arXiv subjects

R. Mizuk

Publications and source records attributed to R. Mizuk.

At least 91 records · Page 5Linked to original sources

arXiv2015

Measurement of the branching fraction of B^+ -> tau^+ nu_tau decays with the semileptonic tagging method

We report a measurement of the branching fraction of B^+ -> tau^+ nu_tau decays using a data sample of 772 x 10^6 BBbar pairs, collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. We reconstruct the accompanying B meson in a semileptonic decay and detect the recoiling B candidate in the decay channel B^+ -> tau^+ nu_tau. We obtain a branching fraction of BR(B^+ -> tau^+ nu_tau) = [1.25 +- 0.28 (stat.) +- 0.27 (syst.)] x 10^-4. This result is in good agreement with previous measurements and the expectation from the calculation based on the Standard Model.

hep-ex↗

arXiv2015

Measurements of $B\rightarrow \bar{D} D_{s0} ^{+}(2317)$ decay rates and a search for isospin partners of the $D_{s0}^{+} (2317)$

We report improved measurements of the product branching fractions ${\mathcal B}(B^+\rightarrow\bar{D}^0 D_{s0}^{*+} (2317))\times{\mathcal B}( D_{s0} ^{*+}(2317)\rightarrow D_s^{+}π^0) =(8.0^{+1.3}_{-1.2} \pm 1.1 \pm 0.4)\times 10^{-4}$ and ${\mathcal B}(B^0\rightarrow D^- D_{s0} ^{*+}(2317))\times{\mathcal B}(D_{s0}^{*+}(2317)\rightarrow D_s^{+}π^0) =(10.2^{+1.3}_{-1.2} \pm 1.0 \pm 0.4)\times 10^{-4}$, where the first errors are statistical, the second are systematic and the third are from $D$ and $D_s$ branching fractions. In addition, we report negative results from a search for hypothesized neutral ($Z^0$) and doubly charged ($Z^{++}$) isospin partners of the $D_{s0}^{*+}(2317)$ and provide upper limits on the product branching fractions ${\mathcal B}(B^0 \rightarrow D^0 z^0)\times{\mathcal B}(z^0\rightarrow D_s^{+}π^-)$ and ${\mathcal B}(B^+\rightarrow D^- z^{++})\times{\mathcal B}(z^{++}\rightarrow D_s^{+}π^+)$ that are more than an order of magnitude smaller than theoretical expectations for the hypotheses that the $D_{s0} ^{*+}(2317)$ is a member of an isospin triplet. The analysis uses a 711 fb$^{-1}$ data sample containing 772 million $B\bar{B}$ meson pairs collected at the $Υ(4S)$ resonance in the Belle detector at the KEKB collider.

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arXiv2015

Study of $D^{**}$ production and light hadronic states in the $\bar{B}^0 \to D^{*+} ωπ^-$ decay

We report on the first observations of $\bar{B}^0 \to D_1(2430)^0 ω$, $\bar{B}^0 \to D_1(2420)^0 ω$ and $\bar{B}^0 \to D^*_2(2460)^0 ω$ decays. The $\bar{B}^0 \to D^{*+} ρ(1450)^-$ decay is also observed. The branching fraction measurements are based on $(771.6 \pm 10.6)\times 10^6$ $B\bar{B}$ events collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The fractions of longitudinal polarization of the $D^{**}$ states as well as partial wave fractions of the $D_1(2430)^0$ are obtained. We also set a $90\%$ confidence level upper limit for the product of branching fractions of $\mathcal{B}(\bar{B}^0 \to D^{*+} b_1(1235)^-) \times \mathcal{B}(b_1(1235)^- \to ωπ^-)$. The measurements show evidence of nontrivial final-state interaction phases for the $ρ$-like amplitudes.

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arXiv2015

Measurement of $e^+e^- \to γχ_{cJ}$ via initial state radiation at Belle

The process $e^+e^- \to γχ_{cJ}$ ($J$=1, 2) is studied via initial state radiation using 980 fb$^{-1}$ of data at and around the $Υ(nS)$ ($n$=1, 2, 3, 4, 5) resonances collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No significant signal is observed except from $ψ(2S)$ decays. Upper limits on the cross sections between $\sqrt{s}=3.80$ and $5.56~{\rm GeV}$ are determined at the 90% credibility level, which range from few pb to a few tens of pb. We also set upper limits on the decay rate of the vector charmonium [$ψ(4040$), $ψ(4160)$, and $ψ(4415)$] and charmoniumlike [$Y(4260)$, $Y(4360)$, and $Y(4660)$] states to $γχ_{cJ}$.

