A faraway quasar in the direction of the highest energy Auger event

The highest energy cosmic ray event reported by the Auger Observatory has an energy of 148 EeV. It does not correlate with any nearby (z<0.024) object capable of originating such a high energy event. Intrigued by the fact that the highest energy event ever recorded (by the Fly`s Eye collaboration) points to a faraway quasar with very high radio luminosity and large Faraday rotation measurement, we have searched for a similar source for the Auger event. We find that the Auger highest energy event points to a quasar with similar characteristics to the one correlated to the Fly`s Eye event. We also find the same kind of correlation for one of the highest energy AGASA events. We conclude that so far these types of quasars are the best source candidates for both Auger and Fly`s Eye highest energy events. We discuss a few exotic candidates that could reach us from gigaparsec distances.

Absolute normalization for uncorrelated background with the event mixing technique

We present a method to determine the magnitude of the uncorrelated background distribution obtained with the event mixing technique, through the simultaneous observation of the projectile elastic scattering in different detectors, which correspond to random coincidences. The procedure is tested with alpha-d angular correlation data from the (6)Li + (59)Co reaction at E(lab) = 29.6 MeV. We also show that the method can be applied using the product of singles events, when singles measurements are available. (C) 2009 Elsevier B.V. All rights reserved.

Reaction microtextures of monazite: Correlation between chemical and age domains in the Nazare Paulista migmatite, SE Brazil

Back-scattered imaging, X-ray element mapping and electron microprobe analyzer (EMPA) chemical dating reveal complex compositional and age zoning in monazite crystals from different layers and textural positions in a garnet-bearing migmatite in SE Brazil. Y-rich (variable Y(2)O(3), averaging 2.5 wt.%) relict cores are preserved in mesosome and melanosome monazite, and correspond to 793 +/- 6 Ma inherited crystals possibly generated in a previous metamorphic event. These cores are overgrown and widely replaced by two generations of monazite, which are present in all migmatite layers. The first, also Y-rich (average 2.5 wt.% Y(2)O(3)), was produced at similar to 635 Ma during prograde metamorphism under subsolidus conditions, while the second has an Y-poor (<1.5 wt.% Y(2)O(3)), low Th/U signature, and precipitated from low Y and HREE anatectic melts produced by reactions in which garnet was inert. Quartz-rich trondhjemitic leucosome represents lower temperature melt (bearing some subsolidus quartz and garnet with included monazite) formed at temperatures below muscovite breakdown; its Y-poor monazite indicates an age of 617 +/- 6 Ma. Granitic leucosomes formed close to peak metamorphic conditions (T>750 degrees C) above muscovite breakdown have their slightly younger character confirmed by a 609 +/- 7 Ma low-Y monazite age. A similar 606 +/- 5 Ma age was obtained for low-Y monazite rims and domains in mesosome and melanosome, and reflects the time of monazite saturation in interstitial granitic melt that was trapped in these layers. Our results confirm that inherited monazite crystals can be preserved during partial melting at temperatures above muscovite breakdown. Moreover, careful textural control aided by X-ray chemical mapping may allow monazite generated at different stages in a similar to 25 Myr prograde metamorphic path to be identified and dated using an electron microprobe. (C) 2008 Elsevier B.V. All rights reserved.