arXiv subjects

K. Inami

Publications and source records attributed to K. Inami.

At least 127 records · Page 7Linked to original sources

arXiv2020

Update of inclusive cross sections of single and pairs of identified light charged hadrons

We report new measurements of the production cross sections of pairs of charged pions and kaons as a function of their fractional energies using various fractional-energy definitions. Two different fractional-energy definitions were used and compared to the conventional fractional-energy definition reported previously. The new variables aim at either identifying dihadron cross sections in terms of single-hadron fragmentation functions, or to provide a means of characterizing the transverse momentum created in the fragmentation process. The results were obtained applying the updated initial-state radiation correction used in other recent Belle publications on light-hadron production cross sections. In addition, production cross sections of single charged pions, kaons, and protons were also updated using this initial-state radiation correction. The cross sections are obtained from a $558\,{\rm fb}^{-1}$ data sample collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider.

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arXiv2019

Measurements of the Branching Fractions ${\cal B}(B^{-} \to \barΛ_{c}^{-} Ξ_{c}^{'0})$, ${\cal B}(B^{-} \to \barΛ_{c}^{-} Ξ_{c}(2645)^{0})$ and ${\cal B}(B^{-} \to \barΛ_{c}^{-} Ξ_{c}(2790)^{0}) $

Using the data sample of 711 fb$^{-1}$ of $Υ(4S)$ on-resonance data taken by the Belle detector at the KEKB asymmetric-energy electron-positron collider, we present the first measurements of branching fractions of the decays $B^{-} \to \barΛ_{c}^{-} Ξ_{c}^{'0}$, $B^{-} \to \barΛ_{c}^{-} Ξ_{c}(2645)^{0}$, and $B^{-} \to \barΛ_{c}^{-} Ξ_{c}(2790)^{0} $. The signal yields for these decays are extracted from the recoil mass spectrum of the system recoiling against $\barΛ_{c}^{-}$ baryons in selected $B^-$ candidates. The branching fraction of $B^{-} \to \barΛ_{c}^{-} Ξ_{c}(2790)^{0}$ is measured to be $ (1.1 \pm 0.4 \pm 0.2)\times 10^{-3}$, where the first uncertainty is statistical and the second systematic. The 90\% credibility level upper limits on ${\cal B}(B^{-} \to \barΛ_{c}^{-} Ξ_{c}^{'0})$ and ${\cal B}(B^{-} \to \barΛ_{c}^{-} Ξ_{c}(2645)^{0})$ are determined to be $6.5\times 10^{-4}$ and $7.9\times 10^{-4}$, respectively.

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arXiv2019

Study of $B \to p {\bar p} ππ$

Using a data sample of $772 \times 10^6$ BB pairs collected on the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider, we report the observations of $B^0\to p{\bar p}π^+π^-$ and $B^+ \to p{\bar p}π^+π^0$. We measure a decay branching fraction of $(0.83 \pm 0.17 \pm 0.17) \times 10^-6$ in $B^0\to p{\bar p}π^+π^-$ for $M_{π^+π^-} < 1.22 GeV/c^2$ with a significance of 5.5 standard deviations. The contribution from $B0 \to p{\bar p}K^0$ is excluded. We measure a decay branching fraction of $(4.58 \pm 1.17 \pm 0.67) \times 10^-6$ for $B^+ \to p{\bar p}π^+π^0$ with $M_{π^+π^0} < 1.3 GeV/c^2$ with a significance of 5.4 standard deviations. We study the difference of the $M_{p{\bar p}}$ distributions in $B^0\to p{\bar p}π^+π^-$ and $B^+ \to p{\bar p}π^+π^0$.

