Bulletin of the American Physical Society
APS April Meeting 2012
Volume 57, Number 3
Saturday–Tuesday, March 31–April 3 2012; Atlanta, Georgia
Session C10: Electroweak Interactions |
Hide Abstracts |
Sponsoring Units: DNP Chair: Pieter Mumm, NIST Room: Embassy A |
Saturday, March 31, 2012 1:30PM - 1:42PM |
C10.00001: Prospects for True Muonium Physics with HPS Andrzej Banburski, Philip Schuster True muonium, the bound state of a muon-antimuon pair, is one of the smallest QED bound states in Nature and has thus far never been observed. The Heavy Photon Search (HPS) experiment at Jefferson Laboratory, designed to search for new sub-GeV forces, should have sufficient sensitivity to discover and study True Muonium. We will describe how this can be done, and explain future prospects for True Muonium physics using the nominal HPS layout and potential upgrades. [Preview Abstract] |
Saturday, March 31, 2012 1:42PM - 1:54PM |
C10.00002: MuSun - Muon Capture on the Deuteron Peter Kammel The MuSun experiment is a measurement of the rate for muon capture on the deuteron to 1.5\% precision. This basic weak interaction process on a nucleus can be calculated and measured to a high degree of precision. Experimental improvements are due to a novel active target technique, while electro-weak observables in few-body systems can now be calculated within the framework of QCD based effective field theories (EFT). The experiment is designed to resolve the long-standing inconclusive experimental status and to determine an important, but poorly known low-energy constant, required in the EFT. This constant also enters the calculation of fundamental astrophysical reactions, like solar $pp$ fusion and $\nu d$ scattering. The MuSun experiment will determine it to a precision 5 times greater than presently available from 2N observables. The experiment must be performed under conditions which lead to an unambiguous interpretation, independent of muonic atomic physics complications. A new high-density cryogenic time projection chamber filled with ultra-pure deuterium has been developed as a target and a first production run has been performed. Several upgrades are being prepared towards the collection of the full statistics. [Preview Abstract] |
Saturday, March 31, 2012 1:54PM - 2:06PM |
C10.00003: Suppression of false asymmetries for the QWeak experiment Emmanouil Kargiantoulakis The Qweak experiment at Jefferson Lab will determine the neutral weak charge of the proton to a precision of 4\% by measuring the parity-violating asymmetry of polarized electrons, providing a stringent test of the Standard Model and probing new physics at the 2 TeV scale. For this goal to be achieved, the asymmetry will be measured at an accuracy of 4 parts-per-billion. At this level of precision, it is necessary to minimize the contribution of false asymmetries and keep systematic errors below the part-per-billion level. In this talk, we will discuss techniques for configuring the polarized electron source to minimize changes in the beam intensity, trajectory, and energy under reversal of the beam helicity, as well as beam diagnostics and complementary analysis strategies employed to make remaining corrections to the measured asymmetry. [Preview Abstract] |
Saturday, March 31, 2012 2:06PM - 2:18PM |
C10.00004: Measurement of Branching-Ratios in the $\beta$ Decay of $^{38}$Ca H.I. Park, J.C. Hardy, V.E. Iacob, M. Bencomo, L. Chen, J. Goodwin, V. Horvat, N. Nica, B. Roeder, L. Trache, R.E. Tribble Currently, the most stringent test of the unitarity of the CKM matrix depends on results from precise ft-value measurements of superallowed beta decays. One of the key elements of this test is the calculated isospin-symmetry-breaking (ISB) correction that must be applied to each experimental ft value in order to extract a corrected Ft value. According to conserved vector current, the Ft values for all such transitions should be the same, so the efficacy of a particular set of ISB correction terms can be judged by whether they satisfy this condition. This test becomes even more demanding if additional superallowed ft values can be measured, especially for cases where the ISB correction is expected to be unusually large. The case of $^{38}$Ca is particularly interesting because its total ISB correction is calculated to be one of the largest in the $sd$ shell. However, being a $T_{Z}=-1$ nucleus decaying to an odd-odd $T_{Z}=0$ daughter, it has multiple beta-decay branches. This presentation focuses on progress in our measurement of the branching-ratio for the superallowed $0^{+}\rightarrow0^{+}$ transition from $^{38}$Ca. The challenges remaining before we reach our goal of 0.1\% precision will be discussed, and preliminary results presented. [Preview Abstract] |
Saturday, March 31, 2012 2:18PM - 2:30PM |
