Fragmentation of Two Repelling Lund Strings

Understand

Motivated by recent discoveries of flow-like effects in pp collisions, and noting that multiple string systems can form and hadronize simultaneously in such collisions, we develop a simple model for the repulsive interaction between two Lund strings with a positive (colour-oriented) overlap in rapidity.

• The model is formulated in momentum space and is based on a postulate of a constant net transverse momentum being acquired per unit of overlap along a common rapidity direction.
• To conserve energy, the strings shrink in the longitudinal direction, essentially converting a portion of the string invariant mass $m^2$ into $p_{\perp}^2$ for constant $m_{\perp}^2 = m^2 + p_{\perp}^2$ for each string.
• The reduction in string invariant mass implies a reduced overall multiplicity of produced hadrons; the increase in $p_{\perp}^2$ is local and only affects hadrons in the overlapping region.