arXiv subjects

Y. Ban

Publications and source records attributed to Y. Ban.

At least 721 records · Page 40Linked to original sources

arXiv2016

Determination of the number of $J/ψ$ events with inclusive $J/ψ$ decays

A measurement of the number of $J/ψ$ events collected with the BESIII detector in 2009 and 2012 is performed using inclusive decays of the $J/ψ$ . The number of $J/ψ$ events taken in 2009 is recalculated to be $(223.7\pm1.4)\times 10^6$, which is in good agreement with the previous measurement, but with significantly improved precision due to improvements in the BESIII software. The number of $J/ψ$ events taken in 2012 is determined to be $(1086.9\pm 6.0)\times 10^6$. In total, the number of $J/ψ$ events collected with the BESIII detector is measured to be $(1310.6\pm 7.0)\times 10^6$, where the uncertainty is dominated by systematic effects and the statistical uncertainty is negligible.

hep-ex↗

arXiv2016

Observation of $e^+e^- \rightarrow ωχ_{c1,2}$ near $\sqrt{s}$ = 4.42 and 4.6 GeV

Based on data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies $\sqrt{s} >$ 4.4 GeV, the processes $e^+e^- \rightarrow ωχ_{c1,2}$ are observed for the first time. With an integrated luminosity of $1074 pb^{-1}$ near $\sqrt{s} =$ 4.42 GeV, a significant $ωχ_{c2}$ signal is found, and the cross section is measured to be $(20.9 \pm 3.2 \pm 2.5)\pb$. With $567 pb^{-1}$ near $\sqrt{s} =$ 4.6 GeV, a clear $ωχ_{c1}$ signal is seen, and the cross section is measured to be $(9.5 \pm 2.1 \pm 1.3) \pb$, while evidence is found for an $ωχ_{c2}$ signal. The first errors are statistical and the second are systematic. Due to low luminosity or low cross section at other energies, no significant signals are observed. In the $ωχ_{c2}$ cross section, an enhancement is seen around $\sqrt{s} =$ 4.42 GeV. Fitting the cross section with a coherent sum of the $ψ(4415)$ Breit-Wigner function and a phase space term, the branching fraction $\mathcal{B}(ψ(4415)\toωχ_{c2})$ is obtained to be of the order of $10^{-3}$.

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arXiv2016

Observation of $h_{c}$ radiative decay $h_{c} \rightarrow γη'$ and evidence for $h_{c} \rightarrow γη$

A search for radiative decays of the $P$-wave spin singlet charmonium resonance $h_c$ is performed based on $4.48 \times 10^{8}$ $ψ'$ events collected with the BESIII detector operating at the BEPCII storage ring. Events of the reaction channels $h_{c} \rightarrow γη'$ and $γη$ are observed with a statistical significance of $8.4 σ$ and $4.0 σ$, respectively, for the first time. The branching fractions of $h_{c} \rightarrow γη'$ and $h_{c} \rightarrow γη$ are measured to be $\mathcal{B}(h_{c} \rightarrow γη')=(1.52 \pm 0.27 \pm 0.29)\times10^{-3}$ and $\mathcal{B}(h_{c} \rightarrow γη)=(4.7 \pm 1.5 \pm 1.4)\times10^{-4}$, respectively, where the first errors are statistical and the second are systematic uncertainties.

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arXiv2016

R&D towards the CMS RPC Phase-2 upgrade

The high pseudo-rapidity region of the CMS muon system is covered by Cathode Strip Chambers (CSC) only and lacks redundant coverage despite the fact that it is a challenging region for muons in terms of backgrounds and momentum resolution. In order to maintain good efficiency for the muon trigger in this region additional RPCs are planned to be installed in the two outermost stations at low angle named RE3/1 and RE4/1. These stations will use RPCs with finer granularity and good timing resolution to mitigate background effects and to increase the redundancy of the system.

physics.ins-det↗

arXiv2016

Improved measurement of the absolute branching fraction of $D^{+}\rightarrow \bar K^0 μ^{+}ν_μ$

