arXiv subjects

Mariano Quirós

Publications and source records attributed to Mariano Quirós.

15 recordsLinked to original sources

arXiv2024

Implication of preheating on gravity assisted baryogenesis in $R^2$-Higgs inflation

We investigate the impact of preheating on baryogenesis in $R^2$-Higgs inflation. In this scenario, the inclusion of a dimension-six operator ${(R/ Λ^2)} B_{μν} \widetilde{B}^{μν} $ abundantly generates helical hypermagnetic fields during inflation, leading to a baryon asymmetric Universe at the electroweak crossover. Focusing on the $R^2$-like regime, we first derive the relevant dynamics of preheating using a doubly-covariant formalism. We find that preheating can happen for the Higgs, transverse gauge and Goldstone bosons, however, it is dependent on the value of the non-minimal coupling $ξ_H$ between the Standard Model Higgs field and the Ricci scalar. We identify the preheating temperature to determine the appropriate scale $Λ$ for driving baryogenesis, which is around $Λ\sim 2.2 \, (2.6) \times 10^{-5}\, M_{\rm P}$ for $ξ_H \sim 1 \, (10)$. Our results represent the most accurate estimation of the scale of gravity induced baryogenesis in $R^2$-Higgs inflation to date. Areas for further improvement are identified.

hep-ph↗

arXiv2024

Baryogenesis in $R^2$-Higgs Inflation: the Gravitational Connection

$R^2$-Higgs inflation stands out as one of the best-fit models of Planck data. Using a covariant formalism for the inflationary dynamics and the production of helical gauge fields, we show that the observed baryon asymmetry of the Universe (BAU) can be obtained when this model is supplemented by a dimension-six CP-violating term $\sim (R/Λ^2)\, B_{μν} \widetilde{B}^{μν}$ in the hypercharge sector. At linear order, values of $Λ\simeq 2.5\times10^{-5}\ M_{\rm P}$ produce, in the $R^2$-like regime, sufficient helical hypermagnetic fields to create the observed matter-antimatter asymmetry during the electroweak crossover. However, the Schwinger effect of fermion pair production can play a critical role in this context, and that scale is significantly lowered when the backreaction of the fermion fields on the gauge field production is included. In all cases, the helical field configurations can remain robust against washout after the end of inflation.

astro-ph.CO↗

arXiv2023

Numerical study of the Schwinger effect in axion inflation

Previous studies demonstrate that the inflaton, when coupled to the hypercharge Chern-Simons density, can source an explosive production of helical hypermagnetic fields. Then, in the absence of fermion production, those fields have the capability of preheating the Universe after inflation and triggering a successful baryogenesis mechanism at the electroweak phase transition. In the presence of fermion production however, we expect a strong damping of the gauge fields production from the fermion backreaction, a phenomenon called Schwinger effect, thus jeopardizing their original capabilities. Using numerical methods we study the backreaction on the generated gauge fields and revisit the processes of gauge preheating and baryogenesis in the presence of the Schwinger effect. We have found that gauge preheating is very unlikely, while still having a sizable window in the parameter space to achieve the baryon asymmetry of the Universe at the electroweak phase transition.

hep-ph↗

arXiv2023

Baryogenesis from Higgs Inflation

If the inflaton field is coupled to the hypercharge Chern-Simons density $F\tilde F$, an explosive production of helical gauge fields when inflation ends can trigger baryogenesis at the electroweak phase transition. Besides, Higgs inflation identifies the inflaton with the Higgs field $\mathcal H$, thus relating cosmological observables to properties of electroweak physics. In this paper we merge both approaches: the helical gauge fields are produced at the end of Higgs inflation from the coupling $|\mathcal H|^2 F\tilde F$. In the metric formulation of gravity we found a window in the parameter space for electroweak baryogenesis consistent with all experimental observations. Conversely, for the Palatini formalism the non-gaussianity bounds strongly constrain the helicity produced at the end of inflation, forbidding an efficient baryogenesis.

