Observation of abnormal suppression of $\mathrm{f}_{0}$(980) production in p$-$Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV

The dependence of $\mathrm{f}_{0}$(980) production on the final-state charged-particle multiplicity in p$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV is reported. The production of $\mathrm{f}_{0}$(980) is measured with the ALICE detector via the $\mathrm{f}_0 (980) \rightarrow \pi^{+}\pi^{-}$ decay channel in a midrapidity region of $-0.5<~y<~0$. Particle yield ratios of $\mathrm{f}_{0}$(980) to $\pi$ and $\mathrm{K}^{*}$(892)$^{0}$ are found to be decreasing with increasing charged-particle multiplicity. The magnitude of the suppression of the $\mathrm{f}_{0}$(980)/$\pi$ and $\mathrm{f}_{0}$(980)/$\mathrm{K}^{*}$(892)$^{0}$ yield ratios is found to be dependent on the transverse momentum $p_{\mathrm{T}}$, suggesting different mechanisms responsible for the measured effects. Furthermore, the nuclear modification factor $Q_{\mathrm{pPb}}$ of $\mathrm{f}_{0}$(980) is measured in various multiplicity ranges. The $Q_{\mathrm{pPb}}$ shows a strong suppression of the $\mathrm{f}_{0}$(980) production in the $p_{\mathrm{T}}$ region up to about 4 GeV/$c$. The results on the particle yield ratios and $Q_{\mathrm{pPb}}$ for $\mathrm{f}_{0}$(980) may help to understand the late hadronic phase in p$-$Pb collisions and the nature of the internal structure of $\mathrm{f}_{0}$(980) particle.

 

Submitted to: PLB
e-Print: arXiv:2311.11786 | PDF | inSPIRE
CERN-EP-2023-263
Figure group

Figure 1

Invariant mass distribution of $\pi^{+}\pi^{-}$ pairs in $-0.5< y after="" the="" like-sign="" background="" subtraction="" in="" p--pb="" collisions="" at="" left="" plot="" is="" obtained="" low="" of="" pairs="" minimum="" bias="" events.="">< /y>

Figure 2

Transverse momentum spectra of \fzero in p--Pb collisions at \snn = 5.02 TeV for different multiplicity classes, which are scaled for visibility. Statistical and systematic uncertainties are shown as error bars and boxes, respectively. The normalization uncertainty of 13\% due to the uncertainty of the $\mathrm{B.R.}$ is not shown in the figure. The lower panel shows the ratios of the spectra in multiplicity classes to the NSD spectrum.

Figure 3

Double ratios of $\phi$ , \kstar , and \fzero to $\pi$  (left) and \fzero to \kstar (right) as a function of charged-particle multiplicity raised to the power of 1/3. The ratio in each multiplicity class is divided by the ratio in low-multiplicity (LM, 60--100\%) events to allow for a direct comparison among different hadron species and reduce systematic uncertainties. V0A is utilized to categorize events based on their multiplicity. Predictions from the canonical statistical model are represented with lines.

Figure 4

The particle yield ratios of \fzero to $\pi$ as a function of $p_{\rm{T}}$ in high-multiplicity (circles) and low-multiplicity (squares) p--Pb collisions at \snn = 5.02 TeV. The lower panel shows the double ratio of \fzero/$\pi$ between the high-multiplicity and low-multiplicity events. V0A is utilized to categorize events based on their multiplicity.

Figure 5

The particle yield ratio of \fzero to \kstar as a function of $p_{\rm{T}}$ in high-multiplicity (circles) and low-multiplicity (squares) p--Pb collisions at \snn = 5.02 TeV. The lower panel shows the double ratio of high-multiplicity to low-multiplicity \fzero/\kstar. V0A is utilized to categorize events based on their multiplicity.

Figure 6

Nuclear modification factor ($Q_{\rm{pPb}}$) of \fzero as a function of $p_{\rm{T}}$ in p--Pb collisions at \snn = 5.02 TeV for different multiplicity classes. The multiplicity class is defined with the ZNA, which is the ZN placed on the Pb-going side. Statistical and systematic uncertainties are shown as error bars and boxes, respectively. Black boxes around unity represent the binary collision scaling uncertainties. The $Q_{\rm{pPb}}$ of charged hadrons  are reported for comparison.