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Angular distribution of neutron inverse beta decay, ν̅e+p→e++n

Vogel, P. and Beacom, J. F. (1999) Angular distribution of neutron inverse beta decay, ν̅e+p→e++n. Physical Review D, 60 (5). Art. No. 053003. ISSN 0556-2821. http://resolver.caltech.edu/CaltechAUTHORS:VOGprd99

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Abstract

The reaction ν̅e+p→e++n is very important for low-energy (Eν≲60 MeV) antineutrino experiments. In this paper we calculate the positron angular distribution, which at low energies is slightly backward. We show that weak magnetism and recoil corrections have a large effect on the angular distribution, making it isotropic at about 15 MeV and slightly forward at higher energies. We also show that the behavior of the cross section and the angular distribution can be well understood analytically for Eν≲60 MeV by calculating to O(1/M), where M is the nucleon mass. The correct angular distribution is useful for separating ν̅e+p→e++n events from other reactions and detector backgrounds, as well as for possible localization of the source (e.g., a supernova) direction. We comment on how similar corrections appear for the lepton angular distributions in the deuteron breakup reactions ν̅e+d→e++n+n and νe+d→e-+p+p. Finally, in the reaction ν̅e+p→e++n, the angular distribution of the outgoing neutrons is strongly forward peaked, leading to a measurable separation in positron and neutron detection points, also potentially useful for rejecting backgrounds or locating the source direction.


Item Type:Article
Additional Information:©1999 The American Physical Society Received 1 April 1999; published 27 July 1999 This work was supported in part by the U.S. Department of Energy under Grant No. DE-FG03-88ER-40397. J.F.B. was supported by Caltech. We also thank the Aspen Center for Physics, where part of this work was done. We thank Gerry Garvey and Bill Louis for discussions of the angular distribution of the candidate n¯ e events observed in LSND; Brian Fujikawa and Gerry Garvey for discussions of weak magnetism; Carlo Bemporad, Felix Boehm, Yves Declais, and Andreas Piepke for discussions of the positron-neutron separation in the detection of reactor antineutrinos; and Kuniharu Kubodera for providing and explaining his numerical tables of the charged-current neutrino-deuteron differential cross sections.
Record Number:CaltechAUTHORS:VOGprd99
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:VOGprd99
Alternative URL:http://dx.doi.org/10.1103/PhysRevD.60.053003
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2796
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:27 Apr 2006
Last Modified:26 Dec 2012 08:51

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