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MICONI Florian

Dernière mise à jour mardi 18 juin 2013, par Alain GOASDUFF

MICONI Florian

Institut Pluridisciplinaire Hubert Curien - IPHC

Département de Recherche Subatomique – DRS
Groupe Dø

Centre National de la Recherche Scientifique - CNRS
UMR 7178 CNRS/Université De Strasbourg - UDS

23 rue du loess, 67037 Strasbourg cedex 2, France

Contact : Florian MICONI

Titre de la thèse : Recherche d’un boson de Higgs standard de masse inférieure à 140 GeV/c2 avec l’expérience DØ au Tevatron.

Période : 2009-2012

Encadrant(s) : Isabelle RIPP-BAUDOT

Abstract

The standard model of the particle physics is based on the notion of local gauge invariance. It is a very successful theory but it comes with a major flaw, even though local gauge invariance is a very elegant way to introduce interaction between fermions, it predicts a null mass for the corresponding bosons. And yet, mass of the electroweak bosons W+/- and Z has been measured non-null at CERN in 1983. Higgs boson has been introduce to explain these masses as an interaction with the Higgs field, but it’s still unobserved by any experiment.

Below 140 GeV/c2 the Higgs boson decays mainly in two b quarks. Finding this final state is very difficult in an hadronic environment because of the overwhelming amount of background containing b-jets. Thus the most sensitive channel is the production of a Higgs boson in association with a W boson. The decay of the W boson ( lepton + neutrino ) allow us to drastically reduce the hadronic background.

Higgs production being extremely rare, we have to develop sophisticated techniques to improve the signal sensitivity such as b-jet identification and multivariate analysis (mainly neural networks and boosted decision trees).

This work focused on :

  • The development of a dedicated multivariate analysis to reduce the W(Z)+bb background, irreducible by the standard b-tagging method.
  • The development of an algorithm to recover a part of the radiation from the Higgs in the 3 jets channel, improving the reconstruction of its mass.

And various studies on b-tagging (comparison of the b-tagging efficiency vs time and luminosity) and on the overall analysis (comparison of previous set of data vs new one, adding new reweighting and corresponding systematics uncertainties).

In the end, statistical approach allow us to set an upper limit on the ratio between the observed (resp. expected) Higgs production and its theoretical cross section. The results obtained in the WH channel with 5.3 fb-1 at Dø is 4.8 (resp. 4.5) for a 115 GeV/c2 Higgs boson.
Key words : Higgs, D0, Tevatron, multivariate analysis, neural network, decision tree, b-tagging.

Keywords : Particle physics, Higgs, D0, Tevatron, b-tagging, multivariate analysis, neural network, decision tree.

Publications / Communications

  • « Jet Energy Resolution  »
    F. Miconi, Dø France meeting , LPNHE, Paris, May 30-31 2011
  • « Experimental aspect of low mass Higgs search at D0 »
    F. Miconi
    Lake Louise Winter Institute, Lake Louise, Canada (Alberta), February 14-20, 2011
  • « Tests of IIb-3 Dataset (WH electron channel) »
    F. Miconi, Dø France meeting , IPN, Lyon, May 3-4 2010
  • « La physique des particules auprès des collisioneurs »
    D. Bodin, C. Ferro, M. Karim, A. Maire, F. Miconi,
    IPHC PhD Student Day, Strasbourg, France, February 12, 2010
  • « Implémentation des variables du discriminant Vbb/Hbb dans l’analyse WH »
    F. Miconi, Réunion Dø France, LAL, Orsay, 26-27 Novembre 2009