arXiv subjects

K. Arinstein

Publications and source records attributed to K. Arinstein.

At least 37 records · Page 2Linked to original sources

arXiv2016

Evidence for the decay $B^{0}\to ηη$

We report a search for $B^{0}\to ηη$ with a data sample corresponding to an integrated luminosity of $698 \,{\rm fb}^{-1}$ containing $753 \times 10^{6}$ $B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. The branching fraction is measured to be $\mathcal{B}(B^{0} \to ηη) = (7.6^{+2.7 +1.4}_{-2.3 -1.6}) \times 10^{-7}$ at the level of 3.3 standard deviations above zero, which provides the first evidence for the decay $B^{0} \to ηη$.

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arXiv2016

Measurement of the $τ$ lepton polarization in the decay ${\bar B} \rightarrow D^* τ^- {\bar ν_τ}$

We report the first measurement of the $τ$ lepton polarization in the decay ${\bar B} \rightarrow D^* τ^- {\barν_τ}$ as well as a new measurement of the ratio of the branching fractions $R(D^{*}) = \mathcal{B}({\bar B} \rightarrow D^* τ^- {\barν_τ}) / \mathcal{B}({\bar B} \rightarrow D^* \ell^- {\barν_{\ell}})$, where $\ell^-$ denotes an electron or a muon, with the decays $τ^- \rightarrow π^- ν_τ$ and $τ^- \rightarrow ρ^- ν_τ$. We use the full data sample of $772 \times 10^6$ $B{\bar B}$ pairs accumulated with the Belle detector at the KEKB electron-positron collider. Our preliminary results, $R(D^*) = 0.276 \pm 0.034{\rm (stat.)} ^{+0.029} _{-0.026}{\rm (syst.)}$ and $P_τ = -0.44 \pm 0.47 {\rm (stat.)} ^{+0.20} _{-0.17} {\rm (syst.)}$, are consistent with the theoretical predictions of the Standard Model within $0.6$ standard deviation.

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arXiv2016

Measurement of $e^+e^- \to π^+π^-ψ(2S)$ via Initial State Radiation at Belle

We report measurement of the cross section of $e^+e^-\to π^+π^-ψ(2S)$ between 4.0 and $5.5 {\rm GeV}$, based on an analysis of initial state radiation events in a $980 \rm fb^{-1}$ data sample recorded with the Belle detector. The properties of the $Y(4360)$ and $Y(4660)$ states are determined. Fitting the mass spectrum of $π^+π^-ψ(2S)$ with two coherent Breit-Wigner functions, we find two solutions with identical mass and width but different couplings to electron-positron pairs: $M_{Y(4360)} = (4347\pm 6\pm 3) {\rm MeV}/c^2$, $Γ_{Y(4360)} = (103\pm 9\pm 5) {\rm MeV}$, $M_{Y(4660)} = (4652\pm10\pm 8) {\rm MeV}/c^2$, $Γ_{Y(4660)} = (68\pm 11\pm 1) \rm MeV$; and ${\cal{B}}[Y(4360)\to π^+π^-ψ(2S)]\cdot Γ_{Y(4360)}^{e^+e^-} = (10.9\pm 0.6\pm 0.7) \rm eV$ and ${\cal{B}}[Y(4660)\to π^+π^-ψ(2S)]\cdot Γ_{Y(4660)}^{e^+e^-} = (8.1\pm 1.1\pm 0.5) \rm eV$ for one solution; or ${\cal{B}}[Y(4360)\to π^+π^-ψ(2S)]\cdot Γ_{Y(4360)}^{e^+e^-} = (9.2\pm 0.6\pm 0.6) \rm eV$ and ${\cal{B}}[Y(4660)\to π^+π^-ψ(2S)]\cdot Γ_{Y(4660)}^{e^+e^-} = (2.0\pm 0.3\pm 0.2) \rm eV$ for the other. Here, the first errors are statistical and the second systematic. Evidence for a charged charmoniumlike structure at $4.05 {\rm GeV}/c^2$ is observed in the $π^{\pm}ψ(2S)$ intermediate state in the $Y(4360)$ decays.

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arXiv2016

Study of χ_{bJ}(1P) Properties in the Radiative Υ(2S) Decays

We report a study of radiative decays of χ_{bJ}(1P)(J=0,1,2) mesons into 74 hadronic final states comprising charged and neutral pions, kaons, protons; out of these, 41 modes are observed with at least 5 standard deviation significance. Our measurements not only improve the previous measurements by the CLEO Collaboration but also lead to first observations in many new modes. The large sample allows us to probe the total decay width of the χ_{b0}(1P). In the absence of a statistically significant result, a 90% confidence-level upper limit is set on the width at Γ_{total}< 2.4 MeV. Our results are based on 24.7 fb^{-1} of e+e- collision data recorded by the Belle detector at the Υ(2S) resonance, corresponding to (157.8\pm3.6)\times10^6 Υ(2S) decays.

