arXiv subjects

P. Katrenko

Publications and source records attributed to P. Katrenko.

At least 19 recordsLinked to original sources

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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arXiv2018

Production cross sections of hyperons and charmed baryons from $e^+e^-$ annihilation near $\sqrt{s} = 10.52$~GeV

We measure the inclusive production cross sections of hyperons and charmed baryons from $e^+e^-$ annihilation using a 800 fb$^{-1}$ data sample taken near the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The feed-down contributions from heavy particles are subtracted using our data, and the direct production cross sections are presented for the first time. The production cross sections divided by the number of spin states for $S=-1$ hyperons follow an exponential function with a single slope parameter except for the $Σ(1385)^+$ resonance. Suppression for $Σ(1385)^+$ and $Ξ(1530)^0$ hyperons is observed. Among the production cross sections of charmed baryons, a factor of three difference for $Λ_c^+$ states over $Σ_c$ states is observed. This observation suggests a diquark structure for these baryons.

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arXiv2018

Search for $CP$ violation in the $D^{+}\toπ^{+}π^{0}$ decay at Belle

We search for $CP$ violation in the charged charm meson decay $D^{+}\toπ^{+}π^{0}$, based on a data sample corresponding to an integrated luminosity of $\rm 921~fb^{-1}$ collected by the Belle experiment at the KEKB $e^{+}e^{-}$ asymmetric-energy collider. The measured $CP$ violating asymmetry is $[+2.31\pm1.24({\rm stat})\pm0.23({\rm syst})]\%$, which is consistent with the standard model prediction and has a significantly improved precision compared to previous results.

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arXiv2017

Measurement of the branching fraction and $CP$ asymmetry in $B^{0} \to π^{0}π^{0}$ decays, and an improved constraint on $ϕ_{2}$

We measure the branching fraction and $CP$ violation asymmetry in the decay $B^{0}\to π^{0}π^{0}$, using a data sample of $752\times 10^{6}$ $B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^{+}e^{-}$ collider. The obtained branching fraction and direct $CP$ asymmetry are $ \mathcal{B}(B\to π^{0}π^{0}) = [1.31 \pm 0.19~ \text{(stat.)} \pm 0.19~ \text{(syst.)}] \times 10^{-6}$ and $ A_{CP} = +0.14 \pm 0.36~ \text{(stat.)} \pm 0.10~ \text{(syst.)}, $ respectively. The signal significance, including the systematic uncertainty, is 6.4 standard deviations. We combine these results with Belle's earlier measurements of $B^{0}\to π^{+} π^{-}$ and $B^{\pm} \to π^{\pm} π^{0}$ to exclude the $CP$-violating parameter $ϕ_{2}$ from the range $15.5^{\circ} < ϕ_{2} < 75.0^{\circ}$ at 95\% confidence level.

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arXiv2017

Measurement of branching fraction and direct $CP$ asymmetry in charmless $B^+ \to K^+K^- π^+$ decays at Belle

We report a study of the charmless hadronic decay of the charged $B$ meson to the three-body final state $K^+ K^- π^+$. The results are based on a data sample that contains $772\times10^6$ $B \bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The measured inclusive branching fraction and the direct $CP$ asymmetry are $(5.38\pm0.40\pm0.35)\times 10^{-6}$ and $-0.170\pm0.073\pm0.017$, respectively, where the first uncertainties are statistical and the second are systematic. The $K^{+}K^{-}$ invariant mass distribution of the signal candidates shows an excess in the region below $1.5$ GeV/$c^2$, which is consistent with the previous studies from BaBar and LHCb. In addition, strong evidence of a large direct $CP$ asymmetry is found in the $K^{+}K^{-}$ low-invariant-mass region.

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arXiv2017

Search for $\boldsymbol{B\to hν\barν}$ decays with semileptonic tagging at Belle

We present the results of a search for the rare decays $B\to hν\overlineν$, where $h$ stands for $K^+,\:K^0_{\mathrm{S}},\:K^{\ast +},\:K^{\ast 0},\:π^+,\:π^0,\:ρ^+$ and $ρ^{0}$. The results are obtained with $772\times10^{6}$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB $e^+ e^-$ collider. We reconstruct one $B$ meson in a semileptonic decay and require a single $h$ meson but nothing else on the signal side. We observe no significant signal and set upper limits on the branching fractions. The limits set on the $B\to K^0_{\mathrm{S}}ν\overlineν$, $B^0\to K^{*0}ν\overlineν$, $B\to π^+ν\overlineν$, $B^0\toπ^0ν\overlineν$, $B^+\toρ^+ν\overlineν$, and $B^0\toρ^0ν\overlineν$ channels are the world's most stringent.

