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

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. ; Bracko, M. ; Browder, T. E. ; Cervenkov, D. ; Chang, M. -C. ; Cheon, B. G. ; Chilikin, K. ; Cho, K. ; Chobanova, V. ; Choi, S. -K. ; Choi, Y. ; Cinabro, D. ; Dalseno, J. ; Dolezal, Z. ; Drasal, 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. ; Kodys, P. ; Korpar, S. ; Krizan, P. ; Krokovny, P. ; Kuzmin, A. ; Kwon, Y. -J. ; Lange, J. S. ; Lee, I. S. ; Lewis, P. ; Gioi, L. Li ; 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. ; Pesantez, L. ; Petric, 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. ; Staric, 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. ; Belle Collaboration

The dark photon A' and the dark Higgs boson h' 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(-) -> A'h', with h' -> A'A'. We investigate ten exclusive final states with A' -> e(+)e(-), mu(+)mu(-), or pi(+)pi(-) in the mass ranges 0.1 GeV/c(2) < m(A') < 3.5 GeV/c(2) and 0.2 GeV/c(2) < m(h') < 10.5 GeV/c(2). We also investigate three inclusive final states 2(e(+)e(-))X, 2(mu(+)mu(-))X, and (e(+)e(-))(mu(+)mu(-))X, where X denotes a dark photon candidate detected via missing mass, in the mass ranges 1.1 GeV/c(2) < m(A') < 3.5 GeV/c(2) and 2.2 GeV/c(2) < m(h') < 10.5 GeV/c(2). Using the entire 977 fb(-1) data set collected by Belle, we observe no significant signal. We obtain individual and combined 90% credibility level upper limits on the branching fraction times the Born cross section, B x sigma(Born), on the Born cross section sigma(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) x epsilon(2). These limits improve upon and cover wider mass ranges than previous experiments. The limits from the final states 3(pi(+)pi(-)) and 2(e(+)e(-))X are the first placed by any experiment. For alpha(D) equal to 1/137, m(h') < 8 GeV/c(2), and m(A') < 1 GeV/c(2), we exclude values of the mixing parameter epsilon above similar to 8 x 10(-4).


Published in:
Physical Review Letters, 114, 21, 211801
Year:
2015
Publisher:
College Pk, Amer Physical Soc
ISSN:
0031-9007
Laboratories:




 Record created 2015-09-28, last modified 2018-12-03


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