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arXiv2019

Search for $B^+ \to μ^+\, ν_μ$ and $B^+ \to μ^+\, N$ with inclusive tagging

We report the result for a search for the leptonic decay of $B^+ \to μ^+ \, ν_μ$ using the full Belle data set of 711 fb${}^{-1}$ of integrated luminosity at the $Υ(4S)$ resonance. In the Standard Model leptonic $B$-meson decays are helicity and CKM suppressed. To maximize sensitivity an inclusive tagging approach is used to reconstruct the second $B$ meson produced in the collision. The directional information from this second $B$ meson is used to boost the observed $μ$ into the signal $B$ meson rest-frame, in which the $μ$ has a monochromatic momentum spectrum. Though its momentum is smeared by the experimental resolution, this technique improves the analysis sensitivity considerably. Analyzing the $μ$ momentum spectrum in this frame we find $\mathcal{B}(B^+ \to μ^+ \, ν_μ) = \left( 5.3 \pm 2.0 \pm 0.9 \right) \times 10^{-7}$ with a one-sided significance of 2.8 standard deviations over the background-only hypothesis. This translates to a frequentist upper limit of $\mathcal{B}(B^+ \to μ^+ \, ν_μ) < 8.6 \times 10^{-7}$ at 90% CL. The experimental spectrum is then used to search for a massive sterile neutrino, $B^+ \to μ^+ \, N$, but no evidence is observed for a sterile neutrino with a mass in a range of 0 - 1.5 GeV. The determined $B^+ \to μ^+ \, ν_μ$ branching fraction limit is further used to constrain the mass and coupling space of the type II and type III two-Higgs-doublet models.

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arXiv2019

Observation of a vector charmoniumlike state in $e^+e^- \to D^+_sD_{s1}(2536)^-+c.c.$

Using a data sample of 921.9 fb$^{-1}$ collected with the Belle detector, we study the process of $e^+e^-\to D^+_sD_{s1}(2536)^-+c.c.$ via initial-state radiation. We report the first observation of a vector charmoniumlike state decaying to $D^+_sD_{s1}(2536)^-+c.c.$ with a significance of 5.9$σ$, including the systematic uncertainties. The measured mass and width are $(4625.9^{+6.2}_{-6.0}({\rm stat.})\pm0.4({\rm syst.}))~{\rm MeV}/c^{2}$ and $(49.8^{+13.9}_{-11.5}({\rm stat.})\pm4.0({\rm syst.}))~{\rm MeV}$, respectively. The product of the $e^+e^-\to D^+_sD_{s1}(2536)^-+c.c.$ cross section and the branching fraction of $D_{s1}(2536)^-\to{\bar D}^{*0}K^-$ is measured from the $D_s \bar{D}_{s1}(2536)$ threshold to 5.59~GeV.

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arXiv2019

Observation of the radiative decays of $Υ(1S)$ to $χ_{c1}$

We report the first observation of the radiative decay of the $Υ(1S)$ into a charmonium state. The statistical significance of the observed signal of $Υ(1S) \to γχ_{c1}$ is 6.3 standard deviations including systematics. The branching fraction is calculated to be Br($Υ(1S) \to γχ_{c1}$) = (4.7^{+2.4}_{-1.8} (stat) ^{+0.4}_{-0.5} (sys)) * 10^{-5}. We also searched for $Υ(1S)$ radiative decays into $χ_{c0,2}$ and $η_c(1S,2S)$ and set upper limits on their branching fractions. These results are obtained from a 24.9 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider at a center-of-mass energy equal to the $Υ(2S)$ mass using $Υ(1S)$ tagging by the $Υ(2S) \to Υ(1S) π^+π^-$ transitions.

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arXiv2019

Measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$ with a semileptonic tagging method

The experimental results on the ratios of branching fractions $\mathcal{R}(D) = {\cal B}(\bar{B} \to D τ^- \barν_τ)/{\cal B}(\bar{B} \to D \ell^- \barν_{\ell})$ and $\mathcal{R}(D^*) = {\cal B}(\bar{B} \to D^* τ^- \barν_τ)/{\cal B}(\bar{B} \to D^* \ell^- \barν_{\ell})$, where $\ell$ denotes an electron or a muon, show a long-standing discrepancy with the Standard Model predictions, and might hint to a violation of lepton flavor universality. We report a new simultaneous measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$, based on a data sample containing $772 \times 10^6$ $B\bar{B}$ events recorded at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. In this analysis the tag-side $B$ meson is reconstructed in a semileptonic decay mode and the signal-side $τ$ is reconstructed in a purely leptonic decay. The measured values are $\mathcal{R}(D)= 0.307 \pm 0.037 \pm 0.016$ and $\mathcal{R}(D^*) = 0.283 \pm 0.018 \pm 0.014$, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within $0.2$, $1.1$ and $0.8$ standard deviations for $\mathcal{R}(D)$, $\mathcal{R}(D^*)$ and their combination, respectively. This work constitutes the most precise measurements of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$ performed to date as well as the first result for $\mathcal{R}(D)$ based on a semileptonic tagging method.

