Physics Commons^™

Search For Dark Matter Decay Of The Free Neutron From The Ucna Experiment: N → Χ + E+E−, X. Sun, E. Adamek, B. Allgeier, M. Blatnik, T. J. Bowles, L. J. Broussard, M. A. -P. Brown, R. Carr, S. Clayton, C. Cude-Woods, S. Currie, E. B. Dees, X. Ding, B. W. Filippone, A. García, P. Geltenbort, S. Hasan, K. P. Hickerson, J. Hoagland, R. Hong, G. E. Hogan, A. T. Holley, T. M. Ito, A. Knecht, C. -Y. Liu, J. Liu, M. Makela, R. Mammei, J. W. Martin, D. Melconian, Subash C. Nepal, Bradley R. Plaster

Physics and Astronomy Faculty Publications

It has been proposed recently that a previously unobserved neutron decay branch to a dark matter particle (χ) could account for the discrepancy in the neutron lifetime observed in experiments that use two different measurement techniques. One of the possible final states discussed includes a single χ along with an e⁺e⁻ pair. We use data from the UCNA (Ultracold Neutron Asymmetry) experiment to set limits on this decay channel. Coincident electron-like events are detected with ∼4π acceptance using a pair of detectors that observe a volume of stored ultracold neutrons. The summed kinetic energy (E_{e …}

New Result For The Neutron Β-Asymmetry Parameter A0 From Ucna, M. A.-P. Brown, E. B. Dees, E. Adamek, B. Allgeier, M. Blatnik, T. J. Bowles, L. J. Broussard, R. Carr, S. Clayton, C. Cude-Woods, S. Currie, X. Ding, B. W. Filippone, A. García, P. Geltenbort, S. Hasan, K. P. Hickerson, J. Hoagland, R. Hong, G. E. Hogan, A. T. Holley, T. M. Ito, A. Knecht, C. -Y. Liu, J. Liu, M. Makela, J. W. Martin, D. Melconian, M. P. Mendenhall, S. D. Moore, Subash C. Nepal, N. Nouri, Bradley R. Plaster

Physics and Astronomy Faculty Publications

Background: The neutron β-decay asymmetry parameter A₀ defines the angular correlation between the spin of the neutron and the momentum of the emitted electron. Values for A₀ permit an extraction of the ratio of the weak axial-vector to vector coupling constants, λ ≡ g_A/g_V, which under assumption of the conserved vector current hypothesis (g_V = 1) determines g_A. Precise values for g_A are important as a benchmark for lattice QCD calculations and as a test of the standard model.

Purpose: The UCNA experiment, carried out at the …

First Direct Constraints On Fierz Interference In Free-Neutron Β Decay, K. P. Hickerson, X. Sun, Y. Bagdasarova, D. Bravo-Berguño, L. J. Broussard, M. A. -P. Brown, R. Carr, S. Currie, X. Ding, B. W. Filippone, A. García, P. Geltenbort, J. Hoagland, A. T. Holley, R. Hong, T. M. Ito, A. Knecht, C. -Y. Liu, J. L. Liu, M. Makela, R. R. Mammei, J. W. Martin, D. Melconian, M. P. Mendenhall, S. D. Moore, C. L. Morris, R. W. Pattie Jr., A. Pérez Galván, R. Picker, M. L. Pitt, Bradley R. Plaster

Physics and Astronomy Faculty Publications

Precision measurements of free-neutron β decay have been used to precisely constrain our understanding of the weak interaction. However, the neutron Fierz interference term b_n, which is particularly sensitive to beyond-standard-model tensor currents at the TeV scale, has thus far eluded measurement. Here we report the first direct constraints on this term, finding b_n = 0.067 ± 0.005_{stat^+0.090-0.061sys}, consistent with the standard model. The uncertainty is dominated by absolute energy reconstruction and the linearity of the β spectrometer energy response.

Precision Measurement Of The Radiative Β Decay Of The Free Neutron, M. J. Bales, R. Alarcon, C. D. Bass, E. J. Beise, H. Breuer, J. Byrne, T. E. Chupp, K. J. Coakley, R. L. Cooper, M. S. Dewey, Susan Gardner, T. R. Gentile, D. He, H. P. Mumm, J. S. Nico, B. O'Neill, A. K. Thompson, F. E. Wietfeldt

Physics and Astronomy Faculty Publications

The standard model predicts that, in addition to a proton, an electron, and an antineutrino, a continuous spectrum of photons is emitted in the β decay of the free neutron. We report on the RDK II experiment which measured the photon spectrum using two different detector arrays. An annular array of bismuth germanium oxide scintillators detected photons from 14 to 782 keV. The spectral shape was consistent with theory, and we determined a branching ratio of 0.00335 ± 0.00005[stat] ± 0.00015[syst]. A second detector array of large area avalanche photodiodes directly detected photons from 0.4 to 14 keV. For this …