Huang Q.-G.,CAS Institute of Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015
Imposing that the excursion distance of the inflaton in field space during inflation be less than the Planck scale, we derive an upper bound on the tensor-to-scalar ratio at the cosmic microwave background scales, i.e., r∗,max, in the general canonical single-field slow-roll inflation model, in particular, the model with non-negligible running of the spectral index αs and/or the running of running βs. We find that r∗,max≃7×10-4 for ns=0.9645 without running and running of running, and r∗,max is significantly relaxed to the order of O(10-2∼10-1) in the inflation model with αs and/or βs∼+O(10-2) which are marginally preferred by the Planck 2015 data. © 2015 American Physical Society.
Zhao Z.-H.,CAS Institute of Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012
In this paper, we give a model for understanding flavor physics in the lepton sector mass hierarchy among different generations and neutrino mixing patterns. The model is constructed in the framework of supersymmetry, with a family symmetry S4*U(1). There are two right-handed neutrinos introduced for a seesaw mechanism, while some standard model gauge group singlet fields are included, which transforms nontrivially under family symmetry. In the model, each order of contributions are suppressed by δ∼0.1 compared to the previous one. In order to reproduce the mass hierarchy, m τ and √Δmatm2, and m μ and √Δmsol2 are obtained at leading order and next-to-leading order, respectively, while the electron can only get its mass through next-to-next-to-next-to-leading order contributions. For neutrino mixing angels, θ 12, θ 23, θ 13 are 45°, 45°, 0, i.e., the bimaximal mixing pattern as a first approximation, while higher order contributions can make them consistent with experimental results. As corrections for θ 12 and θ 13 originate from the same contribution, there is a relation predicted for them: sinθ 13=1- tanθ 121+tanθ 12. Besides, the deviation from π4 for θ 23 should have been as large as the deviation from 0 for θ 13; if not, the former is suppressed by a factor of 4 compared to the latter. © 2012 American Physical Society.
Shu J.,CAS Institute of Theoretical Physics |
Zhang Y.,California Institute of Technology
Physical Review Letters | Year: 2013
We observe a generic connection between LHC Higgs data and electroweak baryogenesis: the particle that contributes to the CP-odd hgg or hγγ vertex would provide the CP-violating source during a first-order phase transition. It is illustrated in the two Higgs doublet model that a common complex phase controls the lightest Higgs properties at the LHC, electric dipole moments, and the CP-violating source for electroweak baryogenesis. We perform a general parametrization of Higgs effective couplings and a global fit to the LHC Higgs data. Current LHC measurements prefer a nonzero phase for tana 1 and electric dipole moment constraints still allow an order-one phase for tana β∼1, which gives sufficient room to generate the correct cosmic baryon asymmetry. We also give some prospects in the direct measurements of CP violation in the Higgs sector at the LHC. © 2013 American Physical Society.
Pang Y.,CAS Institute of Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011
In this note, we correct a mistake in the mass formula in which generalizes the Ashtekar-Magnon-Das method to incorporate extended gravities with quadratic curvature terms. The corrected mass formula confirms that the black hole masses for recently discovered critical gravities vanish. © 2011 American Physical Society.
Parry J.K.,CAS Institute of Theoretical Physics
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011
We study the new physics (NP) implications of the recently reported 3.2 σ Standard Model (SM) deviation in the like-sign dimuon asymmetry at the Tevatron. Assuming that new physics only enters the Bs mixing amplitude we explore the implications for generic new physics, general supersymmetric (SUSY) models and also SUSY SU(5). In the case of SUSY SU(5) we exploit the GUT scale relationship between slepton and squark soft masses to predict rates for lepton flavour violation (LFV). The predicted rates for τ→μγ are found to be detectable at future Super- B factories. © 2010 Elsevier B.V.