Search

The Fermi National Accelerator Laboratory (FNAL) recently announced confirmation of the Brookhaven National Lab (BNL) measurements of the $g-2$ of the muon that uncovered a discrepancy with the theoretically calculated Standard Model value. We suggest an explanation for the combined BNL+FNAL 4.2$\sigma$ deviation within the supersymmetric grand unification theory (GUT) model No-Scale $\cal{F}$-$SU(5)$ supplemented with a string derived TeV-scale extra $10+\overline{10}$ vector-like multiplet and charged vector-like singlet $(XE,XE^c)$, dubbed flippons. We introduced these vector-like particles into No-Scale Flipped $SU(5)$ many years ago, and as a result, the renormalization group equation (RGE) running was immediately shaped to produce a distinctive and rather beneficial two-stage gauge coupling unification process to avoid the Landau pole and lift unification to the string scale, in addition to contributing through 1-loop to the light Higgs boson mass. The flippons have long stood ready to tackle another challenge, and now do so yet again, where the charged vector-like "lepton"/singlet couples with the muon, the supersymmetric down-type Higgs $H_d$, and a singlet $S$, using a chirality flip to easily accommodate the muonic $g-2$ discrepancy in No-Scale $\cal{F}$-$SU(5)$. Considering the phenomenological success of this string derived model over the prior 11 years that remains accommodative of all presently available LHC limits plus all other experimental constraints, including no fine-tuning, and the fact that for the first time a Starobinsky-like inflationary model consistent with all cosmological data was derived from superstring theory in No-Scale Flipped $SU(5)$, we believe it is imperative to reconcile the BNL+FNAL developments within the model space., Comment: 12 Pages, 3 Figures; EPJC Version

We consider a class of $\text{SO}(10)$ models with flavor symmetries in the Yukawa sector and investigate their viability by performing numerical fits to the fermion masses and mixing parameters. The fitting procedure involves a top-down approach in which we solve the renormalization group equations from the scale of grand unification down to the electroweak scale. This allows the intermediate scale right-handed neutrinos and scalar triplet, involved in the type I and II seesaw mechanisms, to be integrated out at their corresponding mass scales, leading to a correct renormalization group running. The result is that, of the 14 models considered, only two are able to fit the known data well. Both these two models correspond to $\mathbb{Z}_2$ symmetries. In addition to being able to fit the fermion masses and mixing parameters, they provide predictions for the sum of light neutrino masses and the effective neutrinoless double beta decay mass parameter, which are both within current observational bounds., Comment: 19 pages, 4 tables. Final version published in JHEP

We discuss gauge mediated supersymmetry breaking models which explain the observed muon anomalous magnetic moment and the Higgs boson mass simultaneously. The successful explanation requires the messenger sector which violates the relation motivated by the grand unification theory (GUT). The naive violation of the GUT relation, however, ends up with the CP problem. We propose a model in which the phases of the gaugino masses are aligned despite the violation of the GUT relation. We also consider a model which generates the $\mu$-term and the additional Higgs soft masses squared without causing CP violation. As a result, we find a successful model which explains the muon anomalous magnetic moment and the Higgs boson mass. The model is also free from the CP, flavor-changing neutral current and the lepton flavor violation problems caused by the subdominant gravity mediation effects., Comment: 33 pages, 7 figures, Mass spectrum calculator: https://member.ipmu.jp/satoshi.shirai/sweetspot/sweetspotSUSY.php

We explicitly test the asymptotic grand unification of a minimal 5-dimensional model with SO(10) gauge theory compactified on an $S^{1}/Z_{2}\times Z^{\prime}_{2}$ orbifold. We consider all matter fields as propagating in the bulk and show that the gauge couplings asymptotically run to a fixed point in the UV. However, the Yukawa couplings will typically hit a Landau pole right above the compactification scale in this class of SO(10) models., 6 pages, 1 figure, submitted to the PACP2022 conference proceedings

We propose a model of fermion masses and mixings based on $SU(5)$ grand unified theory (GUT) and a $D_{4}$ flavor symmetry. This is a highly predictive 4D $SU(5)$ GUT with a flavor symmetry that does not contain a triplet irreducible representation. The Yukawa matrices of quarks and charged leptons are obtained after integrating out heavy messenger fields from renormalizable superpotentials while neutrino masses originate from the type I seesaw mechanism. The group theoretical factors from 24- and 45-dimensional Higgs fields lead to ratios between the Yukawa couplings in agreement with data, while the dangerous proton decay operators are highly suppressed. By performing a numerical fit, we find that the model captures accurately the mixing angles, the Yukawa couplings and the $CP$ phase of the quark sector at the GUT scale. The neutrino masses are generated at the renormalizable level with the prediction of trimaximal mixing while an additional effective operator is required to account for the baryon asymmetry of the universe (BAU). The model is remarkably predictive because only the normal neutrino mass ordering and the lower octant of the atmospheric angle are allowed while the $CP$ conserving values of the Dirac neutrino phase $\delta_{CP}$ are excluded. Moreover, the predicted values of the effective Majorana mass $m_{\beta \beta}$ can be tested at future neutrinoless double beta decay experiments. An analytical and a numerical study of the BAU via the leptogenesis mechanism is performed. We focused on the regions of parameter space where leptogenesis from the lightest right-handed neutrino is successfully realized. Strong correlations between the parameters of the neutrino sector and the observed BAU are obtained., Comment: 39 pages, 28 figures, matches published version

