Searcharxiv⌕ Search

arXiv subjects

Petr Vogel

Publications and source records attributed to Petr Vogel.

44 records · Page 3Linked to original sources
arXiv2000

Nuclear Physics Neutrino PreTown Meeting: Summary and Recommendations

In preparation for the nuclear physics Long Range Plan exercise, a group of 104 neutrino physicists met in Seattle September 21-23 to discuss both the present state of the field and the new opportunities of the next decade. This report summarizes the conclusions of that meeting and presents its recommendations. Further information is available at the workshop's web site. This report will be further reviewed at the upcoming Oakland Town Meeting.

nucl-th↗
arXiv2000

Spin-Dependent WIMPs in DAMA?

We investigate whether the annual modulation observed in the DAMA experiment can be due to a weakly-interacting massive particle (WIMP) with an axial-vector (spin-dependent; SD) coupling to nuclei. We evaluate the SD WIMP-proton cross section under the assumption that such scattering accounts for the DAMA modulation, and we do the same for a SD WIMP-neutron cross section. We show that SD WIMP-proton scattering is ruled out in a model-independent fashion by null searches for energetic neutrinos from WIMP annihilation in the Sun, and that SD WIMP-neutron scattering is ruled out for WIMP masses > 20 GeV by the null result with the DAMA Xe detector. A SD WIMP with mass < 20 GeV is still compatible, but only if the SD WIMP-neutron interaction is four orders of magnitude greater than the WIMP-proton interaction.

hep-ph↗
arXiv1999

What might we learn from a future supernova neutrino signal?

Neutrinos from a future Galactic supernova will be detected by several large underground detectors, in particular by SuperKamiokande (SK) and the Sudbury Neutrino Observatory (SNO). If, as expected, the $ν_μ$ and $ν_τ$ neutrinos have somewhat higher energy on average that the electron neutrinos, they will dominate the neutral current response. The ways to separate the neutral and charged current signals will be discussed, and the best strategy to measure the possible time delay of the neutral current events will be outlined. Given the expected count rates, one will be able to measure in this way the $ν_τ$ mass down to about 30 eV in SNO and to 50 eV in SuperKamiokande. Another application to be discussed is the supernova localization by the neutrino signal, prior to or independently of the electromagnetic signal. The accuracy with which this can be accomplished using the angular distributions of the reactions will be estimated. With two or more detectors one can, in principle, attempt triangulation based on the arrival time of the neutrinos. It will be argued that for realistic parameters this method will be very difficult and likely leads only to crude localization.

astro-ph↗
arXiv1999

Nuclear Physics of Double Beta Decay

Study of the neutrinoless $ββ$ decay allows us to put a stringent limit on the effective neutrino Majorana mass, a quantity of fundamental importance. To test our ability to evaluate the nuclear matrix elements that govern the decay rate, it is desirable to be able to describe the allowed two-neutrino decay. It is argued that only low-lying virtual intermediate states are important for that process, and thus it appears that the large-scale shell model evaluation, free from the various difficulties of QRPA, is the preferred method. In the $0ν$ decay, it is shown that there is a substantial cancellation between the paired and broken pair pieces of the nuclear wave function. Thus, despite the popular claim to the contrary, one expects that the $0ν$ rate is also sensitive to the details of nuclear structure. This is reflected in the spread of the theoretical values, leading to the uncertainty of about factor 2-3 in the deduced $ $ limit. Finally, brief comment about the $0ν$ decay with the exchange of a very heavy neutrino are made.

nucl-th↗
arXiv1999

Neutrino nucleus scattering

The status of the theoretical description of neutrino-nuclear interaction for low and intermediate energies is reviewed and its result compared with the existing data. Particular emphasis is on $^{12}$C, the ingredient of liquid scintillator, and on $^{16}$ the main component of the water Čerenkov detectors. First, I show that the data on the exclusive process populating the ground state of $^{12}$N are well reproduced by the theory. This is also the case for the excitation of the continuum with low energy neutrinos from the muon decay at rest and for the muon capture. However, for not yet understood reasons, the theory overestimates the cross section for higher energy neutrinos from the pion decay in flight, by up to 50%. I also show that the Continuum Random Phase Approximation and the Relativistic Fermi Gas model give very similar full and differential cross sections for the neutrino energies of several hundred MeV, thus checking one method against the other.

nucl-th↗
arXiv1998

Shell model calculation of the beta- and beta+ partial halflifes of 54Mn and other unique second forbidden beta decays

The nucleus 54Mn has been observed in cosmic rays. In astrophysical environments it is fully stripped of its atomic electrons and its decay is dominated by the beta- branch to the 54Fe ground state. Application of 54Mn based chronometer to study the confinement of the iron group cosmic rays requires knowledge of the corresponding halflife, but its measurement is impossible at the present time. However, the branching ratio for the related beta+ decay of 54Mn was determined recently. We use the shell model with only a minimal truncation and calculate both beta+ and beta- decay rates of 54Mn. Good agreement for the beta+ branch suggests that the calculated partial halflife of the beta- decay, (4.94 \pm 0.06) x 10^5 years, should be reliable. However, this halflife is noticeably shorter than the range 1-2 x 10^6 y indicated by the fit based on the 54Mn abundance in cosmic rays. We also evaluate other known unique second forbidden beta decays from the nuclear p and sd shells (10Be, 22Na, and two decay branches of 26Al) and show that the shell model can describe them with reasonable accuracy as well.

nucl-th↗
arXiv1998

Isovector Pairing in Odd-A Proton-Rich Nuclei

A simple model based on the group SO(5) suggests that both the like-particle and neutron-proton components of isovector pairing correlations in odd-A nuclei are Pauli blocked. The same effect emerges from Monte Carlo Shell-model calculations of proton-rich nuclei in the full fp shell. There are small differences between the two models in their representation of the effects of an odd nucleon on the competition between like-particle and neutron-proton pairing, but they can be understood and reduced by using a two-level version of the SO(5) model. On the other hand, in odd-odd nuclei with N not equal to Z SO(5) disagrees more severely with the shell model because it incorrectly predicts ground-state isospins. The shell model calculations for any fp-shell nuclei can be extended to finite temperature, where they show a decrease in blocking.

nucl-th↗