C10.00005: An Alpha-Gamma Counter for Absolute Neutron Flux Measurement A. Yue, G. Greene, M. Dewey, D. Gilliam, J. Nico, A. Laptev An alpha-gamma counter was used to measure the absolute neutron flux of a monochromatic cold neutron beam to sub-0.1\,\% precision. Simultaneously, the counter was used to calibrate a thin neutron flux monitor based on neutron absorption on ${}^{6}$Li to the same precision. This monitor was used in the most precise beam-based measurement of the neutron lifetime, where the limiting systematic effect was the uncertainty in the neutron counting efficiency (0.3\,\%). The counter uses a thick target of ${}^{10}$B-enriched boron carbide to completely absorb the beam. The rate of absorbed neutrons is determined by counting 478 keV gamma rays from neutron capture on ${}^{10}$B with calibrated high-purity germanium detectors. The calibration results and the implications for the neutron lifetime will be discussed. [Preview Abstract] |
Saturday, March 31, 2012 2:30PM - 2:42PM |
C10.00006: Recent Progress Towards a Measurement of the Neutron Lifetime Using Magnetically Trapped Ultracold Neutrons K.W. Schelhammer, C.R. Huffer, P.R. Huffman, D.E. Marley, K.J. Coakley, Michael Huber, P.P Hughes, H.P. Mumm, A.K. Thompson, A.T. Yue, N.C. Abrams Free neutron beta decay is a fundamental process in the Standard Model that can be used to test the weak interaction as well as provide information about primordial $^4$He abundance. Recent precision measurements of the neutron lifetime have led to reduced confidence in the absolute value of this parameter; due presumably to unknown systematic effects. This work seeks to measure the neutron lifetime using a different technique that employs a superconducting magnetic trap to confine ultracold neutrons. Neutrons are loaded into the trap through the superthermal technique where $1$ mEv neutrons down scatter from phonons in liquid helium losing the majority of their energy. Neutrons in the appropriate spin state are then confined by the static magnetic field. During the past year, over $400$ run cycles of data were collected using the upgraded apparatus. Analysis of previous data sets was limited due to large numbers of background events relative to the neutron decay signal. An increased number of trapped neutrons as well as a analysis using pulse shape discrimination allows one to significantly increase the overall precision of the measurement. Details of this ongoing analysis will be presented with preliminary results. [Preview Abstract] |
Saturday, March 31, 2012 2:42PM - 2:54PM |
C10.00007: Update of the NPDGamma Experiment at the Fundamental Neutron Physics Beamline at the Spallation Neutron Source Serpil Kucuker Dogan The NPDGamma experiment, which measures parity-violating directional gamma asymmetry in neutron-proton capture, is running at the FNPB at SNS. In the experiment intense polarized low-energy neutron beam interacts with liquid para-hydrogen target, gamma rays from the capture reaction is detected by 48 CsI(Tl) detectors with the 3$\pi$ acceptance angle. The experiment aims to measure the asymmetry with accuracy of $10^{-8}$ which requires total of xyz h of beam. We describe the experiment and talk about the status of the data taking. [Preview Abstract] |
Saturday, March 31, 2012 2:54PM - 3:06PM |
C10.00008: Measurement of the Parity-Violating directional Gamma-ray Asymmetry in Polarized Neutron Capture on $^{35}$Cl Nadia Fomin The NPDGamma experiment aims to measure the parity-odd correlation between the neutron spin and the direction of the emitted photon in neutron-proton capture. A parity violating asymmetry (to be measured to 10$^{-8}$) from this process can be directly related to the strength of the hadronic weak interaction between nucleons. As part of the commissioning runs on the Fundamental Neutron Physics beamline at the Spallation Neutron Source at ORNL, the gamma-ray asymmetry from the parity-violating capture of cold neutrons on $^{35}$Cl was measured, primarily to check for systematic effects and false asymmtries. The current precision from existing world measurements on this asymmetry is at the level of 10$^{-6}$ and we believe we can improve it. The analysis methodology as well as preliminary results will be presented. [Preview Abstract] |
Saturday, March 31, 2012 3:06PM - 3:18PM |
C10.00009: Towards a new study of the electron-neutrino angular correlation in the decay of trapped $^6$He Andreas Knecht We are pursuing a program to search for new physics in the form of tensor contributions to the well established vector and axial-vector structure of the weak interaction. Such contributions potentially show up in the measurement of the angular correlation between the electron and neutrino momenta in nuclear beta decay. Our system of choice is the pure Gamow-Teller decay of the nucleus $^6$He. We produce and transfer $\sim10^9$ atoms/s to our trapping system consisting of a Zeeman slower and a magneto-optical trap (an additional dipole trap will be added later). This talk will describe our recent successful efforts to trap $^6$He and give an outlook on the next steps and plans for the full experiment. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700