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Abstract
The oscillation of the neutron n into mirror neutron n′, its partner from the dark mirror sector, can gradually transform an ordinary neutron star into a mixed star consisting in part of mirror dark matter. The implications of the reverse process taking place in the mirror neutron stars depend on the sign of baryon asymmetry in the mirror sector. Namely, if it is negative, as predicted by certain baryogenesis scenarios, then n′¯−n¯ transitions create a core of our antimatter gravitationally trapped in the mirror star interior. The annihilation of accreted gas on such antimatter cores could explain the origin of γ-source candidates with an unusual spectrum compatible with baryon–antibaryon annihilation, recently identified in the Fermi LAT catalog. In addition, some part of this antimatter escaping after the mergers of mirror neutron stars can produce the flux of cosmic antihelium and also heavier antinuclei which are hunted in the AMS-02 experiment.
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Broussard LJ, Barrow JL, DeBeer-Schmitt L, Dennis T, Fitzsimmons MR, Frost MJ, Gilbert CE, Gonzalez FM, Heilbronn L, Iverson EB, Johnston A, Kamyshkov Y, Kline M, Lewiz P, Matteson C, Ternullo J, Varriano L, Vavra S. Experimental Search for Neutron to Mirror Neutron Oscillations as an Explanation of the Neutron Lifetime Anomaly. PHYSICAL REVIEW LETTERS 2022; 128:212503. [PMID: 35687456 DOI: 10.1103/physrevlett.128.212503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 03/25/2022] [Accepted: 05/04/2022] [Indexed: 06/15/2023]
Abstract
An unexplained >4σ discrepancy persists between "beam" and "bottle" measurements of the neutron lifetime. A new model proposed that conversions of neutrons n into mirror neutrons n^{'}, part of a dark mirror sector, can increase the apparent neutron lifetime by 1% via a small mass splitting Δm between n and n^{'} inside the 4.6 T magnetic field of the National Institute of Standards and Technology Beam Lifetime experiment. A search for neutron conversions in a 6.6 T magnetic field was performed at the Spallation Neutron Source which excludes this explanation for the neutron lifetime discrepancy.
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Affiliation(s)
- L J Broussard
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - J L Barrow
- Department of Physics, University of Tennessee, Knoxville, Tennessee 37996, USA
| | | | - T Dennis
- Department of Physics and Astronomy, East Tennessee State University, Johnson City, Tennessee 37614, USA
| | - M R Fitzsimmons
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Department of Physics, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - M J Frost
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - C E Gilbert
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - F M Gonzalez
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - L Heilbronn
- Department of Nuclear Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - E B Iverson
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A Johnston
- Department of Physics, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Y Kamyshkov
- Department of Physics, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - M Kline
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - P Lewiz
- Department of Physics, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - C Matteson
- Department of Physics, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - J Ternullo
- Department of Physics, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - L Varriano
- Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - S Vavra
- Department of Physics, University of Tennessee, Knoxville, Tennessee 37996, USA
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Abstract
The neutron lifetime anomaly has been used to motivate the introduction of new physics with hidden-sector particles coupled to baryon number, and on which neutron stars provide powerful constraints. Although the neutron lifetime anomaly may eventually prove to be of mundane origin, we use it as motivation for a broader review of the ways that baryon number violation, be it real or apparent, and dark sectors can intertwine and how neutron star observables, both present and future, can constrain them.
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A Search for Neutron to Mirror Neutron Oscillation Using Neutron Electric Dipole Moment Measurements. Symmetry (Basel) 2022. [DOI: 10.3390/sym14030487] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Baryon number violation is a key ingredient of baryogenesis. It has been hypothesized that there could also be a parity-conjugated copy of the standard model particles, called mirror particles. The existence of such a mirror universe has specific testable implications, especially in the domain of neutral particle oscillation, viz. the baryon number violating neutron to mirror-neutron (n−n′) oscillation. Consequently, there were many experiments that have searched for n−n′ oscillation, and imposed constraints upon the parameters that describe it. Recently, further analysis on some of these results have identified anomalies which could point to the detection of n−n′ oscillation. All the previous efforts searched for n−n′ oscillation by comparing the relative number of ultracold neutrons that survive after a period of storage for one or both of the two cases: (i) comparison of zero applied magnetic field to a non-zero applied magnetic field, and (ii) comparison where the orientation of the applied magnetic field was reversed. However, n−n′ oscillations also lead to variations in the precession frequency of polarized neutrons upon flipping the direction of the applied magnetic field. Precession frequencies are measured, very precisely, by experiments searching for the electric dipole moment. For the first time, we used the data from the latest search for the neutron electric dipole moment to constrain n−n′ oscillation. After compensating for the systematic effects that affect the ratio of precession frequencies of ultracold neutrons and cohabiting 199Hg-atoms, chief among which was due to their motion in non-uniform magnetic field, we constrained any further perturbations due to n−n′ oscillation. We thereby provide a lower limit on the n−n′ oscillation time constant of τnn′/|cos(β)|>5.7s,0.36T′<B′<1.01T′ (95% C.L.), where β is the angle between the applied magnetic field and the ambient mirror magnetic field. This constraint is the best available in the range of 0.36T′<B′<0.40T′.
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Abstract
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.
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