Elizabeth Jenkins

Baryon chiral perturbation theory using a heavy fermion Lagrangian

Baryon chiral perturbation theory is developed using an effective lagrangian in which the baryons appear as heavy static fields. The chiral logarithmic corrections to the axial current for semileptonic hyperon decay and for the analysis of the strangeness content of the proton are computed as examples. The corrections are as big as the lowest order values, which implies that F and D cannot be reliably extracted from hyperon semileptonic decays.

Renormalization group evolution of the Standard Model dimension six operators III: gauge coupling dependence and phenomenology

A bstractWe calculate the gauge terms of the one-loop anomalous dimension matrix for the dimension-six operators of the Standard Model effective field theory (SM EFT). Combining these results with our previous results for the λ and Yukawa coupling terms completes the calculation of the one-loop anomalous dimension matrix for the dimension-six operators. There are 1350 CP -even and 1149 CP -odd parameters in the dimension-six Lagrangian for 3 generations, and our results give the entire 2499 × 2499 anomalous dimension matrix. We discuss how the renormalization of the dimension-six operators, and the additional renormalization of the dimension d ≤ 4 terms of the SM Lagrangian due to dimension-six operators, lays the groundwork for future precision studies of the SM EFT aimed at constraining the effects of new physics through precision measurements at the electroweak scale. As some sample applications, we discuss some aspects of the full RGE improved result for essential processes such as gg → h, h → γγ and h → Zγ, for Higgs couplings to fermions, for the precision electroweak parameters S and T, and for the operators that modify important processes in precision electroweak phenomenology, such as the three-body Higgs boson decay h → Z ℓ+ℓ− and triple gauge boson couplings. We discuss how the renormalization group improved results can be used to study the flavor problem in the SM EFT, and to test the minimal flavor violation (MFV) hypothesis. We briefly discuss the renormalization effects on the dipole coefficient Ceγ which contributes to μ → eγ and to the muon and electron magnetic and electric dipole moments.

Chiral corrections to the baryon axial currents

Abstract Chiral logarithmic corrections to the baryon axial vector currents in semileptonic hyperon decay are computed including intermediate octet and decuplet states, and it is shown that the spin- 3 2 decuplet partially cancels the large spin- 1 2 octet contribution corrections to the quark currents are also computed.

Renormalization group evolution of the standard model dimension six operators. I: formalism and λ dependence

A bstractWe calculate the order λ, λ2 and λy2 terms of the 59 × 59 one-loop anomalous dimension matrix of dimension-six operators, where λ and y are the Standard Model Higgs self-coupling and a generic Yukawa coupling, respectively. The dimension-six operators modify the running of the Standard Model parameters themselves, and we compute the complete one-loop result for this. We discuss how there is mixing between operators for which no direct one-particle-irreducible diagram exists, due to operator replacements by the equations of motion.

Renormalization group evolution of the Standard Model dimension six operators II: Yukawa dependence

A bstractWe calculate the complete order y2 and y4 terms of the 59 × 59 one-loop anomalous dimension matrix for the dimension-six operators of the Standard Model effective field theory, where y is a generic Yukawa coupling. These terms, together with the terms of order λ, λ2 and λy2 depending on the Standard Model Higgs self-coupling λ which were calculated in a previous work, yield the complete one-loop anomalous dimension matrix in the limit of vanishing gauge couplings. The Yukawa contributions result in non-trivial flavor mixing in the various operator sectors of the Standard Model effective theory.

Renormalization group scaling of Higgs operators and h → γγ decay

A bstractWe compute the renormalization of dimension six Higgs-gauge boson operators that can modify the h → γγ rate at tree-level. Operator mixing is shown to lead to an important modification of new physics effects which has been neglected in past calculations. We also find that the usual formula for the S oblique parameter contribution of these Higgs-gauge boson operators needs additional terms to be consistent with renormalization group evolution. We study the implications of our results for Higgs phenomenology and for new physics models which attempt to explain a deviation in the h → γγ rate. We derive a new relation between the S parameter and the h → γγ and h → Zγ decay rates.

Baryon masses in chiral perturbation theory

Abstract Chiral corrections to baryon mass relations are computed using a chiral lagrangian which includes the spin - 3 2 baryon decuplet. The observed accuracies of the Gell-Mann-Okubo formula for baryon octet masses and of Gell-Manns equal spacing rule for decuplet masses are consistent with chira; perturbation theory up to order m s 2 .

Testing the cosmic coincidence problem and the nature of dark energy.

Dark energy models which alter the relative scaling behavior of dark energy and matter could provide a natural solution to the cosmic coincidence problem-why the densities of dark energy and dark matter are comparable today. A generalized class of dark energy models is introduced which allows noncanonical scaling of the ratio of dark matter and dark energy with the Robertson-Walker scale factor a(t). We show that determining whether there is a coincidence problem, and the extent of cosmic coincidence, can be addressed by several forthcoming experiments.

The effective Lagrangian for the seesaw model of neutrino mass and leptogenesis

Abstract The effective Lagrangian for the seesaw model is derived including effects due to CP -violation. Besides the usual dimension-5 operator responsible for light neutrino masses, a dimension-6 operator is obtained. For three or less heavy neutrino generations, the inclusion of both operators is necessary and sufficient for all independent physical parameters of the high-energy seesaw Lagrangian to appear in the low-energy effective theory, including the CP -odd phases relevant for leptogenesis. The dimension-6 operator implies exotic low-energy couplings for light neutrinos, providing a link between the high-energy physics and low-energy observables.

Renormalization group evolution of dimension-six baryon number violating operators

Abstract We calculate the one-loop anomalous dimension matrix for the dimension-six baryon number violating operators of the Standard Model effective field theory, including right-handed neutrino fields. We discuss the flavor structure of the renormalization group evolution in the contexts of minimal flavor violation and unification.