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Volume 334 - The 36th Annual International Symposium on Lattice Field Theory (LATTICE2018) - Weak Decays and Matrix Elements
D meson semileptonic decay form factors at $q^2 = 0$
R. Li,* A. Bazavov, C. DeTar, C.W. Bernard, D. Du, A.X. El-Khadra, E. Gámiz, S. Gottlieb, U.M. Heller, J. Komijani, A.S. Kronfeld, L. J. Laiho, P.B. Mackenzie, E.T. Neil, T. Primer, J.N. Simone, R.L. Sugar, D. Toussaint, R.S. Van de Water, R. Zhou on behalf of Fermilab Lattice and MILC Collaborations
*corresponding author
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Published on: 2019 May 29
We discuss preliminary results for the vector form factors $f_+^{\{\pi,K\}}$ at zero-momentum transfer for the decays $D\to\pi\ell\nu$ and $D\to K \ell\nu$ using MILC's $N_f = 2+1+1$ HISQ ensembles at four lattice spacings, $a \approx 0.042, 0.06, 0.09$, and 0.12 fm, and various HISQ quark masses down to the (degenerate) physical light quark mass. We use the kinematic constraint $f_+(q^2)= f_0(q^2)$ at $q^2 = 0$ to determine the vector form factor from our study of the scalar current, which yields $f_0(0)$.
Results are extrapolated to the continuum physical point in the framework of hard pion/kaon SU(3) heavy-meson-staggered $\chi$PT and Symanzik effective theory. Our calculation improves upon the precision achieved in existing lattice-QCD calculations of the vector form factors at $q^2=0$. We show the values of the CKM matrix elements $|V_{cs}|$ and $|V_{cd}|$ that we would obtain using our preliminary results for the form factors together with recent experimental results, and discuss the implications of these values for the second row CKM unitarity.
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