arXiv subjects

Ilia Gogoladze

Publications and source records attributed to Ilia Gogoladze.

At least 73 records · Page 4Linked to original sources

arXiv2008

Higgs Mass Bounds, Type II SeeSaw and LHC

In type II seesaw utilized to explain the observed neutrino masses and mixings, one extends the Standard Model (SM) by introducing scalar fields which transform as a triplet under the electroweak gauge symmetry. New scalar couplings involving the Higgs doublet then appear and, as we show, these have important implications for the Higgs boson mass bounds obtained using vacuum stability and perturbativity arguments. We identify, in particular, regions of the parameter space which permit the SM Higgs boson to be as light as 114.4 GeV, the LEP2 bound. The triplet scalars include doubly charged particles whose masses could, in principle, be in the few hundred GeV range, and so they may be accessible at the LHC.

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arXiv2008

Higgs Boson Mass Bounds in the Standard Model with Type III and Type I Seesaw

In type III seesaw utilized to explain the observed solar and atmospheric neutrino oscillations the Standard Model (SM) particle spectrum is extended by introducing three SU(2)_L triplet fermion fields. This can have important implications for the SM Higgs boson mass (M_H) bounds based on vacuum stability and perturbativity arguments. We compute the appropriate renormalization group equations for type III seesaw, and then proceed to identify regions of the parameter space such that the SM Higgs boson mass window is enlarged to 125 GeV < M_H < 174 GeV, with the type III seesaw scale close to TeV. We also display regions of the parameter space for which the vacuum stability and perturbativity bounds merge together for large neutrino Yukawa couplings. Comparison with type I seesaw is also presented.

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arXiv2008

Interplay of Higgs and Sparticle Masses in the CMSSM with updated SUSY constraints

We estimate the bounds on Higgs and sparticle masses and discuss their correlations in the constrained minimal supersymmetric standard model (CMSSM). In our analysis we have applied the present constraints from collider and low energy experiments, as well as the experimental bound on cold dark matter from WMAP. For a given lightest Higgs boson mass, which is expected to be measured with good precision at the LHC, we find important correlations between the Higgs and sparticle masses which allows one to delineate the MSSM model parameters and particle spectra. We have also demonstrated an important complementarity between the LHC and direct dark matter detection experiments emphasizing that by including the experimental input both from collider physics and from dark matter detection experiments, one would significantly improve the measurement of the SUSY spectrum and the underlying parameter space.

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arXiv2007

Family Unification with SO(10)

Unification based on the group SO(10)^3 \times S_3 is studied. Each family has its own SO(10) group, and the S_3 permutes the three families and SO(10) factors. This is the maximal local symmetry for the known fermions. Family unification is achieved in the sense that all known fermions are in a single irreducible multiplet of the symmetry. The symmetry suppresses SUSY flavor changing effects by making all squarks and sleptons degenerate in the symmetry limit. Doublet-triplet splitting can arise simply, and non-trivial structure of the quark and lepton masses emerges from the gauge symmetry, including the "doubly lopsided" form.

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arXiv2007

Unparticle Physics And Gauge Coupling Unification

Unparticle physics from a hidden conformal sector can alter the evolution of the Standard Model (SM) gauge couplings via TeV scale threshold corrections. We discuss how this may lead to gauge coupling unification at M_{GUT}\approx 2 \times 10^{15} GeV -- 5 \times 10^{17} GeV without introducing new particles in the SM sector.

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arXiv2007

Higgs Boson Mass From Gauge-Higgs Unification

In certain five dimensional gauge theories the Standard Model Higgs doublet is identified, after compactification on the orbifold S^1/Z_2, with the zero mode of the fifth component of the gauge field. An effective potential for the Higgs field is generated via quantum corrections, triggered by the breaking of the underlying gauge symmetry through boundary conditions. The quartic Higgs coupling can be estimated at low energies by employing the boundary condition that it vanishes at the compactification scale Λ, as required by five dimensional gauge invariance. For Λ\gtrsim 10^{13}-10^{14} GeV, the Standard Model Higgs boson mass is found to be m_H = 125 \pm 4 GeV corresponding to a top quark pole mass M_t = 170.9 \pm 1.8 GeV. A more complete (gauge-Higgs-Yukawa) unification can be realized for Λ~ 10^8 GeV, which happens to be the scale at which the SU(2) weak coupling and the top quark Yukawa coupling have the same value. For this case, m_H = 117\pm 4 GeV.

