Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session K20: Weak decays of heavy quarksLive
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Sponsoring Units: DPF Chair: Sheldon Stone, Syracuse University |
Sunday, April 18, 2021 1:30PM - 1:42PM Live |
K20.00001: Semileptonic b decays at LHCb Mariia Poliakova Semileptonic B decays provide a powerful tool to understand the Standard Model and look for new physics by studying lepton flavor universality, measuring CKM matrix elements Vcb and Vub and measuring QCD form factors. LHCb has a uniquely large sample of B hadrons allowing high precision measurements in this area and probing new decay modes. This talk reports the most recent results on semileptonic measurements at the LHCb experiment. [Preview Abstract] |
Sunday, April 18, 2021 1:42PM - 1:54PM Live |
K20.00002: Variations to the Z-expansion of the Form Factors of the Decay of B Mesons Daniel Simons, Erik Gustafson, Yannick Meurice We studied the decay rate of the particle decay $B \rightarrow D l \nu_l$ using data collected from the Belle Collaboration. In order to analyze this decay rate, two different form factor parametrizations of the decay rate were used, the CLN (Caprini, Lellouch, and Neubert) parametrization and the BGL (Boyd, Grinstein, and Lebed) parametrization. These form factors are functions of the hadronic recoil variable $w$ and contain free parameters which are the interest of this project. One of the goals of this project was to fit these form factors to the Belle data in the lattice regime, considering only the data points where $w <$ $\sim 1.3$, so that we can predict what the larger $w$ region should look like. We hope to in the future be able to use Monte Carlo simulations to extract values of the form factors, however these simulations are only able to reliably extract these values inside of the lattice regime. By fitting only the low $w$ values, we are able to get an idea of what the larger $w$ region should look like and how many data points are needed in the fit to accurately predict the larger $w$ region. Our recent progress extends this idea to the more complex particle decay $B \rightarrow D^* l \nu_l$ and we look at incorporating the Z-expansion into public event generators. [Preview Abstract] |
Sunday, April 18, 2021 1:54PM - 2:06PM Live |
K20.00003: Measurement of $B \rightarrow X_{c} l \nu$ branching fractions using Belle data Frank Meier Semileptonic decays of $B$ mesons are an important tool for precision measurements of Cabibbo-Kobayashi-Maskawa matrix elements and precision tests of the electroweak sector of the standard model. For the $B\rightarrow X_c l\nu$ branching fraction there is a significant gap between the inclusive measurement and the sum of the measurements of the exclusive channels. The dominant contributions $B\rightarrow D^{*} l\nu$ and $B\rightarrow D l\nu$ are precisely known but the branching fractions of $B\rightarrow D^{**} l\nu$ have higher uncertainties. Here, the $D^{**}$ is an orbitally excited charmed meson, which can decay into $D^*\pi$ and $D\pi$. The decay $B\rightarrow D^{(*)}\pi\pi l\nu$ with two bachelor pions in the final state has so far even only been observed by the Babar collaboration. Over the course of about 10 years the Belle collaboration has recorded about 772 million $B\overline{B}$ pairs produced in $e^+e^-\rightarrow\Upsilon(4S)$ at the KEKB asymmetric-energy $e^+e^-$ collider. The status of the measurement of the branching fraction of $B\rightarrow D^{(*)} \pi l\nu$ as well as $B\rightarrow D^{(*)} \pi\pi l\nu$ using the full Belle data sample will be presented including an analysis of the invariant $D^{(*)} \pi$ mass distribution. [Preview Abstract] |
Sunday, April 18, 2021 2:06PM - 2:18PM Live |
K20.00004: Direct CP Violation in the Decay $B^{+} \rightarrow K^{+} \pi^{0}$ at LHCb Zishuo Yang Measurements of CP asymmetries in B-meson systems can be a powerful way to probe for physics beyond the Standard Model. A new measurement, the most precise to date, of the direct CP asymmetry in the decay $B^{+} \rightarrow K^{+} \pi^{0}$ has been performed at LHCb. This direct CP asymmetry is a key input to the studies of a long-standing anomaly in B-meson decays, known as the $K\pi$ puzzle. I will present the new result, which is consistent with the previous measurements and significantly strengthens the anomaly. [Preview Abstract] |
Sunday, April 18, 2021 2:18PM - 2:30PM Live |
K20.00005: Search for New Decays of $B_s$ Mesons to $\eta^\prime$ at Belle Tong Pang, Vladimir Savinov We search for charmless two-body decays of $B_s$ mesons to $\eta^\prime$ and report the results obtained using the full $\Upsilon(5S)$ Belle data sample. These decays are sensitive to contributions from BSM amplitudes and, with larger statistics, could be used to search for new sources of CP violation. We discuss the analysis optimization strategy, background suppression, using data-based calibration methods and report the final results. We elaborate on enigmatic role of the $\eta^\prime$ in $B$ decays and beyond. [Preview Abstract] |
Sunday, April 18, 2021 2:30PM - 2:42PM Live |
K20.00006: Measurement of the branching fraction and a search for CP violation in B to phi phi K. Vipin Gaur We report the final results of the measurement of the branching fraction and CP violation in B to phi phi K decays based on a data sample collected with the Belle detector at the KEKB asymmetric-energy e$+$ e- collider. [Preview Abstract] |
Sunday, April 18, 2021 2:42PM - 2:54PM Live |
K20.00007: Analysis of Decays $B \to \pi^+\pi^-\pi^0$ With Full Belle Data Sample Erfei Wang, Vladimir Savinov We report the current status of a time-dependent Dalitz analysis of the decays $B \to \pi^+\pi^-\pi^0$ with the full Belle data sample. In this analysis we measure the CKM angle $\phi_2$ ($\alpha$) and search for BSM sources of CP violation. We discuss the sources of systematic uncertainties including the measurement of $\pi^0$ reconstruction efficiency as the function of $\pi^0$ momentum which is important to understand for extracting the final results from the data. [Preview Abstract] |
Sunday, April 18, 2021 2:54PM - 3:06PM Live |
K20.00008: Measurement of the CKM matrix elements $|V_{ub}|/|V_{cb}| $ from semileptonic $B_s$-meson decays at LHCb Svende Braun The Cabibbo-Kobayashi-Maskawa matrix elements $|V_{ub}|$ and $|V_{cb}|$ describe the coupling between beauty to up and beauty to charm quarks in the electroweak interaction, respectively. They can be measured using semileptonic $B$-decays which are either fully reconstructed or in an inclusive way. A discrepancy exceeding 3 standard deviations is observed which is a long-standing puzzle of flavor physics. I will discuss a new measurement made by LHCb using the decay $B_s^0 \to K^- \mu^+ \nu_{\mu}$, which is observed for the first time and can be used together with its normalization channel $B_s^0 \to D_s^- \mu^+ \nu_{\mu}$ to extract $|V_{ub}|/|V_{cb}|$ in different regions of the momentum transfer $q^2$ using theoretical form factor predictions. [Preview Abstract] |
Sunday, April 18, 2021 3:06PM - 3:18PM Live |
K20.00009: Search for New Decays of $B$ mesons to Charmed Baryons at Belle Mark Farino, Vladimir Savinov We search for new Cabibbo-suppressed decays of $B$ mesons to neutral charmed baryons and report the current status of the analysis based on the full Belle data sample. These decays could be used to validate the models describing hadronic dynamics and, with a larger data sample,to search for baryon number violation arising via the charmed baryons oscillations. We discuss the analysis procedure, background suppression optimization, the approach used to separate between similar channels, and present preliminary results based on data. [Preview Abstract] |
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