Rubin-LSST

Abstract:

This article reports a measurement of the production cross section of prompt isolated photon pairs in proton-antiproton collisions at √s=1.96TeV using the CDF II detector at the Fermilab Tevatron collider. The data correspond to an integrated luminosity of 5.36fb-1. The cross section is presented as a function of kinematic variables sensitive to the reaction mechanisms. The results are compared with three perturbative QCD calculations: (1) a leading-order parton shower Monte Carlo, (2) a fixed next-to-leading-order calculation and (3) a next-to-leading-order/next-to-next-to-leading-log resummed calculation. The comparisons show that, within their known limitations, all calculations predict the main features of the data, but no calculation adequately describes all aspects of the data. © 2011 American Physical Society.

Abstract:

A search for pair-production of first generation scalar leptoquarks is performed in the final state containing an electron, a neutrino, and at least two jets using proton-proton collision data at √s=7 TeV. The data were collected by the CMS detector at the LHC, corresponding to an integrated luminosity of 36 pb-1. The number of observed events is in good agreement with the predictions for standard model processes. Prior CMS results in the dielectron channel are combined with this electron+neutrino search. A 95% confidence level combined lower limit is set on the mass of a first generation scalar leptoquark at 339 GeV for β=0.5, where β is the branching fraction of the leptoquark to an electron and a quark. These results represent the most stringent direct limits to date for values of β greater than 0.05. © 2011 CERN.

Abstract:

We present the results of a gravitational lensing analysis of the bright z s = 2.957 submillimeter galaxy (SMG) HERMES found in the Herschel/SPIRE science demonstration phase data from the Herschel Multi-tiered Extragalactic Survey (HerMES) project. The high-resolution imaging available in optical and near-IR channels, along with CO emission obtained with the Plateau de Bure Interferometer, allows us to precisely estimate the intrinsic source extension and hence estimate the total lensing magnification to be μ = 10.9 ± 0.7. We measure the half-light radius R eff of the source in the rest-frame near-UV and V bands that characterize the unobscured light coming from stars and find R eff, * = [2.0 ± 0.1] kpc, in good agreement with recent studies on the SMG population. This lens model is also used to estimate the size of the gas distribution (Reff, gas = [1.1 ± 0.5] kpc) by mapping back in the source plane the CO (J = 5 → 4) transition line emission. The lens modeling yields a relatively large Einstein radius R Ein = 4.″10 ± 0″.02, corresponding to a deflector velocity dispersion of [483 ± 16] km s -1. This shows that HERMES is lensed by a galaxy group-size dark matter halo at redshift z l ∼ 0.6. The projected dark matter contribution largely dominates the mass budget within the Einstein radius with f dm(< R Ein) ∼ 80%. This fraction reduces to f dm(< R eff, G1 ≃ 4.5 kpc) ∼ 47% within the effective radius of the main deflecting galaxy of stellar mass M *, G1 = [8.5 ± 1.6] × 1011 M ⊙. At this smaller scale the dark matter fraction is consistent with results already found for massive lensing ellipticals at z ∼ 0.2 from the Sloan Lens ACS Survey. © 2011. The American Astronomical Society. All rights reserved.

Abstract:

This Letter reports a measurement of the cross section of prompt isolated photon pair production in pp̄ collisions at a total energy √s=1.96TeV using data of 5.36fb-1 integrated luminosity collected with the CDF II detector at the Fermilab Tevatron. The measured cross section, differential in basic kinematic variables, is compared with three perturbative QCD predictions, a leading order parton shower calculation and two next-to-leading order calculations. The next-to-leading order calculations reproduce most aspects of the data. By including photon radiation from quarks before and after hard scattering, the parton shower prediction becomes competitive with the next-to-leading order predictions.

Abstract:

We present a new model for the infrared emission of the high redshift hyperluminous infrared galaxy IRAS F10214+4724 which takes into account recent photometric data from Spitzer and Herschel that sample the peak of its spectral energy distribution. We first demonstrate that the combination of the AGN tapered disc and starburst models of Efstathiou and coworkers, while able to give an excellent fit to the average spectrum of type 2 AGN measured by Spitzer, fails to match the spectral energy distribution of IRAS F10214+4724. This is mainly due to the fact that the ν S ν distribution of the galaxy falls very steeply with increasing frequency (a characteristic of heavy absorption by dust) but shows a silicate feature in emission. We propose a model that assumes two components of emission: clouds that are associated with the narrow-line region and a highly obscured starburst. The emission from the clouds must suffer significantly stronger gravitational lensing compared to the emission from the torus to explain the observed spectral energy distribution. © 2012 International Astronomical Union.