We study leptonic CP and flavor violations in supersymmetric (SUSY) grand unified theory (GUT) with right handed neutrinos, paying attention to the renormalization group effects on the slepton mass matrices due to the neutrino and GUT Yukawa interactions. In particular, we study in detail the impacts of the so-called Casas- Ibarra parameters on CP and flavor violating observables. The renormalization group effects induce CP and flavor violating elements of the SUSY breaking scalar mass squared matrices, which may result in sizable leptonic CP and flavor violating signals. Assuming seesaw formula for the active neutrino masses, the renormalization group effects have been often thought to be negligible as the right-handed neutrino masses become small. With the most general form of the neutrino Yukawa matrix, i.e., taking into account the Casas-Ibarra parameters, however, this is not the case. We found that the maximal possible sizes of signals of leptonic CP and flavor violating processes are found to be insensitive to the mass scale of the right-handed neutrinos and that they are as large as (or larger than) the present experimental bounds irrespective of the right-handed neutrino masses., Comment: 23 pages, 8 figures

We extend the classification of fermionic $\mathbb{Z}_2\times\mathbb{Z}_2$ heterotic string orbifolds to non--supersymmetric Pati--Salam (PS) models in two classes of vacua, that we dub $\tilde S$--models and $S$--models. The first correspond to compactifications of a tachyonic ten--dimensional vacuum, whereas the second correspond to compactifications of the ten--dimensional tachyon--free $SO(16)\times SO(16)$ heterotic string. In both cases we develop a systematic method to extract tachyon--free four--dimensional models. We show that tachyon--free configurations arise with probability $\sim0.002$ and $\sim0.01$ in the first and second case, respectively. We adapt the `fertility methodology' that facilitates the extraction of phenomenological models. We show that Pati--Salam $\tilde S$--models do not contain heavy Higgs scalar representations that are required to break the PS symmetry to the Standard Model and are therefore not phenomenologically viable. Hence, we argue that in $\tilde S$--models the $SO(10)$ GUT symmetry must be broken at the string scale to the Standard--like Model subgroup. We extract tachyon--free three generation models in both cases that contain an equal number of massless bosonic and fermionic degrees of freedom, ${\it i.e.}$ with $a_{00}=N_b^0-N_f^0=0$, and analyse their one--loop partition function., 37 pages. 5 figures. Standard LaTex. Added Comments

We study the phenomenology of the two Higgs doublet model with a real singlet scalar $S$ (2HDMS). The model predicts three CP-even Higgses $h_{1,2,3}$, one CP-odd $A^0$ and a pair of charged Higgs. We discuss the consistency of the 2HDMS with theoretical as well as with all available experimental data. In contrast with previous studies, we focus on the scenario where $h_2$ is the Standard Model (SM) 125 GeV Higgs, while $h_1$ is lighter than $h_2$ which may open a window for Higgs to Higgs decays. We perform an extensive scan into the parameter space of 2HDMS of type I and explore the effect of the singlet-doublet admixture. We found that a large singlet-doublet admixture is still compatible with the recent Higgs data from LHC. Moreover, we show that $h_1$ could be quasi-fermiophobic and would decay dominantly into two photons. We also study in details the consistency of the non-detected decay of $h_2\to h_1 h_1$ with LHC data followed by $h_1\to \gamma \gamma$ which leads to four photons final state at LHC: $pp\to h_2\to h_1 h_1\to 4\gamma$. Using the results of null searches of multi-photons carried by the ATLAS collaboration, we have found that a large area of the parameter space is still allowed. We also demonstrate that various neutral Higgs of the 2HDMS could have several exotic decays., Comment: 21 pages, EPJC style, 13Figures

The vanishing of the Higgs quartic coupling of the Standard Model at high energies may be explained by spontaneous breaking of Higgs Parity. Taking Higgs Parity to originate from the Left-Right symmetry of the $SO(10)$ gauge group, leads to a new scheme for precision gauge coupling unification that is consistent with proton decay. We compute the relevant running of couplings and threshold corrections to allow a precise correlation among Standard Model parameters. The scheme has a built-in solution for obtaining a realistic value for $m_b/m_\tau$, which further improves the precision from gauge coupling unification, allowing the QCD coupling constant to be predicted to the level of 1 % or, alternatively, the top quark mass to 0.2 %. Future measurements of these parameters may significantly constrain the detailed structure of the theory. We also study an $SO(10)$ embedding of quark and lepton masses, showing how large neutrino mixing is compatible with small quark mixing, and predict a normal neutrino mass hierarchy. The strong CP problem may be explained by combining Higgs Parity with space-time parity., Comment: 39 pages, 9 figures

We employ a variety of symmetry breaking patterns in $SO(10)$ and $E_6$ Grand Unified Theories to demonstrate the appearance of topological defects including magnetic monopoles, strings, and necklaces. We show that independent of the symmetry breaking pattern, a topologically stable superheavy monopole carrying a single unit of Dirac charge as well as color magnetic charge is always present. Lighter intermediate mass topologically stable monopoles carrying two or three quanta of Dirac charge can appear in $SO(10)$ and $E_6$ models respectively. These lighter monopoles as well as topologically stable intermediate scale strings can survive an inflationary epoch. We also show the appearance of a novel necklace configuration in $SO(10)$ broken to the Standard Model via $SU(4)_c\times SU(2)_L\times SU(2)_R$. It consists of $SU(4)_c$ and $SU(2)_R$ monopoles connected by flux tubes. Necklaces consisting of monopoles and antimonopoles joined together by flux tubes are also identified. Even in the absence of topologically stable strings, a monopole-string system can temporarily appear. This system decays by emitting gravity waves and we provide an example in which the spectrum of these waves is strongly peaked around $10^{-4}~{\rm Hz}$ with $\Omega_{\rm gw}h^2\simeq 10^{-12}$. This spectrum should be within the detection capability of LISA., Comment: 21 pages including 3 figures, major revision, version to be published in JHEP

