東京・上宮会所蔵聖徳太子孝養像考

　東京都荒川区の社会福祉法人上宮会所蔵聖徳太子像は、像内銘により、文永七年（一二七〇）に仏師尭慶が製作したことの知られる鎌倉時代後期の規準作品である。本稿では、二〇一三年五月に大学院思想文化専攻開講科目「美術史学演習Ⅲ」における演習の一環で実施した調査の概要を、「伝来」「像の概要」「銘記および納入品」の三章に分けて報告し、さらに日本彫刻史上の意義や周辺の問題についても、「聖徳太子造像における位置」「形式と表現」「仏師尭慶について」の三章に分けて論述する。この像は、聖徳太子像の典型的形式のひとつである孝養太子像の初期作例として貴重である。銘記によれば不退寺（現在も奈良市に所在する不退寺にあたる可能性がつよい）の像として造られたもので、さらに十六歳の肖像であると明記し、その形式の原型となった像の存在が暗示されることも注目される。また、形式や表現の点で奈良・元興寺の善春作聖徳太子像と共通する点が多く、作者尭慶はその他の事績をふくめても、鎌倉中・後期の奈良で活躍した善派仏師と関係が深いこと、などが明らかになった。末尾には、近代以降のこの像の伝来に関する文献を関連史料として付載した。　 The statue of Shotoku Taishi owned by the Jyogu Hospital Social Welfare Group (Jyogu Kai), Arakawa-ku, Tokyo is a standard work in the late Kamakura Period, known to be created by Busshi (sculptor of Buddhist statues) Gyokei in 1270 from the inscription in the statue. This paper reports an outline of an investigation conducted as a part of a seminar in “Art History Seminar III”, a course offered by the Department of Cultural History, Graduate School in May, 2013, in three chapters; “History”, “Outline of the Statue”, and “Inscription and Items inside the Statue” and discusses its meaning in Japanese sculpture history and peripheral issues in three chapters; “Position in Creation of Shotoku Taishi Statues”, “Style and Expression”, and “Busshi Gyokei”. This statue is valuable as an example of the early stage of statues of Kyoyo Taishi (considered to be a style of praying, being concerned about the condition of his father), which is one of typical styles of statues of Shotoku Taishi. According to the inscription, this statue was made for Futai-ji temple (this temple is likely to be Futai-ji still located in Nara city) and is clearly described as an image at 16 years old, and the suggestion of presence of a statue used as a model of the style attracts attention. The statue has many points in common regarding style and expression with the statue of Shotoku Taishi made by Zenshun in Gango-ji temple in Nara, and it was found out that Gyokei had a close relationship with the Zen-pa School Busshi who were active in Nara in the middle to late Kamakura period also in terms of other achievements. Materials relating to the history of this statue in the modern period and after are attached to the end of the paper

Measurement of the Branching Fraction for B->eta' K and Search for B->eta'pi+

We report measurements for two-body charmless B decays with an eta' meson in the final state. Using 11.1X10^6 BBbar pairs collected with the Belle detector, we find BF(B^+ ->eta'K^+)=(79^+12_-11 +-9)x10^-6 and BF(B^0 -> eta'K^0)=(55^+19_-16 +-8)x10^-6, where the first and second errors are statistical and systematic, respectively. No signal is observed in the mode B^+ -> eta' pi^+, and we set a 90% confidence level upper limit of BF(B^+-> eta'pi^+) eta'K^+- decays is investigated and a limit at 90% confidence level of -0.20<Acp<0.32 is obtained.Comment: Submitted to Physics Letters

Search for Direct CP Violation in B -> K pi Decays

We search for direct CP violation in flavor specific B -> K pi decays by measuring the rate asymmetry between charge conjugate modes. The search is performed on a data sample of 11.1 million B B bar events recorded on the Upsilon(4S) resonance by the Belle experiment at KEKB. We measure 90% confidence intervals in the partial rate asymmetry A_CP of -0.25 < A_CP(K-/+ pi+/-) < 0.37, -0.40 < A_CP(K-/+ pi^0) < 0.36, and -0.53 < A_CP(K^0 pi-/+) < 0.82. By combining the K-/+ pi+/- and K-/+ pi^0 final states, we conclude that -0.22 < A_CP[K-/+(pi+/- + pi^0)] < 0.25 at the 90% confidence level.Comment: Submitted to PRD Rapid Communication

A Measurement of the Branching Fraction for the Inclusive B --> X(s) gamma Decays with the Belle Detector

We have measured the branching fraction of the inclusive radiative B meson decay B --> X(s) gamma to be Br(B->X(s)gamma)=(3.36 +/- 0.53(stat) +/- 0.42(sys) +0.50-0.54(th)) x 10^{-4}. The result is based on a sample of 6.07 x 10^6 BBbar events collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric e^+e^- storage ring.Comment: 14 pages, 6 Postsript figures, uses elsart.cl

