Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session CD: Muon Physics |
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Chair: David Hertzog, University of Washington Room: Hilton Kohala 3 |
Wednesday, October 24, 2018 7:00PM - 7:15PM |
CD.00001: The MuSun Experiment: Muon Capture and Chiral Two-body Currents Rachel Ryan Muon capture provides a powerful tool to study currents and forces in few-nucleon systems. In effective field theories of two-nucleon weak interactions, a single poorly-known low energy constant enters. The MuSun experiment will extract this quantity from a high precision measurement of the muon capture rate on deuterium, $\mu + d \rightarrow n + n + \nu_{\mu}$, and calibrate related fundamental astrophysics reactions. A unique cryogenic time projection chamber is employed to measure the capture rate as a deviation of the negative muon lifetime in deuterium gas from the free muon lifetime. Analysis of the $10^{10}$ fully reconstructed muon decay events collected over two ten-week beam periods is coming to a close. Advanced analyses to combat the major systematic issues, including muon catalyzed fusion interference, critical background suppression, and gas purity determination, have been developed and applied to the production data of the first beam period. An experimental error budget, overall dataset consistency and the final steps to unblinding will be presented. |
Wednesday, October 24, 2018 7:15PM - 7:30PM |
CD.00002: The Systematics of the PEN experiment, A Precision Measurement of Pion Electronic Decay Branching Ratio Charles J Glaser
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Wednesday, October 24, 2018 7:30PM - 7:45PM |
CD.00003: Radiative pion and muon decays in the PEN experiment Dinko Pocanic Radiative decays of the muon, μ+ -> e+ + νe + νbarμ + γ, and pion, π+ -> e+ + νe + γ, or πe2γ, where the photon carries away a non-negligible portion of the available energy, are sensitive in different ways to departures from the basic V-A dynamics of the weak interaction. Like other pion and muon decay channels, they are described with extreme precision in the standard model (SM) of elementary particles and fields. Hence, both processes are effective in studies of the limits on certain non-SM interactions. Additionally, the radiative pion electronic decay offers a direct the weak form factors of the pion. The ratio of the axial-vector and vector pion form factors, FA/FV is one of the basic inputs in low energy chiral lagrangians, such as chiral perturbation theory. We discuss the progress on the analysis of pion and muon radiative decays in the PEN experiment. |
Wednesday, October 24, 2018 7:45PM - 8:00PM |
CD.00004: Measurement of the electric field correction to the muon spin precession frequency in the E989 Muon g-2 experiment at Fermilab Antoine Chapelain The E989 Muon g-2 experiment at Fermilab aims to measure the anomalous magnetic moment of the muon to an unprecedented precision of 140 ppb to solve the tantalizing 3-4 standard deviation discrepancy between the previous measurement at Brookhaven in 2001 and the Standard Model prediction. The E989 experiment has completed its first physics run and collected a dataset roughly two times larger than the Brookhaven experiment's. The measurement of the anomalous magnetic moment relies on measuring the muon spin precession frequency and the storage magnetic field to a precision of 120 and 70 ppb, respectively. Electrostatic quadrupoles provide vertical focusing for the beam circulating in the muon storage ring. The quadrupole electric fields affect the precession frequency of off momentum muons. We will discuss in this talk the measurement of the anticipated O(100) ppb correction to the spin precession frequency using data from the 2018 run, and the challenge of achieving the uncertainty budget of 20 ppb. |
Wednesday, October 24, 2018 8:00PM - 8:15PM |
CD.00005: Hadronic light-by-light scattering and the muon’s (g-2) Igor Danilkin, Marc Vanderhaeghen In my talk, I will present our recent dispersive analysis of the gamma gamma* -> pipi, pieta processes from the threshold up to 1.4 GeV in the two photon invariant mass. These amplitudes serve as important input to constrain the hadronic piece of light-by-light scattering contribution to (g-2) and support the current experimental program at BESIII. As well, I will present an application of the light-by-light scattering sum rules to the gamma gamma*-production of mesons in light of the new data by the Belle Collaboration on the transition form factors. |
Wednesday, October 24, 2018 8:15PM - 8:30PM |
CD.00006: Measuring the Precession Frequency in the E989 Muon g-2 Experiment Aaron T Fienberg The E989 Muon g-2 Experiment has completed its first physics run and collected a dataset roughly two times larger than the Brookhaven experiment's. With a target precision of 140 ppb, divided equally between statistics and systematics and requiring 20 times as many muons as Brookhaven, E989 will achieve the most precise measurement to date of the muon's anomalous magnetic moment. The E989 experiment seeks to either confirm or resolve the larger than 3 sigma discrepancy between theory and measurement. The measurement requires extracting the muon anomalous precession frequency in a highly uniform magnetic field. This frequency is imprinted on the time-dependent energy distribution of decay positrons observed by 24 electromagnetic calorimeters. Systematic effects originating both from storage ring beam dynamics and detector effects complicate the precession analysis. This presentation will describe the analysis techniques as they are applied to data from the 2018 run and show blinded analysis results that demonstrate the quality of the data collected. |