We introduce a class of non-supersymmetric models explaining baryogenesis a la Affleck-Dine, which use a decay of two superheavy scalar fields with close masses. These scalars acquire non-zero expectation values during inflation through linear couplings to a function of an inflaton. After the inflaton decay, the model possesses approximate U(1)-invariance, explicitly broken by a small mass splitting. This splitting leads to the baryogenesis in the early Universe. Resulting baryon asymmetry is automatically small for the scalars with the masses about the Grand Unification scale and larger. It is fully determined by the inflaton dynamics and the Lagrangian parameters, i.e., is independent of initial pre-inflationary conditions for the scalars. As a consequence, baryon perturbations are purely adiabatic. We point out a possible origin of the mass splitting: masses of scalars degenerate at some large energy scale may acquire different loop corrections due to the interaction with the inflaton. Compared to electroweak baryogenesis and conventional Affleck-Dine scenarios, our mechanism generically leads to the proton decay suppressed by the powers of the superheavy scalar masses, which makes this scenario potentially testable., Comment: 6 pages; matches published version

We discuss the Yukawa coupling unification, a very interesting prediction of the grand unified theory, in the context of scenarios with more than one pair of Higgs doublet since the current LHC constraint has become a problem for the Yukawa unification scenarios with just one pair of Higgs doublet. More than one pair of Higgs doublets can easily arise in missing partner mechanism which solves the doublet-triplet splitting problem. In such a scenario, the Yukawa unification occurs at a medium $\tan\beta$ value, e.g., $\sim$ 30, which corresponds to much smaller threshold corrections compared to usual large $\tan\beta$ scenario for $t-b-\tau$ unification in the context of SO(10) and $b-\tau$ unification in the context of SU(5) models. Further, we show that an additional Higgs doublet pair lowers the sensitivity of the radiative symmetry breaking of the electroweak vacuum., Comment: 12 pages, 3 figures

A simple Standard Model Extension based on $T_7$ flavor symmetry which accommodates lepton mass and mixing with non-zero $\theta_{13}$ and CP violation phase is proposed. At the tree- level, the realistic lepton mass and mixing pattern is derived through the spontaneous symmetry breaking by just one vacuum expectation value ($v$) which is the same as in the Standard Model. Neutrinos get small masses from one $SU(2)_L$ doublet and two $SU(2)_L$ singlets in which one being in $\underline{1}$ and the two others in $\underline{3}$ and $\underline{3}^*$ under $T_7$ , respectively. The model also gives a remarkable prediction of Dirac CP violation $\delta_{CP}=172.598^\circ$ in both normal and inverted hierarchies which is still missing in the neutrino mixing matrix., Comment: 23 pages, 6 figures

We consider a $SU(3)_c \times SU(3)_L \times U(1)_X$ model from a $SU(6)$ Grand Unified Theory (GUT). In order to explain the anomalous magnetic moments of muon and electron, we introduce two new scalar triplets without vacuum expectation values (VEVs) so that the leading contributions to $\Delta a_{\mu}$ and $\Delta a_{e}$ can avoid the suppression from small muon mass. In addition, the Higgs potential stability of this 331 model is studied by giving a set of sufficient conditions to ensure the boundedness from below of the potential., Comment: 15 pages

We consider thermal, trapped and chromo-natural inflation in light of the swampland criteria and the Trans-Planckian Censorship Conjecture (TCC). Since thermal inflation occurs at energies low compared to those of Grand Unification, it is consistent with the TCC, and it is also consistent with the refined swampland conditions. Trapped and chromo-natural inflation are candidates for primordial (high energy scale) inflation. Since in both of these scenarios there are effective damping terms in the scalar field equation of motion, the models can easily be consistent with the swampland criteria. The TCC, on the other hand, constrains these scenarios to only take place at low energies., 8 pages

A pseudo-Nambu-Goldstone boson (pNGB) is an attractive candidate for dark matter (DM) due to the simple evasion of the current severe limits of DM direct detection experiments. One of the pNGB DM models has been proposed based on a {\it gauged} $U(1)_{B-L}$ symmetry. The pNGB has long enough lifetime to be a DM and thermal relic abundance of pNGB DM can be fit with the observed value against the constraints on the DM decays from the cosmic-ray observations. The pNGB DM model can be embedded into an $SO(10)$ pNGB DM model in the framework of an $SO(10)$ grand unified theory, whose $SO(10)$ is broken to the Pati-Salam gauge group at the unified scale, and further to the Standard Model gauge group at the intermediate scale. Unlike the previous pNGB DM model, the parameters such as the gauge coupling constants of $U(1)_{B-L}$, the kinetic mixing parameter of between $U(1)_Y$ and $U(1)_{B-L}$ are determined by solving the renormalization group equations for gauge coupling constants with appropriate matching conditions. From the constraints of the DM lifetime and gamma-ray observations, the pNGB DM mass must be less than $\mathcal{O}(100)$$\,$GeV. We find that the thermal relic abundance can be consistent with all the constraints when the DM mass is close to half of the CP even Higg masses., 26 pages, 6 tables, 5 figures; typos corrected; some figures replaced; some references and paragraphs added; accepted for publication in Physical Review D

We study the textures of SM fermion mass matrices and their mixings in a supersymmetric adjoint SU(5) Grand Unified Theory with modular $S_4$ being the horizontal symmetry. The Yukawa entries of both quarks and leptons are expressed by modular forms with lower weights. Neutrino sector has an adjoint SU(5) representation 24 as matter superfield, which is a triplet of $S_4$. The effective light neutrino masses is generated through Type-III and Type-I seesaw mechanism. The only common complex parameter in both charged fermion and neutrino sectors is modulus $\tau$. Down-type quarks and charged leptons have the same joint effective operators with adjoint scalar in them, and their mass discrepancy in the same generation depends on Clebsch-Gordan factor. Especially for the first two generations the respective Clebsch-Gordan factors made the double Yukawa ratio $y_dy_{\mu}/y_ey_s=12$, in excellent agreement with the experimental result. We reproduce proper CKM mixing parameters and all nine Yukawa eigenvalues of quarks and charged leptons. Neutrino masses and MNS parameters are also produced properly with normal ordering is preferred., Comment: 24 pages,3 figures,Matches JHEP version

