Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session C11: B Physics |
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Sponsoring Units: DPF Chair: Marina Artuso, Syracuse University Room: Roosevelt 3 |
Saturday, January 28, 2017 1:30PM - 1:42PM |
C11.00001: The Belle II Detector Leo Piilonen The Belle II detector is now under construction at the KEK laboratory in Japan. This project represents a substantial upgrade of the Belle detector (and the KEKB accelerator). The Belle II experiment will record 50~ab$^{-1}$ of data, a factor of 50 more than that recorded by Belle. This large data set, combined with the low backgrounds and high trigger efficiencies characteristic of an $e^+e^-$ experiment, should provide unprecedented sensitivity to new physics signatures in $B$ and $D$ meson decays, and in $\tau$ lepton decays. The detector comprises many forefront subsystems. The vertex detector consists of two inner layers of silicon DEPFET pixels and four outer layers of double-sided silicon strips. These layers surround a beryllium beam pipe having a radius of only 10~mm. Outside of the vertex detector is a large-radius, small-cell drift chamber, an "imaging time-of-propagation" detector based on Cerenkov radiation for particle identification, and scintillating fibers and resistive plate chambers used to identify muons. The detector will begin commissioning in 2017. [Preview Abstract] |
Saturday, January 28, 2017 1:42PM - 1:54PM |
C11.00002: Belle II grid computing : An overview of the distributed data management system. Vikas Bansal, Malachi Schram The Belle II experiment at the SuperKEKB collider in Tsukuba, Japan, will start physics data taking in 2018 and will accumulate 50/ab of e$+$e- collision data, about 50 times larger than the data set of the Belle experiment. The computing requirements of Belle II are comparable to those of a Run I LHC experiment. Computing at this scale requires efficient use of the compute grids in North America, Asia and Europe and will take advantage of upgrades to the high-speed global network. We present the architecture of data flow and data handling as a part of the Belle II computing infrastructure. [Preview Abstract] |
Saturday, January 28, 2017 1:54PM - 2:06PM |
C11.00003: The Belle II Physics Program Leo Piilonen The Belle II experiment at the asymmetric $e^+e^-$ SuperKEKB collider is a major upgrade of the Belle experiment, which ran at the KEKB collider at the KEK laboratory in Japan. The design luminosity of SuperKEKB is $8\times 10^{35}$~cm$^{-2}$\,s$^{-1}$, which is about 40 times higher than that of KEKB. The expected integrated luminosity of Belle II is 50~ab$^{-1}$ in five years of running. The experiment will focus on searches for new physics beyond the Standard Model via high precision measurements of heavy flavor decays, and searches for rare signals. To reach these goals, the accelerator, detector, electronics, software, and computing systems are all being substantially upgraded. In this talk we discuss the physics program and the expected sensitivity to new physics of the Belle II data set. [Preview Abstract] |
Saturday, January 28, 2017 2:06PM - 2:18PM |
C11.00004: Belle II Early Physics Program Zachary Stottler The Belle II experiment at the SuperKEKB collider is a major upgrade of the KEK ``$B$ factory'' facility in Tsukuba, Japan. First beams are planned for early 2017 and first physics data will be recorded in the middle of 2018 during Phase 2 commissioning, while the Belle II detector is still missing its vertex detector system. In this talk we describe the physics program for this early data. The program will focus on bottomonium spectroscopy at different center-of-mass energies, in particular at the $\Upsilon(3S)$ and $\Upsilon(6S)$ resonances, amongst other energy points. [Preview Abstract] |
Saturday, January 28, 2017 2:18PM - 2:30PM |
