  Forming planetesimals from pebbles is a major challenge in our current
understanding of planet formation. In a protoplanetary disk, pebbles drift
inward near the disk midplane via gas drag and they may enter a dead zone. In
this context, we identified that the backreaction of the drag of pebbles onto
the gas could lead to a runaway pile-up of pebbles, the so-called no-drift
mechanism. We improve upon the previous study of the no-drift mechanism by
investigating the nature and characteristics of the resultant planetesimal
belt. We performed 1D diffusion-advection simulations of drifting pebbles in
the outer region of a dead zone by including the backreaction to the radial
drift of pebbles and including planetesimal formation via the streaming
instability. We considered the parameters that regulate gas accretion and
vertical stirring of pebbles in the disk midplane. In this study, the
pebble-to-gas mass flux ($F_{\rm p/g}$) was fixed as a parameter. We find that
planetesimals initially form within a narrow ring whose width expands as
accumulating pebbles radially diffuse over time. The system finally reaches a
steady-state where the width of the planetesimal belt no longer changes. A
non-negligible total mass of planetesimals (more than one Earth mass) is formed
for a disk having $F_{\rm p/g} \gtrsim 0.1$ for more than $\sim 10-100$ kyr
with nominal parameters: a gas mass flux of $\gtrsim10^{-8} {\rm M}_\oplus$/yr,
$\tau_{\rm s} \simeq 0.01-0.1$, $\alpha_{\rm mid} \lesssim 10^{-4}$, and
$\alpha_{\rm acc} \simeq 10^{-3}-10^{-2}$ at $r \lesssim 10$ au, where $r$,
$\tau_{\rm s}$, $\alpha_{\rm mid}$, and $\alpha_{\rm acc}$ are the heliocentric
distance, the Stokes number, and the parameters in a dead zone controlling the
efficiencies of vertical turbulent diffusion of pebbles (i.e., scale height of
pebbles) and gas accretion of the $\alpha$-disk (i.e., gas surface density),
respectively.
