Decoupling or nondecoupling: Is that the Rb question?
نویسندگان
چکیده
The top quark is well known for the nondecoupling e ects it implies in and Rb. The recent experimental Rb data exhibits a disagreement with the SM prediction at more than the 3 level. It is tempting to explore whether this might be due to nondecoupling New Physics e ect, opposite to those of the top. We investigate this issue in the context of models with an extra family of right or left handed, singlet or doublet quarks. It is shown that, contrary to what one might naively expect, the nondecoupling properties of a mirror t0 do not have an impact on Rb, due to a conspiracy of the mixing angles, imposed by the requirement that there be no b b0 mixing. Our analysis disagrees with an analysis performed independently, for that has ignored the charged current couplings with right-handed nontrivial multiplets. They are needed in order to extract the correct physical decoupling properties.
منابع مشابه
ar X iv : h ep - p h / 96 03 22 1 v 1 4 M ar 1 99 6 Decoupling or nondecoupling : is that the R b question ?
The top quark is well known for the nondecoupling effects it implies in ρ and Rb. The recent experimental Rb data exhibits a disagreement with the SM prediction at more than the 3σ level. It is tempting to explore whether this might be due to nondecoupling New Physics effect, opposite to those of the top. We investigate this issue in the context of models with an extra family of right or left h...
متن کاملar X iv : h ep - p h / 96 03 22 1 v 2 1 4 M ar 1 99 6 Decoupling or nondecoupling : is that the R b question ? D . Comelli a and João
The top quark is well known for the nondecoupling effects it implies in ρ and Rb. The recent experimental Rb data exhibits a disagreement with the SM prediction at more than the 3σ level. It is tempting to explore whether this might be due to nondecoupling New Physics effects, opposite to those of the top. We investigate this issue in the context of models with an extra family of right or left ...
متن کاملTree-Level Nondecoupling and the Supersymmetric Higgs Sector
Because of the existence of cubic scalar couplings, there are in general nondecoupling effects at tree level in the scalar sector of any theory with two or more very different mass scales. We show this explicitly in the minimal nonsupersymmetric SU(5) model of grand unification. We show also how tree-level decoupling is guaranteed if supersymmetry is imposed. On the other hand, if the gauge sym...
متن کاملOptimal characteristics determination of engine mounting system using TRA mode decoupling with emphasis on frequency responses
It is possible to improve vehicle vibration by tuning the parameters of engine mounting system. By optimization of mount characteristics or finding the optimal position of mounts, vibration of the engine and transmitted force from the engine to the chassis can be reduced. This paper examines the optimization of 6-degree-of-freedom engine mounting system based on torque roll axis (TRA) mode deco...
متن کاملNondecoupling of maximal supergravity from the superstring.
We consider the conditions necessary for obtaining perturbative maximal supergravity in d dimensions as a decoupling limit of type II superstring theory compactified on a (10-d) torus. For dimensions d=2 and d=3, it is possible to define a limit in which the only finite-mass states are the 256 massless states of maximal supergravity. However, in dimensions d>or=4, there are infinite towers of a...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Physical review. D, Particles and fields
دوره 54 1 شماره
صفحات -
تاریخ انتشار 1996