共查询到20条相似文献,搜索用时 31 毫秒
1.
M. Drees 《Physics letters. [Part B]》1985,158(5):409-412
It is shown that N=1 supergravity theories can have a GUT scale as large as the Planck scale if the kinetic energy terms for vector superfields are non-minimal. The canonical values for sin2θW (MW), α3 (MW) and are respected. In those theories masses of SU(3), SU(2) and U(1) gauginos may be different at the unification scale. Consequences for the low-energy particle spectrum are discussed in the extreme case where one of the gaugino masses is large while the other two vanish. 相似文献
2.
We construct locally supersymmetric GUTs in which radiative corrections determine all the mass scales which are hierarchically smaller than the Planck mass: , etc. Such no-scale GUTs are based on a hidden sector with a flat potential guaranteed by SU(1, 1) conformal invariance. This is extended to include observable chiral fields in an SU(n, 1)/SU(n) × U(1) structure reminiscent of N ? 5 extended supergravity theories. Tree-level supersymmetry breaking is present only for the gravitino, and for the light gaugino masses through non-minimal kinetic terms reminiscent of N?4 extended supergravity theories. Radiative corrections generate squark and slepton masses which are phenomenologically acceptable, and the right value of mW is obtained if mt ≈ 50 GeV in the simplest such model. 相似文献
3.
We investigate the structure of phenomenological supergravity models which permit the hierarchy problem to be “solved” in the sense that and mW are determined dynamically to be exp [-O(1)/α] × mP. Such models must have a flat hidden sector potential, which is only possible if the theory has an underlying SU(1, 1) invariance. Flat SU(1, 1) theories necessarily have a zero cosmological constant and the hidden sector is an Einstein space with . The SU(1, 1) invariance is necessarily broken down to U(1) by the gravitino mass. If is the only source of SU(1, 1) breaking then the tree-level gaugino masses are small and , while values of A up to 3 and non-zero gaugino masses are possible if other sources of SU(1, 1) breaking are tolerated. Yukawa couplings may scale as some power of in these models where is generated dynamically, which may explain the hierarchy of Higgs-fermion Yukawa couplings: ? These models also permit the spontaneous violation of CP in the Yukawa coupling matrix. Numerical studies yield 20 GeV < mt < 100 GeV in these phenomenological SU(1, 1) supergravity models. Speculations are presented about their relation to a fundamental theory based on extended supergravity. 相似文献
4.
K. Grassie 《Physics letters. [Part B]》1985,159(1):32-36
It is shown that incorporation of a GUT sector in N = 1 supergravity models with radiative SU(2) × U(1) breaking can drastically modify the corresponding low energy phenomenology. The ratio of Higgs VEVs might be much larger than 1, even for small top quark masses (mt = O(40 GeV)). Scenarios of this type necessarily imply large squark and slepton masses , whereas light gluinos can easily be accomodated. Furthermore the upper bound on the mass of the light neutral Higgs becomes as large as MZ and its coupling to down-type quarks and leptons might exceed the standard GWS-value by more than a factor of 5. 相似文献
5.
Rediative masses are generated for the first and the second fermion families by exploiting the idea that their chirality is a symmetry of the “low-energy” SU(3) × SU(2) × U(1) approximation of SU(5), broken only by including the effects of superheavy particles. With only 5's of Higgs coupled to fermions and getting a non-zero vacuum expectation value, we unavoidably get (i) at the grand unification scale; (ii) the charm quark needing a direct mass as the third family; (iii) neutrino masses of size . 相似文献
6.
