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論文

Measurement of the $$B^+/B^0$$ production ratio in $$e^+e^-$$ collisions at the $$Upsilon(4S)$$ resonance using $$B rightarrow J/psi(ellell) K$$ decays at Belle

Choudhury, S.*; 谷田 聖; Belle Collaboration*; 他198名*

Physical Review D, 107(3), p.L031102_1 - L031102_6, 2023/02

https://doi.org/10.1103/PhysRevD.107.L031102
 被引用回数：12 パーセンタイル：72.68(Astronomy & Astrophysics)

We measure the ratio of branching fractions for the $$Upsilon (4S)$$ decays to $$B^+B^-$$ and $$B^0bar{B}{}^0$$ using $$B^+ rightarrow J/psi(ellell) K^+$$ and $$B^0 rightarrow J/psi(ellell) K^0$$ samples, where $$J/psi(ellell)$$ stands for $$J/psi to ell^+ell^-$$ ($$ell = e$$ or $$mu$$), with $$711$$ fb$$^{-1}$$ of data collected at the $$Upsilon(4S)$$ resonance with the Belle detector. We find the decay rate ratio of $$Upsilon(4S) rightarrow B^+B^-$$ over $$Upsilon(4S) rightarrow B^0bar{B}{}^0$$ to be $$1.065pm0.012pm 0.019 pm 0.047$$, which is the most precise measurement to date. The first and second uncertainties are statistical and systematic, respectively, and the third uncertainty is systematic due to the assumption of isospin symmetry in $$B to J/psi(ellell) K$$.

論文

Measurements of the branching fractions $$mathcal{B} (bar{B}{}^0 to D^{*+} pi^-)$$ and $$mathcal{B} (bar{B}{}^0 to D^{*+} K^-)$$ and tests of QCD factorization

Krohn, J.-F.*; 谷田 聖; Belle Collaboration*; 他198名*

Physical Review D, 107(1), p.012003_1 - 012003_12, 2023/01

https://doi.org/10.1103/PhysRevD.107.012003
 被引用回数：3 パーセンタイル：15.61(Astronomy & Astrophysics)

Using $$(771.6 pm 10.6) times 10^6$$ $$Bbar{B}$$ meson pairs recorded by the Belle experiment at the KEKB $$e^+ e^-$$ collider, we report the branching fractions $$mathcal{B}(bar{B}^0 to D^{*+} pi^-) = (2.62 pm 0.02 pm 0.09)times 10^{-3}$$ and $$mathcal{B}(bar{B}^0 to D^{*+} K^-) = (2.22 pm 0.06 pm 0.08)times 10^{-4}$$; the quoted uncertainties are statistical and systematic, respectively. A measurement of the ratio of these branching fractions is also presented, $$mathcal{R}_{K/pi}=mathcal{B}(bar{B} to D^{*+}K^-) /mathcal{B}(bar{B} to D^{*+}pi^-) = (8.41 pm 0.24 pm 0.13)times 10^{-2}$$, where systematic uncertainties due to the $$D^{*+}$$ meson reconstruction cancel out. Furthermore, we report a new QCD factorization test based on the measured ratios for $$bar{B} to D^{*+}h^-$$ and $$bar{B} to D^{*+}ell^-nu$$ decays at squared momentum transfer values equivalent to the mass of the $$h = pi$$ or $$K$$ hadron. The parameters $$|a_1(h)|$$ are measured to be $$|a_1(pi)|= 0.884 pm 0.004 pm 0.003 pm 0.016$$ and $$|a_1(K)|=0.913 pm 0.019 pm 0.008 pm 0.013$$, where the last uncertainties account for all external inputs. These values are approximately $$15%$$ lower than those expected from theoretical predictions. Subsequently, flavor $$SU(3)$$ symmetry is tested by measuring the ratios for pions and kaons, $$|a_1(K)|^2/ |a_1(pi)|^2=1.066 pm 0.042 pm 0.018 pm 0.023$$, as well as for different particle species. The ratio is consistent with unity and therefore no evidence for $$SU(3)$$ symmetry breaking effects is found at the $$5%$$ precision level.

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

https://doi.org/10.1103/PhysRevD.102.092011
 被引用回数：0 パーセンタイル：0.00(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

https://doi.org/10.1103/PhysRevD.100.071101
 被引用回数：4 パーセンタイル：21.83(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

AA2017-0514.pdf:0.35MB

https://doi.org/10.1103/PhysRevLett.119.171801
 被引用回数：38 パーセンタイル：85.32(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

https://doi.org/10.1088/1748-0221/11/01/C01087
 被引用回数：6 パーセンタイル：28.24(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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