Search for the dark photon in $B^0 \to A^{\prime} A^{\prime}$, $A^{\prime} \to e^+ e^-$, $\mu^+ \mu^-$, and $\pi^+ \pi^-$ decays at Belle
Creators: name: Park, S.-H.
name: Kwon, Y.-J.
name: Adachi, I.
name: Aihara, H.
name: Al Said, S.
name: Asner, D. M.
name: Atmacan, H.
name: Aushev, T.
name: Ayad, R.
name: Babu, Varghese
name: Behera, P.
name: Bennett, J.
name: Bessner, M.
name: Bhardwaj, V.
name: Bhuyan, B.
name: Bilka, T.
name: Biswal, J.
name: Bonvicini, G.
name: Bozek, A.
name: Bračko, M.
name: Browder, T. E.
name: Campajola, M.
name: Cao, L.
name: Červenkov, D.
name: Chang, M.-C.
name: Chang, P.
name: Chen, A.
name: Cheon, B. G.
name: Chilikin, K.
name: Cho, H. E.
name: Cho, K.
name: Cho, S.-J.
name: Choi, S.-K.
name: Choi, Y.
name: Choudhury, S.
name: Cinabro, D.
name: Cunliffe, S.
name: Das, S.
name: Dash, N.
name: De Nardo, G.
name: Di Capua, F.
name: Dingfelder, J.
name: Doležal, Z.
name: Dong, T. V.
name: Eidelman, S.
name: Epifanov, D.
name: Ferlewicz, D.
name: Fulsom, B. G.
name: Garg, R.
name: Gaur, V.
name: Garmash, A.
name: Giri, A.
name: Goldenzweig, P.
name: Guan, Y.
name: Gudkova, K.
name: Hadjivasiliou, C.
name: Hara, T.
name: Hartbrich, O.
name: Hayasaka, K.
name: Hayashii, H.
name: Hedges, M. T.
name: Hernandez Villanueva, M.
name: Hou, W.-S.
name: Hsu, C.-L.
name: Huang, K.
name: Iijima, T.
name: Inami, K.
name: Inguglia, G.
name: Ishikawa, A.
name: Itoh, R.
name: Iwasaki, M.
name: Iwasaki, Y.
name: Jacobs, W. W.
name: Jaegle, I.
name: Jang, E.-J.
name: Jeon, H. B.
name: Jia, S.
name: Jin, Y.
name: Joo, C. W.
name: Joo, K. K.
name: Kang, K. H.
name: Karyan, G.
name: Kawasaki, T.
name: Kiesling, C.
name: Kim, D. Y.
name: Kim, K.-H.
name: Kim, S. H.
name: Kim, Y.-K.
name: Kinoshita, K.
name: Kodyš, P.
name: Konno, T.
name: Korpar, S.
name: Kotchetkov, D.
name: Križan, P.
name: Kroeger, R.
name: Krokovny, P.
name: Kuhr, T.
name: Kumar, M.
name: Kumara, K.
name: Lalwani, K.
name: Lee, I. S.
name: Lee, S. C.
name: Li, C. H.
name: Li, J.
name: Li, L. K.
name: Li, Y. B.
name: Li Gioi, L.
name: Libby, J.
name: Lieret, K.
name: Liptak, Z.
name: Liventsev, D.
name: Luo, T.
name: MacNaughton, J.
name: MacQueen, C.
name: Masuda, M.
name: Matsuda, T.
name: Matvienko, D.
name: Merola, M.
name: Metzner, F.
name: Miyabayashi, K.
name: Mizuk, R.
name: Mohanty, G. B.
name: Mohanty, S.
name: Mori, T.
name: Moser, H.-G.
name: Mrvar, M.
name: Mussa, R.
name: Nakao, M.
name: Natkaniec, Z.
name: Natochii, A.
name: Nayak, L.
name: Nayak, M.
name: Niiyama, M.
name: Nisar, N. K.
name: Nishida, S.
name: Ogawa, S.
name: Ono, H.
name: Onuki, Y.
name: Oskin, P.
name: Pakhlov, P.
