@misc{oai:ir.soken.ac.jp:00000698,
author = {中澤, 秀介 and ナカザワ, ヒデユキ and NAKAZAWA, Hideyuki},
month = {2016-02-17},
note = {We have measured π+π- and K+K- production in two-photon collisions using 87.7fb-1 of data collected with the Belle detector at the asymmetric energy e+e-- collidor KEKB. The cross sections are measured to high precision in the two-photon center-of-mass energy (W) range of 2.4 GeV < W < 4.1 GeV and angular region of |cosθ*| < 0.6. The cross section ratio σ(γγ → K+K-) /σ(γγ → π+π-) is measured to be 0.89 ± 0.04 ± 0.15 in the range of 3.0 GeV < W < 4.1 GeV, where the ratio is energy independent. We observe a sin-4 θ* behavior of the cross section in the same W range. Production of χc0 and χc2 mesons is observed in both γγ → π+π- and γγ → K+K- modes. The products of the two-photon decay width and the branching ratio are measured to be
Γγγ(χc0)Br(χc0 → π+π-) = 15.1 ± 2.1 ± 2.3 eV
Γγγ(χc0)Br(χc0 → K+K-) = 14.3 ± 1.6 ± 2.3 eV
Γγγ(χc2)Br(χc2 → π+π-) = 0.76 ± 0.14 ± 0.11 eV
Γγγ(χc2)Br(χc2 → K+K-) = 0.44 ± 0.11 ± 0.07 eV
which result in the combined two-photon decay width
Γγγ(χc0) = 2.62 ± 0.23 (stat.) ± 0.31 (syst.) ± 0.24 (B) keV
Γγγ(χc2) = 0.44 ± 0.07 (stat.) ± 0.05 (syst.) ± 0.05 (B) keV., 総研大甲第852号},
title = {Measurement of the processes γγ→π+π- and γγ→K+K- at enegies of 2.4-4.1GeV},
year = {}
}