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論文

First evidence for cos 2$$beta >$$ 0 and resolution of the Cabibbo-Kobayashi-Maskawa Quark-Mixing Unitarity Triangle ambiguity

足立 一郎*; 谷田 聖; Belle Collaboration*; 他421名*

Physical Review Letters, 121(26), p.261801_1 - 261801_11, 2018/12

 被引用回数:1 パーセンタイル:49.95(Physics, Multidisciplinary)

We present first evidence that the cosine of the $$CP$$-violating weak phase $$2beta$$ is positive, and hence exclude trigonometric multifold solutions of the CKM Unitarity Triangle using a time-dependent Dalitz plot analysis of $$B^{0} to D^{(*)} h^{0}$$ with $$D to K_{S}^{0} pi^{+} pi^{-}$$ decays, where $$h^{0} in {pi^{0}, eta, omega }$$ denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BaBar and Belle experiments collected at the $$Upsilon(4S)$$ resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain $$( 471 pm 3 )times 10^6, Bbar{B}$$ pairs recorded by the BaBar detector and $$( 772 pm 11 )times 10^6, Bbar{B}$$ pairs recorded by the Belle detector. The results of the measurement are $$sin{2beta} = 0.80 pm 0.14 ,(rm{stat.}) pm 0.06 ,(rm{syst.}) pm 0.03 ,(rm{model})$$ 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 $$beta$$ of the CKM Unitarity Triangle is $$beta = left( 22.5 pm 4.4 ,(rm{stat.}) pm 1.2 ,(rm{syst.}) pm 0.6 ,(rm{model}) right)^{circ}$$. The quoted model uncertainties are due to the composition of the $$D^{0} to K_{S}^{0} pi^{+} pi^{-}$$ decay amplitude model, which is newly established by performing a Dalitz plot amplitude analysis using a high-statistics $$e^{+}e^{-} to cbar{c}$$ data sample. CP violation is observed in $$B^{0} to D^{(*)} h^{0}$$ decays at the level of $$5.1$$ standard deviations. The significance for $$cos{2beta} > 0$$ is $$3.7$$ standard deviations. The trigonometric multifold solution $$pi/2 - beta = (68.1 pm 0.7)^{circ}$$ is excluded at the level of $$7.3$$ standard deviations. The measurement resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle.

論文

Measurement of long-range angular correlation and quadrupole anisotropy of pions and (anti)protons in central d+Au collisions at $$sqrt{s_{NN}} = 200$$ GeV

Adare, A.*; 今井 憲一; 谷田 聖; PHENIX Collaboration*; 他421名*

Physical Review Letters, 114(19), p.192301_1 - 192301_8, 2015/05

AA2015-0709.pdf:0.4MB

 被引用回数:88 パーセンタイル:1.43(Physics, Multidisciplinary)

We present azimuthal angular correlations between charged hadrons and energy deposited in calorimeter towers in central $$d$$ + Au and minimum bias $$p+p$$ collisions at $$sqrt{s_{NN}} = 200$$ GeV. The charged hadron is measured at midrapidity $$|eta| < 0.35$$, and the energy is measured at large rapidity ($$-3.7 < eta < -3.1$$, Au-going direction). An enhanced near-side angular correlation across $$|eta| < 2.75$$ is observed in $$d$$+Au collisions. Using the event plane method applied to the Au-going energy distribution, we extract the anisotropy strength $$v_2$$ for inclusive charged hadrons at midrapidity up to $$p_T < 4.5; {rm GeV}/c$$. We also present the measurement of $$v_2$$ for identified $$pi^{pm}$$ and and (anti)protons in central $$d$$ + Au collisions, and observe a mass-ordering pattern similar to that seen in heavy-ion collisions. These results are compared with viscous hydrodynamic calculations and measurements from $$p$$ + Pb at $$sqrt{s_{NN}}$$ = 5.02 TeV. The magnitude of the mass ordering in $$d$$+Au is found to be smaller than that in $$p$$+Pb collisions, which may indicate smaller radial flow in lower energy $$d$$+Au collisions.

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