arXiv subjects

J. H. Kang

Publications and source records attributed to J. H. Kang.

At least 55 records · Page 3Linked to original sources

arXiv2014

Measurement of ${D^{0}}$-${\overline{D}{}^{0}}$ Mixing and Search for Indirect $CP$ Violation Using ${D^0\to K_S^0π^+π^-}$ Decays

We report a measurement of ${D^{0}}$-${\overline{D}{}^{0}}$ mixing parameters and a search for indirect $CP$ violation through a time-dependent amplitude analysis of ${D^0\to K_S^0π^+π^-}$ decays. The results are based on 921~fb$^{-1}$ of data accumulated with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. Assuming $CP$ conservation, we measure the mixing parameters $x=(0.56\pm0.19^{+0.03}_{-0.09}{^{+0.06}_{-0.09}})\%$ and $y=(0.30\pm0.15^{+0.04}_{-0.05}{^{+0.03}_{-0.06})}\%$, where the errors are statistical, experimental systematic, and systematic due to the amplitude model, respectively. With $CP$ violation allowed, the parameters $|q/p|=0.90^{+0.16}_{-0.15}{^{+0.05}_{-0.04}}{^{+0.06}_{-0.05}}$ and $\arg(q/p)=(-6\pm11{\pm3}{^{+3}_{-4}})^{\circ}$ are found to be consistent with conservation of $CP$ symmetry in mixing and in the interference between mixing and decay, respectively.

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arXiv2014

Amplitude analysis of e+e- => Y(nS)pi+pi- at sqrt(s)=10.865 GeV

We report results on studies of the e+e- annihilation into three-body Y(nS)pi+pi- (n=1,2,3) final states including measurements of cross sections and the full amplitude analysis. The cross sections measured at sqrt(s)=10.865 GeV and corrected for the initial state radiation are sigma(e+e-=>Y(1S)pi+pi-)=(2.27+-0.12+-0.14) pb, sigma(e+e-=>Y(2S)pi+pi-)=(4.07+-0.16+-0.45) pb, and sigma(e+e-=>Y(3S)pi+pi-)=(1.46+-0.09+-0.16) pb. Amplitude analysis of the three-body Y(nS)pi+pi- final states strongly favors I^G(J^P)=1^+(1^+) quantum-number assignments for the two bottomonium-like Zb+- states, recently observed in the Y(nS)pi+- and hb(mP)pi+- (m=1,2) decay channels. The results are obtained with a $121.4 1/fb data sample collected with the Belle detector at the KEKB asymmetric-energy e+e- collider.

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arXiv2014

Measurement of branching fractions for B \to J/ψηK decays and search for a narrow resonance in the J/ψηfinal state

We report an observation of the $B^{\pm} \to J/ψηK^{\pm}$ and $B^0 \to J/ψηK^0_S$ decays using 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 obtain the branching fractions ${\cal B}(B^{\pm}\rightarrow J/ψηK^{\pm})=(1.27\pm 0.11{\rm (stat.)\pm 0.11{\rm (syst.)})}\times10^{-4}$ and ${\cal B}(B^0\to J/ψηK^0_S)=(5.22 \pm 0.78 {\rm(stat.)} \pm 0.49{\rm(syst.)})\times10^{-5}$. We search for a new narrow charmonium(-like) state $X$ in the $J/ψη$ mass spectrum and find no significant excess. We set upper limits on the product of branching fractions, ${\cal B}(B^\pm \to XK^\pm){\cal B}(X \to J/ψη)$, at 3872 MeV$/c^2$ where a $C$-odd partner of X(3872) may exist, at $ψ(4040)$ and $ψ(4160)$ assuming their known mass and width, and over a range from 3.8 to 4.8 GeV$/c^2$. % at a 5 MeV$/c^2$ step. The obtained upper limits at 90% confidence level for $X^{C{\rm -odd}}(3872)$, $ψ(4040)$ and $ψ(4160)$ are 3.8$\times 10^{-6}$, 15.5$\times 10^{-6}$ and 7.4$\times 10^{-6}$, respectively.

