arXiv subjects

Gustavo Burdman

Publications and source records attributed to Gustavo Burdman.

At least 19 recordsLinked to original sources

arXiv2026

The Radial Mode of Composite Higgs Theories at the LHC

We examine the potential of the LHC to observe the scalar radial excitation present in extensions of the standard model where the Higgs boson is a pseudo Nambu Golstone boson. These include composite Higgs models as well as the twin Higgs model. These states can be light enough to be seen at the LHC, potentially resulting in additional clues about the nature of the Higgs sector. We present the current status of LHC bounds as well as the future prospects for the the high luminosity LHC (HL-LHC). We identify the most sensitive channels as those where the radial state decays to a pair of Higgs bosons, especially at the high luminosity stage. For the minimal composite Higgs models we study, we make use of the LHC Run 2 data with ${\cal L}=138~{\rm fb}^{-1}$ to extract the $2\sigma $ mass bounds $m_\sigma\geq (0.93-1.13)~$TeV, where the values on the interval depend on the parameters of the model. We show that the reach of the HL-LHC for these cases is $m_\sigma\geq (1.8-2.2)~TeV$, with ${\cal L}=3000~{\rm fb}^{-1}$. For the twin Higgs model radial state, the current bounds are set by Higgs coupling measurements, while for the HL-LHC we obtain the reach $m_\sigma\geq 1.2~$TeV, corresponding to the lowest symmetry breaking scale allowed by current data.

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arXiv2025

Spontaneous Symmetry Breaking and the Higgs Mechanism

The Higgs sector of the standard model of particle physics plays a central role in the generation of all the masses of elementary particles known so far. Here we give a pedagogical introduction to all the elements leading ot the Higgs mechanism and the Higgs boson, starting with the spontaneous symmetry breaking of global symmetries and the Goldstone theorem. We then consider the case of gauge symmetries, i.e. the Higgs mechanism, and its application to the electroweak sector of the standard model. We close with a reflection on the possible open questions that the very introduction of the Higgs sector in the standard model posses.

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arXiv2024

Quantum field theory and the electroweak Standard Model

In these lectures we give an introduction and overview of the electroweak standard model (EWSM) of particle physics. We first introduce the basic concepts of quantum field theory necessary to build the EWSM: abelian and non-abelian gauge theories, spontaneous symmetry breaking and the Higgs mechanism. We also introduce some basic concepts of renormalization, so as to be able to understand the full power of electroweak precision tests and their impact on our understanding the EWSM and its possible extensions. We discuss the current status of experimental tests and conclude by pointing the problems still existing in particle physics not solved by the EWSM and how these impact the future of the field.

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arXiv2024

Displaced vertex signals of low temperature baryogenesis

We explore the connection of baryogenesis at temperatures below the electroweak scale and signals for long-lived particles at the LHC. The model features new SM singlets, with a long-lived fermion decaying to quarks to generate the baryon asymmetry. The model avoids strong flavor physics bounds while predicting a rich diquark phenomenology, monojet signals, and displaced vertices. We show how the displaced vertex signals can be probed at the HL-LHC. The large transverse production makes a strong physics case for constructing far detector experiments such as MATHUSLA, ANUBIS, and CODEX-b, complementary to the central and forward long-lived particle program.

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arXiv2024

Spontaneous breaking of baryon number, baryogenesis and the bajoron

We explore the spontaneous breaking of global baryon number for baryogenesis. We introduce a model with three majorana fermions and a complex scalar carrying baryon number charge. After symmetry breaking, the baryon asymmetry is generated below the electroweak scale via the decays of one of the majorana fermions. The main focus of the paper is the phenomenology of the Nambu--Goldstone boson of $U(1)_B$, which we call the bajoron. With small sources of explicit baryon number violation, the bajoron acquires a small mass and is generally very long-lived. The model avoids proton decay, satisfies cosmological constraints, and offers interesting collider phenomenology for the Large Hadron Collider. These long-lived particles tied to baryogenesis strongly support the development of far-detector experiments such as MATHUSLA, FASER, SHiP, and others.

