Diboson production in the SMEFT from gluon fusion

We present the calculation of the contribtuions from the chromomagnetic and four-top-quark-operators within Standard Model Effective Field Theory (SMEFT) to Higgs boson pair production in gluon fusion, combined with QCD corrections that are at NLO with full mt-dependence for the leading operators. We study the effects of these operators on the total cross section and the invariant mass distribution of the Higgs-boson pair, at $$\sqrt{s}$$ = 13.6 TeV. These subleading operators are implemented in the generator ggHH_SMEFT, in the same Powheg-Box-V2 framework as the leading operators, such that their effects can be easily studied in a unified setup.

“…Note that the tails do not yet reach the energy range where, as predicted by the high energy expansion of the helicity amplitudes in ref. [104], the quadratic contribution takes over.…”

Section: Linear Versus Linear+quadratic Contributions From the Chromo...mentioning

confidence: 99%

Combining chromomagnetic and four-fermion operators with leading SMEFT operators for gg → hh at NLO QCD

Heinrich,

Lang

2024

SMEFT at NNLO+PS: Vh production

Gauld,

Haisch,

Schnell

2024

In the context of the Standard Model effective field theory (SMEFT) the next-to-next-to-leading (NNLO) QCD corrections to the Higgsstrahlungs (Vh) processes in hadronic collisions are calculated and matched to a parton shower (PS). NNLO+PS precision is achieved for the complete sets of SMEFT operators that describe the interactions between the Higgs and two vector bosons and the couplings of the Higgs, a W or a Z boson, and light fermions. A POWHEG-BOX implementation of the computed NNLO SMEFT corrections is provided that allows for a realistic exclusive description of Vh production at the level of hadronic events. This feature makes it an essential tool for future Higgs characterisation studies by the ATLAS and CMS collaborations. Utilising our new Monte Carlo code the numerical impact of NNLO+PS corrections on the kinematic distributions in pp → Zh → ℓ+ℓ−h production is explored, employing well-motivated SMEFT benchmark scenarios.

Aligned yet large dipoles: a SMEFT study

Bonnefoy,

Kley,

Liu

et al. 2024

We study a non-universal flavor scenario at the level of the Standard Model Effective Field Theory, according to which the matrix of Wilson coefficients cuW of an up-type electroweak quark dipole operator is aligned with the up-type Yukawa coupling. Such an alignment usually follows from the assumption of Minimal Flavor Violation (MFV), away from which we step by allowing the entries of cuW to be sizable along the first quark generations. A particular example, which we refer to as “inverse hierarchy MFV”, features Wilson coefficients inversely proportional to quark masses, and arises from BSM models respecting MFV and containing heavy fields that replicate the mass hierarchy of SM quarks. We then analyze the phenomenology driven by cuW at colliders and at lower-energy flavor experiments. We show that precision measurements of the process pp → Wh → γγℓν at FCC-hh could set an upper bound on |cuW| ≲ $$ \mathcal{O} $$ O (10−2)(Λ/TeV)2, with Λ the cutoff of the effective field theory. This bound is an order of magnitude stronger than the existing LHC bounds. Moreover, we estimate that Wh → $$ b\overline{b}\ell \nu $$ b b ¯ ℓ ν at HL-LHC could also give competitive bounds. In the low-energy regime, we consider bounds arising from rare kaon decays, which turn out to be loose, |$$ {c}_{uW}^{11} $$ c uW 11 | <$$ \mathcal{O} $$ O (1)(Λ/TeV)2. We finally demonstrate that our flavor and operator assumptions can be derived from a weakly-coupled UV model, which we choose to simultaneously illustrate the UV origin of inverse hierarchy MFV.