Article

Next-to-Leading Order Cross Sections for New Heavy Fermion Production at Hadron Colliders

Physical Review D (Impact Factor: 4.86). 09/2009; 81(3). DOI: 10.1103/PhysRevD.81.035006
Source: arXiv

ABSTRACT We evaluate the cross sections for new heavy fermion production at three
Large Hadron Collider energies accurate to next-to-leading order in
perturbative quantum chromodynamics. We treat the cases of pair production of
heavy quarks via strong interactions, single heavy quark production via
electroweak interactions, and the production of heavy leptons. Theoretical
uncertainties associated with the choice of the renormalization scale and the
parton distribution functions are specified. We derive a simple and useful
parameterization of our results which should facilitate phenomenological
studies of new physics models that predict new heavy quarks and/or leptons.

0 Followers
 · 
78 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The results of a search for pair production of a heavy, top-like quark, t', in the decay mode (t' anti-t') to (b anti-W anti-b W) to (b anti-lepton neutrino anti-b lepton anti-neutrino) are presented. The search is performed with a data sample corresponding to an integrated luminosity of 5.0 inverse femtobarns in pp collisions at a center-of-mass energy of 7 TeV, collected by the CMS experiment at the LHC. The observed number of events agrees with the expectation from standard model processes, and no evidence of t' anti-t' production is found. Upper limits on the production cross section as a function of t' mass are presented, and t' masses below 557 GeV/c^2 are excluded at the 95% confidence level.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We study a model independent extension to the Standard Model with an addi- tional real scalar triplet, {\Sigma}, and a single vector-like quark, T . This class of models appear naturally in extensions of the Littlest Higgs model that incorporate dark matter without the need of T -parity. We assume that the triplet does not develop a vacuum expectation value and that all dimension five operators coupling the triplet to Standard Model fields and the vector-like quarks are parametrized by the scale {\Lambda} at which we expect new physics to arise. We introduce new non-renormalizable interactions between the new scalar sector and fermion sector that allow mixing between the Standard Model third generation up-type quark and the vector-like quark in a way that leads to the cancellation of the leading quadratic divergences to the one-loop corrections to the mass of the Higgs boson. Within this framework, new de- cay modes of the vector-like quark to the real scalar triplet and SM particles arise and bring forth an opportunity to probe this model with existing and future LHC data. We contrast constraints from direct colliders searches with low energy precision measurements and find that heavy vector-like top quarks with a mass as low as 650 GeV are consistent with current experimental constraints in models where new physics arises at scales below 2 TeV. Lastly, we discuss a model where new decay modes of the heavy vector-like top quarks are possible within an extension of the Littlest Higgs model.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Prospects for discovery of the standard model Higgs boson are examined at center-of-mass energies of 7 and 10 TeV at the CERN Large Hadron Collider. We perform a simulation of the signal and principal backgrounds for Higgs boson production and decay in the W+W- dilepton mode, finding good agreement with the ATLAS and CMS collaboration estimates of signal significance at 14 TeV for Higgs boson masses near mH=160 GeV. At the lower energy of 7 TeV, using the same analysis cuts as these collaborations, we compute expected signal sensitivities of about 2 standard deviations (σ’s) at mH=160 GeV in the ATLAS case, and about 3.6σ in the CMS case for 1 fb-1 of integrated luminosity. Integrated luminosities of 8 fb-1 and 3 fb-1 are needed in the ATLAS case at 7 and 10 TeV, respectively, for 5σ level discovery. In the CMS case, the numbers are 2 fb-1 and 1 fb-1 at 7 and 10 TeV. Our different stated expectations for the two experiments arise from the more restrictive analysis cuts in the CMS case and from the different event samples in the two cases. Recast as exclusion limits, our results show that with 1 fb-1 of integrated luminosity at 7 TeV, the LHC may be able to exclude mH values in the range 160 to 180 GeV provided no signal is seen.
    Physical review D: Particles and fields 09/2010; 82(5). DOI:10.1103/PhysRevD.82.053003 · 4.86 Impact Factor

Full-text (2 Sources)

Download
37 Downloads
Available from
May 22, 2014