Product group unification is an attractive alternative to simple grand unification. It solves the infamous doublet-triplet splitting problem and the dimension-5 proton decay problems without introducing any fine-tuning. Furthermore, the matter multiplets are still embedded into unified SU(5) representations. In this paper, we discuss proton decay of the simplest product group unification model based on SU(5)XU(2)_H . We find that the minimal setup of the model has already been excluded by dimension-6 proton decay. We also show that a simple extension of the model, with naturally generated SU(5) incomplete multiplets, can rectify this problem. We find that the proton lifetime will be in reach of coming experiments like DUNE and Hyper-K, when the mass of the incomplete multiplet is associated with the Peccei-Quinn symmetry breaking. In this case, the dark matter may be an admixture of the Wino LSP and the axion., Comment: 23 pages, 15 figures

In a class of gauged $U(1)$ extended Standard Models (SMs), the breaking of the $U(1)$ symmetry is not only a source for Majorana masses of right-handed (RH) neutrinos crucial for the seesaw mechanism, but also a source of stochastic gravitational wave (GW) background. Such $U(1)$ extended models are well-motivated from the viewpoint of grand unification. In this paper, we discuss a successful ultraviolet completion of a $U(1)$ extended SM by an $SO(10)$ grand unified model through an intermediate step of $SU(5) \times U(1)$ unification. With a parameter set that is compatible with the $SO(10)$ grand unification, we find that a first-order phase transition associated with the $U(1)$ symmetry breaking can be strong enough to generate GWs with a detectable size of amplitude. We also find that the resultant GW amplitude reduces and its peak frequency becomes higher as the RH neutrino masses increase., Comment: 24 pages, 3 figures, discussion and references added, the final journal published version

Cosmic birefringence is predicted if an axion-like particle (ALP) moves after the recombination. We show that this naturally happens if the ALP is coupled to the dark matter density because it then acquires a large effective mass after the matter-radiation equality. Our scenario applies to a broad range of the ALP mass $m_\phi \lesssim 10^{-28}$ eV, even smaller than the present Hubble constant. We give a simple model to realize this scenario, where dark matter is made of hidden monopoles, which give the ALP such a large effective mass through the Witten effect. The mechanism works if the ALP decay constant is of order the GUT scale without a fine-tuning of the initial misalignment angle. For smaller decay constant, the hidden monopole can be a fraction of dark matter. We also study the implications for the QCD axion, and show that the domain wall problem can be solved by the effective mass., Comment: 6 pages, 2 figures

Journal of cosmology and astroparticle physics 12(12), 006 (1-28) (2021). doi:10.1088/1475-7516/2021/12/006, A metastable cosmic-string network is a generic consequence of many grand unified theories (GUTs) when combined with cosmic inflation. Metastable cosmic strings are not topologically stable, but decay on cosmic time scales due to pair production of GUT monopoles. This leads to a network consisting of metastable long strings on superhorizon scales as well as of string loops and segments on subhorizon scales. We compute for the first time the complete stochastic gravitational-wave background (SGWB) arising from all these network constituents, including several technical improvements to both the derivation of the loop and segment contributions. We find that the gravitational waves emitted by string loops provide the main contribution to the gravitational-wave spectrum in the relevant parameter space. The resulting spectrum is consistent with the tentative signal observed by the NANOGrav and Parkes pulsar timing collaborations for a string tension of G $_{��}$ ��� 10$^{-11���-7}$ and has ample discovery space for ground- and space-based detectors. For GUT-scale string tensions, G $_{��}$ ��� 10$^{-8���-7}$, metastable strings predict a SGWB in the LIGO-Virgo-KAGRA band that could be discovered in the near future., Published by IOP, London

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., 11 pages, 2 tables, 1 figure; discussion somewhat extended; published version

We propose a pseudo-Goldstone boson dark matter (pGDM) particle in $SO(10)$ grand unified theory (GUT). Due to its Goldstone nature, this pGDM evades the direct DM detection experiments which, otherwise, severely constrain the parameter space of DM models. In $SO(10)$, the pGDM is embedded as a linear combination of the Standard Model (SM) singlet scalars in ${\bf 16_H}$ and ${\bf 126_H}$ representations. We consider two scenarios for the intermediate route of $SO(10)$ symmetry breaking (SB) to the SM: $SU(5) \times U(1)_X$ and Pati-Salam the $SU(4)_c \times SU(2)_L \times SU(2)_R$ (4-2-2) gauge groups. The vacuum expectation value of ${\bf 126_H}$, which triggers the breaking of $U(1)_X$ and 4-2-2 symmetry in the two scenarios, respectively, determines the pGDM lifetime whose astrophysical lower bound provides one of the most stringent constraints. For the 4-2-2 route to $SO(10)$, the successful SM gauge coupling unification requires the 4-2-2 breaking scale to be ${\cal O} (10^{11})$ GeV, and most of the parameter space is excluded. For the $SU(5) \times U(1)_X$ route, on the other hand, the $U(1)_X$ breaking scale can be significantly higher, and a wide range of the parameter space is allowed. Furthermore, the proton lifetime in the $SU(5)$ case is predicted to be $4.53 \times 10^{34}$ years, which lies well within the sensitivity reach of the Hyper-Kamiokande experiment. We also examine the constraints on the model parameter space from the Large Hadron Collider and the indirect DM search by Fermi-LAT and MAGIC experiments., Comment: 25 pages, 5 figures, Figures 3 revised, updated version accepted for publication in PRD

