scholarly journals Towards Higgs masses and decay widths satisfying the symmetries in the (N)MSSM

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Florian Domingo ◽  
Sebastian Paßehr
Keyword(s):  
Higgs Sector ◽  
Higher Order ◽  
Loop Order ◽  
Gauge Dependence ◽  
Higher Order Terms ◽  
Gauge Fixing ◽  
Intuitive Concept ◽  
Definition Of ◽  
Higher Order Corrections ◽  
Extended Higgs Sector

AbstractIn models with an extended Higgs sector, such as the (N)MSSM, scalar states mix with one another. Yet, the concept of Higgs mixing is problematic at the radiative level, since it introduces both a scheme and a gauge dependence. In particular, the definition of Higgs masses and decay amplitudes can be impaired by the presence of gauge-violating pieces of higher order. We discuss in depth the origin and magnitude of such effects and consider two strategies that minimize the dependence on the gauge-fixing parameter and field-renormalization of one-loop order in the definition of the mass and decay observables, both in degenerate and non-degenerate scenarios. In addition, the intuitive concept of mixing and the simplicity of its definition in terms of two-point diagrams can make it tempting to include higher-order corrections on this side of the calculation, irrespectively of the order achieved in vertex diagrams. Using the global $$SU(2)_{\mathrm{L}}$$ S U ( 2 ) L -symmetry in the decoupling limit, we show that no improvement can be expected from such an approach at the level of the Higgs decays, but that, on the contrary, the higher-order terms may lead to numerically large spurious effects.

scholarly journals Two-loop $$ \mathcal{O} $$((αt + αλ + ακ)2) corrections to the Higgs boson masses in the CP-violating NMSSM

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Thi Nhung Dao ◽  
Martin Gabelmann ◽  
Margarete Mühlleitner ◽  
Heidi Rzehak
Keyword(s):  
Higgs Boson ◽  
Higgs Mass ◽  
Goldstone Boson ◽  
Higgs Sector ◽  
Momentum Dependence ◽  
Loop Order ◽  
Fortran Code ◽  
Higher Order Corrections ◽  
Infrared Divergences ◽  
The Impact

Abstract We present our computation of the $$ \mathcal{O} $$ O ((αt + αλ + ακ)2) two-loop corrections to the Higgs boson masses of the CP-violating Next-to-Minimal Supersymmetric Standard Model (NMSSM) using the Feynman-diagrammatic approach in the gaugeless limit at vanishing external momentum. We choose a mixed $$ \overline{\mathrm{DR}} $$ DR ¯ -on-shell (OS) renormalisation scheme for the Higgs sector and apply both $$ \overline{\mathrm{DR}} $$ DR ¯ and OS renormalisation in the top/stop sector. For the treatment of the infrared divergences we apply and compare three different regularisation methods: the introduction of a regulator mass, the application of a small momentum expansion, and the inclusion of the full momentum dependence. Our new corrections have been implemented in the Fortran code NMSSMCALC that computes the Higgs mass spectrum of the CP-conserving and CP-violating NMSSM as well as the Higgs boson decays including the state-of-the-art higher-order corrections. Our numerical analysis shows that the newly computed corrections increase with rising λ and κ, remaining overall below about 3% compared to our previously computed $$ \mathcal{O} $$ O (αt(αt + αs)) corrections, in the region compatible with perturbativity below the GUT scale. The renormalisation scheme and scale dependence is of typical two-loop order. The impact of the CP-violating phases in the new corrections is small. We furthermore show that the Goldstone Boson Catastrophe due to the infrared divergences can be treated in a numerically efficient way by introducing a regulator mass that approximates the momentum-dependent results best for squared mass values in the permille range of the squared renormalisation scale. Our results mark another step forward in the program of increasing the precision in the NMSSM Higgs boson observables.

scholarly journals STATUS OF HIGHER-ORDER CORRECTIONS IN THE STANDARD ELECTROWEAK THEORY

1995 ◽  
Vol 10 (04) ◽  
pp. 443-464 ◽  
Author(s):  
BERND A. KNIEHL
Keyword(s):  
Standard Model ◽  
Higgs Sector ◽  
Higher Order ◽  
Threshold Effects ◽  
Electroweak Theory ◽  
Radiative Corrections ◽  
Gauge Sector ◽  
The Standard Model ◽  
Text Mode ◽  
Higher Order Corrections

We review recent theoretical progress in the computation of radiative corrections beyond one loop within the standard model of electroweak interactions, in both the gauge and Higgs sectors. In the gauge sector, we discuss universal corrections of [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], and those due to virtual [Formula: see text]-threshold effects, as well as specific corrections to [Formula: see text] of [Formula: see text], [Formula: see text] and [Formula: see text] including finite-mb effects. We also present an update of the hadronic contributions to Δα. Theoretical uncertainties, other than those due to the lack of knowledge of MH and mt, are estimated. In the Higgs sector, we report on the [Formula: see text] corrections to [Formula: see text] including those which are specific for the [Formula: see text] mode, the [Formula: see text] corrections to [Formula: see text] including the finite-mq terms, and the [Formula: see text] corrections to Γ(H → gg).

