dc.contributor.author
Thyagarthi Mohanmurthy, Prajwal
dc.contributor.supervisor
Kirch, Klaus Stefan
dc.contributor.supervisor
Zsigmond, Géza
dc.contributor.supervisor
Grab, Christophorus
dc.date.accessioned
2020-06-04T06:01:16Z
dc.date.available
2020-06-03T13:52:52Z
dc.date.available
2020-06-04T06:01:16Z
dc.date.issued
2020
dc.identifier.uri
http://hdl.handle.net/20.500.11850/417951
dc.identifier.doi
10.3929/ethz-b-000417951
dc.description.abstract
Lee and Yang had noted, in their Nobel prize winning paper, that observation of apparent parity violation in the weak interaction of particles could be mitigated with the introduction of a parity conjugated copy of the same particles. The existence of a parity conjugated copy in terms of the weak interaction of normal matter, called mirror matter, that does not interact with normal matter through known forces, has long been theorized. Baryon number violation is required for baryogenesis in order to explain the observed asymmetry between matter and antimatter in the universe. Neutron to mirror-neutron oscillations could be an observable baryon number violating process. In late 2000s, it was pointed out that the oscillation time of such neutron to mirror-neutron oscillation could be of the order of a few seconds, and that a magnetic field dependent ultracold neutron storage measurement could be sensitive to such oscillations. Furthermore, it was also shown that the ambient mirror magnetic field on the surface of the Earth could be as high as the Earth's magnetic field. Subsequently, two separate groups performed experiments at the Institut Laue-Langevin in search of neutron to mirror-neutron oscillations and reported having found no evidence. The limit set on the oscillation time was $\tau_{nn'} > 414~$s (90\% C.L.) for the case where the mirror magnetic field, $B'=0$, and $\tau_{nn'}>12~$s (95\% C.L.) for the case where $B'\in(0,12.5)~\mu$T. These constraints have since been improved to $\tau_{nn'} > 448~$s (90\% C.L., $B'=0$), $\tau_{nn'} > 17~\text{s}~\forall~B'\in(8,17)~\mu\text{T (95\% C.L.)}$, and $\tau_{nn'} > 27~\text{s}~\forall~B'\in(6,25)~\mu\text{T (95\% C.L.)}$. Soon after, when the results of these experiments were further analyzed by Berezhiani et al., $5\sigma$, $3\sigma$, and $2.5\sigma$ statistically significant signals for mirror-neutron oscillation in the presence of a non zero mirror magnetic field were reported. The current leading constraints upon $\tau_{nn'}$ do not exclude these signals. Thus a new experiment was required to test these claimed signals. The neutron electric dipole moment experiment based at the Paul Scherrer Institute performed a dedicated search to investigate these signals and found no evidence of neutron mirror-neutron oscillations. We thereby impose the following new lower limits on the oscillation time: $\tau_{nn'} > 388~$s (90\% C.L., $B'=0$), $\tau_{nn'} > 6~\text{s}~\forall~B'\in(0.38,25.66)~\mu\text{T (95\% C.L.)}$, and $\left(\tau_{nn'}/\sqrt{\cos(\beta)}\right) > 9~\text{s}~\forall~B'\in(5.04,25.39)~\mu\text{T (95\% C.L.)}$, where $\beta$ is the fixed angle between the applied magnetic field and the ambient mirror magnetic field, which is bound to the reference frame of the Earth. For the case when the mirror magnetic field is fixed in the cosmos, we have also for the first time placed the following constraints: $\tau^{\Omega_{\bigoplus}}_{nn'} > 7~\text{s (95\% C.L.)}~\forall~B'\in(5.20,24.43)~\mu\text{T}$, $\tau^{\Omega_{2\bigoplus}}_{nn'}~>~6~\text{s}~\forall~B'\in(5.51,25.78)~\mu\text{T}~(95\%~\text{C.L.})$, $\tau^{\Omega_{\bigodot}}_{nn'}~>~4~\text{s}~\forall~B'\in(6.77,27.18)~\mu\text{T}~(95\%~\text{C.L.})$, and $\tau^{\Omega_{2\bigodot}}_{nn'}~>~5~\text{s}~\forall~B'\in(4.20,24.17)~\mu\text{T}~(95\%~\text{C.L.})$, for modulation frequencies associated with one sidereal day, half a sidereal day, an annual year, and half an annual year, respectively. Our new constraints in the assumption of a mirror magnetic field bound to Earth are the best constraints around $B'\sim10~\mu$T, and also in the region where the mirror magnet field falls in the range of $B'>37~\mu$T. While this result excludes large portions of the three statistically significant signals indicated by Berezhiani et al., especially where at least two signal regions overlap, it does not exclude all the signals. We therefore need further tests of these signals in the vicinity of $B'\in(4,37)~\mu$T.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.rights.uri
http://rightsstatements.org/page/InC-NC/1.0/
dc.subject
NUCLEAR PHYSICS
en_US
dc.subject
PARTICLE PHYSICS
en_US
dc.title
A Search for Neutron to Mirror-Neutron Oscillations
en_US
dc.type
Doctoral Thesis
In Copyright - Non-Commercial Use Permitted
dc.date.published
2020-06-04
ethz.size
242 p.
en_US
ethz.code.ddc
DDC - DDC::5 - Science::530 - Physics
en_US
ethz.notes
This work was supported by SERI-FCS award # 2015.0594 and Sigma Xi grants # G2017100190747806 and # G2019100190747806
en_US
ethz.identifier.diss
26525
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02010 - Dep. Physik / Dep. of Physics::02532 - Institut für Teilchen- und Astrophysik / Inst. Particle Physics and Astrophysics
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02010 - Dep. Physik / Dep. of Physics::02532 - Institut für Teilchen- und Astrophysik / Inst. Particle Physics and Astrophysics::03864 - Kirch, Klaus / Kirch, Klaus
en_US
ethz.leitzahl.certified
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02010 - Dep. Physik / Dep. of Physics::02532 - Institut für Teilchen- und Astrophysik / Inst. Particle Physics and Astrophysics::03864 - Kirch, Klaus / Kirch, Klaus
en_US
ethz.tag
Properties of neutrons
en_US
ethz.tag
Ultracold neutrons
en_US
ethz.tag
Nuclear matter
en_US
ethz.tag
Mirror matter
en_US
ethz.tag
Dark matter
en_US
ethz.tag
Particle symmetries
en_US
ethz.date.deposited
2020-06-03T13:53:00Z
ethz.source
FORM
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.rosetta.installDate
2020-06-04T06:01:28Z
ethz.rosetta.lastUpdated
2021-02-15T11:58:12Z
ethz.rosetta.versionExported
true
ethz.COinS
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