Multiplicity Dependence of Pion, Kaon, Proton and Lambda Production in p-Pb Collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV

ALICE Collaboration

In this Letter, comprehensive results on ${\rm\pi}^\pm$, K$^\pm$, K$^0_S$, p, $\rm\bar{p}$, $\rm \Lambda$ and $\rm \bar{\Lambda}$ production at mid-rapidity ($0 < y_{\rm cms} < 0.5$) in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV, measured by the ALICE detector at the LHC, are reported. The transverse momentum distributions exhibit a hardening as a function of event multiplicity, which is stronger for heavier particles. This behavior is similar to what has been observed in pp and Pb-Pb collisions at the LHC. The measured $p_{\rm T}$ distributions are compared to results at lower energy and with predictions based on QCD-inspired and hydrodynamic models.

Figures

Figure 1

Invariant $\pt$-differential yields of pions, kaons, protons, $\Lambda$s and K$^0_{\rm S}$ in different V0A multiplicity classes (sum of particle and antiparticle states where relevant) measured in the rapidity interval $0< y_{\rm cms}< 0.5$.
Top to bottom: central to peripheral; data scaled by $2^{n}$ factors for better visibility. Statistical (bars) and full systematic (boxes) uncertainties are plotted. Dashed curves: blast-wave fits to each individual distribution.
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Figure 2

Ratios of kaons to pions, protons to pions, and $\Lambda$s to K$^0_{\rm S}$ as a function of $\pt$ in two multiplicity bins measured in the rapidity interval $0< y_{\rm cms}< 0.5$ (left panels). The ratios are compared to results in Pb-Pb collisions measured at midrapidity, shown in the right panels. The empty boxes show the total systematic uncertainty; the shaded boxes indicate the contribution uncorrelated across multiplicity bins (not estimated in Pb-Pb).
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Figure 3

Proton to pion ratio as a function of the charged-particle density $\dNdeta$ in three $\pt$ intervals in p-Pb (measured in the rapidity interval $0< y_{\rm cms}< 0.5$) and Pb-Pb collisions (measured at midrapidity). The dashed lines show the corresponding power-law fit (top).
Exponent of the proton to pion (middle) and $\Lambda$ to K$^0_{\rm S}$ (bottom) power-law fit as a function of $\pt$ in p-Pb and Pb-Pb collisions. The empty boxes show the total systematic uncertainty; the shaded boxes indicate the contribution uncorrelated across multiplicity bins (not estimated in Pb-Pb).
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Figure 4

Mean transverse momentum as a function of $\dNdeta$ in each V0A multiplicity class (see text for details) for different particle species measured in the rapidity interval $0< y_{\rm cms}< 0.5$. The $\dNdeta$ values of K$^0_{\rm S}$ are shifted for visibility. The empty boxes show the total systematic uncertainty; the shaded boxes indicate the contribution uncorrelated across multiplicity bins (not estimated in Pb-Pb).
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Figure 5

Particle yields d$N$/d$y$ of kaons, protons, and $\Lambda$s normalized to pions as a function of $\dNdeta$ in each V0A multiplicity class (see text for details) measured in the rapidity interval $0< y_{\rm cms}< 0.5$. The values are compared to results obtained from Pb-Pb collisions at the LHC and Au-Au and d-Au collisions at RHIC measured at midrapidity. The empty boxes show the total systematic uncertainty; the shaded boxes indicate the contribution uncorrelated across multiplicity bins (not estimated in Pb-Pb).
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Figure 6

Results of blast-wave fits, compared to Pb-Pb data and MC simulations from PYTHIA8 with and without color reconnection. Charged-particle multiplicity increases from left to right. Uncertainties from the global fit are shown as correlation ellipses.
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Figure 7

Pion, kaon, and proton transverse momentum distributions in the 5-10% V0A multiplicity class measured in the rapidity interval $0< y_{\rm cms}< 0.5$ compared to the several models (see text for details).
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