Radiative Electroweak Symmetry Breaking Research Articles

A quirky little Higgs model

We consider an extra dimensional model where the quadratically divergent top loop contribution to the Higgs mass is cancelled by an uncolored heavy "top quirk" charged under a different SU(3) gauge group. The cancellation is enforced by bulk gauge symmetries. Thus we have an unusual type of little Higgs model which has some quirky signatures. The top partner in this model could be identified at the Large Hadron Collider due to macroscopic strings that connect quirk and anti-quirks. The model can undergo radiative electroweak symmetry breaking and is consistent with precision electroweak measurements.

Higgs funnel region of supersymmetric dark matter for smalltanβand renormalization group effects on pseudoscalar Higgs boson with scalar mass nonuniversality

A non-universal scalar mass supergravity type of model is explored where the first two generation of scalars and the third generation of sleptons may be very massive. Lighter or vanishing third generation of squarks as well as Higgs scalars at the unification scale cause the radiative electroweak symmetry breaking constraint to be less prohibitive. Thus, both FCNC/CP-violation problems as well as the naturalness problem are within control. We identify a large slepton mass effect in the RGE of $m_{H_D}^2$ (for the down type of Higgs) that may turn the later negative at the electroweak scale even for a small $\tan\beta$. A hyperbolic branch/focus point like effect is found for $m_A^2$ that may result in very light Higgs spectra. The lightest stable particle is dominantly a bino that pair annihilates via Higgs exchange, giving rise to a WMAP satisfied relic density region for all $\tan\beta$. Detection prospects of such LSPs in the upcoming dark matter experiments both of direct and indirect types (photon flux) are interesting. The Higgs bosons and the third generation of squarks are light in this scenario and these may be easily probed besides charginos and neutralinos in the early runs of LHC.

Modulus-dominated SUSY-breaking soft terms in F-theory and their test at LHC

We study the general patterns of SUSY-breaking soft terms arising under the assumption of Kahler moduli dominated SUSY-breaking in string theory models. Insisting that all MSSM gauginos get masses at leading order and that the top Yukawa coupling is of order the gauge coupling constant identifies the class of viable models. These are models in which the SM fields live either in the bulk or at the intersection of local sets of Type IIB D7-branes or their F-theory relatives. General arguments allow us to compute the dependence of the Kahler metrics of MSSM fields on the local Kahler modulus of the brane configuration in the large moduli approximation. We illustrate this study in the case of toroidal/orbifold orientifolds but discuss how the findings generalize to the F-theory case which is more naturally compatible with coupling unification. Only three types of 7-brane configurations are possible, leading each of them to very constrained patterns of soft terms for the MSSM. We study their consistency with radiative electroweak symmetry breaking and other phenomenological constraints. We find that essentially only the configuration corresponding to intersecting 7-branes is compatible with all present experimental constraints and the desired abundance of neutralino dark matter. The obtained MSSM spectrum is very characteristic and could be tested at LHC. We also study the LHC reach for the discovery of this type of SUSY particle spectra.

Radiative [formula omitted] symmetry breaking and the [formula omitted] mediated SUSY breaking

We explore a mechanism of radiative B–L symmetry breaking in analogous to the radiative electroweak symmetry breaking. The breaking scale of B–L symmetry is related to the neutrino masses through the see-saw mechanism. Once we incorporate the U(1)B–L gauge symmetry in SUSY models, the U(1)B–L gaugino, Z˜B–L appears, and it can mediate the SUSY breaking (Z-prime mediated SUSY breaking) at around the scale of 106 GeV. Then we find a links between the neutrino mass (more precisely the see-saw or B–L scale of order 106 GeV) and the Z-prime mediated SUSY breaking scale. It is also very interesting that the gluino at the weak scale becomes relatively light, and almost compressed mass spectra for the gaugino sector can be realized in this scenario, which is very interesting in scope of the LHC.

