arXiv subjects

S. H. Kim

Publications and source records attributed to S. H. Kim.

At least 145 records · Page 8Linked to original sources

arXiv2018

Observation of $e^+e^- \to γχ_{c1}$ and search for $e^+e^- \to γχ_{c0}, γχ_{c2},$ and $γη_c$ at $\sqrt{s}$ near 10.6 GeV at Belle

Using data samples of 89.5~fb$^{-1}$, 711.0~fb$^{-1}$, and 121.4~fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider at center-of-mass energies 10.52 GeV, 10.58 GeV, and 10.867 GeV, respectively, we study the exclusive reactions $e^+e^-\toγχ_{cJ}$ ($J = 0,~1,~2$) and $e^+e^-\toγη_c$. A significant $γχ_{c1}$ signal is observed for the first time at $\sqrt{s}=10.58$ GeV with a significance of $5.1σ$ including systematic uncertainties. No significant excesses for $γχ_{c0}$, $γχ_{c2}$, and $γη_c$ final states are found, and we set 90\% credibility level upper limits on the Born cross sections ($σ_{\rm B}$) at 10.52 GeV, 10.58 GeV, and 10.867~GeV. Together with cross sections measured by BESIII at lower center-of-mass energies, the energy dependency of $σ_{\rm B}(e^+e^-\toγχ_{c1})$ is obtained.

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arXiv2018

Measurement of the Decays $Λ_c\to Σππ$ at Belle

We report measurements of the branching fractions of the decays $Λ^+_c\toΣ^+π^-π^+$, $Λ^+_c\toΣ^0π^+π^0$ and $Λ^+_c\toΣ^+π^0π^0$ relative to the reference channel $Λ^+_c\to pK^-π^+$. The analysis is based on the full data sample collected at and close to $Υ(4S)$ resonance by the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider corresponding to the integrated luminosity of 711 fb$^{-1}$. We measure ${\cal B}(Λ^+_c\rightarrowΣ^+π^-π^+)/{\cal B}(Λ^+_c\to pK^-π^+) = 0.706~\pm 0.003~\pm 0.029$, ${\cal B}(Λ^+_c\rightarrowΣ^0π^+π^0)/{\cal B}(Λ^+_c\to pK^-π^+) = 0.491~\pm 0.005~\pm 0.028$ and ${\cal B}(Λ^+_c\rightarrowΣ^+π^0π^0)/{\cal B}(Λ^+_c\to pK^-π^+) = 0.198~\pm 0.006~\pm 0.016$. The listed uncertainties are statistical and systematic, respectively.

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arXiv2018

Evidence of a structure in $\bar{K}^{0} Λ_{c}^{+}$ consistent with a charged $Ξ_c(2930)^{+}$, and updated measurement of $\bar{B}^{0} \to \bar{K}^{0} Λ_{c}^{+} \barΛ_{c}^{-}$ at Belle

We report evidence for the charged charmed-strange baryon $Ξ_{c}(2930)^+$ with a signal significance of 3.9$σ$ with systematic errors included. The charged $Ξ_{c}(2930)^+$ is found in its decay to $K_{S}^{0} Λ_{c}^+$ in the substructure of $\bar{B}^{0} \to K^{0}_{S} Λ_{c}^{+} \barΛ_{c}^{-}$ decays. The measured mass and width are $[2942.3 \pm 4.4 (\rm stat.) \pm 1.5(\rm syst.)]$~MeV/$c^{2}$ and $[14.8 \pm 8.8(\rm stat.) \pm 2.5(\rm syst.)]$~MeV, respectively, and the product branching fraction is $\cal{B}(\bar{B}^{0} \to Ξ_c(2930)^{+} \barΛ_{c}^{-}) \cal{B}(Ξ_c(2930)^{+}\to \bar{K}^{0} Λ_{c}^{+})=[2.37 \pm 0.51 (\rm stat.)\pm 0.31(\rm syst.)]\times 10^{-4}$. We also measure $\cal{B}(\bar{B}^{0} \to \bar{K}^{0} Λ_{c}^{+} \barΛ_{c}^{-}) = [3.99 \pm 0.76(\rm stat.) \pm 0.51(\rm syst.)] \times 10^{-4}$ with greater precision than previous experiments, and present the results of a search for the charmonium-like state $Y(4660)$ and its spin partner, $Y_η$, in the $Λ_{c}^{+}\barΛ_{c}^{-}$ invariant mass spectrum. No clear signals of the $Y(4660)$ or $Y_η$ are observed and the 90\% credibility level (C.L.) upper limits on their production rates are determined. These measurements are obtained from a sample of $(772\pm11)\times 10^{6} B\bar{B}$ pairs collected at the $Υ(4S)$ resonance by the Belle detector at the KEKB asymmetric energy electron-positron collider.