Physical review letters 126(20), 201802 (2021). doi:10.1103/PhysRevLett.126.201802, We present a leptogenesis mechanism based on the standard type-I seesaw model that successfully operates at right-handed-neutrino masses as low as a few 100 TeV. This mechanism, which we dub 'wash-in leptogenesis', does not require any CP violation in the neutrino sector and can be implemented even in the regime of strong wash-out. The key idea behind wash-in leptogenesis is to generalize standard freeze-out leptogenesis to a nonminimal cosmological background in which the chemical potentials of all particles not in chemical equilibrium at the temperature of leptogenesis are allowed to take arbitrary values. This sets the stage for building a plethora of new baryogenesis models where chemical potentials generated at high temperatures are reprocessed to generate a nonvanishing B-L asymmetry at low temperatures. As concrete examples, we discuss wash-in leptogenesis after axion inflation and in the context of grand unification., Published by APS, College Park, Md.

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

Upon embedding the axion-inflation in the minimal left-right symmetric gauge extension of the SM with gauge group $SU(2)_L\times SU(2)_R \times U(1)_{B-L}$, [arXiv:2012.11516] proposed a new particle physics model for inflation. In this work, we present a more detailed analysis. As a compelling consequence, this setup provides a new mechanism for simultaneous baryogenesis and right-handed neutrino creation by the chiral anomaly of $W_R$ in inflation. The lightest right-handed neutrino is the dark matter candidate. This setup has two unknown fundamental scales, i.e., the scale of inflation and left-right symmetry breaking $SU(2)_R\times U(1)_{B-L}\rightarrow U(1)_{Y}$. Sufficient matter creation demands the left-right symmetry breaking scale happens shortly after the end of inflation. Interestingly, it prefers left-right symmetry breaking scales above $10^{10}~GeV$, which is in the range suggested by the non-supersymmetric SO(10) Grand Unified Theory with an intermediate left-right symmetry scale. Although $W_R$ gauge field generates equal amounts of right-handed baryons and leptons in inflation, i.e. $B-L=0$, in the Standard Model sub-sector $B-L_{SM}\neq 0$. A key aspect of this setup is that $SU(2)_R$ sphalerons are never in equilibrium, and the primordial $B-L_{SM}$ is conserved by the Standard Model interactions. This setup yields a deep connection between CP violation in physics of inflation and matter creation (visible and dark); hence it can naturally explain the observed coincidences among cosmological parameters, i.e., $\eta_{B}\simeq 0.3 P_{\zeta}$ and $\Omega_{DM}\simeq 5\Omega_{B}$. The $SU(2)_R$-axion inflation comes with a cosmological smoking gun; chiral, non-Gaussian, and blue-tilted gravitational wave background, which can be probed by future CMB missions and laser interferometer detectors., Comment: 28+20 Pages, 15 Figs

The success of primordial nucleosynthesis as a cornerstone of the hot Big Bang model has been limited by the long-standing lithium problem. Recent work presented a self-consistent perturbative analysis of the effects of variations in nature's fundamental constants on primordial nucleosynthesis for a broad class of grand unified theory models, showing that such models provide a possible solution to the lithium problem, provided the value of the fine-structure constant $\alpha$ at the nucleosynthesis epoch is larger than the current laboratory one by a few parts per million of relative variation. Here we extend the earlier analysis, focusing on how this preferred value of $\alpha$ is affected if relevant cosmological parameters are also allowed to vary--specifically focusing on the baryon-to-photon ratio, the number of neutrinos, and the neutron lifetime. We rephrase the lithium problem in terms of the values of these parameters that would be needed to solve it within this class of grand unified theories, thus obtaining values that would disagree with the results of other experiments by several standard deviations. Using these experimental results as priors in the analysis, we find that a larger value of $\alpha$ is still preferred, confirming our previous results. By excluding lithium from the analysis, we also obtain upper limits on possible variations of $\alpha$ at the primordial nucleosynthesis epoch. At the two-sigma level, these are $|\Delta\alpha/\alpha, Comment: 11 pages, 5 figures, Astronomy & Astrophysics (in press)

We show that in nonlocal generalization of standard nonsupersymmetric SU(5) GUT it is possible to solve the problems with the proton lifetime and the Weinberg angle without introduction of additional particles in the spectrum of the theory. Non-local scale responsible for ultraviolet cutoff coincides (up to some factor) with GUT scale. We find that in the simplest nonlocal modification of the SU(5) model $M_{\rm GUT} = 3 * 10^{16}$ GeV . In general case the value of M_GUT is an arbitrary and the most interesting option $M_{\rm GUT} = O(M_{\rm PL})$ could be realized., Comment: 7 pages

We minimally extend the Standard Model field content by adding new vector-like fermions at the TeV scale to allow gauge coupling unification at a realistic scale. We embed the model into a $SU(5)$ grand unified theory that is asymptotically safe and features an interacting fixed point for the gauge coupling. There are no Landau poles of the $U(1)$ gauge and Higgs couplings. Gauge, Yukawa and Higgs couplings are retraced from the fixed point and matched at the grand unification scale to those of the Standard Model rescaled up to the same energy. All couplings, their fixed point values and critical exponents always remain in the perturbative regime., 25 pages, 3 figures, 6 tables

