A thorough search for large-scale anisotropies in the distribution of arrival directions of cosmic rays detected above 10[sup]18 eV at the Pierre Auger Observatory is reported. For the first time, these large-scale anisotropy searches are performed as a function of both the right ascension and the declination and expressed in terms of dipole and quadrupole moments. Within the systematic uncertainties, no significant deviation from isotropy is revealed. Upper limits on dipole and quadrupole amplitudes are derived under the hypothesis that any cosmic ray anisotropy is dominated by such moments in this energy range. These upper limits provide constraints on the production of cosmic rays above 10[sup]18 eV, since they allow us to challenge an origin from stationary galactic sources densely distributed in the galactic disk and emitting predominantly light particles in all directions.
COBISS.SI-ID: 2627835
To interpret the mean depth of cosmic ray air shower maximum and its dispersion, we parametrize those two observables as functions of the first two moments of the ln A distribution. We examine the goodness of this simple method through simulations of test mass distributions. The application of the parameterization to Pierre Auger Observatory data allows one to study the energy dependence of the mean ln A and of its variance under the assumption of selected hadronic interaction models. We discuss possible implications of these dependences in term of interaction models and astrophysical cosmic ray sources.
COBISS.SI-ID: 2692859
We derive lower bounds on the density of sources of ultra-high energy cosmic rays from the lack of significant clustering in the arrival directions of the highest energy events detected at the Pierre Auger Observatory. The density of uniformly distributed sources of equal intrinsic intensity was found to be larger than ~ (0.06−5) × 10[sup]−4 Mpc[sup]−3 at 95% CL, depending on the magnitude of the magnetic deflections. Similar bounds, in the range (0.2−7) × 10[sup]−4 Mpc[sup]−3, were obtained for sources following the local matter distribution.
COBISS.SI-ID: 2756859
We search for bottomonium states in Υ(2S) [to] (b anti-b)γ decays with an integrated luminosity of 24.7 inverse fb recorded at the Υ(2S) resonance with the Belle detector at KEK, containing (157.8±3.6)×10[sup]6 Υ(2S) events. The (b anti-b) system is reconstructed in 26 exclusive hadronic final states composed of charged pions, kaons, protons, and K0S mesons. We find no evidence for the state recently observed around 9975 MeV in an analysis based on a data sample of 9.3×10[sup]6 Υ(2S) events collected with the CLEO III detector.
COBISS.SI-ID: 27041575
We report the results of a high-statistics search for H dibaryon production in inclusive Υ(1S) and Υ(2S) decays. No indication of an H dibaryon with a mass near the M_H=2m_Λ threshold is seen in either the H→Λpπ or ΛΛ decay channels and 90% confidence level branching-fraction upper limits are set that are between one and two orders of magnitude below the measured branching fractions for inclusive Υ(1S) and Υ(2S) decays to antideuterons. Since Υ(1S,2S) decays produce flavor-SU(3)-symmetric final states, these results put stringent constraints on H dibaryon properties. The results are based on analyses of 102 million Υ(1S) and 158 million Υ(2S) events collected with the Belle detector at the KEKB e+e− collider.
COBISS.SI-ID: 27039015