Rubin-LSST

Abstract:

We propose a new method for the extraction cosmological parameters using the baryon acoustic oscillation (BAO) scale as a standard ruler in deep galaxy surveys with photometric determination of redshifts. The method consists in a simple empirical parametric fit to the angular two-point correlation function ω(θ). It is parametrized as a power law to describe the continuum and as a Gaussian to describe the BAO bump. The location of the Gaussian is used as the basis for the measurement of the sound horizon scale. This method, although simple, actually provides a robust estimation, since the inclusion of the power law and the use of the Gaussian remove the shifts which affect the local maximum. We discuss the effects of projection bias, non-linearities, redshift space distortions and photo-z precision and apply our method to a mock catalogue of the Dark Energy Survey, built upon a large N-body simulation provided by the MICE collaboration. We discuss the main systematic errors associated with our method and show that they are dominated by the photo-z uncertainty.

Abstract:

We report on a search for new particles in the diphoton channel using a data sample of pp̄ collisions at √s=1.96TeV collected by the CDF II detector at the Fermilab Tevatron, with an integrated luminosity of 5.4fb⊃-1. The diphoton invariant mass spectrum of the data agrees well with the standard model expectation. We set upper limits on the production cross section times branching ratio for the Randall-Sundrum graviton, as a function of diphoton mass. We subsequently derive lower limits on the graviton mass of 459GeV/c2 and 963GeV/c2, at the 95% confidence level, for coupling parameters (k/M̄Pl) of 0.01 and 0.1, respectively. © 2011 American Physical Society.

Abstract:

The first measurement of the cross section for top-quark pair production in pp collisions at the Large Hadron Collider at center-of-mass energy s=7 TeV has been performed using a data sample corresponding to an integrated luminosity of 3.1±0.3 pb-1 recorded by the CMS detector. This result utilizes the final state with two isolated, highly energetic charged leptons, large missing transverse energy, and two or more jets. Backgrounds from Drell-Yan and non-W/Z boson production are estimated from data. Eleven events are observed in the data with 2.1±1.0 events expected from background. The measured cross section is 194±72(stat.)±24(syst.)±21(lumi.) pb, consistent with next-to-leading order predictions. © 2010 CERN.

Abstract:

The results of the first search for long-lived gluinos produced in 7 TeV pp collisions at the CERN Large Hadron Collider are presented. The search looks for evidence of long-lived particles that stop in the CMS detector and decay in the quiescent periods between beam crossings. In a dataset with a peak instantaneous luminosity of 1×1032cm-2s-1, an integrated luminosity of 10pb-1, and a search interval corresponding to 62 hours of LHC operation, no significant excess above background was observed. Limits at the 95% confidence level on gluino pair production over 13 orders of magnitude of gluino lifetime are set. For a mass difference m g-mχ10>100GeV/c2, and assuming BR(g→gχ10)= 100%, mg<370GeV/c2 are excluded for lifetimes from 10μs to 1000 s. © 2010 The American Physical Society.