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arXiv2024

Neutrino Masses in the Mirror Twin Higgs with Spontaneous $\mathbb{Z}_2$ Breaking

We introduce a mirror twin Higgs model with spontaneous $\mathbb{Z}_2$ symmetry breaking that ameliorates the constraints in twin Higgs cosmology and, at the same time, generates the Standard Model neutrino masses. The model features an $SU(2)$ triplet with hypercharge $1$ alongside its twin counterpart. Spontaneous breaking of both $\mathbb{Z}_2$ and electroweak symmetry occurs in the scalar sector. The Standard Model neutrinos acquire small masses through the type-II seesaw mechanism. In contrast, their twin counterparts acquire large masses, effectively addressing the dark radiation problem in mirror twin Higgs scenarios. We study the impact of the model on the $N_{\rm eff.}$ constraints, as well as on collider phenomenology.

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arXiv2023

Baryogenesis and Dark Matter in the Mirror Twin Higgs

We consider a natural asymmetric dark matter (ADM) model in the mirror twin Higgs (MTH). We show that it is possible to obtain the correct dark matter (DM) abundance when a twin baryon is the DM without the need of explicit breaking of the MTH $\mathbb{Z}_2$ symmetry in the dimensionless couplings (i.e. without hard $\mathbb{Z}_2$ breaking). We illustrate how this is possible in a specific baryogenesis setup, which also leads to ADM. In the simplest scenario we obtain $m_{\rm DM}\sim O(1)$GeV, just above the proton mass. We show estimates for direct detection rates at present and future experiments.

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arXiv2022

Form Factors in Higgs Couplings from Physics Beyond the Standard Model

We consider the momentum-dependent effects in Higgs couplings generated by physics beyond the standard model. We take a model-dependent approach, in which we can fully compute the non-local effects from physics not directly reachable by the LHC energy. We consider several scenarios, including composite Higgs models, additional scalars, and the continuum contributions of a quasi-conformal sector, as examples. For each specific model, we are able to obtain the form factor, with which it is then possible to fully simulate the effects in kinematics distributions. The momentum-dependent effects appear as a consequence of off-shellness in the process. We show how the sensitivity of different channels to the various models depends on how the flow of off-shellness appears in the Higgs couplings.

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arXiv2018

Displaced Vertices from Hidden Glue

We consider the phenomenology of glueball production and decay in theories with hidden glue. We focus on the case of folded supersymmetry (FSUSY) , where there is an unbroken $SU(3)$ gauge theory in the absence of light matter, leading to the formation of glueballs. We study their production through the annihilation of folded squarks into hidden gluons at the LHC, and model their fragmentation into glueballs. We obtain the distribution of displaced vertices, which is directly determined by the folded squark mass scale. Although here we specifically apply it to FSUSY, the procedure to model the hidden glue fragmentation into glueballs can be generalized to other similar theories.

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arXiv2015

Scalar Leptons in Folded Supersymmetry

Folded supersymmetry is a natural theory of the electroweak scale in which the scalar top partner responsible for canceling the ultraviolet sensitivity of the Higgs mass at one loop carries no color. As a result, bounds on naturalness on these theories are more relaxed than in typical supersymmetric models, since collider bounds on top partners are less stringent. Here we consider the lepton sector of these theories. We show that a natural realization in a five-dimensional completion requires the existence of scalar leptons with weak scale masses and study their phenomenology. We derive bounds on the masses of these sleptons from the LHC data at $\sqrt{s}=8~$TeV and study the sensitivity of the $\sqrt{s}=13~$TeV run for various integrated luminosities. When supersymmetry is broken exclusively by Scherk-Schwarz boundary conditions the sleptons are stable on collider scales. This leads to bounds on the folded sleptons that translate into masses above $1~$TeV for the folded stops resulting in tuning. When additional sources of supersymmetry breaking, which may be necessary to ensure electroweak symmetry breaking, are allowed the bounds on stops are mostly avoided. On the other hand, these terms lead to faster slepton decays resulting in interesting signals with highly displaced vertices and multi-jet final states inside the detectors.

