Abstract
The study of the strength and behavior of the antikaon-nucleon ((K) over
bar N) interaction constitutes one of the key focuses of the strangeness
sector in low-energy quantum chromodynamics (QCD). In this Letter a
unique high-precision measurement of the strong interaction between
kaons and protons, close and above the kinematic threshold, is
presented. The femtoscopic measurements of the correlation function at
low pair-frame relative momentum of (K+ p circle plus K- (p) over bar)
and (K- p circle plus K+ (p) over bar) pairs measured in pp collisions
at root s = 5, 7, and 13 TeV are reported. A structure observed around a
relative momentum of 58 MeV/c in the measured correlation function of
(K- p circle plus K+ (p) over bar) with a significance of 4.4 sigma
constitutes the first experimental evidence for the opening of the ((K)
over bar (0)(n) circle plus K-0 (n) over bar) breaking channel due to
the mass difference between charged and neutral kaons. The measured
correlation functions have been compared to Julich and Kyoto models in
addition to the Coulomb potential. The high-precision data at low
relative momenta presented in this work prove femtoscopy to be a
powerful complementary tool to scattering experiments and provide new
constraints above the (K) over barN threshold for low-energy QCD chiral
models.