It is well known that the supersymmetric finite threshold effects can induce substantial corrections to the Standard Model fermion masses. This opens an alternative possibility to correct the problematic mass ratios of the lighter generations within the minimal SU(5) GUT. We show that with large soft A--terms, one can achieve simple unification for lighter generations without additional Higgs multiplet, while having sfermions lighter than 1 TeV. The presence of such large A--terms will distort the sfermion mass spectrum upon running from GUT scale down to the electroweak scale making it distinct from the universal SUSY breaking sector, especially in the first two generations. The implications of these splittings are studied in K and D meson oscillations and in rare processes D^+ -> pi^+ nu anti-nu and K^+ -> pi^+ nu anti-nu, and in the latter case the effect is found to be important.
Gauge-Yukawa Unification (GYU) yields a functional relation among the gauge and Yukawa couplings, and it may follow from the usual Grand Unification if it is supplemented with some additional principles. Postulating the principles of finiteness and reduction of couplings, we have achieved Gauge-Yukawa Unification in various supersymmetric unified models leading, among other things, to interesting predictions on the top quark mass.
We show that an intermediate gauge symmetry breaking scale can be a significant source of electric dipole moments for the electron and neutron in supersymmetric grand unified theories. New phases, similar to that of the CKM matrix, appear which do not arise from the supersymmetry (SUSY) breaking operators. To illustrate, we choose some grand unified SUSY models having an intermediate gauge symmetry breaking scale with some attractive features. We also show how well the $b-τ$ unification hypothesis works in this class of models.
After a short overview of the hypothesis of Yukawa unification within SUSY GUTs, I detail on the general conditions for its phenomenological viability, emphasizing the decisive role played by observables in the flavor sector.
We discuss the production of lepton flavor violation and EDMs and the viability of the $b-τ$ unification hypothesis in SUSY grand unification with an intermediate gauge symmetry breaking scale.
We study the deviation of yukawa coupling in the gauge-Higgs unification scenario from the Standard Model one. Taking into account the brane mass terms necessary for generating the flavor mixing and removing the exotic massless fermions, we derive an analytic formula determining the KK mass spectrum and yukawa coupling. Applying the obtained results to the tau and bottom yukawa couplings, we numerically calculate the ratio of the yukawa couplings in the gauge-Higgs unification and in the Standard Model.
Going beyond the theta function approximation we discuss supersymmetric unification of gauge couplings with exact decoupling of light and heavy particles at energy scales below their masses. We find that the Minimal SUSY model is strongly disfavored while the Missing Doublet Model survives with GUT scale masses rising into the $10^{18}$ GeV region.
We show that gauge couplings unify more precisely in the region of SUSY parameter space already preferred by Yukawa unification. While proton decay due to dimension 5 operators is maximally suppressed in this region, the contribution from dimension 6 operators is enhanced as a consequence of lower unification scale.
We explore the possibility of achieving one--step unification of the standard model coupling constants within non supersymmetric and supersymmetric gauge models, which at low energies have only the standard particle content. The constraints are the experimental values of $α_{em}$, $α_s$ and $\sin^2θ_W$ at $10^2 GeV$, and the lower bounds for FCNC and proton decay rates. The analysis is done in a model independent way.
In this talk we assume SO(10) boundary conditions at the GUT scale, including unification for the third generation Yukawa couplings $λ_t = λ_b = λ_τ$. We find that this assumption is only consistent with the low energy data in a narrow region of soft SUSY breaking parameter space. We discuss the consequences of this result for Higgs and SUSY searches.
In supersymmetric theories with extra dimensions, the Higgs and matter fields can be part of the gauge multiplet, so that the Yukawa interactions can arise from the gauge interactions. This leads to the possibility of gauge-Yukawa coupling unification, g_i=y_f, in the effective four dimensional theory after the initial gauge symmetry and the supersymmetry are broken upon orbifold compactification. We consider gauge-Yukawa unified models based on a variety of four dimensional symmetries, including SO(10), SU(5), Pati-Salam symmetry, trinification, and the Standard Model. Only in the case of Pat…
We systematically analyze the correlations between the various leptonic and hadronic flavor violating processes arising in SUSY Grand Unified Theories. Using the GUT-symmetric relations between the soft SUSY breaking parameters, we assess the impact of hadronic and leptonic flavor observables on the SUSY sources of flavor violation.
