Theoretical constraints on the Higgs effective couplings

By I. Low, R. Rattazzi, A. Vichi. 2009

179 citations recorded by the source corpus.

We derive constraints on the sign of couplings in an effective Higgs Lagrangian using prime principles such as the naturalness principle, global symmetries, and unitarity. Specifically, we study four dimension-six operators, $ {\mathcal{O}_H} $, $ {\mathcal{O}_y} $, $ {\mathcal{O}_g} $, and $ {\mathcal{O}_\gamma } $, which contribute to the production and decay of the Higgs boson at the Large Hadron Collider (LHC), among other things. Assuming the Higgs is a fundamental scalar, we find: 1) the coefficient of $ {\mathcal{O}_H} $ is positive except when there are triplet scalars, resulting in a reduction in the Higgs on-shell coupling from their standard model (SM) expectations if no other operators contribute, 2) the linear combination of $ {\mathcal{O}_H} $ and $ {\mathcal{O}_y} $ controlling the overall Higgs coupling to fermion is always reduced, 3) the sign of $ {\mathcal{O}_g} $ induced by a new colored fermion is such that it interferes destructively with the SM top contribution in the gluon fusion production of the Higgs, if the new fermion cancels the top quadratic divergence in the Higgs mass, and 4) the correlation between naturalness and the sign of $ {\mathcal{O}_\gamma } $ is similar to that of $ {\mathcal{O}_g} $, when there is a new set of heavy electroweak gauge bosons. Next considering a composite scalar for the Higgs, we find the reduction in the on-shell Higgs couplings persists. If further assuming a collective breaking mechanism as in little Higgs theories, the coefficient of $ {\mathcal{O}_H} $ remains positive even in the presence of triplet scalars. In the end, we conclude that the gluon fusion production of the Higgs boson is reduced from the SM rate in all composite Higgs models. Our study suggests a wealth of information could be revealed by precise measurements of the Higgs couplings, providing strong motivations for both improving on measurements at the LHC and building a precision machine such as the linear collider.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7a0b1bd556c5e97a7ba477d90d24f667d56ddd56

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

Citations in the corpus

LHC HXSWG interim recommendations to explore the coupling structure of a Higgs-like particle (2012, unknown): “κ2 (Zγ)(κb, κt, κτ, κW,mH) κ2 (Zγ) (13)”
Softness and amplitudes’ positivity for spinning particles (2016, background): “In this case only a once-subtracted dispersion relation for M′ would be IR convergent; one would need then to make extra assumptions about the high energy behavior of the amplitude as in [8, 9], since the Froissart bound is not longer enough to discard the big circle’s contribution C∞ with just one ”
Strong double higgs production at the LHC (2010, background): “In the case of a pseudo-Goldstone Higgs one can prove in general that a;b 22 ], while all known models also satisfy c v or fD 1.”
A non Standard Model Higgs at the LHC as a sign of naturalness (2011, background): “In the supersymmetric limit, light stops increase the LHC Higgs production crosssection [11–15], since the latter is related to the β-function of αs to which scalar fields contribute with the same sign as fermions [16, 17].”
Interpreting LHC Higgs results from natural new physics perspective (2012, background): “In composite Higgs models under certain conditions one can argue that the gluon fusion and diphoton decay rate cannot be enhanced [59].”