  We report the discovery of a multiply lensed Ly Alpha (Lya) emitter at z =
3.90 behind the massive galaxy cluster WARPS J1415.1+3612 at z = 1.026. Images
taken by the Hubble Space Telescope(HST) using ACS reveal a complex lensing
system that produces a prominent, highly magnified arc and a triplet of smaller
arcs grouped tightly around a spectroscopically confirmed cluster member.
Spectroscopic observations using FOCAS on Subaru confirm strong Lya emission in
the source galaxy and provide redshifts for more than 21 cluster members, from
which we obtain a velocity dispersion of 807+/-185 km/s. Assuming a singular
isothermal sphere profile, the mass within the Einstein ring (7.13+/-0.38")
corresponds to a central velocity dispersion of 686+15-19 km/s for the cluster,
consistent with the value estimated from cluster member redshifts. Our mass
profile estimate from combining strong lensing and dynamical analyses is in
good agreement with both X-ray and weak lensing results.