scholarly journals SOFT BREAKING OF BRST SYMMETRY AND GAUGE DEPENDENCE

2012 ◽  
Vol 27 (13) ◽  
pp. 1250067 ◽  
Author(s):  
P. M. LAVROV ◽  
O. V. RADCHENKO ◽  
A. A. RESHETNYAK
Keyword(s):  
Green's Functions ◽  
Gauge Theories ◽  
Green’S Functions ◽  
Brst Symmetry ◽  
Gauge Dependence ◽  
Gauge Fixing ◽  
Definition Of ◽  
Continue Investigation ◽  
Arbitrary Gauge ◽  
General Gauge

We continue investigation of soft breaking of BRST symmetry in the Batalin–Vilkovisky (BV) formalism beyond regularizations like dimensional ones used in our previous paper [JHEP 1110, 043 (2011)]. We generalize a definition of soft breaking of BRST symmetry valid for general gauge theories and arbitrary gauge fixing. The gauge dependence of generating functionals of Green's functions is investigated. It is proved that such introduction of a soft breaking of BRST symmetry into gauge theories leads to inconsistency of the conventional BV formalism.

scholarly journals Hamiltonian reduction of Vlasov–Maxwell to a dark slow manifold

2021 ◽  
Vol 87 (3) ◽  
Author(s):  
George Miloshevich ◽  
Joshua W. Burby
Keyword(s):  
Hamiltonian Structure ◽  
Slow Manifold ◽  
Higher Order ◽  
Hamiltonian Reduction ◽  
Time Interval ◽  
Maxwell System ◽  
Infinite Dimensional ◽  
Light Waves ◽  
Higher Order Terms ◽  
Higher Order Corrections

We show that non-relativistic scaling of the collisionless Vlasov–Maxwell system implies the existence of a formal invariant slow manifold in the infinite-dimensional Vlasov–Maxwell phase space. Vlasov–Maxwell dynamics restricted to the slow manifold recovers the Vlasov–Poisson and Vlasov–Darwin models as low-order approximations, and provides higher-order corrections to the Vlasov–Darwin model more generally. The slow manifold may be interpreted to all orders in perturbation theory as a collection of formal Vlasov–Maxwell solutions that do not excite light waves, and are therefore ‘dark’. We provide a heuristic lower bound for the time interval over which Vlasov–Maxwell solutions initialized optimally near the slow manifold remain dark. We also show how the dynamics on the slow manifold naturally inherits a Hamiltonian structure from the underlying system. After expressing this structure in a simple form, we use it to identify a manifestly Hamiltonian correction to the Vlasov–Darwin model. The derivation of higher-order terms is reduced to computing the corrections of the system Hamiltonian restricted to the slow manifold.

scholarly journals 4D Einstein-Lovelock Black Holes: Hierarchy of Orders in Curvature

2020 ◽  
Author(s):  
Roman A. Konoplya ◽  
Alexander Zhidenko
Keyword(s):  
Black Holes ◽  
Black Hole Solution ◽  
Higher Order ◽  
Coupling Constants ◽  
Dynamical Instability ◽  
Coupling Constant ◽  
Threshold Values ◽  
Higher Order Terms ◽  
Higher Order Corrections ◽  
Bonnet Term

The Einstein-Lovelock theory contains an infinite series of corrections to the Einstein term with an increasing power of the curvature. It is well-known that for large black holes the lowest (Gauss-Bonnet) term is the dominant one, while for smaller black holes higher curvature corrections become important. We will show that if one is limited by positive values of the coupling constants, then the dynamical instability of black holes serves as an effective cut-off of influence of higher curvature corrections in the 4D Einstein-Lovelock approach: the higher is the order of the Lovelock term, the smaller is the maximal value of the coupling constant allowing for stability, so that effectively only a first few orders can deform the observable values seemingly. For negative values of coupling constants this is not so, and, despite some suppression of higher order terms also occurs due to the decreasing threshold values of the coupling constant, this does not lead to an noticeable opportunity to neglect higher order corrections. In the case a lot of orders of Lovelock theory are taken into account, so that the black-hole solution depends on a great number of coupling constants, we propose a compact description of it in terms of only two or three parameters encoding all the observable values.

scholarly journals A critical look at the electroweak phase transition

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Andreas Ekstedt ◽  
Johan Löfgren
Keyword(s):  
Phase Transition ◽  
Generic Model ◽  
Electroweak Symmetry ◽  
Electroweak Phase Transition ◽  
Gauge Dependence ◽  
Perturbative Methods ◽  
The Standard Model ◽  
Gauge Fixing ◽  
Infrared Divergences ◽  
General Gauge

Abstract The electroweak phase transition broke the electroweak symmetry. Perturbative methods used to calculate observables related to this phase transition suffer from severe problems such as gauge dependence, infrared divergences, and a breakdown of perturbation theory. In this paper we develop robust perturbative tools for dealing with phase transitions. We argue that gauge and infrared problems are absent in a consistent power-counting. We calculate the finite temperature effective potential to two loops for general gauge-fixing parameters in a generic model. We demonstrate gauge invariance, and perform numerical calculations for the Standard Model in Fermi gauge.

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