arXiv subjects

Y. M. Goh

Publications and source records attributed to Y. M. Goh.

121 records · Page 7Linked to original sources

arXiv2012

Search for $B^{0}$ decays to invisible final states at Belle

We report a search for $B^{0}$ decays into invisible final states using a data sample of $657 \times 10^{6}$ $B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^{+}e^{-}$ collider. The signal is identified by fully reconstructing a hadronic decay of the accompanying $B$ meson and requiring no other particles in the event. No significant signal is observed, and we obtain an upper limit of $1.3 \times 10^{-4}$ at the 90% confidence level for the branching fraction of invisible $B^{0}$ decay.

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arXiv2012

First Measurement of phi_3 with a Model-independent Dalitz Plot Analysis of B->DK, D->KsPiPi Decay

We present the first measurement of the angle phi_3 of the Unitarity Triangle using a model-independent Dalitz plot analysis of B->DK, D->KsPiPi decays. The method uses an input measurements of the strong phase of the D->KsPiPi amplitude from the CLEO collaboration. The result is based on the full data set of 772x10^6 BBbar pairs collected by the Belle experiment at the Upsilon(4S) resonance. We obtain phi_3 = (77.3^{+15.1}_{-14.9} +- 4.1 +- 4.3)^{\circ} and the suppressed amplitude ratio r_B = 0.145 +- 0.030 +- 0.010 +- 0.011. Here the first error is statistical, the second is the experimental systematic uncertainty, and the third is the error due to the precision of the strong-phase parameters obtained by CLEO.

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arXiv2012

First observation of exclusive $Υ(1S)$ and $Υ(2S)$ decays into light hadrons

Using samples of 102 million $Υ(1S)$ and 158 million $Υ(2S)$ events collected with the Belle detector, we study exclusive hadronic decays of these two bottomonium resonances to the three-body final states $ϕK^+ K^-$, $ωπ^+ π^-$ and $K^{\ast 0}(892) K^- π^+ $, and to the two-body Vector-Tensor ($ϕf_2'(1525)$, $ωf_2(1270)$, $ρa_2(1320)$ and $K^{\ast 0}(892) \bar{K}_2^{\ast 0}(1430) $) and Axial-vector-Pseudoscalar ($K_1(1270)^+ K^-$, $K_1(1400)^+ K^- $ and $b_1(1235)^+ π^- $) pairs. Signals are observed for the first time in the $Υ(1S) \to ϕK^+ K^-$, $ωπ^+ π^-$, $K^{\ast 0} K^- π^+$, $K^{\ast0} K_2^{\ast 0}$ and $Υ(2S) \to ϕK^+ K^-$, $K^{\ast 0} K^- π^+$ decay modes. Branching fractions are determined for all the processes, while 90% confidence level upper limits are established on the branching fractions for the modes with a statistical significance less than $3σ$. The ratios of the branching fractions of $Υ(2S)$ and $Υ(1S)$ decays into the same final state are used to test a perturbative QCD prediction for OZI suppressed bottomonium decays.

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arXiv2012

Evidence for a Zb0(10610) in Dalitz analysis of Y(5S) -> Y(nS) pi0 pi0

We report the first observation of Y(5S) -> Y(1,2S) pi0 pi0 decays. Evidence for the Zb0(10610) with 4.9sigma significance is found in a Dalitz plot analysis of Y(5S) -> Y(2S) 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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arXiv2012

Search for B -> phi pi decays

We report on a search for the charmless decays $B^{+} \toϕπ^{+}$ and $B^{0} \toϕπ^{0}$ that are strongly suppressed in the Standard Model. The analysis is based on a data sample of $657 \times 10^6$ $B \bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We find no significant signal and set upper limits of $3.3 \times 10^{-7}$ for $B^{+} \to ϕπ^{+}$ and $1.5 \times 10^{-7}$ for $B^0 \to ϕπ^0$ at the 90% confidence level.

