Kaon semileptonic decay form factors with HISQ valence quarks

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We report on the status of our kaon semileptonic form factor calculations using the highly-improved staggered quark (HISQ) formulation to simulate the valence fermions.

• We present results for the form factor f_+^{K \pi}(0) on the asqtad N_f=2+1 MILC configurations, discuss the chiral-continuum extrapolation, and give a preliminary estimate of the total error.
• We also present a more preliminary set of results for the same form factor but with the sea quarks also simulated with the HISQ action; these results include data at the physical light quark masses.
• The improvements that we expect to achieve with the use of the HISQ configurations and simulations at the physical quark masses are briefly discussed.