hep-ph↗

arXiv2022

Baryogenesis from combined Higgs - scalar field inflation

We study a modification of the Higgs inflation scenario where we introduce an extra scalar $ϕ$, with mass $m$, coupled to the Ricci scalar as $gϕ^2 R$, and mixed with the Higgs field $h$ via the Lagrangian term $μϕh^2$. Both fields participate in the inflation process in a unitary theory that predicts values of the cosmological observables in agreement with the results from the Planck/BICEP/Keck collaborations. In addition, by means of a $\mathcal{CP}$-odd effective operator that couples $ϕ$ to the Chern-Simons term of the hypercharge gauge group as $f_ϕ^{-1}ϕ\,Y_{μν}\tilde Y^{μν}$, maximally helical magnetic fields are produced during the last $e$-folds of inflation. We found a window in the coupling $ f_ϕ$ where these fields survive all constraints until the electroweak phase transition, and source the baryon asymmetry of the Universe through the Standard Model chiral anomaly. From a phenomenological perspective, the model can solve the Standard Model instability problem at the scale $\mathcal Q_I\simeq 10^{11}$ GeV, provided that $μ\lesssim m \lesssim \mathcal Q_I$, and for $m\lesssim \mathcal{O}$(few)~TeV, the $ϕ$-$h$ mixing becomes sizable while the theory turns natural. The latter thus predicts modifications of the trilinear and quartic couplings that could be explored at the HE-LHC, as well as at future colliders, and allows for direct $ϕ$ production at the LHC followed by decay into $hh$. Present results from ATLAS and CMS already put (mild) bounds on the mass of the heavy scalar as $m\gtrsim 0.55$~TeV at 95\% C.L.

hep-ph↗

arXiv2022

LHC search strategy for squarks in higgsino-LSP scenarios with leptons and $b$-jets in the final state

The higgsino Lightest Supersymmetric Particle (LSP) scenario opens up the possibility of decays of strongly produced particles to an intermediate neutralino, due to the Yukawa-suppressed direct decays to the higgsino. Those decays produce multijet signals with a Higgs or a $Z$ boson being produced in the decay of the intermediate neutralino to the LSP. In this paper we study the discovery prospects of squarks that produce $b$-jets and leptons in the final state. Our collider analysis provides signal significances at the 3$σ$ level for luminosities of 1 ab$^{-1}$, and at the 5$σ$ level if we project these results for 3 ab$^{-1}$.

hep-ph↗

arXiv2021

Hunting Squarks in Higgsino LSP scenarios at the LHC

The assumption that strongly interacting sparticles will decay directly to the LSP plus jets breaks down in situations where those decays are Yukawa suppressed. That occurs when producing the first two generations of squarks and when, at the same time, there are several electroweakinos lighter than those squarks. In this paper we analyze the signal of pair production of squarks that subsequently decay to an intermediate neutralino ($\tildeχ_3^0$) plus jets. The neutralino will then decay to the LSP (mainly higgsino) and a Higgs. We have simulated the events and designed a discovery strategy based on a signal of two jets, four $b$-quarks and missing transverse energy. We obtain very promising values for the LHC sensitivity at 14 TeV and 300 fb$^{-1}$.

hep-ph↗

arXiv2021

Search strategy for gluinos at the LHC with a Higgs boson decaying into tau leptons

The possibility in supersymmetric scenarios that the dark matter candidate is a Higgsino-like neutralino means that its production can be associated with Higgs bosons. Taking advantage of this fact, we propose a LHC search strategy for gluinos with $τ$ leptons in the final state, coming from the decay of a Higgs boson. We consider the strong production of a pair of gluinos, one of which decays into the Higgsino plus jets while the other decays into the bino plus jets. In turn, this bino decays into the Higgsino plus a Higgs boson which finally decays into a $τ$-lepton pair. Therefore, the experimental signature under study consists of 4 jets, 2 $τ$ leptons, and a large amount of missing transverse energy. Our cut-based search strategy allows us to reach, for a LHC center-of-mass energy of 14 TeV and a total integrated luminosity of 1 ab$^{-1}$, significances of up to 2 standard deviations, considering systematic uncertainties in the SM background of 30\%. The projections for 3 ab$^{-1}$ are encouraging, with significances at the evidence level, which in more optimistic experimental scenarios could exceed 4 standard deviations.

