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論文

Search for transitions from $$Upsilon(4S)$$ and $$Upsilon(5S)$$ to $$eta_b(1S)$$ and $$eta_b(2S)$$ with emission of an $$omega$$ meson

Oskin, P.*; 谷田 聖; Belle Collaboration*; 他198名*

Physical Review D, 102(9), p.092011_1 - 092011_8, 2020/11

 被引用回数:0 パーセンタイル:0.01(Astronomy & Astrophysics)

Using data collected in the Belle experiment at the KEKB asymmetric-energy $$e^+e^-$$ collider we search for transitions $$Upsilon(4S) rightarrow eta_b(1S)omega$$, $$Upsilon(5S) rightarrow eta_b(1S)omega$$ and $$Upsilon(5S) rightarrow eta_b(2S)omega$$. No significant signals are observed and we set 90% confidence level upper limits on the corresponding visible cross sections: $$0.2 ~textrm{pb}, 0.4 ~textrm{pb}$$ and $$1.9 ~textrm{pb}$$, respectively.

論文

Observation of $$tau^- rightarrow pi^- nu_{tau} e^+ e^- $$ and search for $$tau^- rightarrow pi^- nu_{tau} mu^+ mu^-$$

Jin, Y.*; 谷田 聖; Belle Collaboration*; 他198名*

Physical Review D, 100(7), p.071101_1 - 071101_9, 2019/10

 被引用回数:1 パーセンタイル:13.19(Astronomy & Astrophysics)

We present the first measurements of branching fractions of rare tau-lepton decays, $$tau^- rightarrow pi^- nu_{tau} ell^+ ell^-$$ ($$ell = e$$ or $$mu$$), using a data sample corresponding to 562 fb$$^{-1}$$ collected at a center-of-mass energy of 10.58 GeV with the Belle detector at the KEKB asymmetric-energy $$e^+ e^-$$ collider. The $$tau^- rightarrow pi^- nu_tau e^+ e^-$$ decay is observed for the first time with 7.0$$sigma$$ significance. The partial branching fraction determined by the structure-dependent mechanisms mediated by either a vector or an axial-vector current for the mass region $$M_{pi e e} > 1.05$$ GeV/$$c^2$$ is measured to be $$mathcal{B}(tau^-rightarrow pi^- nu_tau e^+ e^-)[M_{pi^- e^+ e^-} > 1.05~{rm GeV}/c^2] = (5.90 pm 0.53 pm 0.85 pm 0.11) times 10^{-6}$$, where the first uncertainty is statistical, the second is systematic, and the third is due to the model dependence. In the full phase space, due to the different detection efficiencies for the structure-dependent mechanisms mediated by axial-vector and vector currents, the branching fraction varies from $$mathcal{B}_{A}(tau^-rightarrow pi^- nu_tau e^+ e^-) = (1.46 pm 0.13 pm 0.21) times 10^{-5}$$ to $$mathcal{B}_{V}(tau^-rightarrow pi^- nu_tau e^+ e^-) = (3.01 pm 0.27 pm 0.43) times 10^{-5}$$, respectively. An upper limit is set on the branching fraction of the $$tau^- rightarrow pi^- nu_tau mu^+ mu^-$$ decay, $$mathcal{B}(tau^-rightarrow pi^- nu_tau mu^+ mu^-) < 1.14 times 10^{-5}$$, at the 90% confidence level.

論文

Search for $$CP$$ violation and measurement of the branching fraction in the decay $$D^{0} to K^0_S K^0_S$$

Dash, N.*; 谷田 聖; Belle Collaboration*; 他198名*

Physical Review Letters, 119(17), p.171801_1 - 171801_7, 2017/10

 被引用回数:21 パーセンタイル:83.81(Physics, Multidisciplinary)

We report a study of the decay $$D^{0} to K^0_S K^0_S$$ using 921 fb$$^{-1}$$ of data collected at or near the $$Upsilon(4S)$$ and $$Upsilon(5S)$$ resonances with the Belle detector at the KEKB asymmetric energy $$e^+e^-$$ collider. The measured time-integrated $$CP$$ asymmetry is $$A_{CP}(D^{0} to K^0_S K^0_S)=(-0.02 pm 1.53 pm 0.02 pm 0.17)%$$, and the branching fraction is $$B(D^{0} to K^0_S K^0_S)=(1.321 pm 0.023 pm 0.036 pm 0.044) times 10^{-4}$$, where the first uncertainty is statistical, the second is systematic, and the third is due to the normalization mode ($$D^{0} to K^0_S pi^0$$). These results are significantly more precise than previous measurements available for this mode. The $$A_{CP}$$ measurement is consistent with the standard model expectation.

論文

Construction and test of the first Belle II SVD ladder implementing the origami chip-on-sensor design

Irmler, C.*; 谷田 聖; 他98名*

Journal of Instrumentation (Internet), 11(1), p.C01087_1 - C01087_9, 2016/01

 被引用回数:5 パーセンタイル:34.01(Instruments & Instrumentation)

The Belle II Silicon Vertex Detector comprises four layers of double-sided silicon strip detectors (DSSDs), consisting of ladders with two to five sensors each. All sensors are individually read out by APV25 chips with the Origami chip-on-sensor concept for the central DSSDs of the ladders. The chips sit on flexible circuits that are glued on the top of the sensors. This concept allows a low material budget and an efficient cooling of the chips by a single pipe per ladder. We present the construction of the first SVD ladders and results from precision measurements and electrical tests.

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