Search for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>η</mml:mi><mml:mo>′</mml:mo></mml:msup></mml:math> Bound Nuclei in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:mmultiscripts><mml:mo stretchy="false">(</mml:mo><mml:mi>γ</mml:mi><mml:mo>,</mml:mo><mml:mi>p</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:math> Reaction with Simultaneous Detection of Decay Products
N. Tomida, N. Muramatsu, M. Niiyama, J. K. Ahn, W. C. Chang, J. Y. Chen, M. L. Chu, S. Daté, T. Gogami, H. Goto, H Hamano, Toshikazu Hashimoto, Q. He, K. Hicks, T. Hiraiwa, Y. Honda, T. Hotta, H. Ikuno, Yoshiyuki Inoue, T. Ishikawa, I. Jaeglé, J. M. Jo, Y. Kasamatsu, H. Katsuragawa, S. Kido, Y. Kon, Tomoyuki Maruyama, S. Masumoto, Yoko Matsumura, M. Miyabe, K. Mizutani, Hideko Nagahiro, T. Nakamura, T. Nakano, T. Nam, T. N. T. Ngan, Y. Nozawa, Yoji Ohashi, H. Ohnìshì, T. Ohta, K. Ozawa, C. Rangacharyulu, S. Y. Ryu, Y. Sada, M. Sasagawa, T. Shibukawa, H. Shimizu, R. Shirai, Kazunori Shiraishi, E. A. Strokovsky, Y. Sugaya, M. Sumihama, S. Suzuki, S. Tanaka, A. O. Tokiyasu, Y. Tsuchikawa, Takashi Ueda, H. Yamazaki, Ryuichi Yamazaki, Y. Yanai, T. Yorita, C. Yoshida, M. Yosoi
Abstract
We measured missing mass spectrum of the $^{12}\mathrm{C}(\ensuremath{\gamma},p)$ reaction for the first time in coincidence with potential decay products from ${\ensuremath{\eta}}^{\ensuremath{'}}$ bound nuclei. We tagged an ($\ensuremath{\eta}+p$) pair associated with the ${\ensuremath{\eta}}^{\ensuremath{'}}N\ensuremath{\rightarrow}\ensuremath{\eta}N$ process in a nucleus. After applying kinematical selections to reduce backgrounds, no signal events were observed in the bound-state region. An upper limit of the signal cross section in the opening angle $\mathrm{cos}{\ensuremath{\theta}}_{\mathrm{lab}}^{\ensuremath{\eta}p}<\ensuremath{-}0.9$ was obtained to be $2.2\text{ }\text{ }\mathrm{nb}/\mathrm{sr}$ at the 90% confidence level. It is compared with theoretical cross sections, whose normalization ambiguity is suppressed by measuring a quasifree ${\ensuremath{\eta}}^{\ensuremath{'}}$ production rate. Our results indicate a small branching fraction of the ${\ensuremath{\eta}}^{\ensuremath{'}}N\ensuremath{\rightarrow}\ensuremath{\eta}N$ process and/or a shallow ${\ensuremath{\eta}}^{\ensuremath{'}}$-nucleus potential.