Color-octet scalars arise in various Grand Unification scenarios and also in other models of new physics. They are also postulated for minimal flavour violation. Purely phenomenological imprints of such scalars are therefore worth looking at. Motivated by this, we perform a complete one-loop calculation of the $H^+ \to W^+ Z (\g)$ decay in a two Higgs doublet model augmented by a color-octet $SU(2)_L$ scalar doublet. The computation is conveniently segregated into colorless and colored components. The color-octet part of the amplitude, being scaled by the color-factor, provides an overall enhancement to the form factors. Crucial constraints from perturbative unitarity, positivity of the scalar potential, oblique parameters, Higgs signal strengths and direct search of a charged Higgs and color-octet scalars are folded-in into the analysis. Sensitivity of the loop-induced $H^+ \to W^+ Z (\g)$ vertex to other model parameters is elucidated. Finally, the prospect of observing a loop-induced $H^+ \to W^+ Z (\g)$ interaction at the future hadronic collisions is also discussed., Comment: 27 pages (in 2 column format), 4 tables, 15 captioned figures. Version published in EPJC

We present a model for third-family quark-lepton unification at the TeV scale featuring a composite Higgs sector. The model is based on a variant of the Pati-Salam model, the so-called 4321 model, consisting of the gauge group $SU(4)\times SU(3)^\prime\times SU(2)_L\times U(1)_X$. The spontaneous symmetry breaking to the SM gauge group is triggered dynamically by a QCD-like confining sector. The same strong dynamics also produces the Higgs as a pseudo Nambu-Goldstone boson, connecting the energy scales of both sectors. The model predicts a massive $U_1$ vector leptoquark coupled dominantly to the third generation, recently put forward as a possible solution to the $B$-meson anomalies., Comment: 14 pages, 2 figures. v2: matching the journal version

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

To address five fundamental shortcomings of the Standard Model (SM) of particle physics and cosmology, we propose a SMART U(1)$_X$ model which is a $U(1)_X \times U(1)_{PQ}$ extension of the SM. The $U(1)_X$ gauge symmetry is a generalization of the well-known $U(1)_{B-L}$ symmetry and $U(1)_{PQ}$ is the global Peccie-Quinn (PQ) symmetry. Three right handed neutrinos are added to cancel $U(1)_X$ related anomalies, and they play a crucial role in understanding the observed neutrino oscillations and explaining the observed baryon asymmetry in the universe via leptogenesis. The PQ symmetry helps resolve the strong CP problem and also provides axion as a compelling dark matter (DM) candidate. The $U(1)_X$ gauge symmetry enables us to implement the inflection-point inflation scenario with $H_{inf} \lesssim 2 \times 10^{7}$ GeV, where $H_{inf}$ is the value of Hubble parameter during inflation. This allows us to overcome a potential axion domain wall problem as well as the axion isocurvature problem. The SMART U(1)$_X$ model can be merged with $SU(5)$ as we briefly show., 18 pages, 2 figures

The Gatto Sartori Tonin (GST) relation which establishes the Cabibbo angle in terms of the quark mass ratio: $\theta_{C}=\sqrt{m_d/m_s}$, is instituted as $\theta_{13}=\sqrt{m_1/m_3}$ to a Bi-large motivated lepton mixing framework that relies on the unification of mixing parameters: $\theta_{13}=\theta_{C}$ and $\theta_{12}=\theta_{23}$. This modification in addition to ruling out the possibility of vanishing $\theta_{13}$, advocates for a nonzero lowest neutrino mass and underlines the normal ordering of the neutrino masses. The framework is further enhanced by the inclusion of a charged lepton diagonalizing matrix $U_{lL}$ with $ (\theta_{12}^l \sim \theta_C, \delta=0)$. The model being architected at the Grand unification theory (GUT) scale is further run down upto the $Z$ boson scale to understand the universality of the GST relation and the Cabibbo angle., Comment: 14 pages, 10 figures, 2 tables

New matter fields charged under the strong nuclear force would have dramatic phenomenological implications. Here, we systematically explore how these new states, which we postulate belong to some representation of SU(3) of quantum chromo-dynamics, could interact with Standard Model fields: We analyze all lowest-dimensional "portal" operators for any SU(3) representation and, motivated by grand unification, we extend our results to SU($N$), for $N>3$. We provide a publicly available python code, "tessellation", that automatically constructs said lowest-dimensional portal operators for any new exotic matter field charged under SU($N$) for any $N$., 16 pages, 7 figures

We analyze the Next-to-minimal supersymmetric standard model with Grand unification boundary conditions under current theoretical and experimental constraints. We compute the mass spectrum of the model and focus on the three lightest particles in the Higgs sector (two CP-even scalars, $h_1, h_2$, and one CP-odd, $a_1$). The reduced couplings of such particles, singlet-doublet components, their branching ratios to bosons, and reduced cross-section to photons and massive gauge bosons via gluon fusion are thoroughly and systematically scrutinized. Our analysis is focused on the parameter space where the singlet-doublet coupling $\lambda$ is as large as possible (keeping the perturbativity bound intact) and the ratio between the vacuum expectation values of the up-type and down-type Higgses ($\tan{\beta}$) is as small as possible, which is the region representing the most natural case of the NMSSM. We show the impact of recent constraints from the LHC on the SM-Higgs couplings to bosons and fermions on the parameter space of the model and the consequent implications on the Higgs sector. The results show that while the model is still able to account for current data and provide an opportunity for discovery of extended Higgs sectors, recent LHC Higgs couplings constraints rule-out parts of the parameter space where $h_2$ (non-SM-like) and $a_1$ are non-singlet with masses below ~400 GeV., Comment: MPLA accepted version