Sparticles at the LHC

Sparticle mass hierarchies will play an important role in the type of signatures that will be visible at the Large Hadron Collider. We analyze these hierarchies for the four lightest sparticles for a general class of supergravity unified models including nonuniversalities in the soft breaking sector. It is shown that out of nearly $10^4$ possibilities of sparticle mass hierarchies, only a small number survives the rigorous constraints of radiative electroweak symmetry breaking, relic density and other experimental constraints. The signature space of these mass patterns at the Large Hadron Collider is investigated using a large set of final states including multi-leptonic states, hadronically decaying $\tau$s, tagged $b$ jets and other hadronic jets. In all, we analyze more than 40 such lepton plus jet and missing energy signatures along with several kinematical signatures such as missing transverse momentum, effective mass, and invariant mass distributions of final state observables. It is shown that a composite analysis can produce significant discrimination among sparticle mass patterns allowing for a possible identification of the source of soft breaking. While the analysis given is for supergravity models, the techniques based on mass pattern analysis are applicable to wide class of models including string and brane models.

Collider phenomenology of Gauge-Higgs unification scenarios in warped extra dimensions

We compute the couplings of the zero modes and first excited states of gluons, $W$'s, $Z$ gauge bosons, as well as the Higgs, to the zero modes and first excited states of the third generation quarks, in a Randall-Sundrum Gauge-Higgs unification scenario based on a bulk $SO(5)\ifmmode\times\else\texttimes\fi{}U(1{)}_{X}$ gauge symmetry, with gauge and fermion fields propagating in the bulk. Using the parameter space consistent with electroweak precision tests and radiative electroweak symmetry breaking, we study numerically the dependence of these couplings on the parameters of our model. Furthermore, after emphasizing the presence of light excited states of the top quark, which couple strongly to the Kaluza-Klein gauge bosons, the associated collider phenomenology is analyzed. In particular, we concentrate on the possible detection of the first excited state of the top, ${t}^{1}$, which tends to have a higher mass than the ones accessible via regular QCD production processes. We stress that the detection of these particles is still possible due to an increase in the pair production of ${t}^{1}$ induced by the first excited state of the gluon, ${G}^{1}$.

Gauge-Higgs unification and radiative electroweak symmetry breaking in warped extra dimensions

of large corrections to the T parameter and the coupling of the Z to the bottom quark. We demonstrate that electroweak symmetry breaking may be realized, with proper generation of the top and bottom quark masses for the same region of bulk mass parameters that lead to good agreement with precision electroweak data in the presence of a light Higgs. We compute the Higgs mass and demonstrate that for the range of parameters for which the Higgs boson has Standard Model-like properties, the Higgs mass is naturally in a range that varies between values close to the LEP experimental limit and about 160 GeV. This mass range may be probed at the Tevatron and at the LHC. We analyze the KK spectrum and briey discuss the phenomenology of the light resonances arising in our model.

Supersymmetric Higgs and radiative electroweak breaking

We review the mechanism of radiative electroweak symmetry breaking taking place in SUSY versions of the Standard Model. We further discuss different proposals for the origin of SUSY-breaking and the corresponding induced SUSY-breaking soft terms. Several proposals for the understanding of the little hierarchy problem are critically discussed. To cite this article: L.E. Ibáñez, G.G. Ross, C. R. Physique 8 (2007).

SuSpect: A Fortran code for the Supersymmetric and Higgs particle spectrum in the MSSM