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arXiv2015

First observation of the hadronic transition $ Υ(4S) \to ηh_{b}(1P)$ and new measurement of the $h_b(1P)$ and $η_b(1S)$ parameters

Using a sample of $771.6 \times 10^{6}$ $Υ(4S)$ decays collected by the Belle experiment at the KEKB $e^+e^-$ collider, we observe for the first time the transition $Υ(4S) \to ηh_b(1P)$ with the branching fraction ${\cal B}[Υ(4S) \to ηh_b(1P)]= (2.18 \pm 0.11 \pm 0.18) \times 10^{-3}$ and we measure the $h_b(1P)$ mass $M_{h_{b}(1P)} = (9899.3 \pm 0.4 \pm 1.0)$ MeV/$c^{2}$, corresponding to the hyperfine splitting $ΔM_{\mathrm HF}(1P) = (0.6 \pm 0.4 \pm 1.0)$ MeV/$c^{2}$. Using the transition $h_b(1P) \to γη_b(1S)$, we measure the $η_b(1S)$ mass $M_{η_{b}(1S)} = (9400.7 \pm 1.7 \pm 1.6)$ MeV/$c^{2}$, corresponding to $ΔM_{\mathrm HF}(1S) = (59.6 \pm 1.7 \pm 1.6)$ MeV/$c^{2}$, the $η_b(1S)$ width $Γ_{η_{b}(1S)} = (8 ^{+6}_{-5} \pm 5)$ MeV/$c^{2}$ and the branching fraction ${\cal B}[h_b(1P) \to γη_b(1S)]= (56 \pm 8 \pm 4) \%$.

hep-ex↗

arXiv2015

Measurement of the direct $CP$ asymmetry in $\bar{B}\rightarrow X_{s+d}γ$ decays with a lepton tag

We report the measurement of the direct $CP$ asymmetry in the radiative $\bar{B}\rightarrow X_{s+d}γ$ decay using a data sample of $(772 \pm 11)\times 10^6$ $B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The $CP$ asymmetry is measured as a function of the photon energy threshold. For $E^{\rm{*}}_γ \geq 2.1~{\rm{GeV}}$, where $E^{\rm{*}}_γ$ is the photon energy in the center-of-mass frame, we obtain $\mathcal{A}_{CP}(\bar{B}\rightarrow X_{s+d}γ)= (2.2 \pm 3.9 \pm 0.9) \%$, consistent with the Standard Model prediction.

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arXiv2015

Testing Hadronic Interaction Models using a Highly Granular Silicon-Tungsten Calorimeter

A detailed study of hadronic interactions is presented using data recorded with the highly granular CALICE silicon-tungsten electromagnetic calorimeter. Approximately 350,000 selected negatively charged pion events at energies between 2 and 10 GeV have been studied. The predictions of several physics models available within the Geant4 simulation tool kit are compared to this data. A reasonable overall description of the data is observed; the Monte Carlo predictions are within 20% of the data, and for many observables much closer. The largest quantitative discrepancies are found in the longitudinal and transverse distributions of reconstructed energy.

physics.ins-det↗

arXiv2015

Search for B+ -> l+ nu gamma decays with hadronic tagging using the full Belle data sample

We search for the decay B+ -> l+ nu gamma with l+ = e+ or mu+ using the full Belle data set of 772 x 10^6 BBbar pairs, collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We reconstruct one B meson in a hadronic decay mode and search for the B+ -> l+ nu gamma decay in the remainder of the event. We observe no significant signal within the phase space of E_gamma^sig > 1 GeV and obtain upper limits of BR(B+ -> e+ nu gamma) < 6.1 x 10^-6, BR(B+ -> mu+ nu gamma) < 3.4 x 10^-6, and BR(B+ -> l+ nu gamma) < 3.5 x 10^-6 at 90 % credibility level.

hep-ex↗

arXiv2015

A scintillator based muon and KLong detector for the Belle II experiment

A new muon and K_Long detector based on scintillators will be used for the endcap and inner barrel regions in the Belle II experiment, currently under construction. The increased luminosity of the e+e- SuperKEKB collider entails challenging detector requirements. We demonstrate that relatively inexpensive polystyrene scintillator stips with wave length shifting fibers ensure a sufficient light yield at the Silcon PhotoMultiplier (SiPM) photodetector, are robust and provide improved physics performance for the Belle II experiment compared to its predecessor, Belle.

