NMSPEC: A Fortran code for the sparticle and Higgs masses in the NMSSM with GUT scale boundary conditions

Abstract : NMSPEC is a Fortran code that computes the sparticle and Higgs masses, as well as Higgs decay widths and couplings in the NMSSM, with soft SUSY breaking terms specified at MGUT. Exceptions are the soft singlet mass m_s^2 and the singlet self coupling kappa, that are both determined in terms of the other parameters through the minimization equations of the Higgs potential. We present a first analysis of the NMSSM parameter space with universal SUSY breaking terms at MGUT -- except for m_s and A_kappa -- that passes present experimental constraints on sparticle and Higgs masses. We discuss in some detail a region in parameter space where a SM-like Higgs boson decays dominantly into two CP odd singlet-like Higgs states.