Measurement of the production of charm jets tagged with ${\rm D^0}$ mesons in pp collisions at $\sqrt{s}$ = 5.02 and 13 TeV

The measurement of the production of charm jets, identified by the presence of a ${\rm D^0}$ meson in the jet constituents, is presented in proton-proton collisions at centre-of-mass energies of $\sqrt{s}$ = 5.02 and 13 TeV with the ALICE detector at the CERN LHC. The ${\rm D^0}$ mesons were reconstructed from their hadronic decay ${\rm D^0} \rightarrow {\rm K^-}\pi^+$ and the respective charge conjugate. Jets were reconstructed from ${\rm D^0}$-meson candidates and charged particles using the anti-$k_{\rm T}$ algorithm, in the jet transverse momentum range $5<~p_{\rm T;chjet}<~50$ GeV/$c$, pseudorapidity $|\eta_{\rm jet}| <~0.9-R$, and with the jet resolution parameters $R$ = 0.2, 0.4, 0.6. The distribution of the jet momentum fraction carried by a ${\rm D^0}$ meson along the jet axis ($z^{\rm ch}_{||}$) was measured in the range $0.4 <~ z^{\rm ch}_{||} <~ 1.0$ in four ranges of the jet transverse momentum. Comparisons of results for different collision energies and jet resolution parameters are also presented. The measurements are compared to predictions from Monte Carlo event generators based on leading-order and next-to-leading-order perturbative quantum chromodynamics calculations. A generally good description of the main features of the data is obtained in spite of a few discrepancies at low $p_{\rm T;chjet}$. Measurements were also done for $R = 0.3$ at $\sqrt{s}$ = 5.02 TeV and are shown along with their comparisons to theoretical predictions in an appendix to this paper.

 

Submitted to: JHEP
e-Print: arXiv:2204.10167 | PDF | inSPIRE
Figure group

Figure 1

Top: invariant mass distributions of D0-jet candidates for 2 < pT,ch jet < 50 GeV/c and R = 0.4 in pp collisions at √s = 5.02 TeV, in the D0-meson transverse momentum intervals: 3 < pT,D0 < 4 GeV/c (left), 7 < pT,D0 < 8 GeV/c (centre), and 10 < pT,D0 < 12 GeV/c (right). The total fit function is represented by the blue solid line, while the red dashed line represents the sum of the background and reflection fit functions. The red and green shaded areas correspond to the peak and sideband regions, respectively. Bottom: D0-jet raw yields as a function of pT,ch jet in the signal and sideband regions, and their subtracted yields.

Figure 2

Top: invariant mass distribution of D0-jet candidates for one jet-pT interval of 5 < pT,ch jet < 7 GeV/c and R = 0.4 in pp collisions at √s = 5.02 TeV, in D0-meson transverse momentum intervals: 3 < pT,D0 < 4 GeV/c (left), 4 < pT,D0 < 5 GeV/c (centre), and 5 < pT,D0 < 6 GeV/c (right). The total fit function is represented by the blue solid line, while the red dashed line represents the background fit function. The red and green shaded areas correspond to the peak and sideband regions, respectively. Bottom: D0-jet raw yields as a function of zch || in the signal and sideband regions, and their subtracted yields.

Figure 3

Product of acceptance and efficiency, Acc × ε, for D0-jet reconstruction as a function of pT,D0 with R = 0.4 in pp collisions at √s = 5.02 TeV. Left: Acc × ε for prompt and non-prompt D0 jets in the range 5 < pT,ch jet < 50 GeV/c. Right: Acc × ε for prompt D0 jets in different jet-pT intervals.

Figure 4

Feed-down fraction of D0 jets from b-hadrons in pp collisions at √s = 5.02 TeV for R = 0.4 as a function of pT,ch jet in 5 < pT,ch jet < 50 GeV/c (left) and as a function of zch || in two pT,ch jet intervals 5 < pT,ch jet < 7 GeV/c and 15 < pT,ch jet < 50 GeV/c (right).

Figure 5

Left: detector response matrix of matched jets used for unfolding the pT,ch jet distribution with R = 0.4 in pp collisions at √s = 5.02 TeV in the range 2 < pT,ch jet < 50 GeV/c. Right: pT,ch jet resolution, ∆p, for 5 < ppart T,ch jet < 6 GeV/c, 10 < ppart T,ch jet < 12 GeV/c, and 20 < ppart T,ch jet < 30 GeV/c.

Figure 6

Left: detector response matrix of matched jets used for unfolding zch || distribution with R = 0.4 in pp collisions at √s = 5.02 TeV in the range 2 < pT,ch jet < 50 GeV/c and 0.4 < zch || < 1. Right: zch || resolution, ∆z, in the zch,part || intervals 0.4–0.6, 0.6–0.8, and 0.8–1 for the pT,ch jet interval 5 < ppart T,ch jet < 7 GeV/c

Figure 7

Top panels: \ptchjet-differential cross section of charm jets tagged with \Dzero mesons for $R=0.2$ (circles, scaled by 0.1), $0.4$ (squares) and $0.6$ (crosses, scaled by 10) in \pp collisions at \thirteen (left) and \five (right) compared to PYTHIA~8 HardQCD Monash~2013 (dash-dotted lines), PYTHIA~8 SoftQCD Mode 2 (dashed lines), and POWHEG hvq + PYTHIA~8 (open circles) predictions. The shaded bands indicate the systematic uncertainty on the data cross section while open boxes represent the theoretical uncertainties on the POWHEG predictions. Bottom panels: ratios of MC predictions to the data for $R=0.2$, $0.4$ and $0.6$.