Talk given at PASCOS 2012, Merida, Mexico describing work in progress in collaboration with Archana Anandakrishnan, Christopher Plumberg and Akin Wingerter.
We study the effects of additional fields on the unification of gauge couplings in supersymmetric models. We find that the effects are quite constrained by the requirement of SU(5) gauge invariance. In general, we find that any extension of the MSSM will form complete SU(5) multiplets or spoil gauge coupling unification.
We study the deviation of yukawa coupling in the gauge-Higgs unification scenario from the Standard Model one. Applying the obtained results to the tau and bottom yukawa couplings, we numerically calculate the signal strength of $gg \to H \to \bar b b, \bar τ τ$in the gauge-Higgs unification.
We discuss gauge and Yukawa unification in the context of a supersymmetric model with bilinear R-parity violation. We show that this model allows $b-τ$ Yukawa unification for any value of $\tanβ$ while satisfying perturbativity of the couplings. We also find the $t-b-τ$ Yukawa unification easier to achieve than in the MSSM, occurring in a wider high $\tanβ$ region. Finaly, we also discuss the compatibility between the predicted and the measured values for $α_s(M_Z)$
We propose a GUT model in which visible matter and messengers are treated in unified way what unavoidably leads to messenger-matter mixed Yukawa interactions. Influence of this mixing on the fermion masses and the weak mixing angles is discussed.
There is a convincing experimental evidence that neutrinos are massive. Therefore we investigate the influence of the neutrino masses on the unification of gauge and Yukawa couplings in the framework of the Minimal Supersymmetric Standard Model. We estimate the contribution of the neutrino Yukawa coupling to the gauge and Yukawa coupling unification. We find that in the case of the gauge coupling unification the effect of massive neutrinos is small and can be neglected. It appears to be much more significant, if we explore Y_{b} and Y_{tau} equality at the GUT scale. The neutrino contribution …
We show that a large CP asymmetry in hyperon decays can be naturally realized in the framework of SUSY models. The possibility is implemented by the hermiticities of Yukawa and A matrices. And also, the observed values of $ε$ and $ε'$ are explained.
The consequences of Gauge-Yukawa Unification (GYU) in supersymmetric unified models on low energy physics are analyzed. We find that the observed top-bottom mass hierarchy can be explained by supersymmetric GYU and different models can be experimentally distinguished if the top quark mass does not exceed the value $\sim 185$ GeV.
We study the influence of messenger Yukawa couplings and top, bottom and $τ$ Yukawa couplings on the proton lifetime in SU(5) Supersymmetric GUT with dynamical supersymmetry breaking mechanism due to Dine and Nelson.
Among the firm predictions of softly broken supersymmetry is the identity of gauge couplings and the corresponding Yukawa couplings between gauginos, sfermions and fermions. In the event that a SUSY-like spectrum of new particles is discovered at future colliders, a key follow-up will be to test these relations experimentally. In detailed studies it has been found that the SUSY-Yukawa couplings of the electroweak sector can be studied with great precision at the ILC, but a similar analysis for the Yukawa coupling of the SUSY-QCD sector is far more challenging. Here a first phenomenological stu…
We discuss the basic idea of the Gauge-Yukawa Unification that is based on the principle of the reduction of couplings. This method of unification relies on the search of successful renormalization group invariant relations among couplings, which do not originate from symmetry principles. The predictive power of Grand Unified Theories can be increased by this method, predicting for instance values of the top quark mass consistent with the recent experimental data. The hope is that this unification attempt might shed further light on the origin of the Yukawa sector of the standard model.
