相关论文: Bounding CKM Mixing with a Fourth Family
We perform an exploratory study of the allowed parameter range for the CKM-like mixing of hypothetical quarks of a fourth generation. As experimental constraints we use the tree-level determinations of the 3 $\times$ 3 CKM elements and FCNC…
Limits on the Higgs boson mass restrict CKM mixing of a possible fourth family beyond the constraints previously obtained from precision electroweak data alone. Existing experimental and theoretical bounds on the Higgs mass already…
We investigate the experimentally allowed parameter space of an extension of the standard model (SM3) by one additional family of fermions. Therefore we extend our previous study of the CKM like mixing constraints of a fourth generation of…
New dynamical mechanism of quark mass generations and mixing is demonstrated in the examples of three and four generations. In the framework of the new mixing pattern, called the coherent mixing, the CKM elements are predicted compatible…
While a chiral fourth generation of quarks is almost ruled out from the data on Higgs boson production and decay at the Large Hadron Collider, vector-like quarks are still a feasible option to extend the fermionic sector of the Standard…
In the scenario with four quark generations, we perform a fit using flavor-physics data and determine the allowed values -- preferred central values and errors -- of all of the elements of the 4X4 quark mixing matrix. In addition to the…
The structure of the mixing matrix, in the electroweak quark sector with four generations of quarks is investigated. We conclude that the area of the unitarity quadrangle is not a good choice as a possible measure of the CP~violation. In…
A simple breaking of the subnuclear democracy of the quarks leads to a mixing between the second and the third family, in agrement with observation. Introducing the mixing between the first and the second family, one finds an interesting…
We consider a direct approach to quark mixing based on the discrete family symmetry Delta (6N^2) in which the Cabibbo angle is determined by a residual Z_2 times Z_2 subgroup to be $|V_{us}|=0.222521$, for $N$ being a multiple of 7. We…
A simple breaking of the subnuclear democracy among the quarks leads to a mixing between the second and the third family, in agreement with observation. Introducing the mixing between the first and the second family, one finds an…
The structure of the Cabibbo-Kobayashi-Maskawa (CKM) matrix is analyzed from the standpoint of a composite model. A model is constructed with three families of quarks, by taking tensor products of sufficient numbers of spin-1/2…
A simple breaking of the subnuclear democracy of the quarks leads to a mixing between the secons and the third family, in agreement with observation. Introducing the mixing between the first and the second family, one finds an interesting…
In the Standard Model of elementary particles, quark-mixing is expressed in terms of a 3 x 3 unitary matrix V, the so called Cabibbo-Kobayashi-Maskawa (CKM) matrix. Significant unitarity checks are so far possible for the first row of this…
A phenomenological theory of fermion masses and mixings is constructed within the framework of a four- family symmetry. It is found that the most favored set of relevant CKM elements are $|V_{us}|\approx 0.222$, $|V_{cb}|\approx 0.044$,…
Results are presented from a search for a fourth generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in 2011. A novel…
We present a reanalysis of CDF data to extend limits on individual fourth-generation quark masses from particular flavor-mixing rates to the entire space of possible mixing values. Measurements from CDF have set individual limits on masses,…
We perform a bottom-up search for discrete non-Abelian symmetries capable of quantizing the Cabibbo angle that parameterizes CKM mixing. Given a particular Abelian symmetry structure in the up and down sectors, we construct representations…
We argue why vector-like quarks are usually expected to mix predominantly with the third generation, and discuss about the expected size of this mixing and its naturalness.
We show that a fourth family of quarks with $m_{t'}$ in the range of (400 - 600) GeV provides a rather simple explanation for the several indications of new physics that have been observed involving CP asymmetries of the b-quark. The…
A composite model of fermions is proposed to explain the "anomaly" in $Z \rightarrow b {\bar b}$ and, to a lesser extent, in $Z \rightarrow c {\bar c}$. It contains a {\em nonsequential} fourth family whose mass of one member (the charge…