Background magnetic field stabilizes QCD string against breaking

Abstract

The confinement of quarks in hadrons occurs due to formation of QCD string. At large separation between the quarks the QCD string breaks into pieces due to light quark-antiquark pair creation. We argue that there exist a critical background magnetic field e B ~ 16 m_\pi^2, above which the string breaking is impossible in the transverse directions with respect to the axis of the magnetic field. Thus, at strong enough magnetic field a new, asymmetrically confining phase may form. The effect - which can potentially be tested at LHC/ALICE experiment - leads to abundance of u-quark rich hadrons and to excess of radially excited mesons in the noncentral heavy-ion collisions compared to the central ones.