Abstract
Transverse spectra of both jets and hadrons obtained in high-energy
$pp$ and $p\bar p $ collisions at central rapidity exhibit power-law
behavior of $1/p_T^n$ at high $p_T$. The power index $n$ is 4-5 for
jet production and is slightly greater for hadron production.
Furthermore, the hadron spectra spanning over 14 orders of magnitude
down to the lowest $p_T$ region in $pp$ collisions at LHC can be
adequately described by a single nonextensive statistical mechanical
distribution that is widely used in other branches of science. This
suggests indirectly the dominance of the hard-scattering process over
essentially the whole $p_T$ region at central rapidity in $pp$
collisions at LHC. We show here direct evidences of such a dominance
of the hard-scattering process by investigating the power index of UA1
jet spectra over an extended $p_T$ region and the two-particle
correlation data of the STAR and PHENIX Collaborations in high-energy
$pp$ and $p \bar p$ collisions at central rapidity. We then study how
the showering of the hard-scattering product partons alters the power
index of the hadron spectra and leads to a hadron distribution that
can be cast into a single-particle non-extensive statistical
mechanical distribution. Because of such a connection, the
non-extensive statistical mechanical distribution can be considered as
a lowest-order approximation of the hard-scattering of partons
followed by the subsequent process of parton showering that turns the
jets into hadrons, in high energy $pp$ and $p\bar p$ collisions.