physics.ins-det↗

arXiv2015

Search for the decay $B^+\rightarrow\overline{K}{}^{0}K^{+}$ at Belle

We report a search for the rare charmless decay $B^+\rightarrow\overline{K}{}^{*0}K^{*+}$ using a data sample of $772\times10^6$ $B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No statistically significant signal is found and a 90% confidence-level upper limit is set on the decay branching fraction as $ \mathcal{B}(B^+\rightarrow\overline{K}{}^{*0}K^{*+}) <1.31\times 10^{-6}$.

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arXiv2014

Observation of a new charged charmoniumlike state in B -> J/psi K pi decays

We present the results of an amplitude analysis of anti-B0 -> J/psi K- pi+ decays. A new charged charmoniumlike state Zc(4200)+ decaying to J/psi pi+ is observed with a significance of 6.2 sigma. The mass and width of the Zc(4200)+ are 4196 +31-29 +17-13 MeV/c^2 and 370 +70-70 +70-132 MeV, respectively; the preferred assignment of the quantum numbers is J^P = 1^+. In addition, we find evidence for Zc(4430)+ -> J/psi pi+. The analysis is based on a 711 fb^-1 data sample collected by the Belle detector at the asymmetric-energy e+ e- collider KEKB.

hep-ex↗

arXiv2014

Search for $B_{s}^{0}\rightarrowγγ$ and a measurement of the branching fraction for $B_{s}^{0}\rightarrowϕγ$

We search for the decay $B_{s}^{0}\rightarrowγγ$ and measure the branching fraction for $B_{s}^{0}\rightarrowϕγ$ using 121.4~$\textrm{fb}^{-1}$ of data collected at the $Υ(\mathrm{5}S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. The $B_{s}^{0}\rightarrowϕγ$ branching fraction is measured to be $(3.6 \pm 0.5 (\mathrm{stat.}) \pm 0.3 (\mathrm{syst.}) \pm 0.6 (f_{s})) \times 10^{-5}$, where $f_{s}$ is the fraction of $B_{s}^{(*)}\bar{B}_{s}^{(*)}$ in $b\bar{b}$ events. Our result is in good agreement with the theoretical predictions as well as with a recent measurement from LHCb. We observe no statistically significant signal for the decay $B_{s}^{0}\rightarrowγγ$ and set a $90\%$ confidence-level upper limit on its branching fraction at $ 3.1 \times 10^{-6}$. This constitutes a significant improvement over the previous result.

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arXiv2014

Measurement of the $\bar{B} \rightarrow X_s γ$ Branching Fraction with a Sum of Exclusive Decays

We use 772$\times 10^6$ $B \bar{B}$ meson pairs collected at the $Υ(4S)$ resonance with the Belle detector to measure the branching fraction for $\bar{B} \rightarrow X_s γ$. Our measurement uses a sum-of-exclusives approach in which 38 of the hadronic final states with strangeness equal to $+1$, denoted by $X_s$, are reconstructed. The inclusive branching fraction for $M_{X_s}<$ 2.8 GeV/$c^2$, which corresponds to a minimum photon energy of 1.9 GeV, is measured to be ${\cal B}(\bar{B} \rightarrow X_s γ)=(3.51\pm0.17\pm0.33)\times10^{-4}$, where the first uncertainty is statistical and the second is systematic.

hep-ex↗

arXiv2014

Measurement of $B^0 \to D_s^- K^0_Sπ^+$ and $B^+ \to D_s^- K^+K^+$ branching fractions

We report a measurement of the $B^0$ and $B^+$ meson decays to the $D_s^-K^0_S π^+$ and $D_s^- K^+K^+$ final states, respectively, using $657 \times 10^{6} B\overline{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. Using the $D_s^-\to ϕπ^-$, $K^{*}(892)^0 K^-$ and $K^0_S K^-$ decay modes for the $D_s$ reconstruction, we measure the following branching fractions: ${\cal B}(B^0\to D_s^{-}K^0_Sπ^+)=[0.47 \pm 0.06 (\mathrm {stat}) \pm 0.05 (\mathrm {syst})]\times 10^{-4}$ and ${\cal B}(B^+\to D_s^-K^+K^+)= [0.93 \pm 0.22 (\mathrm {stat})\pm 0.10 (\mathrm {syst})]\times 10^{-5}$. We find the ratio of the branching fraction of $B^+\to D_s^-K^+K^+$ to that of the analogous Cabibbo favored $B^+\to D_s^-K^+π^+$ decay to be ${\cal R}_{\cal B} = 0.054 \pm 0.013 ({\rm stat}) \pm 0.006 ({\rm syst})$, which is consistent with the na\"ıve factorization model. We also observe a deviation from the three-body phase-space model for both studied decays.

