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1. chinaXiv:201609.01043 [pdf]

Measurements of $\pi^0\pi^0$ production and form factors for $f_0(980)$ and $f_2(1270)$ in single-tag two-photon process

Belle Collaboration
分类: 物理学 >> 核物理学

We report a measurement of differential cross section of π0 pair production in single-tag two-photon collisions. These results are obtained with 759fb−1 of the data collected with the Belle detector at the KEKB asymmetric energy e+e−collider. The cross section is measured for Q2 up to 30 GeV2, where Q2 is the negative of the invariant mass squared of the tagged virtual photon, in the kinematic range 0.5 GeV < W < 2.1 GeV and |cosθ∗| < 1.0 for the total energy and pion scattering angle, respectively. The transition form factor of the f0(980) and that of the f2(1270)with the helicity-0,-1, and -2 components separately are measured for the first time and are compared with theoretical calculations.

提交时间: 2016-09-14 点击量394下载量257 评论 0

2. chinaXiv:201609.00827 [pdf]

First Observation of Doubly Cabibbo-Suppressed Decay of a Charmed Baryon: $\Lambda^+_c \rightarrow p K^+ \pi^-$

Yang, S. B. and others
分类: 物理学 >> 核物理学

We report the first observation of the decay Λ+c→pK+π− using a 980 fb−1 data sample collected by the Belle detector at the KEKB asymmetric-energy e+e− collider. This is the first doubly Cabibbo-suppressed decay of a charmed baryon to be observed. We measure the branching ratio of this decay with respect to its Cabibbo-favored counterpart to be B(Λ+c→pK+π−)/B(Λ+c→pK−π+)=(2.35±0.27±0.21)×10−3, where the uncertainties are statistical and systematic, respectively.

提交时间: 2016-09-12 点击量305下载量195 评论 0

3. chinaXiv:201609.00825 [pdf]

First observation of the decay B$^0\to \psi$(2S)$\pi^0$

Chobanova, V. and others
分类: 物理学 >> 核物理学

We report a measurement of the B0→ψ(2S)π0 branching fraction based on the full Υ(4S) data set of 772×106 BB¯ pairs collected by the Belle detector at the KEKB asymmetric-energy e+e− collider. We obtain B(B0→ψ(2S)π0)=(1.17±0.17(stat)±0.08(syst))×10−5. The result has a significance of 7.2 standard deviations and is the first observation of the decay B0→ψ(2S)π0.

提交时间: 2016-09-12 点击量286下载量202 评论 0

4. chinaXiv:201609.00814 [pdf]

New results on the XYZ states from Belle experiment

Yuan, Chang-Zheng
分类: 物理学 >> 核物理学

We review the results on the XYZ states from the Belle experiment, including the measurement of inclusive hadronic cross sections and exclusive cross sections in e+e- annihilation and the Z_b states in the bottomonium energy region; and the study of the Y states and the Z_c states in charmonium energy region.

提交时间: 2016-09-12 点击量364下载量239 评论 0

5. chinaXiv:201609.00813 [pdf]

Search for the rare decay $D^0\to\gamma\gamma$ at Belle

Nisar, N. K. and others
分类: 物理学 >> 核物理学

We search for the rare radiative decay D0→γγ using a data sample with an integrated luminosity of 832fb−1recorded by the Belle detector at the KEKB e+e− asymmetric-energy collider. We find no statistically significant signal and set an upper limit on the branching fraction of B(D0→γγ)<8.5×10−7 at 90% confidence level. This is the most restrictive limit on the decay channel to date.

提交时间: 2016-09-12 点击量297下载量180 评论 0

6. chinaXiv:201609.00811 [pdf]

Inclusive and exclusive measurements of $B$ decays to $\chi_c1$ and $\chi_c2$ at Belle

Bhardwaj, V. and others
分类: 物理学 >> 核物理学

We report inclusive and exclusive measurements for χc1 and χc2 production in B decays. We measure B(B→χc1X)= (3.03±0.05(stat)±0.24(syst))×10−3 and B(B→χc2X)= (0.70±0.06(stat)±0.10(syst))×10−3. For the first time, χc2 production in exclusive B decays in the modes B0→χc2π−K+ and B+→χc2π+π−K+ has been observed, along with first evidence for the B+→χc2π+K0S decay mode. For χc1 production, we report the first observation in the B+→χc1π+π−K+, B0→χc1π+π−K0S and B0→χc1π0π−K+ decay modes. Using these decay modes, we observe a difference in the production mechanism of χc2 in comparison to χc1 in B decays. In addition, we report searches for X(3872) and χc1(2P) in the B+→(χc1π+π−)K+ decay mode. The reported results use 772×106 BB¯¯¯¯ events collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider.

