443 research outputs found
Hadronic structure aspects of decays
As is known from previous studies the lepton number violating decays have good prospects to probe new physics beyond the
Standard Model and provide valuable information on neutrino masses and mixing.
We analyze these processes with an emphasis on their hadronic structure
aspects applying relativistic constituent quark model. We conclude that the
previously ignored contribution associated with the t-channel Majorana neutrino
exchange is comparable with the s-channel one in a wide range of neutrino
masses. We also estimated model independent absolute upper bounds on neutrino
contribution to these decays.Comment: 15 pages, 1 figure. Version to appear in PRD, normalization factor in
Eq. (25) is correcte
On sterile neutrino mixing with \nu_{\tau}
Matrix element of sterile neutrino N mixing with is
the least constrained in the literature among the three
() mixing parameters characterizing the sterile neutrino
phenomenology. We study the contribution of massive dominantly sterile
neutrinos to purely leptonic -decays and semileptonic decays of
and K, D mesons. We consider some decays allowed in the Standard Model (SM) as
well as Lepton Flavor and Lepton Number Violating (LFV, LNV) decays forbidden
in the SM. From the existing experimental data on the branching ratios of these
processes we derived new limits on more stringent than the ones
existing in the literature. These limits are extracted in a model independent
way without any ad hoc assumptions on the relative size of the three different
sterile neutrino mixing parameters.Comment: 14 pages, 6 figures. arXiv admin note: text overlap with
arXiv:1005.160
The neutron electric dipole form factor in the perturbative chiral quark model
We calculate the electric dipole form factor of the neutron in a perturbative
chiral quark model, parameterizing CP-violation of generic origin by means of
effective electric dipole moments of the constituent quarks and their
CP-violating couplings to the chiral fields. We discuss the relation of these
effective parameters to more fundamental ones such as the intrinsic electric
and chromoelectric dipole moments of quarks and the Weinberg parameter. From
the existing experimental upper limits on the neutron EDM we derive constraints
on these CP-violating parameters.Comment: 20 pages, 3 figure
Large family with both parents affected by distinct BRCA1 mutations: implications for genetic testing
Although the probability of both parents being affected by BRCA1 mutations is not negligible, such families have not been systematically described in the literature. Here we present a large breast-ovarian cancer family, where 3 sisters and 1 half-sister inherited maternal BRCA1 5382insC mutation while the remaining 2 sisters carried paternal BRCA1 1629delC allele. No BRCA1 homozygous mutations has been detected, that is consistent with the data on lethality of BRCA1 knockout mice. This report exemplifies that the identification of a single cancer-predisposing mutation within the index patient may not be sufficient in some circumstances. Ideally, all family members affected by breast or ovarian tumor disease have to be subjected to the DNA testing, and failure to detect the mutation in any of them calls for the search of the second cancer-associated allele
The (muon^-,muon^+) conversion in nuclei as a probe of new physics
A detailed study of the muonic analogue of neutrinoless double beta decay,
(muon^-,muon^+) conversion, has been carried out for the A=44 nuclear system.
We studied several lepton number violating (LNV) mechanisms potentially
triggering this process: exchange by light and heavy Majorana neutrinos as well
as exchange by supersymmetric particles participating in R-parity violating
interactions. The nuclear structure has been taken into account within the
renormalized Quasiparticle Random Phase Approximation method. To our knowledge,
this is the first realistic treatment of nuclear structure aspects of the
(muon^-,muon^+) conversion. We estimated the rate of this process utilizing the
existing experimental constraints on the parameters of the underlying LNV
interactions and conclude that the (muon^-,muon^+) conversion is hardly
detectable in the near future experiments.Comment: 23 pages, RevTex, 3 Postscript figure
Erratum to: "Double volume reflection of a proton beam by a sequence of two bent crystals" [Phys. Lett. B 658 (2008) 109]
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Bilinear R-parity Violation in Neutrinoless Double Beta Decay
We discuss some phenomenological issues of the effective quark-lepton
operators emerging from the bilinear lepton-Higgs couplings in the
superpotential and in the soft supersymmetry (SUSY) breaking sector of the
supersymmetric models without R-parity. The contribution of these operators to
the neutrinoless double beta decay is derived. The corresponding nuclear matrix
elements are calculated within the renormalized quasiparticle random phase
approximation, which includes the Pauli effect of fermion pairs and does not
collapse for the physical values of the nuclear force strength. On this basis
we extract from the experimental data new stringent limits on the 1st
generation mass parameter characterized the lepton-Higgs bilinear coupling and
on the electron sneutrino vacuum expectation value.Comment: 26 pages, Latex, 1 Postscript figur
Pions in Nuclei and Manifestations of Supersymmetry in Neutrinoless Double Beta Decay
We examine the pion realization of the short ranged supersymmetric (SUSY)
mechanism of neutrinoless double beta decay. It originates from the R-parity
violating quark-lepton interactions of the SUSY extensions of the standard
model of the electroweak interactions. We argue that pions are dominant SUSY
mediators in neutrinoless double beta decay. The corresponding nuclear matrix
elements for various isotopes are calculated within the proton-neutron
renormalized quasiparticle random phase approximation. We define those isotopes
which are most sensitive to the SUSY signal and outlook the present
experimental situation with the double beta decay searches for the SUSY. Upper
limits on the R-parity violating 1st generation Yukawa coupling are derived
from various double beta decay experiments.Comment: 15 pages, Latex, 3 Postscript figure
Observation of parametric X-rays produced by 400 GeV/c protons in bent crystals
Spectral maxima of parametric X-ray radiation (PXR) produced by 400 GeV/c protons in bent silicon crystals aligned with the beam have been observed in an experiment at the H8 external beam of the CERN SPS. The total yield of PXR photons was about 10-6 per proton. Agreement between calculations and the experimental data shows that the PXR kinematic theory is valid for bent crystals with sufficiently small curvature as used in the experiment. The intensity of PXR emitted from halo protons in a bent crystal used as a primary collimator in a circular accelerator may be considered as a possible tool to control its crystal structure, which is slowly damaged because of irradiation. The intensity distribution of PXR peaks depends on the crystal thickness intersected by the beam, which changes for different orientations of a crystal collimator. This dependence may be used to control crystal collimator alignment by analyzing PXR spectra produced by halo protons.peer-reviewe
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