Measurement of the production of charm jets tagged with D0 mesons in pp collisions at $$ \sqrt{s} $$ = 5.02 and 13 TeV

Abstract

The measurement of the production of charm jets, identified by the presence of a D0 meson in the jet constituents, is presented in proton–proton collisions at centre-of-mass energies of $$ \sqrt{s} $$ s = 5.02 and 13 TeV with the ALICE detector at the CERN LHC. The D0 mesons were reconstructed from their hadronic decay D0 → K−π+ and the respective charge conjugate. Jets were reconstructed from D0-meson candidates and charged particles using the anti-kT algorithm, in the jet transverse momentum range 5 < pT,chjet< 50 GeV/c, pseudorapidity |ηjet| < 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 D0 meson along the jet axis $$ \left({z}_{\Big\Vert}^{\textrm{ch}}\right) $$ z ‖ ch was measured in the range 0.4 <$$ {z}_{\Big\Vert}^{\textrm{ch}} $$ z ‖ 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 pT,chjet. Measurements were also done for R = 0.3 at $$ \sqrt{s} $$ s = 5.02 and are shown along with their comparisons to theoretical predictions in an appendix to this paper.

Hadronization mechanism (via heavy-flavor hadrons): Experiment

“…A softer 𝑧 ch | | distribution can be related to a smaller hadron jet-energy fraction or a smaller alignment of the hadron and jet momentum vectors, both aspects sensitive to a possible interplay with the underlying event. The Λ + c -jet measured trend contrasts with that expected by the default version of pythia8 (Monash tune), which reasonably describes D-meson tagged jets [42] and reflects the tendency in jet fragmentation for heavier particles to carry a larger fraction of jet momentum, while it agrees with that expected by the tune of pythia8 with CR BLC. A related, study is that of the azimuthal correlation of Λ + c baryons with charged particles produced in the event.…”

Characterization of heavy-quark fragmentation via jets and correlations with ALICE

“…As discussed in Ref. [1] the 𝑝 T,ch jet -differential cross section and 𝑧 ch | | -differential yield of jets containing a prompt D 0 meson is well described by the PYTHIA 8 Soft QCD Mode 2 [8,9] and the POWHEG+PYTHIA 8 [8,10] within the uncertainties. In the case of Λ + c -tagged jets, the 𝑧 ch | | distribution [11] was studied for 7 ≤ 𝑝 T,ch jet < 15 GeV/𝑐, and shows a good agreement with PYTHIA 8 CR-BLC Mode2, as shown in the left panel of Fig 2 . The comparison of 𝑧 ch | | between the Λ + c baryon and D 0 meson shows a hint of a softer fragmentation for the c → Λ + c case with respect to c → D 0 case.…”

“…The mass of heavy quarks is larger than the non-perturbative QCD scale (Λ QCD ), and the hard parton scattering cross section can be evaluated perturbatively. Therefore, studies of heavyflavour hadron production provide the necessary inputs to test and constrain perturbative QCD calculations [1]. The production cross section for a heavy-flavour hadron (H Q ) can be calculated using the factorization approach [2]:…”