A search for the fourth standard model family at lepton colliders

A SEARCH FOR THE FOURTH STANDARD MODEL FAMILY ATLEPTON COLLIDERS(Ph. D. Thesis)Rena ÇIFTÇIGAZI UNIVERSITYINSTITUTE OF SCIENCE AND TECHNOLOGYJuly 2006ABSTRACTIn this study, the existence of the fourth standard model family has beenresearched in the framework of DMM (Democratic Mass Matrix) approach andmass limits for the fourth family fermions are given. In addition, CKM(Cabibbo Kabayashi Maskawa) matrix corresponding mixings of the fourthstandard model family with the first three family is obtained. Decay modes ofthe fourth family fermions are investigated. It is shown that necessary conditionfor the fourth family quarks to form quarkonia can be provided. All possibledecay modes of η4 (1S0) and ψ 4 (3S1) quarkonia are investigated. In future, thefourth standard model family fermions can be observed only in colliders withTeV energy scale. In this thesis, both pair production of fourth family fermionsand the production of their quarkonia in linear colliders are taken intoconsideration. The production cross sections and corresponding number ofevents per year are computed. According to obtained results, high energy leptoncolliders make possible to produce and observe fourth family fermions and theirquarkonia.Science Code : 202.1.149Key Word : Standard model, quark, quarkonia, collider, event numberPage Number : 125Adviser : Prof. Dr. Saleh SULTANSOY