Study Of Electroweak Chiral Lagrangian From Strong Dynamical Models

So far the postulated Higgs particle of the standard model has not been observed in experiments.We do not know what the electroweak symmetry breaking mechanism in nature is.The electroweak chiral Lagrangian is a general and economic low energy description for electroweak symmetry breaking patterns,especially for those strong dynamical electroweak symmetry breaking mechanisms.All the coefficients of the electroweak chiral Lagrangian,in principle,can be fixed by experiments.Due to the nonperturbative property of the possible strong dynamics,it is difficult to relate the measured coefficients of the electroweak chiral Lagrangian to underlying theories. Recently,the series of work of our group successfully produced the predictions for the coefficients of the chiral Lagrangian for pseudo scalar mesons from the first principle of QCD,which lights up the hope of building up the relationship between the coefficients of the electroweak chiral Lagrangian and underlying strong dynamical models.Along this line of thought,in this thesis we derive the electroweak chiral Lagrangian and build up the formulation of computing its coefficients from the minimal (one-doublet)technicolor model,the one-family technicolor,and a shematic topcolor-assisted technicolor model.We take the one-doublet and the one-family technicolor models as the prototypes to build up our formulation and as the trial models to test our formulation.The topcolor-assisted technicolor model is the main model we handle in this thesis.We find that the coefficients of the electroweak chiral Lagrangian from the topcolor-assisted technicolor model we consider are divided into three parts:the direct G_TC2interaction part,the contributions from the G_TC1and G_TC2induced effective Z' particle,and the contributions from ordinary fermions especially the top quark.The first two parts are computed in this thesis and we show that the direct G_TC2interaction part is the same as the results from the one-doublet technicolor model,while the contributions from the effective Z'particle is at least proportional to the p²-order coefficientβ₁ of the electroweak chiral Lagrangian,and one of the typical features of this topcolor-assisted technicolor we consider is that it only allows the T parameter vary in the range of 0～1/(25α).Besides the above main work of this thesis,we also do some other work related to the electroweak chiral Lagrangian,for instance we calculate the contributions to the oblique correction parameters S,T and U from heavy fermions and scalars in some generic representations of the electroweak gauge group.