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arXiv2019

Observation of a new structure near 10.75 GeV in the energy dependence of the $e^+e^-\toΥ(nS)π^+π^-$ ($n=1,2,3$) cross sections

We report a new measurement of the $e^+e^-\toΥ(nS)π^+π^-$ ($n=1,2,3$) cross sections at energies from 10.52 to 11.02 GeV using data collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We observe a new structure in the energy dependence of the cross sections; if described by a Breit-Wigner function its mass and width are found to be $M=(10752.7\pm5.9\,^{+0.7}_{-1.1})\,$MeV/$c^2$ and $Γ=(35.5^{+17.6}_{-11.3}\,^{+3.9}_{-3.3})\,$MeV, where the first error is statistical and the second is systematic. The global significance of the new structure including systematic uncertainty is 5.2 standard deviations. We also find evidence for the $e^+e^-\toΥ(1S)π^+π^-$ process at the energy 10.52 GeV, which is below the $B\bar{B}$ threshold.

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arXiv2019

First measurement of the CKM angle $ϕ_3$ with $B^{\pm}\to D(K_{\rm S}^0π^+π^-π^0)K^{\pm}$ decays

We present the first model-independent measurement of the CKM unitarity triangle angle $ϕ_3$ using $B^{\pm}\to D(K_{\rm S}^0π^+π^-π^0)K^{\pm}$ decays, where $D$ indicates either a $D^{0}$ or $\overline{D}^{0}$ meson. Measurements of the strong-phase difference of the $D \to K_{\rm S}^0π^+π^-π^0$ amplitude obtained from CLEO-c data are used as input. This analysis is based on the full Belle data set of $772\times 10^{6}$ $B\overline{B}$ events collected at the $Υ(4S)$ resonance. We obtain $ϕ_3 = (5.7~^{+10.2}_{-8.8} \pm 3.5 \pm 5.7)^{\circ}$ and the suppressed amplitude ratio $r_{B} = 0.323 \pm 0.147 \pm 0.023 \pm 0.051$. Here the first uncertainty is statistical, the second is the experimental systematic, and the third is due to the precision of the strong-phase parameters measured from CLEO-c data. The 95% confidence interval on $ϕ_3$ is $(-29.7,~109.5)^{\circ}$, which is consistent with the current world average.

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arXiv2019

Observation of $ τ^- \rightarrow π^- ν_τ e^+ e^-$ and search for $τ^- \rightarrow π^- ν_τ μ^+ μ^-$

We present the first measurements of branching fractions of rare tau-lepton decays, $τ^- \rightarrow π^- ν_τ \ell^+ \ell^-$ ($\ell = e$ or $μ$), 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 $τ^- \rightarrow π^- ν_τe^+ e^-$ decay is observed for the first time with 7.0$σ$ 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 $M_{πe e}>1.05$ GeV/$c^2$ is measured to be $\mathcal{B}(τ^-\rightarrow π^- ν_τe^+ e^-)[M_{π^- e^+ e^-}>1.05~{\rm GeV}/c^2] = (5.90 \pm 0.53 \pm 0.85 \pm 0.11) \times 10^{-6}$, 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 $\mathcal{B}_{A}(τ^-\rightarrow π^- ν_τe^+ e^-) = (1.46 \pm 0.13 \pm 0.21) \times 10^{-5}$ to $\mathcal{B}_{V}(τ^-\rightarrow π^- ν_τe^+ e^-) = (3.01 \pm 0.27 \pm 0.43) \times 10^{-5}$, respectively. An upper limit is set on the branching fraction of the $τ^- \rightarrow π^- ν_τμ^+ μ^-$ decay, $\mathcal{B}(τ^-\rightarrow π^- ν_τμ^+ μ^-) < 1.14 \times 10^{-5}$, at the 90% confidence level.

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arXiv2019

Azimuthal asymmetries of back-to-back $π^\pm-(π^0,η,π^\pm)$ pairs in $e^+e^-$ annihilation

This work reports the first observation of azimuthal asymmetries around the thrust axis in $e^+e^-$ annihilation of pairs of back-to-back charged pions in one hemisphere, and $π^0$ and $η$ mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The $π^0$ and $η$ asymmetries rise with the relative momentum $z$ of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function $H_1^{\perp}$ and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the $η$ final states will provide additional information on the flavor structure of $H_1^{\perp}$. This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4~fb$^{-1}$ collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.

