arXiv subjects

Barry R. Holstein

Publications and source records attributed to Barry R. Holstein.

At least 19 recordsLinked to original sources

arXiv2023

On-Shell Calculation of Mixed Electromagnetic and Gravitational Scattering

The study of long-range effects arising from the higher order exchange of massless particles via summation of Feynman diagrams is well known, but recently it has been shown that the use of on-shell methods can provide a streamlined route to the calculation of both electromagnetic and gravitational effects. In this note we demonstrate that the use of on-shell methods yields a similar simplification in the evaluation of higher order effects in the case of mixed electromagnetic and gravitational scattering.

nucl-th↗

arXiv2017

Bending of Light in Quantum Gravity

We consider the scattering of lightlike matter in the presence of a heavy scalar object (such as the Sun or a Schwarzschild black hole). By treating general relativity as an effective field theory we directly compute the nonanalytic components of the one-loop gravitational amplitude for the scattering of massless scalars or photons from an external massive scalar field. These results allow a semiclassical computation of the bending angle for light rays grazing the Sun, including long-range $\hbar$ contributions. We discuss implications of this computation, in particular the violation of some classical formulations of the equivalence principle.

hep-th↗

arXiv2017

A New Paradigm for Hadronic Parity Nonconservation and its Experimental Implications

For decades the primary experimental goal in studies of hadronic parity nonconservation (PNC) has been the isolation of the isovector weak nucleon-nucleon interaction, expected to be dominated by long-range pion exchange and enhanced by the neutral current. In meson-exchange descriptions this interaction together with an isoscalar interaction generated by rho and omega exchange dominate most observables. Consequently these two amplitudes have been used to compare and check the consistency of the field's experiments. Yet to date, despite sensitive searches like that performed with 18F, no evidence for isovector hadronic PNC has been found. Here we argue, based on recent large-Nc treatments and new global analyses, that the emphasis on isovector hadronic PNC was misplaced. Large-Nc provides an alternative and theoretically better motivated simplification of effective field theories (EFTs) of hadronic PNC, separating the five low-energy constants (LECs) into two of leading order (LO), and three others that are NNLO. This scheme pivots the isospin coordinates we have traditionally used, placing one dominant axis in the isoscalar plane, and a second along the isotensor direction. We show that this large-Nc LEC hierarchy accurately describes all existing data on hadronic PNC, and we discuss opportunities to further test the predicted large-Nc hierarchy of LECs, illustrating the kind of analyses experimentalists can use to better constrain the LO theory and to determine the size of NNLO corrections.

nucl-th↗

arXiv2017

Illuminating Light Bending

The interactions of gravitons with spin-1 matter are calculated in parallel with the well known photon case. It is shown that graviton scattering amplitudes can be factorized into a product of familiar electromagnetic forms, and cross sections for various reactions are straightforwardly evaluated using helicity methods. Universality relations are identified. Extrapolation to zero mass yields scattering amplitudes for photon-graviton and graviton-graviton scattering. The phenomenon of light bending near a massive object, which is generally treated using classical general relativity, is discussed from alternative points of view.

gr-qc↗

arXiv2017

Light-like Scattering in Quantum Gravity

We consider scattering in quantum gravity and derive long-range classical and quantum contributions to the scattering of light-like bosons and fermions (spin-0, spin-1/2, spin-1) from an external massive scalar field, such as the Sun or a black hole. This is achieved by treating general relativity as an effective field theory and identifying the non-analytic pieces of the one-loop gravitational scattering amplitude. It is emphasized throughout the paper how modern amplitude techniques, involving spinor-helicity variables, unitarity, and squaring relations in gravity enable much simplified computations. We directly verify, as predicted by general relativity, that all classical effects in our computation are universal (in the context of matter type and statistics). Using an eikonal procedure we confirm the post-Newtonian general relativity correction for light-like bending around large stellar objects. We also comment on treating effects from quantum hbar dependent terms using the same eikonal method.

hep-th↗

arXiv2016

Analytical On-shell Calculation of Higher Order Scattering: Massless Particles

We demonstrate that the use of on-shell methods involving calculation of the discontinuity across the t-channel cut associated with the exchange of a pair of massless particles can be used to evaluate loop contributions to the electromagnetic and gravitational scattering of both massive and massless particles. In the gravitational case the use of factorization permits a straightforward and algebraic calculation of higher order scattering results, which were obtained previously by considerably more arduous Feynman diagram techniques.

hep-ph↗

arXiv2016

Analytical On-shell Calculation of Higher Order Scattering: Massive Particles

We demonstrate that the use of on-shell methods, involving calculation of the discontinuity across the t-channel cut associated with the exchange of a pair of massless particles, can be used to evaluate loop contributions to both the electromagnetic and gravitational scattering of massive systems. In the gravitational case, the use of factorization permits a straightforward and algebraic calculation of higher order scattering results, which were obtained previously by much more arduous Feynman diagram techniques.

hep-ph↗

arXiv2016

Analytical On-shell Calculation of Low Energy Higher Order Scattering

We demonstrate that the use of analytical on-shell methods involving calculation of the discontinuity across the t-channel cut associated with the exchange of a pair of massless particles (photons or gravitons) can be used to evaluate one-loop contributions to electromagnetic and gravitational scattering, with and without polarizability, reproducing via simple algebraic manipulations, results obtained previously, generally using Feynman diagram techniques. In the gravitational case the use of factorization permits a straightforward and algebraic calculation of higher order scattering without consideration of ghost contributions or of triple-graviton couplings, which made previous evaluations considerably more arduous.

