Search

We study supercooled first-order phase transitions above the QCD scale in a wide class of conformal Majoron-like U(1)' models that explain the totality of active neutrino oscillation data and produce a detectable stochastic gravitational wave background (SGWB) at LIGO, LISA and ET. We place constraints on the U(1)' breaking scale and gauge coupling using current LIGO-Virgo-Kagra data. We find that strong supercooling can be ruled out in large regions of parameter space if a SGWB is not detected by these experiments. A null signal at LIGO and ET will disfavor a type-I seesaw scale above $10^{14}$ GeV, while a positive signal is a signature of heavy right-handed neutrinos. On the other hand, LISA will be sensitive to seesaw scales as low as a TeV, and could detect a SGWB even if the right-handed neutrinos are decoupled., Comment: 50 pages, 25 figures, 3 tables

We study the Higgs boson decay into dark matter (DM) in the framework of freeze-in at stronger coupling. Even though the Higgs-DM coupling is significant, up to order one, DM does not thermalize due to the Boltzmann suppression of its production at low temperatures. We find that this mechanism leads to observable Higgs decay into invisible final states with the branching fraction of 10% and below, while producing the correct DM relic abundance. This applies to the DM masses down to the MeV scale, which requires a careful treatment of the hadronic production modes. For DM masses below the muon threshold, the Boltzmann suppression is not operative and the freeze-in nature of the production mechanism is instead guaranteed by the smallness of the electron Yukawa coupling. As a result, MeV DM with a significant coupling to the Higgs boson remains non-thermal as long as the reheating temperature does not exceed $\mathcal{O}(100)\;$MeV. Our findings indicate that there are good prospects for observing light non-thermal DM via invisible Higgs decay at the LHC and FCC., Comment: 23 pages, 9 figures, formulas corrected

Searches for new physics (NP) at particle colliders typically involve multivariate analysis of kinematic distributions of final state particles produced in a decay of a hypothetical NP resonance. Since the pair-production cross-sections mediated by such resonances are strongly suppressed by the NP scale, this analysis becomes less relevant for NP searches for masses of the BSM resonance above 1 TeV. On the other hand, $t$-channel processes are less sensitive to the mass of the virtual mediator and therefore larger phase-space can be potentially probed as well as the couplings between the NP particles and the Standard Model fields. The fact that transitions between different generations of quarks and leptons may exist, the potential of the search presented in this article can be used, as a reference guide, to enlarge significantly the scope of searches performed at the LHC to flavour off-diagonal channels, in a theoretically consistent approach. In this work, we study non-resonant production of scalar leptoquarks which have been proposed in the literature to provide a potential avenue for radiative generation of neutrino masses, accommodating as well the existing flavour physics data. Final states involving just two muons at the LHC ($\mu^+, \mu^-$), are used as a well-motivated case study., Comment: v1: 26 pages; 8 figures; 4 tables; v2: Additional discussion and references

We study a simple extension of the Standard Model featuring a dark sector with an ultralight pseudo Nambu-Goldstone boson as dark matter candidate. We focus on the mass range $\mathcal{O}(10^{-20} - 10^{-10})$ eV, relevant for strong gravity applications, and explore its production and evolution in the early Universe. The model is formulated in such a way that dark matter does not couple directly to photons or other Standard Model particles avoiding some of the most stringent cosmological bounds related to axion-like particles. In this work, two different scenarios are considered depending on whether dark matter is produced in a pre-inflationary or post-inflationary regime. We also discuss the effect from emergent topological defects such as cosmic strings and domain walls, and estimate the spectrum of stochastic gravitational waves produced by their decay, enabling to test the model at current and future gravitational-wave experiments., Comment: 22 pages, 5 figures

We propose a framework to account for neutrino masses at the two-loop level. This mechanism introduces new scalars and Majorana fermions to the Standard Model. It is assumed the existence of a global $\mathrm{U(1)\times \mathcal{Z}_2}$ symmetry which after partial breaking provides the stability of the dark matter candidates of the theory. The rich structure of the potential allows for the possibility of first-order phase transitions (FOPTs) in the early Universe which can lead to the generation of primordial gravitational waves as one of the potentially observable signatures of this model. Taking into account relevant constraints from lepton flavour violation, neutrino physics as well as the trilinear Higgs couplings at next-to-leading order accuracy, we have found a wide range of possible FOPTs which are strong enough to be probed at the proposed gravitational-wave interferometer experiments such as LISA., Comment: 24 pages; 7 figures; 2 tables. v2: Additional references; v3: Missing interactions added. Extended dark matter analysis and additional discussion added; v4: Extended discussion and additional clarifications. Matches version to be published in PRD; v5: Final version. Miscellaneous changes (affliations and funding information)

