Search for the Dark Photon and the Dark Higgs Boson at Belle

Journal Article · Wed May 27 00:00:00 EDT 2015 · Physical Review Letters

DOI:https://doi.org/10.1103/PhysRevLett.114.211801· OSTI ID:1594432

Jaegle, I.; Adachi, I.; Aihara, H.; Al Said, S.; Asner, D. M.; Aushev, T.; Ayad, R.; Bakich, A. M.; Bansal, V.; Barrett, M.; Bhuyan, B.; Bozek, A.; Bračko, M.; Browder, T. E.; Červenkov, D.; Chang, M. -C.; Cheon, B. G.; Chilikin, K.; Cho, K.; Chobanova, V. ; Choi, S. -K.; Choi, Y.; Cinabro, D.; Dalseno, J.; Doležal, Z.; Drásal, Z.; Drutskoy, A.; Dutta, D.; Eidelman, S.; Epifanov, D.; Farhat, H.; Fast, J. E.; Ferber, T.; Frost, O.; Gaur, V.; Gabyshev, N.; Ganguly, S.; Garmash, A.; Getzkow, D.; Gillard, R.; Goh, Y. M.; Golob, B.; Grzymkowska, O.; Hayasaka, K.; Hayashii, H.; He, X. H.; Hedges, M.; Hou, W. -S.; Iijima, T.; Inami, K.; Ishikawa, A.; Iwasaki, Y.; Julius, T.; Kang, K. H.; Kato, E.; Kawasaki, T.; Kim, D. Y.; Kim, J. B.; Kim, J. H.; Kim, S. H.; Kinoshita, K.; Ko, B. R.; Kodyš, P.; Korpar, S.; Križan, P.; Krokovny, P.; Kuzmin, A.; Kwon, Y. -J.; Lange, J. S.; Lee, I. S.; Lewis, P.; Li Gioi, L.; Libby, J.; Liventsev, D.; Matvienko, D.; Miyata, H.; Mizuk, R.; Mohanty, G. B.; Moll, A.; Mussa, R.; Nakano, E.; Nakao, M.; Nisar, N. K.; Nishida, S.; Ogawa, S.; Pakhlov, P.; Pakhlova, G.; Park, H.; Pedlar, T. K.; Pesántez, L.; Petrič, M.; Piilonen, L. E.; Ritter, M.; Rostomyan, A.; Sakai, Y.; Sandilya, S.; Santelj, L.; Sanuki, T.; Sato, Y.; Savinov, V.; Schneider, O.; Schnell, G.; Schwanda, C.; Semmler, D.; Senyo, K.; Seon, O.; Seong, I.; Sevior, M. E.; Shebalin, V.; Shibata, T. -A.; Shiu, J. -G.; Shwartz, B.; Simon, F.; Sinha, R.; Sohn, Y. -S.; Starič, M.; Sumihama, M.; Sumisawa, K.; Tamponi, U.; Tatishvili, G.; Teramoto, Y.; Thorne, F.; Uchida, M.; Uehara, S.; Unno, Y.; Uno, S.; Vahsen, S. E.; Van Hulse, C.; Vanhoefer, P.; Varner, G.; Vinokurova, A.; Wagner, M. N.; Wang, C. H.; Wang, M. -Z.; Wang, P.; Wang, X. L.; Watanabe, M.; Watanabe, Y.; Williams, K. M.; Won, E.; Yamaoka, J.; Yashchenko, S.; Yook, Y.; Yusa, Y.; Zhilich, V.; Zhulanov, V.; Zupanc, A.

The dark photon $A^{\text{'}}$ and the dark Higgs boson $h^{\text{'}}$ are hypothetical constituents featured in a number of recently proposed dark sector models. Assuming prompt decays of both dark particles, we search for their production in the so-called Higgstrahlung channel $e^{+}{e}^{-}\to A^{\text{'}}{h}^{\text{'}}$, with $h^{\text{'}}\to A^{\text{'}}{A}^{\text{'}}$. We investigate ten exclusive final states with $A^{\text{'}}\to e^{+}{e}^{-}$, ${\mu }^{+}{\mu }^{-}$, or ${\pi }^{+}{\pi }^{-}$ in the mass ranges $0.1\mathrm{GeV}/c^2<m_{A^{\text{'}}}<3.5\mathrm{GeV}/c^2$ and $0.2\mathrm{GeV}/c^2<m_{h^{\text{'}}}<10.5\mathrm{GeV}/c^2$. We also investigate three inclusive final states $2\left(e^{+}{e}^{-}\right)X$, $2\left({\mu }^{+}{\mu }^{-}\right)X$, and $\left(e^{+}{e}^{-}\right)\left({\mu }^{+}{\mu }^{-}\right)X$, where $X$ denotes a dark photon candidate detected via missing mass, in the mass ranges $1.1\mathrm{GeV}/c^2<m_{A^{\text{'}}}<3.5\mathrm{GeV}/c^2$ and $2.2\mathrm{GeV}/c^2<m_{h^{\text{'}}}<10.5\mathrm{GeV}/c^2$. Using the entire $977{\mathrm{fb}}^{-1}$ data set collected by Belle, we determine no significant signal. Here, we obtain individual and combined 90% credibility level upper limits on the branching fraction times the Born cross section, $\mathcal{B}\times {\sigma }_{\text{Born}}$, on the Born cross section ${\sigma }_{\text{Born}}$, and on the dark photon coupling to the dark Higgs boson times the kinetic mixing between the standard model photon and the dark photon, ${\alpha }_D\times {\epsilon }^2$. These limits improve upon and cover wider mass ranges than previous experiments. The limits from the final states $3\left({\pi }^{+}{\pi }^{-}\right)$ and $2\left(e^{+}{e}^{-}\right)X$ are the first placed by any experiment. For ${\alpha }_D$ equal to $1/137$, $m_{h^{\text{'}}}<8\mathrm{GeV}/c^2$, and $m_{A^{\text{'}}}<1\mathrm{GeV}/c^2$, we exclude values of the mixing parameter $\epsilon$ above ~ 8×10^-4.

• Research Organization: Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Univ. of Hawaii, Honolulu, HI (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP)
• Contributing Organization: Belle Collaboration
• Grant/Contract Number: SC0009973
• OSTI ID: 1594432
• Alternate ID(s): OSTI ID: 1224597
• Journal Information: Physical Review Letters, Vol. 114, Issue 21; ISSN 0031-9007
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS