Bulletin of the American Physical Society
2020 Fall Meeting of the APS Division of Nuclear Physics
Volume 65, Number 12
Thursday–Sunday, October 29–November 1 2020; Time Zone: Central Time, USA
Session EP: Mini-Symposium: Hadronic Weak Interactions II |
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Chair: Christopher Haddock, NIST |
Friday, October 30, 2020 10:30AM - 11:06AM |
EP.00001: Final Results of a Precision Measurement of the Parity Violating Asymmetry in Cold Neutron Capture on $^{3}$He Invited Speaker: Mark McCrea The hadronic weak interaction (HWI) is one of the least well understood sectors of the Standard Model. While it is in principle described by the Electro-Weak component of the Standard Model as the exchange of W and Z bosons between quarks, the computational difficulties associated with non-perturbative quantum chromodynamics (QCD) prevent first principle calculations of HWI observables. To calculate HWI observables, approaches such as the Desplanques, Donoghue, and Holstein (DDH) model and lately effective field theory (EFT) models have been used, but these models require a number of weak coupling constants to be determined from experiment. The n3He experiment, which ran at the Oak Ridge National Laboratory in 2015, made a high precision measurement of the directional parity vio- lating asymmetry in the direction of proton emission relative to the initial neutron polarization in the reaction ~n $+$ $^{3}$He → t $+$ p, with a result A$_{PV}$ = (1.58 $±$ 0.97(stat) $±$ 0.24(sys)) $×$ 10$^{−8}$ . I will briefly discuss the models used to calculate this asymmetry, the n3He experiment itself, the data analysis process that resulted in the asymmetry, and how this result combined with other past and some possible future experiments can be used to set limits on the weak couplings constants. [Preview Abstract] |
Friday, October 30, 2020 11:06AM - 11:18AM |
EP.00002: The NDTGamma experiment: Hadronic Parity Violation in Counting Mode Christopher Crawford The recent NPDGamma and n3He experimental constraints of $h_\pi^1$ and $h_{\rho{-}\omega}^{0}$ are important milestones towards the goal of a complete spin and isospin characterization of the Hadronic Weak Interaction. The remaining experimentally accessible few-body observables pose special challenges--for example, the neutron spin asymmetry $A_\gamma^{\vec{n}d}$ of gamma rays in the reaction $\vec{\mbox{n}} + \mbox{d} \to \mbox{t} + \gamma$ in an experimentally achievable D$_2$O target would be highly diluted by the low signal-to-background ratio of the suppressed (~mb) n-D capture cross section in a traditional current-mode experiment. Given the moderate event rates from this reaction and modern capabilities of high-speed digital pulse-processing electronics, we describe progress towards the possibility of detecting and discriminating on individual gamma-rays from the 6.2 MeV neutron capture photopeak in real time. This will enable the first counting-mode measurement of Hadronic Parity Violation in a few-body system in which quasi exact (3-body) calculations in the DDH potential and chiral EFT are possible. [Preview Abstract] |
Friday, October 30, 2020 11:18AM - 11:30AM |
EP.00003: A CsI detector array for NDTGamma test measurements Diana Sahibnazarova The goal of the NDTGamma experiment is to measure the directional asymmetry in gamma-ray emission from the reaction n + D $\to$ T + $\gamma$ (6.2 MeV). A 4x4 array of recycled CsI scintillators and photomultipliers tube (PMT) has been constructed for initial tests at the LANSCE FP12 beamline. Each detector was tested with different PMTs with a Co-60 gamma-ray source to calibrate the detectors and optimize high voltage and digital spectroscopy parameters. The signals were analyzed using both CAEN and low-cost Red Pitaya data acquisition systems. I will present the calibrations results and initial data from the FP12 tests. [Preview Abstract] |
Friday, October 30, 2020 11:30AM - 11:42AM |
EP.00004: A Low-Cost High-Performance Digital Signal Processing System for Nuclear Spectroscopy Yuke Wang, Christopher Crawford The NDTGamma experiment aims to measure hadronic parity violation in neutron capture on the deuteron, for which the capture cross section is $10^3$ times smaller than capture on hydrogen. We must count individual gammas to spectroscopically filter out background events. Advancement in computing has allowed the use of field programmable gate arrays to perform digital filtering to obtain high energy resolution in real time. We have implemented a recursive piecewise polynomial convolution filter on the Red Pitaya--a low-cost data acquisition platform with two analog to digital converters and a field programmable gate array. The system is able to detect events and record full waveforms with performance comparable to standard commercial systems available for nuclear physics. [Preview Abstract] |
Friday, October 30, 2020 11:42AM - 11:54AM |
EP.00005: Status of an Experiment to Measure the Parity-odd Neutron Spin Rotation in$\hspace{2mm}^4$He Jerald Balta The NN weak interaction is sensitive to quark-quark correlations in the nucleon and provides the means to test the Standard Model in the low energy strongly interacting limit. Recent theoretical work [1,2] along with the measurement of the weak pion exchange component of the NN weak interaction [3] implies a large parity-odd neutron spin rotation in $^{4}$He just outside the previous measurement of $d\phi/dz = [+2.1 \pm 8.3(stat.) \pm 2.9(sys.)] \times 10^{-7}$ rad/m [4]. Upgrades to the NSR apparatus enable an experimental sensitivity $< [\pm 1.0(stat.) \pm 1.0(sys.)] \times 10^{-7}$ rad/m [5] on the NG-C beamline at NIST. The status of the NSR apparatus as well as implications of the recent measurement in the n-3He system [6] will be discussed. \\ \\{[1]} S. Gardner, W. C. Haxton, and B. R. Holstein, Ann. Rev. Nucl. Part. Sci. \textbf{67}, 69, 024001, (2017). \\{[2]} R. Lazauskas and Y.-H Song, Phys. Rev. C {\bf 99}, 054002 (2019). \\{[3]} D. Blyth {\it et al.} (NPDGamma Collaboration), Phys. Rev. Lett. {\bf 121}, 242002 (2018). \\{[4]} H. E. Swanson, {\it et al.}, Phys. Rev. C {\bf 100}, 015204 (2019). \\{[5]} W. M. Snow, {\it et al.}, Rev. Sci. Inst. \textbf{94}, 055101, (2015). \\{[6]} M. T. Gericke, {\it et al.}, Accepted to arXiv, (2020). [Preview Abstract] |
Friday, October 30, 2020 11:54AM - 12:06PM |
EP.00006: A Search for Possible Weakly-Coupled $Z^{\prime}$ Bosons to the Neutron Using Slow Neutron Spin Rotation Krystyna Lopez An exotic axial vector interaction with a mm to $\mu$m range that couples weakly to the neutron through exchange of a $Z^{\prime}$ boson can appear in some extensions of the Standard Model [1]. We present the current status and systematic uncertainty analysis for an experiment to search for an interaction of the form $V_{5}=\frac{g^{2}_{A}}{4\pi m}\frac{e^{-m_{0}r}}{r}(\frac{1}{r}+\frac{1}{\lambda_{c}})\vec\sigma\cdot(\vec v\times\hat r)$. We plan to employ slow neutron polarimetry [2] to look for a spin rotation of transversely polarized slow neutrons which pass through a series of open parallel slots bounded by flat rectangular plates of tungsten, copper, and glass [3]. The goal of our experiment is to improve the sensitivity of $\varphi'=[2.8\pm4.6(stat.)\pm4.0(sys.)]\times10^{-5}$ rad/m achieved in [4] by at least two orders of magnitude at the NIST NG-C beamline. We will discuss our work using pT-sensitivity B-field maps of the plate surfaces to bound the main source of systematic uncertainty arising from residual magnetic fields.\\\\{[1]} F. M. Piegsa and G. Pignol, Phys. Rev. Lett. 108 (2012)\\{[2]} W. M. Snow et al., Rev. Sci. Inst. 86, 055101 (2015)\\{[3]} C. Haddock et al., Nucl. Inst. Meth. A 885 (2018)\\{[4]} C. Haddock et al., Phys. Lett. B 783 (2018) [Preview Abstract] |
Friday, October 30, 2020 12:06PM - 12:18PM |
EP.00007: Magnetic Characterization of Target Plates for an Experiment to search for Z' Boson Axial Vector Couplings to the Neutron Lukas Cavar We plan to conduct a slow neutron spin rotation experiment to search for possible weakly-coupled $Z'$ bosons to the neutron via an interaction of the form $V_{5}=\frac{g^{2}_{A}}{4\pi m}\frac{e^{-m_{0}r}}{r}(\frac{1}{r}+\frac{1}{\lambda_{c}})\vec\sigma\cdot(\vec v\times\hat r)$. A previous experiment [1] reported $\phi < 4*10^{-6}$ $rad/m$ for the neutron spin rotation angle accumulated by polarized neutrons passing very close to a set of $1/2$ m copper plates [2], and we anticipate magnetic impurities may be our dominant source of systematic error. We discuss a B-field mapping apparatus our group has constructed consisting of a QuSpin Zero-Field Magnetometer and Parker motors to search for magnetic impurities embedded in the target plates. The data analysis must see fields near the limit of the probe noise ($\sim$pT) in the presence of slowly-varying background magnetic fields ($\sim$nT). We discuss our results for maps of glass, copper, and tungsten plates from implementing ABBA data measurement patterns [3] and low-degree polynomial drift subtraction of time-dependent effects. \\\\{[1]} C. Haddock et al., Phys. Lett. B 783 (2018)\\{[2]} C. Haddock et al., Nucl. Inst. Meth. A 885 (2018)\\{[3]} H.E. Swanson and S. Schlamminger, Meas. Sci. Technol. 21 , 115104 (2010) [Preview Abstract] |
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