Dergi makalesi Açık Erişim

Evidence of rescattering effect in Pb–Pb collisions at the LHC through production of K And (1020) Mesons

2020    CERN İşbirliği

Measurements of K${}^{⁎}\left(892\right)^{0}$ and $\varphi \left(1020\right)$ resonance production in Pb–Pb and pp collisions at $\sqrt{{s}_{\mathrm{NN}}}$ = 5.02 TeV with the ALICE detector at the Large Hadron Collider are reported. The resonances are measured at midrapidity ($|y|$ < 0.5) via their hadronic decay channels and the transverse momentum (${p}_{T}$) distributions are obtained for various collision centrality classes up to ${p}_{T}$ = 20 GeV/c. The ${p}_{T}$-integrated yield ratio K${}^{⁎}\left(892\right)^{0}$/K in Pb–Pb collisions shows significant suppression relative to pp collisions and decreases towards more central collisions. In contrast, the $\varphi \left(1020\right)$/K ratio does not show any suppression. Furthermore, the measured K${}^{⁎}\left(892\right)^{0}$/K ratio in central Pb–Pb collisions is significantly suppressed with respect to the expectations based on a thermal model calculation, while the $\varphi \left(1020\right)$/K ratio agrees with the model prediction. These measurements are an experimental demonstration of rescattering of K${}^{⁎}\left(892\right)^{0}$ decay products in the hadronic phase of the collisions. The K${}^{⁎}\left(892\right)^{0}$/K yield ratios in Pb–Pb and pp collisions are used to estimate the time duration between chemical and kinetic freeze-out, which is found to be ∼ 4–7 fm/c for central collisions. The ${p}_{T}$-differential ratios of K${}^{⁎}\left(892\right)^{0}$/K, $\varphi \left(1020\right)$/K, K${}^{⁎}\left(892\right)^{0}$/π, $\varphi \left(1020\right)$/π, p/K${}^{⁎}\left(892\right)^{0}$ and p/$\varphi \left(1020\right)$ are also presented for Pb–Pb and pp collisions at $\sqrt{{s}_{\mathrm{NN}}}$ = 5.02 TeV. These ratios show that the rescattering effect is predominantly a low-${p}_{T}$ phenomenon.