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arXiv2019

First measurements of absolute branching fractions of the $Ξ_c^+$ baryon at Belle

We present the first measurements of the absolute branching fractions of $Ξ_c^+$ decays into $Ξ^- π^+ π^+$ and $p K^- π^+$ final states. Our analysis is based on a data set of $(772\pm 11)\times 10^{6}$ $B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. We measure the absolute branching fraction of $\bar{B}^{0} \to \barΛ_{c}^{-} Ξ_{c}^{+}$ with the $Ξ_c^+$ recoiling against $\barΛ_c^-$ in $\bar{B}^0$ decays resulting in ${\cal B}(\bar{B}^{0} \to \barΛ_{c}^{-} Ξ_{c}^{+}) = [1.16 \pm 0.42(\rm stat.) \pm 0.15(\rm syst.)] \times 10^{-3}$. We then measure the product branching fractions ${\cal B}(\bar{B}^{0} \to \barΛ_c^- Ξ_c^+){\cal B}(Ξ_c^+ \to Ξ^- π^+ π^+)$ and ${\cal B}(\bar{B}^{0} \to \barΛ_c^- Ξ_c^+){\cal B}(Ξ_c^+ \to p K^- π^+)$. Dividing these product branching fractions by $\bar{B}^{0} \to \barΛ_{c}^{-} Ξ_{c}^{+}$ yields: ${\cal B}(Ξ_c^+ \to Ξ^- π^+ π^+) = [2.86 \pm 1.21(\rm stat.) \pm 0.38(\rm syst.)]\%$ and ${\cal B}(Ξ_c^+ \to p K^- π^+)=[0.45 \pm 0.21(\rm stat.) \pm 0.07(\rm syst.)]\%$. Our result for ${\cal B}(Ξ_c^+ \to Ξ^- π^+ π^+)$ can be combined with $Ξ_c^+$ branching fractions measured relative to $Ξ_c^+ \to Ξ^- π^+ π^+$ to set the absolute scale for many $Ξ_c^+$ branching fractions.

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arXiv2019

Search for $B^0 \to X(3872) γ$

We report the results of a search for the decay $B^0 \to X(3872)(\to J/ψπ^+ π^-) γ$. The analysis is performed on a data sample corresponding to an integrated luminosity of $711\,{\rm fb}^{-1}$ and containing $772 \times 10^6 B\bar{B}$ pairs, collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider running at the $Υ(4S)$ resonance energy. We find no evidence for a signal and place an upper limit of $\mathcal{B}(B^0 \to X(3872)γ)\times \mathcal{B}(X(3872) \to J/ψπ^+ π^-) < 5.1 \times 10^{-7}$ at 90% confidence level.

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arXiv2019

Evidence for $B^+ \rightarrow h_c K^+$ and observation of $η_c(2S) \to p \bar{p} π^+ π^-$

A search for the decays $B^+ \rightarrow h_c K^+$ and $B^0 \rightarrow h_c K_S^0$ is performed. Evidence for the decay $B^+ \rightarrow h_c K^+$ is found; its significance is $4.8σ$. No evidence is found for $B^0 \rightarrow h_c K_S^0$. The branching fraction for $B^+ \rightarrow h_c K^+$ is measured to be $(3.7^{+1.0}_{-0.9}{}^{+0.8}_{-0.8}) \times 10^{-5}$; the upper limit for the $B^0 \rightarrow h_c K_S^0$ branching fraction is $1.4 \times 10^{-5}$ at $90\%$ C.L. In addition, a study of the $p \bar{p} π^+ π^-$ invariant mass distribution in the channel $B^+ \to (p \bar{p} π^+ π^-) K^+$ results in the first observation of the decay $η_c(2S) \to p \bar{p} π^+ π^-$ with $12.1σ$ significance. The analysis is based on the 711 $\mathrm{fb}^{-1}$ data sample collected by the Belle detector at the asymmetric-energy $e^+ e^-$ collider KEKB at the $Υ(4S)$ resonance.

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arXiv2019

Search for $Ω(2012)\to KΞ(1530) \to KπΞ$ at Belle

Using data samples of $e^+e^-$ collisions collected at the $Υ(1S)$, $Υ(2S)$, and $Υ(3S)$ resonances with the Belle detector, we search for the three-body decay of the $Ω(2012)$ baryon to $KπΞ$. This decay is predicted to dominate for models describing the $Ω(2012)$ as a $KΞ(1530)$ molecule. No significant $Ω(2012)$ signals are observed in the studied channels, and 90\% credibility level upper limits on the ratios of the branching fractions relative to $K Ξ$ decay modes are obtained.

