The Belle II experiment at the SuperKEKB collider of KEK (Japan) will accumulate 50 ab$^{-1}$ of e$^+$e$^-$ collision data at an unprecedented instantaneous luminosity of 8 $\times 10^{35}$ cm$^{-2}$s$^{-1}$, about 40 times larger than its predecessor. The Belle II vertex detector plays a crucial role in the rich Belle II physics program, especially for time-dependent measurements. It consists of two layers of DEPFET-based pixels and four layers of double sided silicon strips detectors(SVD). The vertex detector has been recently completed and installed in Belle II for the physics run started in spring 2019. We report here results on the commissioning of the SVD and its performance measured with the first collision data set.

STRIPS

10.22323/1.364.0148

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Results from the current experiments: BaBar, Belle, CLEO

EPJ direct (2002)

H. Aihara

CP violation

10.1007/s1010502cs127

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Study of B ! K Decays

arXiv (Cornell University) (2008)

P. Chang I. Adachi H. Aihara K. Arinstein T. Aushev

We report an observation of the decay B^\pm -> \phi \phi K^\pm and evidence for B^0 -> \phi \phi K^0. These results are based on a 414 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy e^+e^- collider operating at the \Upsilon(4S) resonance. The branching fractions for these decay modes are measured to be Br(B^{\pm} -> \phi \phi K^\pm) = (3.2^{+0.6}_{-0.5} +- 0.3) * 10^{-6} and Br(B^{0} \to \phi \phi K^{0}) = (2.3^{+1.0}_{-0.7} +- 0.2) * 10^{-6} for \phi \phi invariant mass below 2.85 GeV/c^2. The corresponding partial rate asymmetry for the charged B mode is measured to be A_{CP}(B^\pm -> \phi \phi K^\pm) = 0.01^{+0.19}_{-0.16} +- 0.02. We also study the decays B^\pm -> J/\psi K^\pm and B^\pm -> \eta_c K^\pm, where the J/\psi and \eta_c decay to final states with four charged kaons. We find A_{CP}(B^\pm -> \phi \phi K^\pm) with the \phi\phi candidates within the \eta_c mass region is 0.15^{+0.16}_{-0.17} +- 0.02, consistent with no asymmetry.

KEKB

Branching fraction

Electron–positron annihilation

Invariant mass

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Observation of B+->(Xi)over-bar(c)(0)Lambda(+)(c) and evidence for B-0 ->(Xi)over-bar(c)(-)Lambda(+)(c)

R. Chistov K. Abe I. Adachi H. Aihara D. Anipko

We report the first observation of the decay B+->(Xi) over bar (0)(c)Lambda(+)(c) with a significance of 8.7 sigma and evidence for the decay B-0 ->(Xi) over bar (-)(c)Lambda(+)(c) with a significance of 3.8 sigma. The product B(B+->(Xi) over bar (0)(c)Lambda(+)(c))xB (Xi) over bar (0)(c)->(Xi) over bar (+)pi(-)) is measured to be (4.8(-0.9)(+1.0)+/- 1.1 +/- 1.2)x10(-5), and B(B-0 ->(Xi) over bar (-)(c)Lambda(+)(c))xB ($) over bar (-)(c)->(Xi) over bar (+)pi(-)pi(-)) is measured to be (9.3(-2.8)(+3.7)+/- 1.9 +/- 2.4)x10(-5). The errors are statistical, systematic and the error of the Lambda(+)(c)-> pK(-)pi(+) branching fraction, respectively. The decay B+->(Xi) over bar (0)(c)Lambda(+)(c) is the first example of a two-body exclusive B+ decay into two charmed baryons. The data used for this analysis was accumulated at the Upsilon(4S) resonance, using the Belle detector at the e(+)e(-) asymmetric-energy collider KEKB. The integrated luminosity of the data sample is equal to 357 fb(-1), corresponding to 386x10(6) (B) over bar pairs.

