Deuteron coalescence probability in jets in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV

Abstract

This article presents the first measurement of the (anti)deuteron and antiproton transverse-momentum distributions, the deuteron coalescence parameter, and the ratio between the yields of deuteron and proton in and out of jets in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV. Three regions are used to study the jet-correlated production: Toward, Away, and Transverse to the jet axis, which direction is approximated by the leading particle in the event with $p_{\rm T}^{\rm lead} > 5$ GeV/$c$. The jet contribution is obtained from the Toward region by subtracting the underlying event, which dominates the Transverse region. In p-Pb collisions, an enhancement of the coalescence parameter $B_{\rm 2}$ is observed in jets compared to the underlying event. The enhancement is larger than the one observed in a similar analysis already in pp collisions. The results are compared with predictions from PYTHIA 8.314 using the Angantyr model with a deuteron production model based on ordinary nuclear reactions. The model is able to qualitatively reproduce the large enhancement of the coalescence parameter in jets with respect to the out-of-jets one. The results are further compared in detail with similar ones from previous studies for pp collisions at $\sqrt{s} = 13$ TeV.

Figures (5)

• Figure 1: The average of deuteron and antideuteron (top row) and antiproton (bottom row) $p_{\rm T}$ -differential yields in the three azimuthal regions (left) and in jets (right) measured in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeemV. Statistical and systematical uncertainties are reported, respectively, with vertical lines and boxes. Individual Lévy-Tsallis fits are also shown. The distributions are scaled for visibility reasons. The bottom panel of each figure shows the ratio of the distribution with respect to the Toward one.
• Figure 2: The coalescence parameter in jets $B_{\mathrm{2}}^{\mathrm{jet}}$ and in the underlying event $B_{\mathrm{2}}^{\mathrm{UE}}$ as a function of the per nucleon transverse momentum $p_{\rm T}$/$A$ (here, $A = 2$) in pp collisions at $\sqrt{s}~=~13$ TeemV, taken from ALICE_pp_B2_jet, and p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeemV. Statistical and systematic uncertainties are represented, respectively, by vertical bars and boxes.
• Figure 3: The coalescence parameter in jets $B_{\mathrm{2}}^{\mathrm{jet}}$ and in the underlying event $B_{\mathrm{2}}^{\mathrm{UE}}$ in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeemV as a function of $p_{\rm T}$/$A$ compared with the model prediction given by PYTHIA 8.314 with Angantyr.
• Figure 4: Top: The deuteron-to-proton yield ratio in pp collisions at $\sqrt{s}~=~13$ TeemV ALICE_pp_B2_jetALICE_proton_RT (left) and p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeemV (right) in jets and in the underlying event. Bottom: The double ratio $(\mathrm{d/p})_{\mathrm{in-jet}}/(\mathrm{d/p})_{\mathrm{UE}}$ in pp collisions at $\sqrt{s}~=~13$ TeemV (left) and p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeemV (right). Statistical and systematic uncertainties are represented, respectively, by vertical bars and boxes.
• Figure 5: Top: The deuteron-to-proton yield ratio in jets (left) and in the underlying event (right) in pp collisions at $\sqrt{s}~=~13$ TeemV ALICE_pp_B2_jetALICE_proton_RT and p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeemV (right). Statistical and systematic uncertainties are represented, respectively, by vertical bars and boxes. Bottom: The double ratio $(\mathrm{d/p})_{\hbox{p--Pb}\xspace}/(\mathrm{d/p})_{\mathrm{pp}}$ in jets (left) and in the underlying event (right). The band represents the statistical and systematic uncertainties summed in quadrature.