Session B11: Heavy Flavor and Heavy Hadron Physics

The Belle II experiment: status and Physics prospects

The Belle II experiment is a substantial upgrade of the Belle detector and will operate at the SuperKEKB energy-asymmetric $e^+e^-$ collider. The detector construction has recently been completed and the accelerator is in its second phase of commissioning, with first collisions expected around the time of this conference. The design luminosity is $8 \times 10^{35}$ cm$^{-2}$s$^{-1}$ and the Belle II experiment aims to record 50 ab$^{-1}$ of data, a factor of 50 more than the Belle experiment. This large data set will be accumulated with low backgrounds and high trigger efficiencies in a clean $e^+e^－$ environment; this will allow to probe New Physics scales that are well beyond the reach of direct production at the LHC and will complement other searches that are currently ongoing or planned. This talk will review the present status of the experiment, and present an overview of the golden channels, their physics motivations, and the expected sensitivity.   

Mesurement of the $ D^{*+} - D^+ $ mass difference

We measure the mass difference, $\Delta m_+$, between the $D^{*}(2010)^+$ and the $D^+$, using the decay chain $D^{*}(2010)^+\to D^+ \pi^0 $ with $ D^+ \to K^- \pi^+ \pi^+$. The data were recorded with the BaBar detector at center-of-mass energies at and near the $\Upsilon(4S)$ resonance, and correspond to an integrated luminosity of approximately $468 \, \mbox{fb}^{-1}$. We measure $\Delta m_+ = \left(140\,601.0 \pm 6.8\,[{\rm stat}] \pm 12.9 \,[{\rm syst}]\right) \, \mbox{keV} $. We combine this result with a previous BaBar measurement of $\Delta m_0\equiv m(D^{*}(2010)^+) - m (D^0)$ to obtain $\Delta m_D = m(D^+) - m(D^0) = \left(4\,824.9 \pm 6.8\,[{\rm stat}] \pm12.9\,[{\rm syst}]\right) \, \mbox{keV}$ These results are compatible with and approximately five times more precise than previous Particle Data Group averages.   

Measurement of the Branching Fraction of anti-B0 to D*$+$ lepton anti-neutrino and Extraction of Vcb

We present a high precision measurement of the branching fraction of the anti-B0 to D*$+$ lepton anti-neutrino and extraction of Vcb using 429/fb of data collected with the BABAR detector at the PEP-II e$+$-e- collider at the SLAC National Accelerator Laboratory. The measurement is performed by partially reconstructed D*$+$ mesons only through the soft pion daughter of D*$+$.   

Combined measurement of CP violating angle $\beta$ by the BaBar and Belle experiments

We present a recent joint measurement of CP violating angle $\beta$ using 1.1 inverse attobarn data collected by BaBar and Belle experiments. This analysis is based on a time-dependent Dalitz plot analysis of $B \to \D^{(*)} h^{0}$ with $D \to K_{S}^{0} \pi^{+} \pi^{-}$ decays. These decays provide an experimental access to $\cos{2\beta}$ in addition to $\sin(2\beta)$, and can therefore resolve an ambiguity in the determination of the apex of the CKM Unitarity Triangle. As part of the analysis, a full Dalitz plot amplitude analysis of $D \to K_{S}^{0} \pi^{+} \pi^{-}$ is performed on a high-statistics charm data set. The first evidence for $\cos 2\beta >0$, an observation of CP violation, and the exclusion of the second solution of the CKM Unitarity Triangle of $\beta=(68.1 +- 0.7)^\circ$ at a significance of 7.3 standard deviations are reported.   

Charmless hadronic B decays from Belle.

We report measurements of the branching fraction and CP violation asymmetry in the B$^{\mathrm{+}} \quad \to $ K$^{\mathrm{+}}$ K$^{\mathrm{-}} \quad \pi ^{\mathrm{+}}$ and B$^{\mathrm{0}} \quad \to \quad \pi^{\mathrm{0}} \quad \pi ^{\mathrm{0}}$ decays using the data collected by the Belle experiment at the KEKB asymmetric-energy e$^{\mathrm{+}}$e$^{\mathrm{-}}$ collider.   

Search for Decay $B_s \to \eta^\prime$ $K_s$ in Belle Data

We search for the decay $B_s \to \eta^\prime K_s$ using $121.4 {\rm ~fb^{-1}}$ of data collected at the $\Upsilon(5S)$ resonance with the Belle detector at the KEKB asymmetric-energy electron-positron collider. This decay is suppressed in the Standard Model of particle physics and proceeds through $b \to u$ and penguin transitions, which are sensitive to new physics. The expected branching fraction in the Standard Model is approximately $2 \times 10^{-6}$. This decay has not been observed yet. We use Monte Carlo simulation to study Belle sensitivity to these decays. We report the current status of our investigations to provide the best sensitivity to discovering this decay in the existing data.   

Search for New Hadronic States $W_{bj}$ in Belle data

Recent discovery of $Z_b$ states at the Belle experiment implies possible existence of a new family of hadronic resonances including molecular states dubbed $W_{bj}$. We search for these states in radiative decays of $\Upsilon(5S)$ resonance in data collected with the Belle detector at the KEKB asymmetric-energy electron-positron collider. No such additional hadronic states in the $Z_b$ family have been observed yet. We use Monte Carlo simulation to study Belle sensitivity to $W_{bj}$ production. We report the current status of our investigations to provide the best sensitivity to this decay in the existing data and to create a roadmap for future discovery.   

Rare decays at LHCb

Rare decays are flavour changing current processes that allow sensitive searches for phenomena beyond the Standard Model (SM). In the SM, rare decays are loop-suppressed and new particles in SM extensions can give significant contributions. Of particular interest is the very rare decay Bs->mu mu which is in addition helicity suppressed and constitutes a powerful probe for new (pseudo) scalar particles. The LHCb experiment is ideally suited for the analysis of these decays due to its high trigger efficiency, as well as excellent tracking and particle identification performance. Recent results from the LHCb experiment in the area of rare decays are presented and their interpretation is discussed.