Gauged B-L Number and Neutron--Antineutron Oscillation: Long-range Forces Mediated by Baryophotons

Transformation of neutron to antineutron is a small effect that has not yet been experimentally observed. %\cite{Phillips:2014fgb}. In principle, it can occur with free neutrons in the vacuum or with bound neutrons inside the nuclear environment different for neutrons and antineutrons and for that reason in the latter case it is heavily suppressed. Free neutron transformation also can be suppressed if environmental vector field exists destinguishing neutron from antineutron. We consider here the case of a vector field coupled to $B-L$ charge of the particles ($B-L$ photons) and study a possibility of this to lead to the observable suppression of neutron to antineutron transformation. The suppression effect however can be removed by applying external magnetic field. If the neutron--antineutron oscillation will be discovered in free neutron oscillation experiments, this will imply limits on $B-L$ photon coupling constant and interaction radius few order of magnitudes stronger than present limits form the tests of the equivalence principle. If $n-\bar n$ oscillation will be discovered via nuclear instability, but not in free neutron oscillations in corresponding level, this would indicate to the presence of fifth-forces mediated by such baryophotons.Comment: 13 pages, 4 figure

Neutron-Mirror Neutron Oscillations in Absorbing Matter

The possibility that a neutron can be transformed to a hidden sector particle remains intriguingly open. Proposed theoretical models conjecture that the hidden sector can be represented by a mirror sector, and the neutron n can oscillate into its sterile mirror twin n′, exactly or nearly degenerate in mass with n. Oscillations n−n′ can take place in vacuum or in an environment containing regular matter and a magnetic field, in which only the neutron will be subject to interactions with the environment. We describe the propagation of the oscillating n−n′ system in a cold neutron beam passing through dense absorbing materials in connection to the possible regeneration type of experiments, where the effect of n→n′→n transformation can be observed

Signatures of Nucleon Disappearance in Large Underground Detectors

For neutrons bound inside nuclei, baryon instability can manifest itself as a decay into undetectable particles (e.g., $\it n \to \nu \nu \bar{\nu}$), i.e., as a disappearance of a neutron from its nuclear state. If electric charge is conserved, a similar disappearance is impossible for a proton. The existing experimental lifetime limit for neutron disappearance is 4-7 orders of magnitude lower than the lifetime limits with detectable nucleon decay products in the final state [PDG2000]. In this paper we calculated the spectrum of nuclear de-excitations that would result from the disappearance of a neutron or two neutrons from $^{12}$C. We found that some de-excitation modes have signatures that are advantageous for detection in the modern high-mass, low-background, and low-threshold underground detectors, where neutron disappearance would result in a characteristic sequence of time- and space-correlated events. Thus, in the KamLAND detector [Kamland], a time-correlated triple coincidence of a prompt signal, a captured neutron, and a $\beta^{+}$ decay of the residual nucleus, all originating from the same point in the detector, will be a unique signal of neutron disappearance allowing searches for baryon instability with sensitivity 3-4 orders of magnitude beyond the present experimental limits.Comment: 13 pages including 6 figures, revised version, to be published in Phys.Rev.

Production of Single W Bosons at LEP

We report on the observation of single W boson production in a data sample collected by the L3 detector at LEP2. The signal consists of large missing energy final states with a single energetic lepton or two hadronic jets. The cross-section is measured to be $0.61^{+0.43}_{-0.33} \pm 0.05 \; \rm{pb}$ at the centre of mass energy \sqrt{s}=172 \GeV{}, consistent with the Standard Model expectation. From this measurement the following limits on the anomalous $\gamma$WW gauge couplings are derived at 95\% CL: $\rm -3.6 \Delta \kappa_\gamma 1.5$ and $\rm -3.6 \lambda_\gamma 3.6$