Phase soliton and pairing symmetry of a two-band superconductor: Role of the proximity effect

We suggest a mechanism which promotes the existence of a phase soliton -- topological defect formed in the relative phase of superconducting gaps of a two-band superconductor with s+- type of pairing. This mechanism exploits the proximity effect with a conventional s-wave superconductor which favors the alignment of the phases of the two-band superconductor which, in the case of s+- pairing, are pi-shifted in the absence of proximity. In the case of a strong proximity such effect can be used to reduce soliton's energy below the energy of a soliton-free state thus making the soliton thermodynamically stable. Based on this observation we consider an experimental setup, applicable both for stable and metastable solitons, which can be used to distinguish between s+- and s++ types of pairing in the iron-based multiband superconductors.Comment: New references, added discussion about self-consistency of the GL description of a phase soliton in the presence of a proximity patc

Predicting Proton-Air Cross Sections at sqrt s ~30 TeV, using Accelerator and Cosmic Ray Data

We use the high energy predictions of a QCD-inspired parameterization of all accelerator data on forward proton-proton and antiproton-proton scattering amplitudes, along with Glauber theory, to predict proton-air cross sections at energies near \sqrt s \approx 30 TeV. The parameterization of the proton-proton cross section incorporates analyticity and unitarity, and demands that the asymptotic proton is a black disk of soft partons. By comparing with the p-air cosmic ray measurements, our analysis results in a constraint on the inclusive particle production cross section.Comment: 9 pages, Revtex, uses epsfig.sty, 5 postscript figures. Minor text revisions. Systematic errors in k included, procedure for extracting k clarified. Previously undefined symbols now define

TeV Gamma Rays from Geminga and the Origin of the GeV Positron Excess

The Geminga pulsar has long been one of the most intriguing MeV-GeV gamma-ray point sources. We examine the implications of the recent Milagro detection of extended, multi-TeV gamma-ray emission from Geminga, finding that this reveals the existence of an ancient, powerful cosmic-ray accelerator that can plausibly account for the multi-GeV positron excess that has evaded explanation. We explore a number of testable predictions for gamma-ray and electron/positron experiments (up to ~100 TeV) that can confirm the first "direct" detection of a cosmic-ray source.Comment: 4 pages and 3 figures; Minor revisions, accepted for publication in Physical Review Letter

Cluster Analysis of Extremely High Energy Cosmic Rays in the Northern Sky

The arrival directions of extremely high energy cosmic rays (EHECR) above $4\times10^{19}$ eV, observed by four surface array experiments in the northern hemisphere,are examined for coincidences from similar directions in the sky. The total number of cosmic rays is 92.A significant number of double coincidences (doublet) and triple coincidences (triplet) are observed on the supergalactic plane within the experimental angular resolution. The chance probability of such multiplets from a uniform distribution is less than 1 % if we consider a restricted region within $\pm 10^{\circ}$ of the supergalactic plane. Though there is still a possibility of chance coincidence, the present results on small angle clustering along the supergalactic plane may be important in interpreting EHECR enigma. An independent set of data is required to check our claims.Comment: 9 pages, 6 tables, 8 figures. submitted to Astroparticle Physic