arXiv subjects

Maria J. Herrero

Publications and source records attributed to Maria J. Herrero.

18 recordsLinked to original sources

arXiv2025

HEFT's appraisal of triple (versus double) Higgs weak boson fusion

Multi-Higgs boson interactions with massive gauge bosons are known to be tell-tale probes of the vacuum manifold of electroweak symmetry breaking. Phenomenologically, a precise determination of these parameters is hampered through increasingly rare processes at the presently available energy frontier provided by the Large Hadron Collider. Contact interactions of three Higgs bosons with the $W$ and $Z$ bosons seem currently well out of experimental reach due to an irrelevant SM production cross section. From a theoretical perspective, in perturbative extensions of the SM such interactions are suppressed by weak loops and further diluted in a priori sensitive processes like weak boson fusion (WBF) when they admit a dimension-six Standard Model Effective Field Theory description. In this work, we identify scenarios that can indeed lead to large, and perhaps even observable modifications of WBF triple Higgs production most directly parametrised by Higgs Effective Field Theory. We critically analyse these enhancements at the LHC and future colliders from the perspective of unitarity and demonstrate the radiative stability of such analyses under QCD corrections at hadron colliders. Taking into account the restrictions from unitarity, we finally study the expected sensitivity to the electroweak triple Higgs production within HEFT, considering $HHVV$ and $HHHVV$ effective couplings, at both future hadron and lepton colliders. Particularly, we present numerical predictions for LHC, FCC, CLIC and muon colliders.

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arXiv2024

Bosonic multi-Higgs correlations beyond leading order

The production of multiple Higgs bosons at the LHC and beyond is a strong test of the mechanism of electroweak symmetry breaking. Taking inspiration from recent experimental efforts to move towards limits on triple Higgs production at the Large Hadron Collider, we consider generic bosonic deviations of $HH$ and $HHH$ production from the Standard Model in the guise of Higgs Effective Field Theory. Including one-loop radiative corrections within the HEFT and going up to ${\mathcal{O}}(p^4)$ in the momentum expansion, we provide a detailed motivation of the parameter range that the LHC (and future hadron colliders) can explore, through accessing non-standard coupling modifications and momentum dependencies that probe Higgs boson non-linearities. In particular, we find that radiative corrections can enhance the sensitivity to Higgs-self coupling modifiers and HEFT-specific momentum dependencies can vastly increase triple Higgs production thus providing further motivation to consider these processes during the LHC's high-luminosity phase.

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arXiv2021

One-loop renormalization of VBS with the electroweak chiral Lagrangian in covariant gauges

This work presents a first full one-loop computation of vector boson scattering (VBS) within the non-linear effective field theory given by the bosonic sector of the usually called electroweak chiral Lagrangian (EChL). The computation is performed in the most general case of covariant $R_ξ$ gauges and is compared through all this work with the Standard Model case, whose computation in these covariant gauges is also novel and is presented also here. The calculation of the one-loop VBS amplitude is performed using the diagrammatic method by means of the one-particle-irreducible (1PI) Green functions that are involved in these scattering processes. The central part of this work is then devoted to the renormalization of all the n-legs one-loop 1PI Green functions involved. This renormalization is performed in the most general off-shell case with arbitrary external legs momenta. We then describe in full detail the renormalization program, which within this context of the EChL, implies to derive all the counterterms for both the electroweak parameters, like boson masses and gauge couplings, and those for the EChL coefficients. These later are crucial for the renormalization of the new divergences typically appearing when computing loops with the lowest chiral dimension Lagrangian. We present here the full list of involved divergences and counterterms in the $R_ξ$ gauges and derive the complete set of renormalization group equations for the EChL coefficients. In the last part of this work, we present the EChL numerical results for the one-loop cross section in the WZ channel and compare them with the SM results.

