The unification of gauge interactions in the context of Adjoint SU(5) and its phenomenological consequences are investigated. We show the allowed mass spectrum of the theory which is compatible with proton decay, and discuss the possibility to have a cold dark matter candidate. Due to the upper bounds on the proton decay partial lifetimes, tau (p --> K^+ nubar) < 9.3 10^{36} years and tau(p --> pi^+ nubar) < 3.0 10^{35} years, the theory could be tested at future proton decay experiments. The theory predicts also light scalar color octets which could be produced at the Large Hadron Collider.
We analyze the relation between the present (and foreseen) bounds on matter stability and the presence of TeV-scale color octet scalar states in nonsupersymmetric SO(10) grand unification with one adjoint Higgs representation triggering the symmetry breaking. This scenario, discarded long ago due to tree-level tachyonic instabilities appearing in all phenomenologically viable breaking patterns, has been recently revived at the quantum level. By including the relevant two-loop corrections we find a tight correlation between the octet mass and the unification scale which either requires a light …
The minimal dark matter (MDM) scenario is a very simple framework of physics beyond the Standard Model (SM) to supplement the SM with a DM candidate. In this paper, we consider an ultraviolet completion of the scenario to an SO(10) grand unified theory, which is a well-motivated framework in light of the neutrino oscillation data. Considering various phenomenological constraints, such as the successful SM gauge coupling unification, the proton stability, and the direct/indirect DM detection constraints as well as the absolute electroweak vacuum stability, we have first singled out the minimal …
We study the properties and production mechanisms of color-octet scalars at the LHC. We focus on the single production of both charged and neutral members of an (8,2)_1/2 doublet through bottom quark initial states. These channels provide a window to the underlying Yukawa structure of the scalar sector. Color-octet scalars naturally appear in grand unified theories based on the SU(5) gauge symmetry. In the context of adjoint SU(5) these fields are expected to be light to satisfy constraints coming from unification and proton decay, and may have TeV-scale masses. One combination of their coupli…
We study the phenomenology of the pair-production of scalar color-octet electroweak singlet states at the LHC. Such states appear in many extensions of the Standard Model. They can be pair-produced copiously at the LHC and will signal themselves as resonances in multijet final states. Beyond the QCD pair-production process we consider a vectorlike confinement scenario with an additional color-octet vector state. These vector particles can be produced in the s-channel and through their decay contribute to the scalar pair production. We point out the differences between the two hypotheses and de…
We explore the phenomenology of scalar fields in the adjoint representation of SM gauge groups. We write a general set of dimension 5 effective operators in which SM adjoint scalars couple to pairs of standard model bosons. Using these effective operators, we explore new possible decay channels of a scalar color octet into a gluon and a Z boson/ gluon and a photon. We recast several analyses from Run I of the LHC to find constraints on an a scalar octet decaying into these channels, and we project the discovery potential of color octets in our gluon+photon channel for the 14 TeV run of LHC.
I present two new renormalizable grand unified theories where the neutrino masses are generated through the type I and type III seesaw mechanisms. These theories can be considered as the simplest (SUSY) renormalizable grand unified theories based on the SU(5) gauge symmetry. Several phenomenological and cosmological aspects of these proposals are discussed.
We show how gauge coupling unification is successfully implemented through non-supersymmetric grand unified theory, $SO(10)\times G_f (~G_f=S_4, SO(3)_f, SU(3)_f)$, using low-scale flavor symmetric model of the type $SU(2)_L\times U(1)_Y$ $ \times SU(3)_C \times S_4$ recently proposed by Hagedorn, Lindner, and Mohapatra, while assigning matter-parity discrete symmetry for the dark matter stability. For gauge coupling unification in the single-step breaking case, we show that a color-octet fermion and a hyperchargeless weak-triplet fermionic dark matter are the missing particles needed to compl…
Color scalars are salient features of non-minimal SU(5) model, where Higgs sector is extended by 45-dimensional multiplet. We show that gauge coupling unification can be realized in this model with TeV octet scalar and intermediate (~10^6 GeV) color-triplet scalar at scale larger than 10^{15} GeV. We analyze the possible LHC signatures of these TeV octet scalars. We emphasize that multi-(b)-jet final states provide significant signal for direct probe of octet scalars at the LHC.
