Measurement of prompt D$^{0}$, $Λ_{c}^{+}$, and $Σ_{c}^{0,++}$(2455) production in pp collisions at $\sqrt{s} = 13$ TeV

The $p_{\rm T}$-differential production cross sections of prompt D$^{0}$, $\Lambda_{\rm c}^{+}$, and $\Sigma_{\rm c}^{0,++}(2455)$ charmed hadrons are measured at midrapidity ($|y| <~ 0.5$) in pp collisions at $\sqrt{s} = 13$ TeV. This is the first measurement of $\Sigma_{\rm c}^{0,++}$ production in hadronic collisions. Assuming the same production yield for the three $\Sigma_{\rm c}^{0,+,++}$ isospin states, the baryon-to-meson cross-section ratios $\Sigma_{\rm c}^{0,+,++}/{\rm D}^{0}$ and $\Lambda_{\rm c}^{+}/{\rm D}^{0}$ are calculated in the transverse momentum ($p_{\rm T}$) intervals $2 <~ p_{\rm T} <~ 12$ GeV/$c$ and $1 <~ p_{\rm T} <~ 24$ GeV/$c$. Values significantly larger than in e$^{+}$e$^{-}$ collisions are observed, indicating for the first time that baryon enhancement in hadronic collisions also extends to the $\Sigma_{\rm c}$. The feed-down contribution to $\Lambda_{\rm c}^{+}$ production from $\Sigma_{\rm c}^{0,+,++}$ is also reported and is found to be larger than in e$^{+}$e$^{-}$ collisions. The data are compared with predictions from event generators and other phenomenological models, providing a sensitive test of the different charm-hadronisation mechanisms implemented in the models.


Submitted to: PRL
e-Print: arXiv:2106.08278 | PDF | inSPIRE

Figure 2

Prompt-charm-hadron cross-section ratios: $\Lambdac/\Dzero$ (left), $\SigmacZeroPlusPlusPlus/\Dzero$ (middle), and $\LambdacFromScZeroPlusPlusPlus/\Lambdac$ (right), in pp collisions at $\sqrt{s}=13$\,\TeV, compared with model expectations~ and (left) with data from pp collisions at $\sqrt{s}=5.02$\,\TeV~. The horizontal lines reflect the width of the $\pt$ intervals. The PYTHIA Monash 2013 curve is scaled by a factor of 10 in the middle panel.