Heavy sterile neutrino in dark matter searches

Sterile neutrinos are possible dark matter candidates. We examine here possible detection mechanisms, assuming that the neutrino has a mass of about 50 keV and couples to the ordinary neutrino. Even though this neutrino is quite heavy, it is non relativistic with a maximum kinetic energy of 0.1 eV. Thus new experimental techniques are required for its detection. We estimate the expected event rate in the following cases: i) Measure electron recoils in the case of materials with very low electron binding. ii) Low temperature crystal bolometers. iii) Spin induced atomic excitations at very low temperatures, leading to a characteristic photon spectrum. iv) Observation of resonances in antineutrino absorption by a nucleus undergoing electron capture. v) Neutrino induced electron events beyond the end point energy of beta decaying systems, e.g. in the tritium decay studied by KATRIN.Comment: 17 pages, 8 figures ; revised figures, corrected typos, additional comments ; results unchange

Modulation, asymmetry and the diurnal variation in axionic dark matter searches

In the present work we study possible time dependent effects in Axion Dark Matter searches employing resonant cavities. We find that the width of the resonance, which depends on the axion mean square velocity in the local frame, will show an annual variation due to the motion of the Earth around the sun (modulation). Furthermore, if the experiments become directional, employing suitable resonant cavities, one expects large asymmetries in the observed widths relative to the sun’s direction of motion. Due to the rotation of the Earth around its axis, these asymmetries will manifest themselves as a diurnal variation in the observed width. ©2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license1111sciescopu

Few active mechanisms of the neutrinoless double beta-decay and effective mass of Majorana neutrinos

It is well known that there exist many mechanisms that may contribute to neutrinoless double beta decay (0nbb-decay). By exploiting the fact that the associated nuclear matrix elements are target dependent we show that, given definite experimental results on a sufficient number of targets, one can determine or sufficiently constrain all lepton violating parameters including the mass term. As a specific example we show that, assuming the observation of the 0nbb-decay in three different nuclei, e.g., 76Ge, 100Mo and 130Te, and just three lepton number violating mechanisms (light and heavy neutrino mass mechanisms as well as R-parity breaking SUSY mechanism) being active, there are only four different solutions for the lepton violating parameters, provided that they are relatively real. In particular, assuming evidence of the 0nbb-decay of 76Ge, the effective neutrino Majorana mass |m_bb| can be almost uniquely extracted by utilizing other existing constraints (cosmological observations and tritium beta-decay experiments). We also point out the possibility that the non-observation of the 0nbb-decay for some isotopes could be in agreement with a value of |m_bb| in sub eV region. We thus suggest that it is important to have at least two different 0nbb-decay experiments for a given nucleus.Comment: 5 pages, 2 figure

Hierarchies of R-violating interactions from Family Symmetries

We investigate the possibility of constructing models of R-violating LQD Yukawa couplings using a single U(1) flavour-symmetry group and supermultiplet charge assignments that are compatible with the known hierarchies of quark and lepton masses. The mismatch of mass and current eigenstates inferred from the known charged-current mixing induces the propagation of strong phenomenological constraints on some R-violating couplings to many others. Applying these constraints, we look for flavour-symmetry models that are consistent with different squark-production hypotheses devised to explain the possible HERA large-Q^2 anomaly. The e^+ d -> stop interpretation of the HERA data is accommodated relatively easily, at the price of postulating an extra parity. The e^+ s -> stop interpretation of the events requires models to have only small (2,3) mixing in the down quark sector. The e^+ d -> scharm mechanism cannot be accommodated without large violations of squark-mass universality, due to the very strong experimental constraints on R-violating operators. We display a model in which baryon decay due to dangerous dimension-five operators is automatically suppressed.Comment: 21 pages, Latex file, no figure

SU(3) techniques for shell model studies and the spectra of A = 25 nuclei : techncial report

http://deepblue.lib.umich.edu/bitstream/2027.42/8088/5/bad4500.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/8088/4/bad4500.0001.001.tx

SU(3) [superset or implies] R(3) Wigner coefficients in the 2s-1d shell

Explicit algebraic expressions are given for SU(3) [superset or implies] R(3) Wigner coefficients, which are of particular interest in p-shell and 2s-1d shell-model calculations. An orthogonal basis tied closely to Elliott's basis is chosen according to a systematic recipe. The Wigner coefficients are those involving the Kronecker products ([lambda]1[mu]1) x ([lambda]2[mu]3) --> ([lambda]3[mu]3) in the following cases:(i) ([lambda]2[mu]2) = (10), (01) and [mu]i [less, double equals] 4 (arbitrary [lambda]i), i = 1, 3. (For the case [mu]i = 4, only auxiliary coefficients are tabulated whenever the angular momentum multiplicity is 3. From these the final Wigner coefficients can be calculated for any specific case of interest.)(ii) ([lambda]2[mu]2) = (20), (02) and [mu]i [less, double equals] 3 (arbitrary [lambda]i), or [lambda]i [less, double equals] 3 (arbitrary [mu]i) i = 1, 3.(iii) ([lambda]2[mu]2) = (11) and [mu]i [less, double equals] 3 (arbitrary [lambda]i), or [lambda]i [less, double equals] 3 (arbitrary [mu]i) i = 1, 3 except for ([lambda]3) x (11) --> ([lambda]3) which is not given.A method is also given whereby coefficients with more complicated ([lambda]2[mu]2) can be calculated from coefficients of type (i) by a build-up process. Some symmetry properties are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33198/1/0000586.pd

Su(3) Techniques For Shell Model Studies And The Spectra Of A = 25 Nuclei.

PhDNuclear physicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/187896/2/6912266.pd

Neutrinoless double beta decay and neutrino mass

The observation of neutrinoless double beta decay (DBD) will have important consequences. First it will signal that lepton number is not conserved and the neutrinos are Majorana particles. Second, it represents our best hope for determining the absolute neutrino mass scale at the level of a few tens of meV. To achieve the last goal, however, certain hurdles have to be overcome involving particle, nuclear and experimental physics. Particle physics is important since it provides the mechanisms for neutrinoless DBD. In this review, we emphasize the light neutrino mass mechanism. Nuclear physics is important for extracting the useful information from the data. One must accurately evaluate the relevant nuclear matrix elements (NMEs), a formidable task. To this end, we review the recently developed sophisticated nuclear structure approaches, employing different methods and techniques of calculation. We also examine the question of quenching of the axial vector coupling constant, which may have important consequences on the size of the NMEs. From an experimental point of view it is challenging, since the life times are extremely long and one has to fight against formidable backgrounds. One needs large isotopically enriched sources and detectors with good energy resolution and very low background. (c) World Scientific Publishing Company143521sciescopu