  The early stage of high multiplicity nuclear collisions is represented by a
nearly quarkless, hot, deconfined pure gluon plasma. This new scenario should
be characterized by a suppression of high $p_T$ photons and dileptons as well
as by reduced baryon to meson ratios. We present the numerical results for
central Pb+Pb collisions at the LHC energies by using the ideal Bjorken
hydrodynamics with time-dependent quark fugacity. It is shown that about 25\%
of final total entropy is generated during the hydrodynamic evolution of
chemically undersaturated quark-gluon plasma.
