Cut locus and heat kernel at Grushin points of 2 dimensional almost Riemannian metrics

This article deals with 2d almost Riemannian structures, which are generalized Riemannian structures on manifolds of dimension 2. Such sub-Riemannian structures can be locally defined by a pair of vector fields (X,Y), playing the role of orthonormal frame, that may become colinear on some subset. We denote D = span(X,Y). After a short introduction, I first give a description of the local cut and conjugate loci at a Grushin point q (where Dq has dimension 1 and Dq = TqM) that makes appear that the cut locus may have an angle at q. In a second time I describe the local cut and conjugate loci at a Riemannian point x in a neighborhood of a Grushin point q. Finally, applying results of [6], I give the asymptotics in small time of the heat kernel p_t(x,y) for y in the same neighborhood of q

Electron/Photon identification in ATLAS and CMS

Recent studies in ATLAS and CMS experiments for the reconstruction and identification of electrons and photons using full Monte Carlo and testbeam data are reportedComment: Talk given at the Hadron Collider Physic Symposium 2006 (HCP2006), Durham, NC on behalf of ATLAS and CMS collaboration

Higgs search in H→\toZZ/WW decay channels with the CMS detector

A prospective analysis for the search of the Standard Model Higgs boson decaying in vector boson pairs is presented with the CMS experiment in the context of the initial luminosity at the CERN LHC pp collider. Monte Carlo data corresponding to an integrated luminosity of up to 1 fb$^{-1}$ are analysed and the expected significance for a Standard Model-like Higgs boson in these channels is established.Comment: 4 pages, 4 figures, proceedings of the Lake Louise Winter Institute 2009, 16th-21st February 2009, Alberta, Canad

A simple model to interpret the ultraviolet, optical and infrared SEDs of galaxies

We present a simple, largely empirical but physically motivated model, which is designed to interpret consistently multi-wavelength observations from large samples of galaxies in terms of physical parameters, such as star formation rate, stellar mass and dust content. Our model is both simple and versatile enough to allow the derivation of statistical constraints on the star formation histories and dust contents of large samples of galaxies using a wide range of ultraviolet, optical and infrared observations. We illustrate this by deriving median-likelihood estimates of a set of physical parameters describing the stellar and dust contents of local star-forming galaxies from the Spitzer Infrared Nearby Galaxy Sample (SINGS) and from a newly-matched sample of SDSS galaxies observed with GALEX, 2MASS, and IRAS. The model reproduces well the observed spectral energy distributions of these galaxies across the entire wavelength range from the far-ultraviolet to the far-infrared. We find important correlations between the physical parameters of galaxies which are useful to investigate the star formation activity and dust properties of galaxies. Our model can be straightforwardly applied to interpret observed ultraviolet-to-infrared spectral energy distributions (SEDs) from any galaxy sample.Comment: 4 pages, 3 figures, to appear in the Conference Proceedings of IAU Symposium No. 262: Stellar Populations - Planning for the Next Decade, G. Bruzual & S. Charlot ed

The K-band luminosity function at z=1: a powerful constraint on galaxy formation theory

There are two major approaches to modelling galaxy evolution. The traditional view is that the most massive galaxies were assembled early and have evolved with steeply declining star formation rates since a redshift of 2 or higher. According to hierarchical theories, massive galaxies were assembled much more recently from mergers of smaller subunits. Here we present a simple observational test designed to differentiate between the two. The observed K-band flux from a galaxy is a good measure of its stellar mass even at high redshift. It is probably only weakly affected by dust extinction. We compute the evolution of the observed K-band luminosity function for traditional, pure luminosity evolution (PLE) models and for hierarchical models. At z=0, both models can fit the observed local K-band luminosity function. By redshift 1, they differ greatly in the predicted abundance of bright galaxies. We calculate the redshift distributions of K-band selected galaxies and compare these with available data. We show that the number of K<19 galaxies with redshifts greater than 1 is well below the numbers predicted by the PLE models. In the Songaila et al (1994) redshift sample of 118 galaxies with 16<K<18, 33 galaxies are predicted to lie at z>1. Only 2 are observed. In the Cowie et al. (1996) redshift sample of 52 galaxies with 18<K<19, 28 galaxies are predicted to lie at at z>1. Only 5 are observed. Both these samples are more than 90% complete. We conclude that there is already strong evidence that the abundance of massive galaxies at z=1 is well below the local value. This is inconsistent with the traditional model, but similar to the expectations of hierarchical models.Comment: 13 pages, Latex, 4 figures included in text, submitted to MNRAS pink page

Twelve Ways to Build CMS Crossings from ROOT Files

The simulation of CMS raw data requires the random selection of one hundred and fifty pileup events from a very large set of files, to be superimposed in memory to the signal event. The use of ROOT I/O for that purpose is quite unusual: the events are not read sequentially but pseudo-randomly, they are not processed one by one in memory but by bunches, and they do not contain orthodox ROOT objects but many foreign objects and templates. In this context, we have compared the performance of ROOT containers versus the STL vectors, and the use of trees versus a direct storage of containers. The strategy with best performances is by far the one using clones within trees, but it stays hard to tune and very dependant on the exact use-case. The use of STL vectors could bring more easily similar performances in a future ROOT release.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 8 pages, LaTeX, 1 eps figures. PSN TUKT00

OVAL: the CMS Testing Robot

Oval is a testing tool which help developers to detect unexpected changes in the behavior of their software. It is able to automatically compile some test programs, to prepare on the fly the needed configuration files, to run the tests within a specified Unix environment, and finally to analyze the output and check expectations. Oval does not provide utility code to help writing the tests, therefore it is quite independant of the programming/scripting language of the software to be tested. It can be seen as a kind of robot which apply the tests and warn about any unexpected change in the output. Oval was developed by the LLR laboratory for the needs of the CMS experiment, and it is now recommended by the CERN LCG project.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 5 pages, LaTeX, 0 eps figures. PSN MOJT00