In this talk I discuss the problems and virtues of SUSY GUTs in four dimensions. I then show how to solve some of these problems, without foregoing the virtues, by considering an SO(10) SUSY GUT in five dimensions. I discuss gauge coupling unification and neutrino masses. In particular, it is shown that the 5D compactification scale and cutoff scale are determined by fitting the low energy values of the three standard model gauge couplings. Neutrino masses can be accommodated.
We study effects of SUSY particle decouplings on a quasi fixed point (QFP) of Yukawa coupling. From renormalization group analysis it is shown that if the SUSY breaking scale $M_S$ is large ($\simg 1$TeV), effects of decoupling of Higgsinos and squarks raise the top Yukawa QFP. This tendency is enhanced in most cases of non-universal SUSY breaking. For the case of $M_S\siml 1$TeV, the decoupling of gluinos lowers $m_t^{\rm QFP}$. We checked some parameter dependencies for the top Yukawa QFP. The bottom-top Yukawa unified case is also studied. When top quark mass is measured more precisely, som…
Recently it has been proposed that, in the framework of quantum field theory, both the Standard Model gauge and Yukawa interactions arise from a single gauge interaction in higher dimensions with supersymmetry. This leads to the unification of the Standard Model gauge couplings and the third family Yukawa couplings at the GUT scale. In this work, we make a detailed study of this unification using the current experimental data, and find a good agreement in a significant region of the parameter space. Similar relations, required in Finite Grand Unification models, are also studied.
For strong enough Yukawa coupling the electroweak standard model fermion finds it energetically advantageous to transform itself into a bound state in the hedgehog background of Higgs field in semiclassical approximation. By considering the bound states give the masses for lepton and quark, we found that all the strongly Yukawa coupling constants tend to an unitary constant. On the other hand, the masses of $W$ and $Z$ produced by the hedgehog Higgs field keep almost no change.
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 $\tanβ$ value, e.g., $\sim$ 30, which corresponds to much smaller threshold corrections compared to usu…
An analysis is made on bottom-tau Yukawa unification in supersymmetric (SUSY) SU(5) grand unified theory (GUT) in the framework of minimal supergravity, in which the parameter space is restricted by some experimental constraints including Br(b to s gamma) and muon g-2. The bottom-tau unification can be accommodated to the measured branching ratio Br(b to s gamma) if superparticle masses are relatively heavy and higgsino mass parameter μis negative. On the other hand, if we take the latest muon g-2 data to require positive SUSY contributions, then wrong-sign threshold corrections at SUSY scale …
We use $t, b, τ$ Yukawa unification to constrain SUSY parameter space. We find a narrow region survives for $μ> 0$ (suggested by \bsgam and the anomalous magnetic moment of the muon) with $A_0 \sim - 1.9 m_{16}$, $m_{10} \sim 1.4 m_{16}$, $m_{16} \sim 1200 -3000$ \gev and $μ, M_{1/2} \sim 100 - 500$ \gev. Demanding Yukawa unification thus makes definite predictions for Higgs and sparticle masses.
In a supersymmetric model where R-Parity and lepton number are violated bilinearly in the superpotential, which can explain the solar and atmospheric neutrino problems, we study the unification of gauge and Yukawa couplings at the GUT scale. We show that bottom-tau Yukawa coupling unification can be achieved at any value of $\tanβ$, and that the strong coupling constant prediction from unification of gauge couplings is closer to the experimental value compared with the MSSM. We also study the predictions for $V_{cb}$ in a Yukawa texture ansätze.
Gauge-Yukawa Unification (GYU) is a renormalization group invariant functional relation among gauge and Yukawa couplings which holds beyond the unification point in Grand Unified Theories (GUTs). We present here various models where GYU is obtained by requiring the principles of finiteness and reduction of couplings. We examine the consequences of these requirements for the low energy parameters, especially for the top quark mass. The predictions are such that they clearly distinguish already GYU from ordinary GUTs. It is expected that it will be possible to discriminate among the various GYUs…
We report on a preferred region of supersymmetric parameter space by t, b, tau Yukawa unification. We find a narrow region survives for mu > 0 (suggested by b --> s gamma and the anomalous magnetic moment of the muon) with A_0 \sim - 2 m_{16}, m_{16} > 1200 GeV, mu, M_{1/2} << m_{16} and tan β\sim 50 \pm 2. Demanding Yukawa unification thus makes definite predictions for Higgs and sparticle masses.