We revisit an extension of the Standard Model with Majorana fermions in the adjoint representations. There, a precise coupling unification and the good candidate for dark matter (the $SU(2)_L$ triplet fermion) are achieved simultaneously. In particular, we show that the $SU(3)_c$ octet fermion which is required for successful unification can be a good non-thermal source of the triplet fermion dark matter. We also show that the scenario predicts a rather short lifetime of the proton compared with the supersymmetric Standard Model, and the most parameter space can be explored by the future exper…
Following the suggestion of Bachas, Fabre and Yanagida (BFY), we analyze the gauge coupling unification at the two-loop order, in a supersymmetric scenario where scalars belonging to the adjoint representations contribute to the evolution of the couplings from intermediate scales onward, and the unification scale is pushed towards the string scale. Thereafter, we compare the masses of these adjoint scalars to the scale at which the hidden sector gauge coupling reaches the non-perturbative limit at the two-loop order for various possible hidden sector gauge groups motivated by the the conjectur…
Here we ask if it is possible to have string unification in $\mathsf{SU(5)\times SU(5)}$ gauge group. We specifically investigate the weakly coupled heterotic string unification for the four couplings in this framework. We show that only a limited versions of $\mathsf{SU(5)\times SU(5)}$ with adjoint representation components at intermediated scales, between $M_Z$ and $Λ$ (unification), are allowed. This is essentially due to the limitation in the parameter space to the gauge coupling constant $α_1^{-1}$ related to hypercharge. Indeed, only the vanishing hypercharge decompositions of $\mathsf{…
We consider states in the adjoint representation of the Standard Model gauge group as messengers for mediation of supersymmetry (SUSY) breaking. These new messengers can shift the gauge coupling unification to the string scale at O(5x10^{17} GeV) if their masses are at O(10^{14} GeV). The predicted SUSY mass spectrum at the electroweak scale is significantly different from those in other gauge-mediated or supergravity models, resulting in robust mass relations. The gravitino mass is predicted to be about 1-10 GeV. The heavy messenger sector could provide a superheavy dark matter candidate.
There are several advantages of introducing adjoint superfields at intermediate energies around $M=10^{13}$ GeV. Such as (i) gauge couplings still unify (ii) neutrino masses and mixings are produced (iii) primordial lepton asymmetry can be produced. We point out that if adjoint scalars have bulk excitations along with gauge bosons whereas fermions and the doublet scalar live on boundary then N=2 supersymmetric beta functions $\tilde{b_i}$ vanish. Thus even if extra dimensions open up at an intermediate scale $μ_0$ and all N=2 Yang-Mills fields as well as N=2 matter fields in the adjoint repres…
By dressing Polyakov lines with appropriate functionals of the gauge fields, we construct observables describing a fundamental representation static quark-antiquark pair in the singlet, adjoint and average channels of SU(N) pure gauge theory. Each of the potentials represents a gauge invariant eigenvalue of the Hamiltonian. Numerical simulations are performed for SU(2) in 2+1 dimensions. The adjoint channel is found to be repulsive at small and confining at large separations, suggesting the existence of a metastable (N^2-1)-plet bound state. For small distances and temperatures above the decon…
We present a gauge mediated supersymmetry breaking model having weak SU(2) triplet, color SU(3) octet and SU(5) 5-plet messengers, that can simultaneously explain the muon $(g-2)$ data within 1$σ$ and the observed Higgs boson mass of 125 GeV. Gauge coupling unification is nontrivially maintained. Most of the parameter space satisfying both is accessible to the 14 TeV LHC. The lighter of the two staus weighs around (100-200) GeV, which can be a potential target of the ILC.