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arXiv2014

Updated Cross Section Measurement of $e^+ e^- \to K^+ K^- J/ψ$ and $K_S^0K_S^0J/ψ$ via Initial State Radiation at Belle

The cross sections of the processes $e^+ e^- \to K^+ K^- J/ψ$ and $K_S^0K_S^0J/ψ$ are measured via initial state radiation at center-of-mass energies between the threshold and 6.0~GeV using a data sample of 980~fb$^{-1}$ collected with the Belle detector on or near the $Υ(nS)$ resonances, where $n=$1, 2, ..., 5. The cross sections for $e^+ e^- \to K^+ K^- J/ψ$ are at a few pb level and the average cross section for $e^+ e^- \to K_S^0K_S^0J/ψ$ is $1.8\pm 0.6 (\rm stat.)\pm 0.3 (\rm syst.)$~pb between 4.4 and 5.2~GeV. All of them are consistent with previously published results with improved precision. A search for resonant structures and associated intermediate states in the cross section of the process $e^+ e^- \to K^+ K^- J/ψ$ is performed.

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arXiv2014

Search for doubly charmed baryons and study of charmed strange baryons at Belle

We report results of a study of doubly charmed baryons and charmed strange baryons. The analysis is performed using a 980 fb^-1 data sample collected with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. We search for doubly charmed baryons Xi_cc^+(+) with the Lambda_c^+K^-pi^+(pi^+) and Xi_c^0pi^+(pi^+) final states. No significant signal is observed. We also search for two excited charmed strange baryons, Xi_c(3055)^+ and Xi_c(3123)^+ with the Sigma_c^++(2455)K^- and Sigma_c^++(2520)K^- final states. The Xi_c(3055)^+ signal is observed with a significance of 6.6 standard deviations including systematic uncertainty, while no signature of the Xi_c(3123)^+ is seen. We also study properties of the Xi_c(2645)^+ and measure a width of 2.6 +- 0.2 (stat) +- 0.4 (syst) MeV/c^2, which is the first significant determination.

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arXiv2013

Search for B0 to p Lambdabar pi- gamma at Belle

We search for the charmless B^0 decay with final state particles p Lambdabar pi^- gamma using the full data sample that contains 772 * 10^6 B Bar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+ e^- collider. This decay is predicted to proceed predominantly via the b to s gamma radiative penguin process with a high energy photon. No significant signal is found. We set an upper limit of 6.5 * 10^-7 for the branching fraction of B^0 to p Lambdabar pi^- gamma at the 90% confidence level.

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arXiv2013

High-statistics study of K^0_S pair production in two-photon collisions

We report a high-statistics measurement of the differential cross section of the process gamma gamma --> K^0_S K^0_S in the range 1.05 GeV <= W <= 4.00 GeV, where W is the center-of-mass energy of the colliding photons, using 972 fb^{-1} of data collected with the Belle detector at the KEKB asymmetric-energy e^+ e^- collider operated at and near the Upsilon-resonance region. The differential cross section is fitted by parameterized S-, D_0-, D_2-, G_0- and G_2-wave amplitudes. In the D_2 wave, the f_2(1270), a_2(1320) and f_2'(1525) are dominant and a resonance, the f_2(2200), is also present. The f_0(1710) and possibly the f_0(2500) are seen in the S wave. The mass, total width and product of the two-photon partial decay width and decay branching fraction to the K bar{K} state Gamma_{gamma gamma}B(K bar{K}) are extracted for the f_2'(1525), f_0(1710), f_2(2200) and f_0(2500). The destructive interference between the f_2(1270) and a_2(1320) is confirmed by measuring their relative phase. The parameters of the charmonium states chi_{c0} and chi_{c2} are updated. Possible contributions from the chi_{c0}(2P) and chi_{c2}(2P) states are discussed. A new upper limit for the branching fraction of the P- and CP-violating decay channel eta_c --> K^0_S K^0_S is reported. The detailed behavior of the cross section is updated and compared with QCD-based calculations.