By analyzing 2.93 fb$^{-1}$ of data collected at $\sqrt s=3.773$ GeV with the BESIII detector, we measure the absolute branching fraction ${\mathcal B}(D^{+}\rightarrow\bar K^0μ^{+}ν_μ)=(8.72 \pm 0.07_{\rm stat.} \pm 0.18_{\rm sys.})\%$, which is consistent with previous measurements within uncertainties but with significantly improved precision. Combining the Particle Data Group values of ${\mathcal B}(D^0\to K^-μ^+ν_μ)$, ${\mathcal B}(D^{+}\rightarrow\bar K^0 e^{+}ν_{e})$, and the lifetimes of the $D^0$ and $D^+$ mesons with the value of ${\mathcal B}(D^{+}\rightarrow\bar K^0 μ^{+}ν_μ)$ measured in this work, we determine the following ratios of partial widths: $Γ(D^0\to K^-μ^+ν_μ)/Γ(D^{+}\rightarrow\bar K^0μ^{+}ν_μ)=0.963\pm0.044$ and $Γ(D^{+}\rightarrow\bar K^0 μ^{+}ν_μ)/Γ(D^{+}\rightarrow\bar K^0 e^{+}ν_{e})=0.988\pm0.033$.

hep-ex↗

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

Performance of Resistive Plate Chambers installed during the first long shutdown of the CMS experiment

The CMS experiment, located at the CERN Large Hadron Collider, has a redundant muon system composed by three different detector technologies: Cathode Strip Chambers (in the forward regions), Drift Tubes (in the central region) and Resistive Plate Chambers (both its central and forward regions). All three are used for muon reconstruction and triggering. During the first long shutdown (LS1) of the LHC (2013-2014) the CMS muon system has been upgraded with 144 newly installed RPCs on the forth forward stations. The new chambers ensure and enhance the muon trigger efficiency in the high luminosity conditions of the LHC Run2. The chambers have been successfully installed and commissioned. The system has been run successfully and experimental data has been collected and analyzed. The performance results of the newly installed RPCs will be presented.

physics.ins-det↗

arXiv2016

Observation of $e^{+}e^{-} \to η^{\prime} J/ψ$ at center-of-mass energies between 4.189 and 4.600 GeV

The process $e^{+}e^{-}\to η^{\prime} J/ψ$ is observed for the first time with a statistical significance of $8.6σ$ at center-of-mass energy $\sqrt{s} = 4.226$ GeV and $7.3σ$ at $\sqrt{s} = 4.258$ GeV using data samples collected with the BESIII detector. The Born cross sections are measured to be $(3.7 \pm 0.7 \pm 0.3)$ and $(3.9 \pm 0.8 \pm 0.3)$ pb at $\sqrt{s} = 4.226$ and $4.258$ GeV, respectively, where the first errors are statistical and the second systematic. Upper limits at the 90% confidence level of the Born cross sections are also reported at other 12 energy points.

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arXiv2016

Radiation Tests of Real-Sized Prototype RPCs for the Future CMS RPC Upscope

We report on a systematic study of double-gap and four-gap phenolic resistive plate chambers (RPCs) for future high-η RPC triggers in the CMS. In the present study, we constructed real-sized double-gap and four-gap RPCs with gap thicknesses of 1.6 and 0.8 mm, respectively, with 2-mm-thick phenolic high-pressure-laminated (HPL) plates. We examined the prototype RPCs for cosmic rays and 100 GeV muons provided by the SPS H4 beam line at CERN. We applied maximum gamma rates of 1.5 kHz cm-2 provided by 137Cs sources at Korea University and the GIF++ irradiation facility installed at the SPS H4 beam line to examine the rate capabilities of the prototype RPCs. In contrast to the case of the four-gap RPCs, we found the relatively high threshold was conducive to effectively suppressing the rapid increase of strip cluster sizes of muon hits with high voltage, especially when measuring the narrow-pitch strips. The gamma-induced currents drawn in the four-gap RPC were about one-fourth of those drawn in the double-gap RPC. The rate capabilities of both RPC types, proven through the present testing using gamma-ray sources, far exceeded the maximum rate expected in the new high-η endcap RPCs planned for future phase-II LHC runs.

