Measurement of the production cross section of prompt $Ξ^0_{\rm c}$ baryons at midrapidity in pp collisions at $\sqrt{s}$ = 5.02 TeV

The transverse momentum ($p_{\rm T}$) differential cross section of the charm-strange baryon $\Xi^0_{\rm c}$ is measured at midrapidity ($|y|<~$ 0.5) via its semileptonic decay into ${\rm e^{+}}\Xi^{-}\nu_{\rm e}$ in pp collisions at $\sqrt{s}$ = 5.02 TeV with the ALICE detector at the LHC. The ratio of the $p_{\rm T}$-differential $\Xi^0_{\rm c}$-baryon and ${\rm D^0}$-meson production cross sections is also reported. The measurements are compared with simulations with different tunes of the PYTHIA 8 event generator, with predictions from a statistical hadronisation model (SHM) with a largely augmented set of charm-baryon states beyond the current lists of the Particle Data Group, and with models including hadronisation via quark coalescence. The $p_{\rm T}$-integrated cross section of prompt $\Xi^0_{\rm c}$-baryon production at midrapidity is also reported, which is used to calculate the baryon-to-meson ratio $\Xi^0_{\rm c}/{\rm D^0} = 0.20 \pm 0.04~{\rm (stat.)} ^{+0.08}_{-0.07}~{\rm (syst.)}$. These results provide an additional indication of a modification of the charm fragmentation from $\rm e^+e^-$ and $\rm e^{-}p$ collisions to pp collisions.

 

JHEP 10 (2021) 159
HEP Data
e-Print: arXiv:2105.05616 | PDF | inSPIRE
CERN-EP-2021-079
Figure group

Figure 1

Left panel: $n_{\sigma\textrm{,e}}^\textrm{TPC}$ distribution as a function of the electron \pt after applying the particle identification criteria on the TOF signal (see text for details). Right panel: invariant mass distribution of $\Xi^{-} \rightarrow \pi^{-}\Lambda$ (and charge conjugate) candidates integrated over $ p_{\rm T}^{\Xi^{-}}$ The arrow indicates the world average $\Xi^{-}$ mass~ and the dashed lines define the interval in which the $\Xi^{-}$ candidates are selected for the $\Xi^0_{\rm c}$ reconstruction (see text for details).

Figure 3

Correlation matrix between the generated $\Xi^0_{\rm c}$-baryon \pt and the reconstructed $ {\rm e}^{+}\Xi^{-}$ pair \pt, obtained from the simulation based on PYTHIA 8 described in the text.

Figure 4

Left panel: product of acceptance and efficiency for prompt and feed-down $\Xi^0_{\rm c}$ baryons in pp collisions at $\sqrt{s} =$ 5.02 TeV as a function of\pt. Right panel: fraction of prompt $\Xi^0_{\rm c}$ baryons in the raw yield ($f_{\rm prompt}$) as a function of \pt. The systematic uncertainties of $f_{\rm prompt}$ are shown as boxes.

Figure 5

Left panel: \pt-differential production cross sections of prompt $\Xi^0_{\rm c}$ baryons in pp collisions at $\sqrt{s}$~=~5.02~TeV and 13 TeV~ and of inclusive $\Xi^0_{\rm c}$ baryons in pp collisions at $\sqrt{s}$~=~7~TeV ~ with updated decay BR as discussed in the text. The uncertainty of the BR of the cross sections of prompt $\Xi^0_{\rm c}$ baryons in pp collisions at $\sqrt{s}$~=~13 TeV is lower because it consists in the combination of two different decay channels ($\Xi^0_{\rm c} \rightarrow {\rm e}^{+}\Xi^{-}\nu_{\rm e}$ and $\Xi^0_{\rm c} \rightarrow {\pi}^{+}\Xi^{-}$)~ Right panel: $\Xi^0_{\rm c}$/${\rm D^0}$ ratio measured in pp collisions at $\sqrt{s}$~=~5.02~TeV, compared with the measurements at $\sqrt{s}$~=~7~TeV~ and $\sqrt{s}$~=~13~TeV~. The uncertainty of the BR of ${\rm D^0}$ and $\Xi^0_{\rm c}$ are shown as shaded boxes.

Figure 6

Left panel: \pt-differential production cross section of prompt $\Xi^0_{\rm c}$ baryons in pp collisions at $\sqrt{s}$~=~5.02~TeV compared with model calculations~. Right panel: $\Xi^0_{\rm c}/{\rm D^0}$ ratio as a function of \pt measured in pp collisions at $\sqrt{s}$~=~5.02~TeV compared with model calculations~ (see text for details).