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arXiv2007

Window For Higgs Boson Mass From Gauge-Higgs Unification

We consider six dimensional gauge models compactified on the orbifold T^2/Z_N (N=2,3,4,6) such that the Standard Model (SM) Higgs doublet arises from the extra-dimensional components of the gauge field. For Λ\leq 10^{19} GeV, where Λdenotes the compactification scale, we obtain 114.4 GeV \leq m_H \leq 164 GeV for the SM Higgs boson mass. We also consider gauge-Higgs-top and gauge-Higgs-bottom Yukawa unification which respectively yield m_H = 131^{+4}_{-5} GeV and m_H = 150^{+2}_{-2} GeV for a top quark pole mass M_t =170.9^{+1.8}_{-1.8} GeV. As a special case we recover the result m_H \leq 132 GeV previously obtained for five dimensional models.

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arXiv2007

Fermion Masses and Mixings in GUTs with Non-Canonical U(1)_Y

We discuss fermion masses and mixings in models derived from orbifold GUTs such that gauge coupling unification is achieved without low energy supersymmetry by utilizing a non-canonical U(1)_Y. A gauged U(1)_X flavor symmetry plays an essential role, and the Green-Schwarz mechanism is invoked in anomaly cancellations. Models containing vector-like particles with masses close to M_{GUT} are also discussed.

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arXiv2007

Yukawa Couplings in a Model with Gauge, Higgs and Matter Unification

We discuss how unification of the gauge, Higgs and (three chiral family) matter superfields can be realized from the compactification of a six dimensional supersymmetric SU(8) gauge theory over the orbifold R^4 x T^2/Z_3. The bulk gauge interaction includes Yukawa interactions to generate masses for quarks and leptons after the electroweak symmetry is broken. The Yukawa matrices in this case turn out to be antisymmetric, and thus not phenomenologically viable. To overcome this we introduce brane fields which are vector-like under the standard model gauge symmetry, and so do not alter the number of chiral families. In such a setup, the observed fermion masses and mixings can be realized by taking into account suppression effects from the effective Wilson line couplings and large volume of the extra dimensions.

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arXiv2006

Non-Canonical MSSM, Unification, And New Particles At The LHC

We consider non-canonical embeddings of the MSSM in high-dimensional orbifold GUTs based on the gauge symmetry SU(N), N=5,6,7,8. The hypercharge normalization factor k_Y can either have unique non-canonical values, such as 23/21 in a six-dimensional SU(7) model, or may lie in a (continuous) interval. Gauge coupling unification and gauge-Yukawa unification can be realized in these models by introducing new particles with masses in the TeV range which may be found at the LHC. In one such example there exist color singlet fractionally charged states.

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arXiv2006

Probing the Gravitational Scale via Running Gauge Couplings

According to a recent paper by Robinson and Wilczek, the leading gravitational corrections to the running of gauge couplings tend to reduce the values of the couplings at energies below the gravitational scale, defined to be the energy above which gravity becomes strongly interacting. If the physical gravitational scale is sufficiently low, as conjectured in certain extra-dimension models, this behavior of the gauge couplings can be measured in future high energy experiments, providing a way to determine where the gravitational scale lies. We estimate that measurements of the fine structure constant at the Large Hadron Collider and the proposed International Linear Collider energies can probe the gravitational scale up to several hundred TeV, which will be the most stringent test that can be obtained in the conceivable future.

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arXiv2006

Fermion Mass Generation in SO(10) with a Unified Higgs Sector

An analysis of generating fermion masses via cubic couplings in SO(10) grand unification with a unified Higgs sector is given. The new framework utilizes a single pair of vector--spinor representation $144+\bar{144}$ to break the gauge symmetry all the way to $SU(3)_C \times U(1)_{em}$. Typically the matter--Higgs couplings in this framework are quartic and lead to naturally suppressed Yukawa couplings for the first two generations. Here we show that much larger third generation couplings naturally arise at the cubic level with additional matter in 10--plet and 45--plet representations of SO(10). Thus the physical third generation is a mixture of 16, 10 and 45--plet representations while the remaining components become superheavy and are removed from the low energy spectrum. In this scenario it is possible to understand the heaviness of the top in a natural way since the analysis generates a hierarchy in the Yukawa couplings so that $h_{\textnormal {t}}/h_{\textnormal {b}}>> 1$ where $h_{\textnormal {t}} (h_{\textnormal {b}})$ are the top (bottom) Yukawa couplings. It is then possible to realize values of $\tanβ$ as low as 2, which also helps to stabilize the proton.