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arXiv2012

First study of η_c, η(1760) and X(1835) production via η'π^+π^- final states in two-photon collisions

The invariant mass spectrum of the η' π^+ π^- final state produced in two-photon collisions is obtained using a 673 fb^{-1} data sample collected in the vicinity of the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. We observe a clear signal of the η_c and measure its mass and width to be M(η_c)=(2982.7 +- 1.8(stat) +- 2.2(syst) +- 0.3(model)) MeV/c^2 and Γ(η_c) = (37.8^{+5.8}_{-5.3}(stat) +- 2.8(syst) +- 1.4(model)) MeV/c^2. The third error is an uncertainty due to possible interference between the η_c and a non-resonant component. We also report the first evidence for η(1760) decay to η' π^+ π^-; we find two solutions for its parameters, depending on the inclusion or not of the X(1835), whose existence is of marginal significance in our data. From a fit to the mass spectrum using coherent X(1835) and η(1760) resonant amplitudes, we set a 90% confidence level upper limit on the product Γ_{γγ} \BR (η' π^+ π^-) for the X(1835).

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arXiv2012

Search for the decay $B^0\to DK^{*0}$ followed by $D\to K^-π^+$

We report a study of the decay $B^0\rightarrow D K^+π^-$ followed by $D\rightarrow K^-π^+$, where $D$ indicates $D^0$ or $\bar{D}^0$. We reconstruct the $D K^+π^-$ state in a phase space corresponding to $D K^{*}(892)^0$. The CP-violating angle $ϕ_3$ affects its decay rate via the interference between $b\rightarrow u$ and $b\rightarrow c$ transitions. The result is obtained from a 711 ${\rm fb}^{-1}$ data sample that contains 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 measure the ratio ${\cal R}_{DK^{*0}} \equiv Γ(B^0\rightarrow [K^-π^+]_DK^+π^-)/Γ(B^0\rightarrow [K^+π^-]_DK^+π^-)$ to be $(4.1 ^{+ 5.6 + 2.8}_{- 5.0 - 1.8}) \times 10^{-2}$, and set an upper limit of ${\cal R}_{DK^{*0}} < 0.16$ at the 95% confidence level.

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arXiv2012

Measurements of Branching Fractions and Time-dependent CP Violating Asymmetries in $B^{0} \to D^{(*)\pm}D^{\mp}$ Decays

We report measurements of branching fractions and time-dependent CP asymmetries in $B^{0} \to D^{+}D^{-}$ and $B^{0} \to D^{*\pm}D^{\mp}$ decays using a data sample that contains $(772 \pm 11)\times 10^6 B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We determine the branching fractions to be $\mathcal{B}(B^{0} \to D^{+}D^{-})=(2.12 \pm 0.16 \pm 0.18)\times 10^{-4}$ and $\mathcal{B}(B^{0} \to D^{*\pm}D^{\mp}=(6.14 \pm 0.29 \pm 0.50)\times 10^{-4}$. We measure CP asymmetry parameters $\mathcal{S}_{D^{+}D^{-}} = -1.06_{-0.14}^{+0.21} \pm 0.08$ and $\mathcal{C}_{D^{+}D^{-}} = -0.43 \pm 0.16 \pm 0.05$ in $B^{0} \to D^{+}D^{-}$ and $\mathcal{A}_{D^{*}D} = +0.06 \pm 0.05 \pm 0.02$, $\mathcal{S}_{D^{*}D} = -0.78 \pm 0.15 \pm 0.05$, $\mathcal{C}_{D^{*}D} = -0.01 \pm 0.11 \pm 0.04$, $Δ\mathcal{S}_{D^{*}D} = -0.13 \pm 0.15 \pm 0.04$ and $Δ\mathcal{C}_{D^{*}D} = +0.12 \pm 0.11 \pm 0.03$ in $B^{0} \to D^{*\pm}D^{\mp}$, where the first uncertainty is statistical and the second is systematic. We exclude the conservation of CP symmetry in both decays at equal to or greater than $4σ$ significance.