提交时间: 2016-09-12 点击量319下载量204 评论 0

7. chinaXiv:201609.00808 [pdf]

Observation of the decay $B_s^0\rightarrow K^0\overlineK^0$

Pal, B. and others
分类: 物理学 >> 核物理学

We measure the decay B0s→K0K¯¯¯¯¯0 using data collected at the Υ(5S) resonance with the Belle detector at the KEKB e+e− collider. The data sample used corresponds to an integrated luminosity of 121.4 fb−1. We measure a branching fraction B(B0s→K0K¯¯¯¯¯0)=[19.6+5.8−5.1(stat.)±1.0(sys.)±2.0(NB0sB¯¯¯¯0s)]×10−6 with a significance of 5.1 standard deviations. This measurement constitutes the first observation of this decay.

提交时间: 2016-09-12 点击量317下载量194 评论 0

8. chinaXiv:201609.00770 [pdf]

Measurement of the decay $B\to D\ell\nu_\ell$ in fully reconstructed events and determination of the Cabibbo-Kobayashi-Maskawa matrix element $|V_cb|$

Glattauer, R. and others
分类: 物理学 >> 核物理学

We present a determination of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| using the decay B→Dℓνℓ (ℓ=e,μ) based on 711 fb−1 of e+e−→Υ(4S) data recorded by the Belle detector and containing 772×106 BB¯ pairs. One B meson in the event is fully reconstructed in a hadronic decay mode while the other, on the signal side, is partially reconstructed from a charged lepton and either a D+ or D0 meson in a total of 23 hadronic decay modes. The isospin-averaged branching fraction of the decay B→Dℓνℓ is found to be B(B0→D−ℓ+νℓ)=(2.31±0.03(stat)±0.11(syst))%. Analyzing the differential decay rate as a function of the hadronic recoil with the parameterization of Caprini, Lelouch and Neubert and using the form-factor prediction G(1)=1.0541±0.0083 calculated by FNAL/MILC, we obtain ηEW|Vcb|=(40.12±1.34)×10−3, where ηEW is the electroweak correction factor. Alternatively, assuming the model-independent form-factor parameterization of Boyd, Grinstein and Lebed and using lattice QCD data from the FNAL/MILC and HPQCD collaborations, we find ηEW|Vcb|=(41.10±1.14)×10−3.

提交时间: 2016-09-12 点击量306下载量201 评论 0

9. chinaXiv:201609.00763 [pdf]

Study of $\mathbfB^0\rightarrow\rho^+\rho^-$ decays and implications for the CKM angle $\mathbf\phi_2$

Vanhoefer, P. and others
分类: 物理学 >> 核物理学

We present a measurement of the branching fraction and the longitudinal polarization fraction of B0→ρ+ρ− decays, as well as the time-dependent CP violating parameters in decays into longitudinally polarized ρ+ρ− pairs with Belle's final data set of 772×106 BB¯ pairs, at the Υ(4S) resonance, collected at the asymmetric-energy e+e− collider KEKB. We obtain B(B0→ρ+ρ−)=(28.3±1.5(stat)±1.5(syst))×10−6, fL=0.988±0.012(stat)±0.023(syst), ACP=0.00±0.10(stat)±0.06(syst), SCP=−0.13±0.15(stat)±0.05(syst). We perform an isospin analysis to constrain the CKM angle ϕ2 and obtain two solutions with ϕ2=(93.7±10.6)∘, being most compatible with other Standard-Model based fits to the data.

提交时间: 2016-09-12 点击量266下载量174 评论 0

10. chinaXiv:201609.00757 [pdf]

Measurement of $D^0 – \bar D^0$ mixing and search for CP violation in $D^0 \to K^+ K^−, \pi^+ \pi^−$ decays with the full Belle data set

Starič, M. and others
分类: 物理学 >> 核物理学

We report an improved measurement of D0-D0bar mixing and a search for CP violation in D0 decays to CP-even final states K+K- and pi+pi-. The measurement is based on the final Belle data sample of 976/fb. The results are y_CP=(1.11 +- 0.22 +- 0.09)% and A_Gamma=(-0.03 +- 0.20 +- 0.07)%, where the first uncertainty is statistical and the second is systematic.

提交时间: 2016-09-12 点击量288下载量203 评论 0

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