Angular distribution of neutron inverse beta decay, anti-neutrino(e) + p ---> e+ + n

Mar, 1999
10 pages
Published in:
  • Phys.Rev.D 60 (1999) 053003
e-Print:

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Abstract:
The reaction νˉe+pe++n\bar{\nu}_e + p \to e^+ + n is very important for low-energy (Eν60E_\nu \lesssim 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 Eν60E_\nu \lesssim 60 MeV by calculating to O(1/M){\cal O}(1/M), where MM is the nucleon mass. The correct angular distribution is useful for separating νˉe+pe++n\bar{\nu}_e + p \to 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 νˉe+de++n+n\bar{\nu}_e + d \to e^+ + n + n and νe+de+p+p\nu_e + d \to e^- + p + p. Finally, in the reaction νˉe+pe++n\bar{\nu}_e + p \to 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.
  • antineutrino p: exclusive reaction
  • antineutrino/e: flux
  • charged current
  • angular distribution: (n positron)
  • differential cross section
  • expansion: mass
  • nucleon: mass
  • channel cross section: energy dependence
  • angular distribution: energy dependence
  • deuteron: fission