We evaluate the next-to-next-to-leading order soft function for the production of a massive color octet state at rest in the collision of two massless colored partons in either the fundamental or the adjoint representation. The main application of our result is the determination of the threshold expansion of the heavy-quark pair-production cross sections in the quark annihilation and gluon fusion channels. We discuss the factorization necessary for this purpose and explain the relationship between hard functions and virtual amplitudes.
Barbieri and Hall have argued that threshold effects at the scale of grand-unification wipe out predictions on the SUSY scale, M_S. Using triviality arguments we give upper bounds on ultraheavy particles, while proton stability gives lower bounds on the mass of the higgs color-triplet. We find no useful lower bound on the $Σ$ supermultiplet, but if the strong coupling constant is as large as recent experiments suggest, unification in the minimal SUSY SU(5) model requires that the $Sigma$ masses be $\sim 10^{-7}M_V$ and that the color octet and weak triplet be split in mass by a factor of $\sim…
Recently we have proved color octet NRQCD factorization of S-wave heavy quarkonium production at all orders in coupling constant at high energy colliders in Eur. Phys. J. C76 (2016) 448. In this paper we extend this to prove color octet NRQCD factorization of P-wave heavy quarkonium production at all orders in coupling constant at high energy colliders. We find that while the color octet NRQCD S-wave non-perturbative matrix element contains two gauge-links in the adjoint representation of SU(3), the color octet NRQCD P-wave non-perturbative matrix element contains four gauge-links in the funda…
We propose a simple renormalizable grand unified theory based on the $SU(5)$ gauge symmetry where the neutrino masses are generated at the quantum level through the Zee mechanism. In this model the same Higgs needed to correct the mass relation between charged leptons and down-type quarks plays a crucial role to generate neutrino masses. We show that in this model one can satisfy the constrains coming from the unification of gauge couplings and the mechanism for neutrino masses is discussed in detail. The predictions for proton decay are discussed in order to understand the testability at curr…
As the mass limits on supersymmetric particles are gradually pushed to higher values due to their continuing non-observation at the CERN LHC, looking for focus point regions in the supersymmetric parameter space, which shows considerably reduced fine-tuning, is increasingly more important than ever. We explore this in the context of gauge mediated supersymmetry breaking with messengers transforming in the adjoint representation of the gauge group, namely, octet of color SU(3) and triplet of weak SU(2). A distinctive feature of this scenario is that the focus point is achieved by fixing a singl…
We investigate the interaction between a heavy quark-antiquark pair in color octet configuration in gluon plasma. We calculate nonperturbatively an effective thermal potential for such a pair through the study of the correlation function of a hybrid state with $Q \bar{Q}$ octet and an adjoint gluon source in the static limit. We discuss the extraction of an octet potential, and present results for the effective thermal potential between octet $Q \bar{Q}$ pair in gluon plasma for moderately high temperatures $\lesssim 2 T_c$. The implications of our result are discussed.
Building up on previous work we propose a Dark Matter (DM) model with gauged matter parity and dynamical gauge coupling unification, driven by the same physics responsible for scotogenic neutrino mass generation. Our construction is based on the extended gauge group \3311, whose spontaneous breaking leaves a residual conserved matter parity, $M_{P}$, stabilizing the DM particle candidates of the model. A key role is played by the Majorana ${\rm SU(3)_{L}}$-octet leptons, in allowing successful gauge coupling unification and one-loop scotogenic neutrino mass generation. Theoretical consistency …
Minimal supersymmetric SU(5) with exact unification is naively inconsistent with proton decay constraints. However, it can be made viable by a gravity-induced non-renormalizable operator connecting the adjoint Higgs boson and adjoint vector boson representations. We compute the allowed coupling space for this theory and find natural compatibility with proton decay constraints even for relatively light superpartner masses. The modifications away from the naive SU(5) theory have an impact on the gaugino mass spectrum, which we calculate. A combination of precision Linear Collider and Large Hadro…
Dynamical gauge-Higgs unification is presented in higher dimensional gauge theory, in which both adjoint and fundamental Higgs fields are a part of gauge fields. Dynamical gauge symmetry breaking is induced through the Hosotani mechanism. Gauge theory, including the U(3) x U(3) model, is examined on M^4 x (T^2/Z_2).
