2,291 research outputs found
Observation of Galactic Gamma-ray Sources with VERITAS
We report on VERITAS observations at energies above 200 GeV of known or
potential galactic gamma-ray sources. The observed objects comprise pulsars,
pulsar wind nebulae, high-mass X-ray binaries and gamma-ray sources with
unknown counterparts in other wavelengths. Among the highlights are the
observation of variable gamma-ray emission from the X-ray binary LS I +61 303
and the detection of MGRO J1906+06/HESS J1906+063, an extended gamma-ray source
which could not be associated with any obvious counterpart at lower energies.Comment: Fixed typos in source name
HD66051: the first eclipsing binary hosting an early-type magnetic star
Early-type magnetic stars are rarely found in close binary systems. No such
objects were known in eclipsing binaries prior to this study. Here we
investigated the eclipsing, spectroscopic double-lined binary HD66051, which
exhibits out-of-eclipse photometric variations suggestive of surface brightness
inhomogeneities typical of early-type magnetic stars. Using a new set of
high-resolution spectropolarimetric observations, we discovered a weak magnetic
field on the primary and found intrinsic, element-dependent variability in its
spectral lines. The magnetic field structure of the primary is dominated by a
nearly axisymmetric dipolar component with a polar field strength G and an inclination with respect to the rotation axis of
. A weaker quadrupolar component is also likely to be
present. We combined the radial velocity measurements derived from our spectra
with archival optical photometry to determine fundamental masses (3.16 and 1.75
) and radii (2.78 and 1.39 ) with a 1-3% precision. We also
obtained a refined estimate of the effective temperatures (13000 and 9000 K)
and studied chemical abundances for both components with the help of
disentangled spectra. We demonstrate that the primary component of HD66051 is a
typical late-B magnetic chemically peculiar star with a non-uniform surface
chemical abundance distribution. It is not an HgMn-type star as suggested by
recent studies. The secondary is a metallic-line star showing neither a strong,
global magnetic field nor intrinsic spectral variability. Fundamental
parameters provided by our work for this interesting system open unique
possibilities for probing interior structure, studying atomic diffusion, and
constraining binary star evolution.Comment: 14 pages, 15 figures; accepted for publication in MNRA
V_cs from D_s to {\phi}l{\nu} semileptonic decay and full lattice QCD
We determine the complete set of axial and vector form factors for the Ds to
{\phi}l{\nu} decay from full lattice QCD for the first time. The valence quarks
are implemented using the Highly Improved Staggered Quark action and we
normalise the appropriate axial and vector currents fully nonperturbatively.
The q^2 and angular distributions we obtain for the differential rate agree
well with those from the BaBar experiment and, from the total branching
fraction, we obtain Vcs = 1.017(63), in good agreement with that from D to
Kl{\nu} semileptonic decay. We also find the mass and decay constant of the
{\phi} meson in good agreement with experiment, showing that its decay to
K{\bar{K}} (which we do not include here) has at most a small effect. We
include an Appendix on nonperturbative renormalisation of the complete set of
staggered vector and axial vector bilinears needed for this calculation.Comment: 19 pages, 13 figure
Single Pion Measurement Capabilities at SciBooNE
The precise knowledge of the single pion production cross-section of neutrino
around the ~1 GeV energy region is an essential ingredient in the
interpretation of neutrino oscillation experiments. The unique opportunities
and prospects of single pion measurements at SciBooNE are described.Comment: Proceedings of the 5th International Workshop on Neutrino-Nucleus
Interactions in the Few-GeV Region (NuInt07), Batavia, Illinois, 30 May - 3
Jun 200
Nonperturbative comparison of clover and highly improved staggered quarks in lattice QCD and the properties of the Ï• meson
We compare correlators for pseudoscalar and vector mesons made from valence strange quarks using the
clover quark and highly improved staggered quark (HISQ) formalisms in full lattice QCD. We use fully
nonperturbative methods to normalize vector and axial vector current operators made from HISQ quarks,
clover quarks and from combining HISQ and clover fields. This allows us to test expectations for the
renormalization factors based on perturbative QCD, with implications for the error budget of lattice QCD
calculations of the matrix elements of clover-staggered b-light weak currents, as well as further HISQ
calculations of the hadronic vacuum polarization.We also compare the approach to the (same) continuum limit
in clover and HISQ formalisms for the mass and decay constant of the Ï• meson. Our final results for these
parameters, using single-meson correlators and allowing an uncertainty for the neglect of quark-line
disconnected diagrams are: Mϕ ¼ 1.023ð6Þ GeV and fϕ ¼ 0.238ð3Þ GeV in good agreement with experiment.
The results come from calculations in the HISQ formalism using gluon fields that include the effect of u,
d, s and c quarks in the sea with three lattice spacing values and mu=d values going down to the physical point
Neutral Current Production in MiniBooNE
This paper describes the analysis used to determine the neutral current
production in MiniBooNE in bins of momentum. Additionally, a
measurement of the relative coherent production of s is discussed. The
coherent production rate is found to be (19.5 1.1 (stat) 2.5 (sys))%
of the total exclusive neutral current production rate.Comment: Prepared for the Proceedings of Neutrino Interactions 200
NC pi0 Production in the MiniBooNE Antineutrino Data
The single largest background to future numubar to nuebar (numu to nue)
oscillation searches is neutral current pi0 production. MiniBooNE, which began
taking antineutrino data in January 2006, has the world's largest sample of
pi0's produced by antineutrinos in the 1 GeV energy range. These neutral pions
are primarily produced through the delta resonance but can also be created
through "coherent production." The latter process is the coherent sum of
glancing scatters of (anti)neutrinos off a neutron or proton, in which the
nucleus is kept intact but a pi0 is created. Current analysis of NC pi0
production in the MiniBooNE antineutrino data will be discussed.Comment: 4 pages, including 5 figures. Proceedings of the 5th International
Workshop on Neutrino-Nucleus Interactions in the Few-GeV Region (NuInt07),
Batavia, Illinois, 30 May - 3 Jun 200
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
- …