hep-ph↗

arXiv2021

On Broad Kaluza-Klein Gluons

In theories with a warped extra dimension, composite fermions, as e.g. the right-handed top quark, can be very strongly coupled to Kaluza-Klein (KK) fields. In particular, the KK gluons in the presence of such composite fields become very broad resonances, thus remarkably modifying their experimental signatures. We have computed the pole mass and the pole width of the KK gluon, triggered by its interaction with quarks, as well as the prediction for proton-proton cross-sections using the full propagator and compared it with that obtained from the usual Breit-Wigner approximation. We compare both approaches, along with the existing experimental data from ATLAS and CMS, for the $t\bar t$, $t\bar t W$, $t\bar t Z$, $t\bar t H$, and $t\bar t t\bar t$ channels. We have found differences between the two approaches of up to about 100%, highlighting that the effect of broad resonances can be dramatic on present, and mainly future, experimental searches. The channel $t\bar t t\bar t$ is particularly promising because the size of the cross-section signal is of the same order of magnitude as the Standard Model prediction, and future experimental analyses in this channel, especially for broad resonances, can shed light on the nature of possible physics beyond the Standard Model.

hep-ph↗

arXiv2021

Novel Higgsino Dark Matter Signatures at the LHC

In the LHC searches for gluinos it is usually assumed that they decay predominantly into the lightest neutralino plus jets. In this work we perform a proof-of-concept collider analysis of a novel supersymmetric signal in which gluinos decay mostly into jets and the bino-like neutralino ($\tildeχ_3^0$), which in turn decays into the lightest Higgsino-like neutralino ($\tildeχ_1^0$), considered the dark matter candidate, together with the SM-like Higgs boson ($h$). This new physics signal then consists of an LHC final state made up by four light jets, four $b$-jets, and a large amount of missing transverse energy. We identify $t \bar t$, $V$+jets ($V$= $W$, $Z$), and $t \bar t + X$ ($X$ = $W$, $Z$, $γ^*$, $h$) productions as the most problematic backgrounds, and develop a search strategy for the high luminosity phase of the LHC, reaching signal significances at the evidence level for a luminosity of 1000 fb$^{-1}$. The prospects for a luminosity of 3000 fb$^{-1}$ are even more promising, with discovery-level significances.

hep-ph↗

arXiv2021

Higgsino Dark Matter in the MSSM

A comologically stable neutral component from a nearly pure $SU(2)$ doublet, with a mass $\sim$1.1 TeV, is one appealing candidate for dark matter (DM) consistent with all direct dark matter searches. We have explored this possibility in the context of the Minimal Supersymmetric extension of the Standard Model (MSSM), with the Higgsino playing the role of DM, in theories where supersymmetry breaking is transmitted by gravitational interactions at the unification scale $M\simeq 2\times 10^{16}$ GeV. We have focussed our work in the search of "light" supersymmetric spectra, which could be at reach of present and/or future colliders, in models with universal and non-universal Higgs and gaugino Majorana masses. The lightest supersymmetric particles of the spectrum are, by construction, two neutralinos and one chargino, almost degenerate, with a mass $\sim $1.1 TeV, and a mass splitting of a few GeV. Depending on the particular scenario the gluino can be at its experimental mass lower bound $\sim$ 2.2 TeV; in the squark sector, the lightest stop can be as light as $\sim$ 1.3 TeV, and the lightest slepton, the right-handed stau, can have a mass as light as $1.2$ TeV. The lightest neutralino can be found at the next generation of direct dark matter experimental searches. In the most favorable situation, the gluino, with some specific decay channels, could be found at the next run of the Large Hadron Collider (LHC), and the lightest stop at the High-Luminosity LHC run.