We propose a novel way to break grand unified gauge symmetries via the Hosotani mechanism in models that can accommodate chiral fermions. Adjoint scalar fields are realized through the so-called diagonal embedding method which is often used in the heterotic string theory. We calculate the one-loop effective potential of the adjoint scalar field in a five dimensional model compactified on an S^1/Z_2 orbifold, as an illustration. It turns out that the potential is basically the same as the one in an S^1 model, and thus the results in literatures, in addition to the chiral fermions, can be realiz…
Influenced by the current trend of experimental data, especially from the LHC, we construct a supersymmetric scenario where a natural dynamics makes the squarks and gluino super-heavy (order 10 TeV) while keeping the sleptons and the weak gauginos light (100-500 GeV). The dynamics relies on the interfusion of two underlying ideas: ($i$) gauge mediation of supersymmetry breaking with two messenger multiplets, one transforming as a triplet of weak SU(2) and the other as an octet of color SU(3); ($ii$) perturbative gauge coupling unification at the string scale even with these incomplete SU(5) mu…
The idea of grand unification in a minimal supersymmetric SU(5)xSU(5) framework is revisited. It is shown that the unification of gauge couplings into a unique coupling constant can be achieved at a high-energy scale compatible with proton decay constraints. This requires the addition of a minimal particle content at intermediate energy scales. In particular, the introduction of the SU(2)_L triplets belonging to the (15,1)+(\bar{15},1) representations, as well as of the scalar triplet Σ_3 and octet Σ_8 in the (24,1) representation, turns out to be crucial for unification. The masses of these i…
The significant heavy threshold effect is found in the supersymmetric SU(5) model with two adjoint scalars, one of which is interpreted as a massive string mode decoupled from the lower-energy particle spectra. This threshold related with the generic mass splitting of the basic adjoint moduli is shown to alter properly the running of gauge couplings, thus giving a natural solution to the string-scale grand unification as prescribed at low energies by LEP precision measurements and minimal particle content. The further symmetry condition of the (top-bottom) Yukawa and gauge coupling superunific…
We argue that moduli in the adjoint representation of the standard- model gauge group are a natural feature of superstring models, and that they can account for the apparent discrepancy between the string and unification scales.
We consider a small extension of the standard model by adding two Majorana fermions; those are adjoint representations of the SU(2)_L and SU(3)_c gauge groups of the standard model. In this extension, the gauge coupling unification at an energy scale higher than 10^{15} GeV is realized when the masses of the triplet and the octet fermions are smaller than 10^4 GeV and 10^{12} GeV, respectively. We also show that an appropriate symmetry ensures a long lifetime of the neutral component of the triplet fermion whose thermal relic density naturally explains the observed dark matter density. The ele…
We propose a unification scenario for supersymmetric intersecting brane models. The quarks and leptons are embedded into adjoint representations of SO(32), which are obtained and break by type I string compactified on orbifolds. Its single unified gauge coupling can give rise to different gauge couplings below the unification scale, due to effects of magnetic fluxes. The crucial mechanism is brane recombination preserving supersymmetry.
