Research

21 pages, 401 KiB

Open AccessFeature PaperArticle

Theoretical Constraints on Neutron-Mirror-Neutron Oscillation

by Kaladi S. Babu and Rabindra N. Mohapatra

Symmetry 2022, 14(4), 731; https://doi.org/10.3390/sym14040731 - 03 Apr 2022

Cited by 13 | Viewed by 3775

Mirror models lead to the possibility that neutron (n) can oscillate into its mirror partner (

n^{'}

), inspiring several experimental searches for this phenomenon. The condition for observability of this oscillation is a high degree of degeneracy between the [...] Read more.

Mirror models lead to the possibility that neutron (n) can oscillate into its mirror partner (

n^{'}

), inspiring several experimental searches for this phenomenon. The condition for observability of this oscillation is a high degree of degeneracy between the n and

n^{'}

masses, which can be guaranteed if there is exact parity symmetry taking all particles to their mirror partners. However, consistency of these models with big-bang nucleosynthesis requires that this parity symmetry be broken in the early universe in a scenario called asymmetric inflation. In this paper, we study the consistency of an observable

n - n^{'}

oscillations signal with asymmetric inflation and derive various theoretical constraints. In particular, we find that the reheat temperature after inflation should lie below 2.5 TeV, and we predict a singlet fermion with a mass below 100 GeV. In simple models, where the right-handed neutrino is a mediator of baryon-number-violating interactions, we find that the light neutrinos are Dirac fermions with their masses arising radiatively through one-loop diagrams. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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10 pages, 424 KiB

Open AccessFeature PaperArticle

Topological Portals from Matter to Antimatter

by Andrea Addazi

Symmetry 2022, 14(3), 551; https://doi.org/10.3390/sym14030551 - 08 Mar 2022

Cited by 1 | Viewed by 1618

Abstract

We discuss possibilities of generating a Majorana mass for the neutron from topological quantum gravity effects which survive at mesoscopic scales from decoherence. We show how virtual micro-black hole (BH) pairs with skyrme/baryon hairs induce a neutron–antineutron transition which can be tested in [...] Read more.

We discuss possibilities of generating a Majorana mass for the neutron from topological quantum gravity effects which survive at mesoscopic scales from decoherence. We show how virtual micro-black hole (BH) pairs with skyrme/baryon hairs induce a neutron–antineutron transition which can be tested in next generation of experiments. Such effects do not destabilize the proton. We also discuss how BHs with mix ordinary and mirror baryon hairs can mediate neutron-mirror neutron mixings. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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62 pages, 6768 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Neutron Stars with Baryon Number Violation, Probing Dark Sectors

by Jeffrey M. Berryman, Susan Gardner and Mohammadreza Zakeri

Symmetry 2022, 14(3), 518; https://doi.org/10.3390/sym14030518 - 02 Mar 2022

Cited by 27 | Viewed by 6777

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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22 pages, 6035 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Improved Search for Neutron to Mirror-Neutron Oscillations in the Presence of Mirror Magnetic Fields with a Dedicated Apparatus at the PSI UCN Source

by Nicholas J. Ayres, Zurab Berezhiani, Riccardo Biondi, Georg Bison, Kazimierz Bodek, Vira Bondar, Pin-Jung Chiu, Manfred Daum, Reza Tavakoli Dinani, Cornelis B. Doorenbos, Solange Emmenegger, Klaus Kirch, Victoria Kletzl, Jochen Krempel, Bernhard Lauss, Duarte Pais, Ingo Rienäcker, Dieter Ries, Nicola Rossi, Dagmara Rozpedzik, Philipp Schmidt-Wellenburg, Kazuo S. Tanaka, Jacek Zejma, Nathalie Ziehl and Geza Zsigmond Show full author list Hide full author list

Symmetry 2022, 14(3), 503; https://doi.org/10.3390/sym14030503 - 01 Mar 2022

Cited by 18 | Viewed by 5912

Abstract

While the international nEDM collaboration at the Paul Scherrer Institut (PSI) took data in 2017 that covered a considerable fraction of the parameter space of claimed potential signals of hypothetical neutron (n) to mirror-neutron (

n^{'}

) transitions, it could [...] Read more.