We present the Fortran code SuSpect version 2.3, which calculates the Supersymmetric and Higgs particle spectrum in the Minimal Supersymmetric Standard Model (MSSM). The calculation can be performed in constrained models with universal boundary conditions at high scales such as the gravity (mSUGRA), anomaly (AMSB) or gauge (GMSB) mediated supersymmetry breaking models, but also in the non-universal MSSM case with R-parity and CP conservation. Care has been taken to treat important features such as the renormalization group evolution of parameters between low and high energy scales, the consistent implementation of radiative electroweak symmetry breaking and the calculation of the physical masses of the Higgs bosons and supersymmetric particles taking into account the dominant radiative corrections. Some checks of important theoretical and experimental features, such as the absence of non-desired minima, large fine-tuning in the electroweak symmetry breaking condition, as well as agreement with precision measurements can be performed. The program is simple to use, self-contained and can easily be linked to other codes; it is rather fast and flexible, thus allowing scans of the parameter space with several possible options and choices for model assumptions and approximations. Program summary Title of program:SuSpect Catalogue identifier:ADYR_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADYR_v1_0 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions:none Programming language used:FORTRAN 77 Computer:Unix machines, PC No. of lines in distributed program, including test data, etc.:21 821 No. of bytes in distributed program, including test data, etc.:249 657 Distribution format:tar.gz Operating system:Unix (or Linux) RAM:approximately 2500 Kbytes Number of processors used:1 processor Nature of problem: SuSpect calculates the supersymmetric and Higgs particle spectrum (masses and some other relevant parameters) in the unconstrained Minimal Supersymmetric Standard Model (MSSM), as well as in constrained models (cMSSMs) such as the minimal Supergravity (mSUGRA), the gauge mediated (GMSB) and anomaly mediated (AMSB) Supersymmetry breaking scenarii. The following features and ingredients are included: renormalization group evolution between low and high energy scales, consistent implementation of radiative electroweak symmetry breaking, calculation of the physical particle masses with radiative corrections at the one- and two-loop level. Solution method:The main methods used in the code are: (1) an (adaptative fourth-order) Runge–Kutta type algorithm (following a standard algorithm described in “Numerical Recipes”), used to solve numerically a set of coupled differential equations resulting from the renormalization group equations at the two-loop level of the perturbative expansions; (2) diagonalizations of mass matrices; (3) some mathematical (Spence, etc) functions resulting from the evaluation of one and two-loop integrals using the Feynman graphs techniques for radiative corrections to the particle masses; (4) finally, some fixed-point iterative algorithms to solve non-linear equations for some of the relevant output parameters. Restrictions:(1) The code is limited at the moment to real input parameters. (2) It also does not include flavor non-diagonal terms which are possible in the most general soft supersymmetry breaking Lagrangian. (3) There are some (mild) limitations on the possible range of values of input parameter, i.e. not any arbitrary values of some input parameters are allowed: these limitations are essentially based on physical rather than algorithmic issues, and warning flags and other protections are installed to avoid as much as possible execution failure if unappropriate input values are used. Running time:between 1 and 3 seconds depending on options, with a 1 GHz processor.

Neutrino-induced electroweak symmetry breaking in supersymmetric SO(10) models

The radiative electroweak symmetry breaking, the unification of third-generation Yukawa couplings, and flavor-changing rare decay are investigated in two types of supersymmetric SO(10) scenarios taking into account of the effects of neutrino physics, i.e. the observed large generation mixing and tiny mass scale. The first scenario is minimal, including right-handed neutrinos at intermediate scale with the unification of third-generation Yukawa couplings. Another is the case that the large mixing of atmospheric neutrinos originates from the charged-lepton sector. Under the SO(10)-motivated boundary conditions for supersymmetry-breaking parameters, typical low-energy particle spectrum is discussed and the parameter space is identified which satisfies the conditions for successful radiative electroweak symmetry breaking and the experimental mass bounds of superparticles. In particular, the predictions of the bottom quark mass and the b \to s gamma branching ratio are fully analyzed. In both two scenarios, new types of radiative electroweak symmetry breaking are achieved with the effects of neutrino couplings. The Yukawa unification becomes compatible with the bottom quark mass and the experimental constraints from flavor-violating rare processes, and the hierarchical superparticle mass spectrum is obtained.

Radiative breaking scenario for the GUT gauge symmetry

The origin of the GUT scale from the top down perspective is explored. The GUT gauge symmetry is broken by the renormalization group effects, which is an extension of the radiative electroweak symmetry breaking scenario to the GUT models. That is, in the same way as the origin of the electroweak scale, the GUT scale is generated from the Planck scale through the radiative corrections to the soft SUSY breaking mass parameters. This mechanism is applied to a perturbative SO(10) GUT model, recently proposed by us. In the SO(10) model, the relation between the GUT scale and the Planck scale can naturally be realized by using order one coupling constants.

