Dean Morgan

Probing quantum decoherence with high-energy neutrinos

Abstract We consider the prospects for observing the effects of quantum decoherence in high-energy (TeV–PeV) neutrinos from astrophysical sources. In particular, we study galactic sources of electron antineutrinos produced in the decay of ultra-high energy neutrons. We find that next generation neutrino telescopes should be capable of placing limits on quantum decoherence effects over multi-kiloparsec baselines, surpassing current bounds by a factor of 10 12 to 10 33 , depending on the model considered.

Lorentz and CPT invariance violation in high-energy neutrinos

High-energy neutrino astronomy will be capable of observing particles at both extremely high energies and over extremely long baselines. These features make such experiments highly sensitive to the effects of CPT and Lorentz violation. In this article, we review the theoretical foundation and motivation for CPT and Lorentz violating effects, and then go on to discuss the related phenomenology within the neutrino sector. We describe several signatures which might be used to identify the presence of CPT or Lorentz violation in next generation neutrino telescopes and cosmic ray experiments. In many cases, high-energy neutrino experiments can test for CPT and Lorentz violation effects with much greater precision than other techniques.

Probing quantum decoherence in atmospheric neutrino oscillations with a neutrino telescope

Quantum decoherence, the evolution of pure states into mixed states, may be a feature of quantum gravity. In this paper, we show how these effects can be modelled for atmospheric neutrinos and illustrate how the standard oscillation picture is modified. We examine how neutrino telescopes, such as ANTARES, are able to place upper bounds on these quantum decoherence effects.

Neutrino telescope modelling of Lorentz invariance violation in oscillations of atmospheric neutrinos

One possible feature of quantum gravity may be the violation of Lorentz invariance. In this paper, we consider one particular manifestation of the violation of Lorentz invariance, namely modified dispersion relations for massive neutrinos. We show how such modified dispersion relations may affect atmospheric neutrino oscillations. We then consider how neutrino telescopes, such as ANTARES, may be able to place bounds on the magnitude of this type of Lorentz invariance violation.

On multiple adsorptions of hydrogen atoms on graphene

First-principles calculations using the Vienna Ab Initio Simulation Package (VASP) have been performed in order to scrutinize the hydrogen–graphene interaction. Emphasis has been placed on how surface relaxation and the prior chemisorption of one, two and three hydrogen atoms on graphene affect the adsorption properties of an encroaching gas phase hydrogen atom. Chemisorption at the para site was found to be barrierless, while it has been shown that a stable ortho adsorbate can form directly from the gas phase. Adsorption of the third and fourth H atoms was found in all cases to have a significant barrier. The resultant minimum energy structures show a reasonable agreement with scanning tunneling microscopy images obtained by Hornekaer et al (2007 Chem. Phys. Lett. 446 237).

BEAM TEST of the ATLAS SILICON DETECTOR MODULES with BINARY READOUT in the CERN H8 BEAM in 19961

detector with small angle stereo readout. Readout will be AC-coupled from n-type implant strips in n-bulk crystals. increased depletion voltage [3], the junctions will be at the nstrips allowing the possibility of operation under partial depletion of the silicon. The readout electronics [4] employs a 1 bit binary scheme whereby only hits above a single threshold are recorded. In such a scheme the required resolution is achieved with 75pm pitch detectors. Noise OccuPancY must be well below not to exceed the bandwidth of the data transmission system. A key Derformance reauirement of such a system is to maintain are reprted from a beam test Of Prototype After radiation induced type inversion of the bulk and micro strip detectors and front-end electronics designed for use at the LHC. The detector assemblies were 12 cm long and were read out with binary electronics. Both irradiated and unirradiated assemblies were measured in a 1.56T magnetic field for efficiency, noise occupancy, and resolution as a function of bias voltage, binary hit threshold, and detector rotation angle with respect to the beam direction. Measurements were also performed at a particle flux comparable to the one expected at the LHC.

Some general properties of the renormalized stress-energy tensor for static quantum states on (n + 1)-dimensional spherically symmetric black holes

We study the renormalized stress-energy tensor (RSET) for static quantum states on (nxa0+xa01)-dimensional, static, spherically symmetric black holes. By solving the conservation equations, we are able to write the stress-energy tensor in terms of a single unknown function of the radial co-ordinate, plus two arbitrary constants. Conditions for the stress-energy tensor to be regular at event horizons (including the extremal and “ultra-extremal” cases) are then derived using generalized Kruskal-like co-ordinates. These results should be useful for future calculations of the RSET for static quantum states on spherically symmetric black hole geometries in any number of space-time dimensions.

Spectral difference methods in bound state calculations.

The use of discrete variable representations is now commonplace in chemical dynamics calculations. In this paper, we employ spectral difference methods to speed up these calculations. We present five new spectral difference weight functions and compare them with those that already exist in the literature for two different bound state problems. We find that one particular weight we propose, based on a Gaussian function, outperforms all other weights.

Pulse height of MIP's in an n-side silicon microstrip detector after proton irradiation with a fluence of 1x10**15 p cm**(-2)

We have irradiated an n-side silicon microstrip detector to an equivalent high energy fluence of 1/spl times/10/sup 15/ p cm/sup -2/ using 55 MeV protons. We determined the median pulse height to be 0.7 fC at a bias voltage of 180 V, and deduced a depletion region of about 80 /spl mu/m.