Azimuthal asymmetries of back-to-back $\pi^\pm-(\pi^0,\eta,\pi^\pm)$ pairs in $e^+e^-$ annihilation

• Published in: Physical review. D 2019, Vol.100 (9)
• Main Authors: 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., Li, Y.B., Li Gioi, L., Libby, J., Lieret, K., Liventsev, D., Luo, T., Macqueen, C., Masuda, M., Matsuda, T., Merola, M., Miyabayashi, K., Mussa, R., Nakano, T., Nakao, M., Naruki, M., Nath, K.J., Natkaniec, Z., 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., Santelj, L., Sanuki, T., Savinov, V., Schneider, O., Schnell, G., Schueler, J., Schwanda, C., Seidl, R.
• Format: Article
• Language: English
• Subjects: High Energy Physics - Experiment; Physics
• ISSN: 2470-0010; 2470-0029
• 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 H1⊥ 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 H1⊥. 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.