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arXiv2019

Search for $X(3872)$ and $X(3915)$ decay into $χ_{c1} π^0$ in $B$ decays at Belle

We report a search for $X(3872)$ and $X(3915)$ in $B^+ \to χ_{c1} π^0 K^+$ decays. We set an upper limit of $\mathcal{B}(B^+ \to X(3872) K^+) \times \mathcal{B}(X(3872) \to χ_{c1} π^0)$ $ < 8.1 \times 10^{-6}$ and $\mathcal{B}(B^+ \to X(3915) K^+) \times \mathcal{B}(X(3915) \to χ_{c1} π^0)$ $ < 3.8 \times 10^{-5}$ at 90\% confidence level. We also measure $\mathcal{B}(X(3872) \to χ_{c1} π^0)/\mathcal{B}(X(3872) \to J/ψπ^+ π^-) < 0.97$ at 90\% confidence level. The results reported here are obtained from $772 \times 10^{6}$ $B\overline{B}$ events collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider.

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arXiv2019

Observation of $e^+e^-\toπ^+π^-π^0χ_{b1,2}(1P)$ and search for $e^+e^-\toϕχ_{b1,2}(1P)$ at $\sqrt{s}=$10.96---11.05 GeV

We report searches for the processes $e^+e^-\toπ^+π^-π^0χ_{bJ}$ and $e^+e^-\toϕχ_{bJ}$ (J=1,2) based on data samples collected by the Belle experiment at the KEKB collider. We report the first observation of the process $e^+e^-\to (π^+π^-π^0)_{\rm non-ω}χ_{b1}$ and first evidence for $e^+e^-\toωχ_{bJ}$ in the vicinity of the $Υ(11020)$ resonance, with center-of-mass energies from 10.96 to 11.05~GeV. The significances for $(π^+π^-π^0)_{\rm non-ω}χ_{b1}$ and $ωχ_{bJ}$ are greater than $5.3σ$ and $4.0σ$, respectively. We also investigate the energy dependence of the $e^+e^-\toπ^+π^-π^0χ_{bJ}$ cross section, but we cannot determine whether the contributions are from the $Υ(10860)$ and $Υ(11020)$ resonances or non-resonant continuum processes. The signals for $e^+e^-\to ϕχ_{bJ}$ are not significant, and the upper limits of the Born cross sections at the 90\% confidence level are $0.7$ and $1.0$~pb for $e^+e^-\to ϕχ_{b1}$ and $ϕχ_{b2}$, respectively, for center-of-mass energies from 10.96 to 11.05~GeV.

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arXiv2019

Measurement of the CKM Matrix Element $|V_{cb}|$ from $B^{0} \to D^{*-} \ell^+ ν_\ell$ at Belle

We present a new measurement of the CKM matrix element $|V_{cb}|$ from $B^{0} \to D^{*-} \ell^+ ν_\ell$ decays, reconstructed with the full Belle data set of $711 \, \rm fb^{-1}$ integrated luminosity. Two form factor parameterizations, originally conceived by the Caprini-Lellouch-Neubert (CLN) and the Boyd, Grinstein and Lebed (BGL) groups, are used to extract the product $\mathcal{F}(1)η_{\rm EW}|V_{cb}|$ and the decay form factors, where $\mathcal{F}(1)$ is the normalization factor and $η_{\rm EW}$ is a small electroweak correction. In the CLN parameterization we find $\mathcal{F}(1)η_{\rm EW}|V_{cb}| = (35.06 \pm 0.15 \pm 0.56) \times 10^{-3}$, $ρ^{2}=1.106 \pm 0.031 \pm 0.007$, $R_{1}(1)=1.229 \pm 0.028 \pm 0.009$, $R_{2}(1)=0.852 \pm 0.021 \pm 0.006$. For the BGL parameterization we obtain $\mathcal{F}(1)η_{\rm EW}|V_{cb}|= (34.93 \pm 0.23 \pm 0.59)\times 10^{-3}$, which is consistent with the World Average when correcting for $\mathcal{F}(1)η_{\rm EW}$. The branching fraction of $B^{0} \to D^{*-} \ell^+ ν_\ell$ is measured to be $\mathcal{B}(B^{0}\rightarrow D^{*-}\ell^{+}ν_{\ell}) = (4.90 \pm 0.02 \pm 0.16)\%$. We also present a new test of lepton flavor universality violation in semileptonic $B$ decays, $\frac{{\cal B }(B^0 \to D^{*-} e^+ ν)}{{\cal B }(B^0 \to D^{*-} μ^+ ν)} = 1.01 \pm 0.01 \pm 0.03~$. The errors correspond to the statistical and systematic uncertainties respectively. This is the most precise measurement of $\mathcal{F}(1)η_{\rm EW}|V_{cb}|$ and form factors to date and the first experimental study of the BGL form factor parameterization in an experimental measurement.

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