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arXiv2006

Higgs Boson Mass from Orbifold GUTs with Split Supersymmetry

We consider orbifold GUTs with N=1 supersymmetry in which the Standard Model (SM) gauge couplings are unified at M_GUT =~ 2 x 10^16 GeV with one of the third family (charged) Yukawa couplings. With split supersymmetry the SM Higgs mass is estimated to be 131 +/- 10 GeV for gauge-top quark Yukawa unification, which increases to 146 +/- 8 GeV for gauge-bottom quark (or gauge-tau lepton) Yukawa unification.

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arXiv2006

Precision electroweak constraints on Universal Extra Dimensions revisited

We reconsider the constraints on Universal Extra Dimensions (UED) models arising from precision electroweak data. We take into account the subleading contributions from new physics (expressed in terms of the X,Y ... variables), as well as two loop corrections to the Standard Model rho parameter. For the case of one extra dimension, we obtain a lower bound on the inverse compactification scale M = R^{-1} of 600 GeV (at 90% confidence level), with a Higgs mass of 115 GeV. However, in contradiction to recent claims, we find that this constraint is significantly relaxed with increasing Higgs mass, allowing for compactification scales as low as 300 GeV. LEP II data does not significantly affect these results.

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arXiv2006

Higgs Boson Mass From Orbifold GUTs

We consider a class of seven-dimensional N=1 supersymmetric orbifold GUTs in which the Standard Model (SM) gauge couplings and one of the Yukawa couplings (top quark, bottom quark or tau lepton) are unified, without low energy supersymmetry, at M_{GUT} \simeq 4 \times 10^{16} GeV. With gauge-top quark Yukawa coupling unification the SM Higgs boson mass is estimated to be 135 \pm 6 GeV, which increases to 144 \pm 4 GeV for gauge-bottom quark (or gauge-tau lepton) Yukawa coupling unification.

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arXiv2005

Orbifold Unification for the Gauge and Higgs Fields and Their Couplings

We present an orbifold GUT model in which the NMSSM Higgs trilinear couplings are unified with the three Standard Model gauge couplings. The model is constructed as an N=2 supersymmetric SU(8) gauge theory in six dimensions, which is reduced to the NMSSM with extra U(1) factors upon compactification. Such an unification is in good agreement with experiments. The predicted upper limit for the lightest CP-even neutral Higgs boson is somewhat larger than in the MSSM, and can be tested in the upcoming Large Hadron Collider.

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arXiv2005

A Unified Framework for Symmetry Breaking in SO(10)

A new SO(10) unified model is proposed based on a one step breaking of SO(10) to the Standard Model gauge group $SU(3)\times SU(2)\times U(1)_Y$ using a single 144 of Higgs. The symmetry breaking occurs when the SU(5) 24-plet component of 144 develops a vacuum expectation value. Further, it is possible to obtain from the same 144 a light Higgs doublet necessary for electro-weak symmetry breaking using recent ideas of string vacua landscapes and fine tuning. Thus the breaking of SO(10) down to $SU(3)_C\times U(1)_{em}$ can be accomplished with a single Higgs. We analyze this symmetry breaking pattern in the nonsupersymmetric as well as in the supersymmetric SO(10) model.In this scenario masses of the quarks and leptons arise via quartic couplings. We show that the resulting mass pattern is consistent with experimental data, including neutrino oscillations. The model represents an alternative to the currently popular grand unified scenarios.

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arXiv2005

Coupling Unifications in Gauge-Higgs Unified Orbifold Models

Supersymmetric gauge theories, in higher dimensions compactified in an orbifold, give a natural framework to unify the gauge bosons, Higgs fields and even the matter fields in a single multiplet of the unifying gauge symmetry. The extra dimensions and the supersymmetry are the two key ingredients for such an unification. In this work, we investigate various scenarios for the unification of the three gauge couplings, and the Yukawa couplings in the Minimal Supersymmetric Standard Model (MSSM), as well as the trilinear Higgs couplings λand κof the Non-Minimal Supersymmetric Standard Model (NMSSM). We present an SU(8) model in six dimensions with N=2 supersymmetry, compactified in a T^2/Z_6 orbifold which unifies the three gauge couplings with λand κof NMSSM. Then, we present an SU(9) model in 6D, which, in addition, includes partial unification of Yukawa couplings, either for the up-type (top quark and Dirac tau-neutrino) or down-type (bottom quark and tau lepton). We also study the phenomenological implications of these various unification scenarios using the appropriate renormalization group equations, and show that such unification works very well with the measured low energy values of the couplings. The predicted upper bounds for the lightest neutral Higgs boson mass in our model is higher than those in MSSM, but lower that those in the general NMSSM (where the couplings λand κare arbitrary). Some of the predictions of our models can be tested in the upcoming Large Hadron Collider.

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