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arXiv2016

Angular analysis of $B^0 \to K^\ast(892)^0 \ell^+ \ell^-$

We present a measurement of angular observables, $P_4'$, $P_5'$, $P_6'$, $P_8'$, in the decay $B^0 \to K^\ast(892)^0 \ell^+ \ell^-$, where $\ell^+\ell^-$ is either $e^+e^-$ or $μ^+μ^-$. The analysis is performed on a data sample corresponding to an integrated luminosity of $711~\mathrm{fb}^{-1}$ containing $772\times 10^{6}$ $B\bar B$ pairs, collected at the $Υ(4S)$ resonance with the Belle detector at the asymmetric-energy $e^+e^-$ collider KEKB. Four angular observables, $P_{4,5,6,8}'$ are extracted in five bins of the invariant mass squared of the lepton system, $q^2$. We compare our results for $P_{4,5,6,8}'$ with Standard Model predictions including the $q^2$ region in which the LHCb collaboration reported the so-called $P_5'$ anomaly.

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arXiv2016

Inclusive and exclusive measurements of $B$ decays to $χ_{c1}$ and $χ_{c2}$ at Belle

We report inclusive and exclusive measurements for $χ_{c1}$ and $χ_{c2}$ production in $B$ decays. We measure $\mathcal{B}(B \to χ_{c1} X)$= $(3.03 \pm 0.05(\mbox{stat}) \pm 0.24(\mbox{syst})) \times 10^{-3}$ and $\mathcal{B}(B \to χ_{c2} X)$= $(0.70 \pm 0.06(\mbox{stat}) \pm 0.10(\mbox{syst})) \times 10^{-3}$. For the first time, $χ_{c2}$ production in exclusive $B$ decays in the modes $B^0 \to χ_{c2}π^- K^+$ and $B^+ \to χ_{c2} π^+ π^- K^+$ has been observed, along with first evidence for the $B^+ \to χ_{c2} π^+ K_S^0$ decay mode. For $χ_{c1}$ production, we report the first observation in the $B^+ \to χ_{c1} π^+ π^- K^+$, $B^0 \to χ_{c1} π^+ π^- K_S^0$ and $B^0 \to χ_{c1} π^0 π^- K^+$ decay modes. Using these decay modes, we observe a difference in the production mechanism of $χ_{c2}$ in comparison to $χ_{c1}$ in $B$ decays. In addition, we report searches for $X(3872)$ and $χ_{c1}(2P)$ in the $B^+ \to (χ_{c1} π^+ π^-) K^+$ decay mode. The reported results use $772 \times 10^{6}$ $B\overline{B}$ events collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider.

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arXiv2016

Measurement of the branching ratio of $\bar{B}^0 \rightarrow D^{+} τ^- \barν_τ$ relative to $\bar{B}^0 \rightarrow D^{+} \ell^- \barν_{\ell}$ decays with a semileptonic tagging method

We report a measurement of ratio ${\cal R}(D^*) = {\cal B}(\bar{B}^0 \rightarrow D^{*+} τ^- \barν_τ)/{\cal B}(\bar{B}^0 \rightarrow D^{*+} \ell^- \barν_{\ell})$, where $\ell$ denotes an electron or a muon. The results are based on a data sample containing $772\times10^6$ $B\bar{B}$ pairs recorded at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. We select a sample of $B^0 \bar{B}^0$ pairs by reconstructing both $B$ mesons in semileptonic decays to $D^{*\mp} \ell^{\pm}$. We measure ${\cal R}(D^*)= 0.302 \pm 0.030({\rm stat)} \pm 0.011({\rm syst)}$, which is within $1.6 σ$ of the Standard Model theoretical expectation, where $σ$ is the standard deviation including systematic uncertainties.

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arXiv2016

Search for $B^0 \to π^- τ^+ ν_τ$ with hadronic tagging at Belle

We search for the process $B^0 \to π^- τ^+ ν_τ$ using the full Belle data set of $711\,{\rm fb}^{-1}$, corresponding to $772 \times 10^6 B\bar{B}$ pairs, collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We reconstruct one $B$ meson in a hadronic decay and search for the $B^0 \to π^- τ^+ ν_τ$ process in the remainder of the event. No significant signal is observed and an upper limit of $\mathcal{B}(B^0 \to π^- τ^+ ν_τ) < 2.5 \times 10^{-4}$ is obtained at the $90\%$ confidence level.