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arXiv2018

Measurement of the cosmic ray muon flux seasonal variation with the OPERA detector

The OPERA experiment discovered muon neutrino into tau neutrino oscillations in appearance mode, detecting tau leptons by means of nuclear emulsion films. The apparatus was also endowed with electronic detectors with tracking capability, such as scintillator strips and resistive plate chambers. Because of its location, in the underground Gran Sasso laboratory, under 3800 m.w.e., the OPERA detector has also been used as an observatory for TeV muons produced by cosmic rays in the atmosphere. In this paper the measurement of the single muon flux modulation and of its correlation with the seasonal variation of the atmospheric temperature are reported.

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arXiv2018

Observation of $Ξ(1620)^0$ and evidence for $Ξ(1690)^0$ in $Ξ_c^+ \rightarrow Ξ^-π^+π^+$ decays

We report the first observation of the doubly-strange baryon $Ξ(1620)^0$ in its decay to $Ξ^-π^+$ via $Ξ_c^+ \rightarrow Ξ^- π^+ π^+$ decays based on a $980\,{\rm fb}^{-1}$ data sample collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The mass and width are measured to be 1610.4 $\pm$ 6.0 (stat) $^{+5.9}_{-3.5}$ (syst)~MeV$/c^2$ and 59.9 $\pm$ 4.8 (stat) $^{+2.8}_{-3.0}$ (syst)~MeV, respectively. We obtain 4.0$σ$ evidence of the $Ξ(1690)^0$ with the same data sample. These results shed light on the structure of hyperon resonances with strangeness $S=-2$.

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arXiv2018

Search for the lepton-flavor-violating decay $B^{0}\to K^{\ast 0} μ^{\pm} e^{\mp}$

We have searched for the lepton-flavor-violating decay $B^{0}\to K^{\ast 0} μ^{\pm} e^{\mp}$ using a data sample of 711 $fb^{-1}$ that contains $772 \times 10^{6}$ $B\bar{B}$ pairs. The data were collected near the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. No signals were observed, and we set 90% confidence level upper limits on the branching fractions of ${\cal B}(B^{0}\to K^{\ast 0} μ^{+} e^{-})< 1.2\times 10^{-7}$, ${\cal B}(B^{0}\to K^{\ast 0} μ^{-} e^{+})< 1.6\times 10^{-7}$, and, for both decays combined, ${\cal B}(B^{0}\to K^{\ast 0} μ^{\pm} e^{\mp}) < 1.8\times 10^{-7}$. These are the most stringent limits on these decays to date.

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arXiv2018

Measurements of isospin asymmetry and difference of direct $CP$ asymmetries in inclusive $B \to X_s γ$ decays

We report measurements of isospin asymmetry $Δ_{0-}$ and difference of direct $CP$ asymmetries $ΔA_{CP}$ between charged and neutral $B \to X_s γ$ decays. This analysis is based on the data sample containing $772 \times 10^6 B\bar{B}$ pairs that was collected with the Belle detector at the KEKB energy-asymmetric $e^+ e^-$ collider. Using a sum-of-exclusive technique with invariant $X_s$ mass up to 2.8~GeV/$c^2$, we obtain $Δ_{0-} = \bigl[-0.48 \pm 1.49 {\rm (stat.)} \pm 0.97 {\rm (syst.)} \pm 1.15 {(f_{+-}/f_{00})}\bigr]$\% and $ΔA_{CP} = \bigl[+3.69 \pm 2.65 {\rm (stat.)} \pm 0.76{\rm (syst.)}\bigr]$\%, where the last uncertainty for $Δ_{0-}$ is due to the uncertainty on the production ratio of $B^+B^-$ to $B^0\bar{B}^0$ in $Υ(4S)$ decays. The measured value of $Δ_{0-}$ is consistent with zero, allowing us to constrain the resolved photon contribution in the $B \to X_s γ$, and improve the branching fraction prediction. The result for $ΔA_{CP}$ is consistent with the prediction of the SM. We also measure the direct $CP$ asymmetries for charged and neutral $B \to X_s γ$ decays. All the measurements are the most precise to date.

