291 research outputs found
The KARMEN anomaly, light neutralinos and type II supernovae
The KARMEN experiment observes a time anomaly in events induced by pion decay
at rest. This anomaly can be ascribed to the production of a new weakly
interacting particle X with mass m_X\sim 34 MeV. We show that a recently
proposed identification of the X particle with the lightest neutralino \chi in
the frame work of the MSSM with broken R parity is in contradiction to optical
observations of type II supernovae.Comment: 6 pages latex, 1 eps figure. Slightly revised (cf. title), matches
published versio
Ultrahigh energy cosmic rays and new particle physics
The current status of the ultrahigh energy cosmic ray (UHE CR) enigma and
several proposed solutions involving particle physics beyond the standard model
are discussed. Emphasis is given to top--down models, and as a main example,
supermassive dark matter as galactic source for UHE CR and the status of its
experimental signatures (galactic anisotropy, chemical composition and
clustering) is reviewed. Then different approaches to calculate fragmentation
spectra of supermassive particles are discussed. Finally, it is argued that UHE
neutrinos cannot be - neither directly or indirectly - responsible for the
observed vertical air showers.Comment: 14 pages, 5 figures. Invited talk at ``CAPP-2K'', Verbier, July 200
Non-adiabatic oscillations of supernova neutrinos
The level-crossing probability, local and global adiabaticity conditions are
discussed for 2-flavour neutrino oscillations in matter with arbitrary mixing
angle . Different approximations for the survival probability of
supernova neutrinos are compared. Results of a combined likelihood analysis of
the observed SN1987A neutrino signal and of the latest solar neutrino data
including the recent SNO CC measurement are presented.Comment: 5 pages, 8 eps figures, JHEP style included. Talk presented at
"Neutrino masses and mixings", Les Houches, June 2001, and at "EPS HEP 2001",
Budapest, July 200
Ultrahigh energy neutrino interactions and weak-scale string theories
It has been suggested that ultrahigh energy neutrinos can acquire
cross-sections approaching hadronic size if the string scale is as low as 1-10
TeV. In this case, the vertical air showers observed with energies above the
Greisen-Zatsepin-Kuzmin cutoff at E approximately 6x10^{19} eV could be
initiated by neutrinos which are the only known primaries able to travel long
distances unimpeded. We have calculated the neutrino-nucleon cross-section due
to the exchange of Kaluza-Klein excitations of the graviton in a field
theoretical framework. We have found that the neutrino-nucleon cross section
and the transferred energy per interaction are too small to explain vertical
showers even in the most optimistic scenario.Comment: 7 pages, 3 figures; discussion of the sensitivity of Auger/Owl
shortened, matches version to be publishe
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