Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session T10: Collider and BSM IV |
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Sponsoring Units: DPF Chair: Jeremy Love, Argonne National Laboratory Room: Sheraton Governor's Square 12 |
Monday, April 15, 2019 3:30PM - 3:42PM |
T10.00001: Charmless hadronic B decays from Belle Vipin Gaur We report Belle preliminary results of the study of B0 -> ηη, B0 -> K-π+KS0 and B± -> KS0KS0h± (h=K,π) based on data samples collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider |
Monday, April 15, 2019 3:42PM - 3:54PM |
T10.00002: Using Ξ(1820) baryons to test for parity doubling at ALICE Corey James Myers We investigate the production of Ξ(1820) baryons in pp collisions at 13 TeV by reconstructing their Λ-Κ decays. Recent lattice calculations on parity doubling indicate that the masses of negative-parity particles, such as Ξ(1820), may decrease at high temperatures, while the masses of positive-parity partners, i.e. the Ξ(1530), do not. Furthermore, the lifetime of the Ξ(1820) is short enough that it may be suppressed in high-multiplicity collisions, as has been observed for Λ(1520), K*(892), and ρ(770). Studying Ξ(1820) also allows us to better understand the spectrum of excited hyperon states, with implications for our understanding of the hadron resonance gas. Using ALICE data from 2015-2018, we have reconstructed the Ξ(1820) and measured its mass, width, and yield as functions of transverse momentum and collision multiplicity. The mass and width measurements are in general agreement with previous measurements, but could indicate a slight increase in the width as a function of charged particle multiplicity. These pp studies will inform future studies of the Ξ(1820) in p-Pb and Pb-Pb collisions. |
Monday, April 15, 2019 3:54PM - 4:06PM |
T10.00003: Production of $X(3872)$ Accompanied by a Pion in $B$ Meson Decay Eric Braaten, Liping He, Kevin Ingles If the $X(3872)$ is a weakly bound charm-meson molecule with flavor structure $(D^{*0}\bar{D}^0 +D^{0}\bar{D}^{*0})/\sqrt2$, it can be produced by the creation of charm meson pairs at short distances followed by the formation of the bound state. It can also be produced by the creation of $D^{*}\bar{D}^*$ at short distances followed by their rescattering into $X \pi$. An effective field theory called XEFT predicts that the rate for producing $X$ accompanied by a soft pion should be roughly comparable to that for an isolated $X$. We use the results of a previous isospin analysis of $B$ meson decays into $K D^{(*)}\bar D^{(*)}$ to estimate the short-distance amplitudes for creating $D^*\bar D^*$. We use XEFT to calculate the amplitudes for rescattering into $X \pi$. The resulting predictions for the branching fractions of $B$ mesons into $K X$ plus a soft $\pi^+$ or $\pi^-$ are consistent with measurements of the branching fractions into $KX\pi^\pm$ by the Belle collaboration. If $K X \pi^\pm$ events in which $K\pi^\pm$ come from the $K^*$ resonance are removed, the remaining events are predicted to come primarily from the region of the Dalitz plot with small $X\pi^\pm$ invariant mass. |
Monday, April 15, 2019 4:06PM - 4:18PM |
T10.00004: Normalization Study for the Search for KL->π0νν with the KOTO Experiment Melissa Hutcheson The KOTO Experiment at the J-PARC research facility in Tokai, Japan aims to observe and measure the rare decay of the neutral kaon, KL->π0νν. This decay has a Standard Model (SM) predicted branching ratio (BR) of (3.00 ± 0.30) × 10-11 which is why it has never been observed before. While this decay is extremely rare, it is one of the best decays for studying CP violation in the quark sector because it is a clean channel with small theoretical uncertainties. The experiment E391a previously searched for KL->π0νν events and set a limit of BR(KL->π0νν) < 2.6 × 10-8 in 2010. The KOTO Experiment set a new experimental limit in 2018 for the branching ratio of KL->π0νν from data collected in 2015. From 2016 to 2018, KOTO collected four times more data than in 2015, and this data set is currently being analyzed. A critical part of the analysis includes a detailed study of the normalization modes, KL->3π0, KL->2π0, and KL->2γ, which are used to calculate the KL flux and kinematic and veto cut efficiencies. This talk will focus on the 2016-2018 data and the analysis results of the normalization modes. |
Monday, April 15, 2019 4:18PM - 4:30PM |
T10.00005: New results on the KL—>π0νν search with the KOTO detector Brian O Beckford The KOTO experiment was designed to observe and study the L—>π0νν decay. The Standard Model (SM) prediction for the mode is 2.4 x 10-11 with a small theoretical uncertainty [1]. An experimental upper limit of 2.6 x 10-8 was set by the KEK E391a collaboration [2]. The rare “golden” decay is ideal for probing for physics beyond the standard model. A comparison of experimentally obtained results with SM calculations permits a test of the quark flavor region and provides a means to search for new physics. The signature of the decay is a pair of photons from the π0 decay and no other detected particles. For the measurement of the energies and positions of the photons, KOTO uses a Cesium Iodide (CSI) electromagnetic calorimeter as the main detector, and hermetic veto counters to guarantee that there are no other detected particles. KOTO’s initial data was collected in 2013 and achieved a similar sensitivity as E391a result [3]. This presentation will present the newest results on the upper limit from KOTO and its search of detecting KL—>π0νν.