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arXiv2014

Measurement of the inclusive semileptonic branching fraction $\mathcal{B}(B_s^0 \rightarrow X^- \ell^+ ν_\ell)$ at Belle

We report a measurement of the inclusive semileptonic $B_s^0$ branching fraction in a $121~fb^{-1}$ data sample collected near the $Υ(5S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^+ e^-$ collider. Events containing $B_s^0$ pairs are selected by reconstructing a tag side $D_s^+$ and identifying a signal side lepton $\ell^+$ ($\ell = e, μ$) that is required to have the same-sign charge to ensure that both originate from different $B_s^0$ mesons. The $B_s^0 \rightarrow X^- \ell^+ ν_\ell$ branching fraction is extracted from the ratio of the measured yields of $D_s^+$ mesons and $D_s^+ \ell^+$ pairs and the known production and branching fractions. The inclusive semileptonic branching fraction is measured to be $[9.6 \pm 0.4\text{(stat)} \pm 0.7\text{(syst)}]~\%$.

hep-ex↗

arXiv2014

Observation of $e^+e^- \to π^+ π^- π^0 χ_{bJ}$ and search for $X_b \to ωΥ(1S)$ at $\sqrt{s}\sim 10.867$ GeV

The $e^+e^- \to π^+ π^- π^0 χ_{bJ}$ ($J=0,~1,~2$) processes are studied using a 118~fb$^{-1}$ data sample collected at a center-of-mass energy of 10.867 GeV, in the $Υ(10860)$ energy range, with the Belle detector. The $π^+ π^- π^0 χ_{b1}$, $π^+π^-π^0χ_{b2}$, $ωχ_{b1}$ signals and the evidence of $ωχ_{b2}$ are observed for the first time and the cross sections are measured. No significant $π^+π^-π^0χ_{b0}$ or $ωχ_{b0}$ signal is observed and 90\% confidence level upper limits on the cross sections for these two processes are obtained. In the $π^+π^-π^0$ invariant mass spectrum, significant non-$ω$ signals are also observed. We search for the $X(3872)$-like state with a hidden $b\bar{b}$ component (named $X_b$) decaying into $ωΥ(1S)$; no significant signal is observed with a mass between $10.55$ and $10.65$ GeV/$c^2$.

hep-ex↗

arXiv2014

Observation of the decay $B^0 \to η' K^*(892)^0$

We report a search for charmless hadronic decays of neutral $B$ mesons to $η' K^{*}(892)^{0}$. The results are based on a 711fb$^{-1}$ data sample that contains $772\times 10^6 B\overline{B}$ pairs, collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^+e^-$ collider. We observe the decay for the first time with a significance of 5.0 standard deviations and obtain its branching fraction ${\cal B}[B^0\toη' K^{*}(892)^{0}]=[2.6\pm0.7{\rm (stat)}\pm0.2{\rm (syst)}]\times 10^{-6}$. We also measure the $CP$ violating asymmetry as ${\cal A}_{CP}[B^0\toη' K^{*}(892)^{0}]=-0.22\pm0.29{\rm (stat)}\pm0.07{\rm syst}$.

hep-ex↗

arXiv2014

Measurement of the Branching Fraction Br(Lambda_c+ -> p K- pi+)

We present the first model-independent measurement of the absolute branching fraction of the Lambda_c+ -> p K- pi+ decay using a data sample of 978 fb^-1 collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The number of Lambda_c+ baryons is determined by reconstructing the recoiling D(*)- anti-p pi+ system in events of the type e+e- -> D(*)- anti-p pi+ Lambda_c+. The branching fraction is measured to be Br(Lambda_c+ -> p K- pi+) = (6.84 +- 0.24^{+0.21}_{-0.27})%, where the first and second uncertainties are statistical and systematic, respectively.

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