In this paper we show that D = 11 supergravity admits an infinite discrete class of solutions having the phenomenological group SU(3) ? SU(2) ? U(1) as a symmetry of the internal space M7. These solutions lead, in dimensional reduction, to SU(3) ? SU(2) ? U(1) gauge fields.In general all these spaces produce a complete breaking of supersymmetry except in one case where N = 2 supersymmetry survives. The parameter which classifies the solutions is a rational number q/p which describes the embedding of the stability subgroup SU(2) ? U(1) ? U(1) of M7 in SU(3) ? SU(2) ? U(1). For all q/p ≠ 1 the holonomy group is SO(7) and all supersymmetries are broken. For q/p = 1 the holonomy group is SU(3) and two supersymmetries survive. In this last case we can also find a solution with internal photon curl . It breaks all sypersymmetries. 相似文献
7.
Rodrigo Huerta 《Nuclear Physics B》1982,204(3):413-418
The right-handed neutrino cross sections of the processes νL + ? → νR + ? and νR + ? → νR + ?, where ? is a relativistic lepton, are calculated in the SU(2)L × SU(2)R × U(1) model. According to a cosmological criterion the parameters of the model are bounded. In particular we obtain the bound , assuming the neutrinos are Dirac four-component particles. 相似文献
8.
The implications of a Z4 horizontal symmetry model of flavor mixing for CP violation are studied in the framework of minimal SU(2)L × SU(2)R × U(1)B – L gauge theory. We show that CP violation in this model arises purely from right-handed currents. We also note that spontaneous breaking of CP symmetry requires a fine tuning of coupling parameters to the level of , which can be avoided by the inclusion of one additional singlet Higgs field, of the kind recently introduced for other purposes. 相似文献
9.
H. Kleinert 《Physics letters. [Part B]》1976,62(1):77-80
In quark gluon theory with very small bare masses, -ψ, spontaneous breakdown of chiral symmetry generates sizable masses Mu, Md, Ms, … We find (. Scalar densities have well determined non-zero vaccum expectations at an SU(3) breaking of the vacuum c′ ≡ 〈0|u8|〉/〈0|uo|0〉 ≈ ? 16% 相似文献
10.
We propose a two-component inflation model, based on maximally symmetric supergravity, where the scales of reheating and the inflation potential at the origin are decoupled. This is possible because of the second-order phase transition from SU(5) to SU(3)×SU(2)×U(1) that takes place when φ?φc<φ0, when φ0?O(M) is the value of the inflation at the global minimum, and leads to a reheating temperature TR?(1015–1016) GeV. This makes it possible to generate baryon asymmetry in the conventional way without any conflict with experimental data on proton lifetime. The mass of the gravitinos is , thus avoiding the gravitino problem. Monopoles are diluted by residual inflation in the broken phase below the cosmological bounds if φc?0.3M. 相似文献
11.
The natural conservation of flavours to O(GF2) in neutral weak interactions severely constrains choices of gauge groups as well as their fermion representations. In the absence of exactly conserved quantum numbers other than charge, and of |ΔQ| ? 2 charged currents, essentially the only weak and electromagnetic gauge groups whose neutral interactions naturally conserve all flavours are SU(2)L ? U(1) and SU(2)L ? [U(1)]2. The plausible extensions of these gauge groups to grand unified models including the strong interactions are based on SU(5) and SO(10) respectively. Making the SU(5) model completely natural, including in the Higgs sector, gives the prediction where τ is the probable new heavy lepton and b is the conjectured third flavour of charge . The SO(10) model contains a potential SU(2)L ? SU(2)R ? U(1) weak and electromagnetic gauge group, and has a complicated Higgs structure which does not naturally conserve quark flavours. 相似文献
12.
We reconsider a realistic model of electroweak and strong interactions with calculable mass spectrum at the tree level in which supersymmetry and an extra gauge group factor ?(1) beyond SU(3) × SU(2) × U(1) are both broken at very high energies: , . In spite of these high-energy scales, especially the large scale of supersymmetry breaking, the low energy spectrum - including the relevant Higgs boson - is decoupled from the heavy degrees of freedom. Due to the “non-renormalization” theorems this decoupling persists to all orders in perturbation theory. 相似文献
13.
