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Werner Porod

Publications and source records attributed to Werner Porod.

At least 19 recordsLinked to original sources

Dark matter in composite Higgs models with a scotogenic EFT

We discuss a class of Composite Higgs models with a fermionic UV completion that can explain the dark matter relic density. The resulting low-energy theory resembles so-called scotogenic models. A residual $\mathbb{Z}_2$ symmetry implies that one of the pseudo-Nambu-Goldstone bosons is stable and therefore is a viable dark matter candidate. As a concrete example, we take a model based on the $\mathrm{SU}(6)/\mathrm{Sp}(6)$ coset, which in principle contains four dark matter candidates. However, only three of them can produce a relic density consistent with observations. We perform a MCMC study focusing on dark matter observables to explore the available parameter space of the effective theory. In particular, we find that spin-1 resonances play an important role in a substantial part of the parameter space. Finally, we comment on possible LHC signatures of this model class.

hep-ph

BSMArt 2: simpler and faster parameter space scans

We present version 2 of BSMArt, a powerful yet lightweight scanning tool designed to simplify the exploration of parameter spaces of new physics models. Aside from architectural improvements, simpler installation and expanded documentation with examples, the new version includes additional tools and new machine learning and Monte Carlo scanning algorithms: Affine MC, Contour Finding, MLScanner, DLScanner, MLS, and CMA-ES. We showcase two variants of CMA-ES scans with physics applications relevant for soft lepton excesses at the LHC. We demonstrate that it is easily possible to find diverse and interesting parameter points for future testing.

hep-ph

Composite top partners in exotic colour representations

Composite Higgs models with partial compositeness generically predict coloured fermionic resonances associated with the strong dynamics responsible for electroweak symmetry breaking. While most phenomenological studies have focused on colour-triplet and colour-octet top partners, several UV-complete hypercolour constructions also contain fermionic colour sextets. We present a systematic study of these states in the minimal model classes where they arise, constructing the relevant low-energy interactions and deriving their characteristic decay patterns. The sextets predominantly decay through coloured pseudo-Nambu-Goldstone bosons, leading to top-rich final states, while additional channels with $b$-jets and missing transverse energy can be important. We reinterpret existing ATLAS and CMS searches for high-multiplicity final states to derive the dedicated constraints on these resonances. For the benchmark spectra considered, current LHC data exclude individual sextet components up to masses in the $2-2.5$ TeV regime, with stronger bounds when the full sextet multiplet is included, while conservative extrapolations to the HL-LHC indicate a reach close to $3$ TeV. Our results therefore show that colour-sextet fermions provide a powerful and largely unexplored probe of composite Higgs models with partial compositeness.

hep-ph

Surveying the theory space of pion dark matter

We use a holographic model to survey the space of strongly coupled SU(Nc) gauge dynamics with QCD-like chiral symmetry breaking pattern for quarks in the fundamental representation. We systematically identify the light degrees of freedom (rho, sigma and pi mesons) that would make up the dark sector as a function of Nf, Nc and a common quark mass scale. We identify seven distinct effective theories that are of interest to explore and make a first summary of the expected dark matter phenomenology. Amongst our results we conclude that QCD-like models where the low energy theory is described purely in terms of pions struggle to generate a large enough Mpi/fpi value so these theories will need extra relic density generation mechanisms to be viable. The largest space of models (with an intermediate quark mass) have both the sigma and rho lying below 2 Mpi and are largely unexplored in the literature so far. Regions with just one of rho or sigma light are possible in constrained parameter regions. These states aid the pion relic density generation as needed for valid theories. The sigma always lies above the pi mass becoming degenerate with the pi in the extreme walking limit.

hep-ph

Hunting and identifying coloured resonances in four top events with machine learning

We study prospects to search for pair or singly produced colour octet or colour sextet scalars which decay into two top quarks at the LHC. We focus on the same-sign lepton final state. We train a neural network comprising a simple multilayer perceptron combined with a convolutional neural network to optimize the separation of signal and background events. For LHC operated at 14 TeV and a luminosity of 3 ab$^{-1}$ we find an expected discovery reach of $m_8=1.8$ TeV and $m_6=1.92$ TeV for pair produced colour octets and sextets, respectively, and an expected exclusion reach of $m_8=2.02$ TeV and $m_6=2.14$ TeV. In a second step, we retrain the same network architecture to discriminate between signal processes. The network can clearly distinguish between the different colour representations. Moreover, we can also determine whether there is a significant contribution from single production to pair production for the same final state. The methodology can be applied to BSM candidates of different spin and colour representations.

hep-ph

Exploring Scotogenic Parameter Spaces and Mapping Uncharted Dark Matter Phenomenology with Multi-Objective Search Algorithms

