The pseudorapidity density of charged particles with minimum transverse momentum ($p_{\rm T}$) thresholds of 0.15, 0.5, 1, and 2 GeV$/c$ was measured in pp collisions at centre-of-mass energies of $\sqrt{s} = 5.02$ and $13$ TeV with the ALICE detector. The study is carried out for inelastic collisions with at least one primary charged particle having a pseudorapidity ($\eta$) within $\pm0.8$ and $p_{\rm T}$ larger than the corresponding threshold. The measurements were also performed for inelastic and non-single-diffractive events as well as for inelastic events with at least one charged particle having $|\eta|<~1$ in pp collisions at $\sqrt{s} = 5.02$ TeV for the first time at the LHC. The measurements are compared to the PYTHIA 6, PYTHIA 8, and EPOS-LHC models. In general, the models describe the pseudorapidity dependence of particle production well, however, discrepancies are observed for event classes including diffractive events and for the highest transverse momentum threshold ($p_{\rm T} > 2$ GeV$/c$), highlighting the importance of such measurements for tuning event generators. The new measurements agree within uncertainties with results from the ATLAS and CMS experiments.
Submitted to: PRD
e-Print: arXiv:2211.15364 | PDF | inSPIRE
CERN-EP-2022-262
Figure group
Figure 1
The distributions of $\dndeta$ for INEL (left panel), NSD (middle panel), and $\inelg$ (right panel) event classes in pp collisions at $\sqrt{s} = 5.02$ TeV. Data are compared to simulations obtained with PYTHIA 6 with the Perugia 2011 tuning and PYTHIA 8 with the Monash 2013 tuning. Grey bands (unfilled rectangles) represent the uncorrelated (correlated) systematic uncertainties from data. The bottom part of the figure shows the ratios between models and data. |  |
Figure 3
Pseudorapidity density distributions of charged particles, $\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta$, in pp collisions at $\sqrt{s} = $ 5.02 TeV for the four event classes, $\inelf$, $\inels$, $\inelt$, and $\inelq$, compared to the distributions from models: PYTHIA 8 Monash 2013 and EPOS LHC. Grey bands (unfilled rectangles) represent the uncorrelated (correlated) systematic uncertainties from data. |  |
Figure 4
Pseudorapidity density distributions of charged particles, $\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta$, in pp collisions at $\sqrt{s}=$ 13 TeV for the four event classes, $\inelf$, $\inels$, $\inelt$, and $\inelq$, compared to the distributions from models: PYTHIA 8 Monash 2013 and EPOS LHC. Grey bands (unfilled rectangles) represent the uncorrelated (correlated) systematic uncertainties from data. |  |
Figure 5
The distributions of $\dndeta$ for the $\inels$ event class are normalised to the (a) $\inelsss$ and (b) $\inelss$ event classes using PYTHIA 8 with the Monash 2013 tuning in pp collisions at $\cms = 13$ TeV . The bottom panels show the ratio of $\dndeta$ for the $\inelsss$ (left) and $\inelss$ (right) event class between ALICE and ATLAS (left) and between ALICE and CMS (right), respectively. |  |