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arXiv2015

Colorless Top Partners, a 125 GeV Higgs, and the Limits on Naturalness

Theories of physics beyond the Standard Model that address the hierarchy problem generally involve top partners, new particles that cancel the quadratic divergences associated with the Yukawa coupling of the Higgs to the top quark. With extensions of the Standard Model that involve new colored particles coming under strain from collider searches, scenarios in which the top partners carry no charge under the strong interactions have become increasingly compelling. Although elusive for direct searches, these theories predict modified couplings of the Higgs boson to the Standard Model particles. This results in corrections to the Higgs production and decay rates that can be detected at the Large Hadron Collider (LHC) provided the top partners are sufficiently light, and the theory correspondingly natural. In this paper we consider three theories that address the little hierarchy problem and involve colorless top partners, specifically the Mirror Twin Higgs, Folded Supersymmetry, and the Quirky Little Higgs. For each model we investigate the current and future bounds on the top partners, and the corresponding limits on naturalness, that can be obtained from the Higgs program at the LHC. We conclude that the LHC will not be able to strongly disfavor naturalness, with mild tuning at the level of about one part in ten remaining allowed even with 3000 fb$^{-1}$ of data at 14 TeV.

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arXiv2014

Fermion Resonances in Quiver Theories with a pNGB Higgs

Hierarchical quiver models can be used to build theories of electroweak symmetry breaking and natural models of flavor with a pseudo--Nambu-Goldstone boson (pNGB) Higgs. They are cousins of similar models in extra-dimensional theories in anti--de Sitter backgrounds, and can be obtained from them by coarse deconstruction. We consider the fermion excitations in these models, focusing on the quark sector and studying its generic features and phenomenology. We show that, unlike in the continuum case, the spectrum is strongly flavor dependent. To study the phenomenology of the quark excitations we compute their couplings to the Higgs sector and the gauge excitations which determine both their single-production and their decays. We show how the generic features of quiver theories with a pNGB Higgs translate, through the spectrum of quark excitations and their couplings, into a distinct phenomenology at the LHC.

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arXiv2013

Resonances from Quiver Theories at the LHC

We consider the collider signals of spin-one resonances present in full-hierarchy quiver theories of electroweak symmetry breaking. These four-dimensional theories result from the deconstruction of warped extra dimensional models and have very distinct phenomenological features when the number of sites is small. We study a class of generic scenarios in these theories where the color gauge group as well as the electroweak sector, propagate in the quiver diagram. These scenarios correspond to various specific models of electroweak symmetry breaking and fermion masses. We focus on the minimum resonant content and its main features: the presence of heavy and narrow spin one resonances. We derive bounds from the LHC data on the color-octet and color-singlet excited gauge bosons from their decays to jets and top pairs, and show their dependence on the number of sites in the quiver. We also compare them with the bounds derived from flavor violation.

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arXiv2012

Full-hierarchy Quiver Theories of Electroweak Symmetry Breaking and Fermion Masses

We consider quiver theories in four dimensions with a large ultra-violet cutoff. These theories require that an ordered set of vacuum expectation values for the link fields develops dynamically and can be obtained from the coarse deconstruction of extra-dimensional theories in an AdS background. These full-hierarchy quiver theories form a large class which include AdS$_5$ models as a limit, but which have a distinctive phenomenology. As an example, in this paper we show that fermions can be introduced in a way that can at the same time generate the fermion mass hierarchy and have flavor violation consistent with experimental bounds, when the mass scale of the color-octect gauge excitation is above $3 {\rm TeV}$. We also show that electroweak precision constraints are satisfied by this mass scale, without the need to extend the gauge sector to protect against custodial violation.