Physics letters / B 811, 135914 (1-4) (2020). doi:10.1016/j.physletb.2020.135914, We interpret the recent NANOGrav results in terms of a stochastic gravitational wave background from metastable cosmic strings. The observed amplitude of a stochastic signal can be translated into a range for the cosmic string tension and the mass of magnetic monopoles arising in theories of grand unification. In a sizable part of the parameter space, this interpretation predicts a large stochastic gravitational wave signal in the frequency band of ground-based interferometers, which can be probed in the very near future. We confront these results with predictions from successful inflation, leptogenesis and dark matter from the spontaneous breaking of a gauged B − L symmetry., Published by North-Holland Publ., Amsterdam

Publisher's version (útgefin grein), Despite the successes of the Standard Model of particle physics, it is known to suffer from a number of deficiencies. Several of these can be addressed within non-supersymmetric theories of grand unification based on SO(10). However, achieving gauge coupling unification in such theories is known to require additional physics below the unification scale, such as symmetry breaking in multiple steps. Many such models are disfavored due to bounds on the proton lifetime. Corrections arising from threshold effects can, however, modify these conclusions. We analyze all seven relevant breaking chains with one intermediate symmetry breaking scale, assuming the “survival hypothesis” for the scalar masses. Two are allowed by proton lifetime and two are disfavored by a failure to unify the gauge couplings. The remaining three unify at a too low scale, but can be salvaged by various amounts of threshold corrections. We parametrize this and thereby rank the models by the size of the threshold corrections required to save them., The authors wish to thank Sofiane M. Boucenna for collaboration in early stages of this project and Erik Sönnerlind for pointing out errors and clarifying issues with numerics in a draft of this manuscript. T.O. acknowledges support by the Swedish Research Council (Vetenskapsrådet) through contract No. 2017-03934 and the KTH Royal Institute of Technology for a sabbatical period at the University of Iceland. M.P. thanks “Stiftelsen Olle Engkvist Byggmästare” and “Roland Gustafssons Stiftelse för teoretisk fysik” for financial support. Numerical computations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at PDC Center for High Performance Computing (PDC-HPC) at KTH Royal Institute of Technology in Stockholm, Sweden under project numbers SNIC 2018/3-559 and SNIC 2020/5-122.

We explore possible signatures for charged lepton flavour violation (LFV), sparticle discovery at the LHC and dark matter (DM) searches in grand unified theories (GUTs) based on SU(5), flipped SU(5) (FSU(5)) and SU(4)$_c \times $SU(2)$_L \times $SU(2)$_R$ (4-2-2). We assume that soft supersymmetry-breaking terms preserve the group symmetry at some high input scale, and focus on the non-universal effects on different matter representations generated by gauge interactions at lower scales, as well as the charged LFV induced in Type-1 see-saw models of neutrino masses. We identify the different mechanisms that control the relic DM density in the various GUT models, and contrast their LFV and LHC signatures. The SU(5) and 4-2-2 models offer good detection prospects both at the LHC and in LFV searches, though with different LSP compositions, and the SU(5) and FSU(5) models offer LFV within the current reach. The 4-2-2 model allows chargino and gluino coannihilations with neutralinos, and the former offer good detection prospects for both the LHC and LFV, while gluino coannihilations lead to lower LFV rates. Our results indicate that LFV is a powerful tool that complements LHC and DM searches, providing significant insights into the sparticle spectra and neutrino mass parameters in different models., Comment: 27 pages, 8 figures

Spontaneous breaking of conformal symmetry has been widely exploited in successful model building of both inflationary cosmology and particle physics phenomenology. Conformal Grand Unified Theory (CGUT) inflation provides the same scalar tilt and tensor-to-scalar ratio as of Starobinsky and Higgs inflation. Moreover, it predicts a proton life time compatible with the current experimental bound. In this paper, we extend CGUT to account for the production of dark matter and the reheating of the Standard Model. To this end, we introduce a hidden sector directly coupled to the inflaton, whereas the reheating of the visible sector is realized through a portal coupling between the dark particles and the Higgs boson. The masses and interactions of the dark particles and the Higgs boson are determined by the form of the conformal potential and the non-vanishing VEV of the inflaton. We provide benchmark points in the parameter space of the model that give the observed dark matter relic density and reheating temperatures compatible with the Big Bang nucleosynthesis., 38 pages, 9 figures, matches published version

We propose an $SU(3)_C\times SU(2)_L \times SU(2)_N \times U(1)_Y$ model arising from $E_6$ grand unified theory. We show that the tiny neutrino masses in this model can be generated at the three-loop involving the $SU(2)_N$ gauge bosons. With Yukawa couplings around 0.01 or larger and TeV-scale $SU(2)_N$ gauge bosons, we show that the neutrino oscillation data can be explained naturally by presenting a concrete benchmark set of input parameters. All new particles are around the TeV scale. Thus our model can be tested at the ongoing/future collider experiments., Comment: 13 pages, 2 figure

We show that a minimal local $B-L$ symmetry extension of the standard model can provide a unified description of both neutrino mass and dark matter. In our model, $B-L$ breaking is responsible for neutrino masses via the seesaw mechanism, whereas the real part of the $B-L$ breaking Higgs field (called $\sigma$ here) plays the role of a freeze-in dark matter candidate for a wide parameter range. Since the $\sigma$-particle is unstable, for it to qualify as dark matter, its lifetime must be longer than $10^{25}$ seconds implying that the $B-L$ gauge coupling must be very small. This in turn implies that the dark matter relic density must arise from the freeze-in mechanism. The dark matter lifetime bound combined with dark matter relic density gives a lower bound on the $B-L$ gauge boson mass in terms of the dark matter mass. We point out parameter domains where the dark matter mass can be both in the keV to MeV range as well as in the PeV range. We discuss ways to test some parameter ranges of this scenario in collider experiments. Finally, we show that if instead of $B-L$, we consider the extra $U(1)$ generator to be $-4I_{3R}+3(B-L)$, the basic phenomenology remains unaltered and for certain gauge coupling ranges, the model can be embedded into a five dimensional $SO(10)$ grand unified theory., Comment: 18 pages and six figures

