Coulomb gauge Gribov copies and the confining potential

We study the approach, initiated by Marinari et al., to the static inter-quark potential based on Polyakov lines of finite temporal extent, evaluated in Coulomb gauge. We show that, at small spatial separations, the potential can be understood as being between two separately gauge invariant colour charges. At larger separations Gribov copies obstruct the non-perturbative identification of individually gauge invariant colour states. We demonstrate, for the first time, how gauge invariance can be maintained quite generally by averaging over Gribov copies. This allows us to extend the analysis of the Polyakov lines and the corresponding, gauge invariant quark-antiquark state to all distance scales. Using large scale lattice simulations, we show that this interpolating state possesses a good overlap with the ground state in the quark-antiquark sector and yields the full static inter-quark potential at all distances. A visual representation of the Gribov copies on the lattice is also presented.Comment: 22 pages, 9 figures, v2: minor changes, references adde

Highly Sideophile Element Abundance Constraints on the Nature of the Late Accretionary Histories of Earth, Moon and Mars

The highly siderophile elements (HSE) include Re, Os, Ir, Ru, Pt and Pd. These elements are initially nearly-quantitatively stripped from planetary silicate mantles during core segregation. They then may be re-enriched in mantles via continued accretion sans continued core segregation. This suite of elements and its included long-lived radiogenic isotopes systems (Re-187 (right arrow) Os-187; Pt-190 (right arrow) Os-186) can potentially be used to fingerprint the characteristics of late accreted materials. The fingerprints may ultimately be useful to constrain the prior nebular history of the dominant late accreted materials, and to compare the proportion and genesis of late accretionary materials added to the inner planets. The past ten years have seen considerable accumulation of isotopic and compositional data for HSE present in the Earth's mantle, lunar mantle and impact melt breccias, and Martian meteorites. Here we review some of these data and consider the broader implications of the compiled data

Measurement of 1.7 to 74 MeV polarised gamma rays with the HARPO TPC

Current {\gamma}-ray telescopes based on photon conversions to electron-positron pairs, such as Fermi, use tungsten converters. They suffer of limited angular resolution at low energies, and their sensitivity drops below 1 GeV. The low multiple scattering in a gaseous detector gives access to higher angular resolution in the MeV-GeV range, and to the linear polarisation of the photons through the azimuthal angle of the electron-positron pair. HARPO is an R&D program to characterise the operation of a TPC (Time Projection Chamber) as a high angular-resolution and sensitivity telescope and polarimeter for {\gamma} rays from cosmic sources. It represents a first step towards a future space instrument. A 30 cm cubic TPC demonstrator was built, and filled with 2 bar argon-based gas. It was put in a polarised {\gamma}-ray beam at the NewSUBARU accelerator in Japan in November 2014. Data were taken at different photon energies from 1.7 MeV to 74 MeV, and with different polarisation configurations. The electronics setup is described, with an emphasis on the trigger system. The event reconstruction algorithm is quickly described, and preliminary measurements of the polarisation of 11 MeVphotons are shown.Comment: Proceedings VCI201

The Gamma Ray Burst section of the White Paper on the Status and Future of Very High Energy Gamma Ray Astronomy: A Brief Preliminary Report

Original paper can be found at: http://proceedings.aip.org/proceedings/ Copyright American Institute of Physics DOI: 10.1063/1.2943545otherPeer reviewe

Detection of the BL Lac Object H1426+428 at TeV Gamma Ray Energies

A very high energy (VHE) gamma-ray signal has been detected at the 5.4 sigma level from H1426+428, an x-ray selected BL Lacertae object at a redshift of 0.129. The object was monitored from 1995 - 1998 with the Whipple 10m imaging atmospheric Cherenkov telescope as part of a general blazar survey; the results of these observations, although not statistically significant, were consistently positive. X-ray observations of H1426+428 during 1999 with the BeppoSAX instrument revealed that the peak of its synchrotron spectrum occurs at > 100 keV, leading to the prediction of observable TeV emission from this object. H1426+428 was monitored extensively at the Whipple Observatory during the 1999, 2000, and 2001 observing seasons. The strongest TeV signals were detected in 2000 and 2001. During 2001, an integral flux of 2.04 +/- 0.35 x10e-11 cm-2 s-1 above 280 GeV was recorded from H1426+428. The detection of H1426+428 supports the idea that, as also seen in Markarian 501 and 1ES2344+514, BL Lacertae objects with extremely high synchrotron peak frequencies produce gamma rays in the TeV range.Comment: 35 pages, 7 figures, accepted by ApJ Two upper limits in Table 3 (upper limits for 1995 and 1997) are different from the ApJ versio

Search for TeV Gamma-Rays from Shell-Type Supernova Remnants

If cosmic rays with energies <100 TeV originate in the galaxy and are accelerated in shock waves in shell-type supernova remnants (SNRs), gamma-rays will be produced as the result of proton and electron interactions with the local interstellar medium, and by inverse Compton emission from electrons scattering soft photon fields. We report on observations of two supernova remnants with the Whipple Observatory's 10 m gamma-ray telescope. No significant detections have been made and upper limits on the >500 GeV flux are reported. Non-thermal X-ray emission detected from one of these remnants (Cassiopeia A) has been interpreted as synchrotron emission from electrons in the ambient magnetic fields. Gamma-ray emission detected from the Monoceros/Rosette Nebula region has been interpreted as evidence of cosmic-ray acceleration. We interpret our results in the context of these observations.Comment: 4 pages, 2 figures, to appear in the proceedings of 26th International Cosmic Ray Conference (Salt Lake City, 1999