{ital R}{sub {ital b}} and {ital R}{sub {ital c}} in the two-Higgs-doublet model with flavor-changing neutral currents
- Theory Group, Southeastern Universities Research Association, Continuous Electron Beam Accelerator Facility, Newport News, Virginia 23606 (United States)
- Physics Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)
A study of {ital R}{sub {ital b}} and {ital R}{sub {ital c}} is presented in the context of a two-Higgs-doublet model with flavor-changing scalar currents (FCSC{close_quote}s). Implications of the model for the {rho} parameter and for {ital b}{r_arrow}{ital s}{gamma} are also considered. The experimental data on {ital R}{sub {ital b}} places stringent constraints on the model parameters that are difficult to reconcile with the constraints from {ital b}{r_arrow}{ital s}{gamma} and {rho}. If we treat the couplings of the model as purely phenomenological, then the model can still survive albeit in a rather narrow region of the parameter space. Noting that aspects of the experimental analysis for {ital R}{sub {ital b}} and {ital R}{sub {ital c}} may be of some concern, we also disregard {ital R}{sub {ital b}}{sup expt} and {ital R}{sub {ital c}}{sup expt} and give predictions for these using constraints from {ital b}{r_arrow}{ital s}{gamma} and the {rho} parameter only. We emphasize the theoretical and experimental advantages of the observable {ital R}{sub {ital b}+{ital c}}{equivalent_to}{Gamma}({ital Z}{r_arrow}{ital b{bar b}}or{ital c{bar c}})/{Gamma}({ital Z}{r_arrow}hadrons). We also stress the role of {ital R}{sub {ital l}}{equivalent_to}{Gamma}({ital Z}{r_arrow}hadrons)/{Gamma}({ital Z}{r_arrow}{ital l}{sup +}{ital l}{sup {minus}}) in testing the standard model despite its dependence on QCD corrections. Noting that in models with FCNC{close_quote}s the amplitude for {ital Z}{r_arrow}{ital c{bar c}} receives a contribution which grows with {ital m}{sup 2}{sub {ital t}} the importance and uniqueness of precision {ital Z}{r_arrow}{ital c{bar c}} measurements for constraining flavor-changing {ital t{bar c}} currents is underscored. {copyright} {ital 1996 The American Physical Society.}
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- DOE Contract Number:
- AC02-76CH00016; AC05-84ER40150
- OSTI ID:
- 383543
- Journal Information:
- Physical Review, D, Vol. 54, Issue 5; Other Information: PBD: Sep 1996
- Country of Publication:
- United States
- Language:
- English
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