While the international nEDM collaboration at the Paul Scherrer Institut (PSI) took data in 2017 that covered a considerable fraction of the parameter space of claimed potential signals of hypothetical neutron (n) to mirror-neutron (

n^{'}

) transitions, it could not test all claimed signal regions at various mirror magnetic fields. Therefore, a new study of

n - n^{'}

oscillations using stored ultracold neutrons (UCNs) is underway at PSI, considerably expanding the reach in parameter space of mirror magnetic fields (

B^{'}

) and oscillation time constants (

τ_{n n^{'}}

). The new apparatus is designed to test for the anomalous loss of stored ultracold neutrons as a function of an applied magnetic field. The experiment is distinguished from its predecessors by its very large storage vessel (1.47 m³), enhancing its statistical sensitivity. In a test experiment in 2020 we have demonstrated the capabilities of our apparatus. However, the full analysis of our recent data is still pending. Based on already demonstrated performance, we will reach sensitivity to oscillation times

τ_{n n^{'}} / \sqrt{cos (β)}

well above a hundred seconds, with

β

being the angle between

B^{'}

and the applied magnetic field B. The scan of B will allow the finding or the comprehensive exclusion of potential signals reported in the analysis of previous experiments and suggested to be consistent with neutron to mirror-neutron oscillations. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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14 pages, 1441 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Search for Neutron to Mirror Neutron Oscillation Using Neutron Electric Dipole Moment Measurements

by Prajwal Mohanmurthy, Albert R. Young, Jeff A. Winger and Geza Zsigmond

Symmetry 2022, 14(3), 487; https://doi.org/10.3390/sym14030487 - 28 Feb 2022

Cited by 9 | Viewed by 2448

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 [...] Read more.

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

^{199}

Hg-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

τ_{n n^{'}} / \sqrt{| cos (β) |} > 5.7 s, 0.36 T^{'} < B^{'} < 1.01 T^{'}

(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

0.36 T^{'} < B^{'} < 0.40 T^{'}

. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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13 pages, 567 KiB

Open AccessEditor’s ChoiceArticle

Neutron-Mirror Neutron Oscillations in Absorbing Matter

by Yuri Kamyshkov, James Ternullo, Louis Varriano and Zurab Berezhiani

Symmetry 2022, 14(2), 230; https://doi.org/10.3390/sym14020230 - 25 Jan 2022

Cited by 10 | Viewed by 2267

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 [...] Read more.

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 \to n^{'} \to n

transformation can be observed. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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17 pages, 2519 KiB

Open AccessArticle

Status of the Design of an Annihilation Detector to Observe Neutron-Antineutron Conversions at the European Spallation Source

by Sze-Chun Yiu, Bernhard Meirose, Joshua Barrow, Christian Bohm, Gustaaf Brooijmans, Katherine Dunne, Elena S. Golubeva, David Milstead, André Nepomuceno, Anders Oskarsson, Valentina Santoro and Samuel Silverstein

Symmetry 2022, 14(1), 76; https://doi.org/10.3390/sym14010076 - 05 Jan 2022

Cited by 8 | Viewed by 1871

Abstract

The goal of the HIBEAM/NNBAR program is to search for baryon number violation via the conversion or oscillation of neutrons into sterile neutrons and/or antineutrons at the European Spallation Source. A key experimental component of the program is the construction of an annihilation [...] Read more.

The goal of the HIBEAM/NNBAR program is to search for baryon number violation via the conversion or oscillation of neutrons into sterile neutrons and/or antineutrons at the European Spallation Source. A key experimental component of the program is the construction of an annihilation detector to directly observe the production of an antineutron following the oscillation. Design studies for the annihilation detector are presented. The predicted response of the detector models are studied using Geant4 simulations made with Monte Carlo simulations of the annihilation signal topology and cosmic ray backgrounds. Particle identification and sensitive discriminating observables, such as invariant mass and sphericity, are shown. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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19 pages, 556 KiB

Open AccessArticle

Searches for Exotic Interactions Using Neutrons

by William Michael Snow, Chris Haddock and Ben Heacock

Symmetry 2022, 14(1), 10; https://doi.org/10.3390/sym14010010 - 22 Dec 2021

Cited by 10 | Viewed by 2629

Abstract

Slow neutrons possess several advantageous properties which make them useful probes for a variety of exotic interactions, including some that can form at least some components of the dark matter of interest for this issue of Symmetry. We discuss the relevant neutron properties, [...] Read more.

