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H. V. Klapdor-Kleingrothaus

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

At least 91 records · Page 5Linked to original sources
arXiv1999

Stellar Weak Interaction Rates and Energy Losses for fp-Shell Nuclei Calculated in the Proton-Neutron Quasiparticle Random-Phase Approximation (II).(A = 61 to 80)

Weak interaction rates and the associated energy losses for massive nuclei in the fp-shell are calculated in stellar matter using a modified form of proton-neutron quasiparticle RPA model with separable Gamow-Teller forces. A total of 209 nuclei with mass numbers ranging from A = 61 to 80 are considered here for the calculation of weak rates. These also include many neutron-rich nuclei which play a key role in the dynamics of the core collapse calculations. The stellar weak rates are calculated over a wide range of densities (10 < ρY_{e} (gcm^{-3}) < 10^{11}) and temperatures (10^{7} < T(K) 30 x 10^{9}). This is our third paper in a series starting with the calculation of stellar weak rates for nuclei in the sd-shell. The calculated rates take into consideration the latest experimental energy levels and ft value compilations. The effect of particle emission processes is taken into account and the energies and probabilities of these particle emission processes are also calculated in stellar environment. Our results are presented here on an abbreviated scale of temperature and density.

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arXiv1999

Weak Interaction Rates Of sd-Shell Nuclei In Stellar Environment Calculated in the Proton-Neutron Quasiparticle Random Phase Approximation

Allowed weak interaction rates for sd-shell nuclei in stellar environment are calculated using a generalized form of proton-neutron quasiparticle RPA model with separable Gamow-Teller forces. Twelve different weak rates are calculated for each nucleus as a function of temperature and density. This project consists of calculation of weak rates for a total of 709 nuclei with masses ranging from A = 18 to 100. This paper contains calculated weak rates for sd-shell nuclei. The calculated capture and decay rates take into consideration the latest experimental energy levels and ft value compilations. The results are also compared with earlier works. Particle emission processes from excited states, previously ignored, are taken into account, and are found to significantly affect some beta decay rates.

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arXiv1999

Towards a superformula for neutrinoless double beta decay

A general Lorentz--invariant parameterization for the long-range part of the $0νββ$ decay rate is derived. Combined with the short range part this general parameterization in terms of effective $B-L$ violating couplings will allow it to extract the $0νββ$ limits on arbitrary lepton number violating theories. Several new nuclear matrix elements appear in the general formalism compared to the standard neutrino mass mechanism. Some of these new matrix elements have never been considered before and are calculated within pn-QRPA. Using these, limits on lepton number violating parameters are derived from experimental data on $^{76}$Ge.

hep-ph↗
arXiv1999

Improved bounds on SUSY accompanied neutrinoless double beta decay

Neutrinoless double beta decay induced by light Majorana neutrino exchange between two decaying nucleons with squark/slepton exchange inside one and W exchange inside the other nucleon (so-called vector-scalar exchange) gives stringent limits on R-parity violating interactions. We have extended previous work by including the tensor contribution to the transition rate. We discuss the improved limits on trilinear \Rp -MSSM couplings imposed by the current experimental limit on the $\znbb$ decay half-life of $^{76}$Ge.

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arXiv1999

Detection of low energy solar neutrinos with HPGermanium

The potential of the GENIUS proposal to measure the spectrum of low energy solar neutrinos in real time is studied. The detection reaction is elastic neutrino-electron scattering. The energy resolution for detecting the recoil electrons is about 0.3 %, the energy threshold is a few keV. The expected number of events for a target of one ton of natural germanium is 3.6 events/day for pp-neutrinos and 1.3 events/day for 7Be-neutrinos, calculated in the standard solar model (BP98). It should be feasible to achieve a background low enough to measure the low energy solar neutrino spectrum.

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arXiv1999

Limits on the Majorana neutrino mass in the 0.1 eV range

The Heidelberg-Moscow experiment gives the most stringent limit on the Majorana neutrino mass. After 24 kg yr of data with pulse shape measurements, we set a lower limit on the half-life of the neutrinoless double beta decay in 76Ge of T_1/2 > 5.7 * 10^{25} yr at 90% C.L., thus excluding an effective Majorana neutrino mass greater than 0.2 eV. This allows to set strong constraints on degenerate neutrino mass models.

hep-ex↗
arXiv1999

Microscopic Calculations of Weak Interaction Rates of Nuclei in Stellar Environment for A = 18 to 100

