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論文

Observation of $$Xi_{c}(2930)^0$$ and updated measurement of $$B^{-} to K^{-} Lambda_{c}^{+} bar{Lambda}_{c}^{-}$$ at Belle

Li, Y. B.*; 谷田 聖; Belle Collaboration*; 他178名*

European Physical Journal C, 78(3), p.252_1 - 252_8, 2018/03

https://doi.org/10.1140/epjc/s10052-018-5720-5
 被引用回数：32 パーセンタイル：83.35(Physics, Particles & Fields)

We report the first observation of the $$Xi_{c}(2930)^0$$ charmed-strange baryon with a significance greater than 5$$sigma$$. The $$Xi_{c}(2930)^0$$ is found in its decay to $$K^- Lambda_{c}^+$$ in $$B^{-} to K^{-} Lambda_{c}^{+} bar{Lambda}_{c}^{-}$$ decays. The measured mass and width are $$[2928.9 pm 3.0(rm stat.)^{+0.9}_{-12.0}(rm syst.)]$$ MeV/$$c^{2}$$ and $$[19.5 pm 8.4(rm stat.) ^{+5.9}_{-7.9}(rm syst.)]$$ MeV, respectively, and the product branching fraction is $${cal B}(B^{-} to Xi_{c}(2930)^0 bar{Lambda}_{c}^{-})$$$$ {cal B}(Xi_{c}(2930)^0 to K^- Lambda_{c}^{+})$$=$$[1.73 pm 0.45(rm stat.) pm 0.21(rm syst.)] times 10^{-4}$$. We also measure $${cal B}(B^{-} to K^{-} Lambda_{c}^{+} bar{Lambda}_{c}^{-}) = [4.80 pm 0.43(rm stat.) pm 0.60(rm syst.)] times 10^{-4}$$ with improved precision, and search for the charmonium-like state $$Y(4660)$$ and its spin partner, $$Y_{eta}$$, in the $$Lambda_{c}^{+}bar{Lambda}_{c}^{-}$$ invariant mass spectrum. No clear signals of the $$Y(4660)$$ nor its spin partner are observed and the 90% credibility level (C.L.) upper limits on their production rates are determined. These measurements are obtained from a sample of $$(772pm11)times 10^{6} Bbar{B}$$ pairs collected at the $$Upsilon(4S)$$ resonance by the Belle detector at the KEKB asymmetric energy electron-positron collider.

論文

Study of $$pi^0$$ pair production in single-tag two-photon collisions

増田 正孝*; 谷田 聖; Belle Collaboration*; 他178名*

Physical Review D, 93(3), p.032003_1 - 032003_34, 2016/02

AA2015-0858.pdf:2.61MB

https://doi.org/10.1103/PhysRevD.93.032003
 被引用回数：47 パーセンタイル：88.46(Astronomy & Astrophysics)

We report a measurement of the differential cross section of $$pi^0$$ pair production in single-tag two-photon collisions, $$gamma^*gamma to pi^0pi^0$$, in $$e^+e^-$$ scattering. The cross section is measured for $$Q^2$$ up to 30 GeV$$^2$$, where $$Q^2$$ is the negative of the invariant mass squared of the tagged photon, in the kinematic range 0.5 GeV $$< W <$$ 2.1 GeV and $$|costheta^*| < 1.0$$ for the total energy and pion scattering angle, respectively, in the $$gamma^*gamma$$ center-of-mass system. The results are based on a data sample of 759 fb$$^{-1}$$ collected with the Belle detector at the KEKB asymmetric-energy $$e^+e^-$$ collider. The transition form factor of the $$f_0(980)$$ and that of the $$f_2(1270)$$ with the helicity-0, -1, and -2 components separately are measured for the first time and are compared with theoretical calculations.

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