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arXiv · 2012.02538

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

S. -H. Park·Y. -J. Kwon·I. Adachi·H. Aihara·S. Al Said·D. M. Asner·H. Atmacan·T. Aushev·R. Ayad·V. Babu·P. Behera·J. Bennett·M. Bessner·V. Bhardwaj·B. Bhuyan·T. Bilka·J. Biswal·G. Bonvicini·A. Bozek·M. Bračko·T. E. Browder·M. Campajola·L. Cao·D. Červenkov·M. -C. Chang·P. Chang·A. Chen·B. G. Cheon·K. Chilikin·H. E. Cho·K. Cho·S. -J. Cho·S. -K. Choi·Y. Choi·S. Choudhury·D. Cinabro·S. Cunliffe·S. Das·N. Dash·G. De Nardo·F. Di Capua·J. Dingfelder·Z. Doležal·T. V. Dong·S. Eidelman·D. Epifanov·D. Ferlewicz·B. G. Fulsom·R. Garg·V. Gaur·A. Garmash·A. Giri·P. Goldenzweig·Y. Guan·K. Gudkova·C. Hadjivasiliou·T. Hara·O. Hartbrich·K. Hayasaka·H. Hayashii·M. T. Hedges·M. Hernandez Villanueva·W. -S. Hou·C. -L. Hsu·K. Huang·T. Iijima·K. Inami·G. Inguglia·A. Ishikawa·R. Itoh·M. Iwasaki·Y. Iwasaki·W. W. Jacobs·I. Jaegle·E. -J. Jang·H. B. Jeon·S. Jia·Y. Jin·C. W. Joo·K. K. Joo·K. H. Kang·G. Karyan·T. Kawasaki·C. Kiesling·D. Y. Kim·K. -H. Kim·S. H. Kim·Y. -K. Kim·K. Kinoshita·P. Kodyš·T. Konno·S. Korpar·D. Kotchetkov·P. Križan·R. Kroeger·P. Krokovny·T. Kuhr·M. Kumar·K. Kumara·K. Lalwani
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Abstract

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 $m_{h'} \simeq m_{B^0} \pm 3~\mathrm{GeV}/c^2$.

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S. -H. Park, Y. -J. Kwon, I. Adachi, H. Aihara, S. Al Said, D. M. Asner, H. Atmacan, T. Aushev, R. Ayad, V. Babu, P. Behera, J. Bennett, M. Bessner, V. Bhardwaj, B. Bhuyan, T. Bilka, J. Biswal, G. Bonvicini, A. Bozek, M. Bračko, T. E. Browder, M. Campajola, L. Cao, D. Červenkov, M. -C. Chang, P. Chang, A. Chen, B. G. Cheon, K. Chilikin, H. E. Cho, K. Cho, S. -J. Cho, S. -K. Choi, Y. Choi, S. Choudhury, D. Cinabro, S. Cunliffe, S. Das, N. Dash, G. De Nardo, F. Di Capua, J. Dingfelder, Z. Doležal, T. V. Dong, S. Eidelman, D. Epifanov, D. Ferlewicz, B. G. Fulsom, R. Garg, V. Gaur, A. Garmash, A. Giri, P. Goldenzweig, Y. Guan, K. Gudkova, C. Hadjivasiliou, T. Hara, O. Hartbrich, K. Hayasaka, H. Hayashii, M. T. Hedges, M. Hernandez Villanueva, W. -S. Hou, C. -L. Hsu, K. Huang, T. Iijima, K. Inami, G. Inguglia, A. Ishikawa, R. Itoh, M. Iwasaki, Y. Iwasaki, W. W. Jacobs, I. Jaegle, E. -J. Jang, H. B. Jeon, S. Jia, Y. Jin, C. W. Joo, K. K. Joo, K. H. Kang, G. Karyan, T. Kawasaki, C. Kiesling, D. Y. Kim, K. -H. Kim, S. H. Kim, Y. -K. Kim, K. Kinoshita, P. Kodyš, T. Konno, S. Korpar, D. Kotchetkov, P. Križan, R. Kroeger, P. Krokovny, T. Kuhr, M. Kumar, K. Kumara, K. Lalwani. 2020-12-04. 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. https://doi.org/10.1007/jhep04(2021)191

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