Bryan W. Lynn

Electroweak radiative corrections with an effective lagrangian: Four-fermions processes

We present a new, more concise method for computing and organizing electroweak radiative corrections, based on an effective lagrangian and incorporating a large class of diagrams into a few simple running couplings without use of truncated renormalization group approximations. We apply this technique to the case of four-fermion processes. Special emphasis is placed on the effects of heavy particles on low-energy physics and how such phenomena can be classified and measured in the new generation of precision electroweak experiments - in particular, experiments with polarized e− beams at the SLC and LEP.

Electroweak Cross-Sections and Asymmetries at the Z0

Abstract We present complete calculations for basic observables at the SLC/LEP e + e − colliders: the Z 0 cross sections, line shape and width, forward-backward and polarizat asymmetries effects of experimental cuts are explored. Special emphasis is placed on the polarization asymmetry, a highly sensitive measure of electroweak couplings and of the presence of heavy particles in virtual loops. The calculations were performed using a new, more efficient Monte Carlo method, which is also discussed.

Delayed unitary cancellation and heavy particle effects in e+e−→W+W−

Abstract We examine one-loop radiative corrections to e+e−→W+W− in the standard model with one Higgs doublet, concentrating on the effects of very heavy fermions. These disturb the delicate unitarity cancellation between s- and t-channel diagrams, raising the cross section even well below the fermion threshold and giving a clear experimental signature for the heavy sector.

Chiral SU(2)L × SU(2)R liquids: a theory of heavy nuclei and neutron stars

Abstract The global SU(2) L × SU(2) R symmetries of QCD probably imply the existence of a liquid phase consisting of protons, neutrons and pions. Drops of this “chiral liquid” at zero external pressure emerge as saturating (the baryon number grows roughly as the volume) nontopological solitons of the low energy non-linear chiral effective lagrangian theory of pions and nucleons, where the pions are the pseudo-Goldstone bosons resulting from the spontaneous breaking of SU(2) L − R by the QCD vacuum. Chiral perturbation theory of linear SU(2) L + R × non-linear SU(2) L − R gives us control of both the tree and quantum loop levels of the theory. A crucial role is played by explicit SU(2) L − R breaking terms whose origin lies in quark masses; an isosinglet combination of even numbers of pions carries the primary long-range attractive force. If non-linear chiral symmetry contains such saturating nontopological soliton field configurations, they would give a chiral-symmetric explanation for the existence of ordinary heavy nuclei, which are then to be regarded as just droplets of chiral liquid. This picture, reminiscent of the old liquid drop model of heavy nuclei, vastly simplifies the extraction of bulk nuclear properties from chiral symmetry; nucleons, treated as Fermi fluids inside a heavy nucleus, move within a huge coherent self-consistent classical pion field 〈π 2 〉 1 2 t~ 200–400 MeV . Neutron stars are then just great oceans of neutral chiral liquid held together by gravity. Quantum chiral liquids can have interesting macroscopic quantum properties such as the spontaneous breaking of parity with parity doubling; these may distinguish experimentally the chiral liquid theory of heavy nuclei and neutron stars from more conventional models.

New models for neutron stars

A new type of neutron star model (Q stars), in which high-density, electrically neutral baryonic matter is a coherent classical solution to an effective field theory of strong forces, and is bound in the absence of gravity, is considered. This model allows massive compact objects (suggesting that Cygnus X-1 and LMC X-3 may not be black holes), and has no macroscopic minimum mass. Because laboratory experiments on ordinary nuclei do not constrain the properties of bulk baryon matter, there is a wide new range of theoretical possibilities for compact objects. 38 refs.

Fermion Q-stars

Abstract We describe fermion Q-stars, a class of non-topological classical solutions of field theories containing interacting fermions and bosons. These objects generalize Q-balls by including fermions and classical Einstein gravity, and have interesting astrophysical applications.

Are neutron stars Q-stars?

We show that certain classical solutions of hadronic effective field theories can model neutron stars. Within the uncertainties of what is known from laboratory measurements of nuclear physics, these solutions, called Q-stars, may have masses much larger (⪢ 3 M ⊙) or may be able to rotate faster (Prot < 0.5 ms) than previously believed possible. Stable chunks of nuclear density baryonic matter varying in size from 10−12 cm to several kilometers may also exist. Cygnus X-1, LMC X-3, and the SN1987A remnant are candidates for Q-stars.

Strange baryon matter

Abstract Using the non-linear SU(3)L × SU(3)R chiral lagrangian coupled to a field theory of nuclear forces, we show that a bound state of baryons with a well-defined surface may conceivably form in the presence of kaon condensation. This state is of similar density to ordinary nuclei, but has net strangeness equal to about two thirds the baryon number. We discuss the properties of lumps of strange baryon matter with baryon number between ∼ 20 and ∼ 1057 where gravitational effects become important. The possibility that the ground state of baryonic matter at zero pressure is strange and that ordinary nuclei may only be metastable has important consequences for laboratory nuclear physics, the early universe and astrophysical compact objects.

Precision measurements of final state weak coupling from polarized electron-positron annihilation

Abstract We introduce and analyse the longitudinally polarized forward-backward asymmetry A FB pol for electron-positron annihilation on Z 0 resonance. We show that a specific combination of data taken with two opposite electron polarizations is independent of the initial state details including one-loop electroweak and bremsstrahlung effects. This remarkable property would allow the weak coupling of the produced final state (μ, ρ, b , c , …) to be measured in a clean and very promising way at LEP/SLC.

Atomic enhancements in the detection of weakly interacting particles

Abstract Proposed holometric and supercolloidal detectors can measure energy depositions of the order of atomic energies. At these energies, atomic bound state effects lead to great enhancements in the detection of weakly interacting particles. As an example, we show that solar axions could give event rates 10 5 –10 6 times larger than published neutrino detector design capabilities. Thus, relatively small detectors might see solar axions.