John F. Donoghue

General relativity as an effective field theory: The leading quantum corrections

I describe the treatment of gravity as a quantum effective field theory. This allows a natural separation of the (known) low energy quantum effects from the (unknown) high energy contributions. Within this framework, gravity is a well-behaved quantum field theory at ordinary energies. In studying the class of quantum corrections at low energy, the dominant effects at large distance can be isolated, as these are due to the propagation of the massless particles ( including gravitons) of the theory and are manifested in the nonlocal and/or nonanalytic contributions to vertex functions and propagators. These leading quantum corrections are parameter-free and represent necessary consequences of quantum gravity. The methodology is illustrated by a calculation of the leading quantum corrections to the gravitational interaction of two heavy masses.

Unified Treatment of the Parity Violating Nuclear Force

Abstract We discuss the weak amplitudes which determine the parity violating nuclear force. By use of the quark model and the SU(6)ω symmetry, we unite the treatment of pion and vector meson vertices, and describe the interrelation of past techniques which have been applied to this problem. This allows us to catalog the uncertainties in the amplitudes, and to provide reasonable bounds on their values. The connection of our results with experiment is also discussed.

Union of chiral and heavy quark symmetries

Abstract We describe the chiral symmetric couplings of pions to heavy mesons (B or D), valid in the portion of phase space where the pions have low momentum. In order to include consistently all low energy excitations, the vector mesons (B ∗ or D ∗ ) must appear explicitly in the effective lagrangian. The result is then invariant under both the chiral and heavy quark symmetries. We include matrix elements relevant for various weak decays.

Flavour changes in locally supersymmetric theories

Abstract Locally supersymmetric models lead in general to flavour-changing gluino exchanges. We derive the necessary expressions for describing them in detail. We show that the K 0  K 0 mixing puts a lower bound on the gravitino mass and gives new restrictions on the Kobayashi-Maskawa angles.

The Quark Content of the Proton

Abstract The quark content of the proton is studied using the quark scalar bilinear, q q, as a probe. An analysis of hadron masses and the sigma term suggests an unexpectedly large signal for s s. This is seen to be reasonable within both the Skyrme model and the bag model. The interpretation of the quark content is discussed in both models.

The ΔS = 2 matrix element for K0−K̄0 mixing

Abstract We use SU(3) and PACAC to relate the ΔS = 2 matrix element M = 〈 K 0 | d γ μ (1 + γ 5 )s d γ μ (1 + γ 5 )s| K 0 〉 to experimental information on the ΔI = 3 2 contribution to K → 2π. Our results is M = 0.10 m K 4 which is about 33% of the vacuum insertion value.

The decay of a light Higgs boson

Abstract We discuss the hadronic form factors which are required for the prediction of the decay rate of scalar Higgs bosons, including non-standard generalizations. We calculate the next-to-leading order corrections to the low-energy theorems of chiral symmetry, and use dispersion relations to determine the couplings at higher energy.

The anthropic principle and the mass scale of the Standard Model

In theories in which different regions of the universe can have different values of the the physical parameters, we would naturally find ourselves in a region which has parameters favorable for life. We explore the range of anthropically allowed values of the mass parameter in the Higgs potential, µ 2 . For µ 2 0, baryon stability requires that |µ| << MP, the Planck Mass. Smaller values of � µ 2 � may or may not be allowed depending on issues of element synthesis and stellar evolution. We conclude that the observed value of µ 2 is reasonably typical of the anthropically allowed range, and that anthropic arguments provide a plausible explanation for the closeness of the QCD scale and the weak scale.

SU(3) Baryon Chiral Perturbation Theory and Long Distance Regularization

The use of SU(3) chiral perturbation theory in the analysis of low energy meson-baryon interactions is discussed. It is emphasized that short distance effects, arising from propagation of Goldstone bosons over distances smaller than a typical hadronic size, are modeldependent and can lead to a lack of convergence in the SU(3) chiral expansion if they are included in loop diagrams. In this paper we demonstrate how to remove such effects in a chirally consistent fashion by use of a cutoff and demonstrate that such removal ameliorates problems which have arisen in previous calculations due to large loop effects.

Systematics of soft final-state interactions in B decays

By using very general and well established features of soft strong interactions we show, contrary to conventional expectations, that (i) soft final state interactions (FSI) do not disappear for large {ital m}{sub {ital B}}, (ii) inelastic rescattering is expected to be the main source of soft FSI phases, and (iii) FSI which interchange charge and/or flavors are suppressed by a power of {ital m}{sub {ital B}}, but are quite likely to be significant at {ital m}{sub {ital B}}{approx_equal}5 GeV. We briefly discuss the influence of these interactions on tests of {ital CP} violation and on theoretical calculations of weak decays. {copyright} {ital 1996 The American Physical Society.}