The apparent unification of gauge couplings around 10^16 GeV is one of the strong arguments in favor of Supersymmetric extensions of the Standard Model (SM). In this contribution two new analyses of the gauge coupling running, the latter using in contrast to previous studies not data at the Z peak but at LEP2 energies, are presented. The generic SUSY scale in the more precise novel approach is 93 < M_SUSY < 183 GeV, easily within LHC, and possibly even within Tevatron reach.
The idea of Gauge-Yukawa Unification (GYU) based on the principle of reduction of couplings is elucidated. We show how the observed top-bottom mass hierarchy can be explained in terms of supersymmetric GYU by considering an example of the minimal supersymmetric GUT.
The scaling behavior and fixed points in the evolution of fermion Yukawa couplings and mixing angles are discussed. The relevance of fixed points in determining the top quark mass is described.
Gauge-Yukawa Unification (GYU) is a renormalization group invariant functional relation among gauge and Yukawa couplings which holds beyond the unification point in Grand Unified Theories (GUTs). Here, GYU is obtained by requiring finiteness and reduction of couplings to all orders in perturbation theory. We examine the consequences of GYU in various supersymmetric GUTs and in particular the predictions for the top quark mass. These predictions are such that they distinguish already GYU from ordinary GUTs. Moreover, when more accurate measurements of the top quark mass are available, it is exp…
We revisit the WMAP dark matter constraints on Yukawa Unification in the presence of massive neutrinos. The large lepton mixing indicated by the data may modify the predictions for the bottom quark mass, enabling Yukawa unification also for large $\tanβ$, and for positive $μ$ that was previously disfavoured. As a result, the allowed parameter space for neutralino dark matter increases for positive $μ$, particularly for areas with resonant enhancement of the neutralino relic density. On the contrary, a negative $μ$ is not easily compatible with large lepton mixing and Dirac neutrino Yukawa coup…
We revisit the implications of naturalness and gauge unification in the MSSM. We find that precision unification of the couplings in connection with a small mu parameter requires a highly compressed gaugino pattern as it is realized in mirage mediation. Due to the small mass difference between gluino and LSP, collider limits on the gluino mass are drastically relaxed. Without further assumptions, the relic density of the LSP is very close to the observed dark matter density due to coannihilation effects.
In order to establish supersymmetry (SUSY) at future colliders, the identity of gauge couplings and the corresponding Yukawa couplings between gauginos, sfermions and fermions needs to be verified. Here a first phenomenological study for determining the Yukawa coupling of the SUSY-QCD sector is presented, using a method which combines information from LHC and ILC.
In this paper we analyze Yukawa unification in a three family SO(10) SUSY GUT. We perform a global $χ^2$ analysis and show that SUSY effects do not decouple even though the universal scalar mass parameter at the GUT scale, $m_{16}$, is found to lie between 15 and 30 TeV with the best fit given for $m_{16} \approx 25$ TeV. Note, SUSY effects don't decouple since stops and bottoms have mass of order 5 TeV, due to RG running from $M_{GUT}$. The model has many testable predictions. Gauginos are the lightest sparticles and the light Higgs boson is very much Standard Model-like. The model is consist…
We explore in a model independent way the possibility of achieving the non supersymmetric gauge coupling unification within left-right symmetric models, with the minimal particle content at the left-right mass scale which could be as low as 1 TeV in a variety of models, and with a unification scale M in the range $10^5$ GeV $< M< 10^{17.7}$ GeV.
We consider the production, at future lepton colliders, of final fermion, sfermion, scalar pairs in SUSY models. For third family fermions and sfermions and for charged Higgses, the leading Yukawa effect at one loop for large c.m. energies comes from a linear logarithm of Sudakov type, that only depends, in the MSSM, on one SUSY mass scale and on tan(beta). Assuming a relatively light SUSY scenario, we illustrate a possible determination of tan(beta) at c.m. energies of about 1 TeV, working systematically at subleading logarithmic accuracy, at the one-loop level.
