Model Independent Extra-dimension signatures with ATLAS

The generic missing transverse energy signals at LHC for theories having large extra dimensions are discussed. Final states of jets plus missing energy and photons plus missing energy are simulated in the ATLAS detector. The discovery limit of LHC and the methods to determine the parameters of the underlying model are discussed.Comment: 29 page

Prospects for b-tagging in ATLAS and tracking commissioning results with cosmic rays

The ability to identify jets containing B hadrons is important for the high-pT physics program of a general-purpose experiment at the LHC such as ATLAS. This capability relies on the very accurate measurements of the parameters of charged tracks provided by the ATLAS Inner Detector. Using millions of cosmic-ray tracks collected during the automn 2008, the ATLAS Inner Detector has been aligned and its tracking performance assessed. Some of the very encouraging results which have been obtained and are relevant for b-tagging are discussed, notably the current level of alignment of the detector and the resolution on the transverse impact parameter of tracks. The various b-tagging algorithms are then described, and their anticipated performance discussed in the light of the cosmic-ray data results. Finaly,the expected accuracy with which the b-tagging performance will be measured in data is mentioned

Signals of Models with Large Extra Dimensions in ATLAS

The generic missing transverse energy signals at LHC for theories having large extra dimensions are discussed. Final states of jets plus missing energy and photons plus missing energy are simulated in the ATLAS detector. The discovery limit of LHC and the methods to determine the parameters of the underlying model are discussed

Spectra of Field Fluctuations in Braneworld Models with Broken Bulk Lorentz Invariance

We investigate five-dimensional braneworld setups with broken Lorentz invariance continuing the developments of our previous paper (arXiv:0712.1136), where a family of static self-tuning braneworld solutions was found. We show that several known braneworld models can be embedded into this family. Then we give a qualitative analysis of spectra of field fluctuations in backgrounds with broken Lorentz invariance. We also elaborate on one particular model and study spectra of scalar and spinor fields in it. It turns out that the spectra we have found possess very peculiar and unexpected properties.Comment: 30 pages, 8 figures, minor corrections, references added, note adde

Search for the radion using the ATLAS detector

The possibility of observing the radion using the ATLAS detector at LHC is investigated. Studies on searches for the Standard Model Higgs with the ATLAS detector are re-interpreted to obtain limits on radion decay to gamma-gamma and ZZ(*). The observability of radion decays into Higgs pairs, which subsequently decay into gamma-gamma+b-bbar or tau-tau+b-bbar is then estimate

b-tagging with ATLAS

The ability to identify jets containing b-hadrons is important for the high-pT physics program of a general-purpose experiment at the LHC such as ATLAS. This is in particular useful to select very pure top samples, to search and/or study Standard Model or supersymmetric Higgs bosons which couple preferably to heavy objects or are produced in association with heavy quarks, to veto the large dominant ttbar background for several physics channels and finally to search for new physics: SUSY decay chains, heavy gauge bosons, etc. After a review of the algorithms used to identify b-jets, their anticipated performance is discussed as well as the impact of various critical ingredients such as the residual misalignments in the tracker. The prospects to measure the b-tagging performance in the first few hundreds pb-1 of data with di-jet events and ttbar events are then discussed. Finally three different use cases are discussed: the top mass measurement, the search for a low-mass Higgs boson produced in association with a top quark pair and decaying to bbbar, and the specific challenges of tagging very high-pT (TeV) jets for exotics searches

Prospects for b-tagging with ATLAS and tracking results with cosmics

b-tagging is a important tool for a large fraction of the physics program of ATLAS. In addition it is specially important for rediscovering the top quark at a 7 TeV center-of-mass energy, where the signal over background is less favourable than at higher energies. The ATLAS Inner Detector is working extremely well and some results obtained with cosmic muons are presented, showing that most parameters are already very close to the nominal expected values. In addition the cosmic muons were used to align the detector with a relatively good accuray. Therefore it is not unrealistic to start commissioning the b-tagging capability with the first ATLAS data. The tagging algorithms which will be used in early data are then described, as well as their expected performance. Finally the measurement of the b-tagging performance directly in data is discussed

Unsupervised Polygonal Reconstruction of Noisy Contours by a Discrete Irregular Approach

International audienceIn this paper, we present an original algorithm to build a polygonal reconstruction of noisy digital contours. For this purpose, we first improve an algorithm devoted to the vectorization of discrete irregular isothetic objects. Afterwards we propose to use it to define a reconstruction process of noisy digital contours. More precisely, we use a local noise detector, introduced by Kerautret and Lachaud in IWCIA 2009, that builds a multi-scale representation of the digital contour, which is composed of pixels of various size depending of the local amount of noise. Finally, we compare our approach with previous works, by con- sidering the Hausdorff distance and the error on tangent orientations of the computed line segments to the original perfect contour. Thanks to both synthetic and real noisy objects, we show that our approach has interesting performance, and could be applied in document analysis systems

Prospects for probing the gluon density in protons using heavy quarkonium hadroproduction

We examine carefully bottomonia hadroproduction in proton colliders, especially focusing on the LHC, as a way of probing the gluon density in protons. To this end we develop some previous work, getting quantitative predictions and concluding that our proposal can be useful to perform consistency checks of the parameterization sets of different parton distribution functions.Comment: LaTeX, 14 pages, 6 EPS figure

Vector boson production in association with KK modes of the ADD model to NLO in QCD at LHC

Next-to-leading order QCD corrections to the associated production of vector boson (Z/W) with the the Kaluza-Klein modes of the graviton in large extra dimensional model at the LHC, are presented. We have obtained various kinematic distributions using a Monte Carlo code which is based on the two cut off phase space slicing method that handles soft and collinear singularities appearing at NLO level. We estimate the impact of the QCD corrections on various observables and find that they are significant. We also show the reduction in factorization scale uncertainty when QCD corrections are included.Comment: 12 pages, 5 figure