arXiv subjects

Eugene Golowich

Publications and source records attributed to Eugene Golowich.

33 records · Page 2Linked to original sources

arXiv1998

Can Nearby Resonances Enhance D^0 - anti-D^0 Mixing?

We consider the possibility that D^0 - anti-D^0 mixing undergoes resonant enhancement. Various scenarios are explored, including the potential effects of nearby pseudoscalar or scalar quark-antiquark (Q - anti-Q) resonances as well as of hybrid quark-antiquark-gluon Q - anti-Q G states. Assuming reasonable values for the resonance parameters we find relatively sizeable contributions from individual resonances to both Δm_D and ΔΓ_D. We derive a variant of the GIM cancellation mechanism for the resonance amplitudes and show that broken SU(3) can allow for sizeable residual effects. Additional input from meson spectroscopy and lattice gauge simulations will be needed to improve the accuracy of these predictions.

hep-ph↗

arXiv1997

The DMO Sum Rule Revisited

We reconsider the DMO sum rule in light of our recent two-loop calculations of isospin and hypercharge vector and axialvector current propagators in chiral perturbation theory. A modified derivation valid to second order in the light quark masses is presented, and a phenomenological analysis yields determination of a combination of finite counterterms occurring in the p^4 and p^6 chiral lagrangians. Suggestions are given for further study.

hep-ph↗

arXiv1997

Two-loop Analysis of Axialvector Current Propagators in Chiral Perturbation Theory

We perform a calculation of the isospin and hypercharge axialvector current propagators to two loops in SU(3)xSU(3) chiral perturbation theory. A large number of order p^6 divergent counterterms are fixed, and complete two-loop renormalized expressions for the pion and eta masses and decay constants are given. The calculated isospin and hypercharge axialvector polarization functions are used as input in new chiral sum rules, valid to second order in the light quark masses. Some phenomenological implications of these sum rules are considered.

hep-ph↗

arXiv1997

Chiral sum rules to second order in quark mass

A new calculation of the isospin and hypercharge axialvector current propagators ($Δ_{A33}^{μν}(q^2)$ and $Δ_{A88}^{μν}(q^2)$) to two loops in SU(3) x SU(3) chiral perturbation theory is used to derive chiral spectral function sum rules valid to second order in the light quark masses. Explicit forms are given for the three-pion isospin axialvector spectral functions at low energy and application of the sum rules to the determination of counterterms of the chiral lagrangian is discussed.

hep-ph↗

arXiv1997

Some Possibilities for Charm Studies at B-factories

To provide focus to my review of charm theory at the B-Physics and CP-Violation conference, I consider theoretical issues related to possible charm studies at B-factories. A few topics of interest to the author are stressed -- rare decays, CP-violating asymmetries and ${\bar D}^0 - D^0$ mixing.

hep-ph↗

arXiv1997

Charm Physics 1996 - A Retrospective

A pedagogically oriented review is given of progress made over the past year in our understanding of physics related to the charm quark. Included are discussions of the R_c deficit, the ψ' anomaly, charm spectroscopy, D nonleptonic decays, searches for flavor-changing neutral currents, new limits on D^0 - {\bar D}^0 mixing and prospects for future experimental studies of the charm sector.

hep-ph↗

arXiv1996

Final state rescattering as a contribution to $B \to ργ$

We provide a new estimate of the long-distance component to the radiative transition $B \to ργ$. Our mechanism involves the soft-scattering of on-shell hadronic products of nonleptonic $B$ decay, as in the chain $B \to ρρ\to ργ$. We employ a phenomenological fit to scattering data to estimate the effect. The specific intermediate states considered here modify the $B \to ργ$ decay rate at roughly the $5 \to 8%$ level, although the underlying effect has the potential to be larger. Contrary to other mechanisms of long distance physics which have been discussed in the literature, this yields a non-negligible modification of the $B^0 \to ρ^0 γ$ channel and hence will provide an uncertainty in the extraction of $V_{td}$. This mechanism also affects the isospin relation between the rates for $B^- \to ρ^-γ$ and $B^0 \to ρ^0 γ$ and may generate CP asymmetries at experimentally observable levels.