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arXiv2015

Measurement of the branching ratio of $\bar{B} \to D^{(\ast)} τ^- \barν_τ$ relative to $\bar{B} \to D^{(\ast)} \ell^- \barν_\ell$ decays with hadronic tagging at Belle

We report a measurement of the branching fraction ratios R(D(*)) of Bbar -> D(*) tau- nubar_tau relative to Bbar -> D()* l- nubar_l (where l = e or mu) using the full Belle 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. The measured values are R(D)= 0.375 +- 0.064(stat.) +- 0.026(syst.) and R(D*) = 0.293 +- 0.038(stat.) +- 0.015(syst.). The analysis uses hadronic reconstruction of the tag-side B meson and purely leptonic tau decays. The results are consistent with earlier measurements and do not show a significant deviation from the standard model prediction.

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arXiv2015

Observation of $X(3872)$ in $B \to X(3872) Kπ$ decays

We report the first observation of $B^0 \to X(3872) (K^{+}π^{-})$ and evidence for $B^+ \to X(3872) (K^{0}π^{+})$. We measure the product of branching fractions for the former to be ${\cal B}(B^0 \to X(3872) (K^+ π^-)) \times {\cal B}(X(3872) \to J/ψπ^+ π^-) = (7.9 \pm 1.3(\mbox{stat.})\pm 0.4(\mbox{syst.})) \times 10^{-6}$ and find that $B^{0}\to X(3872) K^{*}(892)^{0}$ does not dominate the $B^{0}\to X(3872)K^{+}π^{-}$ decay mode. We also measure ${\cal B}(B^+ \to X(3872) (K^0 π^+)) \times {\cal B}(X(3872) \to J/ψπ^+ π^-) = (10.6 \pm 3.0(\mbox{stat.}) \pm 0.9(\mbox{syst.})) \times 10^{-6}$. This study is based on the full data sample of 711~fb$^{-1}$ ($772\times 10^6 B\bar B$ pairs) collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB collider.

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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.

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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

First Observation of CP Violation in B0->D(*)CP h0 Decays by a Combined Time-Dependent Analysis of BaBar and Belle Data

We report a measurement of the time-dependent CP asymmetry of B0->D(*)CP h0 decays, where the light neutral hadron h0 is a pi0, eta or omega meson, and the neutral D meson is reconstructed in the CP eigenstates K+ K-, K0S pi0 or K0S omega. The measurement is performed combining the final data samples collected at the Y(4S) resonance by the BaBar and Belle experiments at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain ( 471 +/- 3 ) x 10^6 BB pairs recorded by the BaBar detector and ( 772 +/- 11 ) x 10^6, BB pairs recorded by the Belle detector. We measure the CP asymmetry parameters -eta_f S = +0.66 +/- 0.10 (stat.) +/- 0.06 (syst.) and C = -0.02 +/- 0.07 (stat.) +/- 0.03 (syst.). These results correspond to the first observation of CP violation in B0->D(*)CP h0 decays. The hypothesis of no mixing-induced CP violation is excluded in these decays at the level of 5.4 standard deviations.

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arXiv2015

Evidence for the decay B0->eta pi^0

We report a search for the charmless hadronic decay $B^0\toηπ^0$ with a data sample corresponding to an integrated luminosity of 694 $\rm fb^{-1}$ containing $753\times10^6$ $B\bar{B}$ pairs. The data were collected by the Belle experiment running on the $Υ(4S)$ resonance at the KEKB $e^+e^-$ collider. We measure a branching fraction $\mathcal{B}(B^0\toηπ^0)=(4.1^{+1.7+0.5}_{-1.5-0.7})\times 10^{-7}$, where the first uncertainty is statistical and the second is systematic. Our measurement gives an upper limit of $\mathcal{B}(B^0\toηπ^0)<6.5\times 10^{-7}$ at 90\% confidence level. The signal has a significance of $3.0$ standard deviations and constitutes the first evidence for this decay mode.

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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 ${\cal B}[h_b(1P) \to γη_b(1S)]= (56 \pm 8 \pm 4) \%$.

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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

Measurement of Azimuthal Modulations in the Cross-Section of Di-Pion Pairs in Di-Jet Production from Electron-Positron Annihilation

We present an extraction of azimuthal correlations between two pairs of charged pions detected in opposite jets from electron-positron annihilation. These correlations may arise from the dependence of the di-pion fragmentation on the polarization of the parent quark in the process $e^+e^- \rightarrow q \bar{q}$. Due to the correlation of the quark polarizations, the cross-section of di-pion pair production, in which the pion pairs are detected in opposite jets in a dijet event, exhibits a modulation in the azimuthal angles of the planes containing the hadron pairs with respect to the production plane. The measurement of this modulation allows access to combinations of fragmentation functions that are sensitive to the quark's transverse polarization and helicity. Within our uncertainties we do not observe a significant signal from the previously unmeasured helicity dependent fragmentation function $G_1^\perp$. This measurement uses a dataset of 938~fb$^{-1}$ collected by the Belle experiment at or near $\sqrt{s}\approx10.58$ GeV.

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