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arXiv2013

Search for the process $e^+e^-\to J/ψ+ X(1835)$ at $\sqrt{s}\approx10.6$GeV

We report the results of a search for the $X(1835)$ state in the process $e^+e^-\to J/ψ+X(1835)$ using a data sample of 672 fb$^{-1}$ collected with the Belle detector at and near the $Υ(4S)$ resonance at the KEKB asymmetric-energy $e^+e^-$ collider. No significant evidence is found for this process, and an upper limit is set on its cross section times the branching fraction: $σ_{\rm Born}(e^+e^- \to J/ψX(1835)) \cdot$ {${\cal B}(X(1835)\to \ge 3$ charged tracks)} $< 1.3 \ {\rm fb}$ at 90% confidence level.

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arXiv2013

Measurement of the Decays $B^0_s\to J/ψ\,ϕ(1020)$, $B^0_{s}\to J/ψ\,f'_2(1525)$ and $B^0_s\to J/ψ\,K^+K^-$ at Belle

We report a measurement of the branching fraction of the decay $B^0_s\to J/ψ\,ϕ(1020)$, evidence and a branching fraction measurement for $B^0_s\to J/ψ\,f'_2(1525)$, and the determination of the total $B^0_s\to J/ψ\,K^+K^-$ branching fraction, including the resonant and non-resonant contributions to the $K^+K^-$ channel. We also determine the $S$-wave contribution within the $ϕ(1020)$ mass region. The absolute branching fractions are $\mathcal{B}[B^0_s\to J/ψ\,ϕ(1020)]=(1.25 \pm 0.07\left(\mathrm{stat}\right)\pm 0.08\left(\mathrm{syst}\right)\pm 0.22\left(f_s\right))\times 10^{-3}$, $\mathcal{B}[B^0_s\to J/ψ\,f'_2(1525)]=(0.26\pm 0.06\left(\mathrm{stat}\right)\pm 0.02\left(\mathrm{syst}\right) \pm 0.05\left(f_s\right))\times 10^{-3}$ and $\mathcal{B}[B^0_s\to J/ψ\,K^+K^-] = (1.01\pm 0.09\left(\mathrm{stat}\right) \pm 0.10\left(\mathrm{syst}\right)\pm 0.18\left(f_s\right))\times 10^{-3}$, where the last systematic error is due to the branching fraction of $b\bar{b}\to B^{(*)}_s B^{(*)}_s$. The branching fraction ratio is found to be $\mathcal{B}[B^0_s\to J/ψ\,f'_2(1525)]/\mathcal{B}[B^0_s\to J/ψ\,ϕ(1020)]=(21.5\pm 4.9\left(\mathrm{stat}\right) \pm2.6\left(\mathrm{syst}\right))%$. All results are based on a 121.4 fb$^{-1}$ data sample collected at the $Υ(5S)$ resonance by the Belle experiment at the KEKB asymmetric-energy $e^+e^-$ collider.

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arXiv2013

Experimental constraints on the spin and parity of the Z(4430)+

We perform a full amplitude analysis of B0 -> psi' K+ pi- decays, with psi' -> mu+ mu- or e+ e-, to constrain the spin and parity of the Z(4430)-. The J^P=1+ hypothesis is favored over the 0-, 1-, 2- and 2+ hypotheses at the levels of 3.4 sigma, 3.7 sigma, 4.7 sigma and 5.1 sigma, respectively. The analysis is based on a 711 fb^-1 data sample that contains 772x10^6 B B pairs, collected at the Y(4S) resonance by the Belle detector at the asymmetric-energy e+ e- collider KEKB.