hep-ph↗

arXiv2020

Dark CP Violation and Gauged Lepton/Baryon Number for Electroweak Baryogenesis

We explore the generation of the baryon asymmetry in an extension of the Standard Model where the lepton number is promoted to a $U(1)_\ell$ gauge symmetry with an associated $Z^\prime$ gauge boson. This is based on a novel electroweak baryogenesis mechanism first proposed by us in Ref. \cite{Carena:2018cjh}. Extra fermionic degrees of freedom - including a fermionic dark matter $χ$ - are introduced in the dark sector for anomaly cancellation. Lepton number is spontaneously broken at high scale and the effective theory, containing the Standard Model, the $Z^\prime$, the fermionic dark matter, and an additional complex scalar field $S$, violates CP in the dark sector. The complex scalar field couples to the Higgs portal and is essential in enabling a strong first order phase transition. Dark CP violation is diffused in front of the bubble walls and creates a chiral asymmetry for $χ$, which in turn creates a chemical potential for the Standard Model leptons. Weak sphalerons are then in charge of transforming the net lepton charge asymmetry into net baryon number. We explore the model phenomenology related to the leptophilic $Z^\prime$, the dark matter candidate, the Higgs boson and the additional scalar, as well as implications for electric dipole moments. We also discuss the case when baryon number $U(1)_B$ is promoted to a gauge symmetry, and discuss electroweak baryogenesis and its corresponding phenomenology.

hep-ph↗

arXiv2018

Electroweak Baryogenesis From Dark CP Violation

We present a novel mechanism of electroweak baryogenesis where \textit{CP} violation occurs in a dark sector, comprised of standard model gauge singlets, thereby evading the strong electric dipole moment constraints. In this framework, the background of time-like component of a new gauge boson $Z^\prime_μ$, generated at electroweak temperatures, drives the electroweak sphaleron processes to create the required baryon asymmetry. We first discuss the crucial ingredients for this mechanism to work, and then show that all of them can be elegantly embedded in ultraviolet completions with spontaneously broken gauged lepton number. The models under consideration have a rich phenomenology and can be experimentally probed in leptophilic $Z^\prime$ searches, dark matter searches, heavy Majorana neutrino searches, as well as through hunting for new Higgs portal scalars in multi-lepton channels at colliders.

hep-ph↗

arXiv1994

Bounds on the Higgs Mass in the Standard Model and Minimal Supersymmetric Standard Model

We present bounds on the Higgs mass in the Standard Model and in the Minimal Supersymmetric Standard Model using the effective potential with next-to-leading logarithms resummed by the renormalization group equations, and physical (pole) masses for the top quark and Higgs boson. In the Standard Model we obtain lower bounds from stability requirements: they depend on the top mass and the cutoff scale. In the Minimal Supersymmetric Standard Model we obtain upper bounds which depend on the top mass and the scale of supersymmetry breaking. A Higgs mass measurement could discriminate, depending on the top mass, between the two models. Higgs discovery at LEP-200 can put an upper bound on the scale of new physics.

hep-ph↗

arXiv1993

On Daisy and Superdaisy Resummation of the Effective Potential at Finite Temperature

We describe in detail, in the context of the simple scalar $ϕ^4$ theory, the prescription for resummation of daisy and superdaisy diagrams in the effective potential using the solution of the gap equations in the infrared limit. We find that the latter procedure is consistent provided we neglect logarithmic terms from the finite-temperature self energies and from the integration of overlapping momenta. This amounts to dressing only the zero-mode contribution to the finite-temperature effective potential. Improving also the non-zero modes, would require exactly solving (not in the IR limit) the gap equations. In general this can only be done in a theory where all self-energies are momentum independent ({\em e.g.} in the scalar theory at the symmetric phase $ϕ=0$). However some partial dressing procedures are still possible in general.

hep-ph↗