新山　雅之
   所属   京都産業大学  理学部 物理科学科
   職種   教授
発行・発表の年月 2021/05
形態種別 その他
標題 The study of $γγ\toγψ(2S)$ at Belle
執筆形態 その他
著者・共著者 X. L. Wang,B. S. Gao,W. J. Zhu,I. Adachi,H. Aihara,S. Al Said,D. M. Asner,H. Atmacan,V. Aulchenko,T. Aushev,R. Ayad,V. Babu,S. Bahinipati,P. Behera,V. Bhardwaj,B. Bhuyan,T. Bilka,J. Biswal,A. Bobrov,G. Bonvicini,A. Bozek,M. Bračko,M. Campajola,D. Červenkov,M. -C. Chang,V. Chekelian,A. Chen,B. G. Cheon,K. Chilikin,H. E. Cho,K. Cho,S. -K. Choi,Y. Choi,S. Choudhury,D. Cinabro,S. Cunliffe,S. Das,G. De Nardo,R. Dhamija,F. Di Capua,Z. Doležal,T. V. Dong,S. Eidelman,T. Ferber,D. Ferlewicz,A. Frey,B. G.
概要 Using $980~\rm fb^{-1}$ of data on and around the $\Upsilon(nS)(n=1,2,3,4,5)$
resonances collected with the Belle detector at the KEKB asymmetric-energy
$e^+e^-$ collider, the two-photon process $\gamma\gamma\to \gamma\psi(2S)$ is
studied from the threshold to $4.2~{\rm GeV}$ for the first time. Two
structures are seen in the invariant mass distribution of $\gamma\psi(2S)$: one
at $M_{R_1} = 3922.4\pm 6.5 \pm 2.0~{\rm MeV}/c^2$ with a width of
$\Gamma_{R_1} = 22\pm 17\pm 4~{\rm MeV}$, and another at $M_{R_2} = 4014.3\pm
4.0 \pm 1.5~{\rm MeV}/c^2$ with a width of $\Gamma_{R_2} = 4\pm 11 \pm 6~{\rm
MeV}$; the signals are parametrized with the incoherent sum of two Breit-Wigner
functions. The first structure is consistent with the $X(3915)$ or the
$\chi_{c2}(3930)$, and the local statistical significance is determined to be
$3.1\sigma$ with the systematic uncertainties included. The second matches none
of the known charmonium or charmoniumlike states, and its global significance
is determined to be $2.8\sigma$ including the look-elsewhere effect. The
production rates are $\Gamma_{\gamma\gamma}{\cal B}(R_1\to\gamma\psi(2S)) =
9.8\pm 3.6\pm 1.2~{\rm eV}$ assuming $(J^{PC}, |\lambda|) =(0^{++}, 0)$ or
$2.0\pm 0.7\pm 0.2~{\rm eV}$ with $(2^{++}, 2)$ for the first structure and
$\Gamma_{\gamma\gamma}{\cal B}(R_2\to\gamma\psi(2S)) = 6.2\pm 2.2\pm 0.8~{\rm
eV}$ with $(0^{++}, 0)$ or $1.2\pm 0.4\pm 0.2~{\rm eV}$ with $(2^{++}, 2)$ for
the second one. Here, the first errors are statistical and the second
systematic, and $\lambda$ is the helicity.
DOI 10.1103/PhysRevD.105.112011
PermalinkURL http://arxiv.org/abs/2105.06605v3
researchmap用URL http://arxiv.org/pdf/2105.06605v3