Figure 8

Top: ratios of \ptchjet-differential cross section of charm jets tagged with \Dzero mesons in \pp collisions at \thirteen to \five for $R=0.2$ (left), $R=0.4$ (centre), and $R=0.6$ (right) compared to PYTHIA~8 HardQCD Monash~2013 (dash-dotted lines), PYTHIA~8 SoftQCD Mode 2 (dashed lines), and POWHEG hvq + PYTHIA~8 (open circles) predictions. The shaded bands indicate the systematic uncertainty on the cross section ratios while open boxes represent the theoretical uncertainties on the POWHEG predictions. Bottom: ratios of MC predictions to the data

Figure 9

Top: ratios of \ptchjet-differential cross section of charm jets tagged with \Dzero mesons for different $R$: $\sigma(R=0.2)/\sigma(R=0.4)$ (circles, shifted up by 0.5) and $\sigma(R=0.2)/\sigma(R=0.6)$ (squares) in \pp collisions at \thirteen~(left) and \five~(right) compared to PYTHIA~8 HardQCD Monash~2013 (dash-dotted lines), PYTHIA~8 SoftQCD Mode 2 (dashed lines), and POWHEG hvq + PYTHIA~8 (open circles) predictions. The shaded bands indicate the systematic uncertainty on the cross section ratios while open boxes represent the theoretical uncertainties on the POWHEG predictions Bottom: ratios of MC predictions to the data for \mbox{$\sigma(R=0.2)/\sigma(R=0.4)$} and \mbox{$\sigma(R=0.2)/\sigma(R=0.6)$}, respectively

Figure 10

The fraction of \Dzero jets over inclusive charged-particle jets in \pp collisions at \five for \mbox{(a)~$R = 0.2$}, (b)~$R = 0.4$, and (c)~$R = 0.6$ compared to PYTHIA~8 HardQCD Monash~2013 (dash-dotted lines) and POWHEG hvq + PYTHIA~8 (open circles) predictions. The shaded bands indicate the systematic uncertainty on the data cross section ratios while the open boxes represent the theoretical uncertainties on the POWHEG predictions

Figure 11

Distributions of zch || -differential yield of charm jets tagged with D0 mesons normalised by the number of D0 jets within each distribution in pp collisions at √s = 13 TeV in four jet-pT intervals 5 < pT,ch jet < 7 GeV/c, 7 < pT,ch jet < 10 GeV/c, 10 < pT,ch jet < 15 GeV/c, and 15 < pT,ch jet < 50 GeV/c from left to right, respectively. Top, middle, and bottom rows represent jets with R = 0.2, 0.4, and 0.6, respectively. They are compared to PYTHIA 8 HardQCD Monash 2013 (dash-dotted lines), PYTHIA 8 SoftQCD Mode 2 (dashed lines), and POWHEG hvq + PYTHIA 8 (open circles) predictions. The shaded bands indicate the systematic uncertainty on the distributions. Bottom panels present ratios of MC predictions to the data.

Figure 12

Distributions of zch || -differential yield of charm jets tagged with D0 mesons and normalised by the number of D0 jets within each distribution in pp collisions at √s = 5.02 TeV in four pT,ch jet intervals 5 < pT,ch jet < 7 GeV/c, 7 < pT,ch jet < 10 GeV/c, 10 < pT,ch jet < 15 GeV/c, and 15 < pT,ch jet < 50 GeV/c from left to right, respectively. Top, middle, and bottom rows represent jets with R = 0.2, 0.4, and 0.6, respectively. They are compared to PYTHIA 8 HardQCD Monash 2013 (dash-dotted lines), PYTHIA 8 SoftQCD Mode 2 (dashed lines), and POWHEG hvq + PYTHIA 8 (open circles) predictions. The shaded bands indicate the system- atic uncertainty on the distributions. Bottom panels present ratios of MC predictions to the data.

Figure 13

Top panel: \ptchjet-differential cross section of charm jets tagged with \Dzero mesons for $R=0.3$ in \pp collisions at \five compared to PYTHIA~8 HardQCD Monash~2013 (dash-dotted lines), PYTHIA~8 Monash~2013 SoftQCD Mode 2 (dashed lines) and POWHEG hvq + PYTHIA~8 (open circles) predictions. The shaded bands indicate the systematic uncertainty on the data cross section while open boxes represent the theoretical uncertainties on the POWHEG predictions. Bottom panel presents ratios of MC predictions to the data.

Figure 14

The fraction of \Dzero jets over inclusive charged-particle jets in \pp collisions at \five for \mbox{$R = 0.3$} compared to PYTHIA~8 HardQCD Monash~2013 (dash-dotted lines) and POWHEG hvq + PYTHIA~8 (open circles) predictions

Figure 15

Top panels: zch || -differential yield of R = 0.3 charm jets tagged with D0 mesons normalised by the number of D0 jets within each distribution in pp collisions at √s = 5.02 TeV in four pT,ch jet intervals (top left) 5 < pT,ch jet < 7 GeV/c, (top right) 7 < pT,ch jet < 10 GeV/c, (bottom left) 10 < pT,ch jet < 15 GeV/c and (bottom right) 15 < pT,ch jet < 50 GeV/c GeV/c. They are compared to PYTHIA 8 Monash 2013 (dashed-dotted lines), PYTHIA 8 Monash 2013 SoftQCD Mode 2 (dashed lines) and POWHEG hvq + PYTHIA 8 (open circles) predictions. The shaded bands indicate the systematic uncertainty on the distributions while open boxes represent the theoretical uncertainties on the POWHEG predictions. Bottom panels present ratios of MC predictions to the data