Production of Σ(1385)± and Ξ(1530)0 in p-Pb collisions at sNN=5.02 TeV

Abstract

The transverse momentum distributions of the strange and double-strange hyperon resonances ($\Sigma {\left(1385\right)}^{\pm }$, $\Xi {\left(1530\right)}^0$) produced in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV were measured in the rapidity range $-0.5<y_{\mathrm{CMS}}<0$ for event classes corresponding to different charged-particle multiplicity densities, $⟨$d$N_{\mathrm{ch}}$/d${\eta }_{\mathrm{lab}}⟩$. The mean transverse momentum values are presented as a function of $⟨$d$N_{\mathrm{ch}}$/d${\eta }_{\mathrm{lab}}⟩$, 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 $⟨$d$N_{\mathrm{ch}}$/d${\eta }_{\mathrm{lab}}⟩$. The equivalent ratios to pions exhibit an increase with $⟨$d$N_{\mathrm{ch}}$/d${\eta }_{\mathrm{lab}}⟩$, depending on their strangeness content.

Fig. 1

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

Fig. 2

(Left) the $\mathrm{\Lambda }{\mathit{\pi }}^{+}$ invariant mass distribution (same-event pairs) in 2.0 < $p_{\mathrm{T}}$ < 2.5 $\mathrm{GeV}/\mathrm{c}$ 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 $<M_{\mathrm{\Lambda }\mathit{\pi }}<$ 2.0 ${\mathrm{GeV}/\mathrm{c}}^2$. (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

Fig. 3

(Left) the ${\mathrm{\Xi }}^{\mp }{\mathit{\pi }}^{\pm }$ invariant mass distribution (same-event pairs) in 1.8 < $p_{\mathrm{T}}$ < 2.2 $\mathrm{GeV}/\mathrm{c}$ and for the multiplicity class 20–40%. The background shape, using pairs from different events (mixed-event background), is normalised to the counts in $1.49<M_{\mathrm{\Xi }\mathit{\pi }}<1.51$ ${\mathrm{GeV}/\mathrm{c}}^2$ and $1.56<M_{\mathrm{\Xi }\mathit{\pi }}<1.58$ ${\mathrm{GeV}/\mathrm{c}}^2$. (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

Fig. 4

The geometrical acceptance and the reconstruction efficiency (A $\times$ $\mathit{\epsilon }$) for ${\mathrm{\Sigma }}^{\ast +}$ and ${\mathrm{\Xi }}^{\ast 0}$ in $-0.5<y_{{\mathrm{CMS}}^{\mathrm{MC}}}<$ 0 for minimum-bias events, obtained with DPMJET 3.05 [19] and GEANT 3.1  [27]. Only statistical uncertainties are shown

Fig. 5

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

Fig. 6

Mean transverse momenta $⟨p_{\mathrm{T}}⟩$ of $\mathrm{\Lambda }$, ${\mathrm{\Xi }}^{-}$, ${\mathrm{\Sigma }}^{\ast \pm }$, ${\mathrm{\Xi }}^{\ast 0}$ and ${\mathrm{\Omega }}^{-}$ in p–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV as a function of mean charged-particle multiplicity density $⟨$d$N_{\mathrm{ch}}$/d${\mathit{\eta }}_{\mathrm{lab}}⟩$, measured in the pseudorapidity range $\mid {\mathit{\eta }}_{\mathrm{lab}}\mid <$ 0.5. The results for $\mathrm{\Lambda }$, ${\mathrm{\Xi }}^{-}$ and ${\mathrm{\Omega }}^{-}$ are taken from [10, 14, 24]. Statistical and systematic uncertainties are represented as bars and boxes, respectively. The ${\mathrm{\Omega }}^{-}$ and ${\mathrm{\Xi }}^{-}$ points in the 3rd and 4th lowest multiplicity bins are slightly displaced along the abscissa to avoid superposition with the ${\mathrm{\Xi }}^{\ast 0}$ points

Fig. 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 [10, 24], and in minimum-bias pp collisions at $\sqrt{s}=7$ TeV [17] with $|y_{\mathrm{CMS}}|<0.5$. Additionally, $D^0$ and J/$\mathit{\psi }$ results are plotted. The $D^0$ and J/$\mathit{\psi }$ were measured in different rapidity ranges: $|y_{\mathrm{CMS}}|<0.5$ [34] ($|y_{\mathrm{CMS}}|<0.9$ [35]) for $D^0$ (J/$\mathit{\psi }$) in pp and $-0.96<y_{\mathrm{CMS}}<0.04$ [34] ($-1.37<y_{\mathrm{CMS}}<0.43$ [36]) for $D^0$ (J/$\mathit{\psi }$) in p–Pb. Note also that the results for $D^0$ and J/$\mathit{\psi }$ in p–Pb collisions are for the 0–100% multiplicity class

Fig. 8

(Left) ratio of ${\mathrm{\Sigma }}^{\ast \pm }$ to $\mathrm{\Lambda }$ and (Right) ratio of ${\mathrm{\Xi }}^{\ast 0}$ to ${\mathrm{\Xi }}^{-}$ measured in $\mathrm{pp}$ [17, 32, 37, 39], d–Au [32, 37] and $\text{p--Pb}$ [10, 24] collisions, as a function of $⟨$d$N_{\mathrm{ch}}$/d${\mathit{\eta }}_{\mathrm{lab}}⟩$ 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

Fig. 9

(Left) ratio of ${\mathrm{\Sigma }}^{\ast \pm }$ to ${\mathit{\pi }}^{\pm }$ and (Right) ratio of ${\mathrm{\Xi }}^{\ast 0}$ to ${\mathit{\pi }}^{\pm }$, measured in $\mathrm{pp}$ [17, 32, 41, 42], d–Au [32, 37] and $\text{p--Pb}$ [24] collisions, as a function of the average charged particle density ($⟨$d$N_{\mathrm{ch}}$/d${\mathit{\eta }}_{\mathrm{lab}}⟩$) 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