Fully radiative electroweak symmetry breaking

Models of Gauge-Higgs unification in extra dimensions offer a very elegant playground where one can study electroweak symmetry breaking. The nicest feature is that gauge symmetry itself protects the Higgs potential from divergences, thus potentially curing the hierarchy problem in the Standard Model. In a flat space model tree-level contributions to electroweak precision observables will be absent due to the flatness of the gauge and Higgs wave functions. The Higgs potential is fully radiatively generated and the contribution of bulk fermions will induce a vacuum expectation value. A generic problem is that the quartic scalar coupling is too low, resulting in a Higgs VEV that is too close to the compactification scale, and a Higgs mass that is too light. In this paper we show that it is possible to solve these problems in a minimal scenario by cancellations in the Higgs potential between the contribution of different bulk fermions. A crucial role is played by antiperiodic fermions: the cancellation is not the result of a fine tuning, but rather dictated by the choice of representations and parities of the fermions. We also show that introducing a relatively large representation can help in achieving a sufficiently heavy top. In this case, the strong coupling scale is lowered to a marginally acceptable value, and a more careful analysis of two loop effects should decide if the theory remains under perturbative control.

Stability of subsequent-to-leading-logarithm corrections to the effective potential for radiative electroweak symmetry breaking

We demonstrate the stability under subsequent-to-leading logarithm corrections of the quartic scalar-field coupling constant λ and the running Higgs boson mass obtained from the (initially massless) effective potential for radiatively broken electroweak symmetry in the single-Higgs-doublet Standard Model. Such subsequent-to-leading logarithm contributions are systematically extracted from the renormalization group equation considered beyond one-loop order. We show λ to be the dominant coupling constant of the effective potential for the radiatively broken case of electroweak symmetry. We demonstrate the stability of λ and the running Higgs boson mass through five orders of successively subleading logarithmic corrections to the scalar-field-theory projection of the effective potential for which all coupling constants except the dominant coupling constant λ are disregarded. We present a full next-to-leading logarithm potential in the three dominant Standard Model coupling constants ( t-quark-Yukawa, α s , and λ) from these coupling constants' contribution to two loop β- and γ-functions. Finally, we demonstrate the manifest order-by-order stability of the physical Higgs boson mass in the 220 – 231 GeV range. In particular, we obtain a 231 GeV physical Higgs boson mass inclusive of the t-quark-Yukawa and α s coupling constants to next-to-leading logarithm order, and inclusive of the smaller SU ( 2 ) × U ( 1 ) gauge coupling constants to leading logarithm order.

Large evolution of the bilinear Higgs coupling parameter in supersymmetric models and reduction of phase sensitivity

The phases in a generic low-energy supersymmetric model are severely constrained by the experimental upper bounds on the electric dipole moments of the electron and the neutron. Coupled with the requirement of radiative electroweak symmetry breaking, this results in a large degree of fine tuning of the phase parameters at the unification scale. In supergravity type models, this corresponds to very highly tuned values for the phases of the bilinear Higgs coupling parameter $B$ and the universal trilinear coupling $A_0$. We identify a cancellation/enhancement mechanism associated with the renormalization group evolution of $B$, which, in turn, reduces such fine-tuning quite appreciably without taking recourse to very large masses for the supersymmetric partners. We find a significant amount of reduction of this fine-tuning in nonuniversal gaugino mass models that do not introduce any new phases.

STARTLING EQUIVALENCES IN THE HIGGS-GOLDSTONE SECTOR BETWEEN RADIATIVE AND LOWEST-ORDER CONVENTIONAL ELECTROWEAK SYMMETRY BREAKING

For the Higgs boson mass of ~ 220 GeV expected to arise from radiative electroweak symmetry breaking, we find the same lowest-order expressions as would be obtained from conventional electroweak symmetry breaking, given the same Higgs boson mass, for Higgs-Goldstone sector scattering processes identified with [Formula: see text], [Formula: see text], as well as for Higgs boson decay widths [Formula: see text], H → ZLZL. The radiatively broken case, however, leads to an order of magnitude enhancement over lowest-order conventional symmetry breaking for scattering processes [Formula: see text], ZLZL → HH, as well as a factor of ~ 30 enhancement for HH → HH.