hep-ph↗

arXiv1996

Systematics of soft final state interactions in $B$ decay

By using very general and well established features of soft strong interactions we show, contrary to conventional expectations, that (i) soft final state interactions (FSI) do not disappear for large $m_B$, (ii) inelastic rescattering is expected to be the main source of soft FSI phases, and (iii) flavor off-diagonal FSI are suppressed by a power of $m_B$, but are quite likely to be significant at $m_B\simeq 5$~GeV. We briefly discuss the influence of these interactions on tests of CP-violation and on theoretical calculations of weak decays.

hep-ph↗

arXiv1995

Inverse-Moment Chiral Sum Rules

A general class of inverse-moment sum rules was previously derived by the authors in a chiral perturbation theory (ChPT) study at two-loop order of the isospin and hypercharge vector-current propagators. Here, we address the evaluation of the inverse-moment sum rules in terms of existing data and theoretical constraints. Two kinds of sum rules are seen to occur, those which contain as-yet undetermined ${\cal O}(q^6)$ counterterms and those free of such quantities. We use the former to obtain phenomenological evaluations of two ${\cal O}(q^6)$ counterterms. Light is shed on the important but difficult issue regarding contributions of higher orders in the ChPT expansion.

hep-ph↗

arXiv1995

Two Comparative Case Studies of $b$-quark and $c$-quark Physics

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.} $D\to K^* + γ$). 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.

hep-ph↗

arXiv1995

Two-Loop Analysis of Vector Current Propagators in Chiral Perturbation Theory

We perform a calculation of the isospin and hypercharge vector current propagators ($Δ_{V33}^{μν}(q^2)$ and $Δ_{V88}^{μν}(q^2)$) to two loops in chiral perturbation theory. The analysis is carried out with straightforward Feynman diagram methods by making appropriate use of external vector sources. Counterterms from the ${\cal O}(q^6)$ 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.

hep-ph↗

arXiv1995

Radiative Weak Decays of Charm Mesons

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 $c\to u+γ$ 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.

hep-ph↗

arXiv1994

Uncertainties from Long Range Effects in $B \to K^* γ

We reconsider the `long-range' component of the radiative transition $B \to K^* γ$. A careful analysis of the vector dominance amplitude $B \to V_1 V_2 \to V_1 γ$ is carried out, with emphasis on the role of gauge invariance. The procedure for incorporating phenomenological $B\to V_1 V_2$ data is identified and polarization data, only recently available, is employed to estimate the magnitude of the vector dominance effect. We summarize uncertainties in the $B\to K^*γ$ radiative transition produced by long-range effects and provide sugggestions for further experimental work.

hep-ph↗

arXiv1993

Anatomy of a Weak Matrix Element

Although the weak nonleptonic amplitudes of the Standard Model are notoriously difficult to calculate, we have produced a modified weak matrix element which can be analyzed using reliable methods. This hypothetical nonleptonic matrix element is expressible in terms of the isovector vector and axialvector spectral functions $ρ_{\rm V}(s)$ and $ρ_{\rm A}(s)$, which can be determined in terms of data from tau lepton decay and $e^+ e^-$ annihilation. Chiral symmetry and the operator product expansion are used to constrain the spectral functions respectively in the low energy and the high energy limits. The magnitude of the matrix element thus determined is compared with its `vacuum saturation' estimate, and in the future may be accessible with lattice calculations.

hep-ph↗

arXiv1993

Chiral Sum Rules and Their Phenomenology

We present an analysis of four sum rules, each based on chiral symmetry and containing the difference $ρ_{\rm V}(s) - ρ_{\rm A}(s)$ of isovector vector and axialvector spectral functions. Experimental data from tau lepton decay and electron-positron scattering identify the spectral functions over a limited kinematic domain. We summarize the status of the existing database. However, a successful determination of the sum rules requires additional content, in the form of theoretical input. We show how chiral symmetry and the operator product expansion can be used to constrain the spectral functions in the low energy and the high energy limits and proceed to perform a phenomenological test of the sum rules.

hep-ph↗