Improved unitarity constraints in Two-Higgs-Doublet-Models

Two-Higgs-Doublet-Models (THDMs) are among the simplest extensions of the standard model and are intensively studied in the literature. Using on-shell parameters such as the masses of the additional scalars as input, corresponds often to large quartic couplings in the underlying Lagrangian. Therefore, it is important to check if these couplings are for instance in agreement with perturbative unitarity. The common approach for doing this check is to consider the two-particle scattering matrix of scalars in the large centre-of-mass energy limit where only point interactions contribute. We show that this is not always a valid approximation: the full calculation including all tree-level contributions at finite energy can lead to much more stringent constraints. We show how the allowed regions in the parameter space are affected. In particular, the light Higgs window with a second Higgs below 125 GeV completely closes for large values of the $Z_2$ breaking parameter $|M_{12}|$. We also compare against the loop corrected constraints, which use also the large $\sqrt{s}$ approximation, and find that (effective) cubic couplings are often more important than radiative corrections.Comment: 8 pages, 6 figure

Dirac Gauginos and the 125 GeV Higgs

We investigate the mass, production and branching ratios of a 125 GeV Higgs in models with Dirac gaugino masses. We give a discussion of naturalness, and describe how deviations from the Standard Model in the key Higgs search channels can be simply obtained. We then perform parameter scans using a SARAH package upgrade, which produces SPheno code that calculates all relevant quantities, including electroweak precision and flavour constraint data, to a level of accuracy previously impossible for this class of models. We study three different variations on the minimal Dirac gaugino extension of the (N)MSSM.Comment: 32 pages, 9 figure

Supersymmetric and non-supersymmetric models without catastrophic Goldstone bosons

The calculation of the Higgs mass in general renormalisable field theories has been plagued by the so-called "Goldstone Boson Catastrophe", where light (would-be) Goldstone bosons give infra-red divergent loop integrals. In supersymmetric models, previous approaches included a workaround that ameliorated the problem for most, but not all, parameter space regions; while giving divergent results everywhere for non-supersymmetric models! We present an implementation of a general solution to the problem in the public code SARAH, along with new calculations of some necessary loop integrals and generic expressions. We discuss the validation of our code in the Standard Model, where we find remarkable agreement with the known results. We then show new applications in Split SUSY, the NMSSM, the Two-Higgs-Doublet Model, and the Georgi-Machacek model. In particular, we take some first steps to exploring where the habit of using tree-level mass relations in non-supersymmetric models breaks down, and show that the loop corrections usually become very large well before naive perturbativity bounds are reached.Comment: 45 pages, 12 figure

Minimal constrained superfields and the Fayet-Iliopoulos model

We show how the necessary constraints to project out all the components of a chiral superfield except for some scalar degrees of freedom originate from simple operators in the microscopic theory. This is in particular useful in constructing the simplest models of a goldstone boson/inflaton; or extracting the Standard Model Higgs doublet from a supersymmetric electroweak sector. We use the Fayet-Iliopoulos model as an example of the origin for the supersymmetry breaking. We consider the regime where both gauge symmetry and supersymmetry are spontaneously broken, leaving (in the decoupling limit) the goldstino as the only light mode in this sector. We show in three different ways, both in components and in superspace language, how the nilpotent goldstino superfield emerges. We then use it to write different effective operators and extract some of the consequences for the low energy spectrum.Comment: 17 pages. References added. Published versio

Matching renormalisable couplings: simple schemes and a plot

We discuss different choices that can be made when matching a general high-energy theory -- with the restriction that it should not contain heavy gauge bosons -- onto a general renormalisable effective field theory at one loop, with particular attention to the quartic scalar couplings and Yukawa couplings. This includes a generalisation of the counterterm scheme that was found to be useful in the case of high-scale/split supersymmetry, but we show the important differences when there are new heavy scalar fields in singlet or triplet representations of $SU(2)$. We also analytically compare our methods and choices with the approach of matching pole masses, proving the equivalence with one of our choices. We outline how to make the extraction of quartic couplings using pole masses more efficient, an approach that we hope will generalise beyond one loop. We give examples of the impact of different scheme choices in a toy model; we also discuss the MSSM and give the threshold corrections to the Higgs quartic coupling in Dirac gaugino models.Comment: 59 pages, 7 figures. v2: added some explanations. Matches published versio