Slow neutrons possess several advantageous properties which make them useful probes for a variety of exotic interactions, including some that can form at least some components of the dark matter of interest for this issue of Symmetry. We discuss the relevant neutron properties, describe some of the recent work that has been done along these lines using neutron experiments mainly with cold and ultra-cold neutrons, and outline some interesting and exciting opportunities which can be pursued using resonant epithermal neutron interactions in heavy nuclei. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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18 pages, 703 KiB

Open AccessArticle

A Possible Neutron-Antineutron Oscillation Experiment at PF1B at the Institut Laue Langevin

by Vladimir Gudkov, Esben Klinby, Bernhard Meirose, David Milstead, Valery V. Nesvizhevsky, Konstantin V. Protasov, Nicola Rizzi, Valentina Santoro, William Michael Snow, Richard Wagner and Sze-Chun Yiu

Symmetry 2021, 13(12), 2314; https://doi.org/10.3390/sym13122314 - 03 Dec 2021

Cited by 6 | Viewed by 1956

Abstract

We consider a possible neutron–antineutron (

n - \bar{n}

) oscillation experiment at the PF1B instrument at Institut Laue Langevin. It can improve the best existing constraint on the transition rate and also allow the testing of the methods and instrumentation which [...] Read more.

We consider a possible neutron–antineutron (

n - \bar{n}

) oscillation experiment at the PF1B instrument at Institut Laue Langevin. It can improve the best existing constraint on the transition rate and also allow the testing of the methods and instrumentation which would be needed for a later larger-scale experiment at ESS. The main gain factors over the most competitive experiment, performed earlier at PF1 instrument at ILL, are: a more intense neutron beam and a new operating mode based on coherent n and

\bar{n}

mirror reflections. The installation of such an experiment would need a temporary replacement of the existing ballistic neutron guide by a specially designed

n / \bar{n}

guide with a gradually increasing cross section and a specially selected coating as well as the development and construction of an advanced

\bar{n}

annihilation detector with a high efficiency and low background. The overall gain factor could reach up to an order of magnitude and depends on the chosen experiment configuration. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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12 pages, 279 KiB

Open AccessArticle

Neutron Oscillations and the Parity Doubling Theorem

by Kazuo Fujikawa and Anca Tureanu

Symmetry 2021, 13(11), 2202; https://doi.org/10.3390/sym13112202 - 18 Nov 2021

Viewed by 1166

Abstract

We review several aspects of parity and CP violation in the framework of neutron-antineutron oscillations. We focus on the parity doubling theorem, which provides a criterion for neutron oscillation in the general theory with

Δ B = 2

baryon number-violating interactions. We prove [...] Read more.

We review several aspects of parity and CP violation in the framework of neutron-antineutron oscillations. We focus on the parity doubling theorem, which provides a criterion for neutron oscillation in the general theory with

Δ B = 2

baryon number-violating interactions. We prove by explicit calculations that the violation of the conventional parity symmetry with

P^{2} = 1

is the necessary condition for neutron oscillations to happen. While the CP violation is not manifest in the oscillation, it is nevertheless intrinsic to the system, and it is transferred, by the mixing matrix, to the neutron interactions and potentially observable as a contribution to the electric dipole moment. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

10 pages, 325 KiB

Open AccessArticle

Electrodisintegration of Deuteron into Dark Matter and Proton Close to Threshold

by Andrey N. Ivanov, Roman Höllwieser, Nataliya I. Troitskaya, Markus Wellenzohn and Yaroslav A. Berdnikov

Symmetry 2021, 13(11), 2169; https://doi.org/10.3390/sym13112169 - 12 Nov 2021

Viewed by 1065

Abstract

We discuss an investigation of the dark matter decay modes of the neutron, proposed by Fornal and Grinstein (2018–2020), Berezhiani (2017, 2018) and Ivanov et al. (2018) for solution of the neutron lifetime anomaly problem, through the analysis of the electrodisintegration of the [...] Read more.

We discuss an investigation of the dark matter decay modes of the neutron, proposed by Fornal and Grinstein (2018–2020), Berezhiani (2017, 2018) and Ivanov et al. (2018) for solution of the neutron lifetime anomaly problem, through the analysis of the electrodisintegration of the deuteron d into dark matter fermions

χ

and protons p close to threshold. We calculate the triple-differential cross section for the reaction

e^{-} + d \to χ + p + e^{-}

and propose to search for such a dark matter channel in coincidence experiments on the electrodisintegration of the deuteron

e^{-} + d \to n + p + e^{-}

into neutrons n and protons close to threshold with outgoing electrons, protons, and neutrons in coincidence. An absence of neutron signals should testify to a detection of dark matter fermions. Full article

(This article belongs to the Special Issue The Neutron Physics - Dark Matter Connection: Bridge Through the Baryon Symmetry Violation)

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