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arXiv2017

Higgs effective $Hl_il_j$ vertex from heavy $ν_R$ and applications to LFV phenomenology

We present a new computation of the Lepton Flavor Violating effective vertex involving the Higgs boson and two leptons with different flavors. This vertex is generated from the integration to one-loop level of the heavy right handed neutrinos which are considered here within the context of the Low Scale Seesaw Models and with masses close to the TeV scale. We apply the Mass Insertion Approximation technique to compute the loop contributions from these heavy $ν_R$ and derive a symple analytical formula for the $Hl_il_j$ effective vertex in terms of the input $Y_ν$ Yukawa coupling matrix and right handed $M_R$ neutrino masses. Some interesting phenomenological applications of this $Hl_il_j$ effective vertex are also included.

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arXiv2014

Remark on the one-loop Z form factors for LFV Z-penguin diagrams in SUSY

In this note we shortly comment on our analytical results in PRD73(2006)055003 for the $Z$ boson one-loop form factors contributing to the Lepton Flavour Violating $Z$ penguin diagrams in SUSY. In a recent communication [arXiv:1312.5318v1] it has been pointed out a mistake in our formulas for the chargino contribution to the $Z$-form factor, $F_L^{(c)}$, and these authors have included corrections to our results in a way that we do not agree with. We wish to clarify here what are the correct results for these form factors.

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arXiv2005

Decays of MSSM Higgs in Flavour-Changing Quark Channels

We compute the genuine SUSY one-loop quantum contributions to flavour-changing MSSM Higgs-boson decays into $b \bar s$ and $s \bar b$ using the full diagrammatic approach that is valid for all $\tan β$ values and do not rely on the mass-insertion approximation for the characteristic flavour-changing parameter. We analyze in full detail the dependence of these flavour-changing partial widths on all the relevant MSSM parameters and also study the non-decoupling behaviour of these widths with the SUSY mass parameters. We find that these contributions are sizable as compared to the SM ones, and can be very efficient as an indirect method in the future search for Supersymmetry.

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arXiv2003

Non-decoupling effects of SUSY in the physics of Higgs bosons and their phenomenological implications

We consider a plausible scenario in the Minimal Supersymmetric Standard Model (MSSM) where all the genuine supersymmetric (SUSY) particles are heavier than the electroweak scale. In this situation, indirect searches via their radiative corrections to low energy observables are complementary to direct searches, and they can be crucial if the SUSY masses are at the TeV energy range. We summarize the most relevant heavy SUSY radiative effects in Higgs boson physics and emphasize those that manifest a non-decoupling behaviour. We focus, in particular, on the SUSY-QCD non-decoupling effects in fermionic Higgs decays, flavour changing Higgs decays and Yukawa couplings. Some of their phenomenological implications at future colliders are also studied.

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arXiv2003

Quantum effects to the Higgs boson self-couplings in the SM and in the MSSM

We show that the effects of heavy Higgs particles and heavy top-squarks in the one-loop self-couplings of the lightest CP-even MSSM Higgs boson decouple from the low energy theory when the self-couplings are expressed in terms of the Higgs boson mass M_h0. Our conclusion is that the h^0 self-interactions become very close to those of the SM Higgs boson and, therefore, MSSM quantum effects could only be revealed by very high precision experiments.

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arXiv2002

Self-interactions of the lightest MSSM Higgs boson in the large pseudoscalar-mass limit

We investigate the decoupling properties of the Higgs-sector-induced one-loop corrections in the lightest Higgs-boson self-couplings, in the framework of the Minimal Supersymmetric Standard Model (MSSM). The renormalized n-point vertex functions with external Higgs particles in the MSSM and in the SM are derived to the one-loop level and compared in the MA >> MZ limit. The computation has been done in a general R_{xi} gauge and the on-shell renormalization scheme is chosen. By a comparison of the renormalized lightest Higgs-boson h^0 vertex functions with respect to the corresponding SM ones, we find that the differences between the predictions of both models are summarized in the lightest Higgs-boson mass correction Delta Mh. Consequently, the radiative corrections are absorbed in the Higgs-boson mass, and the trilinear and quartic h^0 self-couplings acquire the same structure as the couplings of the SM Higgs-boson. Therefore, decoupling of the heavy MSSM Higgs bosons occurs and the MSSM h^0 self-interactions converge to the SM ones in the MA >> MZ limit.