[1] C. Bobeth, A. J. Buras, A. Celis, and M. Jung, J. High Energy Phys. 04, 079 (2017). [2] J. K. Ahn et al., Phys. Rev. D 81, 072004 (2010). [3] J. K. Ahn et al., Prog. Theor. Phys. 021C01 (2017). |
Monday, April 15, 2019 4:30PM - 4:42PM |
T10.00006: Low
Energy Neutron Emission after Muon Capture Jonathan Miller The Mu2e experiment at Fermilab seeks to observe charge lepton flavor violation through neutrino-less muon to electron conversion after muons are stopped and captured in an aluminum target. The 3E-17 single event sensitivity of the experiment requires unprecedented reduction of backgrounds due to neutrons, protons, and gammas. Thus to better quantify the potential neutron background the AlCap collaboration measured neutron emission after muons are stopped on an Al target using the πE5 beamline at the Paul Scherrer Institute. This talk will present results on the characterization of the emitted neutron energy spectra between 2 to 11 MeV for Al and Ti targets. |
Monday, April 15, 2019 4:42PM - 4:54PM |
T10.00007: Neutrinoless Muon-to-Positron Conversion at Mu2e Hasung Song The Mu2e experiment at Fermilab will search for coherent neutrinoless muon-to-electron conversion interacting with an Aluminum-27 nucleus at a sensitivity 10,000 times higher than the current upper bound. A secondary physics goal of the experiment is the search for neutrinoless muon-to-positron conversion. Not only would this process violate lepton flavor conservation at rates far greater than allowed by the Standard Model, but also violate lepton number conservation. Like neutrinoless double beta decay, muon-to-positron conversion would demonstrate that neutrinos are Majorana particles. Mu2e is also expected to be several orders of magnitude more sensitive than past experiments to muon-to-positron conversion. To achieve this sensitivity, it is important that we thoroughly understand the sources of background positrons in the detection environment. We will discuss detailed simulations of the background processes and predictions for the Mu2e sensitivity to muon-to-positron conversion. |
Monday, April 15, 2019 4:54PM - 5:06PM |
T10.00008: Pileup Systematic Studies in the Fermilab Muon g-2 Experiment Meghna Bhattacharya, Sudeshna Ganguly The Muon g-2 experiment at Fermilab (E989) aims to measure the anomalous magnetic moment of the muon, aμ, to a precision of 140 ppb, a four-fold increase in precision over the previous experiment at Brookhaven National Laboratory (BNL). The value of aμ from BNL currently differs from the Standard Model prediction by ∼3.5 standard deviations or higher, suggesting the potential for new physics and therefore, motivating a new experiment. The Fermilab experiment follows the measurement principles of the BNL experiment, injecting a beam of positive muons into a storage ring, which focuses the beam with a combination of magnetic and electric fields. The muon anomaly relies on the measurement of the spin precession frequency ωa about the muon momentum. This presentation will focus on one of the most important sources of systematic to the ωa analysis: pileup effects. Pileup refers to the overlap of decays in the detector that originate from separate muon decays, too close to each other in time and space to be resolved into individual pulses. A complete description of how pileup events are identified will be presented along with a discussion of how the correction to a traditional ωa analysis is formulated and applied.
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Monday, April 15, 2019 5:06PM - 5:18PM |
T10.00009: Measurement of Moller Scattering at 2.5 MeV Richard G Milner Møller scattering is one of the most fundamental processes in QED. Its knowledge at high precision is necessary for a variety of modern nuclear and particle physics experiments. However, most treatments have neglected the electron mass, which is an approximation that breaks down at relevant low energies. In this work, existing soft-photon radiative corrections were combined with new hard-photon bremsstrahlung calculations to take into account the effect of photon emission at any photon energy. The electron mass was included at all steps. The radiative corrections were compiled into a Monte-Carlo event generator. To test the results, an experiment was designed, constructed, installed, and executed at the MIT High Voltage Research Laboratory. Measurements are reported, comparing the simulated radiative Møller spectra to data at 2.5 MeV. Good agreement between the measurements and the new calculation is observed in the momentum spectrum at three angles. |
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