Abstract
he quark flavor sector of the Standard Model is a fertile ground to look for new physics effects through a unitarity test of the Cabbibo-Kobayashi-Maskawa (CKM) matrix. We present a lattice QCD calculation of the scalar and the vector form factors (over a large q2 region including q2 = 0) associated with the D→ Klv semi-leptonic decay. This calculation will then allow us to determine the central CKM matrix element, Vcs in the Standard Model, by comparing the lattice QCD results for the form factors and the experimental decay rate. This form factor calculation has been performed on the Nf = 2 + 1 + 1 MILC HISQ ensembles with the physical light quark masses.
Highlights
IntroductionThe flavour changing weak interactions between quarks via emission of W bosons can be parametrised in terms of the Cabbibo-Kobayashi-Maskawa (CKM) unitary matrix in the Standard Model given by [1, 2]
The flavour changing weak interactions between quarks via emission of W bosons can be parametrised in terms of the Cabbibo-Kobayashi-Maskawa (CKM) unitary matrix in the Standard Model given by [1, 2]VCKM = VVVuctddd Vus Vcs Vts VVVuctbbb . (1)Precise and independent determination of each of the CKM matrix elements is crucial to test the Standard Model stringently and any deviation from unitarity would signal the existence of physics beyond the Standard Model.The uncertainties in the unitarity checks of the second row and second column of the CKM matrix are dominated by that of |Vcs|, the central CKM matrix element
This calculation will allow us to determine the central CKM matrix element, Vcs in the Standard Model, by comparing the lattice QCD results for the form factors and the experimental decay rate. This form factor calculation has been performed on the N f = 2 + 1 + 1 MILC highly improved staggered quark (HISQ) ensembles with the physical light quark masses
Summary
The flavour changing weak interactions between quarks via emission of W bosons can be parametrised in terms of the Cabbibo-Kobayashi-Maskawa (CKM) unitary matrix in the Standard Model given by [1, 2]. The uncertainties in the unitarity checks of the second row and second column of the CKM matrix are dominated by that of |Vcs|, the central CKM matrix element. This element is calculated from the studies of the leptonic and semileptonic meson decays involving charged flavour changing current from c to s by combining the experimental decay rate with the vector form factor calculated from lattice QCD [1, 2]. We present a calculation of the semileptonic D → Klν decay on the N f = 2 + 1 + 1 lattices generated by MILC using highly improved staggered quark (HISQ) formalism [7], which is an improvement over HPQCD’s previous work reported in [8, 9]. A similar study [11] has been recently done using twisted mass fermions
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