D To Axial Vector Meson Transition Form Factors With Applications To Relevant Semileptonic Decays

The weak decays of hadrons are very useful for us to test the standard model of particle physics（SM）,determine its basic parameters and search possible new physics.For the decays with only S-wave mesons（the pseudoscalar mesons,vector mesons,etc.）in the final states,many studies have been conducted both from theoretical and experimental aspects.However,the studies on decays involving P-wave meson（scalar meson,axial vector meson）in the final states are relatively less.In the last ten years,with the development of experiments,a large amount of decays with P-wave mesons in the final states have been found and measured,which promote the theoretical investigations on these decays.In this thesis,we calculate the D to axial vector meson transition form factors by using the QCD sum rules and apply the results to relevant semileptoinc decays.In the first part,we give an overview of the standard model,QCD sum rules and the physical properties of even parity mesons.To be specific,in chapter 1,we sketches the limitations of the standard model of particle physics and the methods used for solving these limitations;then we give an introduction to the basic framework of the standard model,including the QCD theory and electroweak theory in chapter 2;chapter 3 is devoted to illustrating the QCD sum rules detailly,including correlation function of quark current,unitary relation and derivation of QCD sum rules and so on;in chapter 4,we introduce the physical properties of even parity mesons,i.e.the scalar,axial vector and tensor mesons.On this basis,in the second part,i.e chapter 5,we calculate the D to axial vector meson a1（1260）,f₁（1285）,f₁（1420）transition form factors.In the calculations,we consider the flavor contents of every mesons in detail and the mixing between f（1285）and f（1420）.The uncertainties of transition form factors come from the four free parameters s0,S0’,M12,M22 which is about（15-20）%for f₁,f₀,fV and 30%for f₂.Based on the form factors obtained here,the branching ratios for relevant semileptonic decays are calculated.It is found that the branching ratios for D→a10（1260）l+ v、D0→a1-（1260）l+v、D⁺→f₁（1285）l+ v are at the order of O（10-5）,while the one for D⁺→f₁（1420）l+v is approximately two order of magnitude smaller.