The first measurements of $\mathrm{K^{*}(892)^{0}}$ resonance production as a function of charged-particle multiplicity in Xe$-$Xe collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.44 TeV and pp collisions at $\sqrt{s}=$ 5.02 TeV using the ALICE detector are presented. The resonance is reconstructed at midrapidity ($|y|<~ 0.5$) using the hadronic decay channel $\mathrm{K^{*0}} \rightarrow \mathrm{K^{\pm} \pi^{\mp}}$. Measurements of transverse-momentum integrated yield, mean transverse-momentum, nuclear modification factor of $\mathrm{K^{*0}}$, and yield ratios of resonance to stable hadron ($\mathrm{K^{*0}}$/K) are compared across different collision systems (pp, p$-$Pb, Xe$-$Xe, and Pb$-$Pb) at similar collision energies to investigate how the production of $\mathrm{K^{*0}}$ resonances depends on the size of the system formed in these collisions. The hadronic rescattering effect is found to be independent of the size of colliding systems and mainly driven by the produced charged-particle multiplicity, which is a proxy of the volume of produced matter at the chemical freeze-out. In addition, the production yields of $\mathrm{K^{*0}}$ in Xe$-$Xe collisions are utilized to constrain the dependence of the kinetic freeze-out temperature on the system size using the hadron resonance gas in partial chemical equilibrium (HRG-PCE) model.
Phys. Rev. C 109, 014911 (2024)
HEP Data
e-Print: arXiv:2308.16115 | PDF | inSPIRE
CERN-EP-2023-175
Figure group
Figure 1
The left panel shows the invariant mass distribution of unlike sign $\pi$K pairs from the same and mixed events. The right panel shows the same but after the mixed-event background subtraction. The mixed event background subtracted invariant mass distribution is fitted with a combination of Breit--Wigner function and second order polynomial distribution. The Breit--Wigner distribution represents the ${\rm K^{*0}}$ signal and the second order polynomial describes the residual background. |   |
Figure 2
Upper panel: The $p_{\mathrm{T}}$ spectra of ${\rm K^{*0}}$ in various multiplicity classes of pp collisions at $\s$ = 5.02 TeV. Lower panel: The ratios of the multiplicity-dependent $\pt$ spectra to the multiplicity-integrated INEL$>$ 0 spectra. The statistical and systematic uncertainties are shown as bars and boxes, respectively. |  |
Figure 3
The left panel shows the $\pt$ distributions of ${\rm K^{*0}}$ meson in four different centrality classes of Xe-Xe collisions at $\snn$ = 5.44 TeV. The right panel shows the comparison between the ${\rm K^{*0}}$ $\pt$ spectrum in 0$-$30$\%$ Xe-Xe collisions at $\snn$ = 5.44 TeV and in 20$-$30$\%$ Pb-Pb collisions at $\snn$ = 5.02 TeV, both having similar multiplicities. The statistical and systematic uncertainties are shown by bars and boxes, respectively. |  |
Figure 4
The ${\rm d}N/{\rm d}y$ (left panel) and $\langle \pt \rangle$ (right panel) of ${\rm K^{*0}}$ as a function of $\langle {\rm d}N_{\rm ch}/{\rm d}\eta \rangle^{1/3}_{|\eta|< 0.5}$ in pp collision at $\s$ = 5.02 TeV and in Xe-Xe collisions at $\snn$ = 5.44 TeV. Measurements are compared with the results obtained in p--Pb and Pb-Pb collisions at $\snn$ = 5.02 TeV. Bars and shaded boxes correspond to the statistical and systematic uncertainties, respectively. |  |
Figure 5
The left panel shows the measured ${\rm K^{*0}}$/K yield ratio along with model calculation. The right panel shows the lower limit of hadronic phase lifetime as a function of $\langle {\rm d}N_{\rm ch}/{\rm d}\eta \rangle^{1/3}_{|\eta|< 0.5}$ in different collision systems. Bars and shaded boxes represent the statistical and systematic uncertainties, respectively. |  |
Figure 6
The kinetic freeze-out temperature estimated using the fit of HRG-PCE model to the measured yields of $\pi^{\pm}$, K$^{\pm}$, p($\overline{\mathrm{p}}$), $\phi$, ${\rm K^{*0}}$ in different centrality classes of Xe$-$Xe collisions at $\snn$ = 5.44 TeV. Results are compared with extracted kinetic freeze-out temperature in Pb$-$Pb collisions at $\snn$ = 5.02 TeV. |  |
Figure 7
The ${\rm K^{*0}}$/K and $\phi/$K yield ratios as a function of $\langle {\rm d}N_{\rm ch}/{\rm d}\eta \rangle^{1/3}_{|\eta|< 0.5}$ in Xe-Xe collisions at $\snn$ = 5.44 TeV. The left and right panels show the measurements for a low-$\pt$ and a high-$\pt$ interval, respectively. Statistical and systematic uncertainties are represented by bars and shaded boxes. |  |
Figure 8
The left panel shows the nuclear modification factor as a function of $\pt$ for the ${\rm K^{*0}}$ meson in 0$-$30$\%$ Xe$-$Xe collisions at $\snn$ = 5.44 TeV and in 20$-$30$\%$ Pb$-$Pb collisions at $\snn$ = 5.02 TeV. The right panel shows the R$_{\mathrm{AA}}$ of ${\rm K^{*0}}$ as a function of $\langle {\rm d}N_{\rm ch}/{\rm d}\eta \rangle^{1/3}_{|\eta|< 0.5}$ for 4.0 $< \pt <$ 12.0 GeV/$c$ in Xe$-$Xe collisions. The results are compared to the $R_{\mathrm{AA}}$ of charged hadron. Statistical and systematic uncertainties are represented by bars and shaded boxes. |   |