Wednesday, October 24, 2018 8:30PM - 8:45PM |
CD.00007: Precision magnetometry in the Muon g-2 storage ring at Fermilab H Swanson The Muon g-2 experiment at Fermilab is the fifth generation measurement of the Muon’s anomalous magnetic moment with improved precision to reduce the current uncertainty between measurement and Standard Model prediction. This requires a simultaneous determination of the muon’s anomalous precession frequency and the magnetic field along its trajectory. The upgraded field measurement system is described in detail including compatibility with shimming techniques for improved field homogeneity around the 50 foot diameter storage ring. Outside the storage region 378 probes continuously monitor the field where more than 350 have precisions of 50 parts per billion (ppb). A mini version of this system periodically samples the field seen by muons. We show field variations over the last running period and discuss the implications of temperature dependence and other effects from the magnet itself. The data are used to interpolate between measurements in the storage volume and when convoluted with muon trajectories comprise field measurements for this phase of the experiment. |
Wednesday, October 24, 2018 8:45PM - 9:00PM |
CD.00008: Magnetic Field Tracking in the Muon g-2 Experiment Rachel Osofsky The muon g-2 experiment at Fermilab aims to measure the anomalous magnetic moment of the muon to a precision of 140 parts per billion (ppb). The measurement will shed light on the deviation between Standard Model calculations and the previous measurement at Brookhaven National Laboratory. The experiment measures the difference between the cyclotron and spin precession frequencies of muons in a highly uniform magnetic field, where the magnetic field over a muon's trajectory must be known to 70 ppb. Magnetic field gradients in the storage region are mapped precisely every 3 days by an in-vacuum field mapping system (trolley) carrying an array of 17 nuclear magnetic resonance (NMR) probes. Between trolley runs the time evolution of the field, caused for example by temperature variations in the hall, is monitored by a suite of 378 fixed NMR probes mounted outside of the vacuum chambers. The fixed probes are used to interpolate the field experienced by muons between trolley runs. An overview of the magnetic field interpolation analysis will be presented. |
Wednesday, October 24, 2018 9:00PM - 9:15PM |
CD.00009: Precise Measurement of the $K_{e2}/K_{\mu 2}$ Branching Ratio and New Physics Search with a Stopped $K^+$ Beam Experiment Tongtong Cao
The J-PARC TREK/E36 experiment with a stopped $K^+$ beam is designed to provide a more precise measurement of the branching ratio $R_K=\Gamma(K^+\rightarrow e^+\nu)/\Gamma(K^+\rightarrow \mu^+\nu)$ than previous in-flight $K^+$ decay experiments. $R_K$ is very precisely predicted by the Standard Model (SM) with an uncertainty of $4\times10^{-4}$ and any deviation from this prediction would very clearly indicate the existence of new physics beyond the SM. Additionally, the experiment is searching for light neutral bosons ($A^{'}$), which could be associated with dark matter or explain the $g_{\mu}$-2 anomaly and the proton radius puzzle. In the experiment, a $K^+$ beam was stopped by a scintillating fiber target, and charged decay products were momentum analyzed and tracked by a 12-sector superconducting toroidal magnetic spectrometer and multi-wire proportional chambers (MWPCs) combined with a photon calorimeter with a large solid angle (75\% of $4\pi$) and 3 different particle identification systems. In this talk, the status of the $R_K$ and $A^{'}$ analyses is presented, and the MWPC calibration and tracking by a Kalman filter are reported. This work has been supported by awards DE-SC0003884 and DE-SC0013941 in U.S., NSERC in Canada, and Kaken-hi in Japan.
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Wednesday, October 24, 2018 9:15PM - 9:30PM |
CD.00010: Search for light neutral bosons in the TREK/E36 experiment Bishoy Handiipondola Dongwi, Michael Kohl, Tongtong Cao The TREK/E36 (E36) experiment conducted at J-PARC in Japan aims to test lepton universality in the ratio of decay widths, $R_{K} = \Gamma(K_{e2})/\Gamma(K_{\mu2})$, by utilizing a scintillating fiber target to stop a beam of up to 1.2 million $K^+$ per spill. In addition, the E36 detector system allows us to search for light $U(1)$ gauge bosons below 300 MeV/$c^2$, which could be associated with dark matter or explain the established muon-related anomalies such as the muon $g-2$ value, and the proton radius puzzle. Particle identification systems in combination with a highly segmented CsI(Tl) photon calorimeter covering $75\%$ of $4\pi$ are being used to search for these exotic particles in rare $K^+$ decay modes. The status of the particle search as well as simulation based exclusion limits will be presented. |
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