We formulate a version of the low-scale Majoron model equipped with an inverse seesaw mechanism featuring lepton-number preserving dimension-6 operators in the scalar potential. Contrary to its dimension-4 counterpart, we find that the model can simultaneously provide light and ultralight Majorons, neutrino masses and their mixing, while featuring strong first-order cosmological phase transitions associated to the spontaneous breaking of the lepton number and the electroweak symmetries in the early Universe. We show by a detailed numerical analysis that under certain conditions on the parameter space accounted for in collider physics, the model can be probed via the primordial gravitational wave spectrum potentially observable at LISA and other planned facilities., Comment: Updated invisible Higgs decays constraints, references added, 29 pages, 7 figures

In this work, we propose and explore for the first time a new collider signature of heavy neutral scalars typically found in many distinct classes of multi-Higgs models. This signature, particular relevant in the context of the Large Hadron Collider (LHC) measurements, is based on a topology with two charged leptons and four jets arising from first and second generation quarks. As an important benchmark scenario of the multi-Higgs models, we focus on a recently proposed Branco-Grimus-Lavoura (BGL) type model enhanced with an abelian U(1) flavour symmetry and featuring an additional sector of right-handed neutrinos. We discuss how kinematics of the scalar fields in this model can be used to efficiently separate the signal from the dominant backgrounds and explore the discovery potential of the new heavy scalars in the forthcoming LHC runs. The proposed method can be applied for analysis of statistical significance of heavy scalars' production at the LHC and future colliders in any multi-Higgs model., Comment: 30 pages, 8 tables, 13 figures; v2: Various corrections and additional discussions. Matches version to be published in PRD

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 $b \to c \ell \nu_\ell$ 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., Comment: Accepted version

In this work, we continue our exploration of TeV-scale vector-like fermion signatures inspired by a Grand Unification scenario based on the trinification gauge group. A particular focus is given to pair-production topologies of vector-like quarks (VLQs) at the LHC, in a multi-jet plus a charged lepton and a missing energy signature. We employ Deep Learning methods and techniques based in evolutive algorithms that optimize hyper-parameters in the neural network construction, whose objective is to maximise the Asimov estimate for distinct VLQ masses. In this article, we consider the implications of an innovative approach by simultaneously combining detector images (also known as jet images) and tabular data containing kinematic information from the final states. With this technique we are able to exclude VLQs, that are specific for the considered model, to up a mass of 800 GeV in both the high-luminosity the Run-III phases of the LHC programme., Comment: 24 pages, 4 tables and 8 figures. Matches version to be published in EPJC

We suggest an appealing strategy to probe a large class of scenarios beyond the Standard Model simultaneously explaining the recent CDF II measurement of the $W$ boson mass and predicting first-order phase transitions (FOPT) testable in future gravitational-wave (GW) experiments. Our analysis deploys measurements from the GW channels and high energy particle colliders. We discuss this methodology focusing on the specific example provided by an extension of the Standard Model of particle physics that incorporates an additional scalar $\mathrm{SU}(2)_{\rm L}$ triplet coupled to the Higgs boson. We show that within this scenario a strong electroweak FOPT is naturally realised consistently with the measured $W$ boson mass-shift. Potentially observable GW signatures imply the triplet mass scale to be TeV-ish, consistently with the value preferred by the $W$ mass anomaly. This model can be tested in future space-based interferometers such as LISA, DECIGO, BBO, TianQin, TAIJI projects and in future colliders such as FCC, ILC, CEPC., Comment: 6 pages, 4 figures; references added; discussion extended; full numerical analysis including one-loop corrections performed in support of initial claims; two extra figures with parameter scan results and SNR for LISA added; included an author that, due to an unfortunate editing mistake in the first version was accidentally not included; conclusions unchanged; acknowledgments extended

A chiral-symmetric technicolor model successfully reconciles the tension between electroweak precision tests and traditional technicolor models. Focusing on its simplest realization preserving the conventional Higgs mechanism, we study its primordial gravitational wave signatures originating from first order phase transitions in the early Universe. We found that abundant phase transition patterns arise from a physically viable parameter space. Besides, we have also found gravitational wave signals possibly visible by future experiments, such as LISA, BBO and u-DECIGO. Our results stress the importance of gravitational wave detectors in exploring new physics complementary to ground colliders in the multi-messenger astronomy era., Comment: 9 pages, 6 figures, 3 tables; accepted for publication in Phys. Lett. B

