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Prospects for neutron-antineutron transition search
Presently-available sources of free neutrons can allow an improvement in the discovery potential of a neutron-antineutron transition search by four orders of magnitude as compared to that of the most recent reactor-based search experiment performed at ILL in Grenoble. This would be equivalent to a characteristic neutron-antineutron transition time limit of >10{sup 10} seconds. With future dedicated neutron-source Facilities, with further progress in cold-neutron- moderator techniques, and with a vertical experiment layout, the discovery potential could ultimately be pushed by another factor of {approximately}100 corresponding to a characteristic transition time limit of {approximately}10{sup 11} seconds. Prospects for, and relative merits of, a neutron-antineutron oscillation search in intranuclear transitions are also discussed
Solutions to large B and L breaking in the Randall-Sundrum model
The stability of proton and neutrino masses are discussed in the
Randall-Sundrum model. We show that relevant operators should be suppressed, if
the hierarchical Yukawa matrices are explained only by configurations of
wavefunctions for fermions and the Higgs field along the extra dimension. We
assume a discrete gauge symmetry to suppress those operators. In the
Dirac neutrino case, there is an infinite number of symmetries which may forbid
the dangerous operators. In the Majorana neutrino case, the discrete gauge
symmetries should originate from gauge symmetries which are broken on
the Planck brane. We also comment on the oscillation as a
phenomenon which can distinguish those discrete gauge symmetries.Comment: 12 pages, No figures, Added reference
Neutron-Anti-Neutron Oscillation: Theory and Phenomenology
The discovery of neutrino masses has provided strong hints in favor of the
possibility that B-L symmetry is an intimate feature of physics beyond the
standard model. I discuss how important information about this symmetry as well
as other scenarios for TeV scale new physics can be obtained from the baryon
number violating process, neutron-anti-neutron oscillation. This article
presents an overview of different aspects of neutron-anti-neutron oscillation
and is divided into the following parts : (i) the phenomenon; (ii) the physics,
(iii) plausible models and (iv) applications to cosmology. In particular, it is
argued how the discovery of oscillation can significantly affect
our thinking about simple grand unified theory paradigms for physics beyond the
standard model, elucidate the nature of forces behind neutrino mass and provide
a new microphysical view of the origin of matter in the universe.Comment: 34 pages; 7 figures; Invited review for the issue on "Fundamental
Neutron Physics" by J. Phys.
Observing Nucleon Decay in Lead Perchlorate
Lead perchlorate, part of the OMNIS supernova neutrino detector, contains two
nuclei, 208Pb and 35Cl, that might be used to study nucleon decay. Both would
produce signatures that will make them especially useful for studying
less-well-studied neutron decay modes, e.g., those in which only neutrinos are
emitted.Comment: 6 pages, 2 figure
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., ), 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 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 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.
The OscSNS White Paper
There exists a need to address and resolve the growing evidence for
short-baseline neutrino oscillations and the possible existence of sterile
neutrinos. Such non-standard particles require a mass of eV/c, far
above the mass scale associated with active neutrinos, and were first invoked
to explain the LSND appearance signal.
More recently, the MiniBooNE experiment has reported a excess of
events in antineutrino mode consistent with neutrino oscillations and with the
LSND antineutrino appearance signal. MiniBooNE also observed a
excess of events in their neutrino mode data. Lower than expected
neutrino-induced event rates using calibrated radioactive sources and nuclear
reactors can also be explained by the existence of sterile neutrinos. Fits to
the world's neutrino and antineutrino data are consistent with sterile
neutrinos at this eV/c mass scale, although there is some tension
between measurements from disappearance and appearance experiments. In addition
to resolving this potential major extension of the Standard Model, the
existence of sterile neutrinos will impact design and planning for all future
neutrino experiments. It should be an extremely high priority to conclusively
establish if such unexpected light sterile neutrinos exist. The Spallation
Neutron Source (SNS) at Oak Ridge National Laboratory, built to usher in a new
era in neutron research, provides a unique opportunity for US science to
perform a definitive world-class search for sterile neutrinos.Comment: This white paper is submitted as part of the SNOWMASS planning
proces
Search for extraterrestrial antineutrino sources with the KamLAND detector
We present the results of a search for extraterrestrial electron
antineutrinos ('s) in the energy range using the KamLAND detector. In an exposure of
4.53 kton-year, we identify 25 candidate events. All of the candidate events
can be attributed to background, most importantly neutral current atmospheric
neutrino interactions, setting an upper limit on the probability of B
solar 's converting into 's at
(90% C.L.), if we assume an undistorted shape. This limit
corresponds to a solar flux of or an event
rate of above the energy threshold
. The present data also allows us to set more
stringent limits on the diffuse supernova neutrino flux and on the annihilation
rates for light dark matter particles.Comment: 22 pages, 6 figure
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