Measurement of the charged-particle-jet transverse-momentum fraction carried by prompt and non-prompt J/$\psi$ mesons in pp collisions at $\sqrt{s}=13$ TeV

Abstract

The measurement of the transverse-momentum fraction ($z^{\mathrm{ch}}$) carried by prompt and non-prompt J/$\psi$ in charged-particle jets in proton--proton collisions with a center-of-mass energy $\sqrt{s}=13$ TeV is reported by the ALICE Collaboration at the CERN Large Hadron Collider. The measurement is based on a Transition Radiation Detector triggered data sample corresponding to an integrated luminosity of $\mathcal{L}=1.63\pm 0.03$ pb${}^{-1}$. Inclusive J/$\psi$ mesons with transverse momentum ($p_{\mathrm{T}}$) above 1 GeV/$c$ are reconstructed at midrapidity through the electron--positron decay channel. The prompt and non-prompt J/$\psi$ contributions are separated using the secondary vertices from beauty-hadron decays. Jets are reconstructed from J/$\psi$-meson candidates and charged particles using the anti-$k_{\mathrm{T}}$ algorithm with jet resolution parameter $R=0.4$ in the pseudorapidity range $|{\eta }_{\text{jet}}|<0.5$. The distribution of the charged-particle jet $p_{\mathrm{T}}$ fraction carried by the prompt and non-prompt J/$\psi$ mesons, $z^{\mathrm{ch}}$, is measured in the range $0.3<z^{\mathrm{ch}}\le 1.0$ for the jet-$p_{\mathrm{T}}$ range $7<p_{\mathrm{T}}^{\mathrm{jet}}<15$ GeV/$c$. The measured $z^{\mathrm{ch}}$ distributions for prompt and non-prompt J/$\psi$ are compared to pQCD calculations and PYTHIA 8 simulations. Prompt and non-prompt J/$\psi$ production within charged-particle jets are found to be qualitatively well reproduced by PYTHIA 8 for $z^{\mathrm{ch}}<0.9$, however, as $z^{\mathrm{ch}}$ approaches one, the simulations overshoot the measured data, indicating an overestimation of the fraction of isolated J/$\psi$. This observed tension between data and simulations in the highest $z^{\mathrm{ch}}$ bins reflects the challenge of simulating hadronization of low-momentum jets.

26 pages, 5 captioned figures, 3 tables, authors from page 21, submitted to JHEP, figures at http://alice-publications.web.cern.ch/node/13116