Eur. Phys. J. C (2021) 81: 33
https://doi.org/10.1140/epjc/s10052-020-08824-9

Letter

A possible shortcut for neutron–antineutron oscillation through mirror world

¹ Dipartimento di Fisica e Chimica, Università di L’Aquila, 67100, Coppito, L’Aquila, Italy
² INFN, Laboratori Nazionali del Gran Sasso, 67010, Assergi, L’Aquila, Italy

^a zurab.berezhiani@aquila.infn.it

Received: 9 March 2020
Accepted: 20 November 2020
Published online: 16 January 2021

Abstract

Existing bounds on the neutron-antineutron mass mixing, ${ϵ}_{n\overline{n}}<\mathrm{few}\times {10}^{-24}$ eV, impose a severe upper limit on $n-\overline{n}$ transition probability, $P_{n\overline{n}}(t)<{(t/0.1\mathrm{s})}^2\times {10}^{-18}$ or so, where t is the neutron flight time. Here we propose a new mechanism of $n-\overline{n}$ transition which is not induced by direct mass mixing ${ϵ}_{n\overline{n}}$ but is mediated instead by the neutron mass mixings with the hypothetical states of mirror neutron $n^{\prime }$ and mirror antineutron ${\overline{n}}^{\prime }$. The latter can be as large as ${ϵ}_{n{n}^{\prime }},{ϵ}_{n{\overline{n}}^{\prime }}\sim {10}^{-15}$ eV or so, without contradicting present experimental limits and nuclear stability bounds. The probabilities of $n-n^{\prime }$ and $n-{\overline{n}}^{\prime }$ transitions, $P_{n{n}^{\prime }}$ and $P_{n{\overline{n}}^{\prime }}$, depend on environmental conditions in mirror sector, and they can be resonantly amplified by applying the magnetic field of the proper value. This opens up a possibility of $n-\overline{n}$ transition with the probability $P_{n\overline{n}}\simeq P_{n{n}^{\prime }}{P}_{n{\overline{n}}^{\prime }}$ which can reach the values $\sim {10}^{-8}$ or even larger. For finding this effect in real experiments, the magnetic field should not be suppressed but properly varied. These mixings can be induced by new physics at the scale of few TeV which may also originate a new low scale co-baryogenesis mechanism between ordinary and mirror sectors.