Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session KL: BSM Searches in Fundamental Symmetries VI: Electroweak interactions |
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Chair: Kent Paschke, University of Virginia Room: Georgian |
Wednesday, October 13, 2021 11:30AM - 11:42AM |
KL.00001: Overview of the MOLLER experiment Ciprian Gal The MOLLER experiment will make use of parity violating electron scattering to improve the determination of the weak charge of the electron by a factor of 5 compared to E158 (2% statistical precision). This measurement can then be used to directly determine the weak mixing angle at low momentum transfer, allowing us to explore a unique portion of the Beyond the Standard Model phase space. The measurement is complementary to the High Luminosity LHC upgrade and will be able to reach a mass of approximately 27 TeV for the lepton-lepton interaction term. In the talk, I will report on the status and selected technical challenges of the experimental design that will enable such a high precision measurement. |
Wednesday, October 13, 2021 11:42AM - 11:54AM |
KL.00002: Collimator and detector design for the MOLLER experiment Chandan Ghosh The MOLLER experiment proposes to measure the parity-violating electron-electron scattering asymmetry from an unpolarized liquid Hydrogen target with unprecedented accuracy (relative uncertainty 2.4%). Systematic control and large experimental acceptance are crucial to achieving that goal. The collimator system is designed to cover the 100% azimuthal acceptance and provide an adequate signal-to-background ratio. The segmented detector design will measure the signal and background contributions from different physics processes and help to control the systematic uncertainties. In this talk, I give an overview of the collimator system and detector's mechanical design. |
Wednesday, October 13, 2021 11:54AM - 12:06PM |
KL.00003: Determination of the Q2 and kinematics for the MOLLER experiment Hanjie Liu The MOLLER experiment proposes to precisely measure the parity violating asymmetry in electron-electron (Moller) scattering. Integrating detectors will be used to count the number of events for each rapidly alternating helicity window without event-by-event kinematic information. The kinematic factor involving the 4-momentum transfer (Q2) must be independently determined to extract the weak mixing angle from the measured asymmetry using low beam current calibration runs, where individual events will be tracked with special purpose Gas Electron Multiplier (GEM) detectors. These tracking events will enable sufficient understanding of the magnetic optics of the spectrometer/collimator system, given the novel and unusual forward angle kinematics. A special collimator with judiciously placed and precisely machined holes (so-called "sieve") will be used to build a map between the reconstructed variables at the tracking detectors and the variables at the target, as well as for determining the acceptance function. An overview of the optics plan for the MOLLER experiment will be presented. |
Wednesday, October 13, 2021 12:06PM - 12:18PM |
KL.00004: Status of Hadronic Parity Violation Jared Vanasse Hadronic parity violation offers a unique probe of QCD and at low energies is described by five distinct two-nucleon low energy constants. These low energy constants are best theoretically extracted from experiments involving few-nucleon systems. This talk will review the current theoretical and experimental landscape in determining low energy parity violation in nuclear systems. In addition, I will briefly discuss the recent large-$N_C$ paradigm and how this affects our current understanding of hadronic parity violation. |
Wednesday, October 13, 2021 12:18PM - 12:30PM Not Participating |
KL.00005: QCD Analysis of \Delta S=0 Hadronic Parity Violation Girish L Muralidhara, Susan Gardner We revisit the QCD analysis of the effective weak Hamiltonian at hadronic energy scales for strangeness-nonchanging ($\Delta S=0$) hadronic processes. Performing a leading-order renormalization group analysis in QCD from the weak to hadronic energy scales, we derive the pertinent effective Hamiltonian for hadronic parity violation, including the effects of both neutral and charged weak currents at the electroweak scale. We determine the additional four-quark operators that enter at low energy scales from QCD operator mixing effects, and we analyze the operator matrix elements using the factorization {\it Ansatz} and recent assessments of the quark axial charges of the nucleon in lattice QCD. We compute the weak meson-nucleon couplings for comparison with existing work. |
Wednesday, October 13, 2021 12:30PM - 12:42PM |
KL.00006: Searching e+e- Final States for New Physics With an Invariant Mass of 10-20 MeV at the ARIEL Electron Accelerator Ross Corliss, Richard G Milner, Jan C Bernauer Reported anomalies in 4He and 8Be transitions, along with the disagreement between calculated and measured values of muonic g-2, which has been recently reiterated by the Fermliab g-2 experiment, have heightened interest in a potential new particle near 17 MeV. To evade current limits, this particle would need to be proto-phobic, and hence suppressed in hadronic production. Leptonic searches, such as production and decay in electron-nucleus scattering, eX → eXA' → eXee+, can test leptonic couplings directly. The DarkLight collaboration of US and Canadian institutions has recently been approved to mount such a search at TRIUMF's ARIEL accelerator, using magnetic spectrometers to reconstruct candidate e+e- pairs in electron scattering from tantalum. Initial data is expected to take place with a 31 MeV, 150 µA beam, with higher beam energies expected to be available in the future. A brief review of the physics involved will be presented, as will the details of the planned experiment and its expected sensitivities to new physics. |
Wednesday, October 13, 2021 12:42PM - 12:54PM |
KL.00007: Polarized Electron Source for the MOLLER Experiment Sachinthani A Premathilake The MOLLER experiment at Jefferson Laboratory will be part of a new generation of ultra-high precision electroweak experiments that will measure the weak charge of the electron by measuring the parity violating asymmetry in electron-electron scattering. One of the crucial systematic uncertainty for this experiment is the non-parity violating asymmetries that results from the helicity-correlated false asymmetries in the polarized electron beam. To achieve the parity quality beam necessary for the small systematic uncertainties required in MOLLER, innovative techniques in the electron source are required. In order to prepare for MOLLER, the Jefferson Laboratory injector has been upgraded & in this talk I will describe new RTP Pockels cell system in the injector source & latest tests done with the upgraded injector. |
Wednesday, October 13, 2021 12:54PM - 1:06PM |
KL.00008: Challenges to Reaching 0.4% Møller Polarimetry in Hall-A at Jefferson Lab Eric King Upcoming experiments in Hall A at Jefferson Lab demand increasingly stringent polarimetry controls with systematic uncertainty goals for polarimetry that are 0.45% for the MOLLER experiment and 0.40% for SoLID spectrometer experiments. While considerable insights and progress were made in the preparation for and during the recent PREX-2 and CREX experiments, there remain existing hurdles which must be overcome. In this talk I will be focusing on particular challenges we face in reaching these goals for the Møller polarimeter and outline a general path forward towards high-precision Møller polarimetry. |
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