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We report a first measurement of inclusive B -> X_s eta decays, where X_s is a charmless state with unit strangeness. The measurement is based on a pseudo-inclusive reconstruction technique and uses a sample of 657 x 10^6 BB-bar pairs accumulated with the Belle detector at the KEKB e^+e^- collider. For M_{X_s} < 2.6 GeV/c^2, we measure a branching fraction of (26.1 +/- 3.0 (stat) +1.9 -2.1 (syst) +4.0 -7.1 (model)) x 10^-5 and a direct CP asymmetry of A_{CP} = -0.13 +/- 0.04 +0.02 -0.03. Over half of the signal occurs in the range M_{X_s} > 1.8 GeV/c^2.
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We report measurements of isospin asymmetry $Delta_{0-}$ and difference of direct $CP$ asymmetries $Delta A_{CP}$ between charged and neutral $B to X_s gamma$ decays. This analysis is based on the data sample containing $772 times 10^6 Bbar{B}$ 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 $Delta_{0-} = bigl[-0.48 pm 1.49 {rm (stat.)} pm 0.97 {rm (syst.)} pm 1.15 {(f_{+-}/f_{00})}bigr]$% and $Delta A_{CP} = bigl[+3.69 pm 2.65 {rm (stat.)} pm 0.76{rm (syst.)}bigr]$%, where the last uncertainty for $Delta_{0-}$ is due to the uncertainty on the production ratio of $B^+B^-$ to $B^0bar{B}^0$ in $Upsilon(4S)$ decays. The measured value of $Delta_{0-}$ is consistent with zero, allowing us to constrain the resolved photon contribution in the $B to X_s gamma$, and improve the branching fraction prediction. The result for $Delta A_{CP}$ is consistent with the prediction of the SM. We also measure the direct $CP$ asymmetries for charged and neutral $B to X_s gamma$ decays. All the measurements are the most precise to date.
We use 772$times 10^6$ $B bar{B}$ meson pairs collected at the $Upsilon(4S)$ resonance with the Belle detector to measure the branching fraction for $bar{B} rightarrow X_s gamma$. Our measurement uses a sum-of-exclusives approach in which 38 of the hadronic final states with strangeness equal to $+1$, denoted by $X_s$, are reconstructed. The inclusive branching fraction for $M_{X_s}<$ 2.8 GeV/$c^2$, which corresponds to a minimum photon energy of 1.9 GeV, is measured to be ${cal B}(bar{B} rightarrow X_s gamma)=(3.51pm0.17pm0.33)times10^{-4}$, where the first uncertainty is statistical and the second is systematic.
We report a fully inclusive measurement of the flavour changing neutral current decay b->s gamma in the energy range 1.8 GeV < E* < 2.8 GeV, covering 95% of the total spectrum. Using 140 fb^-1 we obtain BF(b->s gamma)= 3.55 +/- 0.32 +0.30-0.31 +0.11-0.07, where the errors are statistical, systematic and from theory corrections. We also measure the first and second moments of the photon energy spectrum above 1.8 GeV and obtain <E> = 2.292 +/- 0.026 +/- 0.034 GeV and <E^2>-<E>^2 = 0.0305 +/- 0.0074 +/- 0.0063 GeV^2, where the errors are statistical and systematic.
The first measurements of differential branching fractions of inclusive semileptonic ${B to X_u , ell^+, u_{ell}}$ decays are performed using the full Belle data set of 711 fb$^{-1}$ of integrated luminosity at the $Upsilon(4S)$ resonance and for $ell = e, mu$. Differential branching fractions are reported as a function of the lepton momentum, the four-momentum-transfer squared, light-cone momenta, the hadronic mass, and the hadronic mass squared. They are obtained by subtracting the backgrounds from semileptonic ${B to X_c , ell^+, u_{ell}}$ decays and other processes, and corrected for resolution and acceptance effects. The measured distributions are compared to predictions from inclusive and hybrid ${B to X_u , ell^+, u_{ell}}$ calculations.
The $b rightarrow s gamma$, $b rightarrow d gamma$ and $b rightarrow s ell^+ ell^-$ processes are allowed at higher order via the electroweak loop or box diagrams in the Standard model. It is sensitive probe to search for new physics beyond the Standard model because new particles might enter in the loop. We present preliminary results of branching fraction of the $bar{B} rightarrow X_s gamma$, $CP$ asymmetry in the $bar{B} rightarrow X_{s+d} gamma$, and the forward-backward asymmetry in the $bar{B} rightarrow X_s ell^+ ell^-$. The results are based on a data sample containing $772 times 10^6 Bbar{B}$ pairs recorded at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider.
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