Flavour separation of helicity distributions from deep inelastic muon–deuteron scattering

• Published in: Physics letters. B Vol. 680; no. 3; pp. 217 - 224
• Main Authors: Alexakhin, V.Yu, Alexandrov, Yu, Amoroso, A., Austregesilo, A., Balestra, F., Barth, J., Bernhard, J., Bisplinghoff, J., Bradamante, F., Chapiro, A., Chiosso, M., Cicuttin, A., Das, S., Dhara, L., Efremov, A., Eyrich, W., Finger, M., Fischer, H., Gautheron, F., Gavrichtchouk, O.P., Giorgi, M., Gobbo, B., Goertz, S., Grajek, O.A., Guskov, A., Hasegawa, T., Heckmann, J., Hermann, R., Herrmann, F., Heß, C., Horikawa, N., Höppner, Ch, Ilgner, C., Ivanshin, Yu, Iwata, T., Jahn, R., Jasinski, P., Joosten, R., Kabuß, E., Käfer, W., Kang, D., Kisselev, Yu, Koblitz, S., Koivuniemi, J.H., Komissarov, E.V., Kondo, K., Konopka, R., Konstantinov, V.F., Kotzinian, A.M., Kowalik, K., Krämer, M., Kroumchtein, Z.V., Kunne, F., Le Goff, J.M., Lednev, A.A., Levorato, S., Liska, T., Magnon, A., Mann, A., Marzec, J., Massmann, F., Moinester, M.A., Nagaytsev, A., Nagel, T., Negrini, S., Nerling, F., Panknin, R., Parsamyan, B., Paul, S., Pawlukiewicz-Kaminska, B., Perevalova, E., Pesaro, G., Peshekhonov, D.V., Platchkov, S., Polyakov, V.A., Pontecorvo, G., Rajotte, J.-F., Rapatsky, V., Reggiani, D., Richter, A., Robinet, F., Sandacz, A., Sapozhnikov, M.G., Sarkar, S., Sbrizzai, G., Schiavon, P., Shevchenko, O.Yu, Sissakian, A.N., Sozzi, F., Stolarski, M., Tessaro, S., Tessarotto, F., Teufel, A., Venugopal, G., Virius, M., Windmolders, R., Zaremba, K., Zavertyaev, M., Ziembicki, M., Zhuravlev, N.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 28-09-2009; Elsevier
• Subjects: Charged kaon asymmetry; COMPASS; Double-spin asymmetry; Exact sciences and technology; Flavour separation analysis; Helicity density; Nuclear physics; Parton distribution function; Physics; Polarised DIS and SIDIS reactions; The physics of elementary particles and fields; COMPASS; Flavour separation analysis; 13.60.Le; Parton distribution function; Helicity density; 13.60.Hb; 13.88.+e; Double-spin asymmetry; Polarised DIS and SIDIS reactions; Charged kaon asymmetry; Muon-deuteron scattering; Deuterons; Strange particles; Asymmetry; Inelastic scattering; Flavor; Helicity; Quantum chromodynamics; Fragmentation
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/j.physletb.2009.08.065

We present a LO evaluation of helicity densities of valence, Δuv+Δdv, non-strange sea, Δu¯+Δd¯, and strange quarks, Δs (assumed to be equal to Δs¯). They have been obtained from the inclusive asymmetry A1,d and the semi-inclusive asymmetries A1,dπ+, A1,dπ−, A1,dK+, A1,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 (GeV/c)2 and 0.004<x<0.3. Both non-strange densities are found to be in a good agreement with previous measurements. The distribution of 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) upon the choice of fragmentation functions used in the derivation is discussed.