Current gravitational wave (GW) detections rely on the existence of libraries of theoretical waveforms. Consequently, finding new physics with GWs requires libraries of non-standard models, which are computationally demanding. We discuss how deep learning frameworks can be used to generate new waveforms "learned" from a simulation dataset obtained, say, from numerical relativity simulations. Concretely, we use the WaveGAN architecture of a generative adversarial network (GAN). As a proof of concept we provide this neural network (NN) with a sample of ($>500$) waveforms from the collisions of exotic compact objects (Proca stars), obtained from numerical relativity simulations. Dividing the sample into a training and a validation set, we show that after a sufficiently large number of training epochs the NN can produce from 12\% to 25\% of the synthetic waveforms with an overlapping match of at least 95\% with the ones from the validation set. We also demonstrate that a NN can be used to predict the overlapping match score, with 90\% of accuracy, of new synthetic samples. These are encouraging results for using GANs for data augmentation and interpolation in the context of GWs, to cover the full parameter space of, say, exotic compact binaries, without the need of intensive numerical relativity simulations., Comment: 20 pages, 13 figures, 4 tables

In this paper, we present several possible anomaly-free implementations of the Branco-Grimus-Lavoura (BGL) model with two Higgs doublets and one singlet scalar. The model also includes three generations of massive neutrinos that get their mass via a type-I seesaw mechanism. A particular anomaly-free realization, which we dub $\nu$BGL-1 scenario, is subjected to an extensive phenomenological analysis, from the perspective of flavour physics and collider phenomenology., Comment: 32 pages, 9 Figures and 7 tables. Matches version to be published in PRD

In this work we discuss two different phases of a complex singlet extension of the Standard Model (SM) together with an extension that also includes new fermion fields, in particular, a Majoron model equipped with an inverse seesaw mechanism. All considered scenarios contain a global $\mathrm{U}(1)$ symmetry and allow for first-order phase transitions while only two of them are strong enough to favour the detection of primordial gravitational waves (GWs) in planned experiments such as LISA. In particular, this is shown to be possible in the singlet extension with a non vanishing real VEV at zero temperature and also in the model with extra fermions. In the singlet extension with no additional fermions, the detection of GWs strongly depends on the $\mathrm{U}(1)$ symmetry breaking pattern of the scalar potential at zero temperature. We study for the first time the impact of the precision in the determination of the SM parameters on the strength of the GWs spectrum. It turns out that the variation of the SM parameters such as the Higgs boson mass and top quark Yukawa coupling in their allowed experimental ranges has a notable impact on GWs detectability prospects., Comment: 28 pages, 13 figures

The discovery potential of both singlet and doublet vector-like leptons (VLLs) at the Large Hadron Collider (LHC) as well as at the not-so-far future muon and electron machines is explored. The focus is on a single production channel for LHC direct searches while double production signatures are proposed for the leptonic colliders. A Deep Learning algorithm to determine the discovery (or exclusion) statistical significance at the LHC is employed. While doublet VLLs can be probed up to masses of 1 TeV, their singlet counterparts have very low cross sections and can hardly be tested beyond a few hundreds of GeV at the LHC. This motivates a physics-case analysis in the context of leptonic colliders where one obtains larger cross sections in VLL double production channels, allowing to probe higher mass regimes otherwise inaccessible even to the LHC high-luminosity upgrade., Comment: 26 pages, 11 figures, 10 tables, Published version

We propose a model with two Higgs doublets and several $SU(2)$ scalar singlets with a global non-Abelian flavor symmetry $\mathcal{Q}_6\times\mathcal{Z}_2$. This discrete group accounts for the observed pattern of fermion masses and mixing angles after spontaneous symmetry breaking. In this scenario only the third generation of fermions get their masses as in the Standard Model (SM). The masses of the remaining fermions are generated through a seesaw-like mechanism. To that end, the matter content of the model is enlarged by introducing electrically charged vector-like fermions (VLFs), right handed Majorana neutrinos and several SM scalar singlets. Here we study the processes involving VLFs that are within the reach of the Large Hadron Collider (LHC). We perform collider studies for vector-like leptons (VLLs) and vector-like quarks (VLQs), focusing on double production channels for both cases, while for VLLs single production topologies are also included. Utilizing genetic algorithms for neural network optimization, we determine the statistical significance for a hypothetical discovery at future LHC runs. In particular, we show that we can not safely exclude VLLs for masses greater than $200~\mathrm{GeV}$. For VLQ's in our model, we show that we can probe their masses up to 3.8 TeV, if we take only into account the high-luminosity phase of the LHC. Considering Run-III luminosities, we can also exclude VLQs for masses up to $3.4~\mathrm{TeV}$. We also show how the model with predicted VLL masses accommodates the muon anomalous magnetic moment., Comment: 32 pages,16 figures. Additional references and discussion. Matches version to be published in JHEP

