Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session T12: Weak Interactions and Physics Beyond the Standard Model |
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Sponsoring Units: DNP Chair: Alexander Komives, DePauw University Room: Marriott Tampa Waterside Room 11 |
Monday, April 18, 2005 1:30PM - 1:42PM |
T12.00001: General classification and analysis of neutron beta-decay experiments Vladimir Gudkov, John Calarco, Geoffrey Greene A method for general analysis of the sensitivities of neutron beta-decay experiments to manifestations of possible deviations from the Standard model is proposed. We take into account all known (radiative and recoil) corrections which are consistent with the Standard model for description of angular correlations in neutron decay in the first order of approximation, or up to level of 10$^{-5}$ (see, for example ref.[1]). The contributions from models beyond the Standard model are, for low energy neutron decay, parameterized in terms of vector, axial-vector, scalar and tensor coupling constants [2] and in terms of parameters related to specific models [3]. For the present analysis we derive the exact expressions for neutron beta decay probability which includes all possible manifestations models beyond the Standard one up to level of 10$^{-5}$ without time-reversal violation. Based on the general expressions for manifestation of the deviation from the standard model we present analysis of the sensitivities for selected neutron decay experiments. 1. S. Ando, H. W. Fearing, V. Gudkov, K. Kubodera, F. Myhrer, S. Nakamura and T. Sato, Phys. Lett. B 595, 250 (2004 ). 2. J. D. Jackson, S.B. Treiman and H. W. Wyld Jr., Nucl. Phys. 4, 206 (1957). 3. P. Herczeg, Prog. Part. Nucl. Phys. 46, 413 (2001). [Preview Abstract] |
Monday, April 18, 2005 1:42PM - 1:54PM |
T12.00002: Design of an Improved Apparatus for a Measurement of the Neutron Lifetime Using Magnetically Trapped Ultracold Neutrons P.-N. Seo, F.H. DuBose, R. Golub, P.R. Huffman, C.M. O'Shaughnessy, G.L. Palmquist, J.M. Doyle, J. Olson, L. Yang, E. Korobkina, K.J. Coakley, H.P. Mumm, A.K. Thompson, G.L. Yang, S.K. Lamoreaux As a part of an on-going program that seeks to measure the neutron lifetime using magnetically trapped ultracold neutrons (UCN), we are in the process of incorporating a larger and deeper superconducting magnetic trap into our apparatus. The experiment works by loading the trap with UCN through inelastic scattering of 0.89 nm neutrons with phonons in superfluid $^{4} $He. Trapped neutrons are detected when they decay; charged decay electrons ionize helium atoms in the superfluid resulting in scintillation light that is recorded in real time using photomultiplier tubes. We will discuss the design and performance of the new Ioffe-type trap and provide an overview of the statistical sensitivity we expect to reach with the improved apparatus. [Preview Abstract] |
Monday, April 18, 2005 1:54PM - 2:06PM |
T12.00003: Status of the Twist Measurement of the Muon Decay Parameter P$_{\mu}\xi$ Blair Jamieson Muon decay, a purely leptonic decay, is a relatively simple interaction to study when looking for physics not explained by the standard Vector minus Axial Vector (V-A) theory of electroweak interactions. The TWIST spectrometer measures the doubly differential spectrum of decay positrons for a wide range in reduced energy and angle between muon and decay positron momentum. By measuring a large part of muon decay spectrum, TWIST is sensitive to the exact shape of the decay spectrum, and can simultaneously measure three of the muon decay parameters with a high degree of accuracy. I will review the status of the TWIST experiment, and physics related to the muon decay parameter P$_{\mu}\xi$. TWIST will measure P$_{\mu}\xi$ by about an order of magnitude better than previous direct measurements. The status of analysis of systematic uncertainties in the measurement of P$_{\mu}\xi$ is presented. [Preview Abstract] |
Monday, April 18, 2005 2:06PM - 2:18PM |
T12.00004: TWIST Measurement of the Decay Parameters rho and delta of Normal Muon Decay Jim Musser The TWIST collaboration is improving the precision on the characterization of normal muon decay, $\mu^+\rightarrow e^+\nu_e\bar{\nu}_{\mu}$, through measurements of the decay parameters $\rho$, $\delta$ and $P_{\mu}\xi$. The analysis of the initial TWIST measurements of $\rho$ and $\delta$ have been completed. We find $\rho=0.75080\pm0.00032(stat.)\pm0.00097(syst.)\pm0.00023 $ and $\delta=0.74964\pm0.00066(stat.)\pm0.00112(syst.)$, consistent with the Standard Model. The improved precision places new limits on physics beyond the Standard Model, such as the parameters describing left-right symmetric models. The current results and implications will be discussed. [Preview Abstract] |
