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Full-Text Articles in Physical Sciences and Mathematics
2-Loop Analysis Of Vector-Current Propagators In Chiral Perturbation-Theory, E Golowich, J Kambor
2-Loop Analysis Of Vector-Current Propagators In Chiral Perturbation-Theory, E Golowich, J Kambor
Physics Department Faculty Publication Series
We perform a calculation of the isospin and hypercharge vector-current propagators (ΔV33μν(q2) and ΔV88μν(q2)) to two loops in chiral perturbation theory. The analysis is carried out with straight-forward Feynman diagram methods by making appropriate use of external vector sources. Counterterms from the (q6) chiral lagrangian, required to absorb divergences and scale dependence encountered at the two-loop level, are constructed. Our final results are finite, covariant, and scale-independent. Several applications are described, including a comparison of the two-loop isospin vector spectral function with data and the construction of new chiral sum rules.
Chiral Perturbation Theory: A Primer, Br Holstein
Chiral Perturbation Theory: A Primer, Br Holstein
Physics Department Faculty Publication Series
Recently methods have been developed which exploit the chiral symmetry of QCD in order to make rigorous contact with low energy particle physics phenomenology. In these lectures we present a pedagogical introduction to these techniques.
A Status Report On Chiral Dynamics: Theory And Experiment, Aron M. Benstein, Barry Holstein
A Status Report On Chiral Dynamics: Theory And Experiment, Aron M. Benstein, Barry Holstein
Physics Department Faculty Publication Series
This paper gives an overview of a Workshop on Chiral Dynamics: Theory and Experiment which was held at MIT July 25-29, 1994; its unique feature was the equal mixture of theory and experiment. The purpose of the workshop was to bring together many of the active participants to assess the status of the field and to explore fruitful future directions. The foundations and present status of the theory were reviewed as well as the experimental status of the field. To facilitate the discussion of future directions working groups were organized on Threshold Photo/Electropion Production, Two-Pion Threshold and the Chiral Anomaly, …
Breaking Cosmic Strings Without Monopoles, D Eardley, G Horowitz, David Kastor, Jennie Traschen
Breaking Cosmic Strings Without Monopoles, D Eardley, G Horowitz, David Kastor, Jennie Traschen
Physics Department Faculty Publication Series
It is shown that topologically stable cosmic strings can, in fact, appear to end or to break, even in theories without monopoles. This can occur whenever the spatial topology of the universe is nontrivial. For the case of Abelian-Higgs strings, we describe the gauge and scalar field configurations necessary for a string to end on a black hole. We give a lower bound for the rate at which a cosmic string will break via black hole pair production, using an instanton calculation based on the Euclidean C-metric.
Calculation Of A Weak Nonleptonic Matrix Element Using “Weinberg” Sum Rules, John Donoghue
Calculation Of A Weak Nonleptonic Matrix Element Using “Weinberg” Sum Rules, John Donoghue
Physics Department Faculty Publication Series
There is a ``toy'' weak matrix element which can be expressed as an integral over the vector and axial vector spectral functions, $\rho_V (s) - \rho_A (s)$. I review our recent evaluation of these spectral functions, the study of four ``Weinberg'' sum rules and the calculation of this matrix element.
Nn, N-Delta Couplings And The Quark-Model, Tr Hemmert, Br Holstein, Nc Mukhopadhyay
Nn, N-Delta Couplings And The Quark-Model, Tr Hemmert, Br Holstein, Nc Mukhopadhyay
Physics Department Faculty Publication Series
We examine mass-corrected SU(6) symmetry predictions in the quark model relating vector, axial-vector, and strong NN and NΔ couplings, and demonstrate that the experimental NΔ value is significantly higher than predicted in each case. Nevertheless the Goldberger-Treiman relation is satisfied in both sectors. Possible origins of the discrepancy of the quark model predictions with experiments are discussed.
Two Comparative Case Studies Of B-Quark And C-Quark Physics: • Particle-Antiparticle Mixing • Radiative Weak Decays, Eugene Golowich
Two Comparative Case Studies Of B-Quark And C-Quark Physics: • Particle-Antiparticle Mixing • Radiative Weak Decays, Eugene Golowich
Physics Department Faculty Publication Series
We discuss prospects for detecting the two charm-related phenomena of $D^0$-${\bar D}^0$ mixing and weak radiative decays of $D$ mesons ({\it e.g.} $D\to K^* + \gamma$). A general update of particle-antiparticle mixing for the pseudoscalar mesons is presented and the dynamics of mixing is reviewed, with application especially to the $D^0$-${\bar D}^0$ system. The radiative weak decays of $B$ mesons is then considered, and the problem of hadronic uncertainties is reviewed. Finally, the technique of calculating radiative weak decays for charm mesons is explained.
Reanalysis Of The Decay-K-L-]Pi(0)E(+)E(-), Jf Donoghue, F Gabbiani
Reanalysis Of The Decay-K-L-]Pi(0)E(+)E(-), Jf Donoghue, F Gabbiani
Physics Department Faculty Publication Series
The decay KL→π0e+e- is searched for as a signal of direct ΔS=1 CP violation. We provide a thorough updating of the analysis of the three components of the decay: (1) direct CP violation, (2) CP violation through the mass matrix, and (3) CP-conserving (two photon) contributions. First the chiral calculation of the KS→π0e+e- rate, due to Ecker, Pich and, de Rafael, is updated to include recent results on the nonleptonic amplitude. Then we systematically explore the uncertainties in this method. These appear to be so large that they will obscure direct CP violation unless it is possible to measure the …
Radiative Weak Decays Of Charm Mesons, G Burdman, E Golowich, Jl Hewett, S Pakvasa
Radiative Weak Decays Of Charm Mesons, G Burdman, E Golowich, Jl Hewett, S Pakvasa
Physics Department Faculty Publication Series
We address standard model predictions for flavor-changing radiative transitions of the pseudoscalar charm mesons. Short-distance contributions in D radiative transitions are contrasted with those in B decays. A full analysis is presented of the c→u+γ electromagnetic penguin amplitude with QCD radiative corrections included. Given the importance of long-range effects for the charm sector, special attention is paid to such contributions as the vector dominance and pole amplitudes. A number of two-body final states in exclusive charm radiative decays is considered and the corresponding branching ratio predictions are given.
Dispersion Relations And Effective Field Theory, John Donoghue
Dispersion Relations And Effective Field Theory, John Donoghue
Physics Department Faculty Publication Series
The techniques of dispersion relations match very well with those of effective field theory. I describe the techniques for using dispersion relations effectively, and give some pedagogical examples to illustrate the range of applications.
On The Marriage Of Chiral Perturbation Theory And Dispersion Relations, John Donoghue
On The Marriage Of Chiral Perturbation Theory And Dispersion Relations, John Donoghue
Physics Department Faculty Publication Series
I describe the methodology for the use of dispersion relations in connection with chiral perturbation theory. The conditions for matching the two formalisms are given at $O(E^2)$ and $O(E^4)$. The two have several complementary features, as well as some limitations, and these are described by the use of examples, which include chiral sum rules related to the Weinberg sum rules, form factors, and a more complicated reaction, $\gamma \gamma \rightarrow \pi \pi$.