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arXiv2002

Flavour Changing Neutral Higgs Boson Decays from Squark - Gluino Loops

We study the flavour changing neutral Higgs boson decays that can be induced from genuine supersymmetric particles at the one-loop level and within the context of the Minimal Supersymmetric Standard Model. We consider all the possible flavour changing decay channels of the three neutral Higgs bosons into second and third generation quarks, and focus on the Supersymmetric-QCD corrections from squark-gluino loops which are expected to provide the dominant contributions. We assume here the more general hypothesis for flavour mixing, where there is misalignment between the quark and squark sectors, leading to a flavour non-diagonal squark mass matrix. The form factors involved, and the corresponding Higgs partial decay widths and branching ratios, are computed both analytically and numerically, and their behaviour with the parameters of the Minimal Supersymmetric Standard Model and with the squark mass mixing are analyzed in full detail. The large rates found, are explained in terms of the non-decoupling behaviour of these squark-gluino loop corrections in the scenario with very large supersymmetric mass parameters. Our results show that if these decays are seen in future colliders they could provide clear indirect signals of supersymmetry.

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arXiv2002

Optimal observables to search for indirect supersymmetric QCD signals in Higgs boson decays

In this work we study the indirect effects of squarks and gluinos via supersymmetric QCD radiative corrections in the decays of Higgs particles within the Minimal Supersymmetric Standard Model. We consider a heavy supersymmetric spectrum and focus on the main nondecoupling effects. We propose a set of observables that are sensitive to these corrections and that will be accessible at the CERN Large Hadron Collider and Fermilab Tevatron. These observables are the ratios of Higgs boson branching ratios into quarks divided by the corresponding Higgs boson branching ratios into leptons, and both theoretical and experimental uncertainties are expected to be minimized. We show that these nondecoupling corrections are sizable for all the proposed observables in the large $\tanβ$ region and are highly correlated. A global analysis of all these observables will allow the experiments to reach the highest sensitivity to indirect supersymmetric signals.

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arXiv2002

Effective Higgs-quark-quark couplings from a heavy SUSY spectrum

In this paper we study the Yukawa Higgs-quark-quark interactions that are generated from radiative corrections of squarks and gluinos, in the Minimal Supersymmetric Standard Model. We compute the corrections to the effective action for Higgs and quark fields that are produced by explicit integration, in the path integral formalism, of all the squarks and gluinos, at the one-loop level and order $α_s$. In addition, we consider the limit of nearly degenerate heavy squarks and gluinos, with masses much larger than the electroweak scale, and derive the effective Lagrangian containing all the relevant new local Higgs-quark-quark interactions. We show that these new interactions do remain non-vanishing, even in the case of infinitely heavy supersymmetric particles and, therefore, we demonstrate explicitly the non-decoupling behavior of squarks and gluinos in Higgs bosons physics. We present the set of new Yukawa couplings and finally derive the corresponding one-loop, order $α_s$, corrections to the Higgs bosons partial decay widths into quarks.

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arXiv2001

Indirect heavy SUSY signals in Higgs and top decays

We summarize the recent results on the supersymmetric QCD radiative corrections, at the one-loop level, in Higgs and top quark decays, in the context of the Minimal Supersymmetric Standard Model and in the decoupling limit of very heavy SUSY particles. Special attention is devoted to the particular decays $h^0\to b \bar b$, $H^+\to t \bar b$, $H^0\to b \bar b$, $A^0\to b \bar b$ and $t \to H^+\bar b$ where the radiative corrections from heavy squarks and heavy gluinos do not decouple and are enhanced at large $\tan β$. Some interesting phenomenological consequences are also briefly summarized.