Third family Yukawa unification, as suggested by minimal SO(10) unification, is revisited in light of recent experimental measurements and theoretical progress. We characterize unification in a semi-model-independent fashion, and conclude that finite $b$ quark mass corrections from superpartners must be nonzero, but much smaller than naively would be expected. We show that a solution that does not require cancellations of dangerously large tanbeta effects in observables implies that scalar superpartner masses should be substantially heavier than the Z scale, and perhaps inaccessible to all cur…
Supersymmetry predicts the identity of Yukawa and gauge couplings in the QCD sector: quark-squark-gluino = squark-squark-gluon = quark-quark-gluon. We examine whether the quark-squark-gluino Yukawa coupling can be determined, by methods complementary to LHC, by analyzing squark-gluino final states at a TeV e+e- collider.
The wave functions and Yukawa couplings of the top and bottom quarks in the SO(5) x U(1) gauge-Higgs unification model are determined. The result is summarized in the effective interactions for \hat θ_H(x) = θ_H + H(x)/f_H where θ_H is the Wilson line phase and H(x) is the 4D Higgs field. The Yukawa, WWH and ZZH couplings vanish at θ_H = \onehalf π. There emerges the possibility that the Higgs particle becomes stable.
Matter-Higgs unification in string-inspired supersymmetric Grand Unified Theories predicts the existence of colored states in the Higgs multiplets and calls for two extra generations of Higgs-like fields ('unhiggses'). If these states are present near the TeV scale, gauge-coupling unification points to the existence of two distinct scales, 10^15 GeV where right-handed neutrinos and a Pati-Salam symmetry appear, and 10^18 GeV where complete unification is achieved. Baryon-number conservation, while not guaranteed, can naturally emerge from an underlying flavor symmetry. Collider signatures and …
We present simple analytical formulae which describe solutions of the RG equations for Yukawa couplings in SUSY gauge theories with the accuracy of a few per cent. Performing the Grassmannian expansion in these solutions one finds those for all the soft couplings and masses. The solutions clearly exhibit the fixed point behaviour which can be calculated analytically. A comparison with numerical solutions is demonstrated.
We present a new constraint on a lepton mixing matrix $V$ from lepton-flavor violating (LFV) processes in supersymmetric standard models with massive neutrinos. Here, we assume Yukawa-coupling unification $f_{ν3}\simeq f_{\rm top}$, in which $τ$-neutrino Yukawa coupling $f_{ν3}$ is unified into top-quark Yukawa coupling $f_{\rm top}$ at the unification scale $M_*\simeq 3\times 10^{16}$ GeV. We show that the present experimental bound on $μ\to e γ$ decay already gives a stringent limit on the lepton mixing (typically $V_{13}<0.02$ for $V_{23}=1/\sqrt{2}$). Therefore, many existing neutrino-mass…
Supersymmetric Grand Unification usually provides unification of the bottom quark and the tau lepton Yukawa couplings at the GUT scale. In the CMSSM this can be realised only for a very particular choice of parameters. In this letter we study the GUT scale ratio y_tau/y_b for less peculiar parameters in the large tan beta regime and identify one parameter region preferred by current experimental data. In this region, which is well within the reach of the LHC, the ratio is very close to the recently proposed value of 3/2.
We show how an intermediate gauge symmetry breaking scale can be a source of lepton flavor violation and EDM of electron and neutron in SUSY GUTs. The Universal soft supersymmetry breaking operators can be introduced at the GUT scale or above.
We describe in detail our calculation of the full supersymmetric (SUSY) QCD corrections to neutralino annihilation into heavy quarks and extend our numerical analysis of the resulting dark matter relic density to scenarios without scalar or gaugino mass unification. In these scenarios, the final state is often composed of top quarks and the annihilation proceeds through Z^0-boson or scalar top-quark exchanges. The impact of the corrections is again shown to be sizable, so that they must be taken into account systematically in global analyses of the supersymmetry parameter space.
