Azimuthal asymmetries of back-to-back pairs in π±−(π0,η,π±) pairs in e+e− annihilation

Li, H.; Vossen, A.; Aihara, H.; Asner, D.  m.; Aulchenko, V.; Aushev, T.; Babu, V.; Badhrees, I.; Bakich, A.  m.; Bennett, J.; Bhardwaj, V.; Bilka, T.; Biswal, J.; Bobrov, A.; Bračko, M.; Campajola, M.; Cao, L.; Červenkov, D.; Chekelian, V.; Chen, A.; Cheon, B.  g.; Cho, H.  e.; Cho, K.; Choi, Y.; Choudhury, S.; Cinabro, D.; Cunliffe, S.; Di Capua, F.; Di Carlo, S.; Dong, T.  v.; Eidelman, S.; Ferber, T.; Fulsom, B.  g.; Gaur, V.; Garmash, A.; Giri, A.; Goldenzweig, P.; Hartbrich, O.; Hayasaka, K.; Hayashii, H.; Huang, K.; Inami, K.; Ishikawa, A.; Itoh, R.; Iwasaki, M.; Jacobs, W.  w.; Jang, E. -J.; Jia, S.; Jin, Y.; Kang, K.  h.; Karyan, G.; Kim, D.  y.; Kim, S.  h.; Kodyš, P.; Korpar, S.; Kotchetkov, D.; Križan, P.; Kroeger, R.; Krokovny, P.; Kwon, Y. -J.; Lee, S.  c.; Y.  b., Li; Li Gioi, L.; Libby, J.; Lieret, K.; Liventsev, D.; Luo, T.; Macqueen, C.; Masuda, M.; Matsuda, T.; Merola, M.; Miyabayashi, K.; Miyata, H.; Mizuk, R.; Mussa, R.; Nakano, T.; Nakao, M.; Naruki, M.; Nath, K.  j.; Natkaniec, Z.; Nishida, S.; Ono, H.; Ostrowicz, W.; Pakhlov, P.; Pakhlova, G.; Pal, B.; Pardi, S.; Patra, S.; Paul, S.; Pedlar, T.  k.; Pestotnik, R.; Piilonen, L.  e.; Popov, V.; Prencipe, E.; Prim, M.  t.; Russo, G.; Sahoo, D.; Sakai, Y.; Santelj, L.; Sanuki, T.; Savinov, V.; Schneider, O.; Schnell, G.; Schueler, J.; Schwanda, C.; Seidl, R.; Seino, Y.; Senyo, K.; Shiu, J. -G.; Simon, F.; Solovieva, E.; Starič, M.; Stottler, Z.  s.; Takizawa, M.; Tanida, K.; Tenchini, F.; Uchida, M.; Uglov, T.; Uno, S.; Van Tonder, R.; Varner, G.; Wang, B.; Wang, C.  h.; Wang, M. -Z.; Wang, P.; Watanabe, M.; Won, E.; Yang, S.  b.; Ye, H.; Zhang, Z.  p.; Zhilich, V.; Zhukova, V.; Zhulanov, V.

doi:10.1103/physrevd.100.092008

This work reports the first observation of azimuthal asymmetries around the thrust axis in e+e− annihilation of pairs of back-to-back charged pions in one hemisphere, and π0 and η mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The π0 and η asymmetries rise with the relative momentum z of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function H⊥1 and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the η final states will provide additional information on the flavor structure of H⊥1. This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4 fb−1 collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.