We propose a class of supergravity models coupled to matter in which the scales of supersymmetry breaking and of weak gauge symmetry breaking are both fixed by dimensional transmutation, not put in by hand. The models have a flat potential with zero cosmological constant before the evaluation of weak radiative corrections which determine . These models are consistent with all particle physi cs and cosmological constraints for top quark masses in the range 30 GeV < mt < 100 GeV. 相似文献
14.
C.A. Piketty 《Nuclear Physics B》1974,68(1):44-65
We have evaluated the parity-violation contribution in atoms in the framework of SO(3) gauge theory. Various hadronic models have been used: first, for simplicity, the unrealistic five-quark one, next, others involving three ordinary SU(3) triplets for which all unwanted strangeness-changing processes are suppressed, up to order . In the free quark approximation, we obtain quite similar parity-violation effects which are proportional to (ΔM2 is the difference of squared masses of leptons (MX02 ? Mν2 = MX02), or of quarks (ΔMq2)). Namely, in large atoms (Z ? 1) the electronic contribution which is proportional to gives the largest effect (are the spin, momentum operators and mass of the lepton). Parity-violating effects in SO(3) gauge models are ?10?4 smaller than those evaluated in the Weinberg theory with a neutral parity-violating current and will remain undetectable in the near future. 相似文献
15.
Zhao Zhiyong 《Nuclear Physics B》1983,212(2):224-236
The phenomenological predictions of the SO(10) supersymmetric grand unified model (SO(10) SGUM) for the mass scales M1, M2, weak angle ifsin2θw, quark-leptons mass ratios , , and proton lifetime τp are estimated by using renormalization group analysis at one-loop level. In contrast with SU(5) SGUM, we find that the SO(10) SGUM still has problems with τp but not with sin2θw and , which may suggest that supersymmetry would be bro at a mass scale . 相似文献
16.
We make a careful analysis of the constraints on supergravity parameters from the requirement of SU(2)×U(1) symmetry breaking. Since we obtain fully analytic solutions to the relevant renormalization group equations, we are able to explore the whole range of parameters. Breaking electroweak symmetry with a light top quark leads to a strong correlation between the dimensionless parameters and the mass ratios in the supergravity lagrangian. However, the overall mass scale, e.g. , is not fixed by this requirements. The bound on the lightest neutral Higgs boson is reexamined. The lightest squark is usually an s-top, but we easily find cases where it is a s-bottom. Unfortunately the low-energy constraints provide no useful guidelines for experimentalists. 相似文献
17.
Stuart Raby 《Nuclear Physics B》1981,187(3):446-460
We propose a new mechanism for up-down symmetry breaking within the context of a technicolor scenario. The experimentally determined ratio is in addition preserved at the technicolor scale. If we assume that the mechanism works at the level of the heaviest generation we find . The parameter ? depends on strong technicolor dynamics and can in principle be determined. Via a crude estimate we find ? to be a number of order 1. 相似文献
18.
19.
We delineate the domain of supersymmetry breaking parameters in minimal supergravity models for which the cosmological relic photino density is no larger than the closure density. Demanding that the relic density equal the closure density as suggested by inflationary cosmology suggests . We point out that several supergravity scenarios for the monojet events at the CERN p Collider would yield a relic density considerably greater than the closure density. 相似文献
20.
Michael Grady 《Nuclear Physics B》1983,221(1):16-28
We show that the successful relation Mw = Mz cos θ is preserved in the technicolor formulation of the dynamical Higgs mechanism provided only that the creation operators for Goldstone bosons associated with broken generators belong to the representation of the weak isospin group. We present a plausibility argument that this is indeed the case. No additional isospin or isospin-like global SU(2) symmetries are then required allowing isospin to be spontaneously broken. This may be of help in producing a large splitting. It is also shown how the weak hyperchange interaction can produce substantial vacuum isospin breaking in a theory which is only marginally asymptotically free. This mechanism predicts , providing a natural explanation for small neutrino masses. 相似文献