Radiative electroweak symmetry breaking beyond leading logarithms

The top-quark Yukawa coupling is too large to permit radiative electroweak symmetry breaking to occur, to leading-logarithm order, for small values of y — the Higgs self-coupling. However, a large y solution leading to a viable Higgs mass of approximately 220 GeV does exist, and differs from conventional symmetry breaking by an approximately five-fold enhancement of the Higgs self-coupling. This scenario for radiative symmetry breaking is reviewed, and the order-by-order perturbative stability of this scenario is studied within the scalar-field theory projection of the Standard Model in which the Higgs self-coupling y represents the dominant Standard-Model coupling.PACS Nos.: 11.30.Qc, 11.10.Hi, 11.15.Tk, 12.15.Lk

Phenomenology of a Fluxed MSSM

We analyze the phenomenology of a set of minimal supersymmetric standard model (MSSM) soft terms inspired by flux-induced supersymmetry (SUSY)-breaking in Type IIB string orientifolds. The scheme is extremely constrained with essentially only two free mass parameters: a parameter M, which sets the scale of soft terms, and the mu parameter. After imposing consistent radiative electro-weak symmetry breaking (EWSB) the model depends upon one mass parameter (say, M). In spite of being so constrained one finds consistency with EWSB conditions. We demonstrate that those conditions have two solutions for mu<0, and none for mu>0. The parameter tan beta results as a prediction and is approximately 3-5 for one solution, and 25-40 for the other, depending upon M and the top mass. We examine further constraints on the model coming from b->s gamma, the muon g-2, Higgs mass limits and WMAP constraints on dark matter. The MSSM spectrum is predicted in terms of the single free parameter M. The low tan beta branch is consistent with a relatively light spectrum although it is compatible with standard cosmology only if the lightest neutralino is unstable. The high tan beta branch is compatible with all phenomenological constraints, but has quite a heavy spectrum. We argue that the fine-tuning associated to this heavy spectrum would be substantially ameliorated if an additional relationship mu=-2M were present in the underlying theory.

SOFT BREAKING IN SUSY, STRING AND INTERSECTING D BRANE MODELS

A brief review of recent developments on soft breaking in SUSY, string and intersecting D brane models is given. The constraints on soft breaking parameters from WMAP data are discussed. A discussion of the constraints of modular invariance on soft breaking within heterotic string models is given. It is shown that the radiative electroweak symmetry breaking leads to a more stringent constraint on soft parameters here than in SUGRA models. Finally, a brief review of recent developments on soft breaking in the framework of intersecting D brane models is given. The issue of gauge coupling unification within intersecting D brane models is briefly discussed.

μ problem in an extended gauge mediation supersymmetry breaking

We study the $\mu$ problem and the radiative electroweak symmetry breaking in an extended gauge mediation supersymmetry breaking (GMSB) model, in which the messenger fields are assumed to couple to the different singlet fields due to the discrete symmetry. Since the spectrum of superpartners is modified, the constraint from the $\mu$ problem can be relaxed in comparison with the ordinary GMSB at least from the viewpoint of radiative symmetry breaking. We study the consistency of the values of $\mu$ and $B_\mu$ with the radiative electroweak symmetry breaking and also the mass spectrum of superpartners. We present such a concrete example in a supersymmetric SU(5) unified model which is constructed from a direct product gauge structure by imposing the doublet-triplet splitting.

Modular invariant soft breaking, WMAP, dark matter, and sparticle mass limits

An analysis of soft breaking under the constraint of modular invariance is given. The role of dilaton and moduli dependent front factors in achieving a modular invariant ${V}_{\mathrm{s}\mathrm{o}\mathrm{f}\mathrm{t}}$ is emphasized. Further, it is shown that in string models $\mathrm{tan}\ensuremath{\beta}$ is no longer a free parameter but is determined in terms of ${\ensuremath{\alpha}}_{\mathrm{s}\mathrm{t}\mathrm{r}\mathrm{i}\mathrm{n}\mathrm{g}}$ and the other soft parameters by the constraints of modular invariance and radiative electroweak symmetry breaking. The above framework is then used to analyze the neutralino relic density consistent with the Wilkinson Microwave Anisotropy Probe (WMAP) data at self-dual points in the K\"ahler and complex structure moduli. One finds that the combined set of constraints arising from modular invariant soft breaking, radiative electroweak symmetry breaking, and WMAP lead to upper limits on sparticle masses for $\ensuremath{\mu}&gt;0$. These limits are investigated for a class of models and found to lie within reach of the Tevatron and the Large Hadron Collider. Further, an analysis of the neutralino-proton cross section shows that dark matter in these models can be explored in CDMS (Soudan), GENIUS, and ZEPLIN. While the analysis is carried out within the general framework of heterotic strings, the possibility that the results of the analysis may extend to a broader class of string models, such as models based on intersecting D branes, is also discussed.