Physicists spot unexpected particle behavior in high-energy collisions
Researchers at CERN's LHCb experiment observed that certain particles form more frequently than theory predicts when protons and lead nuclei collide at extreme energies. The finding suggests matter behaves differently under extreme density—knowledge essential for understanding fundamental physics and potentially informing next-generation particle detector design.
Originaltitel: Observation of strangeness enhancement with charmed mesons in high-multiplicity <em>p</em>Pb collisions at √<em>s</em><sub>NN</sub>=8.16 TeV
<p>The production of prompt D<sub>s</sub><sup>+</sup> and D<sup>+</sup> mesons is measured by the LHCb experiment in proton-lead (pPb) collisions in both the forward (1.5 < y* < 4.0) and backward (-5.0 < y* < -2.5) rapidity regions at a nucleon-nucleon center-of-mass energy of √s<sub>NN</sub> = 8.16 TeV. The nuclear modification factors of both D<sub>s</sub><sup>+</sup> and D<sup>+</sup> mesons are determined as a function of transverse momentum, p<sub>T</sub>, and rapidity. In addition, the D<sub>s</sub><sup>+</sup> to D<sup>+</sup> cross section ratio is measured as a function of the primary charged particle multiplicity in the event. An enhanced D<sub>s</sub><sup>+</sup> to D<sup>+</sup> production in high-multiplicity events is observed for the whole measured p<sub>T</sub> range, in particular at low p<sub>T</sub> and backward rapidity, where the significance exceeds six standard deviations. This constitutes the first observation of strangeness enhancement in charm quark hadronization in high-multiplicity pPb collisions. The results are also qualitatively consistent with the presence of quark coalescence as an additional charm quark hadronization mechanism in high-multiplicity proton-lead collisions.</p>