  Background: Heavy-flavor production in p+p collisions tests
perturbative-quantum-chromodynamics (pQCD) calculations. Modification of
heavy-flavor production in heavy-ion collisions relative to binary-collision
scaling from p+p results, quantified with the nuclear-modification factor
(R_AA), provides information on both cold- and hot-nuclear-matter effects.
  Purpose: Determine transverse-momentum, pt, spectra and the corresponding
R_AA for muons from heavy-flavor mesons decay in p+p and Cu+Cu collisions at
sqrt(s_NN)=200 GeV and y=1.65.
  Method: Results are obtained using the semi-leptonic decay of heavy-flavor
mesons into negative muons. The PHENIX muon-arm spectrometers measure the p_T
spectra of inclusive muon candidates. Backgrounds, primarily due to light
hadrons, are determined with a Monte-Carlo calculation using a set of input
hadron distributions tuned to match measured-hadron distributions in the same
detector and statistically subtracted.
  Results: The charm-production cross section in p+p collisions at sqrt{s}=200
GeV, integrated over pt and in the rapidity range 1.4<y<1.9 is found to be
dsigma_ccbar/dy = 0.139 +/- 0.029 (stat) ^{+0.051}_{-0.058} (syst) mb. This
result is consistent with calculations and with expectations based on the
corresponding midrapidity charm-production cross section measured earlier by
PHENIX. The R_AA for heavy-flavor muons in Cu+Cu collisions is measured in
three centrality intervals for 1<pt<4 GeV/c. Suppression relative to
binary-collision scaling (R_AA<1) increases with centrality.
  Conclusions: Within experimental and theoretical uncertainties, the measured
heavy-flavor yield in p+p collisions is consistent with state-of-the-art pQCD
calculations. Suppression in central Cu+Cu collisions suggests the presence of
significant cold-nuclear-matter effects and final-state energy loss.
