Predictions for Cold Nuclear Matter Effects in $p+$Pb Collisions at $\sqrt{s_{_{NN}}} = 8.16$ TeV

Abstract

Predictions for cold nuclear matter effects on charged hadrons, identified light hadrons, quarkonium and heavy flavor hadrons, Drell-Yan dileptons, jets, photons, gauge bosons and top quarks produced in $p+$Pb collisions at $\sqrt{s_{_{NN}}} = 8.16$ TeV are compiled and, where possible, compared to each other. Predictions of the normalized ratios of $p+$Pb to $p+p$ cross sections are also presented for most of the observables, providing new insights into the expected role of cold nuclear matter effects. In particular, the role of nuclear parton distribution functions on particle production can now be probed over a wider range of phase space than ever before.

Figures (44)

• Figure 1: (Color online) The charged particle multiplicity distribution $dN_{\rm ch}/d\eta$ at $\sqrt{s_{NN}} = 8$ TeV from $\mathtt{AMPT}$ (solid blue), rcBK from Albacete and Dumitru (black dot dashed), bCGC from Rezaeian (blue dashed), and $\mathtt{HIJING++}$ (dashed red) in the laboratory (a) and center-of-mass (b) frames. The $\mathtt{AMPT}$ result is in the lab frame while the $\mathtt{HIJING++}$ calculation and the rcBK result from Albacete and Dumitru are given in both frames.
• Figure 2: (Color online) The IP-Glasma prediction for the charged hadron multiplicity distribution in $p+p$ collisions at 7 TeV (a) and $p+$Pb collisions at 5.02 and 8 TeV (b) are shown. The ALICE data for $|\eta| < 1$ in 7 TeV $p+p$ collisions Aamodt:2010pp and the CMS data for $|\eta|<2.4$ in 5.02 TeV $p+$Pb collisions CMS:2012qk are shown in red. The corresponding IP-Glasma calculations are shown in black while the 8 TeV $p+$Pb predictions are given in blue.
• Figure 3: (Color online) The charged hadron multiplicity, $dN_{\rm ch}/d\eta$, in 8 TeV $p+$Pb collisions at different centralities calculated with $\mathtt{AMPT-SM}$ are shown. The result for all non-diffractive events at 5 TeV (red points and line) is also shown for comparison. The blue lines, from top to bottom are for centralities of (0-1)%, (1-5)%, (5-10)%, (10-20)%, (20-30)%, (30-40)%, (40-60)%, (60-90)% and (90-100)%. The blue points and line shows the 8 TeV non-diffractive multiplicity. The 8 TeV non-diffractive multiplicity is very similar to the calculation in the (40-60)% centrality bin. The results in (a) are for the ATLAS centrality definition, $\langle E_T \rangle(-4.9 < \eta_{\rm lab} < -3.1)$Aad:2015zza, while the results in (b) use the centrality definition based on charged particle multiplicity in the central region $\langle N_{\rm ch} \rangle(|\eta_{\rm lab}|<2.4)$.
• Figure 4: (Color online) The charged hadron multiplicity distribution, $dN_{\rm ch}/d\eta$, in 5 TeV $p+$Pb collisions at different centralities from $\mathtt{AMPT-SM}$ are shown in the laboratory frame. The previous prediction for minimum-bias events at 5 TeV (cyan points and line) is shown for comparison. The blue lines, from top to bottom are for centralities of (0-1)%, (1-5)%, (5-10)%, (10-20)%, (20-30)%, (30-40)%, (40-60)%, (60-90)% and (90-100)%. The red points and line shows the previous $\mathtt{AMPT}$ result for the 5 TeV non-diffractive multiplicity. The red and cyan curves are somewhat different in shape but similar in magnitude. The results in are for the ATLAS centrality definition, $\langle E_T \rangle(-4.9 < \eta_{\rm lab} < -3.1)$Aad:2015zza.
• Figure 5: (Color online) The new $\mathtt{AMPT-SM}$ charged hadron multiplicity distribution, $dN_{\rm ch}/d\eta$, at 5 TeV (in blue) is compared to the ATLAS data (black points) Aad:2015zza in the same centrality bins: (0-1)%, (1-5)%, (5-10)%, (10-20)%, (20-30)%, (30-40)%, (40-60)% and (60-90)%.