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arXiv2018

Observation of $Ξ_{c}(2930)^0$ and updated measurement of $B^{-} \to K^{-} Λ_{c}^{+} \barΛ_{c}^{-}$ at Belle

We report the first observation of the $Ξ_{c}(2930)^0$ charmed-strange baryon with a significance greater than 5$σ$. The $Ξ_{c}(2930)^0$ is found in its decay to $K^- Λ_{c}^+$ in $B^{-} \to K^{-} Λ_{c}^{+} \barΛ_{c}^{-}$ decays. The measured mass and width are $[2928.9 \pm 3.0(\rm stat.)^{+0.9}_{-12.0}(\rm syst.)]$ MeV/$c^{2}$ and $[19.5 \pm 8.4(\rm stat.) ^{+5.9}_{-7.9}(\rm syst.)]$ MeV, respectively, and the product branching fraction is ${\cal B}(B^{-} \to Ξ_{c}(2930)^0 \barΛ_{c}^{-}) {\cal B}(Ξ_{c}(2930)^0 \to K^- Λ_{c}^{+})=[1.73 \pm 0.45(\rm stat.) \pm 0.21(\rm syst.)]\times 10^{-4}$. We also measure ${\cal B}(B^{-} \to K^{-} Λ_{c}^{+} \barΛ_{c}^{-}) = [4.80 \pm 0.43(\rm stat.) \pm 0.60(\rm syst.)] \times 10^{-4}$ with improved precision, and search for the charmonium-like state $Y(4660)$ and its spin partner, $Y_η$, in the $Λ_{c}^{+}\barΛ_{c}^{-}$ invariant mass spectrum. No clear signals of the $Y(4660)$ nor its spin partner are observed and the 90\% credibility level (C.L.) upper limits on their production rates are determined. These measurements are obtained from a sample of $(772\pm11)\times 10^{6} B\bar{B}$ pairs collected at the $Υ(4S)$ resonance by the Belle detector at the KEKB asymmetric energy electron-positron collider.

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arXiv2018

Observation of Transverse $Λ/\barΛ$ Hyperon Polarization in $e^+e^-$ Annihilation at Belle

We report the first observation of the spontaneous polarization of $Λ$ and $\barΛ$ hyperons transverse to the production plane in $e^+e^-$ annihilation, which is attributed to the effect arising from a polarizing fragmentation function. For inclusive $Λ/\barΛ$ production, we also report results with subtracted feed-down contributions from $Σ^0$ and charm. This measurement uses a dataset of 800.4 fb$^{-1}$ collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV. We observe a significant polarization that rises with the fractional energy carried by the $Λ/\barΛ$ hyperon.

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arXiv2018

Measurement of the branching fraction of $B \rightarrow D^{(*)}π\ellν$ at Belle using hadronic tagging in fully reconstructed events

We report a measurement of the branching fraction of the decay $B \rightarrow D^{(*)}π\ellν$. The analysis uses 772$\times 10^6$ $B\bar{B}$ pairs produced in $e^+e^-\rightarrow Υ(4S)$ data recorded by the Belle experiment at the KEKB asymmetric-energy $e^+e^-$ collider. The tagging $B$ meson in the decay is fully reconstructed in a hadronic decay mode. On the signal side, we reconstruct the decay $B \rightarrow D^{(*)}π\ellν$ $(\ell=e,μ)$. The measured branching fractions are $\mathcal{B}(B^+ \rightarrow D^-π^+ \ell^+ν)$ = [4.55 $\pm$ 0.27 (stat.) $\pm$ 0.39 (syst.)]$\times 10^{-3}$, $\mathcal{B}(B^0 \rightarrow \bar{D}^0π^- \ell^+ν)$ = [4.05 $\pm$ 0.36 (stat.) $\pm$ 0.41 (syst.)]$\times 10^{-3}$, $\mathcal{B}(B^+ \rightarrow D^{*-}π^+ \ell^+ν)$ = [6.03 $\pm$ 0.43 (stat.) $\pm$ 0.38 (syst.)]$\times 10^{-3}$, and $\mathcal{B}(B^0 \rightarrow \bar{D}^{*0}π^- \ell^+ν)$ = [6.46 $\pm$ 0.53 (stat.) $\pm$ 0.52 (syst.)]$\times 10^{-3}$. These are in good agreement with the current world average values.

