Observation of a new structure near 10.75 GeV in the energy dependence of the e+e−→ ϒ (nS)π+π− (n = 1, 2, 3) cross sections

Mizuk, R.; Bondar, A.; Adachi, I.; Aihara, H.; Asner, D. M.; Aulchenko, V.; Aushev, T.; Ayad, R.; Badhrees, I.; Bahinipati, S.; Bakich, A. M.; Behera, P.; Beleño, C.; Berger, M.; Bhardwaj, V.; Bilka, T.; Biswal, J.; Bozek, A.; Bračko, M.; Browder, T. E.; Campajola, M.; Cao, L.; Červenkov, D.; Chen, A.; Cheon, B. G.; Chilikin, K.; Cho, H. E.; Cho, K.; Choi, S.-K.; Choi, Y.; Cinabro, D.; Cunliffe, S.; Dash, N.; De Nardo, G.; Di Capua, F.; Di Carlo, S.; Doležal, Z.; Dong, T.V.; Eidelman, S.; Epifanov, D.; Fast, J. E.; Ferber, T.; Fulsom, B. G.; Gaur, V.; Garmash, A.; Giri, A.; Goldenzweig, P.; Golob, B.; Grzymkowska, O.; Hara, T.; Hartbrich, O.; Hayasaka, K.; Hayashii, H.; Hou, W.-S.; Iijima, T.; Inami, K.; Inguglia, G.; Ishikawa, A.; Itoh, R.; Iwasaki, M.; Iwasaki, Y.; Jacobs, W. W.; Jin, Y.; Joffe, D.; Joo, K. K.; Kang, K. H.; Karyan, G.; Kawasaki, T.; Kichimi, H.; Kim, D. Y.; Kim, H. J.; Kim, K. T.; Kim, S. H.; Kinoshita, K.; Kodyš, P.; Korpar, S.; Kotchetkov, D.; Križan, P.; Kroeger, R.; Krokovny, P.; Kuhr, T.; Kumar, R.; Kuzmin, A.; Lange, J. S.; Lee, J. Y.; Lee, S. C.; Li, L. K.; Gioi, L. Li; Libby, J.; Lieret, K.; Liventsev, D.; Luo, T.; MacNaughton, J.; MacQueen, C.; Masuda, M.; Matsuda, T.; Matvienko, D.; Merola, M.; Miyata, H.; Mohanty, G. B.; Mori, T.; Mussa, R.; Nakano, T.; Nakao, M.; Nath, K. J.; Natkaniec, Z.; Nayak, M.; Niiyama, M.; Nisar, N. K.; Nishida, S.; Nishimura, K.; Ogawa, S.; Olsen, S. L.; Ono, H.; Onuki, Y.; Oskin, P.; Ostrowicz, W.; Pakhlov, P.; Pakhlova, G.; Pal, B.; Pang, T.; Pardi, S.; Park, S.-H.; Paul, S.; Pedlar, T. K.; Pestotnik, R.; Piilonen, L. E.; Popov, V.; Prencipe, E.; Ritter, M.; Rostomyan, A.; Russo, G.; Sakai, Y.; Salehi, M.; Sandilya, S.; Sanuki, T.; Savinov, V.; Schneider, O.; Schnell, G.; Schueler, J.; Schwanda, C.; Seino, Y.; Senyo, K.; Seon, O.; Sevior, M. E.; Shebalin, V.; Shen, C. P.; Shiu, J.-G.; Shwartz, B.; Sokolov, A.; Solovieva, E.; Starič, M.; Strube, J. F.; Sumihama, M.; Sumiyoshi, T.; Sutcliffe, W.; Takizawa, M.; Tamponi, U.; Tanida, K.; Tenchini, F.; Trabelsi, K.; Uglov, T.; Unno, Y.; Uno, S.; Urquijo, P.; Usov, Y.; Vahsen, S. E.; Van Tonder, R.; Varner, G.; Vinokurova, A.; Wang, B.; Wang, C. H.; Wang, M.-Z.; Wang, P.; Won, E.; Yang, S. B.; Ye, H.; Yuan, C. Z.; Yusa, Y.; Zhang, Z. P.; Zhilich, V.; Zhukova, V.

doi:10.1007/JHEP10(2019)220

A bstract We present a search for the dark photon A ′ in the B 0 → A ′ A ′ decays, where A ′ subsequently decays to e + e − , μ + μ − , and π + π − . The search is performed by analyzing 772 × 10 6 $$ B\overline{B} $$ B B ¯ events collected by the Belle detector at the KEKB e + e − energy-asymmetric collider at the ϒ(4 S ) resonance. No signal is found in the dark photon mass range 0 . 01 GeV /c 2 ≤ m A ′ ≤ 2 . 62 GeV /c 2 , and we set upper limits of the branching fraction of B 0 → A ′ A ′ at the 90% confidence level. The products of branching fractions, $$ \mathrm{\mathcal{B}}\left({B}^0\to A^{\prime }A^{\prime}\right)\times \mathrm{\mathcal{B}}{\left(A\prime \to {e}^{+}{e}^{-}\right)}^2 $$ ℬ B 0 → A ′ A ′ × ℬ A ′ → e + e − 2 and $$ \mathrm{\mathcal{B}}\left({B}^0\to A^{\prime }A^{\prime}\right)\times \mathrm{\mathcal{B}}{\left(A\prime \to {\mu}^{+}{\mu}^{-}\right)}^2 $$ ℬ B 0 → A ′ A ′ × ℬ A ′ → μ + μ − 2 , have limits of the order of 10 − 8 depending on the A ′ mass. Furthermore, considering A ′ decay rate to each pair of charged particles, the upper limits of $$ \mathrm{\mathcal{B}}\left({B}^0\to A^{\prime }A^{\prime}\right) $$ ℬ B 0 → A ′ A ′ are of the order of 10 − 8 –10 − 5 . From the upper limits of $$ \mathrm{\mathcal{B}}\left({B}^0\to A^{\prime }A^{\prime}\right) $$ ℬ B 0 → A ′ A ′ , we obtain the Higgs portal coupling for each assumed dark photon and dark Higgs mass. The Higgs portal couplings are of the order of 10 − 2 –10 − 1 at $$ {m}_{h\prime}\simeq {m}_{B^0} $$ m h ′ ≃ m B 0 ± 40 MeV /c 2 and 10 − 1 –1 at $$ {m}_{h\prime}\simeq {m}_{B^0} $$ m h ′ ≃ m B 0 ± 3 GeV /c 2 .

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