I review the unification of gauge couplings of strong, weak and electro-magnetic interactions. I start by recalling the history of the most important prediction of low-energy supersymmetry: the correct value of the weak mixing angle tied to a large top quark mass. I then turn to the discussion of the present day situation of the minimal supersymmetric Grand Unified Theories based on SU(5) and SO(10) groups, and I show why the minimal SU(5) is in accord with experiment. For the sake of completeness I also summarize the problems and possible solutions of the minimal ordinary SU(5). One version, …
We consider the possibility of gauge coupling unification within the simplest realizations of the $\mathrm{SU(3)_c \times SU(3)_L \times SU(3)_R \times U(1)_{X}}$ gauge theory. We present a first exploration of the renormalization group equations governing the "bottom-up" evolution of the gauge couplings in a generic model with free normalization for the generators. Interestingly, we find that for a $\mathrm{SU(3)_c \times SU(3)_L \times SU(3)_R \times U(1)_{X}}$ symmetry breaking scale $M_X$ as low as a few TeV one can achieve unification in the presence of leptonic octets. We briefly comment…
We consider the impact of colored scalars that can couple directly to matter fields on the recently measured h to gamma gamma excess. Among all possible candidates only scalar states transforming as (8, 2,1/2) and (6,3,1/3) under the Standard Model gauge group can individually accommodate the excess and remain in agreement with all available data. Current experimental constraints require such colored states to have an order one coupling to the Standard Model Higgs and a mass below 300 GeV. We use the best fit values to predict the correlated effect in h to Z gamma and di-Higgs production. We f…
The non-supersymmetric SU(5) model can accommodate heavy neutrinos and gauge coupling unification when augmented with an adjoint fermionic multiplet 24_F. Among the most important phenomenological implications of the model is the prediction of light fermions and scalars, charged under the SU(2) gauge group, in the reach of the Large Hadron Collider (LHC). In this talk, we report on the recent calculation of the correlation function between the mass scale of the new electroweak multiplets and the gauge coupling unification scale at three loop accuracy.
We propose a focus point gauge mediation model based on the product group unification (PGU), which solves the doublet-triplet splitting problem of the Higgs multiplets. In the focus point gauge mediation, the electroweak symmetry breaking scale can be naturally explained even for multi-TeV stops. It is known that the focus point behavior appears if a ratio of the number of SU(2) doublet messengers to that of SU(3) triplet messengers is close to 5/2. Importantly, this ratio (effectively) appears in our scenario based on the PGU, if the messenger field is an adjoint representation of SU(5) gauge…
We show that models of the Dirac gaugino can naturally be embedded into a kind of the grand unified theory (GUT), the grand gauge-Higgs unification (gGHU) model, with the gauge group SU(5)\times SU(5)/Z_2 on an S^1/Z_2 orbifold. The supersymmetric gGHU is known to posess a light chiral adjoint supermultiplet after the GUT breaking, thank to the exchange symmetry of two SU(5) groups. Identifying the `predicted' adjoint fermion with the Dirac partner of the gaugino, we argue that the supersoft term, responsible for the Dirac gaugino mass, can be obtained from the supersymmetric Chern-Simons (CS)…
Gauge fields and both adjoint and fundamental Higgs fields are unified in gauge theory defined on an orbifold. It is shown how the Hosotani mechanism at the quantum level resolves the problem of the arbitrariness in boundary conditions imposed at the fixed points of the orbifold. The role of adjoint Higgs fields in the standard GUT, which are extra-dimensional components of gauge fields in the current scheme, is taken by the Hosotani mechanism and additional dynamics governing the selection of equivalence classes of boundary conditions. The roles of fundamental Higgs fields, namely those of in…
We consider 5 dimensional E_6 and E_7 supersymmetric grand unified theories (GUTs) on an orbifold S^1/Z_2, in which the Higgs fields arise from the 5th components of the 5D gauge fields. We introduce matter fields in 5 dimensions, then the Yukawa interactions are induced from the gauge interactions among the 5th component of gauge fields and the bulk hyper-multiplets. The adjoint and fundamental representations of bulk matter fields can induce all Yukawa interactions of the standard model in E_6 GUT. Furthermore, realistic fermion mass hierarchies and flavor mixings with the CP violating phase…
It is demonstrated how the hierarchy between the gauge coupling unification scale of minimal supersymmetry and the Planck (or string) scale, which resembles in order of magnitude a loop factor, can actually be explained as such in supergravity-coupled supersymmetry. A gauge and global singlet field acquires a linear potential term due to its one-loop supergravity interactions and slides to the desired scale. The singlet field can then provide the seed for the breaking of the unified theory at the appropriate scale via its couplings to fields in the adjoint representation.
