•Iliana Brancus1,2, Juergen Wentz1,2, Bogdan Mitrica1,
Heinigerd Rebel2,3, Mirel Petcu1, Alexandru Bercuci1,2,
Cristina Aiftimiei1, Marin Duma1 und Gabriel Toma1
1National Institute of Physics and Nuclear Engineering,
Bucharest, Roumania
2Forschungszentrum Karlsruhe, Institut fur Kernphysik, Karlsruhe,
Germany
3Faculty of Physics and Astronomy, University of Heidelberg,
Germany
The charge ratio of atmospheric muons is a quantity sensitive to hadronic
interactions of cosmic rays and to the influence of the geomagnetic field.
Experimental information is of current interest for tuning models used
for calculations of atmospheric neutrino fluxes. We report about experimental
studies based on observation of the life time of the muons stopped in the
absorber layers (aluminum support) of a detector WILLIconsisting
of 16 plastic scintillator modules ( 90 x 90 cm2), surrounded
by veto counters. The detector is mounted in a rotatable frame and installed
in IFIN Bucharest (vertical geomagnetic cut-off rigigity of 5.6 GV). Measurements
of the asymmetry of the muon charge ratio in East and West directions,
observed with a mean zenith angle of 35o results in valuues
of the relative asymmetry of the charge ratio in values decreasing from
0.25 to 0.20 in the muon momentum range 0.35- 0.50 GeV/c relevant to the
atmospheric neutrino anomaly.