arXiv subjects

H. V. Klapdor-Kleingrothaus

Publications and source records attributed to H. V. Klapdor-Kleingrothaus.

104 records · Page 6Linked to original sources

arXiv1997

R-parity Conserving Supersymmetry, Neutrino Mass and Neutrinoless Double Beta Decay

We consider contributions of R-parity conserving softly broken supersymmetry (SUSY) to neutrinoless double beta ($\znbb$) decay via the (B-L)-violating sneutrino mass term. The latter is a generic ingredient of any weak-scale SUSY model with a Majorana neutrino mass. The new R-parity conserving SUSY contributions to $\znbb$ are realized at the level of box diagrams. We derive the effective Lagrangian describing the SUSY-box mechanism of $\znbb$-decay and the corresponding nuclear matrix elements. The 1-loop sneutrino contribution to the Majorana neutrino mass is also derived. Given the data on the $\znbb$-decay half-life of $^{76}$Ge and the neutrino mass we obtain constraints on the (B-L)-violating sneutrino mass. These constraints leave room for accelerator searches for certain manifestations of the 2nd and 3rd generation (B-L)-violating sneutrino mass term, but are most probably too tight for first generation (B-L)-violating sneutrino masses to be searched for directly.

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arXiv1997

B-L-violation in Softly Broken Supersymmetry and Neutrinoless Double Beta Decay

We prove a low-energy theorem valid for any model of weak scale softly broken supersymmetry. It claims that the neutrino Majorana mass, the B-L violating mass of the sneutrino and the neutrinoless double beta decay amplitude are intimately related to each other such that if one of them is non-zero the other two are also non-zero and, vice versa, if one of them vanishes the other two vanish as well. The theorem is a consequence of the underlying supersymmetry and independent of the mechanisms of neutrinoless double beta decay and (s-)neutrino mass generation.

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arXiv1997

B-L-violating Masses in Softly Broken Supersymmetry

We prove a general low-energy theorem establishing a generic relation between the neutrino Majorana mass and the superpartner sneutrino B-L-violating "Majorana"-like mass term. The theorem states that, if one of these two quantities is non-zero the other one is also non-zero and, vice versa, if one of them vanishes the other vanishes, too. The theorem is a consequence of the underlying supersymmetry (SUSY) and valid for any realistic gauge model with weak scale softly broken SUSY.

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arXiv1996

Superlight neutralino as a dark matter particle candidate

We address the question of how light can be the lightest supersymmetric particle neutralino to be a reliable cold dark matter (CDM) particle candidate. To this end we have performed a combined analysis of the parameter space of the Minimal Supersymmetric Standard Model (MSSM) taking into account cosmological and accelerator constraints including those from the radiative $b\rightarrow sγ$ decay. Appropriate grand unification (GUT) scenarios were considered. We have found that the relaxation of gaugino mass unification is sufficient to obtain a phenomenologically and cosmologically viable solution of the MSSM with the neutralino as light as 3~GeV. We have found good prospects for direct detection of these superlight CDM neutralinos via elastic scattering off various nuclei in the forthcoming experiments with low-threshold DM detectors. In a certain sense, these experiments can probe the gaugino mass unification giving constraints on the possible GUT scenarios within the MSSM.

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arXiv1996

Is SUSY accessible by direct dark matter detection?

We performed a combined analysis of the parameter space of the Minimal Supersymmetric Standard Model (MSSM) taking into account cosmological and accelerator constraints including those from the radiative $b\rightarrow sγ$ decay measured by the CLEO collaboration. Special attention is paid to the event rate, $R$, of direct dark matter neutralino detection. We have found domains of the parameter space with $R\simeq 5-10$~events/kg/day. This would be within the reach of current dark matter experiments. The $b\rightarrow sγ$ data do not essentially reduce these large event rate domains of the MSSM parameter space.

hep-ph↗

arXiv1996

New Leptoquark Mechanism of Neutrinoless Double Beta Decay

A new mechanism for neutrinoless double beta ($\znbb$) decay based on leptoquark exchange is discussed. Due to the specific helicity structure of the effective four-fermion interaction this contribution is strongly enhanced compared to the well-known mass mechanism of $\znbb$ decay. As a result the corresponding leptoquark parameters are severely constrained from non-observation of $\znbb$-decay. These constraints are more stringent than those derived from other experiments.

hep-ph↗

arXiv1996

Double beta decay in left-right symmetric models

Left-right symmetric models provide a natural framework for neutrinoless double beta ($\znbb$) decay. In the analysis of $\znbb$ decay in left-right symmetric models, however, it is usually assumed that all neutrinos are light. On the other hand, heavy {\it right-handed} neutrinos appear quite naturally in left-right symmetric models and should therefore not be neglected. Assuming the existence of at least one right-handed heavy neutrino, absence of $\znbb$ decay of $^{76}$Ge currently provides the following limits on the mass and mixing angle of right-handed W-bosons: $m_{W_R}\ge 1.1 $ TeV and $\tan(ζ) \le 4.7 \times 10^{-3}$ for a particular value of the effective right-handed neutrino mass, $\emnv = 1$ TeV, and in the limit of infinitly massive doubly charged Higgs ($Δ^{--}$). The effects of the inclusion of the Higgs triplet on $\znbb$ decay are also discussed.

