arXiv subjects

K. Kinoshita

Publications and source records attributed to K. Kinoshita.

268 records · Page 15Linked to original sources

arXiv2011

Evidence for the Suppressed Decay B- -> DK-, D -> K+pi-

The suppressed decay chain B- -> DK-, D -> K+pi-, where D indicates a anti-D0 or D0 state, provides important information on the CP-violating angle phi_3. We measure the ratio R_{DK} of the decay rates to the favored mode B- -> DK-, D -> K-pi+ to be R_{DK} = [1.63^{+0.44}_{-0.41}(stat)^{+0.07}_{-0.13}(syst)] x 10^{-2}, which indicates the first evidence of the signal with a significance of 4.1sigma. We also measure the asymmetry A_{DK} between the charge-conjugate decays to be A_{DK} = -0.39^{+0.26}_{-0.28}(stat)^{+0.04}_{-0.03}(syst). The results are based on the full 772 x 10^6 B anti-B pair data sample collected at the Upsilon(4S) resonance with the Belle detector.

hep-ex↗

arXiv2011

Measurements of time-dependent CP asymmetries in $B \to D^{*\mp} π^{\pm}$ decays using a partial reconstruction technique

We report results on time-dependent CP asymmetries in $B \to D^{*\mp}π^{\pm}$ decays based on a data sample containing 657 {\times} $10^6$ $B\bar{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider at the $Υ(4S)$ resonance. We use a partial reconstruction technique, wherein signal $B \to D^{*\mp}π^{\pm}$ events are identified using information only from the fast pion from the B decay and the slow pion from the subsequent decay of the $D^{*\mp}$, where the former (latter) corresponds to $D^{*+} (D^{*-})$ final states. We obtain CP violation parameters $S^+ = +0.061 \pm 0.018(\mathrm{stat}) \pm 0.012(\mathrm{syst})$ and $S^- = +0.031 \pm 0.019(\mathrm{stat}) \pm 0.015(\mathrm{syst})$.

hep-ex↗

arXiv2011

Measurement of the decay $B^0\toπ^-\ell^+ν$ and determination of $|V_{ub}|$

We present a measurement of the charmless semileptonic decay $B^0\toπ^-\ell^+ν$ using a data sample containing 657$\times 10^6$ $B\bar{B}$ events collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider operating near the $Υ(4S)$ resonance. We determine the total branching fraction of the decay, $\mathcal{B}(B^0\toπ^-\ell^+ν)=(1.49\pm 0.04{(\mathrm{stat})}\pm 0.07{(\mathrm{syst})})\times 10^{-4}$. We also report a new precise measurement of the differential decay rate, and extract the Cabibbo-Kobayashi-Maskawa matrix element $|V_{ub}|$ using model-independent and -dependent approaches. From a simultaneous fit to the measured differential decay rate and lattice QCD results, we obtain $|V_{ub}|=(3.43\pm 0.33)\times 10^{-3}$, where the error includes both statistical and systematic uncertainties.

hep-ex↗

arXiv2010

Observation of Bs->Ds()+Ds()- using e+e- collisions and a determination of the Bs-Bsbar width difference ΔΓ_s

We have made the first observation of Bs->Ds(*)+Ds(*)- decays using 23.6 fb-1 of data recorded by the Belle experiment running on the Upsilon(5S) resonance. The branching fractions are measured to be B(B^0_s\ra D^+_s D^-_s) = (1.0\,^{+0.4}_{-0.3}\,^{+0.3}_{-0.2})%, B(B^0_s\ra D^{*\pm}_s D^{\mp}_s) = (2.8\,^{+0.8}_{-0.7}\,\pm 0.7)%, and B(B^0_s\ra D^{*+}_s D^{*-}_s) = (3.1\,^{+1.2}_{-1.0}\,\pm 0.8)%; the sum is B(B^0_s\ra D^{(*)+}_s D^{(*)-}_s) = (6.9\,^{+1.5}_{-1.3}\,\pm 1.9)%. Assuming Bs->Ds(*)+Ds(*)- saturates decays to CP-even final states, the branching fraction determines the ratio ΔΓ_s/cos(ϕ), where ΔΓ_s is the difference in widths between the two Bs-Bsbar mass eigenstates, and ϕis a CP-violating weak phase. Taking CP violation to be negligibly small, we obtain ΔΓ_s/Γ_s = 0.147^{+0.036}_{-0.030}(stat.)^{+0.044}_{-0.042}(syst.), where Γ_s is the mean decay width.