We consider leptogenesis in a left-right-symmetric seesaw scenario in which neutrino mass generation and leptogenesis are dominated by the type-II seesaw term. Motivated by grand unification, we assume that the neutrino Dirac mass matrix is dominated by a single entry of the order of the top-quark mass, which leaves the low-energy phases of the lepton mixing matrix as the only sources of CP violation. Working in a regime where the triplet scalar predominantly decays into leptons, this results in a predictive scenario based on a minimal number of parameters. We perform a detailed analysis of the flavored Boltzmann equations within a revised density matrix framework and demonstrate that the observed baryon asymmetry can be successfully generated in this simple model. We point out that the significance of flavor effects is limited, and we discuss the implications for low-energy observables such as the Dirac CP phase and neutrinoless double beta decay., Comment: 40 pages, 9 figures, 3 tables; minor text revisions, new benchmark values, plots and results updated, matches published version in NPB

Within the extended BLMSSM, the exotic Higgs superfields $$(\Phi _{NL},\varphi _{NL})$$ are added to make the exotic leptons heavy, and the superfields ( $$Y,Y^\prime $$ ) are also introduced to make exotic leptons unstable. This new model is named as the EBLMSSM. We study some charged lepton flavor violating (CLFV) processes in detail in the EBLMSSM, including $$l_j\rightarrow l_i \gamma $$ , muon conversion to electron in nuclei, the $$\tau $$ decays and $$h^0\rightarrow l_i l_j$$ . Being different from BLMSSM, some particles are redefined in this new model, such as slepton, sneutrino, exotic lepton (neutrino), exotic slepton (sneutrino) and lepton neutralino. We also introduce the mass matrices of superfields Y and spinor $$\tilde{Y}$$ in the EBLMSSM. All of these lead to new contributions to the CLFV processes. In the suitable parameter space, we obtain the reasonable numerical results. The results of this work will encourage physicists to explore new physics beyond the SM.

Symmetries of the physical world have guided formulation of fundamental laws, including relativistic quantum field theory and understanding of possible states of matter. Topological defects (TDs) often control the universal behavior of macroscopic quantum systems, while topology and broken symmetries determine allowed TDs. Taking advantage of the symmetry-breaking patterns in the phase diagram of nanoconfined superfluid $^3$He, we show that half-quantum vortices (HQVs) -- linear topological defects carrying half quantum of circulation -- survive transitions from the polar phase to other superfluid phases with polar distortion. In the polar-distorted A phase, HQV cores in 2D systems should harbor non-Abelian Majorana modes. In the polar-distorted B phase, HQVs form composite defects -- walls bounded by strings hypothesized decades ago in cosmology. Our experiments establish the superfluid phases of $^3$He in nanostructured confinement as a promising topological media for further investigations ranging from topological quantum computing to cosmology and grand unification scenarios., Comment: 17 pages, 11 figures

We determined the quark mass matrix in terms of a small expansion parameter $\sqrt{\varepsilon}$, which gives correctly all the quark masses and the CKM matrix elements at the electroweak (EW) scale, and obtain a progenitor form at the GUT scale by running the EW scale mass matrix. Finally, a possible texture form for the progenitor quark mass matrix is suggested., 7 pages, 1 figure

Compared to the minimal supersymmetric standard model, an extension by vectorlike fermions is able to explain the Higgs mass while retains the grand unification. We investigate the minimal vectorlike model by focusing on the vectorlike electroweak sector. We firstly derive the mass spectrum in the electroweak sector, then calculate the one-loop effects on the Higgs physics, and finally explore either vectorlike or neutralino dark matter. Collider constraints are briefly discussed., 18 pages, to match published version

We perform a detailed investigation of a Grand Unified Theory (GUT)-inspired theory of gauge-Higgs unification. Scanning the model's parameter space with adapted numerical techniques, we contrast the scenario's low energy limit with existing SM and collider search constraints. We discuss potential modifications of di-Higgs phenomenology at hadron colliders as sensitive probes of the gauge-like character of the Higgs self-interactions and find that for phenomenologically viable parameter choices modifications of the order of 20\% compared to the SM cross section can be expected. While these modifications are challenging to observe at the LHC, a future 100 TeV hadron collider might be able to constrain the scenario through more precise di-Higgs measurements. We point out alternative signatures that can be employed to constrain this model in the near future., 10 pages, 9 figures, 1 table; v2: references added, version published in PLB

We discuss the current status of lepton flavour universality observables in semileptonic charged and neutral current $B$ meson decays. We recapitulate the current experimental situation. Assuming the current tensions with the SM are of beyond the Standard Model origin we present their implications for the effective theory couplings. Then we discuss general leptoquark models before finally focussing on the model with two scalar leptoquarks ($R_2$ and $S_3$) which have couplings connected by the underlying Grand Unified Theory framework. We present the viability of the model with regard to lepton flavour universality and present opportunities to search for this model in future high-intensity and high-energy experiments, 12 pages, 3 figures Presented at 18th International Conference on B-Physics at Frontier Machines - Beauty2019

We study low-scale gauge mediated supersymmetry breaking models with a very light gravitino of mass $\mathcal{O}(1)$ eV. The cosmological upper bound on the gravitino mass and the collider constraints on the sparticle masses give a significant impact on such models. We apply the latest results of the LHC to these models and obtain the current constraints. We find that perturbatively calculable classes of low-scale gauge mediation models can be largely excluded., Comment: 19 pages, 5 figures