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Search Results: 1 - 10 of 12414 matches for " for the Belle Collaboration "
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Improved Measurement of Inclusive Radiative B-meson decays
Belle Collaboration
Physics , 2008, DOI: 10.1063/1.3051954
Abstract: We report a fully inclusive measurement of the flavor changing neutral current decay $B\to X_s\gamma$ in the energy range $1.7 \GeV\le E^\mathrm{c.m.s}_\gamma\le 2.8 \GeV$, covering 97% of the total spectrum, where c.m.s is the center of mass system. Using $605\ifb$ of data, we obtain in the rest frame of the $B$-meson ${\mathcal B}(B\to X_s\gamma : E^B_\gamma>1.7 \mathrm{GeV})= (3.31 \pm 0.19 \pm 0.37 \pm 0.01)\times 10^{-4}$, where the errors are statistical, systematic and from the boost correction needed to transform from the rest frame of the $\Upsilon(4S)$ (c.m.s) to that of the $B$-meson, respectively. We also measure the first and second moments of the photon energy spectrum as functions of various energy thresholds, which extend down to $1.7 \GeV$. The results are preliminary.
Measurement of $y_{CP}$ in $D^0$ meson decays to the $K_S^0K^+K^-$ final state
The Belle Collaboration
Physics , 2009, DOI: 10.1103/PhysRevD.80.052006
Abstract: We present a measurement of the $D^0$-$\overline{D}{}^0$ mixing parameter $y_{CP}$ using a flavor-untagged sample of $D^0\to K_S^0K^+K^-$ decays. The measurement is based on a 673 fb$^{-1}$ data sample recorded with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. Using a method based on measuring the mean decay time for different $K^+K^-$ invariant mass intervals, we find $y_{CP} = (+0.11\pm 0.61 ({\rm stat.})\pm 0.52 (\rm syst.))%$.
Observation of the decay $B_s^0\to J/ψη$ and Evidence for $B_s^0\to J/ψη'$
The Belle Collaboration
Physics , 2009,
Abstract: We report the first observation of $B_s^0\to J/\psi\eta$ and evidence for $B_s^0\to J/\psi\eta'$. These results are obtained from $23.6 \mathrm{fb}^{-1}$ of data collected at the $\Upsilon(5S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. We measure the branching fractions $\mathcal{B}(B_s^0\to J/\psi\eta)= (3.32 \pm 0.87(\mathrm{stat.})^{+0.32}_{-0.28}(\mathrm{syst.}) \pm 0.42(f_s))\times 10^{-4}}$ with a significance of $7.3 \sigma$, and $\mathcal{B}(B_s^0\to J/\psi\eta')= (3.1 \pm 1.2(\mathrm{stat.})^{+0.5}_{-0.6}(\mathrm{syst.}) \pm 0.38(f_s))\times 10^{-4}$ with a significance of $3.8 \sigma$.
Measurement of the branching fractions for $B^0 \to D_s^{*+}π^-$ and $B^0 \to D_s^{*-}K^+$ decays
Belle Collaboration
Physics , 2009,
Abstract: We present a study of $B^0 \to D_s^{*+}\pi^-$ and $B^0 \to D_s^{*-}K^+$ decays based on a sample of $657 \times 10^6$ $B\bar{B}$ events collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We measure the branching fractions to be $\mathcal{B}(B^0 \to D_s^{*+} \pi^-) = (1.75 \pm 0.34 \pm 0.17 \pm 0.11) \times 10^{-5}$ and $\mathcal{B}(B^0 \to D_s^{*-} K^+) = (2.02 \pm 0.33 \pm 0.18 \pm 0.13) \times 10^{-5}, with significances of 6.1 and 8.0 standard deviations, respectively. The first uncertainty is statistical, the second is due to the experimental systematics, and the third is from uncertainties in the $D_s^+$ decay branching fractions. From our measurements, we obtain the most precise determination so far of $R_{D^*\pi}$, where $R_{D^*\pi}$ is the ratio between amplitudes of the doubly Cabibbo-suppressed decay $B^0 \to D^{*+}\pi^-$ and the Cabibbo favored $B^0 \to D^{*-}\pi^+$ decay.
Measurement of the angle φ_3 with Dalitz analysis of three-body D^0 decay from B\to D^0 K process
Belle Collaboration
Physics , 2003,
Abstract: A new method to measure the angle $\phi_3$ of the CKM unitarity triangle using a Dalitz analysis of the three-body decay of the $D^0$ meson from the $B\to D^0 K$ process has been introduced recently. The method employs the interference between $D^0$ and $\bar{D^0}$ to extract both the weak and strong phases. We present a study of statistical and systematic errors of this method using Monte Carlo simulation. A fit of the $D^0$ Dalitz distribution has been performed based on a 140 fb$^{-1}$ sample collected by the Belle detector. We observe the indication of a CP asymmetry with the significance of 2.4 standard deviations. The 90% confidence interval obtained for the $\phi_3$ value is $61^{\circ}<\phi_3<142^{\circ}$.