Observation of Mixing-induced CP Violation in the Neutral B Meson System

This report describes an observation of mixing-induced CP violation and a measurement of the CP violation parameter, sin(2phi_1), with the Belle detector at the KEKB asymmetric e+e- collider. Using a data sample of 29.1 fb-1 recorded on the Upsilon(4S) resonance that contains 31.3 million BBbar pairs, we reconstruct decays of neutral B mesons to the following CP eigenstates: J/psi K_S^0, psi(2S) K_S^0, chi_c1 K_S^0, eta_c K_S^0, J/psi K_L^0 and J/psi K^*0. The flavor of the accompanying B meson is identified by combining information from primary and secondary leptons, K+/- mesons, lambda baryons, slow and fast pions. The proper-time interval between the two B meson decays is determined from the distance between the two decay vertices measured with a silicon vertex detector. The result sin(2phi_1) = 0.99 +/- 0.14(stat) +/- 0.06(syst) is obtained by applying a maximum likelihood fit to the 1137 candidate events. We conclude that there is large CP violation in the neutral B meson system. A zero value for sin(2phi_1) is ruled out by more than six standard deviations.Comment: 25 pages, 16 figures, accepted for publication in Physical Review

Observation of Cabibbo suppressed B→D(∗)K−B \to D^{(*)}K^- decays at Belle

Cabibbo-suppressed decays $B \to D^{(*)} K^-$ using a 10.4 fb$^{-1}$ data sample accumulated at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ storage ring. The high-momentum particle identification system of Belle is used to isolate signals for $B\to D^0 K^-$, $D^+K^-$, $D^{*0}K^-$ and $D^{*+}K^-$ from the $B\to D^{(*)}\pi^-$ decay processes which have much larger branching fractions. We report ratios of Cabibbo-suppressed to Cabibbo-favored branching fractions of: ${\cal B}(B^- \to D^0 K^-)/{\cal B}(B^- \to D^0\pi^-) = 0.079\pm0.009\pm0.006$; ${\cal B}(\bar{B^0} \to D^+ K^-)/{\cal B}(\bar{B^0} \to D^+\pi^-) = 0.068\pm0.015\pm0.007$; ${\cal B}(B^-\to D^{*0}K^-)/{\cal B}(B^-\to D^{*0}\pi^-) = 0.078 \pm 0.019 \pm 0.009$; and ${\cal B}(\bar{B}^0\to D^{*+}K^-)/{\cal B}(\bar{B}^0\to D^{*+}\pi^-)= 0.074 \pm 0.015 \pm 0.006$. The first error is statistical and the second is systematic. These are the first reported observations of the $B\to D^+K^-$, $D^{*0}K^-$ and $D^{*+}K^-$ decay processes.Comment: LaTeX, 12 pages, 2 figure

Observation of Large CP Violation in the Neutral B Meson System

We present a measurement of the Standard Model CP violation parameter sin 2phi_1 based on a 29.1 fb^{-1} data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. One neutral B meson is fully reconstructed as a J/psi Ks, psi(2S) Ks, chi_c1 Ks, eta_c Ks, J/psi K_L or J/psi K^{*0} decay and the flavor of the accompanying B meson is identified from its decay products. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we determine sin 2phi_1 = 0.99 +- 0.14(stat) +- 0.06(syst). We conclude that we have observed CP violation in the neutral B meson system.Comment: 4 figures, to appear in Phys. Rev. Letter

Measurement of Inclusive Production of Neutral Pions from Upsilon(4S) Decays

Using the Belle detector operating at the KEKB e+e- storage ring, we have measured the mean multiplicity and the momentum spectrum of neutral pions from the decays of the Upsilon(4S) resonance. We measure a mean of 4.70 +/- 0.04 +/- 0.22 neutral pions per Upsilon(4S) decay.Comment: 15 pages, 4 figs. Submitted to Phys.Rev.

Measurement of B0d - B0d-bar mixing rate from the time evolution of dilepton events at the Upsilon(4S)

We report a determination of the B0d - B0d-bar mixing parameter Delta-m_d based on the time evolution of dilepton yields in Upsilon(4S) decays. The measurement is based on a 5.9 /fb data sample collected by the Belle detector at KEKB. The proper-time difference distributions for same-sign and opposite-sign dilepton events are simultaneously fitted to an expression containing Delta-m_d as a free parameter. Using both muons and electrons, we obtain Delta-m_d = 0.463 +- 0.008(stat.) +- 0.016(sys.) ps^{-1} This is the first determination of Delta-m_d from time evolution measurements at the Upsilon(4S). We also place limits on possible CPT violations.Comment: 12 pages, 2 figure