Production of $Σ(1385)^{\pm}$ and $Ξ(1530)^{0}$ in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV

The transverse momentum distributions of the strange and double-strange hyperon resonances ($\Sigma(1385)^{\pm}$, $\Xi(1530)^{0}$) produced in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV were measured in the rapidity range $-0.5<~ y_{\rm{CMS}}<~0$ for event classes corresponding to different charged-particle multiplicity densities, $\langle{\rm d}N_{\rm{ch}}/{\rm d}\eta_{\rm{lab}}\rangle$. The mean transverse momentum values are presented as a function of $\langle{\rm d}N_{\rm{ch}}/{\rm d}\eta_{\rm{lab}}\rangle$, as well as a function of the particle masses and compared with previous results on hyperon production. The integrated yield ratios of excited to ground-state hyperons are constant as a function of $\langle{\rm d}N_{\rm{ch}}/{\rm d}\eta_{\rm{lab}}\rangle$. The equivalent ratios to pions exhibit an increase with $\langle{\rm d}N_{\rm{ch}}/{\rm d}\eta_{\rm{lab}}\rangle$, depending on their strangeness content.

Figures

Figure 1

 Sketch of the decay modes for $\Sigma^{*+}$ (left) and $\Xi^{*0}$ (right) and depiction of the track and topological selection criteria.

Figure 2

 (Left) The $\Lambda\pi^{+}$~invariant mass distribution (Same-event pairs) in2.0~$<$~\pt~$<$~2.5~\gmom~and for the multiplicity class 20-60\%. The background shape,using pairs from different events (Mixed-event background),is normalised to the counts in 1.9~$< M_{\Lambda\pi}<$~2.0~\Gmass. (Right) The invariant massdistribution after subtraction of the mixed-event background. The solid curverepresents the combined fit, while the dashed line describes the residual background

Figure 3

 (Left) The $\Xi^{\mp}\pi^{\pm}$ invariant mass distribution (Same-event pairs) in1.8~$<$~\pt~$<$~2.2~\gmom~and for the multiplicity class 20-40\%. The background shape,using pairs from different events (Mixed-event background), is normalised to the counts in1.49~$<$~$M_{\Xi\pi}$~$<$~1.51~\Gmass~and 1.56~$<$~$M_{\Xi\pi}$~$<$~1.58~\Gmass (Right) The invariant mass distribution after subtraction of the mixed-event background The solid curve represents the combined fit, while the dashed line describes the residual background.

Figure 4

 The geometrical acceptance and the reconstruction efficiency (A $\times$ $\epsilon$) for $\Sigma^{*+}$ and $\Xi^{*0}$ in $-0.5 < y_{\mathrm{CMS}^{\mathrm{MC}}} <$ 0 for minimum-bias events, obtained with DPMJET~3.05~ and GEANT~3.1 ~. Only statistical uncertainties are shown.

Figure 5

 Transverse momentum spectra of $\Sigma^{*+}$ (left) and $\Xi^{*0}$ (right) in different multiplicity classes in the rapidity range $-0.5< y_{\mathrm{CMS}}< 0$. For~$\Xi^{*0}$, both particles and antiparticles are analysed together. Statistical (bars) and systematic (boxes) uncertainties are included. The dashed curves are L\'{e}vy-Tsallis fit to each individual distribution.

Figure 6

 Mean transverse momenta $\mpt$ of $\Lambda$, $\Xi^{-}$, $\Sigma^{*\pm}$, $\Xi^{*0}$ and $\Omega^{-}$ in p--Pb collisions at $\snn$ = 5.02 TeV as a function of mean charged-particle multiplicity density $\langle$d$N_{\mathrm{ch}}$/d$\eta_{\mathrm{lab}}\rangle$, measured in the pseudorapidity range $\mid\eta_{\mathrm{lab}}\mid <$~0.5. The results for $\Lambda$, $\Xi^{-}$ and $\Omega^{-}$ are taken from~. Statistical and systematic uncertainties are represented as bars and boxes, respectively. The $\Omega^-$ and $\Xi^-$ points in the 3rd and 4th lowest multiplicity bins are slightly displaced along the abscissa to avoid superposition with the $\Xi^{*0}$ points.

Figure 7

 Mass dependence of the mean transverse momenta of identified particles for the $0-20$\% V0A multiplicity class and with $-0.5< y_{\mathrm{CMS}}< 0$ in p--Pb~collisions at $\sqrt{s_{\mathrm{NN}}}$~=~5.02~TeV~, and in minimum-bias pp collisions at $\sqrt{s}$~=~7~TeV~ with $|y_{\mathrm{CMS}}|< 0.5$. Additionally, $D^0$ and $J$/$\psi$ results are plotted The $D^0$ and $J$/$\psi$ were measured in different rapidity ranges: $|y_{\mathrm{CMS}}|< 0.5$~ ($|y_{\mathrm{CMS}}|< 0.9$~) for $D^0$ ($J$/$\psi$) in pp and $-0.96 < y_{\mathrm{CMS}}< 0.04$~ ($-1.37< y_{\mathrm{CMS}}< 0.43$~) for $D^0$ ($J$/$\psi$) in p--Pb. Note also that the results for $D^0$ and $J$/$\psi$ in p-Pb collisions are for the 0-100\% multiplicity class.

Figure 8

 (Left) Ratio of $\Sigma^{*\pm}$ to $\Lambda$ and (Right) ratio of $\Xi^{*0}$ to $\Xi^-$ measured in \pp~, d--Au~ and \pPb~ collisions, as a function of $\langle$d$N_{\mathrm{ch}}$/d$\eta_{\mathrm{lab}}\rangle$ measured at midrapidity Statistical uncertainties (bars) are shown as well as total systematic uncertainties (hollow boxes) and systematic uncertainties uncorrelated across multiplicity (shaded boxes) A few model predictions are also shown as lines at their appropriate abscissa.

Figure 9

 (Left) Ratio of $\Sigma^{*\pm}$ to $\pi^{\pm}$ and (Right) ratio of $\Xi^{*0}$ to $\pi^{\pm}$, measured in \pp~, d--Au~ and \pPb~ collisions, as a function of the average charged particle density ($\langle$d$N_{\mathrm{ch}}$/d$\eta_{\mathrm{lab}}\rangle$) measured at midrapidity Statistical uncertainties (bars) are shown as well as total systematic uncertainties (hollow boxes) and systematic uncertainties uncorrelated across multiplicity (shaded boxes). A few model predictions are also shown as lines at their appropriate abscissa.