Effect of a Constant Magnetic Field on the Neutron Beta Decay Rate and its Astrophysical Implications

Abstract

RECENT advances in the production of large magnetic fields in the laboratory1,2 have generated interest in the effect of intense magnetic fields on various phenomena3,4. The largest field that can be produced in the laboratory1,2 at present is about 106 G, which is considerably lower than the quantum critical field value5 of Hc = m2c3/eV = 4.4 × 1013 G; but the “cosmic laboratory” may be a source of much stronger fields and it has been suggested6 that magnetic fields as large as 1014−1016 G may exist in neutron stars. Hoyle7 has cited the possibility of a large primordial magnetic field, and Brownell and Callaway8 speculate that neutron stars and the dense early universe may be ferromagnetic. One of us (R. F. O.) has examined9 various effects of a large magnetic field and has indicated an effect of magnetic fields which has been often ignored in astrophysical investigations, namely, that the rates of all elementary particle processes will be affected. Pursuing this idea, we examine here the effect of a magnetic field on the β decay rate of a neutron. This is a fundamental process in many astrophysical phenomena and in particular it is very important10 in a problem of current interest, that is, the production of He in the “big-bang” expansion of the universe11. In addition, our calculations should be applicable to other elementary particle processes. We present here only the main ideas ; the calculation details will be published elsewhere12.