Evidence for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>X</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>3872</mml:mn><mml:mo stretchy="false">)</mml:mo><mml:mo stretchy="false">→</mml:mo><mml:mi>J</mml:mi><mml:mo stretchy="false">/</mml:mo><mml:mi>ψ</mml:mi><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> Produced in Single-Tag Two-Photon Interactions
Y. Teramoto, S. Uehara, M. Masuda, I. Adachi, H. Aihara, S. Al Said, D. M. Asner, H. Atmacan, T. Aushev, R. Ayad, V. Babu, P. K. Behera, C. Beleño, J. V. Bennett, V. Bhardwaj, B. Bhuyan, T. Bilka, J. P. Biswal, G. Bonvicini, A. Bożek, M. Bračko, T. E. Browder, M. Campajola, D. Červenkov, M.-C. Chang, P. Chang, V. Chekelian, K. F. Chen, B. G. Cheon, K. Chilikin, K. Cho, S.-J. Cho, S.-K. Choi, Y. Choi, S. Choudhury, D. Cinabro, S. Cunliffe, G. De Nardo, F. Di Capua, Z. Doležal, T. V. Dong, S. Eidelman, T. Ferber, B. G. Fulsom, R. B. Garg, V. Gaur, N. Gabyshev, A. Garmash, A. Giri, P. Goldenzweig, D. Greenwald, C. Hadjivasiliou, T. Hara, O. Hartbrich, K. Hayasaka, H. Hayashii, M. T. Hedges, M. Hernández Villanueva, W.-S. Hou, C.-L. Hsu, T. Iijima, K. Inami, G. Inguglia, A. Ishikawa, R. Itoh, M. Iwasaki, M. Iwasaki, W. W. Jacobs, E.-J. Jang, S. Jia, Y. Jin, C. Joo, K. K. Joo, J. Kahn, A. B. Kaliyar, K. H. Kang, G. Karyan, Yuji Katō, T. Kawasaki, H. Kichimi, C. Kiesling, B. H. Kim, D. Y. Kim, S. H. Kim, Kee Hoon Kim, T.D. Kimmel, K. Kinoshita, P. Kodyš, S. Korpar, D. Kotchetkov, P. Križan, R. Kroeger, P. Krokovny, T. Kuhr, R. Kulasiri, R. Kumar, K. Kumara, A. Kuzmin, Y.-J. Kwon, K. Lalwani
Abstract
We report the first evidence for $X(3872)$ production in two-photon interactions by tagging either the electron or the positron in the final state, exploring the highly virtual photon region. The search is performed in ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, using $825\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected by the Belle detector operated at the KEKB ${e}^{+}{e}^{\ensuremath{-}}$ collider. We observe three $X(3872)$ candidates, where the expected background is $0.11\ifmmode\pm\else\textpm\fi{}0.10$ events, with a significance of $3.2\ensuremath{\sigma}$. We obtain an estimated value for ${\stackrel{\texttildelow{}}{\mathrm{\ensuremath{\Gamma}}}}_{\ensuremath{\gamma}\ensuremath{\gamma}}\mathcal{B}\mathbf{(}X(3872)\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\mathbf{)}$ assuming the ${Q}^{2}$ dependence predicted by a $c\overline{c}$ meson model, where $\ensuremath{-}{Q}^{2}$ is the invariant mass squared of the virtual photon. No $X(3915)\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ candidates are found.