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arXiv2013

First Observation of Cabibbo-Suppressed Ξ_c^0 Decays

We report the first observation of the Cabibbo-suppressed decays $Ξ_c^0\rightarrow Ξ^- K^+$, $Ξ_c^0\raΛK^+ K^-$ and $Ξ_c^0\rightarrow Λϕ$, using a data sample of $711\, \mathrm{fb}^{-1}$ collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We measure the ratios of branching fractions to be $\frac{{\cal B}(Ξ_c^0\ra Ξ^- K^+)}{{\cal B}(Ξ^0_c\raΞ^-π^+)}=(2.75\pm 0.51\pm 0.25)\times 10^{-2}$, $\frac{{\cal B}(Ξ_c^0\raΛK^+ K^-)}{{\cal B}(Ξ_c^0\rightarrowΞ^- π^+)}=(2.86\pm 0.61\pm 0.24)\times 10^{-2}$ and $\frac{{\cal B}(Ξ_c^0\ra Λϕ)}{{\cal B}(Ξ^0_c\raΞ^-π^+)}=(3.43\pm 0.58\pm 0.32)\times 10^{-2}$, where the first uncertainty is statistical and the second is systematic.

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arXiv2013

Evidence for B_s^0 -> Lambda_c^+ Lambda-bar pi^-

Using 121.4 fb^{-1} of data collected with the Belle detector at the Y(5S) resonance at the KEKB asymmetric-energy e^+e^- collider, we report evidence for the B_s^0 -> Lambda_c^+ Lambda-bar pi^- decay mode with a measured branching fraction (3.6 +- 1.1[stat.] {+0.3 -0.5}[syst.] +- 0.9[Lambda_c^+] +- 0.7[N_{Bs}]) * 10^{-4} and a significance of 4.4 standard deviations. This is the first evidence for a baryonic B_s^0 decay.

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arXiv2013

Evidence for Semileptonic B- to p pbar l nubar Decays

We find evidence for the semileptonic baryonic decay $B^-\to p\bar p\ell^-\barν_\ell$ ($\ell=e,μ$), based on a data sample of 772 million $B\bar B$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy electron-positron collider. A neural-network based hadronic $B$-meson tagging method is used in this study. The branching fraction of $B^-\to p\bar p\ell^-\barν_\ell$ is measured to be $(5.8^{+2.4}_{-2.1}\textrm{(stat.)}\pm 0.9\textrm{(syst.)})\times 10^{-6}$ with a significance of 3.2$σ$, where lepton universality is assumed. We also estimate the corresponding upper limit: $\mathcal{B}(B^-\to p\bar p\ell^-\barν_\ell) < 9.6\times 10^{-6}$ at the 90% confidence level. This measurement helps constrain the baryonic transition form factor in B decays.

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arXiv2013

Measurement of $e^+ e^- \to ωπ^0$, $K^{\ast}(892)\bar{K}$ and $K_2^{\ast}(1430)\bar{K}$ at $\sqrt{s}$ near 10.6 GeV

Using data samples of 89 fb$^{-1}$, 703 fb$^{-1}$, and 121 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 10.876 GeV, respectively, we study the exclusive reactions $e^+e^- \to ωπ^0$, $K^{\ast}(892)\bar{K}$, and $K_2^{\ast}(1430)\bar{K}$ (Charge-conjugate modes are included implicitly). Significant signals of $ωπ^0$, $K^{\ast}(892)^0\bar{K}^0$, and $K_2^{\ast}(1430)^-K^+$ are observed for the first time at these energies, and the energy dependencies of the cross sections are presented. On the other hand, no significant excesses for $K^{\ast}(892)^-K^+$ and $K_2^{\ast}(1430)^0 \bar{K}^0$ are found, and we set limits on the cross section ratios $R_{\rm VP} = \frac{σ_B(e^+e^-\to K^{\ast}(892)^0\bar K^0)} {σ_B(e^+e^-\to K^{\ast}(892)^-K^+)}>$ 4.3, 20.0, and 5.4, and $R_{\rm TP} = \frac{σ_B(e^+e^-\to K_2^{\ast}(1430)^0\bar K^0)} {σ_B(e^+e^-\to K_2^{\ast}(1430)^-K^+)}<$ 1.1, 0.4, and 0.6, for center-of-mass energies of 10.52 GeV, 10.58 GeV, and 10.876 GeV, respectively, at the 90% C.L.

