  The production of quark-antiquark pairs along a color flux tube precedes the
fragmentation of the tube. Because of local conservation laws, the production
of a $q$-$\bar q$ pair will lead to correlations of adjacently produced mesons
(mostly pions). Adjacently produced mesons however can be signalled by their
rapidity difference $\Delta y$ falling within the window of $|\Delta y |
$$\lesssim$$ 1/(dN/dy)$, on account of the space-time-rapidity ordering of
produced mesons in a flux tube fragmentation. Therefore, the local conservation
laws of momentum, charge, and flavor will lead to a suppression of angular
correlation function $dN/(d\Delta \phi\, d\Delta y)$ for two mesons with
opposite charges or strangeness on the near side at $(\Delta \phi, \Delta y)$$
\sim$0, but an enhanced correlation on the back-to-back, away side at $\Delta
\phi$$\sim$$ \pi$, within the window of $|\Delta y |$$\lesssim$$ 1/(dN/dy)$.
These properties can be used as signatures for the fragmentation of a color
flux tube. The gross features of the signature of flux tube fragmentation for
two oppositely charged mesons are qualitatively consistent with the STAR and
NA61/SHINE angular correlation data for two hadrons with opposite charges in
the low-$p_T$ region in high-energy $pp$ collisions.