Instanton induced Yukawa couplings from distant E3 and E(-1) instantons

We calculate non-perturbative contributions to Yukawa couplings on D3-branes at orbifold singularities due to E3 and fractional E(-1) instantons which do not intersect the visible sector branes. While distant E3 instantons on bulk cycles typically contribute to Yukawa couplings, we find that distant fractional E(-1) can also give rise to new Yukawa couplings. However, fractional E(-1) instantons only induce Yukawa couplings if they are located at a singularity which shares a collapsed homologous two-cycle with the singularity supporting the visible sector. The non-perturbative contributions to Yukawa couplings exhibit a different flavour structure than the tree-level Yukawa couplings and, as a result, they can be sources of flavour violation. This is particularly relevant for schemes of moduli stabilisation which rely on superpotential contributions from E3 instantons, such as KKLT or the Large Volume Scenario. As a byproduct of our analysis, we shed some new light on the properties of annulus diagrams with matter field insertions in stringy instanton calculus.Comment: 41 pages, 2 figures; v2: references adde

Higgs alignment from extended supersymmetry

We consider the effective type-II Two-Higgs doublet model originating from Dirac gaugino models with extended supersymmetry in the gauge sector, which is automatically aligned in the simplest realisations. We show that raising the scale at which the extended supersymmetry is manifest and including quantum corrections actually improves the alignment. Using an effective field theory approach including new threshold corrections and two-loop RGEs, plus two-loop corrections to the Higgs mass in the low-energy theory, we study the implications from the Higgs mass and other experimental constraints on the scale of superpartners. We contrast the results of the minimal Dirac gaugino model, where alignment is automatic, with the hMSSM and the MRSSM, where it is not, also providing an hMSSM-inspired analysis for the new models.Comment: 37 pages, 13 figures. References added. Published versio

The Higgs mass in the CP violating MSSM, NMSSM, and beyond

We discuss the automatised calculation of the Higgs mass in renormalisable supersymmetric models with complex parameters at the two-loop level. Our setup is based on the public codes SARAH and SPheno, which can now compute the two-loop corrections to masses of all neutral scalars in such theories. The generic ansatz for these calculations and the handling of the `Goldstone Boson catastrophe' is described. It is shown that we find perfect agreement with other existing two-loop calculations performed in the DR-bar scheme. We also use the functionality to derive results for the MSSM and NMSSM not available before: the Higgs mass in the constrained version of the complex MSSM, and the impact of CP phases in the two-loop corrections beyond order alpha-strong alpha-top for the scale invariant NMSSM are briefly analysed.Comment: 19 pages, 14 figure

On the two-loop corrections to the Higgs masses in the NMSSM

We discuss the impact of the two-loop corrections to the Higgs mass in the NMSSM beyond $O(\alpha_S(\alpha_b + \alpha_t))$. For this purpose we use the combination of the public tools SARAH and SPheno to include all contributions stemming from superpotential parameters. We show that the corrections in the case of a heavy singlet are often MSSM-like and reduce the predicted mass of the SM-like state by about 1 GeV as long as $\lambda$ is moderately large. For larger values of $\lambda$ the additional corrections can increase the SM-like Higgs mass. If a light singlet is present the additional corrections become more important even for smaller values of $\lambda$ and can even dominate the ones involving the strong interaction. In this context we point out that important effects are not reproduced quantitatively when only including $O((\alpha_b+\alpha_t+\alpha_\tau)^2)$ corrections known from the MSSM.Comment: 23 pages, 11 figure

Leading two-loop corrections to the Higgs boson masses in SUSY models with Dirac gauginos

We compute the two-loop O(as*at) corrections to the Higgs boson masses in supersymmetric extensions of the Standard Model with Dirac gaugino masses. We rely on the effective-potential technique, allow for both Dirac and Majorana mass terms for the gluinos, and compute the corrections in both the DRbar and on-shell renormalisation schemes. We give detailed results for the MDGSSM and the MRSSM, and simple approximate formulae valid in the decoupling limit for all currently-studied variants of supersymmetric models with Dirac gluinos. These results represent the first explicit two-loop calculation of Higgs boson masses in supersymmetric models beyond the MSSM and the NMSSM.Comment: 36 pages, 5 figures; v2: version published in JHE