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arXiv2018

Development of Slow Control Package for the Belle II Calorimeter Trigger System

The Belle II experiment at the SuperKEKB e+e- collider in KEK, Japan does start physics data-taking from early of 2018 with primary physics goal that is to probe the New Physics effect using heavy quark and lepton weak decays. During trigger and DAQ operation upon beam collision, it is important that Belle II detector (Fig. 1) status have to be monitored in a process of data-taking against an unexpected situation. Slow control system, built in the Control System Studio (CSS) which is a GUI window design tool based on Eclipse, is one of monitoring and controlling systems in Belle II operation. Database and archiver servers are connected to slow control system. Experimental parameters are downloaded to Belle II main database server which is based on PostgreSQL. Real-time results are stored in archiver server which is based on EPICS (The Experimental Physics and Industrial Control System) archiver appliances and tomcat which is open-source java servlet container. In this study, we report the development of slow control system for the Belle II electromagnetic calorimeter (ECL) trigger system.

physics.ins-det↗

arXiv2018

Progress on the Electromagnetic Calorimeter Trigger Simulation at the Belle II Experiment

The Belle II experiment at KEK in Japan has started real data taking from April 2018 to probe a New Physics beyond the Standard Model by measuring CP violation precisely and rare weak decays of heavy quark and lepton. The experiment is performed at the high luminosity SuperKEKB e^+ e^- collider with 80 x 10^34 cm^-2 s^-1 as an ultimate instantaneous luminosity. In order to develop and test an appropriate trigger algorithm under much higher luminosity and beam background environment than previous KEKB collider, a detail simulation study of the Belle II calorimeter trigger system is very crucial to operate Belle II Trigger and DAQ system in stable. We report preliminary results on various trigger logics and their efficiencies using physics and beam background Monte Carlo events with a Belle II Geant4-based analysis framework called Basf2.

physics.ins-det↗

arXiv2018

Search for $Υ(1S,2S) \to Z^{+}_{c}Z^{(\prime) -}_{c}$ and $e^{+}e^{-} \to Z^{+}_{c}Z^{(\prime) -}_{c}$ at $\sqrt{s}$ = 10.52, 10.58, and 10.867 GeV

The first search for $Z_{c}$ pair production in $Υ(1S)$ and $Υ(2S)$ decays and in $e^{+}e^{-}$ annihilation at $\sqrt{s}$ = 10.52, 10.58, and 10.867 GeV is conducted using data collected with the Belle detector at the KEKB asymmetric energy electron-positron collider. No significant signals are observed in any of the studied modes, and the 90\% credibility level upper limits on their product branching fractions in $Υ(1S)$ and $Υ(2S)$ decays (${\cal B}(Υ(1S,2S)\to Z^{+}_{c}Z^{(\prime) -}_{c})\times{\cal B}(Z^{+}_{c}\toπ^{+}+c\bar c)$ ($c\bar c=J/ψ$, $χ_{c1}(1P)$, $ψ(2S)$)) and the product of Born cross section and branching fraction for $e^{+}e^{-} \to Z^{+}_{c}Z^{(\prime) -}_{c}$ ($σ(e^+e^- \to Z^{+}_{c}Z^{(\prime) -}_{c})\times {\cal B}(Z^{+}_{c} \to π^+ +c\bar c)$) at $\sqrt{s}$ = 10.52, 10.58, and 10.867 GeV are determined. Here, $Z_{c}$ refers to the $Z_{c}(3900)$ and $Z_{c}(4200)$ observed in the $πJ/ψ$ final state, the $Z_{c1}(4050)$ and $Z_{c2}(4250)$ in the $πχ_{c1}(1P)$ state, and the $Z_{c}(4050)$ and $Z_{c}(4430)$ in the $πψ(2S)$ state.

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arXiv2018

Final results of the search for $ν_μ \to ν_{e}$ oscillations with the OPERA detector in the CNGS beam

The OPERA experiment has discovered the tau neutrino appearance in the CNGS muon neutrino beam, in agreement with the 3 neutrino flavour oscillation hypothesis. The OPERA neutrino interaction target, made of Emulsion Cloud Chamber, was particularly efficient in the reconstruction of electromagnetic showers. Moreover, thanks to the very high granularity of the emulsion films, showers induced by electrons can be distinguished from those induced by $π^0$s, thus allowing the detection of charged current interactions of electron neutrinos. In this paper the results of the search for electron neutrino events using the full dataset are reported. An improved method for the electron neutrino energy estimation is exploited. Data are compatible with the 3 neutrino flavour mixing model expectations and are used to set limits on the oscillation parameters of the 3+1 neutrino mixing model, in which an additional mass eigenstate $m_{4}$ is introduced. At high $Δm^{2}_{41}$ $( \gtrsim 0.1~\textrm{eV}^{2})$, an upper limit on $\sin^2 2θ_{μe}$ is set to 0.021 at 90% C.L. and $Δm^2_{41} \gtrsim 4 \times 10^{-3}~\textrm{eV}^{2}$ is excluded for maximal mixing in appearance mode.

