Stephen Reucroft

ULTRAHIGH ENERGY COSMIC RAYS: THE STATE OF THE ART BEFORE THE AUGER OBSERVATORY

In this review we discuss the important progress made in recent years towards understanding the experimental data on cosmic rays with energies

High energy physics in the atmosphere: Phenomenology of cosmic ray air showers

\agt 10^{19}

Extensive air showers with TeV scale quantum gravity

eV. We begin with a brief survey of the available data, including a description of the energy spectrum, mass composition, and arrival directions. At this point we also give a short overview of experimental techniques. After that, we introduce the fundamentals of acceleration and propagation in order to discuss the conjectured nearby cosmic ray sources. We then turn to theoretical notions of physics beyond the Standard Model where we consider both exotic primaries and exotic physical laws. Particular attention is given to the role that TeV-scale gravity could play in addressing the origin of the highest energy cosmic rays. In the final part of the review we discuss the potential of future cosmic ray experiments for the discovery of tiny black holes that should be produced in the Earths atmosphere if TeV-scale gravity is realized in Nature.

Scintillating optical fiber trajectory detectors

The properties of cosmic rays with energies above 10 6 GeV have to be deduced from the spacetime structure and particle content of the air showers which they initiate. In this review we summarize the phenomenology of these giant air showers. We describe the hadronic interaction models used to extrapolate results from collider data to ultra high energies, and discuss the prospects for insights into forward physics at the LHC. We also describe the main electromagnetic processes that govern the longitudinal shower evolution, as well as the lateral spread of particles. Armed with these two principal shower ingredients and motivation from the underlying physics, we provide an overview of some of the different methods proposed to distinguish primary species. The properties of neutrino interactions and the potential of forthcoming experiments to isolate deeply penetrating showers from baryonic cascades are also discussed. We finally venture into a terra incognita endowed with TeV-scale gravity and explore anomalous neutrino-induced showers.

SSPM Readout of LSO, (Lu-Y)AP:Ce and PWO-II Pixels for PET Detector Modules

One of the possible consequences of the existence of extra degrees of freedom beyond the electroweak scale is the increase of neutrino-nucleon cross sections ({sigma}{sub {nu}N}) beyond standard model predictions. At ultrahigh energies this may allow the existence of neutrino-initiated extensive air showers. In this paper, we examine the most relevant observables of such showers. Our analysis indicates that the future Pierre Auger Observatory could be potentially powerful in probing models with large compact dimensions.

On the Cross-Correlation between the Arrival Direction of Ultra-High-Energy Cosmic Rays, BL Lacertae Objects, and EGRET Detections: A New Way to Identify EGRET Sources?

Abstract Measurements of attenuation in several types of plastic scintillating optical fibers give attenuation lengths varying from 0.8 to 1.5 m. By comparing attenuation as a function of wavelength in fibers of different thicknesses we infer the contributions to the attenuation from reflection losses and bulk scintillation losses. We find good agreement between these values and calculated estimates of attenuation in scintillator. We have also calculated the effective scintillation efficiency of small fibers relative to that of bulk scintillator (for scintillator with dimethyl POPOP as the waveshifting dye) for the two cases of optically coupled and decoupled fibers. Scintillating fiber ribbons made of 200 μm square cross section fibers were exposed to relativistic iron nuclei at the LBL Bevalac, and positional resolution of 70 μm was obtained. Relativistic neon and carbon were also detected in these ribbons. In a similar exposure of 100 μm fibers to 50 MeV/n nitrogen nuclei at the NSCL cyclotron, Michigan State University, a positional resolution of about 50 μm was obtained.

Extragalactic sources for ultrahigh energy cosmic ray nuclei

We have studied the performance of recently developed solid state photomultipliers (SSPMs) with 2.1times2.1 mm2 sensitive area as a readout for small LSO, (Lu-Y)AP:Ce and PWO-II scintillator crystals. The SSPM is based on the p+-p-n+ structure which was optimized for blue/UV light detection. It operates at a gain of >105 and shows >25% photon detection efficiency in the 380-600 nm spectral range. Energy and timing spectra were measured using a 22Na gamma source. Energy resolutions of 13%, 25% and 50% FWHM were measured for 511 keV gammas with the LSO, (Lu-Y)AP:Ce and PWO-II scintillator crystals respectively. A coincidence timing resolution of 710 ps (FWHM) was measured between two identical LSO+SSPM modules.

The Nuclear Dependence of Charm Hadroproduction

With the aim of testing recent claims for a particularly strong correlation between ultra-high-energy cosmic rays (UHECRs), observed with the AGASA and Yakutsk experiments, and a sample of BL Lacertae objects, we conduct a blind statistical assessment. We search for associations between the same set of BL Lac objects and the arrival directions of 33 relevant UHECRs observed with the Haverah Park and Volcano Ranch experiments. Within the accuracy of the angle determination, there are no positional coincidences. The probability that this null result arises as a statistical fluctuation from the strongly correlated case is less than 5%. This implies that the possible correlation between the arrival directions of UHECRs and BL Lac objects is not statistically sustained. We discuss the impact of our findings on the proposed additional connection among UHECRs, BL Lac objects, and EGRET γ-ray blazars. Recently, such an association was used as a classification technique for EGRET sources. Here we show that its main underlying hypothesis (i.e., the EGRET angular uncertainty is twice that quoted in the third EGRET catalog) grossly underestimates the goodness of existing γ-ray data.

THE MYSTERIOUS ULTRAHIGH ENERGY COSMIC RAY CLUSTERING

In this article we examine the hypothesis that the highest energy cosmic rays are complex nuclei from extragalactic sources. Under reasonable physical assumptions, we show that the nearby metally rich starburst galaxies (M82 and NGC 253) can produce all the events observed above the ankle. This requires diffusion of particles below

Gluino air showers as a signal of split supersymmetry

{10}^{20} \mathrm{eV}