Session H7: B Factory Radiative Decays, X(3872), Direct BR

Radiative B Decays at Belle

We present recent studies of radiative $B$ decays at the Belle experiment. These include the branching fraction measurements of $B \to K\,\eta\,\gamma$, $B \to K_1(1270)\,\gamma$ and $B \to X_s\,\ell^+\,\ell^-$, the CP asymmetry in $B \to X_s\,\gamma$, the forward-backward asymmetry for $B \to K^{*}\,\ell^+\,\ell^-$, the photon energy spectrum in $b \to s\,\gamma$, and the search for $b \to d\,\gamma$.   

BaBar Searches for Rare Radiative Penguin Decays of B Mesons

We present searches for rare radiative penguin decays of the $B$ meson: $B\rightarrow \rho \gamma$, $B\rightarrow \gamma\gamma$, and $B\rightarrow D^*\gamma$. Candidate events are identified from exclusively reconstructed combinations of $D^*$, $\rho$, and photon candidates. $B\rightarrow \rho \gamma$ is sensitive to the CKM-suppressed $b\rightarrow d\gamma$ quark decay process, the rate of which is directly dependent upon the CKM matrix element $|V_{td}|$. $B\rightarrow \gamma\gamma$ and $B\rightarrow D^* \gamma$ proceed through weak interaction of the constituent quarks of the $B$ meson and could receive enhancement of the decay rate from new physics at the electroweak scale. The data samples studied comprise up to 230 million $\Upsilon(4S)\rightarrow B \overline B$ decays collected with the BaBar detector at the PEP-II $e^+e^-$ storage ring.   

Study of $X(3872)\rightarrow J/\psi\pi\pi$ in $B\rightarrow X(3872)K^-$ and $B\rightarrow X(3872)K_S^0$

We search for a charged partner of the $X(3872)$ in the decay $B^-\rightarrow X^- K$, $X^-\rightarrow J/\psi \pi^- \pi^0$, using 234 million $B \bar B$ events collected at the $\Upsilon(4S)$ resonance with the BaBar detector at the PEP-II $e^+ e^-$ asymmetric-energy storage ring. The resulting product branching fraction upper limits are $BR(B^0\to X^{-} K^+$, $X^-\rightarrow J/\psi \pi^-\pi^0) < 5.4 \times 10^{-6}$ and $BR(B^-\to X^{-}\overline{K}_0$, $X^- \rightarrow J/\psi\pi^-\pi^0) < 22 \times 10^{-6}$ at the $90\%$ confidence level. In addition, we update the previous BaBar result on $B^-\rightarrow X(3872)K^-$, $X(3872)\rightarrow J\psi\pi^+\pi^-$ with increased statistics and extend the search to include $B^0\rightarrow X(3872) K_S^0$ as well as $X(3872)\rightarrow J\psi\pi^0\pi^0$.   

Search for $X\to J/\psi \omega$ in the B decays, $B\to XK$

There is still much uncertainty as to the nature of the X(3872) observed by Belle in 2003. It may possibly be a charmonium state, a bound state of charmed mesons or a hybrid state of gluons and charm quarks. The decay $X\rightarrow J/\phi \omega$ might be a favored decay if the X(3872) is actually a bound state of two charmed mesons. We report a search for $X(3872) \rightarrow J/\psi \omega$ in $B \rightarrow XK$ decays using 205 $fb^{-1}$ collected on the $\Upsilon (4S)$ resonance by the BaBar detector at the Pep-II asymmetric e+e- storage ring.   

BaBar Measurements of the Exclusive Radiative Penguin Decays $B \rightarrow K^*\gamma$ and $B \rightarrow K\pi\pi\gamma$

We present measurements of exclusive radiative penguin decays of the $B$ meson, $B\rightarrow K^* \gamma$ and $B\rightarrow K\pi\pi\gamma$. Measurements include the branching fractions, CP asymmetries, and hadronic mass distributions of events exclusively reconstructed from various combinations of kaon, pion, and photon candidates. The CP asymmetries are sensitive to new physics at the electroweak scale, and the branching fractions and hadronic mass distribution allow for the evaluation of the contribution of various kaon resonances to the $b \rightarrow s \gamma$ quark decay process. The data samples studied comprise 230 million $\Upsilon(4S)\rightarrow B \overline B$ decays collected with the BaBar detector at the PEP-II $e^+e^-$ storage ring.   

BaBar Measurement of the branching fraction, photon energy spectrum, and direct $\it{CP}$ asymmetry in inclusive $b\to s \gamma$ decays

We present measurements of the radiative penguin quark decay $b\rightarrow s \gamma$. Measurements include the branching fraction, photon spectrum, and CP asymmetry of an inclusive sample of $B$ mesons decaying to high energy photons. The branching fraction and CP asymmetry are highly sensitive to new physics at the electroweak scale, and the photon spectral shape allows for precision studies of the strong interactions of the $b$ quark within the $B$ meson bound state. The data samples studied comprise 89 million $\Upsilon(4S)\rightarrow B \overline B$ decays collected with the BaBar detector at the PEP-II $e^+e^-$ storage ring.   

BaBar Measurements of the Rare Flavor-Changing Neutral Current Decay $b \rightarrow s \ell^+\ell^-$

We present measurements of the flavor-changing neutral current quark decay $b\rightarrow s \ell^+\ell^-$, where $\ell^+\ell^-$ is either an $e^+e^-$ or $\mu^+\mu^-$ pair. Measurements include branching fractions and asymmetries of the inclusive $b \rightarrow s \ell^+\ell^-$ process in $B$ meson decays as well as specific studies of the exclusive decays $B\rightarrow K\ell^+\ell^-$ and $B\rightarrow K^*\ell^+\ell^-$. These decays are highly suppressed in the Standard Model, and they are sensitive to contributions from new particles in the intermediate state. The data samples studied comprise 230 million $\Upsilon(4S)\rightarrow B \overline B$ decays collected with the BaBar detector at the PEP-II $e^+e^-$ storage ring.   

Search for $B^+ \to \ell^+ \nu \gamma$ decays at Belle

We present a search for $B^+ \to \ell^+ \nu \gamma$ decays ($\ell =e$ or $\mu$) in a sample of $e^+ e^-$ collisions with an integrated luminosity of 140/fb recorded at the $\Upsilon(4S)$ resonance using the KEKB asymmetric $B$ factory. The data are collected with the Belle detector, a multi-purpose magnetic spectrometer with near $4\pi$ solid angle coverage for charged and neutral particles.   

Direct Measurement of the Branching Fraction of \boldmath{$\Upsilon(4S) \rightarrow B^0 \bar {B}^{0}$}

We report the first direct measurement of the branching fraction of $\Upsilon(4S) \rightarrow B^0 \bar {B}^{0}$ carried out with a data sample of 82~fb$^{-1}$ collected at the $\Upsilon(4S)$ resonance with the BaBar detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. Our result is obtained with a double-tag technique and does not depend on branching fractions of the $\bar {B}^{0}$ and the $D^{*+}$ decays, on the simulated reconstruction efficiency, on the ratio of the charged and neutral $B$ meson lifetimes, or on the assumption of isospin symmetry.