N = 4 superparticle and super-Yang-Mills theory in USp (4) harmonic superspace

We study the N = 4 harmonic superparticle model, both with and without central charge and quantize it. Since the central charge breaks the U (4) R-symmetry group of the N = 4 superalgebra down to USp (4), we consider the superparticle dynamics in N = 4 harmonic superspace with USp (4) / (U (1) × U (1)) harmonic variables. We show that the quantization of a massive superparticle with central charge leads to a superfield realization of the N = 4 massive vector multiplet in N = 4 harmonic superspace. In the massless case without central charge the superparticle quantization reproduces three different multiplets: the N = 4 SYM multiplet, the N = 4 gravitino multiplet and N = 4 supergravity multiplet. The SYM multiplet is described by six analytic superfield strengths with different types of analyticity. We show that these strengths solve the N = 4 SYM constraints and can be used for the construction of actions in N = 4 harmonic superspace.