physics.ins-det↗

arXiv2016

Search for $XYZ$ states in $Υ(1S)$ inclusive decays

The branching fractions of the $Υ(1S)$ inclusive decays into final states with a $J/ψ$ or a $ψ(2S)$ are measured with improved precision to be $\BR(Υ(1S)\to J/ψ+ {\rm anything})=(5.25\pm 0.13(\mathrm{stat.})\pm 0.25(\mathrm{syst.}))\times 10^{-4}$ and $\BR(Υ(1S)\to ψ(2S) + {\rm anything})=(1.23\pm 0.17(\mathrm{stat.})\pm 0.11(\mathrm{syst.}))\times 10^{-4}$. The first search for $Υ(1S)$ decays into $XYZ$ states that decay into a $J/ψ$ or a $ψ(2S)$ plus one or two charged tracks yields no significant signals for $XYZ$ states in any of the examined decay modes, and upper limits on their production rates in $Υ(1S)$ inclusive decays are determined.

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arXiv2016

Measurement of the absolute branching fraction of $D^{+}\rightarrow\bar K^0 e^{+}ν_{e}$ via $\bar K^0\toπ^0π^0$

By analyzing 2.93 fb$^{-1}$ data collected at the center-of-mass energy $\sqrt s=3.773$ GeV with the BESIII detector, we measure the absolute branching fraction of the semileptonic decay $D^+\rightarrow\bar K^0 e^{+}ν_{e}$ to be ${\mathcal B}(D^{+}\rightarrow\bar K^0 e^{+}ν_{e})=(8.59 \pm 0.14 \pm 0.21)\%$ using $\bar K^0\to K^0_S\to π^0π^0$, where the first uncertainty is statistical and the second systematic. Our result is consistent with previous measurements within uncertainties.

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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

Observation of an anomalous line shape of the $η^{\prime}π^{+}π^{-}$ mass spectrum near the $p\bar{p}$ mass threshold in $J/ψ\rightarrowγη^{\prime}π^{+}π^{-}$

Using $1.09\times10^{9}$ $J/ψ$ events collected by the BESIII experiment in 2012, we study the $J/ψ\rightarrowγη^{\prime}π^{+}π^{-}$ process and observe a significant abrupt change in the slope of the $η^{\prime}π^{+}π^{-}$ invariant mass distribution at the proton-antiproton ($p\bar{p}$) mass threshold. We use two models to characterize the $η^{\prime}π^{+}π^{-}$ line shape around $1.85~\text{GeV}/c^{2}$: one which explicitly incorporates the opening of a decay threshold in the mass spectrum (Flatté formula), and another which is the coherent sum of two resonant amplitudes. Both fits show almost equally good agreement with data, and suggest the existence of either a broad state around $1.85~\text{GeV}/c^{2}$ with strong couplings to $p\bar{p}$ final states or a narrow state just below the $p\bar{p}$ mass threshold. Although we cannot distinguish between the fits, either one supports the existence of a $p\bar{p}$ molecule-like state or bound state with greater than $7σ$ significance.

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arXiv2016

Study of $ψ$ decays to the $Ξ^{-}\barΞ^{+}$ and $Σ(1385)^{\mp}\barΣ(1385)^{\pm}$ final states