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arXiv2017

Search for $CP$ Violation and Measurement of the Branching Fraction in the Decay $D^{0} \to K^0_S K^0_S$

We report a study of the decay $D^0 \to K^0_S K^0_S$ using 921~fb$^{-1}$ of data collected at or near the $Υ(4S)$ and $Υ(5S)$ resonances with the Belle detector at the KEKB asymmetric energy $e^+e^-$ collider. The measured time-integrated $CP$ asymmetry is $ A_{CP}(D^0 \to K^0_S K^0_S) = (-0.02 \pm 1.53 \pm 0.02 \pm 0.17) \%$, and the branching fraction is $\mathcal{B} (D^{0}\rightarrow K_{S}^{0}K_{S}^{0})$ = (1.321 $\pm$ 0.023 $\pm$ 0.036 $\pm$ 0.044) $\times$ 10$^{-4}$, where the first uncertainty is statistical, the second is systematic, and the third is due to the normalization mode ($D^0 \to K_S^0 π^0$). These results are significantly more precise than previous measurements available for this mode. The $A_{CP}$ measurement is consistent with the standard model expectation.

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arXiv2017

Observation of an alternative $χ_{c0}(2P)$ candidate in $e^+ e^- \rightarrow J/ψD \bar{D}$

We perform a full amplitude analysis of the process $e^+ e^- \rightarrow J/ψD \bar{D}$, where $D$ refers to either $D^0$ or $D^+$. A new charmoniumlike state $X^*(3860)$ that decays to $D \bar{D}$ is observed with a significance of $6.5σ$. Its mass is ($3862^{+26}_{-32}{}^{+40}_{-13}$) MeV/$c^2$ and width is ($201^{+154}_{-67}{}^{+88}_{-82}$) MeV. The $J^{PC}=0^{++}$ hypothesis is favored over the $2^{++}$ hypothesis at the level of $2.5σ$. The analysis is based on the 980 $\mathrm{fb}^{-1}$ data sample collected by the Belle detector at the asymmetric-energy $e^+ e^-$ collider KEKB.

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arXiv2017

Search for the $0^{--}$ Glueball in $Υ(1S)$ and $Υ(2S)$ decays

We report the first search for the $J^{PC}=0^{--}$ glueball in $Υ(1S)$ and $Υ(2S)$ decays with data samples of $(102\pm2)$ million and $(158\pm4)$ million events, respectively, collected with the Belle detector. No significant signals are observed in any of the proposed production modes, and the 90\% credibility level upper limits on their branching fractions in $Υ(1S)$ and $Υ(2S)$ decays are obtained. The inclusive branching fractions of the $Υ(1S)$ and $Υ(2S)$ decays into final states with a $χ_{c1}$ are measured to be $\BR(Υ(1S)\to χ_{c1}+ anything) = (1.90\pm 0.43(stat.)\pm 0.14(syst.))\times 10^{-4}$ with an improved precision over prior measurements and $\BR(Υ(2S)\to χ_{c1}+ anything) = (2.24\pm 0.44(stat.)\pm 0.20(syst.))\times 10^{-4}$ for the first time.

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arXiv2016

Lepton-Flavor-Dependent Angular Analysis of $B\to K^\ast \ell^+\ell^-$

We present a measurement of angular observables and a test of lepton flavor universality in the $B\to K^\ast \ell^+\ell^-$ decay, where $\ell$ is either $e$ or $μ$. 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. The result is consistent with Standard Model (SM) expectations, where the largest discrepancy from a SM prediction is observed in the muon modes with a local significance of $2.6σ$.

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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 the 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 the standard deviation $σ$ includes systematic uncertainties. We use this measurement to constrain several scenarios of new physics in a model-independent approach.