We construct families, and concrete examples, of simple extensions of the Standard Model that can yield ultralight {real or} complex vectors or scalars with potential astrophysical relevance. Specifically, the mass range for these putative fundamental bosons ($\sim 10^{-10}-10^{-20}$ eV) would lead dynamically to both new non-black hole compact objects (bosonic stars) and new non-Kerr black holes, with masses of $\sim M_\odot$ to $\sim 10^{10} M_\odot$, corresponding to the mass range of astrophysical black hole candidates (from stellar mass to supermassive). For each model, we study the properties of the mass spectrum and interactions after spontaneous symmetry breaking, discuss its theoretical viability and caveats, as well as some of its potential and most relevant phenomenological implications {linking them to the} physics of compact objects., Comment: 27 pages, 2 figures

The construction and general implications of a model with complete supersymmetric unification of the Standard Model matter content, interactions and families' replication into a single $E_{8}$ gauge superfield in ten dimensions is presented. The gauge and extended Poincar\'e symmetries are broken through compactification of the $\mathbb{T}^6/(\mathbb{Z}_3\times \mathbb{Z}_3)$ orbifold with Wilson lines, which reduces the original symmetry and matter content into those of the Standard Model plus additional heavier states. Proton decay can be suppressed automatically while the compactification scale may be as low as $10^9~\rm{GeV}$, so that the corresponding GUT-scale physics may be potentially accessible and testable by future collider measurements., Comment: 56 pages, 6 figures. v2: changed the orbifold

A model is presented that achieves unification of the full Standard Model (SM) field content into a single superfield. It has $E_8$ as a gauge group and simple SUSY in ten spacetime dimensions. The extra dimensions are orbifolded such that they reduce the gauge symmetry directly to the SM one. At low energies, only the SM field content remains with viable unified Yukawa couplings. Full unification can be achieved at energies as low as $10^6\ \rm{GeV}$ with controlled proton decay., Comment: 13 pages, 5 figures; descriptions of RG evolution and proton decay have been added, conclusions unchanged

We construct a three-Higgs doublet model with a flavour non-universal ${\rm U}(1)\times \mathbb{Z}_2$ symmetry. That symmetry induces suppressed flavour-changing interactions mediated by neutral scalars. New scalars with masses below the TeV scale can still successfully negotiate the constraints arising from flavour data. Such a model can thus encourage direct searches for extra Higgs bosons in the future collider experiments, and includes a non-trivial flavour structure., Comment: 34 pages, 10 figures, references added

We explore the potential of ultimate unification of the Standard Model matter and gauge sectors into a single $E_8$ superfield in ten dimensions via an intermediate Pati-Salam gauge theory. Through a consistent realisation of a $\mathbb{T}^6/(\mathbb{Z}_6\times \mathbb{Z}_2)$ orbifolding procedure accompanied by the Wilson line breaking mechanism and Renormalisation Group evolution of gauge couplings, we have established several benchmark scenarios for New Physics that are worth further phenomenological exploration., Comment: 18 pages, 1 figure and 4 tables

We explore machine learning methods to detect gravitational waves (GW) from binary black hole (BBH) mergers using deep learning (DL) algorithms. The DL networks are trained with gravitational waveforms obtained from BBH mergers with component masses randomly sampled in the range from 5 to 100 solar masses and luminosity distances from 100 Mpc to, at least, 2000 Mpc. The GW signal waveforms are injected in public data from the O2 run of the Advanced LIGO and Advanced Virgo detectors, in time windows that do not coincide with those of known detected signals. We demonstrate that DL algorithms, trained with GW signal waveforms at distances of 2000 Mpc, still show high accuracy when detecting closer signals, within the ranges considered in our analysis. Moreover, by combining the results of the three-detector network in a unique RGB image, the single detector performance is improved by as much as 70%. Furthermore, we train a regression network to perform parameter inference on BBH spectrogram data and apply this network to the events from the the GWTC-1 and GWTC-2 catalogs. Without significant optimization of our algorithms we obtain results that are mostly consistent with published results by the LIGO-Virgo Collaboration. In particular, our predictions for the chirp mass are compatible (up to 3$\sigma$) with the official values for 90% of events, Comment: 16 pages, 12 figures