hep-ex↗

arXiv2010

First Measurement of Inclusive B -> X_s eta Decays

We report a first measurement of inclusive B -> X_s eta decays, where X_s is a charmless state with unit strangeness. The measurement is based on a pseudo-inclusive reconstruction technique and uses a sample of 657 x 10^6 BB-bar pairs accumulated with the Belle detector at the KEKB e^+e^- collider. For M_{X_s} < 2.6 GeV/c^2, we measure a branching fraction of (26.1 +/- 3.0 (stat) +1.9 -2.1 (syst) +4.0 -7.1 (model)) x 10^-5 and a direct CP asymmetry of A_{CP} = -0.13 +/- 0.04 +0.02 -0.03. Over half of the signal occurs in the range M_{X_s} > 1.8 GeV/c^2.

hep-ex↗

arXiv2010

Physics at Super B Factory

This report presents the results of studies that investigate the physics reach at a Super $B$ factory, an asymmetric-energy $e^+e^-$ collider with a design luminosity of $8 \times 10^{35}$ cm$^{-2}$s$^{-1}$, which is around 50 times as large as the peak luminosity achieved by the KEKB collider. The studies focus on flavor physics and CP violation measurements that could be carried out in the LHC era. The physics motivation, key observables, measurement methods and expected precisions are presented.

hep-ex↗

arXiv2008

Prospects for Upgrade of KEKB

The Belle experiment at the KEKB electron-positron collider is expected to have collected close to one billion $Υ$(4S) events by the time it comes to an end in 2009. An upgrade to KEKB has been proposed. It is designed for an order of magnitude higher luminosity than KEKB, following a three-year construction period. The ultimate goal of $8 \times 10^{35}{\rm cm}^{-2}{\rm s}^{-1}$ luminosity would be reached through further improvements over several years. To exploit the physics accessible through this improved luminosity, an upgrade of the Belle detector is also planned. A new international collaboration, temporarily named sBelle, is in the process of being formed. Super-KEKB and sBelle were officially placed on the KEK 5-year Roadmap in early 2008.

hep-ex↗

arXiv2008

Measurements of time-dependent CP Asymmetries in $B \to D^{*\mp} π^{\pm}$ decays using a partial reconstruction technique

We report preliminary results on time-dependent CP asymmetries in $B \to D^{*\mp}π^{\pm}$ decays. The CP asymmetry in these decays is proportional to $2R_{D^{*} π} \sin (2ϕ_1 + ϕ_3 \pm δ_{D^{*} π})$, where $R_{D^{*} π}$ is the ratio of the magnitudes of the doubly-Cabibbo-suppressed and Cabibbo-favoured amplitudes, $δ_{D^{*} π}$ is the strong phase difference between them, and $ϕ_1$ and $ϕ_3$ are two angles of the CKM Unitarity Triangle. This study is based on a large data sample that contains 657 million $B\bar{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider at the $Υ(4S)$ resonance. We use a partial reconstruction technique, wherein signal $B \to D^{*\mp}π^{\pm}$ events are identified using information only from the $π^{\pm}$ from the $B$ decay and the charged slow pion from the subsequent decay of the $D^{*-}$. We obtain $S^+ (D^* π) = +0.057 \pm 0.019(\mathrm{stat}) \pm 0.012(\mathrm{sys})$ and $S^- (D^* π) = +0.038 \pm 0.020(\mathrm{stat}) \pm 0.010(\mathrm{sys})$.