hep-ph↗

arXiv2015

Low Energy Theorems of Quantum Gravity from Effective Field Theory

In this survey, we review some of the low energy quantum predictions of General Relativity which are independent of details of the yet unknown high-energy completion of the gravitational interaction. Such predictions can be extracted using the techniques of effective field theory.

gr-qc↗

arXiv2015

The Equivalence Principle in a Quantum World

We show how modern methods can be applied to quantum gravity at low energy. We test how quantum corrections challenge the classical framework behind the Equivalence Principle, for instance through introduction of non-locality from quantum physics, embodied in the Uncertainty Principle. When the energy is small we now have the tools to address this conflict explicitly. Despite the violation of some classical concepts, the EP continues to provide the core of the quantum gravity framework through the symmetry - general coordinate invariance - that is used to organize the effective field theory.

hep-th↗

arXiv2015

Graviton-Photon Scattering

We use the feature that the gravitational Compton scattering amplitude factorizes in terms of Abelian QED amplitudes to evaluate various gravitational Compton processes. We examine both the QED and gravitational Compton scattering from a massive spin-1 system by the use of helicity amplitude methods. In the case of gravitational Compton scattering we show how the massless limit can be used to evaluate the cross section for graviton-photon scattering and discuss the difference between photon interactions and the zero mass spin-1 limit. We show that the forward scattering cross section for graviton photoproduction has a very peculiar behavior, differing from the standard Thomson and Rutherford cross sections for a Coulomb-like potential.

gr-qc↗

arXiv2013

Hadron Polarizabilities

Electromagnetic polarizabilities describe the response of a system to the application of an external quasi-static electric or magnetic field. In this article experimental and theoretical work addressing the polarizabilities of the light hadrons is examined.

hep-ph↗

arXiv2013

Neutral Pion Lifetime Measurements and the QCD Chiral Anomaly

A fundamental property of QCD is the presence of the chiral anomaly, which is the primary component of the $π^0\rightarrowγγ$ decay amplitude. Based on this anomaly and its small ($\simeq$ 4.5%) chiral correction, a firm prediction of the $π^0$ lifetime can be used as a test of QCD at confinement scale energies. The interesting experimental and theoretical histories of the $π^0$ meson are reviewed, from discovery to the present era. Experimental results are in agreement with the theoretical prediction, within the current ($\simeq$ 3%) experimental error; however, they are not yet sufficiently precise to test the chiral corrected result, which is a firm QCD prediction and is known to $\simeq$ 1% uncertainty. At this level there exist experimental inconsistencies, which require attention. Possible future work to improve the present precision is suggested.

hep-ph↗

arXiv2011

Hyperon forward spin polarizabilty gamma0

We present the results of a systematic leading order calculation of hyperon Compton scattering and extract the forward spin polarizability gamma0 of hyperons within the framework of SU(3) heavy baryon chiral perturbation theory (HBChPT). The results obtained for gamma0 in the case of nucleons agree with that of the known results of SU(2) HBChPT when kaon loops are not considered.

hep-ph↗

arXiv2008

Semileptonic decays of the light J(P)=1/2(+) ground state baryon octet

We calculate the semileptonic baryon octet-octet transition form factors using a manifestly Lorentz covariant quark model approach based on the factorization of the contribution of valence quarks and chiral effects. We perform a detailed analysis of SU(3) breaking corrections to the hyperon semileptonic decay form factors. We present complete results on decay rates and asymmetry parameters including lepton mass effects for the rates.

hep-ph↗

arXiv2008

Chiral corrections to the vector and axial couplings of quarks and baryons

We calculate chiral corrections to the semileptonic vector and axial quark coupling constants using a manifestly Lorentz covariant chiral quark approach up to order O(p4) in the two- and tree-flavor picture. These couplings are then used in the evaluation of the corresponding couplings which govern the semileptonic transitions between octet baryon states. In the calculation of baryon matrix elements we use a general ansatz for the spatial form of the quark wave function, without referring to a specific realization of hadronization and confinement of quarks in baryons. Matching the physical amplitudes calculated within our approach to the model-independent predictions of baryon chiral perturbation theory (ChPT) allows one to deduce the connection between our parameters and those of baryon ChPT.

hep-ph↗

arXiv2008

Long Range Electromagnetic Effects involving Neutral Systems and Effective Field Theory

We analyze the electromagnetic scattering of massive particles with and without spin wherein one particle (or both) is electrically neutral. Using the techniques of effective field theory, we isolate the leading long distance effects, both classical and quantum mechanical. For spinless systems results are identical to those obtained earlier via more elaborate dispersive methods. However, we also find new results if either or both particles carry apin.

hep-ph↗

arXiv2008

Long Distance Effects in Mixed Electromagnetic-Gravitational Scattering

Using the methods of effective field theory we examine long range effects in mixed electromagnetic-gravitational scattering. Recent calculations which have yielded differing results for such effects are examined and corrected. We consider various spin configurations of the scattered particles and find that universality with respect to spin-dependence is obtained in agreement with expectations.

hep-ph↗