In this paper, a model inspired by Grand Unification principles featuring three generations of vector-like fermions, new Higgs doublets and a rich neutrino sector at the low scale is presented. Using the state-of-the-art Deep Learning techniques we perform the first phenomenological analysis of this model focusing on the study of new charged vector-like leptons (VLLs) and their possible signatures at CERN's Large Hadron Collider (LHC). In our numerical analysis we consider signal events for vector-boson fusion and VLL pair production topologies, both involving a final state containing a pair of charged leptons of different flavor and two sterile neutrinos that provide a missing energy. We also consider the case of VLL single production where, in addition to a pair of sterile neutrinos, the final state contains only one charged lepton. All calculated observables are provided as data sets for Deep Learning analysis, where a neural network is constructed, based on results obtained via an evolutive algorithm, whose objective is to maximise either the accuracy metric or the Asimov significance for different masses of the VLL. Taking into account the effect of the three analysed topologies, we have found that the combined significance for the observation of new VLLs at the high-luminosity LHC can range from $5.7\sigma$, for a mass of $1.25~\mathrm{TeV}$, all the way up to $28\sigma$ if the VLL mass is $200~\mathrm{GeV}$. We have also shown that by the end of the LHC Run-III a $200~\mathrm{GeV}$ VLL can be excluded with a confidence of $8.8$ standard deviations. The results obtained show that our model can be probed well before the end of the LHC operations and, in particular, providing important phenomenological information to constrain the energy scale at which new gauge symmetries emergent from the considered Grand Unification picture can be manifest., Comment: 60 pages, 31 figures, 15 tables

Inspired by the recent development in determining the property of the observed Higgs boson, we explore the $CP$-violating (CPV) $- c_{\rm CPV} h W^{+\, \mu\nu}\tilde{W}^{-}_{\mu\nu}/v$ coupling in the Standard Model (SM) and beyond, where $W^{\pm \, \mu \nu}$ and $\tilde{W}^{\pm\,\mu\nu}$ denote the $W$-boson field strength and its dual. To begin with, we show that the leading-order SM contribution to this CPV vertex appears at two-loop level. By summing over the quark flavor indices in the two loop integrals analytically, we can estimate the order of the corresponding Wilson coefficient to be $c^{\rm SM}_{\rm CPV} \sim {\cal O}(10^{-23})$, which is obviously too small to be probed at the LHC and planned future colliders. Then we investigate this CPV $hW^+ W^-$ interaction in two Beyond the Standard Model benchmark models: the left-right model and the complex 2-Higgs doublet model (C2HDM). Unlike what happens for the SM, the dominant contributions in both models arise at the one-loop level, and the corresponding Wilson coefficient can be as large as of ${\cal O}(10^{-9})$ in the former model and of ${\cal O}(10^{-3})$ for the latter. In light of such a large CPV effect in the $hW^+W^-$ coupling, we also give the formulae for the leading one-loop contribution to the related CPV $hZZ$ effective operator in the C2HDM. The order of magnitude of the Wilson coefficients in the C2HDM may be within reach of the high-luminosity LHC or planned future colliders., Comment: 19 pages, 4 figures

We explore a class of models which can provide a common origin for the recently observed evidence for lepton flavor universality violation in $b \to s l^+ l^- $ decays, the dark matter (DM) problem and the long-standing muon $(g-2)$ anomaly. In particular, both anomalies in the $B$ meson decays and the muon $(g-2)$ can be explained by the additional one-loop diagrams with DM candidates. We first classify several simple models according to the new fields' quantum numbers. We then focus on a specific promising model and perform a detailed study of both DM and flavor physics. A random scan over the relevant parameter space reveals that there is indeed a large parameter space which can explain the three new physics phenomena simultaneously, while satisfying all other flavor and DM constraints. Finally, we discuss some of the possible new physics signatures at the Large Hadron Collider., Comment: 33 pages, 8 figures

We propose a low-scale renormalizable trinification theory that successfully explains the flavor hierarchies and neutrino puzzle in the Standard Model (SM), as well as provides a dark matter candidate and also contains the necessary means for efficient leptogenesis. The proposed theory is based on the trinification $\SU{3}{C}\times \SU{3}{L}\times \SU{3}{R}$ gauge symmetry, which is supplemented with an additional flavor symmetry $\U{X}\times Z_{2}^{(1)} \times Z_{2}^{(2)}$. In the proposed model the top quark and the exotic fermions acquire tree-level masses, whereas the lighter SM charged fermions gain masses radiatively at one-loop level. In addition, the light active neutrino masses arise from a combination of radiative and type-I seesaw mechanisms, with the Dirac neutrino mass matrix generated at one-loop level., Comment: Version published in PRD

