplinghoff, J; Bordalo, P; Bradamante, F; Bravar, A; Bressan, A; Brona, G; Burtin, E; Bussa, Mp; Chapiro, A; Chiosso, M; Chung, Su; Cicuttin, A; Colantoni, M; Crespo, Ml; Dalla Torre, S; Dafni, T; Das, S; Dasgupta, Ss; Denisov, Oy; Dhara, L; Diaz, V; Dinkelbach, Am; Donskov, Sv; Doshita, N; Duic, V; Dunnweber, W; Efremov, A; El Alaoui, A; Eversheim, Pd; Eyrich, W; Faessler, M; Ferrero, A; Finger, M; Finger, M; Fischer, H; Franco, C; Friedrich, Jm; Garfagnini, R; Gautheron, F; Gavrichtchouk, Op; Gazda, R; Gerassimov, S; Geyer, R; Giorgi, M; Gobbo, B; Goertz, S; Grabmuller, S; Grajek, Oa; Grasso, A; Grube, B; Gushterski, R; Guskov, A; Haas, F; Hagemann, R; von Harrach, D; Hasegawa, T; Heckmann, J; Heinsius, Fh; Hermann, R; Herrmann, F; Hess, C; Hinterberger, F; Horikawa, N; Hoppner, C; D'Hose, N; Ilgner, C; Ishimoto, S; Ivanov, O; Ivanshin, Y; Iwata, T; Jahn, R; Jasinski, P; Jegou, G; Joosten, R; Kabuss, E; Kafer, W; Kang, D; Ketzer, B; Khaustov, Gv; Khokhlov, Ya; Kiefer, J; Kisselev, Y; Klein, F; Klimaszewski, K; Koblitz, S; Koivuniemi, Jh; Kolosov, Vn; Komissarov, Ev; Kondo, K; Konigsmann, K; Konopka, R; Konorov, I; Konstantinov, Vf; Korzenev, A; Kotzinian, Am; Kouznetsov, O; Kowalik, K; Kramer, M; Kral, A; Kroumchtein, Zv; Kuhn, R; Kunne, F; Kurek, K; Le Goff JM,; Lednev, Aa; Lehmann, A; Levorato, S; Lichtenstadt, J; Liska, T; Maggiora, A; Maggiora, M; Magnon, A; Mallot, Gk; Mann, A; Marchand, C; Marroncle, J; Martin, A; Marzec, J; Massmann, F; Matsuda, T; Maximov, An; Meyer, W; Michigami, T; Mikhailov, Yv; Moinester, Ma; Mutter, A; Nagaytsev, A; Nagel, T; Nassalski, J; Negrini, S; Nerling, F; Neubert, S; Neyret, D; Nikolaenko, Vi; Olshevsky, Ag; Ostrick, M; Padee, A; Panknin, R; Panzieri, Daniele; Parsamyan, B; Paul, S; Pawlukiewicz Kaminska, B; Perevalova, E; Pesaro, G; Peshekhonov, Dv; Piragino, G; Platchkov, S; Pochodzalla, J; Polak, J; Polyakov, Va; Pontecorvo, G; Pretz, J; Quintans, C; Rajotte, Jf; Ramos, S; Rapatsky, V; Reicherz, G; Reggiani, D; Richter, A; Robinet, F; Rocco, E; Rondio, E; Ryabchikov, Di; Samoylenko, Vd; Sandacz, A; Santos, H; Sapozhnikov, Mg; Sarkar, S; Savin, Ia; Sbrizzai, G; Schiavon, P; Schill, C; Schmitt, L; Schroder, W; Shevchenko, Oy; Siebert, Hw; Silva, L; Sinha, L; Sissakian, An; Slunecka, M; Smirnov, Gi; Sosio, S; Sozzi, F; Srnka, A; Stolarski, M; Sulc, M; Sulej, R; Takekawa, S; Tessaro, S; Tessarotto, F; Teufel, A; Tkatchev, Lg; Venugopal, G; Virius, M; Viassov, Nv; Vossen, A; Weitzel, Q; Wenzl, K; Windmolders, R; Wislicki, W; Wollny, H; Zaremba, K; Zavertyaev, M; Zemlyanichkina, E; Ziembicki, M; Zhao, J; Zhuravlev, N; Zvyagin, A.

doi:10.1016/j.physletb.2009.08.065

We present a LO evaluation of helicity densities of valence, Δuv+ΔdvΔuv+Δdv, non-strange sea, View the MathML sourceΔu¯+Δd¯, and strange quarks, Δs (assumed to be equal to View the MathML sourceΔs¯). They have been obtained from the inclusive asymmetry A1,dA1,d and the semi-inclusive asymmetries View the MathML sourceA1,dπ+, View the MathML sourceA1,dπ−, View the MathML sourceA1,dK+, View the MathML sourceA1,dK− measured in polarised deep inelastic muon–deuteron scattering. The full deuteron statistics of COMPASS (years 2002–2004 and 2006) has been used. The data cover the range Q2>1 2(GeV/c)Q2>1 (GeV/c)2 and 0.004<x<0.30.004<x<0.3. Both non-strange densities are found to be in a good agreement with previous measurements. The distribution of Δs(x)Δs(x) is compatible with zero in the whole measured range, in contrast to the shape of the strange quark helicity distribution obtained in most LO and NLO QCD fits. The sensitivity of the values of Δs(x)Δs(x) upon the choice of fragmentation functions used in the derivation is discussed.