Investigating charm production and fragmentation via azimuthal correlations of prompt D mesons with charged particles in pp collisions at $\sqrt{s} = 13$ TeV

Angular correlations of heavy-flavour and charged particles in high-energy proton-proton collisions are sensitive to the production mechanisms of heavy quarks and to their fragmentation as well as hadronisation processes. The measurement of the azimuthal-correlation function of prompt D mesons with charged particles in proton-proton collisions at a centre-of-mass energy of $\sqrt{s} = 13$ TeV with the ALICE detector is reported, considering D$^{0}$, D$^{+}$, and D$^{*+}$ mesons in the transverse-momentum interval $3 <~ p_{\rm T} <~ 36$ GeV/$c$ at midrapidity ($|y| <~ 0.5$), and charged particles with $p_{\rm T} > 0.3$ GeV/$c$ and pseudorapidity $|\eta| <~ 0.8$. This measurement has an improved precision and provides an extended transverse-momentum coverage compared to previous ALICE measurements at lower energies. The study is also performed as a function of the charged-particle multiplicity, showing no modifications of the correlation function with multiplicity within uncertainties. The properties and the transverse-momentum evolution of the near- and away-side correlation peaks are studied and compared with predictions from various Monte Carlo event generators. The obtained results can provide constraints on the generators. Among those considered, PYTHIA8 and POWHEG+PYTHIA8 provide the best description of the measured observables.

 

Submitted to: EPJC
e-Print: arXiv:2110.10043 | PDF | inSPIRE
CERN-EP-2021-184

Figure 1

Average of the azimuthal-correlation functions of $\Dzero$, $\Dplus$, and $\Dstar$ mesons with associated particles, after the baseline subtraction, in pp collisions at $\sqrt{s}$ = 5.02~, 7~, and 13~TeV, for 3 $\pi$.

Figure 2

Near-side (left panel) and away-side (right panel) peak yields (first row) and widths (third row) obtained from a fit to the azimuthal-correlation function after the baseline subtraction. The measurements are compared with ALICE results obtained in pp collisions at $\sqrt{s}$ = 5.02~TeV~ and 7~TeV~, for 0.3 $

Figure 3

Azimuthal-correlation functions of $\Dzero$ mesons with associated particles, after the subtraction of the baseline, in pp collisions at $\sqrt{s}$ = 13~TeV, for 3 $$ 0.3~\GeVc, 0.3 $\pi$.

Figure 4

Near-side associated peak yields (top row) and widths (third row) measured in pp collisions at $\sqrt{s}$~=~13~TeV, for the four V0M multiplicity classes, shown with different marker styles. The ratios of yield (width) values in each V0M class with respect to those in the V0M class I are shown in the second (fourth) row. Results are presented as a function of the $\Dzero$-meson $\pt$, for $\ptass>$ 0.3~\GeVc and the sub-ranges 0.3 $

Figure 5

Away-side associated peak yields (left) and widths (right) measured in pp collisions at $\sqrt{s}$~=~13~TeV, for the four V0M multiplicity classes, shown with different marker styles. The ratios of the observable values in each V0M class with respect to those in V0M class I are represented in the bottom insets. Results are presented as a function of the $\Dzero$-meson $\pt$, for $\ptass>$ 0.3~\GeVc. Statistical and systematic uncertainties are shown as vertical error bars and boxes, respectively.

Figure 6

Near-side associated peak yields (top row) and widths (third row down) in pp collisions at $\sqrt{s}$ = 13~TeV, compared with predictions by PYTHIA, POWHEG+PYTHIA8, HERWIG, and EPOS 3 event generators with various configurations. Results are presented as a function of the D-meson $\pt$, for $\ptass>$ 0.3~\GeVc, $0.3

Figure 7

Away-side associated peak yields (top row) and widths (third row down) in pp collisions at $\sqrt{s}$ = 13~TeV, compared with predictions by PYTHIA, POWHEG+PYTHIA8, HERWIG, and EPOS 3 event generators with various configurations. Results are presented as a function of the D-meson $\pt$, for $\ptass>$ 0.3~\GeVc, $0.3

Figure 8

Near- and away-side peak yields (first column), widths (second column), near-side peak $\beta$ parameter and baseline (third column) from fits to the D-meson and charged particle azimuthal-correlation function, from PYTHIA8 simulations obtained with different parton-level contributions. The predictions are obtained for multiplicity-integrated \pp collisions at $\s = 13$ \TeV, as a function of the D-meson $\pt$, for $\ptass > 0.3$ \GeVc, and compared with ALICE data.

Figure 9

Near- and away-side peak yields (first column), widths (second column), near-side peak $\beta$ parameter and baseline (third column) from fits to the D-meson and charged particle azimuthal-correlation function, from POWHEG+PYTHIA8 simulations obtained with different parton-level contributions. The predictions are obtained for multiplicity-integrated in \pp collisions at $\s = 13$ \TeV, as a function of the D-meson $\pt$, for $\ptass > 0.3$ \GeVc, and compared with ALICE data.

Figure 10

Azimuthal-correlation function of D mesons with charged particles with different parton-level contributions from PYTHIA8 (left panel) and POWHEG+PYTHIA8 simulations (right panel) in pp collisions at $\s = 13$~\TeV, for $0.3

Figure 11

Azimuthal-correlation function of D mesons with charged particles with different parton-level contributions from PYTHIA8 (left panel) and POWHEG+PYTHIA8 simulations (right panel) in pp collisions at $\s = 13$~TeV, for $2