Given the tremendous phenomenological success of the Standard Model (SM) framework, it becomes increasingly important to understand to what extent its specific structure dynamically emerges from unification principles. In this study, we present a novel anomaly-free supersymmetric (SUSY) Grand Unification model based upon gauge trinification $[\mathrm{SU}(3)]^3$ symmetry and a local $\mathrm{SU}(2)_{\mathrm{F}} \times \mathrm{U}(1)_{\mathrm{F}}$ family symmetry, with particle spectra and gauge symmetries inspired by a possible reduction pattern $\mathrm{E}_8 \to \mathrm{E}_6\times \mathrm{SU}(2)_{\mathrm{F}} \times \mathrm{U}(1)_{\mathrm{F}}$, with subsequent $\mathrm{E}_6\to [\mathrm{SU}(3)]^3$ symmetry breaking step. In this framework, higher-dimensional operators of $\mathrm{E}_6$ induce the threshold corrections in the gauge and Yukawa interactions leading, in particular, to only two distinct Yukawa couplings in the fundamental sector of the resulting $[\mathrm{SU}(3)]^3\times \mathrm{SU}(2)_{\mathrm{F}} \times \mathrm{U}(1)_{\mathrm{F}}$ Lagrangian. Among the appealing features emergent in this framework are the Higgs-matter unification and a unique minimal three Higgs doublet scalar sector at the electroweak scale as well as tree-level hierarchies in the light fermion spectra consistent with those observed in nature. In addition, our framework reveals a variety of prospects for New Physics searches at the LHC and future colliders such as vector-like fermions, as well as rich scalar, gauge and neutrino sectors., Comment: 50 pages, 10 figures, 17 tables; discussion somewhat extended; published version

Tremendous phenomenological success of the Standard Model (SM) suggests that its flavor structure and gauge interactions may not be arbitrary but should have a fundamental first-principle explanation. In this work, we explore how the basic distinctive properties of the SM dynamically emerge from a unified New Physics framework tying together both flavour physics and Grand Unified Theory (GUT) concepts. This framework is suggested by a novel anomaly-free supersymmetric chiral $\mathrm{E}_6 \times \mathrm{SU}_F(2) \times \mathrm{U}_F(1)$ GUT containing the SM. Among the most appealing emergent properties of this theory is the Higgs-matter unification with a highly-constrained massless chiral sector featuring two universal Yukawa couplings close to the GUT scale. At the electroweak scale, the minimal SM-like effective field theory limit of this GUT represents a specific flavored three-Higgs doublet model consistent with the observed large hierarchies in the quark mass spectra and mixing already at tree level., Comment: 11 pages, 2 tables, 1 figure; discussion somewhat extended; published version

The minimal $U(1)_{\rm B-L}$ extension of the Standard Model (B-L-SM) offers an explanation for neutrino mass generation via a seesaw mechanism as well as contains two new physics states such as an extra Higgs boson and a new $Z^\prime$ gauge boson. The emergence of a second Higgs particle as well as a new $Z^\prime$ gauge boson, both linked to the breaking of a local $U(1)_{\rm B-L}$ symmetry, makes the B-L-SM rather constrained by direct searches at the Large Hadron Collider (LHC) experiments. We investigate the phenomenological status of the B-L-SM by confronting the new physics predictions with the LHC and electroweak precision data. Taking into account the current bounds from direct LHC searches, we demonstrate that the prediction for the muon $(g-2)_\mu$ anomaly in the B-L-SM yields at most a contribution of approximately $8.9 \times 10^{-12}$ which represents a tension of $3.28$ standard deviations, with the current $1\sigma$ uncertainty, by means of a $Z^\prime$ boson if its mass lies in a range of $6.3$ to $6.5$ TeV, within the reach of future LHC runs. This means that the B-L-SM, with heavy yet allowed $Z^\prime$ boson mass range, in practice does not resolve the tension between the observed anomaly in the muon $(g-2)_\mu$ and the theoretical prediction in the Standard Model. Such a heavy $Z^\prime$ boson also implies that the minimal value for a new Higgs mass is of the order of 400 GeV., Comment: 20 pages, 9 figures; discussion extended, an extra figure and references added, conclusions unchanged; final version

Multi-peaked spectra of the primordial gravitational waves are considered as a phenomenologically relevant source of information about the dynamics of sequential phase transitions in the early Universe. In particular, such signatures trace back to specific patterns of the first-order electroweak phase transition in the early Universe occurring in multiple steps. Such phenomena appear to be rather generic in multi-scalar extensions of the Standard Model. In a particularly simple extension of the Higgs sector, we have identified and studied the emergence of sequential long- and short-lasting transitions as well as their fundamental role in generation of multi-peaked structures in the primordial gravitational-wave spectrum. We discuss the potential detectability of these signatures by the proposed gravitational-wave interferometers., Comment: 33 pages, 7 figures; references added; discussion of the results updated; published version