Monday, April 18, 2005 2:18PM - 2:30PM |
T12.00005: Precision Measurement of Muon Capture on the Proton - the MuCAP experiment. Bernhard Lauss PNPI-PSI-UC Berkeley-UI Urbana-Champaign-UC de Louvain-Boston University - UK Lexington-TU M\"unchen. The goal of the MuCAP experiment is the determination of the singlet muon capture rate on the proton to 1\%. Such a measurement would allow us to extract g$_{P}$, the induced pseudoscalar form factor of the proton, to a few percent. In comparison with the other weak form factors, the pseudoscalar one is known orders of magnitude worse. Moreover, the most precise experimental values are ambiguous, in mutual disagreement, and partially in conflict with theory. In contrast to the experimental situation, recent calculations within chiral perturbation theory agree and are accurate on the few percent level. A precise unambiguous measurement would thus provide a stringent test of the underlying accurate QCD relations. The MuCAP collaboration completed an improved setup last fall with the installation of a second wire chamber allowing for electron tracking to the decay muon vertex, and a continuous hydrogen high-Z purification system. We successfully operated our active muon-stop target, a time-projection chamber, in sub-ppm pure hydrogen over weeks and collected data, doubling the statistics of cleanly observed $\mu^{-}$-decay events of all previous experiments. We will discuss plans for the experiment and progress of the present analysis which should lead to a significant improvement on the current world data on g$_{P}$. [Preview Abstract] |
Monday, April 18, 2005 2:30PM - 2:42PM |
T12.00006: Proposed Searches for Electric Dipole Moments of the Muon, Deuteron and Proton in Storage Rings Yannis Semertzidis We will describe a new, highly-sensitive method of probing for electric dipole moments (EMD) on charged particles, such as muons, deuterons, and protons in magnetic storage rings. These techniques utilize the strong electric fields present in the particle's rest frame due to relativistic effects. We will discuss the physics reach for a range of sensitivities: $10^{-27}$ to $10^{-29}\ {\rm e}\kern-1pt\cdot\kern-1pt{\rm cm}$ for the deuteron/proton and $<10^{-24}\ {\rm e}\kern-1pt\cdot\kern-1pt {\rm cm}$ for the muon (see also \urllink{The storage ring EDM collaboration web page} {http://www.bnl.gov/edm/}). We will compare ring designs that (a) cancel the precession of the anomalous magnetic moment using electric fields and (b) accumulate an EDM precession using a resonance between the anomalous precession and synchrotron oscillations. The mere existence of an EDM for a fundamental particle at these levels would imply a new source of CP-violation that is several orders of magnitude above Standard Model predictions but within the range of speculative models containing new physics. [Preview Abstract] |
Monday, April 18, 2005 2:42PM - 2:54PM |
T12.00007: VLADD : An Extra Dimensions Detector Heather Ray, Richard Van de Water, Paul Vetter The existence of extra-dimensions may be detected by observing the invisible decay of orthopositronium (oPs) at a branching ratio of $10^{- 10}$. Previous experiments have searched for invisible decays at a branching ratio of $10^{-6}$ but were unable to achieve greater precision due to electron backgrounds. None of these experiments attempted to utilize a detector which would distinguish positrons from electrons. The VLADD experiment proposes to use a mini-TPC placed in a small, stable magnetic field as a means to separate $e^+$ from $e^-$. VLADD will be a demonstration experiment to verify that this technique will in fact work and will allow adequate rejection of backgrounds. Should the techniques used in VLADD reach a branching ratio sensitivity on the order of the most sensitive current measurements ($10^{-6}$), then a proposal will be made to build a larger version of VLADD for a more sensitive extra-dimensions search. [Preview Abstract] |
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