We present a novel artificial intelligence approach to explore beyond Standard Model parameter spaces by leveraging a multi-objective optimisation algorithm. We apply this methodology to a non-minimal scotogenic model which is constrained by Higgs mass, anomalous magnetic moment of the muon, dark matter relic density, dark matter direct detection, neutrino masses and mixing, and lepton flavour violating processes. Our results successfully expand on the phenomenological realisations presented in previous work. We compare between multi- and single-objective algorithms and we observe more phenomenologically diverse solutions and an improved search capacity coming from the former. We use novelty detection to further explore sparsely populated regions of phenomenological interest. These results suggest a powerful search strategy that combines the global exploration of multi-objective optimisation with the exploitation of single-objective optimisation.

hep-ph

Electroweak spin-1 resonances in Composite Higgs models

Composite Higgs models predict the existence of various bound states. Among these are spin-1 resonances. We investigate models containing $\text{SU(2)}_L\times \text{SU(2)}_R$ as part of the unbroken subgroup in the new strong sector. These models predict that there are two neutral and one charged spin-1 resonances mixing sizably with the SM vector bosons. As a consequence, these can be singly produced in Drell-Yan processes at the LHC. We explore their rich LHC phenomenology and show that there are still viable scenarios consistent with existing LHC data where the masses of these states can be as low as about 1.5 TeV.

hep-ph

Predictions for Composite Higgs models from gauge/gravity dualities

Gauge/gravity dualities provide a very useful approach into solving strongly coupled systems. We apply this to Composite Higgs models and determine the mass hierarchies of the corresponding bound states. As a cross check we apply this to QCD and compare the results to existing lattice calculations for which we find good agreement. We then focus on a particular example whose phenomenology has recently been studied in the literature in a generic way and outline first phenomenological implications of our findings for the spectrum.

hep-ph

Holography for Sp(2$N_c$) Gauge Dynamics: from Composite Higgs to Technicolour

We study Sp(2$N_c$) gauge dynamics with two Dirac fermion flavours in the fundamental representation. These strongly coupled systems underlie some composite Higgs models with a global symmetry breaking pattern SU(4)$\rightarrow$Sp(4), leading to a light quartet of pseudo-Goldstone bosons that can play the role of the Higgs. Including four-fermion interactions can rotate the vacuum to a technicolour breaking pattern. Using gauge/gravity duality, we study the underlying gauge dynamics. Our model incorporates the $N_c$-specific running of the fermion anomalous dimension and can thus distinguish between specific gauge groups. We determine the bound-state spectrum of the UV SU(4)$\rightarrow$Sp(4) symmetry breaking model, also including fermion masses and mass splitting, and display the $N_c$ dependence. The inclusion of a four-fermion interaction shows the emergence of three Goldstone bosons on the path to technicolour dynamics.

hep-ph

Coloured spin-1 states in composite Higgs models

Strong dynamics for composite Higgs models predict spin-1 resonances which are expected to be in the same mass range as the usually considered top-partners. We study here QCD-coloured vector and axial-vector states stemming from composite Higgs dynamics in several relevant models based on an underlying gauge-fermion description. These states can come as triplet, sextet and octet representation. All models considered have a colour octet vector state in common which can be singly produced at hadron colliders as it mixes with the gluon. We explore the rich and testable phenomenology of these coloured spin-1 states at the LHC and future colliders.

hep-ph

Split NMSSM from dimensional reduction of a $10D$, $\mathcal{N}=1$, $E_8$ theory over a modified flag manifold

We review the Standard Model extension that results from the dimensional reduction of a $10D$, $\mathcal{N}=1$, $E_8$ gauge theory over the $M_4 \times SU(3)/U(1) \times U(1) \times \mathbf{Z}_3 $ space, which leads to a $4D$, $\mathcal{N}=1$, $SU(3)^3\times U(1)^2$ theory. Below the unification scale we obtain a Split NMSSM effective theory. The third generation quark and light Higgs masses are within the experimental limits at 2-loop level and the neutralino LSP mass is predicted $<800$ GeV.

hep-ph

On interplay between flavour anomalies and neutrino properties

A minimal extension of the Standard Model (SM) featuring two scalar leptoquarks, an SU(2) doublet with hypercharge 1/6 and a singlet with hypercharge 1/3, is proposed as an economical benchmark model for studies of an interplay between flavour physics and properties of the neutrino sector. The presence of such type of leptoquarks radiatively generates neutrino masses and offers a simultaneous explanation for the current B-physics anomalies involving $b \to c \ell ν_\ell$ decays. The model can also accommodate both the muon magnetic moment and the recently reported $W$ mass anomalies, while complying with the most stringent lepton flavour violating observables.

