1,721,049 research outputs found
Aspects of symmetry breaking in SO(10) GUTs
No full textI review some recent results on the Higgs sector of minimal SO(10) grand unified theories both with and without supersymmetry. It is shown that nonsupersymmetric SO(10) with just one adjoint triggering the first stage of the symmetry breaking does provide a successful gauge unification when radiative corrections are taken into account in the scalar potential, while in the supersymmetric case it is argued that the troubles in achieving a phenomenologically viable breaking with representations up to the adjoint are overcome by considering the flipped SO(10) embedding of the hypercharge
Unification scale versus electroweak-triplet mass in the SU(5)+24 F model at three loops
No full textIt was shown recently that the original SU(5) theory of Georgi and Glashow, augmented with an adjoint fermionic multiplet 24F, 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- leading order. Such an accuracy on the theory side is necessary in order to settle the convergence of the perturbative expansion and to match the experimental precision on the determination of the electroweak gauge couplings at the Z-boson mass scale. © 2013 American Physical Society
Recent developments in nonsupersymmetric SO(10) unification
Get PDFI review the recent efforts in the search for a minimal and predictive
nonsupersymmetric SO(10) theory. The outcome is the revival of a minimal scenario
in which an old result, claiming the incompatibility between unification constraints
and symmetry-breaking dynamics, is now confuted by the implementation of the
one-loop effective potential
Pati-Salam Axion
Get PDFI discuss the implementation of the Peccei-Quinn mechanism in a minimal realization of the Pati-Salam partial unification scheme. The axion mass is shown to be related to the Pati-Salam breaking scale and it is predicted via a two-loop renormalization group analysis to be in the window eV, as a function of a sliding Left-Right symmetry breaking scale. This parameter space will be fully covered by the late phases of the axion Dark Matter experiments ABRACADABRA and CASPEr-Electric. A Left-Right symmetry breaking scenario as low as 20 TeV is obtained for a Pati-Salam breaking of the order of the reduced Planck mass
Accidental SO(10) axion from gauged flavour
Get PDFAn accidental U(1) Peccei-Quinn (PQ) symmetry automatically arises in a class of SO(10) unified theories upon gauging the SU(3)f flavour group. The PQ symmetry is protected by the center of SO(10)×SU(3) up to effective operators of canonical dimension nine (developing high-scale contributions to the axion potential). In the pre-inflationary PQ breaking scenario the axion mass window is predicted to be ∈[7×10,10] eV, where the lower end is bounded by the seesaw scale and the upper end by iso-curvature fluctuations. A high-quality axion, that is immune to the PQ quality problem, is obtained for ≳0.02 eV. We finally offer a general perspective on the PQ quality problem in 4D grand unified theories
Framework for baryonic R-parity violation in grand unified theories
No full textWe investigate the possibility of obtaining sizeable R-parity breaking interactions violating baryon number but not lepton number within supersymmetric grand unified theories. Such a possibility allows to ameliorate the naturalness status of supersymmetry while maintaining successful gauge coupling unification, one of its main phenomenological motivations. We show that this can be achieved without fine-tuning or the need of large representations in simple SO(10) models
Minimal flavour violation and neutrino masses without R-parity
No full textWe study the extension of the Minimal Flavour Violation (MFV) hypothesis to the MSSM without R-parity. The novelty of our approach lies in the observation that supersymmetry enhances the global symmetry of the kinetic term and in the fact that we consider as irreducible sources of the flavour symmetry breaking all the couplings of the superpotential including the R-parity violating ones. If R-parity violation is responsible for neutrino masses, our setup can be seen as an extension of MFV to the lepton sector. We analyze two patterns based on the non-abelian flavour symmetries SU(3) 4 ⊗SU(4) and SU(3) 5. In the former case the total lepton number and the lepton flavour number are broken together, while in the latter the lepton number can be broken independently by an abelian spurion, so that visible effects and peculiar correlations can be envisaged in flavour changing charged lepton decays like l i → l jγ. © SISSA 2012
Stability of the electroweak ground state in the Standard Model and its extensions
No full textWe review the formalism by which the tunnelling probability of an unstable ground state can be computed in quantum field theory, with special reference to the Standard Model of electroweak interactions. We describe in some detail the approximations implicitly adopted in such calculation. Particular attention is devoted to the role of scale invariance, and to the different implications of scale-invariance violations due to quantum effects and possible new degrees of freedom. We show that new interactions characterized by a new energy scale, close to the Planck mass, do not invalidate the main conclusions about the stability of the Standard Model ground state derived in absence of such terms
Towards a new minimal SO(10) unification
No full textWe argue that non-supersymmetric SO(10) models based on a renormalizable Higgs sector in which spontaneous symmetry breaking is triggered by the VEVs of a 45-dimensional adjoint and a 126-dimensional tensor representations can provide a potentially realistic yet relatively simple framework for a future robust estimate of the proton lifetime. Following closely the work [1] we comment on the gauge unification constraints on the B - L breaking scale and show that there are several regions in the parameter space of the minimal model where the seesaw scale in the phenomenologically favoured ballpark of around 1013÷14GeV is consistently supported. © 2012 American Institute of Physics
- …
