Anomalous internal pair creation
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Regular Article -Theoretical Physics
Anomalous internal pair creation Péter Kálmán, Tamás Keszthelyia Institute of Physics, Budapest University of Technology and Economics, Budafoki út 8. F., Budapest 1521, Hungary
Received: 26 May 2020 / Accepted: 16 July 2020 © The Author(s) 2020 Communicated by Reinhard Alkofer
Abstract In recent electron-positron angular correlation measurements the observed significant enhancements relative to the internal pair creation at large angles was interpreted as indication of the creation of J π = 1+ boson called X17 particle. In this paper it is brought up that such enhancements can be generated by higher order processes. It is found that nuclear transitions, the transition energy of which is significantly lower than the whole transition energy, can cause peaked angle dependence in electron-positron angular correlation.
1 Introduction The anomalies in the spectra of emitted positrons observed in heavy-ion collisions at GSI (Darmstadt) in the 1980’s [1– 4] inspired experimentalists after the suggestions of [5,6] to search for traces of a short-lived neutral particle [7,8] produced in nuclear decays. The observed significant deviations from internal pair conversion [9,10] sustained the interest [11,12] searching for a light neutral boson [13] which is called X17-boson. Interpreting recent experiments, it was stated that ’to the best of our knowledge, the observed anomaly can not have a nuclear physics related origin’ [14]. In this paper it is shown that effects of nuclear physics origin can also contribute to the presence of the observed anomaly. In the experiments [14,15] and [16] the decay of excited nuclear states through internal electron (e− ) - positron (e+ ) pair creation (IPC) was studied. The examined process was assumed to take place in two successive steps. First, the excited states of nuclei were prepared in resonant (p,γ ) reactions. Pair creation is expected after it in a second order electromagnetic scattering process [17–20]. The dependence of the IPC yield fulfilling the E − + E + = constraint was investigated [14,15] where is the angle between the a e-mail:
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momenta p− = h¯ k− and p+ = h¯ k+ of the emitted e− and e+ particles. E − , E + and k− , k+ are the energies and the wave vectors of e− and e+ , respectively. is the energy of the resonantly excited transition and h¯ is the reduced Planckconstant. Extra events, which were said to be unexplainable with IPC, were found. It was supposed that paralell with the usual e− e+ pair creation, which is the usual IPC, the decay of the state may also take place by emitting a hypothetical X17-boson that also decays by e− e+ pair creation having characteristic dependence. If these extra e− e+ events originate from the decay of the X17 boson then its rest mass can be determined with the aid of the given dependence of the peaking anomaly appearing around a definite large angle. Two different experiments [14,15] resulted rest masses identical within
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