name: Pakhlova, G.
name: Pardi, S.
name: Park, C. W.
name: Park, H.
name: Patra, S.
name: Paul, S.
name: Pedlar, T. K.
name: Pestotnik, R.
name: Piilonen, L. E.
name: Podobnik, T.
name: Popov, V.
name: Prencipe, E.
name: Prim, M. T.
name: Ritter, M.
name: Röhrken, M.
name: Rostomyan, A.
name: Rout, N.
name: Russo, G.
name: Sakai, Y.
name: Sandilya, S.
name: Sangal, A.
name: Santelj, L.
name: Sanuki, T.
name: Savinov, V.
name: Schnell, G.
name: Schueler, J.
name: Schwanda, C.
name: Seino, Y.
name: Senyo, K.
name: Sevior, M. E.
name: Shapkin, M.
name: Sharma, C.
name: Shen, C. P.
name: Shiu, J.-G.
name: Sokolov, A.
name: Solovieva, E.
name: Stanič, S.
name: Starič, M.
name: Stottler, Z. S.
name: Strube, J. F.
name: Sumihama, M.
name: Sumisawa, K.
name: Sumiyoshi, T.
name: Sutcliffe, W.
name: Takizawa, M.
name: Tanida, K.
name: Tenchini, Francesco
name: Uchida, M.
name: Uglov, T.
name: Unno, Y.
name: Uno, S.
name: Urquijo, P.
name: Vahsen, S. E.
name: Van Tonder, R.
name: Varner, G.
name: Varvell, K. E.
name: Vinokurova, A.
name: Vorobyev, V.
name: Waheed, E.
name: Wang, C. H.
name: Wang, E.
name: Wang, M.-Z.
name: Wang, P.
name: Watanabe, M.
name: Watanuki, S.
name: Wehle, S.
name: Won, E.
name: Xu, X.
name: Yabsley, B. D.
name: Yan, W.
name: Yang, S. B.
name: Ye, H.
name: Yelton, J.
name: Yin, J. H.
name: Yusa, Y.
name: Zhang, Z. P.
name: Zhilich, V.
name: Zhukova, V.
name: Zhulanov, V.
Publisher: name: Deutsches Elektronen-Synchrotron, DESY, Hamburg
Year: 2020

description: We present a search for the dark photon $A^{\prime}$ in the $B^0 \to A^{\prime} A^{\prime}$ decays, where $A^{\prime}$ subsequently decays to $e^+ e^-$, $\mu^+ \mu^-$, and $\pi^+ \pi^-$. The search is performed by analyzing $772 \times 10^6$ $B\overline{B}$ events collected by the Belle detector at the KEKB $e^+ e^-$ energy-asymmetric collider at the $\Upsilon (4S)$ resonance. No signal is found in the dark photon mass range $0.01~\mathrm{GeV}/c^2 \le m_{A^{\prime}} \le 2.62~\mathrm{GeV}/c^2$, and we set upper limits of the branching fraction of $B^0 \to A^{\prime} A^{\prime}$ at the 90% confidence level. The products of branching fractions, $\mathcal{B}(B^0 \to A^{\prime} A^{\prime}) \times \mathcal{B}(A^{\prime} \to e^+ e^-)^2$ and $\mathcal{B}(B^0 \to A^{\prime} A^{\prime}) \times \mathcal{B}(A^{\prime} \to \mu^+ \mu^-)^2$, have limits of the order of $10^{-8}$ depending on the $A^{\prime}$ mass. Furthermore, considering $A^{\prime}$ decay rate to each pair of charged particles, the upper limits of $\mathcal{B}(B^0 \to A^{\prime} A^{\prime})$ are of the order of $10^{-8}$-$10^{-5}$. From the upper limits of $\mathcal{B}(B^0 \to A^{\prime} A^{\prime})$, 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 $m_{h'} \simeq m_{B^0} \pm 40~\mathrm{MeV}/c^2$ and $10^{-1}$-$1$ at $m_{h'} \simeq m_{B^0} \pm 3~\mathrm{GeV}/c^2$.