C11.00005: Belle II sensitivity to missing energy decays Vipin Gaur The Belle II experiment at the SuperKEKB collider is a major upgrade of the KEK ``$B$ factory'' facility in Tsukuba, Japan. The machine is designed for an instantaneous luminosity of $8\times 10^{35}$~cm$^{-2}$\,s$^{-1}$, and the experiment is expected to accumulate a data sample of about 50 ab$^{-1}$ in five years of running. With this amount of data, decays sensitive to physics beyond the Standard Model can be studied with unprecedented precision. One promising set of modes are physics processes with missing energy such as $B^+\to\tau^+\nu$, $B\to D^{(*)}\tau\nu$, and $B\to K^{(*)}\nu\bar\nu$ decays. The Belle II data also allows searches for the dark photon, the gauge mediator of a hypothetical dark sector, which has received much attention in the context of dark matter models. [Preview Abstract] |
Saturday, January 28, 2017 2:30PM - 2:42PM |
C11.00006: Belle II sensitivity to $B\rightarrow K\nu\bar{\nu}$ decays Vipin Gaur The $B\rightarrow K^{(*)}\nu\bar{\nu}$ decay provides one of the cleanest experimental probes of the flavor-changing neutral current process $b\rightarrow s\nu\bar{\nu}$, which is sensitive to physics beyond the Standard Model. However, the missing energies of the two neutrinos in the final state makes the measurement challenging and requires full reconstruction of the spectator $B$ meson in $e^+ e^−\rightarrow\Upsilon(4S)\rightarrow\overline{B}B$ events. Observation of the $B\rightarrow K^{(*)}\nu\bar{\nu}$ decay will become possible with the large data set to be collected by the upgraded Belle II experiment running at the Super-KEKB accelerator in Japan. A challenge of this analysis will be understanding and suppressing backgrounds. This talk discusses such backgrounds and the expected sensitivity of Belle II for this rare decay. [Preview Abstract] |
Saturday, January 28, 2017 2:42PM - 2:54PM |
C11.00007: Search for $B \to \phi \phi K$ decays at Belle Vipin Gaur We report measurements of the branching fraction and CP violation asymmetry in $B \to \phi \phi K$ decays using the $e^+ e^-$ collision data that correspond to 772 million $B\bar{B}$ pairs collected by the Belle experiment at KEK. These decays are mediated by the FCNC transition $b \to s \bar{s} s$. It is suggested that one can observe large CP violation in the decays owing to the interference of potential non-SM amplitudes appearing in the quantum loop with the $b \to c$ tree-level transition of $B \to \eta_c K$, $\eta_c \to \phi \phi$. The results supersede the earlier Belle's measurement with nine times larger statistics and refined analysis techniques. [Preview Abstract] |
Saturday, January 28, 2017 2:54PM - 3:06PM |
C11.00008: Search for $B^+ \to K_S K_S h^+$ decays at Belle Vipin Gaur We present updated measurements of charmless decays of charged B mesons to the three-body final states of $K_S K_S K^+$ and $K_S K_S \pi^+$, based on a data sample containing $770 \times 10^6$ $B\bar{B}$ events. The data were recorded with the Belle detector operating near the $\Upsilon(4S)$ resonance at the KEKB asymmetric-energy $e^+ e^-$ collider. The $B^+ \to K_S K_S K^+$ and $B^+ \to K_S K_S \pi^+$ decays proceed via the $b \to s$ and $b \to d$ flavor-changing neutral current (FCNC) transitions, respectively, providing a good probe for new physics beyond the standard model (SM). We report the results on the branching fractions and direct CP asymmetries for both the decay channels. [Preview Abstract] |
Saturday, January 28, 2017 3:06PM - 3:18PM |
C11.00009: Recent Results of Bottomonium Spectroscopy in Radiative $\Upsilon(2S)$ Decays at Belle Zachary Stottler We report on the recent results of a search for $\Upsilon(2S)\rightarrow (b\bar{b})\gamma$ decays. We characterize the properties of $\chi_{bJ}(1P)$ $(J=0,1,2)$ mesons, which are reconstructed from 74 hadronic final states containing charged and neutral pions, kaons, protons. In total, we observe 41 modes with a significance at or above $5\sigma$, many of which are first observations. Our results are based on an integrated luminosity of $24.7fb^{-1}$ of $e^+e^-$ collision data recorded by the Belle detector at the $\Upsilon(2S)$ resonance, corresponding to $(157.8\pm3.6)\times10^6$ $\Upsilon(2S)$ events. [Preview Abstract] |
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