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論文

Measurement of $$cos{2beta}$$ in $$B^{0} to D^{(*)} h^{0}$$ with $$D to K_{S}^{0} pi^{+} pi^{-}$$ decays by a combined time-dependent Dalitz plot analysis of $$B_{A}B_{AR}$$ and Belle data

足立 一郎*; 谷田 聖; Belle Collaboration*; 他406名*

Physical Review D, 98(11), p.112012_1 - 112012_29, 2018/11

AA2018-0713.pdf:4.08MB

 被引用回数:12 パーセンタイル:64.07(Astronomy & Astrophysics)

We report measurements of $$sin{2beta}$$ and $$cos{2beta}$$ from a time-dependent Dalitz plot analysis of $$B^{0} to D^{(*)} h^{0}$$ with $$D to K_{S}^{0} pi^{+} pi^{-}$$ decays, where the light unflavored and neutral hadron $$h^{0}$$ is a $$pi^{0}$$, $$eta$$, or $$omega$$ meson. The analysis is performed with a combination of the final data sets of the BABAR and Belle experiments containing $$471 times 10^{6}$$ and $$772 times 10^{6}$$ $$Bbar{B}$$ pairs collected at the $$Upsilonleft(4Sright)$$ resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. We measure $$sin{2beta} = 0.80 pm 0.14 ,(rm{stat.}) pm 0.06 ,(rm{syst.}) pm 0.03 ,(rm{model})$$ and $$cos{2beta} = 0.91 pm 0.22 ,(rm{stat.}) pm 0.09 ,(rm{syst.}) pm 0.07 ,(rm{model})$$. The result for the direct measurement of the angle is $$beta = left( 22.5 pm 4.4 ,(rm{stat.}) pm 1.2 ,(rm{syst.}) pm 0.6 ,(rm{model}) right)^{circ}$$. The last quoted uncertainties are due to the composition of the $$D^{0} to K_{S}^{0} pi^{+} pi^{-}$$ decay amplitude model, which is newly established by a Dalitz plot amplitude analysis of a high-statistics $$e^{+}e^{-} to cbar{c}$$ data sample as part of this analysis. We find the first evidence for $$cos2beta>0$$ at the level of $$3.7$$ standard deviations. The measurement excludes the trigonometric multifold solution $$pi/2 - beta = (68.1 pm 0.7)^{circ}$$ at the level of $$7.3$$ standard deviations and therefore resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle. The hypothesis of $$beta = 0^{circ}$$ is ruled out at the level of $$5.1$$ standard deviations, and thus $$CP$$ violation is observed in $$B^{0} to D^{(*)} h^{0}$$ decays.

論文

Inclusive cross section and double-helicity asymmetry for $$pi^0$$ production at midrapidity in $$p+p$$ collisions at $$sqrt{s}=510$$ GeV

Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他406名*

Physical Review D, 93(1), p.011501_1 - 011501_8, 2016/01

 被引用回数:35 パーセンタイル:83.85(Astronomy & Astrophysics)

PHENIX measurements are presented for the cross section and double-helicity asymmetry ($$A_{LL}$$) in inclusive $$pi^0$$ production at midrapidity from $$p+p$$ collisions at $$sqrt{s}=510$$ GeV from data taken in 2012 and 2013 at the Relativistic Heavy Ion Collider. The next-to-leading-order perturbative-quantum-chromodynamics theory calculation is in excellent agreement with the presented cross section results. The calculation utilized parton-to-pion fragmentation functions from the recent DSS14 global analysis, which prefer a smaller gluon-to-pion fragmentation function. The $$pi^0; A_{LL}$$ results follow an increasingly positive asymmetry trend with $$p_T$$ and $$sqrt{s}$$ with respect to the predictions and are in excellent agreement with the latest global analysis results. This analysis incorporated earlier results on $$pi^0$$ and jet ALL and suggested a positive contribution of gluon polarization to the spin of the proton $$Delta G$$ for the gluon momentum fraction range $$x>0.05$$. The data presented here extend to a currently unexplored region, down to $$x sim 0.01$$, and thus provide additional constraints on the value of $$Delta G$$.

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