Measurement of the exclusive cross sectionC12(ν

R. C. Allen

¹

,

H. H. Chen

²

,

P. J. Doe

³

et al.

Abstract

The neutrino-induced nuclear transition l2 C(v e ,e ~) l2 N(g.s.) has been observed with a 15-ton finegrained tracking detector. The exclusive final state is identified by both an electron track and the positron decay of the ,2 N. From the observation of 181 ± 17 l2 C(v e ,e ~) ,2 N(g.s.) events with subsequent positron decays the flux-averaged cross section, equivalent to the cross section for 35.0-MeV neutrinos, is [1.05 ±0.10(stat) ±0.10(syst)] x 10 ~4 1 cm 2 . This result is in good agreement with recent calculations. PACS numbers: 25.30.Pt, 13.15.DkWe report the measurement of the cross section for l2 C(v e ,e ~) 12 N(g.s.) with v e from a beam-stop neutrino source. This is the first observation of an electron-neutrino-induced reaction between specific nuclear states. 1 Such exclusive reactions are of interest in nuclear physics, astrophysics, and particle physics. Recently, special attention has been drawn to the possibility of using exclusive neutrino reactions for solar-and supernovaneutrino detection. 2 Interpretation of the < t rate in any low-energy neutrino observatory require confidence in calculations for neutrino-induced nuclear transition rates. 3 Furthermore, it has been pointed out that certain specific neutrino-induced reactions may play a pivotal role in the production of intermediate-mass elements such as 19 F. 4 Yet, to date no experimental cross sections were available for neutrino-nucleus interactions to well-defined, two-body final states. This experiment observes such neutrino reactions at energies relevant for astrophysical observations and calculations. Our result provides useful checks of the theoretical calculations and serves as an experimental calibration.This reaction presents a simple case for theoretical calculations as the weak currents are known approximately from the corresponding 12 N p decay. Yet, the observed cross section is about 50% smaller than one estimates from just the 12 N(g.s.) decay rate, because the neutrino reaction occurs over a range of momentum transfers (q 2 ) for which nuclear form factors are important. It is possible to estimate these form factors using appropriate data (electron scattering, muon capture) in combination with the conserved-vector-current (CVC), weak-isospin, and other hypotheses. 5 Indeed, the l2 C(v e ,e ~) ,2 N(g.s.) transition rate is usually treated as

Neutrino-Nucleus Reactions

“…The neutrino energies up to E ν ∼ 100 MeV are expected to be of relevance for stellar collapse neutrinos. Another reason is provided by the intensive programs of beam-dump neutrino experiments at Los Alamos [52,53,54,55] and the Rutherford Laboratory [76,57]. Some of these experiments directly aim at observing the neutrino -12 C reactions.…”

“…Some of these experiments directly aim at observing the neutrino -12 C reactions. In other particle-physics experiments [52] main interest is in the ν − e scattering but here also, to eliminate the dominant background due to the neutrino -12 C reaction, one needs to know its cross sections with reasonable accuracy.…”

Neutrino and antineutrino charge-exchange reactions onC12

“…The neutrino-nucleus scattering on 12 C is important because this nucleus is a component of many liquid scintillator detectors. Experiments such as LSND [1,2], KARMEN [8,9], and LAMPF [10,11] have used 12 C to search for neutrino oscillations, and for measuring neutrino-nucleus cross sections. Present atmospheric and accelerator based neutrino oscillation experiments also involve 12 C, and operate at neutrino energies E ν ∼ 1 GeV in order to access the relevant regions of oscillation parameter space.…”

Non-Gaussian Features of Linear Cosmic String Models

“…Our first step in the present analysis was to perform high-resolution numerical simulations of cosmic string networks in an expanding universe (Allen & Shellard 1990) from which we subsequently computed the causally-sourced density field with either a cold or hot dark matter (CDM or HDM) background. The cosmic string simulations had a dynamic range extending from before the radiation-matter transition at 0.4η eq through to deep into the matter era 8.4η eq , where η eq is the conformal time at radiation-matter density equality.…”