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arXiv2012

Is the LHC Observing the Pseudo-scalar State of a Two-Higgs Doublet Model ?

The ATLAS and CMS collaborations have recently shown data suggesting the presence of a Higgs boson in the vicinity of 125 GeV. We show that a two-Higgs doublet model spectrum, with the pseudo-scalar state being the lightest, could be responsible for the diphoton signal events. In this model, the other scalars are considerably heavier and are not excluded by the current LHC data. If this assumption is correct, future LHC data should show a strengthening of the $γγ$ signal, while the signals in the $ZZ^{(*)}\to 4\ell $ and $WW^{(*)}\to 2\ell 2ν$ channels should diminish and eventually disappear, due to the absence of diboson tree-level couplings of the CP-odd state. The heavier CP-even neutral scalars can now decay into channels involving the CP-odd light scalar which, together with their larger masses, allow them to avoid the existing bounds on Higgs searches. We suggest additional signals to confirm this scenario at the LHC, in the decay channels of the heavier scalars into $AA$ and $AZ$. Finally, this inverted two-Higgs doublet spectrum is characteristic in models where fermion condensation leads to electroweak symmetry breaking. We show that in these theories it is possible to obtain the observed diphoton signal at or somewhat above of the prediction for the standard model Higgs for the typical values of the parameters predicted.

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arXiv2011

Two Higgs Doublets from Fermion Condensation

We consider the most generic situation in models where the electroweak symmetry is broken by the condensation of a strongly coupled fermion sector, such as for instance a fourth generation. We study the scalar content resulting from the condensation of both the up and the down type fermions, corresponding to a two-Higgs doublet model. We estimate the scalar spectrum using the Nambu--Jona-Lasinio model, improved by the renormalization group. We show that the scalar spectrum is generically lighter than for the case with only one right-handed fermion condensing and that due to a remnant Peccei-Quinn symmetry the lightest state is the pseudo-scalar, with masses ranging typically from 10 GeV to 120 GeV. We discuss the phenomenological consequences of this distinct spectrum.

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arXiv2010

New Strongly Coupled Sector at the Tevatron and the LHC

We examine the possibility that a new strong interaction is accessible to the Tevatron and the LHC. In an effective theory approach, we consider a scenario with a new color-octet interaction with strong couplings to the top quark, as well as the presence of a strongly coupled fourth-generation which could be responsible for electroweak symmetry breaking. We apply several constraints, including the ones from flavor physics. We study the phenomenology of the resulting parameter space at the Tevatron, focusing on the the forward-backward asymmetry in top pair production, as well as in the production of the fourth-generation quarks. We show that if the excess in the top production asymmetry is indeed the result of this new interaction, the Tevatron could see the first hints of the strongly coupled fourth-generation quarks. Finally, we show that the LHC with $\sqrt{s}=7~$TeV and $1~{\rm fb}^{-1}$ integrated luminosity should observe the production of fourth-generation quarks at a level at least one order of magnitude above the QCD prediction for the production of these states.

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arXiv2010

The Lepton Sector of a Fourth Generation

In extensions of the standard model with a heavy fourth generation one important question is what makes the fourth-generation lepton sector, particularly the neutrinos, so different from the lighter three generations. We study this question in the context of models of electroweak symmetry breaking in warped extra dimensions, where the flavor hierarchy is generated by the localization of the zero-mode fermions in the extra dimension. In this setup the Higgs sector is localized near the infrared brane, whereas the Majorana mass term is localized at the ultraviolet brane. As a result, light neutrinos are almost entirely Majorana particles, whereas the fourth generation neutrino is mostly a Dirac fermion. We show that it is possible to obtain heavy fourth-generation leptons in regions of parameter space where the light neutrino masses and mixings are compatible with observation. We study the impact of these bounds, as well as the ones from lepton flavor violation, on the phenomenology of these models.

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