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Selected Works

1992

John Donoghue

Articles 1 - 6 of 6

Full-Text Articles in Physics

Light Quark Masses Beyond Leading Order, John Donoghue, Daniel Wyler Jan 1992

Light Quark Masses Beyond Leading Order, John Donoghue, Daniel Wyler

John Donoghue

We describe the measurement of the light quark mass ratios when one calculates to second order in the quark masses. At this order there is an ambiguity in the meaning of the quark mass, which afBicts the past attempts to provide a model-independent measurement of the ratios. We argue that this is similar to the regularization-scheme dependence of coupling constants. We study the anomalous Ward identities and the effects of strong CP violation in an attempt to resolve the ambiguity. The ambiguity persists even with singlet fields, such as the g', but can be resolved by observing the 9 dependence ...


Chiral Symmetry Tests In Nonleptonic K Decay, J. Kambor, John Donoghue, Barry Holstein, J. Missimer, D. Wyler Dec 1991

Chiral Symmetry Tests In Nonleptonic K Decay, J. Kambor, John Donoghue, Barry Holstein, J. Missimer, D. Wyler

John Donoghue

The existence of empirical tests for the validity of chiral perturbation theory in the analysis of nonleptonic kaon decay is pointed out in the context of K-> 2pi, 3pi processes. Comparison with existing data reveals good agreement with the chiral constraints. 


Components Of A Chiral Coefficient, John Donoghue, Barry Holstein Dec 1991

Components Of A Chiral Coefficient, John Donoghue, Barry Holstein

John Donoghue

One of the coefficients that parametrizes the chiral Lagrangian of QCD is expressible in terms of a sum rule for which the integrand is known from experiment. We confront two model calculations of this coeScient with the behavior of the data. The model related to vector dominance reproduces the sumrule behavior very well, whereas a one-loop chiral quark model calculation fails badly. The sum rule allows one to identify those ingredients which are needed to make the quark method more realistic. 


Mass Ratios Of Light Quarks, John Donoghue, Barry Holstein, Daniel Wyler Dec 1991

Mass Ratios Of Light Quarks, John Donoghue, Barry Holstein, Daniel Wyler

John Donoghue

We derive a consistent set of light quark mass ratios which are compatible with the available constraints of chiral symmetry treated to next-to-leading order. Also required as input is resonance saturation of a set of low-energy amplitudes, in particular for the pion and kaon electromagnetic mass difference. The results (mz +m„) /m, =1/15.5, (mz —m„)/m, =1/29 are modestly different from previous values, and resolve the long-standing puzzle of the g 3pi decay rate. 


Two Component Semileptonic Form Factors, Gustavo Burdman, John Donoghue Dec 1991

Two Component Semileptonic Form Factors, Gustavo Burdman, John Donoghue

John Donoghue

In the semileptonic decays of a heavy quark to a light quark, present models disagree in an essential fashion concerning the shape of the form factors. Both the heavy quark limit of QCD and dispersion relations suggest that the correct form factors contain two distinct contributions. We discuss these as applied to the B->piev and B->pev decays. We also describe the inconsistencies of available phenomenological models and discuss how they must be modified.


Union Of Chiral And Heavy Quark Symmetries, John Donoghue Dec 1991

Union Of Chiral And Heavy Quark Symmetries, John Donoghue

John Donoghue

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.