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arXiv2016

Study of $\mathbf{B^{0}\rightarrowρ^{+}ρ^{-}}$ decays and implications for the CKM angle $\mathbf{ϕ_2}$

We present a measurement of the branching fraction and the longitudinal polarization fraction of $B^{0}\rightarrowρ^+ρ^-$ decays, as well as the time-dependent $CP$ violating parameters in decays into longitudinally polarized $ρ^{+}ρ^{-}$ pairs with Belle's final data set of $772\times 10^6$ $B\bar{B}$ pairs, at the $Υ(4S)$ resonance, collected at the asymmetric-energy $e^+ e^-$ collider KEKB. We obtain ${\cal B}(B^0 \rightarrow ρ^+ ρ^-)=(28.3\pm 1.5\;(\rm stat) \pm 1.5\;(\rm syst))\times 10^{-6}$, $f_L = 0.988\pm 0.012\;(\rm stat ) \pm0.023\;(\rm syst)$, ${\cal A}_{CP} = 0.00\pm0.10\;(\rm stat ) \pm0.06\;(\rm syst)$, ${\cal S}_{CP} = -0.13\pm0.15\;(\rm stat ) \pm0.05\;(\rm syst).$ We perform an isospin analysis to constrain the CKM angle $ϕ_2$ and obtain two solutions with \begin{eqnarray} ϕ_{2} = (93.7\pm10.6)^{\circ},\nonumber \end{eqnarray} being most compatible with other Standard-Model based fits to the data.

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arXiv2016

Search for a massive invisible particle $X^0$ in $B^{+}\to e^{+}X^{0}$ and $B^{+}\to μ^{+}X^{0}$ decays

We present a search for a non-Standard-Model invisible particle $X^0$ in the mass range $0.1\textrm{-}1.8 \,{\rm GeV}/{c^2}$ in $B^{+}\to e^{+} X^{0}$ and $B^{+}\to μ^{+} X^{0}$ decays. The results are obtained from a $711~{\rm fb}^{-1}$ data sample that corresponds to $772 \times 10^{6} B\bar{B}$ pairs, collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. One $B$ meson is fully reconstructed in a hadronic mode to determine the momentum of the lepton of the signal decay in the rest frame of the recoiling partner $B$ meson. We find no evidence of a signal and set upper limits on the order of $10^{-6}$.

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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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arXiv2015

First Observation of Doubly Cabibbo-Suppressed Decay of a Charmed Baryon: $Λ^{+}_{c} \rightarrow p K^{+} π^{-}$

We report the first observation of the decay $Λ^{+}_{c} \rightarrow p K^{+} π^{-}$ using a 980 $\mathrm{fb^{-1}}$ data sample collected by the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. This is the first doubly Cabibbo-suppressed decay of a charmed baryon to be observed. We measure the branching ratio of this decay with respect to its Cabibbo-favored counterpart to be $\mathcal{B}(Λ^{+}_{c} \rightarrow p K^{+} π^{-})/\mathcal{B}(Λ^{+}_{c} \rightarrow p K^{-} π^{+})=(2.35\pm0.27\pm0.21)\times10^{-3}$, where the uncertainties are statistical and systematic, respectively.

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arXiv2015

First Observation of the Decay B0->psi(2S)pi0

We report a measurement of the $B^0\rightarrowψ(2S)π^0$ branching fraction based on the full $Υ(4S)$ data set of $772\times10^{6}$ $B\bar{B}$ pairs collected by the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We obtain $B(B^0\rightarrowψ(2S)π^0) = (1.17\pm0.17\text{(stat)}\pm0.08\text{(syst)})\times10^{-5}$. The result has a significance of 7.2 standard deviations and is the first observation of the decay $B^0\rightarrowψ(2S)π^0$.

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arXiv2015

Inclusive cross sections for pairs of identified light charged hadrons and for single protons in $e^+e^-$ at $\sqrt{s}=$ 10.58 GeV

We report the first double differential cross sections of two charged pions and kaons ($e^+e^- \rightarrow hhX$) in electron-positron annihilation as a function of the fractional energies of the two hadrons for any charge and hadron combination. The dependence of these di-hadron cross sections on the topology (same, opposite-hemisphere or anywhere) is also studied with the help of the event shape variable thrust and its axis. The ratios of these di-hadron cross sections for different charges and hadron combinations directly shed light on the contributing fragmentation functions. For example, we find that the ratio of same-sign pion pairs over opposite-sign pion pairs drops toward higher fractional energies where disfavored fragmentation is expected to be suppressed. These di-hadron results are obtained from a $655\,{\rm fb}^{-1}$ data sample collected near the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. Extending the previously published single-pion and single-kaon cross sections, single-proton ($e^+e^- \rightarrow pX$) cross sections are extracted from a $159\,{\rm fb}^{-1}$ data sub-sample.

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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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