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arXiv2001

SUSY-QCD decoupling properties in H+ -> t \bar b decay

The SUSY-QCD radiative corrections to the Γ(H+ -> t \bar b) partial decay width are analyzed within the Minimal Supersymmetric Standard Model at the one-loop level, {\mathcal O}(α_s), and in the decoupling limit. We present the analytical expressions of these corrections in the large SUSY masses limit and study the decoupling behaviour of these corrections in various limiting cases. We find that if the SUSY mass parameters are large and of the same order, the one loop SUSY-QCD corrections {\it do not decouple}. The non-decoupling contribution is enhanced by \tan βand therefore large corrections are expected in the large \tan βlimit. In contrast, we also find that the SUSY-QCD corrections decouple if the masses of either the squarks or the gluinos are separately taken large.

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arXiv2000

The Higgs sector of the MSSM in the decoupling limit

We study the heavy Higgs sector of the MSSM composed of the H^\pm, H^0 and A^0 particles in the so-called decoupling limit where m_{A^0} >> m_Z. By integrating out these heavy Higgs particles to one-loop, we compute the effective action for the electroweak gauge bosons and find out that, in the decoupling limit, all the heavy Higgs effects can be absorbed into redefinitions of the Standard Model electroweak parameters. This demonstrates explicitely that the decoupling theorem works for the heavy MSSM Higgs particles. This is also compared with the paradigmatic and different case of the Standard Model heavy Higgs particle. Finally, this work together with our two previous works, complete the demonstration that all the non-standard particles in the MSSM, namely, squarks, sleptons, charginos, neutralinos and the heavy Higgs particles, decouple to one-loop from the low energy electroweak gauge boson physics.

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arXiv2000

SUSY-QCD corrections to the MSSM $h^0 b \bar b$ vertex in the decoupling limit

We analyze the supersymmetric (SUSY) QCD contribution to the $h^0 b \bar{b}$ coupling at one loop in the Minimal Supersymmetric Model (MSSM) in the decoupling limit. Analytic expressions in the large SUSY mass region are derived and the decoupling behavior of the corrections is examined in various limiting cases, where some or all of the SUSY mass parameters become large. We show that in the decoupling limit of large SUSY mass parameters and large CP-odd Higgs mass, the $h^0 b \bar b$ coupling approaches its Standard Model value at one loop. However, the onset of decoupling is delayed when $\tanβ$ is large. In addition, the one-loop SUSY-QCD corrections decouple if the masses of either the bottom squarks or the gluino are separately taken large; although the approach to decoupling is significantly slower in the latter case.

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arXiv1996

Introduction To The Symmetry Breaking Sector

The basic ingredients of the Spontaneous Symmetry Breaking Phenomenon and of the Higgs Mechanism are reviewed in these lectures of pedagogical character. Some relevant topics related with the breaking $\gs \rightarrow U(1)_{\rm em}$ are selected and discussed here. A brief survey of the experimental Higgs particle searches and the theoretical limits on $\mh$ are also presented. The main features of the most popular models of symmetry breaking beyond the Standard Model are briefly considered. It includes a short summary of the Higgs Sector in the Minimal SUSY Model, the basic ideas of Technicolor models and a brief introduction to Strongly Interacting Scalar sectors and to the Effective Chiral Lagrangian Approach to the Electroweak Theory.

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arXiv1994

Non-decoupling effects of the Standard Model Higgs boson to one loop

We study the complete non-decoupling effects of the standard model Higgs boson to one loop. Using effective field theory methods, we integrate out the Higgs boson and represent its non-decoupling effects by a set of gauge invariant effective operators of the electroweak chiral Lagrangian. In a previous work, we analyzed the non-decoupling effects in the two and three point Green's functions of gauge fields. We complete here the calculation of the chiral effective operators by analyzing the four point functions. We discuss in detail the relation between the renormalization of both the standard model and the effective theory, which is crutial for a correct understanding and use of the electroweak chiral Lagrangian. Some examples have been chosen to show the applicability of this effective Lagrangian approach in the calculation of low energy observables in electroweak theory.

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