On neutrino production of heavy neutral leptons

Abstract

Production of heavy neutral leptons by p -.type neutrinos is inves tigated in the framework of a strangeness-conserving neutral current model, ati the analysis is applied to the Ramm effect. The failure to observe such heavy leptons in the K-meson decay spectrum is easily understood, but the large charged current coupling strength required in the heavy lepton decay (well above the universal value) casts considerable doubt on the validity of the effect, Confirmation of the effect would suggest the existence of a new direct pion-muon interaction. (Submitted to Physics Letters B,) * Work supported in part by the U. S. Atomic Energy Commission. t Summer visitor in the Theoretical Physics Division. Permanent address: Northern Illinois University, DeKalb , Illinois 60115. The possible production of heavy leptons in high energy interactions has stimulated both theoretical and experimental interest. 132 Heavy charged leptons could be produced in pairs in high energy e + ecolliding beams or in association with their characteristic neutrinos in high energy ynucleus or enucleus interactions. On the other hand, both charged and neutral heavy leptons could be copiously produced in high energy neutrino interactions if they carry the same muon quantum number as the conventional neutrino probe v . I-1 The purpose of this note is to present some theoretical speculations on neutral heavy lepton production by p-type neutrinos. This study is prompted in part by the observations due to Ramm3 of an apparent peak in the 7~+p(npe) invariant mass spectrum produced in the 1967 CERN V~ ($) experiments. The peaks at 425 MeV suggest the production and subsequent decay of a heavy neutral lepton. This so called Ramm effect has not been highly regarded, for overwhelming evidence demonstrates that no such peaks appear in the r-p mass distribuJ tions from KL + 7rp v decays. 4 We can resolve this apparent contradiction, however, by employing a simple model. Although our analysis tends to emphasize the Ramm effect at 425 MeV, the study applies just as well to some other hypothetical heavy lepton; we select a mass of 1.2 CeV by way of example. The apparent processes in question are and VP + P +p+h” P (1) h;,a++p-. (2) The theoretical model we propose for the production process (1) couples the neutral leptons to the nucleon vertex through a weak neutral current interaction. To be sure, the existence of weakly coupled neutral currents has not been 2demonstrated to date; however, we consider the simplest model consistent with the present data as discussed previously by Albright and Oakes:5 the neutral hadron current is taken to be strangeness-conserving and simply the 3rd component of an isospin triplet. In detail, we write down the weak semileptonic Hamiltonian coupling the p -type heavy lepton according to HSL = s % [ ( Jr) ji-) + Jim) jr) + 2 go Ji3)jr) ) 1 , where Jr) (3) represents the Cabibbo current, Jh is the 3rd component of the V A octet current, and the lepton currents coupling the heavy lepton to the ordinary leptons are given by (3)