KEKB

Bar (unit)

Branching fraction

Electron–positron annihilation

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Observation of B-0 -> D*-(5 pi)(+), B+ -> D*-(4 pi)(++) and B+ -> (D)over-bar(*0)(5 pi)(+)

Physical Review D (2004)

G. Majumder K. Abe I. Adachi H. Aihara M. Akatsu

We report the first observation of a number of decay modes of the B meson, namely B-0-->D*-(5pi)(+), B+-->D*-(4pi)(++), and B+-->(D) over bar (*0)(5pi)(+), where (npi) implies the combination of n charged pions. The analysis is based on a 140 fb(-1) data sample collected at the Y(4S) resonance with the Belle detector at KEKB. We measure B[B-0-->D*-(5pi)(+)]=(4.72+/-0.59+/-0.71)x10(-3), B[B+-->D*-(4pi)(++)]=(2.56+/-0.26+/-0.33)x10(-3), and B[B+-->(D) over bar (*0)(5pi)(+)]=(5.67+/-0.91+/-0.85)x10(-3). We also provide improved measurements of the branching fractions for the decay modes B-0-->D*-(3pi)(+), B+-->(D) over bar (*0)(3pi)(+), and B-0-->(D) over bar (*0)(4pi)(0).

KEKB

Electron–positron annihilation

Bar (unit)

B meson

Branching fraction

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Measurements of the branching fractions for $B \to K^{*}γ$ decays at Belle II

arXiv (Cornell University) (2021)

F. Abudinén I. Adachi R. Adak K. Adamczyk L. Aggarwal

This paper reports a study of $B \to K^{*}\gamma$ decays using $62.8\pm 0.6$ fb$^{-1}$ of data collected during 2019--2020 by the Belle II experiment at the SuperKEKB $e^{+}e^{-}$ asymmetric-energy collider, corresponding to $(68.2 \pm 0.8) \times 10^6$ $B\overline{B}$ events. We find $454 \pm 28$, $50 \pm 10$, $169 \pm 18$, and $160 \pm 17$ signal events in the decay modes $B^{0} \to K^{*0}[K^{+}\pi^{-}]\gamma$, $B^{0} \to K^{*0}[K^0_{\rm S}\pi^{0}]\gamma$, $B^{+} \to K^{*+}[K^{+}\pi^{0}]\gamma$, and $B^{+} \to K^{*+}[K^{+}\pi^{0}]\gamma$, respectively. The uncertainties quoted for the signal yield are statistical only. We report the branching fractions of these decays: $$\mathcal{B} [B^{0} \to K^{*0}[K^{+}\pi^{-}]\gamma] = (4.5 \pm 0.3 \pm 0.2) \times 10^{-5}, $$ $$\mathcal{B} [B^{0} \to K^{*0}[K^0_{\rm S}\pi^{0}]\gamma] = (4.4 \pm 0.9 \pm 0.6) \times 10^{-5},$$ $$\mathcal{B} [B^{+} \to K^{*+}[K^{+}\pi^{0}]\gamma] = (5.0 \pm 0.5 \pm 0.4)\times 10^{-5},\text{ and}$$ $$\mathcal{B} [B^{+} \to K^{*+}[K^0_{\rm S}\pi^{+}]\gamma] = (5.4 \pm 0.6 \pm 0.4) \times 10^{-5},$$ where the first uncertainty is statistical, and the second is systematic. The results are consistent with world-average values.

Branching fraction

Electron–positron annihilation

10.48550/arxiv.2110.08219

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同定した軽い荷電ハドロンの単一および対の包括断面積の更新【JST・京大機械翻訳】

Physical Review D (2020)

R. Seidl I. Adachi H. Aihara D. M. Asner V. Aulchenko

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Measurement of theτLepton Mass and an Upper Limit on the Mass Difference betweenτ+andτ−

Physical Review Letters (2007)

K. Belous M. Shapkin A. Sokolov K. Abe K. Abe

The mass of the τ lepton has been measured in the decay mode τ→3πντ using a pseudomass technique. The result obtained from 414 fb−1 of data collected with the Belle detector is Mτ=[1776.61±0.13(stat)±0.35(sys)] MeV/c2. The upper limit on the relative mass difference between positive and negative τ leptons is |Mτ+−Mτ−|/Mτ<2.8×10−4 at 90% confidence level.Received 2 February 2007DOI:https://doi.org/10.1103/PhysRevLett.99.011801©2007 American Physical Society

10.1103/physrevlett.99.011801

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Search for B0-->p[overline p], Lambda[overline Lambda ] and B+-->p[overline Lambda ] at Belle

Physical Review D (2007)

Yun-Tse Tsai P. Chang K. Abe I. Adachi H. Aihara

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