Evidence for the decay $Υ(4S) \to Υ(1S) π^{+} π^{-} $
Belle Collaboration
Physics , 2005,
Abstract: A study of transitions between $\Upsilon$ states with the emission of charged pions using 398 fb$^{-1}$ of data collected with the Belle detector at the KEKB asymmetric energy $e^+e^-$ collider is presented. A clear peak from the decay $\Upsilon(1S)\to\mu^+\mu^-$ is observed in the invariant mass distribution of $(\mu^+ \mu^-)$ pairs from the $(\mu^+ \mu^- \pi^+ \pi^- X)$ event sample. The mass difference distribution ($M_{\mu^+\mu^-\pi^+\pi^-}-M_{\mu^+\mu^-}$) for $M_{\mu^+\mu^-}$ from the $\Upsilon(1S)$ mass region has two peaks from $\Upsilon(2S,3S)\to \Upsilon(1S)\pi^+\pi^-$ decays, with no background. A third peak at $\Delta M = (1119.0\pm 1.4)$~MeV/$c^2$ can be interpreted as evidence of a signal from the decay $\Upsilon(4S)\to \Upsilon(1S)\pi^+\pi^-$ with a subsequent $ \Upsilon(1S) \to \mu^+ \mu^-$ transition. This is the first example of a non-$B \bar{B}$ decay of the $\Upsilon(4S)$ resonance. The preliminary estimated branching fraction is equal to $\mathcal{B}(\Upsilon(4S)\to \Upsilon(1S)\pi^+\pi^-) = (1.1 \pm 0.2(\mathrm{stat.}) \pm 0.4(\mathrm{sys.}))\times 10^{-4}.$
Study of X(3872) in $B$ meson decays
Belle collaboration
Physics , 2008,
Abstract: We present results on the X(3872), produced in $B^+ \to X(3872) K^+$ and $B^0 \to X(3872) K^0_S$ decays where $X(3872) \to J/\psi \pi^+ \pi^-$. We report the first statistically significant observation of $B^0 \to X(3872) K^0_S$ and measure the ratio of branching fractions to be $\frac{{\cal B}(B^0 \to X(3872)K^0)} {{\cal B}(B^+ \to X(3872)K^+)} = 0.82 \pm 0.22 \pm 0.05$, consistent with unity. The mass difference between the X(3872) states produced in $B^+$ and $B^0$ decay is found to be $\delta M \equiv M_{XK^+} - M_{XK^0} = (+0.18 \pm 0.89 \pm 0.26)$ MeV/$c^2$, consistent with zero. In addition, we search for the X(3872) in the decay $B^0 \to X(3872)K^+\pi^-$, $X(3872) \to J/\psi \pi^+ \pi^-$. We measure ${\cal B}(B^0 \to X(3872) (K^+ \pi^-)_{NR}) \times {\cal B}(X(3872) \to J/\psi \pi^+ \pi^-) = (8.1 \pm 2.0 ^{+1.1}_{-1.4})\times 10^{-6}$ and we set the 90% C.L. limit, ${\cal B}(B^0 \to X(3872)K^{*}(892)^0) \times {\cal B}(X(3872) \to J/\psi \pi^+ \pi^-) < 3.4 \times 10^{-6}$. The analysis is based on a 605 fb$^{-1}$ data sample collected at the $\Upsilon(4S)$ with the Belle detector at the KEKB collider.
Moments of the photon energy spectrum from $B\to X_s γ$ decays measured by Belle
Belle Collaboration
Physics , 2005,
Abstract: We report preliminary measurements of the first (mean) and second moment (variance) of the inclusive photon energy spectrum in $B\to X_s\gamma$ decays, for threshold values of the photon energy in the range 1.8--2.3 GeV as measured in the rest frame of the $B$-meson. These results are obtained from the Belle measurement of the spectrum, which used a data set consisting of 152 million $B\bar{B}$ pairs collected by the Belle detector at the KEKB asymmetric-energy electron-positron collider operated on the $\Upsilon(4S)$ resonance.
Measurement of D0 -> pilnu (Klnu) and their form factors
Belle Collaboration
Physics , 2005,
Abstract: Using a data sample of 282 1/fb collected by the Belle experiment at the KEKB e+e- collider, we study D0 -> pilnu and D0 -> Klnu decays (l = mu,e) in e+e- annihilation. We identify D* -> D0pi decays by using the mass of the system recoiling against a fully reconstructed tag-side D* or D meson, allowing for additional primary mesons from fragmentation. Using a novel global reconstruction method that provides very good resolution in neutrino momentum and in q^2 = (p_l+p_nu)^2, we reconstructed D0 -> pilnu and D0 -> Klnu decays. From these events we measured the branching fraction ratios BR(D0 -> pienu)/BR(D0 -> Kenu) = 0.0809 +- 0.0080 +- 0.0032$ and BR(D0 -> pimunu)/BR(D0 -> Kmunu) = 0.0677 +- 0.0078 +- 0.0047, and the semileptonic form factor ratio f+(D0 -> pilnu})^2/f+(D0 -> Klnu})^2|Vcd|^2/|Vcs|^2|_{q^2=0} = 0.041 +- 0.003 +- 0.004, where the errors are statistical and systematic, respectively.
Study of the Y (4260) resonance in e+e- collisions with initial state radiation at Belle
Belle Collaboration
Physics , 2006,
Abstract: We present a study of Y(4260) properties using the initial-state radiation process e^+e^- -> gamma_{ISR} Y(4260). The Y(4260) resonance is reconstructed in the pi^+ pi^- J/\psi decay mode, using data collected by the Belle detector at the KEKB e^+e^- collider. We find a significant signal with a central mass value of (4295 +-10 +10 -3) MeV/c^2 and a width of (133 +-26 +13 -6) MeV/c^2. We find Gamma_{ee}.B(Y(4260) -> pi^+ pi^- J/\psi) = (8.7 +- 1.1 +0.3 -0.9) eV. These results are preliminary.
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