Donoghue, John

Job Title

Distinguished Professor, Department of Physics, College of Natural Sciences

Last Name

Donoghue

First Name

John

Discipline

Physics

Introduction

I am a professor of physics at the University of Massachusetts at Amherst.
My research area is theoretical particle physics.

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Now showing 1 - 10 of 172

Open Access
Comments on the Minimal Vectorial Standard Model
(2009-01) Anber, Mohamed M.; Aydemir, Ufuk; Donoghue, John; Pais, Preema
We explore the available parameter space of the minimal vectorial Standard Model. In this theory, the gauge currents are initially vectorial but the Higgs sector produces chiral mass eigenstates, leading to a set of heavy right-handed mirror particles. We describe the phenomenology of the residual parameter space and suggest that the model will be readily tested at the LHC.
Open Access
Random values of the physical parameters
(2001-01) Donoghue, JF
I briefly describe two motivations, two mechanisms and two possible tests of the hypothesis that the physical parameters of the ground state of a theory can vary in different rerions of the universe.
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THE HARMONIC-OSCILLATOR VIA FUNCTIONAL TECHNIQUES
(1988) Donoghue, JF; Holstein, BR
Although functional methods are common in the research literature, they are not generally seen by students until a course in field theory. Nevertheless, it is straightforward and pedagogically useful to treat a familiar problem—the harmonic oscillator—via such techniques, as shown in the present work.
Open Access
Quark and lepton masses and mixing in the landscape
(2006-01) Donoghue, JF; Dutta, K; Ross, A
Even if quark and lepton masses are not uniquely predicted by the fundamental theory, as may be the case in the string theory landscape, nevertheless their pattern may reveal features of the underlying theory. We use statistical techniques to show that the observed masses appear to be representative of a scale-invariant distribution, ρ(m)∼1/m. If we extend this distribution to include all the Yukawa couplings, we show that the resulting Cabibbo-Kobayashi-Maskawa matrix elements typically show a hierarchical pattern similar to observations. The Jarlskog invariant measuring the amount of CP violation is also well reproduced in magnitude. We also apply this framework to neutrinos using the seesaw mechanism. The neutrino results are ambiguous, with the observed pattern being statistically allowed even though the framework does not provide a natural explanation for the observed two large mixing angles. Our framework highly favors a normal hierarchy of neutrino masses. We also are able to make statistical predictions in the neutrino sector when we specialize to situations consistent with the known mass differences and two large mixing angles. Within our framework, we show that with 95% confidence the presently unmeasured Maki-Nakagawa-Sakata mixing angle sin⁡θ13 is larger than 0.04 and typically of order 0.1. The leptonic Jarlskog invariant is found to be typically of order 10-2 and the magnitude of the effective Majorana mass mee is typically of order 0.001 eV.
Open Access
New insights concerning dimension eight effects in weak decays
(2001-01) Donoghue, JF
Most past work on weak nonleptonic decays has mixed dimensional regularization in the weak operator product expansion with some form of a cutoff regularization in the evaluation of the matrix elements. Even with the usual technique of matching the two schemes, this combination misses physics at short distance which can be described by dimension eight (and higher dimension) operators. I describe some recent work with V. Cirigliano and E. Golowich which clarifies these effects and provides a numerical estimate suggesting that they are important.
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KAON DECAYS AND A DETERMINATION OF THE SCALE OF CHIRAL SYMMETRY
(1984) Donoghue, JF; Golowich, Eugene; Holstein, BR
Using effective chiral Lagrangians, we consider the occurrence of quadratic terms in the ΔI=1/2 K→3π matrix element. The inclusion of higher-derivative Lagrangians leads to a significant improvement over the usual current-algebra analysis. This allows an extraction directly from experimental data of Λχ, a measure of the scale of chiral symmetry. We give an operational definition of the chiral scale, and find Λχ≈1 GeV. The issue of uncertainty in the phenomenological determination of the B parameter is clarified.
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DISPERSIVE CONTRIBUTIONS TO K0-KBAR0 MIXING AND CP VIOLATION
(1984) Donoghue, JF; Holstein, BR
We consider the role of dispersive contributions in the analysis of the KL-KS system. These long-distance pieces can be present in both the real and imaginary parts of the mixing element M12. We provide an estimate of one such effect in Im M12, the η′ pole, which turns out to be potentially significant. These terms can substantially modify phenomenological studies, as we demonstrate for several cases. Improved experimental bounds on ε′/ε can provide a strong limit on dispersive effects in Im M12, and may in the near future remove the uncertainties caused by these contributions.
Open Access
SU(3) baryon chiral perturbation theory and long distance regularization
(1999) Donoghue, JF; Holstein, BR; Borasoy, B
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.
Open Access
Long distance chiral corrections in beta meson amplitudes
(2004-01) Sanz-Cillero, JJ; Donoghue, JF; Ross, A
We discuss the chiral corrections to fB and BB with particular emphasis on determining the portion of the correction that arises from long distance physics. For very small pion and kaon masses all of the usual corrections are truly long distance, while for larger masses the long distance portion decreases. These chiral corrections have been used to extrapolate lattice calculations towards the physical region of lighter masses. We show in particular that the chiral extrapolation is better behaved if only the long distance portion of the correction is used. We also display the long distance portions of the infrared enhanced chiral logarithms that appear in partially quenched chiral perturbation theory.
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ELECTROMAGNETIC DECAY OF GLUEBALLS
(1984) Donoghue, JF
The magnetic dipole radiative decay of a JPC=0-+ glueball is considered within the MIT bag model. The resultant width, due to gluonic coupling to quarks, is sizable. In addition to η-η′-glueball mixing, other contributions are found to be significant. We comment that, for magnetic dipole transitions, the radiative widths of glueballs can be expected to be larger than those of radially excited QQ̅ mesons, due to wave-function-orthogonality effects in the latter case.