We consider the constrained minimal supersymmetric standard model which emerges from one theory with a small deviation from Yukawa unification which is adequate for $μ>0$. We show that this model possesses a wide and natural range of parameters which is consistent with the data on $b\to sγ$, the muon anomalous magnetic moment, the cold dark matter abundance in the universe, and the Higgs boson masses.
We revisit the WMAP dark matter constraints on Yukawa Unification in the presence of massive neutrinos. The large neutrino mixing indicated by the data modifies the predictions for the bottom quark mass, and enables Yukawa also for large $\tanβ$, and for positive $μ$ that were previously disfavoured. As a result, the allowed parameter space for neutralino dark matter also increases, particularly for areas with resonant enhancement of the neutralino relic density.
We study Yukawa unification, including the effects of a physical neutrino mass consistent with the Superkamiokande observations, in a string/$D$-brane inspired Pati-Salam model which allows the most general non-universal scalar and gaugino masses, including the usual $D$-term contributions which arise in SO(10). We investigate how the tight constraints from rare decays such as $b \to s γ$ and $τ\to μγ$ can provide information about the family dependent supersymmetry breaking soft Lagrangian, for example the trilinears associated with the second and third family. Many of our results also apply …
In the $SO(5) \times U(1)$ gauge-Higgs unification in the Randall-Sundrum (RS) warped space the Higgs boson naturally becomes stable. The model is consistent with the current collider signatures only for a large warp factor $z_L > 10^{15}$ of the RS space. In order for stable Higgs bosons to explain the dark matter of the Universe the Higgs boson must have a mass $m_h = 70 \sim 75$ GeV, which can be obtained in the non-SUSY model with $z_L \sim 10^5$. We show that this discrepancy is resolved in supersymmetric gauge-Higgs unification where a stop mass is about $300 \sim 320 $GeV and gauginos i…
The WMAP dark matter constraints on b-$τ$ Yukawa Unification in the presence of massive neutrinos is revisited. The predictions for the bottom quark mass are observed to be modified by the large neutrino mixing suggested by the data. This enables Yukawa unification also for large $\tanβ$, and for positive $μ$ that were previously disfavoured. Consequently, the allowed parameter space for neutralino dark matter differs from the MSSM one. We also find that the parameter space being compatible with dark matter also predicts detectable rates for Lepton Flavour Violation at the LHC.
We discuss the Yukawa couplings in 6D gauge-Higgs unification models on $T^2/Z_N$ in the presence of magnetic fluxes. We provide general formulae for them, and numerically evaluate their magnitude in a specific model on $T^2/Z_3$. Thanks to the nontrivial profiles of the zero-mode wave functions, the top quark Yukawa coupling can be reproduced without introducing a large representation of the gauge group for matter fields. However, it is difficult to realize small Yukawa couplings only by the magnetic fluxes and the Wilson-line phases because of the complicated structure of the mode functions …
We study supersymmetric unified models with three fermion generations based on the gauge group $SO(10)$ and require Gauge-Yukawa Unification, i.e., a renormalization group invariant functional relationship among the gauge and Yukawa couplings of the third generation in the symmetric phase. In the case of the minimal model, we find that the predicted values for the top and bottom quark masses are in agreement with the present experimental data for a wide range of supersymmetry breaking scales. We also find that an experimental accuracy of less than $1 \%$ for the top quark mass could test the c…
We study gauge coupling unification and various phenomenological issues, such as baryon number conservation, the $μ$ problem and neutrino anomalies, within SUSY 5D orbifold models. The 5D MSSM on an $S^{(1)}/Z_2$ orbifold with 'minimal' field content does not lead to low scale unification, while some of its extensions can give unification near the multi TeV scale. Within the orbifold SU(5) GUT, low scale unification can not be realized due to full SU(5) multiplets participating in the renormalization above the compactification scale. As alternative examples, we construct 5D N=1 SUSY Pati-Salam…
