VERITAS Observations of the Coma Cluster of Galaxies

Clusters of galaxies are one of the few prominent classes of objects predicted to emit gamma rays not yet detected by satellites like EGRET or ground-based Imaging Atmospheric Cherenkov Telescopes (IACTs). The detection of Very High Energy (VHE, E > 100 GeV) gamma rays from galaxy clusters would provide insight into the morphology of non-thermal particles and fields in clusters. VERITAS, an array of four 12-meter diameter IACTs, is ideally situated to observe the massive Coma cluster, one of the best cluster candidates in the Northern Hemisphere. This contribution details the results of VERITAS observations of the Coma cluster of galaxies during the 2007-2008 observing season.Comment: Submitted to Proceedings of "4th Heidelberg International Symposium on High Energy Gamma-Ray Astronomy 2008

Lattice simulations with Nf=2+1N_f=2+1 improved Wilson fermions at a fixed strange quark mass

The explicit breaking of chiral symmetry of the Wilson fermion action results in additive quark mass renormalization. Moreover, flavour singlet and non-singlet scalar currents acquire different renormalization constants with respect to continuum regularization schemes. This complicates keeping the renormalized strange quark mass fixed when varying the light quark mass in simulations with $N_f=2+1$ sea quark flavours. Here we present and validate our strategy within the CLS (Coordinated Lattice Simulations) effort to achieve this in simulations with non-perturbatively order-$a$ improved Wilson fermions. We also determine various combinations of renormalization constants and improvement coefficients.Comment: 18 pages, 11 Figures, V2: References added/updated, all fits rerun with improved statistics for ensemble N204, also using the final values for the improvement coefficients A and b_P-b_A (very minor impact), The figures have been replotted accordingly. (The differences with respect to V1 are invisible to the human eye). Minor change

The Atmospheric Monitoring System of the JEM-EUSO Space Mission

An Atmospheric Monitoring System (AMS) is a mandatory and key device of a space-based mission which aims to detect Ultra-High Energy Cosmic Rays (UHECR) and Extremely-High Energy Cosmic Rays (EHECR) from Space. JEM-EUSO has a dedicated atmospheric monitoring system that plays a fundamental role in our understanding of the atmospheric conditions in the Field of View (FoV) of the telescope. Our AMS consists of a very challenging space infrared camera and a LIDAR device, that are being fully designed with space qualification to fulfil the scientific requirements of this space mission. The AMS will provide information of the cloud cover in the FoV of JEM-EUSO, as well as measurements of the cloud top altitudes with an accuracy of 500 m and the optical depth profile of the atmosphere transmittance in the direction of each air shower with an accuracy of 0.15 degree and a resolution of 500 m. This will ensure that the energy of the primary UHECR and the depth of maximum development of the EAS ( Extensive Air Shower) are measured with an accuracy better than 30\% primary energy and 120 $g/cm^2$ depth of maximum development for EAS occurring either in clear sky or with the EAS depth of maximum development above optically thick cloud layers. Moreover a very novel radiometric retrieval technique considering the LIDAR shots as calibration points, that seems to be the most promising retrieval algorithm is under development to infer the Cloud Top Height (CTH) of all kind of clouds, thick and thin clouds in the FoV of the JEM-EUSO space telescope

Validation of a modified clinical risk score to predict cancer-specific survival for stage II colon cancer

Many patients with stage II colon cancer will die of their disease despite curative surgery. Therefore, identification of patients at high risk of poor outcome after surgery for stage II colon cancer is desirable. This study aims to validate a clinical risk score to predict cancer-specific survival in patients undergoing surgery for stage II colon cancer. Patients undergoing surgery for stage II colon cancer in 16 hospitals in the West of Scotland between 2001 and 2004 were identified from a prospectively maintained regional clinical audit database. Overall and cancer-specific survival rates up to 5 years were calculated. A total of 871 patients were included. At 5 years, cancer-specific survival was 81.9% and overall survival was 65.6%. On multivariate analysis, age ≥75 years (hazard ratio (HR) 2.11, 95% confidence intervals (CI) 1.57–2.85; P<0.001) and emergency presentation (HR 1.97, 95% CI 1.43–2.70; P<0.001) were independently associated with cancer-specific survival. Age and mode of presentation HRs were added to form a clinical risk score of 0–2. The cancer-specific survival at 5 years for patients with a cumulative score 0 was 88.7%, 1 was 78.2% and 2 was 65.9%. These results validate a modified simple clinical risk score for patients undergoing surgery for stage II colon cancer. The combination of these two universally documented clinical factors provides a solid foundation for the examination of the impact of additional clinicopathological and treatment factors on overall and cancer-specific survival