We report here the microscopic calculation of weak interaction rates in stellar matter for 709 nuclei with A = 18 to 100 using a generalized form of proton-neutron quasiparticle RPA model with separable Gamow-Teller forces. This is the first ever extensive microscopic calculation of weak rates calculated over a wide temperature-density grid which includes 10^7 \leq T(K) \leq 30 \times 10^9 and 10 \leq ρY_{e} (gcm^{-3}) \leq 10^{11}, and over a larger mass range. Particle emission processes from excited states, previously ignored, are taken into account, and are found to significantly affect some $β$ decay rates. The calculated capture and decay rates take into consideration the latest experimental energy levels and $ft$ value compilations. Our calculation of electron capture and $β$-decay rates, in the $fp$-shell, show considerable differences with a recently reported shell model diagonalization approach calculation.

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arXiv1999

High-purity germanium detector ionization pulse shapes of nuclear recoils, gamma interactions and microphonism

Nuclear recoil measurements with high-purity Germanium detectors are very promising to directly detect dark matter candidates. The main background sources in such experiments are natural radioactivity and microphonic noise. Digital pulse shape analysis is an encouraging approach to reduce the background originating from the latter. To study the pulse shapes of nuclear recoil events we performed a neutron scattering experiment, which covered the ionization energy range from 20 to 80 keV. We have measured ionization efficiencies as well and found an excellent agreement with the theory of Lindhard. In a further experiment we measured pulse shapes of a radioactive gamma-source and found no difference to nuclear recoil pulse shapes. Pulse shapes originating from microphonics of a HPGe-detector are presented for the first time. A microphonic noise suppression method, crucial for dark matter direct detection experiments, can therefore be calibrated with pulse shapes from gamma-sources.

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arXiv1999

Double Beta and Dark Matter Search - Window to New Physics beyond the Standard Model of Particle Physics

Nuclear double beta decay provides an extraordinarily broad potential to search for beyond Standard Model physics, probing already now the TeV scale, on which new physics should manifest itself. These possibilities are reviewed here. First, the results of present generation experiments are presented. The most sensitive one of them - the Heidelberg-Moscow experiment in the Gran Sasso - probes the electron mass now in the sub eV region and will reach a limit of $\sim$ 0.1 eV in a few years. Basing to a large extent on the theoretical work of the Heidelberg Double Beta Group in the last two years, results are obtained also for SUSY models (R-parity breaking, sneutrino mass), leptoquarks (leptoquark-Higgs coupling), compositeness, right-handed W boson mass, test of special relativity and equivalence principle in the neutrino sector and others. One of the enriched $^{76}$Ge detectors also yields the most stringent limits for cold dark matter (WIMPs) to date by using raw data. A new Heidelberg experimental proposal (GENIUS) is described which would allow to increase the sensitivity for Majorana neutrino masses from the present level of at best 0.1 eV down to 0.01 or even 0.001 eV. It would further, already in a first step using only 100 kg of natural Ge detectors, cover almost the full MSSM parameter space for prediction of neutralinos as cold dark matter.

hep-ex↗
arXiv1998

The GENIUS Project - Background and technical studies

The potential of GENIUS as a dark matter detector is discussed. A study was performed to demonstrate the good behaviour of the proposed detector design of naked HPGe-crystals in liquid nitrogen. The expected background components were simulated and are discussed in some detail.With the obtained background GENIUS could cover a large part of the favoured MSSM parameter-space.

hep-ex↗
arXiv1998

About direct Dark Matter detection in Next-to-Minimal Supersymmetric Standard Model

Direct dark matter detection is considered in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). The effective neutralino-quark Lagrangian is obtained and event rates are calculated for the Ge-73 isotope. Accelerator and cosmological constraints on the NMSSM parameter space are included. By means of scanning the parameter space at the Fermi scale we show that the lightest neutralino could be detected in dark matter experiments with sizable event rate.

hep-ph↗
arXiv1998

Next-to-Minimal Supersymmetric Standard Model and direct Dark Matter detection

Prospects for direct dark matter detection are considered in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). The effective neutralino-quark Lagrangian is obtained and event rates are calculated for Ge-73. Accelerator and cosmological constraints on the NMSSM are included in our numerical analysis, which allows us to conclude that the lightest neutralino from NMSSM could be detected in future dark matter experiments.