We investigate the production of primordial Gravitational Waves (GWs) arising from First Order Phase Transitions (FOPTs) associated to neutrino mass generation in the context of type-I and inverse seesaw schemes. We examine both "high-scale" as well as "low-scale" variants, with either explicit or spontaneously broken lepton number symmetry $U(1)_L$ in the neutrino sector. In the latter case, a pseudo-Goldstone majoron-like boson may provide a candidate for cosmological dark matter. We find that schemes with softly-broken $U(1)_L$ and with single Higgs-doublet scalar sector lead to either no FOPTs or too weak FOPTs, precluding the detectability of GWs in present or near future measurements. Nevertheless, we found that, in the majoron-like seesaw scheme with spontaneously broken $U(1)_L$ at finite temperatures, one can have strong FOPTs and non-trivial primordial GW spectra which can fall well within the frequency and amplitude sensitivity of upcoming experiments, including LISA, BBO and u-DECIGO. However, GWs observability clashes with invisible Higgs decay constraints from the LHC. A simple and consistent fix is to assume the majoron-like mass to lie above the Higgs-decay kinematical threshold. We also found that the majoron-like variant of the low-scale seesaw mechanism implies a different GW spectrum than the one expected in the high-scale seesaw. This feature will be testable in future experiments. Our analysis shows that GWs can provide a new and complementary portal to test the neutrino mass generation mechanism., Comment: 11 pages, 5 figures, 4 tables; invisible Higgs decay constraint incorporated; discussion extended; references added

The first-order electroweak phase transition in the early universe could occur in multiple steps leading to specific multi-peaked signatures in the primordial gravitational wave (GW) spectrum. We argue that these signatures are generic phenomena in multi-scalar extensions of the Standard Model. In a simple example of such an extension, we have studied the emergence of reoccurring and nested vacuum bubble configurations and their role in the formation of multiple peaks in the GW spectrum. The conditions for potential detectability of these features by the forthcoming generation of interferometers have been studied., Comment: 7 pages, 3 captioned figures, 1 table; numerical analysis extended, conclusions unchanged; contributed talk by R. Pasechnik at the EPS-HEP2019, 10-17 July, 2019, Ghent, Belgium

The rich vacuum structure of multi-Higgs extensions of the Standard Model (SM) may have interesting cosmological implications for the electroweak phase transition (EWPT). As an important example of such class of models, we consider a particularly simple low-energy SM-like limit of a recently proposed Grand-Unified Trinification model with the scalar sector composed of two Higgs doublets and a complex singlet and with a global $\mathrm{U}(1)$ family symmetry. The fermion sector of this model is extended with a family of vector-like quarks which enhances CP violation. With the current study, we aim at exploring the generic vacuum structure and uncovering the features of the EWPT in this model relevant for cosmology. We show the existence of different phase transition patterns providing strong departure from thermal equilibrium. Most of these observations are not specific to the considered model and may generically be expected in other multi-Higgs extensions of the SM., Comment: 48 pages, 13 figures

A unification of left-right $\rm{SU}(3)_\rm{L}\times \rm{SU}(3)_\rm{R}$, colour $\rm{SU}(3)_\rm{C}$ and family $\rm{SU}(3)_\rm{F}$ symmetries in a maximal rank-8 subgroup of ${\rm{E}}_8$ is proposed as a landmark for future explorations beyond the Standard Model (SM). We discuss the implications of this scheme in a supersymmetric (SUSY) model based on the trinification gauge $\left[\rm{SU}(3)\right]^3$ and global $\rm{SU}(3)_\rm{F}$ family symmetries. Among the key properties of this model are the unification of SM Higgs and lepton sectors, a common Yukawa coupling for chiral fermions, the absence of the $\mu$-problem, gauge couplings unification and proton stability to all orders in perturbation theory. The minimal field content consistent with a SM-like effective theory at low energies is composed of one $\mathrm{E}_6$ $27$-plet per generation as well as three gauge and one family $\rm{SU}(3)$ octets inspired by the fundamental sector of ${\rm{E}}_8$. The details of the corresponding (SUSY and gauge) symmetry breaking scheme, multi-scale gauge couplings' evolution, and resulting effective low-energy scenarios are discussed., Comment: 31 pages, 3 figures; discussion of particle mass hierarchies at low energies expanded; the version accepted to Phys. Rev. D