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arXiv2012

Search for Time-Dependent CPT Violation in Hadronic and Semileptonic B Decays

We report a new sensitive search for CPT violation, which includes improved measurements of the CPT-violating parameter z and the total decay-width difference normalized to the averaged width DeltaGamma_d/Gamma_d of the two Bd mass eigenstates. The results are based on a data sample of 535 x 10^6 BBbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. We obtain Re(z) = [+1.9 +/- 3.7 (stat) +/- 3.3 (syst)] x 10^{-2}, Im(z) = [-5.7 +/- 3.3 (stat) +/- 3.3 (syst)] x 10^{-3}, and DeltaGamma_d/Gamma_d = [-1.7 +/- 1.8 (stat) +/- 1.1 (syst)] x 10^{-2}, all of which are consistent with zero. This is the most precise single measurement of these parameters in the neutral B-meson system to date.

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arXiv2012

Measurement of $B^0 \to J/ψη^{(}{}'{}^{)}$ and Constraint on the $η-η'$ Mixing Angle

We measure the branching fractions of $B^{0} \to J/ψη^{(}{}'{}^{)}$ decays with the complete Belle data sample of $772 \times 10^{6}$ $B\bar{B}$ events collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The results for the branching fractions are: ${\cal B}(B^{0} \to J/ψη)=(12.3 \pm ^{1.8}_{1.7} \pm 0.7) \times 10^{-6}$ and ${\cal B}(B^{0} \to J/ψη') < 7.4 \times 10^{-6}$ at 90% confidence level. The $η-η'$ mixing angle is constrained to be less than $ 42.2^{\circ}$ at 90% confidence level.

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arXiv2012

Measurement of the CP-violation Parameter sin2$ϕ_1$ with a New Tagging Method at the $Υ(5S)$ Resonance

We report a measurement of the CP-violation parameter sin2$ϕ_1$ at the $Υ(5S)$ resonance using a new tagging method, called "$B$-$π$ tagging." In $Υ(5S)$ decays containing a neutral $B$ meson, a charged $B$, and a charged pion, the neutral $B$ is reconstructed in the $J/ψK_S^0$ CP-eigenstate decay channel. The initial flavor of the neutral $B$ meson at the moment of the $Υ(5S)$ decay is opposite to that of the charged $B$ and may thus be inferred from the charge of the pion without reconstructing the charged $B$. From the asymmetry between $B$-$π^+$ and $B$-$π^-$ tagged $J/ψK_S^0$ yields, we determine sin2$ϕ_1$ = 0.57 $\pm$ 0.58(stat) $\pm$ 0.06(syst). The results are based on 121 fb$^{-1}$ of data recorded by the Belle detector at the KEKB $e^+ e^-$ collider.

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arXiv2011

Observation of B- to pbar Lambda D0 at Belle

We study B- meson decays to pbar Lambda D(*)0 final states using a sample of 657 * 10^6 B Bbar events collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+ e- collider. The observed branching fraction for B- to pbar Lambda D0 is (1.43^ +0.28_-0.25 +- 0.18)*10^-5. with a significance of 8.1 standard deviations, where the uncertainties are statistical and systematic, respectively. Most of the signal events have the pbarLambda mass peaking near threshold. No significant signal is observed for B- to pbar Lambda D*0 and the corresponding upper limit on the branching fraction is 4.8 * 10^-5 at the 90% confidence level.

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arXiv2010

Belle II Technical Design Report

The Belle detector at the KEKB electron-positron collider has collected almost 1 billion Y(4S) events in its decade of operation. Super-KEKB, an upgrade of KEKB is under construction, to increase the luminosity by two orders of magnitude during a three-year shutdown, with an ultimate goal of 8E35 /cm^2 /s luminosity. To exploit the increased luminosity, an upgrade of the Belle detector has been proposed. A new international collaboration Belle-II, is being formed. The Technical Design Report presents physics motivation, basic methods of the accelerator upgrade, as well as key improvements of the detector.

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