arXiv subjects

S. T. Belyaev

Publications and source records attributed to S. T. Belyaev.

23 records · Page 2Linked to original sources

arXiv2001

Latest Results from the Heidelberg-Moscow Double Beta Decay Experiment

New results for the double beta decay of 76Ge are presented. They are extracted from Data obtained with the HEIDELBERG-MOSCOW, which operates five enriched 76Ge detectors in an extreme low-level environment in the GRAN SASSO. The two neutrino accompanied double beta decay is evaluated for the first time for all five detectors with a statistical significance of 47.7 kg y resulting in a half life of (T_(1/2))^(2nu) = [1.55 +- 0.01 (stat) (+0.19) (-0.15) (syst)] x 10^(21) years. The lower limit on the half-life of the 0nu beta-beta decay obtained with pulse shape analysis is (T_(1/2))^(0_nu) > 1.9 x 10^(25) [3.1 x 10^(25)] years with 90% C.L. (68% C.L.) (with 35.5 kg y). This results in an upper limit of the effective Majorana neutrino mass of 0.35 eV (0.27 eV). No evidence for a Majoron emitting decay mode or for the neutrinoless mode is observed.

hep-ph↗

arXiv1999

Multiple Scattering Theory for Slow Neutrons (from thermal to ultracold)

The general theory of neutron scattering is presented, valid for the whole domain of slow neutrons from thermal to ultracold. Particular attention is given to multiple scattering which is the dominant process for ultracold neutrons (UCN). For thermal and cold neutrons, when the multiple scattering in the target can be neglected, the cross section is reduced to the known value. A new expression for inelastic scattering cross section for UCN is proposed. Dynamical processes in the target are taken into account and their influence on inelastic scattering of UCN is analyzed.

nucl-th↗

arXiv1999

Interaction of Ultra-Cold Neutrons with Condensed Matter

General theory of neutron scattering (elastic and inelastic) is presented. It is applicable for the whole domain of slow neutrons and includes as limiting cases existing theories for thermal and cold neutrons and for elastic scattering of UCN. New expression for inelastic scattering cross section for UCN is proposed. It differs from the usually used by proper account of re-scattering processes. Evidence for small heating and cooling of UCN is given.

nucl-th↗

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↗

arXiv1998

New limits on dark--matter WIMPs from the Heidelberg--Moscow experiment

New results after 0.69 kg yr of measurement with an enriched 76Ge detector of the Heidelberg--Moscow experiment with an active mass of 2.758 kg are presented. An energy threshold of 9 keV and a background level of 0.042 counts/(kg d keV) in the energy region between 15 keV and 40 keV was reached.The derived limits on the WIMP--nucleon cross section are the most stringent limits on spin--independent interactions obtained to date by using essentially raw data without background subtraction.

hep-ex↗