We present a supersymmetric (SUSY) model based on trinification $[\mathrm{SU}(3)]^3$ and family $\mathrm{SU}(3)_\mathrm{F}$ symmetries embedded into a maximal subgroup of $\mathrm{E}_8$, where the sectors of light Higgs bosons and leptons are unified into a single chiral supermultiplet. The common origin of gauge trinification and of the family symmetry from $\mathrm{E}_8$ separates the model from other trinification-based GUTs, as it protects, in particular, the Standard Model fermions from gaining mass until the electroweak symmetry is broken. Furthermore, it allows us to break the trinification symmetry via vacuum expectation values in $\mathrm{SU}(3)$-adjoint scalars down to a left-right symmetric theory. Simultaneously, it ensures the unification of the gauge and Yukawa couplings as well as proton stability. Although the low-energy regime (e.g. mass hierarchies in the scalar sector determined by a soft SUSY-breaking mechanism) is yet to be established, these features are one key to revive the once very popular trinification-based GUTs., Comment: 6 pages; published version

Using the one-loop Coleman-Weinberg effective potential, we derive a general analytic expression for all the derivatives of the effective potential with respect to any number of classical scalar fields. The result is valid for a renormalisable theory in four dimensions with any number of scalars, fermions or gauge bosons. This result corresponds to the zero-external momentum contribution to a general one-loop diagram with N scalar external legs. We illustrate the use of the general result in two simple scalar singlet extensions of the Standard Model, to obtain the dominant contributions to the triple couplings of light scalar particles under the zero external momentum approximation, Comment: 26 pages, 2 figures. Minor text improvements and new references added. To appear in JHEP

In this work, we present a trinification-based grand unified theory incorporating a global $\mathrm{SU}(3)$ family symmetry that after a spontaneous breaking leads to a left-right symmetric model. Already at the classical level, this model can accommodate the matter content and the quark Cabbibo mixing in the Standard Model (SM) with only one Yukawa coupling at the unification scale. Considering the minimal low-energy scenario with the least amount of light states, we show that the resulting effective theory enables dynamical breaking of its gauge group down to that of the SM by means of radiative corrections accounted for by the renormalisation group evolution at one loop. This result paves the way for a consistent explanation of the SM breaking scale and fermion mass hierarchies., Comment: 39 pages, 6 figures. Added a discussion (Sect. 7.2) on 1-loop contributions to the masses of light scalars. Published version

We analyse the low energy predictions of the minimal supersymmetric standard model (MSSM) arising from a GUT scale Pati-Salam gauge group further constrained by an $A_4 \times Z_5$ family symmetry, resulting in four soft scalar masses at the GUT scale: one left-handed soft mass $m_0$ and three right-handed soft masses $m_1,m_2,m_3$, one for each generation. We demonstrate that this model, which was initially developed to describe the neutrino sector, can explain collider and non-collider measurements such as the dark matter relic density, the Higgs boson mass and, in particular, the anomalous magnetic moment of the muon $(g-2)_\mu$. Since about two decades, $(g-2)_\mu$ suffers a puzzling about 3$\,\sigma$ excess of the experimentally measured value over the theoretical prediction, which our model is able to fully resolve. As the consequence of this resolution, our model predicts specific regions of the parameter space with the specific properties including light smuons and neutralinos, which could also potentially explain di-lepton excesses observed by CMS and ATLAS., Comment: 29 pages, 14 figures; [v2] added references, corrected minor typos

We present a study of the high energy stability of a minimal complex singlet extension of the Standard Model with or without dark matter (CxSM). We start by obtaining the beta functions of the couplings of the theory from the effective potential and then perform the RGE evolution for the allowed parameter space of the model at the electroweak scale. We obtain the scale up to which the model survives and combine this information with all the LHC measurements as well as bounds from dark matter detection experiments as well as the relic density best measurement from Planck. We conclude that scenarios which solve both the dark matter and stability problems must contain a dark particle heavier than 50 GeV and a new visible state (mixing with the SM-like Higgs) heavier than 170 GeV., Comment: Proceeding of the 2nd Toyama Workshop "Higgs as a Probe of New Physics 2015", 11-15 February 2015. 5 pages, 2 figures

Motivated by the dark matter and the baryon asymmetry problems, we analyse a complex singlet extension of the Standard Model (SM) with a Z2 symmetry (which provides a dark matter candidate). After a detailed two-loop calculation of the renormalization group equations for the new scalar sector, we study the radiative stability of the model up to a high energy scale (with the constraint that the 126 GeV Higgs boson found at the LHC is in the spectrum) and find it requires the existence of a new scalar state mixing with the Higgs with a mass larger than 140 GeV. This bound is not very sensitive to the cut-off scale as long as the latter is larger than 10^10 GeV. We then include all experimental and observational constraints/measurements from collider data, dark matter direct detection experiments and from the Planck satellite and in addition force stability at least up to the GUT scale, to find that the lower bound is raised to about 170 GeV, while the dark matter particle must be heavier than about 50 GeV., Comment: Added paragraphs in sect. 4.1 and new appendix C. 44 pages, 11 figures