25 research outputs found
Top quarks as a probe for heavy new physics
The heaviest fermion is expected to couple strongly to new physics and
appears therefore as a natural probe in many BSM scenarios. Moreover, top
physics has now entered in a precision era thanks to the huge amount of top
quarks produced at hadron colliders, advanced experimental methods and accurate
theoretical predictions. In this talk, we will used effective field theory to
search for heavy new physics in a model independent way. This method can also
be used to quantify the room left for new physics if no deviation from the SM
is found.Comment: To appear in the proceedings XXII. International Workshop on Deep
Inelastic Scattering and Related Subjects (DIS 2014), 28 April - 2 May 2014,
Warsaw, Polan
New physics in top decay
After a short introduction to effective field theories, most of their
features are illustrated using the top decay. The effects of heavy new physics
on the top decay are computed and the constraints on the coefficients of the
dimension-six operators are derived from the available measurements.Comment: 5 pages, 3 figures, Proceedings for Top201
Tests of top compositeness at hadron colliders
Top pair production can be used to probe composite top models. Associated with 4-top and t¯tb¯b productions, it can be used to distinguish different hypotheses
Can New Physics hide inside the proton?
Modern global analyses of the structure of the proton include collider
measurements which probe energies well above the electroweak scale. While these
provide powerful constraints on the parton distribution functions (PDFs), they
are also sensitive to beyond the Standard Model (BSM) dynamics if these affect
the fitted distributions. Here we present a first simultaneous determination of
the PDFs and BSM effects from deep-inelastic structure function data by means
of the NNPDF framework. We consider representative four-fermion operators from
the SM Effective Field Theory (SMEFT), quantify to which extent their effects
modify the fitted PDFs, and assess how the resulting bounds on the SMEFT
degrees of freedom are modified. Our results demonstrate how BSM effects that
might otherwise be reabsorbed into the PDFs can be systematically disentangled
New developments in FeynRules
The program FeynRules is a Mathematica package developed to facilitate the
implementation of new physics theories into high-energy physics tools. Starting
from a minimal set of information such as the model gauge symmetries, its
particle content, parameters and Lagrangian, FeynRules provides all necessary
routines to extract automatically from the Lagrangian (that can also be
computed semi-automatically for supersymmetric theories) the associated Feynman
rules. These can be further exported to several Monte Carlo event generators
through dedicated interfaces, as well as translated into a Python library,
under the so-called UFO model format, agnostic of the model complexity,
especially in terms of Lorentz and/or color structures appearing in the
vertices or of number of external legs. In this work, we briefly report on the
most recent new features that have been added to FeynRules, including full
support for spin-3/2 fermions, a new module allowing for the automated
diagonalization of the particle spectrum and a new set of routines dedicated to
decay width calculations.Comment: 6 pages. Contribution to the 15th International Workshop on advanced
computing and analysis techniques (ACAT 2013), 16-21 May, Beijing, Chin
New Physics in Double Higgs Production at Future Colliders
We study the effects of new physics in double Higgs production at future colliders. In the Standard Model the chiral limit () plays an
important role for this process, being responsible for the smallness of the
tree-level diagrams with respect to the 1-loop contributions. In our work, we
consider the possibility of an enhancement due to the contribution of Standard
Model dimension-six effective operators. We show that there are only two
relevant operators for this process that are not yet (strongly) constrained by
other data. We perform a sensitivity study on the operator coefficients for
several benchmark values of energy and integrated luminosity related to the
proposed linear colliders such as CLIC, ILC and FCC-ee and we derive expected
95% CL limits for each benchmark scenario.Comment: 17 pages, 8 figures, 1 table. New references adde