Particle collisions reveal hidden rules for rare quark behavior
Physicists discovered that exotic particles called psi(2S) mesons behave differently depending on collision intensity—but only under specific conditions. The finding refines models of how quarks interact in extreme conditions, information crucial for validating physics theories used in emerging quantum technologies and next-generation particle detectors.
Originaltitel: Multiplicity dependence of Ï<sub>Ï(2S)</sub>/Ï<sub><em>J</em>/Ï</sub> in <em>pp</em> collisions at â<em>s</em>=13 TeV
<p>The ratio of production cross-sections of psi(2S) over J/psi mesons as a function of charged-particle multiplicity in proton-proton collisions at a centre-of-mass energy root s = 13 TeV is measured with a data sample collected by the LHCb detector, corresponding to an integrated luminosity of 658 pb(-1). The ratio is measured for both prompt and non-prompt psi(2S) and J/psi mesons. When there is an overlap between the rapidity ranges over which multiplicity and charmonia production are measured, a multiplicity-dependent modification of the ratio is observed for prompt mesons. No significant multiplicity dependence is found when the ranges do not overlap. For non-prompt production, the psi(2S)-to- J/psi production ratio is roughly independent of multiplicity, irrespective of the rapidity range over which the multiplicity is measured. The results are compared to predictions of the co-mover model and agree well except in the low multiplicity region. The ratio of production cross-sections of psi(2S) over J/psi mesons are cross-checked with other measurements in di-lepton channels and found to be compatible.</p>