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 enha…
Supersymmetric models in which the gauginos acquire Dirac masses, rather than Majorana masses, offer an appealing alternative to the minimal supersymmetric standard model, especially in the light of the bounds set on superpartner masses by the 2011 LHC data. Dirac gauginos require the presence of chiral multiplets in the adjoint representation of the gauge group, and the realisation of such scenarios in F-theory is the subject of this paper. The chiral adjoints drastically alter the usual picture of gauge coupling unification, but this is disturbed anyway in F-theory models with non-trivial hy…
We present a supersymmetric SU(5) x U(1)_H model, free from gauge anomalies, where the Abelian factor U(1)_H, introduced to account for the hierarchy of fermion masses and mixings, is broken by the same adjoint representations of SU(5) that also break the GUT symmetry. The model predicts approximate, but never exact, bottom-tau Yukawa unification. The deviations are related to group theoretical coefficients and can naturally be at the level of 10%-20%.
We investigate a 5D SU(6) grand gauge-Higgs unification model compactified on an orbifold S^1/Z_2. Ordinary quarks and leptons, together with right-handed neutrinos, are just accommodated into a minimal set of representations of the gauge group, without introducing any exotic states. The proton decay turns out to be forbidden at least at the tree level. We also find a correct electroweak symmetry breaking SU(2)_L \times U(1)_Y \to U(1)_{em} is easily realized by introducing suitable number of adjoint fermions.
We investigate more generally the possible unification Yang-Mills groups $G_{YM}$ and representations with CP as a gauge symmetry. Besides the possible Yang-Mills groups $E_8$, $E_7$, $SO(2n+1)$, $SO(4n)$, $SP(2n)$, $G_2$ or $F_4$ (or a product of them) which only allow self-contragredient representations, we present other unification groups $G_{YM}$ and representations which may allow CP as a gauge symmetry. These include especially $SU(N)$ containing Weyl fermions and their CP-conjugates from low-energy spectra in a basic irreducible representation (IR). Such an example is the 496-dimensiona…
We review the current status of the minimal non-supersymmetric SO(10) grand unified theory and perform a detailed next-to-leading-order analysis of the gauge unification and proton lifetime constraints on the part of its parameter space supporting a ZeV-scale color sextet scalar. This, together with a TeV-scale color octet studied in detail in a preceding work, represents one of the two minimally fine-tuned settings compatible with all the relevant consistency and phenomenology limits. Both these scenarios can be extensively tested at the future megaton-scale proton-decay facilities. On top of…
The theory that the extra-space component of the gauge field is identified with the standard model Higgs boson, is called the gauge-Higgs unification (GHU) scenario. We examine how the small neutrino masses are naturally generated in the GHU framework. We find out two model classes where the following matter multiplets are introduced : 1. adjoint rep. lepton $Ψ_{A}$, 2. fundamental rep. lepton $Ψ_{F}$ and scalar $Σ_{F}$. We present a concrete model in each class. At the model in class 1, the neutrino masses are generated by the admixture of the seesaw mechanism type-I and -III. At the model in…
We investigate the possibility to find the simplest renormalizable grand unified theory based on the SU(5) gauge symmetry. We find that it is possible to generate all fermion masses with only two Higgs bosons, 5_H and 45_H. In this context the neutrino masses are generated through the type III and type I seesaw mechanisms. The predictions coming from the unification of gauge couplings and the stability of the proton are discussed in detail. In this theory the leptogenesis mechanism can be realized through the out of equilibrium decays of the fermions in the adjoint representation.