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arXiv1996

New Low-energy Leptoquark Interactions

We discuss an extension of the standard model (SM) with vector and scalar leptoquarks. The renormalizable leptoquark Lagrangian consistent with the SM gauge symmetry is presented including the leptoquark-Higgs interactions previously not considered in the literature. We discuss the importance of these new interactions for leptoquark phenomenology. After the electro-weak symmetry breaking they generate non-trivial leptoquark mass matrices. These lead to mixing between different $SU(2)_L$-multiplets of the leptoquarks and induce at low energies new effective 4-fermion lepton-quark vertices. The latter affect the standard leptoquark phenomenology. We discuss constraints on these interactions from the helicity-suppressed $π\rightarrow ν+ e$ decay.

hep-ph↗

arXiv1995

On the SUSY Accompanied Neutrino Exchange Mechanism of Neutrinoless Double Beta Decay

The neutrinoless double beta decay ($\znbb$) induced by light Majorana neutrino exchange between decaying nucleons, accompanied by the squark exchange inside one nucleon, recently discussed by Babu and Mohapatra, is carefully analyzed both from the particle and nuclear physics sides. New nuclear matrix elements relevant to this mechanism are calculated. We extend the analysis to include mixing of light neutrinos with heavy and "sterile" neutrinos. It introduces another supersymmetric (SUSY) contribution to $\znbb$. We discuss constraints on the \rp MSSM parameters imposed by the current experimental limit on $\znbb$ decay half-life of $^{76}$Ge.

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arXiv1995

Expectations for Supersymmetric Dark Matter Searches Underground

We consider the neutralino as a dominant Dark Matter particle in the galactic halo and investigate some general issues of direct Dark Matter searches via elastic neutralino-nucleus scattering. On the basis of conventional assumptions about the nuclear and nucleon structure we analyse constraints on SUSY model parameter space accessible by the direct Dark Matter searches. This analysis shows that Dark Matter detectors fall into the THREE different categories with respect to their sensitivity to different groups of the SUSY model parameters. We calculate the event rate for various experimentally interesting isotopes within the Minimal Supersymmetric Standard Model (MSSM) taking into account the known accelerator and cosmological constraints on the MSSM parameter space. We investigate the role of nuclear spin in elastic neutralino - nucleus scattering. It is found that the contribution of the spin-dependent interaction to this process is subdominant for nuclei with atomic weights A > 50.

hep-ph↗

arXiv1995

Supersymmetry and Neutrinoless Double Beta Decay

Neutrinoless double beta decay ($\znbb$) induced by superparticle exchange is investigated. Such a supersymmetric (SUSY) mechanism of $\znbb$ decay arises within SUSY theories with R-parity non-conservation (\rp). We consider the minimal supersymmetric standard model (MSSM) with explicit \rp terms in the superpotential (\rp MSSM). The decay rate for the SUSY mechanism of $\znbb$ decay is calculated. Numerical values for nuclear matrix elements for the experimentally most interesting isotopes are calculated within pn-QRPA. Constraints on the \rp MSSM parameter space are extracted from current experimental half-life limits. The most stringent limits are derived from data on $^{76}$Ge. It is shown that these constraints are more stringent than those from other low-energy processes and are competitive to or even more stringent than constraints expected from accelerator searches.

hep-ph↗

arXiv1995

New Supersymmetric Contributions to Neutrinoless Double Beta Decay.

The neutrinoless double beta ($\znbb$) decay is analyzed within the Minimal Supersymmetric Standard Model with explicit R-parity violation (\rp MSSM). We have found new supersymmetric contributions to this process and give the complete set of relevant Feynman diagrams. Operators describing $0^+ \longrightarrow 0^+$ nuclear transitions induced by the supersymmetric interactions of the \rp MSSM are derived. These operators can be used for calculating the $\znbb$ decay rate applying any specific nuclear model wave functions.

hep-ph↗

arXiv1994

Possible constraints on SUSY-model Parameters from Direct Dark Matter Search

We consider the SUSY-model neutralino as a dominant Dark Matter particle in the galactic halo and investigate some general issues of direct DM searches via elastic neutralino-nucleus scattering. On the basis of conventional assumptions about the nuclear and nucleon structure, without referring to a specific SUSY-model, we prove that it is impossible in principle to extract more than three constraints on fundamental SUSY-model parameters from the direct Dark matter searches. Three types of Dark matter detectors probing different groups of parameters are recognized.

hep-ph↗

arXiv1994

On SUSY Dark Matter Detection with Spinless Nuclei

We investigate the role of nuclear spin in elastic scattering of Dark Matter (DM) neutralinos from nuclei in the framework of the Minimal SUSY standard model (MSSM). The relative contribution of spin-dependent axial-vector and spin-independent scalar interactions to the event rate in a DM detector has been analyzed for various nuclei. Within general assumptions about the nuclear and nucleon structure we find that for nuclei with atomic weights $A > 50$ the spin-independent part of the event rate $R_{si}$ is larger than the spin-dependent one $R_{sd}$ in the domain of the MSSM parameter space allowed by the known experimental data and where the additional constraint for the total event rate $R =R_{sd} + R_{si} > 0.01$ is satisfied. The latter reflects realistic sensitivities of present and near future DM detectors. Therefore we expect equal chances for discovering the DM event either with spin-zero or with spin-non-zero isotopes if their atomic weights are $A_{1} \sim A_{2} > 50$.

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