  We study the flux tube thickness in the confining phase of the (2+1)d SU(2)
Lattice Gauge Theory near the deconfining phase transition. Following the
Svetitsky-Yaffe conjecture, we map the problem to the study of the <epsilon
sigma sigma> correlation function in the two-dimensional spin model with Z_2
global symmetry, (i.e. the 2d Ising model) in the high-temperature phase. Using
the form factor approach we obtain an explicit expression for this function and
from it we infer the behaviour of the flux density of the original (2+1)d LGT.
Remarkably enough the result we obtain for the flux tube thickness agrees (a
part from an overall normalization) with the effective string prediction for
the same quantity.