Two models which generate the supersymmetric Grand Unification Scale from the strong dynamics of an additional gauge group are presented. The particle content is chosen such that this group confines with chiral symmetry breaking. Fields that are usually introduced to break the Grand Unified group appear instead as composite degrees of freedom and can acquire vacuum expectation values due to the confining dynamics. The models implement known solutions to the doublet-triplet splitting problem. The SO(10) model only requires one higher dimensional representation, an adjoint. The dangerous coloure…
In this talk, we discuss an attempt to construct a realistic model of the grand gauge-Higgs unification. We investigate a 5D SU(6) grand gauge-Higgs unification model compactified on an orbifold S^1/Z_2. Ordinary quarks and leptons, together with right-handed neutrinos, are just accommodated into a minimal set of representations of the gauge group, without introducing any exotic states in the same representations. The proton decay turns out to be forbidden at least at the tree level. We also find a correct electroweak symmetry breaking SU(2)_L \times U(1)_Y \to U(1)_{em} is easily realized by …
A realistic extension of the minimal $SU(5)$ theory consisting of the addition of an adjoint fermion is known to predict light real fermion and scalar weak triplets, potentially accessible at the LHC. These particles, in addition to playing a key role in gauge coupling unification, have profound phenomenological implications. The fermion triplet, that through the seesaw mechanism offers a testable origin of neutrino mass, has been already extensively discussed. The scalar triplet develops a vacuum expectation value that modifies the $W$-boson mass. We show that its low-energy effective theory …
We present a new solution to the doublet-triplet splitting problem which also works in a supersymmetric SU(5) grand unified theory and is testable at TeV-scale collider experiments. In our model, the SU(5) symmetry is broken through the Hosotani mechanism. Thanks to the phase nature of the Hosotani-breaking, the "missing VEV" can be realized even in an SU(5) model. A general and distinctive prediction of this solution is the existence of light adjoint chiral supermultiplets with masses of the supersymmetry breaking scale. Though these disturb the gauge coupling unification, it can be recovered…
To solve the doublet-triplet splitting problem in SU(5) grand unified theories, we propose a four dimensional orbifold grand unified theory by acting Z2 on the SU(5) gauge group. Without an adjoint Higgs, the orbifold procedure breaks the SU(5) gauge symmetry down to the standard model gauge group, and removes the triplet component of the fundamental SU(5) Higgs. In the supersymmetric framework, we show that the orbifold procedure removes two triplet superfields of the Higgs multiplets and leaves us with the minimal supersymmetric standard model, which also solves the hierarchy problem and rea…
Five-dimensional $SU(3)$ gauge-Higgs unification models are studied at finite temperature in the warped extra dimension $S^1/\mathbb{Z}_2$. In order to investigate the phase structure, we developed a technique to compute the one-loop effective potential with the nontrivial Polyakov loop phase and with the nontrivial Wilson line phase along the extra dimension. Effective potentials as functions of two gauge-field condensations are shown for several simple matter contents, including fundamental, sextet, and adjoint representational Dirac fermions. Possible extensions and applications of our form…
With minimal field content and for an interesting range of the supersymmetric Higgs mixing parameter, 0.5 < tan^2 β< 2, the superpartner mass scale, \tilde{m}, is found to be at the intermediate scale, ~ 10^{10 \pm 1} GeV, near where the Standard Model Higgs quartic coupling passes through zero. For any 4d supersymmetric grand unified symmetry spontaneously broken by a vacuum expectation value <Σ>, if superpotential interactions for Σare forbidden e.g. by R symmetries, the uneaten color octet, Σ_8, and weak triplet, Σ_3, have masses of order \tilde{m}. The combination of superpartner and Σ_{8,…
It was shown recently that the original SU(5) theory of Georgi and Glashow, augmented with an adjoint fermionic multiplet 24_F, can be made compatible both with neutrino masses and gauge coupling unification. In particular, the model predicts that either electroweak-triplet states are light, within the reach of the Large Hadron Collider (LHC), or proton decay will become accessible at the next generation of megaton-scale facilities. In this paper, we present the computation of the correlation function between the electroweak-triplet masses and the unification scale at the next-to-next-to-leadi…
In the decomposition of $SO(10)$ grand unification to $SU(5) \times U(1)_χ$, two desirable features are obtained with the addition of one colored fermion octet $Ω$, one electroweak fermion triplet $Σ$ and one complex scalar triplet $S$ to the particle content of the standard model with two Higgs doublets. They are (1) gauge coupling unification of $SU(3)_C \times SU(2)_L \times U(1)_Y$ to $SU(5)$, and (2) the automatic (predestined) emergence of dark matter, i.e. $Ω$, $Σ$ and $S$, with dark parity given by $(-1)^{Q_χ+ 2j}$. It suggests that $U(1)_χ$ may well be the underlying symmetry of the d…
