Rise of the partons transverse momenta in the current fragmentation region and the bi-concave shape of fast hadrons at high energies.
by
Boris Blok(Technion)
→
Europe/Zurich
TH Theory Conference Room (CERN)
TH Theory Conference Room
CERN
Description
We find the increase with energy of the scale of parton momenta in the current fragmentation region in the limit $x_B\rightarrow 0$ and fixed $Q^2$ . The dispersion representation over $Q^2$ for LT pQCD zero angle amplitude of $\gamma^*+T\to \gamma^*+T$ scattering at large energies is derived using the $k_t$ factorization and used to evaluate the scales of the hard processes in the current fragmentation region.
The necessity to include change of pQCD regime at small $x$ into QCD evolution equation and BFKL type approximations is explained.
The modified Gribov formula is derived which describes the total cross-section of the DIS in the black disc (BD) regime. We find that the coherence length of the DIS processes within the black disk regime increases with energy as $\propto s^{0.5-0.6}$, significantly slower than in the parton model ($1/2m_Nx$ - the Ioffe length). As a result the local gluon densities may not decrease at high energies.
As a result in the Black Disk regime the energetic hadron(nucleus) looks as biconcave lense rather than pancake. Possible manifestations of the pattern found in the proximity of the BD regime in DIS for proton-proton collisions at LHC are briefly discussed.