hep-ex↗

arXiv2008

Results from Upsilon(5S) at Belle: Strange Beauty and other Beasts

The Belle experiment collected in 2005-6 a total of 23.6 fb$^{-1}$ of data at the $Υ(10860)$ resonance, also known as $Υ$(5S). These constitute nearly all of the world's sample of $e^+e^- \to Υ$(10860) events, which provide clean $B_s$ pairs. We present here several $B_s$ and $Υ$(10860) properties recently extracted from these data.

hep-ex↗

arXiv2007

Searching for New Physics: Results from Belle and Babar

The $B$-factories provide rich opportunities to search for new phenomena, in $B$, charm, and tau decays. Presented here is a selection of recent results from Belle and Babar.

hep-ex↗

arXiv2005

Sides of "The" Unitarity Triangle: Results from Belle and Babar

The principal goal of the B-factories is to test the CKM paradigm through measurements that overconstrain the shape of the so-called Unitarity Triangle. The sides of the triangle are evaluated through absolute values of several elements of the CKM matrix, so achieving high precision on these is an important aspect of the B-factory program. Recent results from Belle and Babar are presented.

hep-ex↗

arXiv2003

An Unbinned Goodness-of-Fit Test Based on the Random Walk

We describe a test statistic for unbinned goodness-of-fit of data in one dimension. The statistic is based on the two-dimensional Random Walk. The rejection power of this test is explored both for simple and compound hypotheses and, for the examples explored, it is found to be comparable to that for the chisquare test. We discuss briefly how it may be possible to extend this test to multi-dimensional data.

physics.data-an↗

arXiv2001

Dynamics vs electronic states of vortex core of high-T_c superconductors investigated by high-frequency impedance measurement

Dynamics of vortices reflects the electronic states of quasiparticles in the core. To understand this, we investigated the following three issues. (1) We investigated the complex surface impedance, Zs, of YBa2Cu3Oy as a function of magnetic field, H. The total features were well expressed by the Coffey-Clem model. From the data, we estimated the viscosity and pinning frequency, which were found to be independent of frequency. In particular, the obtained viscosity definitely shows that the core of vortex of YBa2Cu3Oy is moderately clean. This result suggests that new physics will show up, for the physics of quantum moderately clean vortex core is unknown at all. (2) An anomaly found in the surface reactance at the first order transition (FOT) of vortex lattice was investigated in Bi2Sr2CaCu2Oy with various doping levels. As a result, the anomaly was found only in the samples exhibiting the FOT. On the other hand, we did not observe the anomaly in YBa2Cu3Oy. These suggest that the anomaly is due to the change in the electronic states of the vortices characteristic of materials with very strong anisotropy. (3) We measured H dependence of both the thermal conductivity κ(H) and Zs(H) in exactly the same pieces of crystal. We could not find any anomaly in Zs(H) even at the onset of the plateau. This result suggests that the origin of the plateau in κ(H) is not a drastic phase transition but is rather gradual crossover.

cond-mat.supr-con↗

arXiv2001

CP Results from Belle

The Belle detector at KEKB has collected 6.2 fb^{-1} of data at the Upsilon(4S) resonance. Presented here are preliminary measurements, from this data sample, of sin(2phi_1) and other quantities relating to CP.

hep-ex↗

arXiv1999

Probing CKM via Semileptonic B Decays at the Upsilon(4S)

Semileptonic decays of B mesons may be used in many different ways to probe the CKM matrix. Presented here are several recent results from the CLEO II experiment, all involving the analysis or utilization of semileptonic B decays.

hep-ex↗

arXiv1997

Charmed Hadron Production in πp and Kp Collisions and Leading Particle Effect by Constituent Quark-Diquark Cascade Model

We investigate the meson, baryon and anti-baryon productions in πp and Kp collisions in terms of a constituent cascade model which includes charm flavour. The constituent diquark in an incident baryon has a tendency to get a large momentum fraction, resulting in considerable difference of subenergies for particle productions from quark-diquark and quark-antiquark chains in a meson-baryon collision. As a consequence, the leading particle effects on D meson productions are expected to be quite different in π+ and π- beams at present accelerator energies.

hep-ph↗