We study the decays of the charmonium resonances $J/ψ$ and $ψ(3686)$ to the final states $Ξ^{-}\barΞ^{+}$, $Σ(1385)^{\mp}\barΣ(1385)^{\pm}$ based on a single baryon tag method using data samples of $(223.7 \pm 1.4) \times 10^{6}$ $J/ψ$ and $(106.4 \pm 0.9) \times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider. The decay $ψ(3686)\rightarrowΣ(1385)^{\mp}\barΣ(1385)^{\pm}$ is observed for the first time, and the measurements of the other processes, including the branching fractions and angular distributions, are in good agreement with and much more precise than the previously published results. Additionally, the ratios $\frac{\cal{B}(ψ(3686)\rightarrowΞ^{-}\barΞ^{+})}{\cal{B}(J/ψ\rightarrowΞ^{-}\barΞ^{+})}$, $\frac{\cal{B}(ψ(3686)\rightarrowΣ(1385)^{-}\barΣ(1385)^{+})}{\cal{B}(J/ψ\rightarrowΣ(1385)^{-}\barΣ(1385)^{+})}$ and $\frac{\cal{B}(ψ(3686)\rightarrowΣ(1385)^{+}\barΣ(1385)^{-})}{\cal{B}(J/ψ\rightarrowΣ(1385)^{+}\barΣ(1385)^{-})}$ are determined.

hep-ex↗

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.

hep-ex↗

arXiv2016

Study of $J/ψ\to p\bar{p}ϕ$ at BESIII

Using a data sample of $1.31 \times 10^{9}$ $J/ψ$ events accumulated with the BESIII detector, the decay $J/ψ\to p\bar{p}ϕ$ is studied via two decay modes, $ϕ\to K^{0}_{S}K^{0}_{L}$ and $ϕ\to K^{+}K^{-}$. The branching fraction of $J/ψ\to p\bar{p}ϕ$ is measured to be $\mathcal{B}(J/ψ\to p\bar{p}ϕ)=[5.23\pm0.06(\mbox{stat})\pm0.33(\mbox{syst})]\times10^{-5}$, which agrees well with a previously published measurement, but with a significantly improved precision. No evident enhancement near the $p\bar{p}$ mass threshold, denoted as $X(p\bar{p})$, is observed, and the upper limit on the branching fraction of $J/ψ\to X(p\bar{p})ϕ\to p\bar{p}ϕ$ is determined to be $\mathcal{B}(J/ψ\to X(p\bar{p})ϕ\to p\bar{p}ϕ)<2.1\times10^{-7}$ at the 90\% confidence level.

hep-ex↗

arXiv2016

Search for the weak decay $η^{\prime}\to K^{\pm}π^{\mp}$ and precise measurement of the branching fraction ${\cal B}(J/ψ\toϕη^{\prime})$

We present the first search for the rare decay of $η^\prime$ into $K^{\pm}π^{\mp}$ in $J/ψ\toϕη^{\prime}$, using a sample of $1.3\times10^{9}$ $J/ψ$ events collected with the BESIII detector. No significant signal is observed, and the upper limit at the 90\% confidence level for the ratio $\frac{{\cal B}(η^{\prime}\to K^{\pm}π^{\mp})}{{\cal B}(η^{\prime}\toγπ^{+}π^{-})}$ is determined to be $1.3\times10^{-4}$. In addition, we report the measurement of the branching fraction of $J/ψ\toϕη^{\prime}$ to be $(5.10\pm0.03(\text{stat.})\pm0.32(\text{syst.}))\times10^{-4}$, which agrees with previous results from BESII.

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arXiv2016

Measurements of absolute hadronic branching fractions of $Λ_{c}^{+}$ baryon

Using $567\rm{pb}^{-1}$ of $e^+e^-$ collisions recorded at $\sqrt{s}=4.599\rm{GeV}$ with the BESIII detector, we report first measurements of absolute hadronic branching fractions of Cabibbo-favored decays of the $Λ_{c}^{+}$ baryon with a double-tag technique. A global least-square fitter is utilized to improve the measured precision. Among the measurements for twelve $Λ_{c}^{+}$ decay modes, the branching fraction for $Λ_{c}^{+} \rightarrow pK^-π^+$ is determined to be $(5.84\pm0.27\pm0.23)\%$, where the first uncertainty is statistical and the second is systematic. In addition, the measurements of the branching fractions of the other eleven Cabbibo-favored hadronic decay modes are significantly improved.

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