hep-ph

MHz to TeV expectations from scotogenic WIMP dark matter

The indirect search for dark matter is typically restricted to individual photon bands and instruments. In the context of multiwavelength observations, finding a weak signal in large fore- and backgrounds at only one wavelength band is hampered by systematic uncertainties dominating the signal strength. Dark matter particle annihilation is producing Standard Model particles of which the prompt photon emission is searched for in many studies. However, also the secondary emission of charged particles from dark matter annihilation in the TeV range results in comparable or even stronger fluxes in the GHz-GeV range. In this study, we calculate the prompt and secondary emission of a scotogenic WIMP with a mass of $1\,\mathrm{TeV}$ in 27 dwarf galaxies of the Milky Way. For the secondary emission, we include Inverse Compton scattering, bremsstrahlung, and synchrotron radiation, which results in a "triple hump" structure characteristic for only dark matter and no other astrophysical source. In order to determine the best candidates for multi-instrument analyses, we estimate the diffuse emission component of the Milky Way itself, including its own dark matter halo from the same scotogenic WIMP model. We find signal-to-background ratios of individual sources on the order of $10^{-3}$-$10^{-2}$ across X- to $γ$-rays assuming $J$-factors for the cold dark matter distribution inferred from observations and no additional boosting due to small-scale clumping. We argue that a joint multi-wavelength analysis of all nearby galaxies as well as the extension towards the Cosmic Gamma-ray Background is required to disentangle possible dark matter signals from astrophysical back- and foregrounds.

astro-ph.HE

Split NMSSM from dimensional reduction of a $10D$, $\mathcal{N}=1$ $E_8$ over $SU(3)/U(1)\times U(1)\times Z_3$

We examine an extension of the Standard Model which results from a $10D$, $\mathcal{N}=1$, $E_8$ gauge theory. The theory is dimensionally reduced over a $M_4 \times B_0/ \mathbf{Z}_3 $ space, where $B_0$ is the nearly-Kähler manifold $SU(3)/U(1) \times U(1)$ and $\mathbf{Z}_3$ is a freely acting discrete group on $B_0$ that triggers a Wilson flux breaking, leading to an $\mathcal{N}=1$, $SU(3)^3\times U(1)^2$ effective theory in $4D$. At lower energies we are left with the Split NMSSM. Its 2-loop analysis yields third generation quark and light Higgs masses within the experimental limits and predicts a neutralino LSP mass $<800$ GeV.

hep-ph

Hunting scalar partners of the Higgs boson at the LHC

Composite Higgs models with a fermionic ultraviolet completion predict in general additional pseudo Nambu Goldstone bosons beside the Higgs multiplet. In this contribution we discuss their LHC signatures and present first bounds in simplified models which can also be applied to generic models like multi-Higgs models. We then demonstrate how these can be combined taking a concrete model based on the SU(5)/SO(5) coset as an example. We use this to show how a proper combination of different channels can lead to an improved bound compared to a single channel analysis.

hep-ph

Uncovering doubly charged scalars with dominant three-body decays using machine learning

We propose a deep learning-based search strategy for pair production of doubly charged scalars undergoing three-body decays to $W^+ t\bar b$ in the same-sign lepton plus multi-jet final state. This process is motivated by composite Higgs models with an underlying fermionic UV theory. We demonstrate that for such busy final states, jet image classification with convolutional neural networks outperforms standard fully connected networks acting on reconstructed kinematic variables. We derive the expected discovery reach and exclusion limit at the high-luminosity LHC.

hep-ph

Holographic Non-Abelian Flavour Symmetry Breaking

We investigate a holographic model for both spontaneous and explicit symmetry breaking of non-abelian flavour symmetries. This consists of a bottom-up model inspired by the top-down D3/D7 probe brane model that incorporates the running anomalous dimensions of the fields. We ensure that in the holographic bulk, the full non-abelian flavour symmetries for massless quarks are present. The quark masses are spontaneously generated field values in the bulk and there is a resultant bulk Higgs mechanism. We provide a numerical technique to find the mass eigenvalues for a system of coupled holographic fields. We test this approach using an analytic model of ${\cal N}=2$ supersymmetric matter. We apply this approach to two-flavour QCD with both $u-d$ quark mass splitting and multi-trace bulk action terms that are expected to break $U(N_f)_V$ to $SU(N_f)_V \times U(1)_V$ away from large $N_c$. We also discuss three-flavour QCD with strange quark mass splitting and applications to more exotic symmetry breaking patterns of potential relevance for composite Higgs models.

hep-th

TF08 Snowmass Report: BSM Model Building

We summarize the state of Beyond the Standard Model (BSM) model building in particle physics for Snowmass 2021, focusing mainly on several whitepaper contributions to BSM model building (TF08) and closely related areas.

hep-ph