17 research outputs found
Leading Two-loop corrections to the mass of Higgs boson in the High scale Dirac gaugino supersymmetry
Precision measurements of the Higgs mass have become a powerful constraint on
models of physics beyond the standard model. We revisit supersymmetric models
with Dirac gauginos and study the contributions to the Higgs mass. We calculate
the leading two-loop corrections to the SM-like Higgs mass by constructing a
series of EFTs and iteratively integrating out heavy particles. We then apply
these calculations to a variety of scenarios, including a simple Dirac gluino,
and split Dirac models of supersymmetry. We present the detailed formulae for
threshold corrections and compare with previous results, where available. In
general, the contributions are small, but the additional precision allows us to
make more concrete statements about the relevant scales in Dirac SUSY models.Comment: 27 pages, 9 figure
Vacuum stability and perturbativity of SU(3) scalars
We calculate the vacuum stability conditions and renormalisation group equations for the extensions of standard model with a higher colour multiplet scalar up to the representation 1 5 0 that leaves the strong interaction asymptotically free. In order to find the vacuum stability conditions, we calculate the orbit spaces for the self-couplings of the higher multiplets, which for the representations 1 5 and 1 5 0 of SU(3)(c) are highly complicated. However, if the scalar potential is linear in orbit space variables, it is sufficient to know the convex hull of the orbit space. Knowledge of the orbit spaces also facilitates the minimisation of the potentials. In contrast to the self-couplings of other multiplets, we find that the scalar quartic couplings of the representations 3 and 8 walk rather than run, remaining nearly constant and perturbative over a vast energy range. We describe the conditions for walking couplings using a schematic model. With these technical results at hand we revise earlier results of generation of new scales with large SU(3) c scalar multiplets. Our results are easily extendable to models of new physics with additional SU(3) or SU(N) gauge symmetries.Peer reviewe
PyR@TE 2: A Python tool for computing RGEs at two-loop
26 pagesInternational audienceRenormalization group equations are an essential tool for the description of theories accross different energy scales. Even though their expressions at two-loop for an arbitrary gauge field theory have been known for more than thirty years, deriving the full set of equations for a given model by hand is very challenging and prone to errors. To tackle this issue, we have introduced in [1] a Python tool called PyR@TE; Python Renormalization group equations @ Two-loop for Everyone. With PyR@TE, it is easy to implement a given Lagrangian and derive the complete set of two-loop RGEs for all the parameters of the theory. In this paper, we present the new version of this code, PyR@TE 2, which brings many new features and in particular it incorporates kinetic mixing when several gauge groups are involved. In addition, the group theory part has been greatly improved as we introduced a new Python module dubbed PyLie that deals with all the group theoretical aspects required for the calculation of the RGEs as well as providing very useful model building capabilities. This allows the use of any irreducible representation of the , and groups. % Furthermore, it is now possible to implement terms in the Lagrangian involving fields which can be contracted into gauge singlets in more than one way. As a byproduct, results for a popular model (SM+complex triplet) for which, to our knowledge, the complete set of two-loop RGEs has not been calculated before are presented in this paper. Finally, the two-loop RGEs for the anomalous dimension of the scalar and fermion fields have been implemented as well. It is now possible to export the coupled system of beta functions into a numerical C++ function, leading to a consequent speed up in solving them
PyR@TE 2: A Python tool for computing RGEs at two-loop.
Renormalization group equations are an essential tool for the description of theories accross different energy scales. Even though their expressions at two-loop for an arbitrary gauge field theory have been known for more than thirty years, deriving the full set of equations for a given model by hand is very challenging and prone to errors. To tackle this issue, we have introduced in Lyonnet et al., (2014) a Python tool called PyR@TE; Python Renormalization group equations @ Two-loop for Everyone . With PyR@TE, it is easy to implement a given Lagrangian and derive the complete set of two-loop RGEs for all the parameters of the theory. In this paper, we present the new version of this code, PyR@TE 2, which brings many new features and in particular it incorporates kinetic mixing when several U(1) gauge groups are involved. In addition, the group theory part has been greatly improved as we introduced a new Python module dubbed PyLie that deals with all the group theoretical aspects required for the calculation of the RGEs as well as providing very useful model building capabilities. This allows the use of any irreducible representation of the SU(n), SO(2n) and SO(2n + 1) groups. Furthermore, it is now possible to implement terms in the Lagrangian involving fields which can be contracted into gauge singlets in more than one way. As a byproduct, results for a popular model (SM+complex triplet) for which, to our knowledge, the complete set of two-loop RGEs has not been calculated before are presented in this paper. Finally, the two-loop RGEs for the anomalous dimension of the scalar and fermion fields have been implemented as well. It is now possible to export the coupled system of beta functions into a numerical C++ function, leading to a consequent speed up in solving them
How robust are particle physics predictions in asymptotic safety?
The framework of trans-Planckian asymptotic safety has been shown to generate
phenomenological predictions in the Standard Model and in some of its simple
new physics extensions. A heuristic approach is often adopted, which bypasses
the functional renormalization group by relying on a parametric description of
quantum gravity with universal coefficients that are eventually obtained from
low-energy observations. Within this approach, a few simplifying approximations
are typically introduced, including the computation of matter renormalization
group equations at 1~loop, an arbitrary definition of the position of the
Planck scale at GeV, and an instantaneous decoupling of gravitational
interactions below the Planck scale. In this work we systematically
investigate, both analytically and numerically, the impact of dropping each of
those approximations on the predictions for certain particle physics scenarios.
In particular we study two extensions of the Standard Model, the gauged
model and the leptoquark model, for which we determine a set of
irrelevant gauge and Yukawa couplings. In each model, we present numerical and
analytical estimates of the uncertainties associated with the predictions from
asymptotic safety.Comment: 35 pages, 6 figures, 2 table