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arXiv2013

Search for Bottomonium States in Exclusive Radiative Upsilon(2S) Decays

We search for bottomonium states in Upsilon(2S)-> (bb-bar) gamma decays with an integrated luminosity of 24.7fb^-1 recorded at the Upsilon(2S) resonance with the Belle detector at KEK, containing (157.8+-3.6) X 10^6 Upsilon(2S) events. The (bb-bar) system is reconstructed in 26 exclusive hadronic final states composed of charged pions, kaons, protons, and K^0_S mesons. We find no evidence for the state recently observed around 9975 MeV (X_(bb-bar)) in an analysis based on a data sample of 9.3 X 10^6 Upsilon(2S) events collected with the CLEO III detector. We set a 90 % confidence-level upper limit on the branching fraction B[Upsilon(2S)-> X_(bb-bar) gamma] X \sum_i{B[X_(bb-bar)-> h_i]}< 4.9 X 10^-6, summed over the exclusive hadronic final states employed in our analysis. This result is an order of magnitude smaller than the measurement reported with CLEO data. We also set an upper limit for the eta_b(1S) state of B[Upsilon(2S)-> eta_b(1S) gamma] X \sum_i{B[eta_b(1S)-> h_i]}< 3.7 X 10^-6.

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arXiv2013

First Observation of the Zb0(10610) in a Dalitz Analysis of Y(5S) -> Y(nS) pi0 pi0

We report the first observation of Y(5S) -> Y(nS) pi0 pi0 decays. The neutral partner of the Zb+-(10610), the Zb0(10610) decaying to Y(2,3S) pi0, is observed for the first time with a 6.5 sigma significance using a Dalitz analysis of Y(5S) -> Y(2,3S) pi0 pi0 decays. The results are obtained with a 121.4 fb^-1 data sample collected with the Belle detector at the Y(5S) resonance at the KEKB asymmetric-energy e+e- collider.

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arXiv2013

Precision measurement of charged pion and kaon differential cross sections in electron-positron annihilation at Q = 10.52 GeV

Measurements of inclusive differential cross sections for charged pion and kaon production in electron-positron annihilation have been carried out at a center-of-mass energy of Q = 10.52 GeV. The measurements were performed with the Belle detector at the KEKB electron-positron collider using a data sample containing 113 million e+e- -> qqbar events, where q={u,d,s,c}. We present charge-integrated differential cross sections dσ_h+-/dz for h+- = pi+-, K+- as a function of the relative hadron energy z = 2*E_h / sqrt{s} from 0.2 to 0.98. The combined statistical and systematic uncertainties for pi+- (K+-) are 4% (4%) at z ~ 0.6 and 15% (24%) at z ~ 0.9. The cross sections are the first measurements of the z-dependence of pion and kaon production for z > 0.7 as well as the first precision cross section measurements at a center-of-mass energy far below the Z^0 resonance used by the experiments at LEP and SLC.

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arXiv2013

Measurement of the Wrong-Sign Decay D0 -> K+ pi- pi+ pi-

A measurement of the rate for the "wrong-sign" decay D0 -> K+ pi- pi+ pi- relative to that for the "right-sign" decay D0 -> K- pi+ pi+ pi- is presented. Using 791 fb-1 of data collected with the Belle detector, we obtain a branching fraction ratio of R_WS = [0.324 +- 0.008 (stat) +- 0.007 (sys)]%. Multiplying this ratio by the world average value for the branching fraction B(D0 -> K- pi+ pi+ pi-) gives a branching fraction B(D0 -> K+ pi- pi+ pi-) = (2.61 +- 0.06 +0.09 -0.08) x 10-4.

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