Teilchenphysik ohne Beschleuniger (Non Accelerator Particle Physics)

Experimental and theoretical research in the areas of
Double Beta Decay, Dark Matter Searches and Physics beyond the Standard Model



Nr. 1 - 6.4 SIGMA RESULT !!
Nr. 3 - Theoretical Investigation ...
Nr. 4 - Microscopic Calculations ...

Nr. 1: Please click here to print the pdf file of
our NEW Article
- Modern Physics Letters A Vol. 21 (2006) 1547-1566:

H.V. Klapdor-Kleingrothaus and I.V. Krivosheina,

"The Evidence for the Observation of 0nu beta-beta decay:
the Identification of 0nu beta-beta Events
from the Full Spectra"

NN, det-s 2,3,4,5, from 1995 to 2003. 6.4 sigma (7.05 +- 1.11 events).
"The pulse shape selected spectrum (selected by neuronal net-NN) with detectors 2,3,4,5, from 1995 to 2003 in the energy interval 2000-2100 keV. The signal at Qbeta-beta has a confidence level of 6.4 sigma (7.05 +- 1.11 events)."
NN- 0 mm, det-s 2,3,4,5, from 1995 to 2003. 6.6 sigma. NN- 1 mm, det-s 2,3,4,5, from 1995 to 2003. 7.2 sigma. NN- 2 mm, det-s 2,3,4,5, from 1995 to 2003. 6.7 sigma.
"The pulse shape selected spectrum (selected by neuronal net-NN) with detectors 2,3,4,5, from 1995 to 2003 in the energy interval 2000-2060 keV. The signal at Qbeta-beta has a confidence level of 6.6, 7.2 and 6.7 sigma respectively for cutting boundary areas of 0(1)(2) mm are shown."
NN- 2505 kev Gam L., det-s 2,3,4,5, from 1995 to 2003. MSE- 2505 kev Gam L., det-s 2,3,4,5, from 1995 to 2003. NN- 2105 kev Gam L., det-s 2,3,4,5, from 1995 to 2003.
"Lines from the neuronal net (NN) pulse shape selected spectrum measured 1995-2003 for detectors 2,3,4,5, in the energy of some strong background lines. E.g. 2505.7 keV line originating from summation of the subsequent 1173.2 and 1332.5 keV gamma-lines from 60Co naturally expected to be a multiple site event is erased to 100% (please compare with pulse shape selected MSE spectrum, second figure (rosa))."

Nr. 2: Please click here to print the pdf file
of our LESSONS
Physics Scripta T 127 (2007) 40-42:

H.V. Klapdor-Kleingrothaus

"Lessons After the Evidence for 0 nu Beta-Beta Decay"

-------- Abstract --------
This paper describes the lessons we have to draw
after the observation of neutrinoless beta-beta decay
by the enriched 76Ge experiment,
for present and future experiments
(a) to fulfill the task to confirm the present result
(b) to deliver additional information on the main contributions,
of effective neutrino mass and right-handed weak currents etc.
to the 0nu beta-beta amplitude.
It is pointed out that
presently running and planned experiments are probably
not sensitive enough to check the present evidence on a reasonable time scale.

More important,
the only way to get more information on the individual contributions
of m, eta, lambda etc. to the 0nu beta-beta amplitude
is to go to completely different types of experiments,
e.g. mixed-mode beta^+ EC decay experiments, such as 124Xe decay.

-------- Abstract --------

Nr. 3 : Here You will find another article -
pdf file of the new article
Phys. Rev D 73 (2006) 013010
H.V. Klapdor-Kleingrothaus, I.V. Krivosheina and I.V. Titkova

"Theoretical Investigation of the Dependence of Double Beta Decay
Tracks in a Ge Detector on Particle and Nuclear Physics
Parameters and Separation from Gamma Ray Events"

-------- Abstract --------

The key to probe the existence of 0nu beta-beta decay beyond observation of a signal at the Q value of the process, Qbeta-beta, is the discrimination of beta-beta events from background gamma events (or other events), in almost any double beta decay experiment (see Phys. Lett. B 586 (2004) 198 and NIMA 522 (2004) 371). In this paper Monte Carlo simulations of neutrino-accompanied (2nu beta-beta) and neutrinoless double beta decay (0nu beta-beta) events, and of various kinds of background processes such as multiple and other gamma interactions are reported for a Ge detector. The time history of the evolution of the individual events is followed and the sizes of the events (volumes in the detector inside which the energy of the event is released) are investigated. Effects of the angular correlations of the two electrons in beta-beta decay, which again depend on nuclear and (for 0nu beta-beta decay) on particle physics parameters, are taken into account and have been calculated for this purporse for the first time on basis of the experimental half-life of 76Ge and of realistic nuclear matrix elements. The sizes determine, together with the location of the events, in the detector, the pulse shapes to be observed. It is shown for beta-beta decay of 76Ge, that beta-beta events are separable from Compton scattering of gamma events of the same energy, while double escape peaks of gamma-lines show very similar behaviour as 0nu beta-beta events, and in that sense can be useful for corresponding 'calibration' of pulse shapes of the detector.

Nr. 4: Another NEW article (pdf file)
Phys. Lett. B 636 (2006) 235-247
H.V. Klapdor-Kleingrothaus, I.V. Krivosheina, V. Mironov and I.V. Titkova

"Microscopic Calculations of Signals of Double Beta Decay in
a 76Ge Detector and first Application
to the Heidelberg-Moscow Experiment"

-------- Abstract --------

The identification of signals of neutrinoless double beta decay is a question of extreme interest. Starting from the Monte Carlo calculated time history and spatial energy distribution of neutrinoless double beta events, for the first time the expected pulse shapes to be observed in a big 76Ge detector have been calculated 'microscopically' , by using the Poisson Superfish code for determination of the field distribution in the detector. It is shown, that for the majority of 0nu beta-beta events it is not possible to differentiate between the contributions of different particle physics parameters entering into the \onbb decay process - in the mass mechanism the effective neutrino mass and the right-handed weak current parameters lambda, eta. It is shown, that on the other hand it is possible in a 76Ge double beta decay experiment to reject a background of larger sizes (high multiplicity) gamma events by selecting low size (low multiplicity) events. First application of the theoretical beta-beta pulses to events from the line observed at 0nu beta-beta (Phys. Lett. B 586 (2004) 198 and NIMA 522 (2004) 371) show very good agreement. It is shown further that a good position determination of beta-beta events in the detector is possible. By the same type of calculation it is shown that use of the pulse shapes of the 1592 keV double escape line of the 2614 keV gamma-transition from 228Th for calibrating a neuronal net for search of events of neutrinoless double beta decay has a sound basis.

Last modification (I.Krivosheina): 25/12/2007