hep-ph↗
arXiv1998

New physics potential of double beta decay and dark matter search

The search for neutrinoless double beta decay and WIMP dark matter has a broad potential to test particle physics beyond the standard model. During the last years, the analysis of various contributions to the double beta decay rate by the Heidelberg group led, besides the most restrictive limit on the effective Majorana neutrino mass, to bounds on left-right-symmetric models, leptoquarks and supersymmetry. In a general framework bounds on arbitrary lepton number violating theories can be derived. Using double beta technology for direct dark matter detection, stringent limits on the spin-independent WIMP--nucleon interaction have been obtained. These results deduced from the Heidelberg-Moscow double beta decay experiment are reviewed. Also an outlook on the future of double beta decay and dark matter search, the GENIUS proposal, is given.

hep-ph↗
arXiv1998

Double Beta Decay and Dark Matter Search - Window to New Physics now, and in future (GENIUS)

Nuclear double beta decay provides an extraordinarily broad potential to search for beyond Standard Model physics, probing already now the TeV scale, on which new physics should manifest itself. These possibilities are reviewed here. First, the results of present generation experiments are presented. The most sensitive one of them -- the Heidelberg-Moscow experiment in the Gran Sasso -- probes the electron mass now in the sub eV region and will reach a limit of $\sim$ 0.1 eV in a few years. Basing to a large extent on the theoretical work of the Heidelberg Double Beta Group in the last two years, results are obtained also for SUSY models (R-parity breaking, sneutrino mass), leptoquarks (leptoquark-Higgs coupling), compositeness, right-handed W boson mass and others. These results are comfortably competitive to corresponding results from high-energy accelerators like TEVATRON, HERA, etc. Second, future perspectives of $ββ$ research are discussed. A new Heidelberg experimental proposal (GENIUS) is presented which would allow to increase the sensitivity for Majorana neutrino masses from the present level of at best 0.1 eV down to 0.01 or even 0.001 eV. Its physical potential would be a breakthrough into the multi-TeV range for many beyond standard models. Its sensitivity for neutrino oscillation parameters would be larger than of all present terrestrial neutrino oscillation experiments and of those planned for the future. It could probe directly the atmospheric neutrino problem and even the large angle solution of the solar neutrino problem. It would further, already in a first step, cover almost the full MSSM parameter space for prediction of neutralinos as cold dark matter, making the experiment competitive to LHC in the search for supersymmetry.

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arXiv1998

A Large Scale Double Beta and Dark Matter Experiment: GENIUS

The recent results from the HEIDELBERG-MOSCOW experiment have demonstrated the large potential of double beta decay to search for new physics beyond the Standard Model. To increase by a major step the present sensitivity for double beta decay and dark matter search much bigger source strengths and much lower backgrounds are needed than used in experiments under operation at present or under construction. We present here a study of a project proposed recently, which would operate one ton of 'naked' enriched GErmanium-detectors in liquid NItrogen as shielding in an Underground Setup (GENIUS). It improves the sensitivity to neutrino masses to 0.01 eV. A ten ton version would probe neutrino masses even down to 10^-3 eV. The first version would allow to test the atmospheric neutrino problem, the second at least part of the solar neutrino problem. Both versions would allow in addition significant contributions to testing several classes of GUT models. These are especially tests of R-parity breaking supersymmetry models, leptoquark masses and mechanism and right-handed W-boson masses comparable to LHC. The second issue of the experiment is the search for dark matter in the universe. The entire MSSM parameter space for prediction of neutralinos as dark matter particles could be covered already in a first step of the full experiment - with the same purity requirements but using only 100 kg of 76Ge or even of natural Ge - making the experiment competitive to LHC in the search for supersymmetry. The layout of the proposed experiment is discussed and the shielding and purity requirements are studied using GEANT Monte Carlo simulations. As a demonstration of the feasibility of the experiment first results of operating a 'naked' Ge detector in liquid nitrogen are presented.

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arXiv1997

A general parametrization for the long-range part of neutrinoless double beta decay

Double beta decay has been proven to be a powerful tool to constrain $B-L$ violating physics beyond the standard model. We present a representation for the long-range part of the general $0νββ$ decay rate allowed by Lorentz-invariance. Combined with the short range part this general parametrization in terms of effective $B-L$ violating couplings will provide the $0νββ$ limits on arbitrary lepton number violating theories.

hep-ph↗
arXiv1997

A Xenon Solar Neutrino Detector

The neutrino capture by $^{131}$Xe with a threshold at 352 keV as reaction to detect solar neutrinos is examined. The most important feature of this process is its high sensitivity to beryllium neutrinos, which contribute approximately 40% to the total capture rate (45 SNU) assuming the fluxes predicted by the Standard Solar Model.

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