Direct determinations of the nucleon and pion σ\sigma terms at nearly physical quark masses

We present a high statistics study of the pion and nucleon light and strange quark sigma terms using $N_f=2$ dynamical non-perturbatively improved clover fermions with a range of pion masses down to $m_\pi\sim 150$ MeV and several volumes, $Lm_\pi=3.4$ up to $6.7$, and lattice spacings, $a=0.06-0.08$ fm, enabling a study of finite volume and discretisation effects for $m_\pi\gtrsim 260$ MeV. Systematics are found to be reasonably under control. For the nucleon we obtain $\sigma_{\pi N}=35(6)$ MeV and $\sigma_s=35(12)$ MeV, or equivalently in terms of the quark fractions, $f_{T_u}=0.021(4)$, $f_{T_d}=0.016(4)$ and $f_{T_s}=0.037(13)$, where the errors include estimates of both the systematic and statistical uncertainties. These values, together with perturbative matching in the heavy quark limit, lead to $f_{T_c}=0.075(4)$, $f_{T_b}=0.072(2)$ and $f_{T_t}=0.070(1)$. In addition, through the use of the (inverse) Feynman-Hellmann theorem our results for $\sigma_{\pi N}$ are shown to be consistent with the nucleon masses determined in the analysis. For the pion we implement a method which greatly reduces excited state contamination to the scalar matrix elements from states travelling across the temporal boundary. This enables us to demonstrate the Gell-Mann-Oakes-Renner expectation $\sigma_\pi=m_\pi/2$ over our range of pion masses.Comment: 31 pages, 18 figures, v2, small changes to text and figure

Medium Modifications from 4He(e,e'p)3H

Polarization transfer in quasi-elastic nucleon knockout is sensitive to the properties of the nucleon in the nuclear medium, including possible modification of the nucleon form factor and/or spinor. In our recently completed experiment E03-104 at Jefferson Lab we measured the proton recoil polarization in the 4He(e,e'p)3H reaction at a Q^2 of 0.8 (GeV/c)^2 and 1.3 (GeV/c)^2 with unprecedented precision. These data complement earlier data between 0.4 and 2.6 (GeV/c)^2 from both Mainz and Jefferson Lab. The measured ratio of polarization-transfer coefficients differs from a fully relativistic calculation, favoring either the inclusion of a medium modification of the proton form factors predicted by a quark-meson coupling model or strong charge-exchange final-state interactions. The measured induced polarizations agree well with the fully relativistic calculation and indicate that these strong final-state interactions may not be applicable.Comment: 7 pages, 3 figures. Based on invited talk presented by S. Strauch at "Sixth International Conference on Perspectives in Hadronic Physics", ICTP, Trieste, May 12-16, 200

Blazar surveys with WMAP and Swift

We present the preliminary results from two new surveys of blazars that have direct implications on the GLAST detection of extragalactic sources from two different perspectives: microwave selection and a combined deep X-ray/radio selection. The first one is a 41 GHz flux-limited sample extracted from the WMAP 3-yr catalog of microwave point sources. This is a statistically well defined sample of about 200 blazars and radio galaxies, most of which are expected to be detected by GLAST. The second one is a new deep survey of Blazars selected among the radio sources that are spatially coincident with serendipitous sources detected in deep X-ray images (0.3-10 keV) centered on the Gamma Ray Bursts (GRB) discovered by the Swift satellite. This sample is particularly interesting from a statistical viewpoint since a) it is unbiased as GRBs explode at random positions in the sky, b) it is very deep in the X-ray band (\fx \simgt $10^{-15}$ \ergs) with a position accuracy of a few arc-seconds, c) it will cover a fairly large (20-30 square deg.) area of sky, d) it includes all blazars with radio flux (1.4 GHz) larger than 10 mJy, making it approximately two orders of magnitude deeper than the WMAP sample and about one order of magnitude deeper than the deepest existing complete samples of radio selected blazars, and e) it can be used to estimate the amount of unresolved GLAST high latitude gamma-ray background and its anisotropy spectrum.Comment: 3 pages, 3 figures, to appear in Proc. of the 1st GLAST Symposium, Feb 5-8, 2007, Stanford, AIP, Eds. S. Ritz, P. F. Michelson, and C. Meega

Are we overusing IVF?

Peer reviewedPublisher PD