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arXiv2018

Measurements of the absolute branching fractions of $B^{+} \to X_{c\bar{c}} K^{+}$ and $B^{+} \to \bar{D}^{(\ast) 0} π^{+} $ at Belle

We present the measurement of the absolute branching fractions of $B^{+} \to X_{c\bar{c}} K^{+}$ and $B^{+} \to \bar{D}^{(\ast) 0} π^{+} $ decays, 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. Here, $X_{c\bar{c}}$ denotes $η_{c}$, $J/ψ$, $χ_{c0}$, $χ_{c1}$, $η_{c}(2S)$, $ψ(2S)$, $ψ(3770)$, $X(3872)$, and $X(3915)$. We do not observe significant signals for $X(3872)$ nor $X(3915)$, and set the 90$\%$ confidence level upper limits: ${\cal B}(B^{+} \to X(3872) K^{+} )<2.7 \times 10^{-4}$ and ${\cal B}(B^{+} \to X(3915) K^{+} )<2.9 \times 10^{-4}$. These represent the most stringent upper limit for ${\cal B}(B^{+} \to X(3872) K^{+} )$ to date and the first measurement for ${\cal B}(B^{+} \to X(3915) K^{+} )$. The measured branching fractions for $η_{c}$ and $η_{c}(2S)$ are the most precise to date: ${\cal B}(B^{+} \to η_{c} K^{+} )=(12.3\pm0.8\pm0.7) \times 10^{-4}$ and ${\cal B}(B^{+} \to η_{c}(2S)K^{+}) =(4.9\pm1.1\pm0.3) \times 10^{-4}$ , where the first and second uncertainties are statistical and systematic, respectively.

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arXiv2018

Observation of an excited $Ω^-$ baryon

Using data recorded with the Belle detector, we observe a new excited hyperon, an $Ω^{*-}$ candidate decaying into $Ξ^0K^-$ and $Ξ^-K^0_S$ with a mass of $2012.4\pm0.7\ {\rm (stat)\pm\ 0.6\ (\rm syst)}\ {\rm MeV}/c^2$ and a width of $Γ=6.4^{+2.5}_{-2.0}\ {\rm(stat)}\pm1.6\ {\rm(syst)}\ {\rm MeV}$. The $Ω^{*-}$ is seen primarily in $Υ(1S), Υ(2S)$, and $Υ(3S)$ decays.

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arXiv2018

Measurement of Time-dependent $CP$ Asymmetries in $B^{0}\to K_S^0 ηγ$ Decays

We report a measurement of time-dependent $CP$ violation parameters in ${B^0 \to K_S^0 ηγ}$ decays. The study is based on a data sample, containing ${772 \times 10^6 B\bar{B}}$ pairs, that was collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We obtain the $CP$ violation parameters of ${{\cal S} = -1.32 \pm 0.77 {\rm (stat.)} \pm 0.36{\rm (syst.)}}$ and ${{\cal A} = -0.48 \pm 0.41 {\rm (stat.)} \pm 0.07{\rm (syst.)}}$ for the invariant mass of the $K_S^0 η$ system up to 2.1 GeV/$c^2$.

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arXiv2018

Final results of the OPERA experiment on $ν_τ$ appearance in the CNGS beam

The OPERA experiment was designed to study $ν_μ\toν_τ$ oscillations in appearance mode in the CNGS neutrino beam. In this letter we report the final analysis of the full data sample collected between 2008 and 2012, corresponding to $17.97\cdot 10^{19}$ protons on target. Selection criteria looser than in previous analyses have produced ten $ν_τ$ candidate events, thus reducing the statistical uncertainty in the measurement of the oscillation parameters and of $ν_τ$ properties. A multivariate approach for event identification has been applied to the candidate events and the discovery of $ν_τ$ appearance is confirmed with an improved significance level of 6.1 $σ$. $Δm^2_{23}$ has been measured, in appearance mode, with an accuracy of 20%. The measurement of $ν_τ$ CC cross-section, for the first time with a negligible contamination from $\barν_τ$, and the first direct observation of the $ν_τ$ lepton number are also reported.

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