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Predictions for $p+$Pb Collisions at $\sqrt{s_{NN}} = 5$ TeV: Comparison with Data

J. L. Albacete, F. Arleo, G. G. Barnafoldi, J. Barrette, W. -T. Deng, A. Dumitru, K. J. Eskola, E. G. Ferreiro, F. Fleuret, H. Fujii, M. Gyulassy, S. M. Harangozi, I. Helenius, Z. Kang, P. Kotko, K. Kutak, J. -P. Lansberg, P. Levai, Z. -W. Lin, Y. Nara, A. Rakotozafindrabe, G. Papp, H. Paukkunen, S. Peigne, M. Petrovici, J. -W. Qiu, A. H. Rezaeian, P. Ru, S. Sapeta, V. Topor Pop, I. Vitev, R. Vogt, E. Wang, X. -N. Wang, H. Xing, R. Xu, B. -W. Zhang, W. -N. Zhang

TL;DR

The paper systematically tests Albacete et al.'s 5.02 TeV $p+$Pb predictions against data, using CGC/rcBK and collinear-factorization frameworks to predict charged particles, jets, quarkonia, and gauge bosons. It highlights where saturation effects and cold nuclear matter modify observables such as $dN_{ch}/d\eta$, $R_{pA}$, jet $R_{pPb}$, quarkonium suppression via comovers and shadowing, and vector-boson rapidity distributions. Overall, many predictions align with data, especially in midrapidity and forward regions, while some tensions remain (notably high-$p_T$ $R_{pPb}$ and forward-backward asymmetries), underscoring the need for improved baseline measurements and refined nPDF constraints. The study demonstrates the complementary roles of saturation physics and CNM effects in interpreting LHC $p+$Pb results and informs future explorations of small-$x$ dynamics and quarkonium interactions in nuclear environments.

Abstract

Predictions made in Albacete {\it et al} prior to the LHC $p+$Pb run at $\sqrt{s_{NN}} = 5$ TeV are compared to currently available data. Some predictions shown here have been updated by including the same experimental cuts as the data. Some additional predictions are also presented, especially for quarkonia, that were provided to the experiments before the data were made public but were too late for the original publication are also shown here.

Predictions for $p+$Pb Collisions at $\sqrt{s_{NN}} = 5$ TeV: Comparison with Data

TL;DR

The paper systematically tests Albacete et al.'s 5.02 TeV Pb predictions against data, using CGC/rcBK and collinear-factorization frameworks to predict charged particles, jets, quarkonia, and gauge bosons. It highlights where saturation effects and cold nuclear matter modify observables such as , , jet , quarkonium suppression via comovers and shadowing, and vector-boson rapidity distributions. Overall, many predictions align with data, especially in midrapidity and forward regions, while some tensions remain (notably high- and forward-backward asymmetries), underscoring the need for improved baseline measurements and refined nPDF constraints. The study demonstrates the complementary roles of saturation physics and CNM effects in interpreting LHC Pb results and informs future explorations of small- dynamics and quarkonium interactions in nuclear environments.

Abstract

Predictions made in Albacete {\it et al} prior to the LHC Pb run at TeV are compared to currently available data. Some predictions shown here have been updated by including the same experimental cuts as the data. Some additional predictions are also presented, especially for quarkonia, that were provided to the experiments before the data were made public but were too late for the original publication are also shown here.

Paper Structure

This paper contains 29 sections, 16 equations, 35 figures, 1 table.

Table of Contents

  1. Introduction
  2. Charged particles
  3. Multiplicity distribution (J. Albacete, A. Drumitru and A. Rezaeian)
  4. Centrality dependence of $dN_{\rm ch}/d\eta$ (Z. Lin and A. Rezaeian)
  5. Transverse momentum distribution (J. Albacete, G. G. Barnaföldi, J. Barette, W.-T. Deng, A. Dumitru, H. Fujii, M. Gyulassy, P. Levai, Z. Lin, Y. Nara, M. Petrovici, V. Topor Pop, X.-N. Wang, and R. Xu)
  6. Average transverse momentum (A. Rezaeian)
  7. Nuclear modification factor (K. J. Eskola, I. Helenius, H. Paukkunen and A. Rezaeian
  8. rcBK (A. Rezaeian)
  9. Minimum-bias charged-hadron production in $p+$Pb collisions: Collinear factorization (K. J. Eskola, I. Helenius and H. Paukkunen)
  10. Forward-backward asymmetry (G. G. Barnaföldi, J.Barette, S. M. Harangozó, M. Gyulassy, P. Levai, Z. Lin, G. Papp and V. Topor Pop)
  11. Flow (Z. Lin)
  12. Jets
  13. Minimum-bias dijets in $p+$Pb collisions (K. J. Eskola, I. Helenius and H. Paukkunen)
  14. Single inclusive jet production (Z.-B. Kang, I. Vitev and H. Xing)
  15. Nuclear modification ratio for production of forward-forward jets in $p+$Pb collisions with Sudakov effects included (P. Kotko, K. Kutak and S. Sapeta)
  16. ...and 14 more sections

Figures (35)

  • Figure 1: (Color online) The ALICE charged particle pseudorapidity distribution in minimum-bias $p+$Pb collisions at $\sqrt{s_{_{NN}}}=5.02$ TeV ALICE:2012xs. The b-CGC curves are based on leading log $k_T$-factorization and the b-CGC saturation model. The results are obtained for $m_{\rm jet} =1$, 5, and 10 MeV. The plot is taken from Ref. [ ?].
  • Figure 2: (Color online) Charged particle pseudorapidity distribution at $\sqrt{s_{_{NN}}}= 5.02$ TeV as a function of $\eta$ with and without the adjusted Jacobian, calculated by Albacete and Dumitru.
  • Figure 3: (Color online) The charged particle pseudorapidity distributions in the ATLAS centrality bins Aad:2015zza compared to calculations based on leading log $k_t$-factorization in the b-CGC saturation model. The central value of the calculation is for $m_{\rm jet} = 5$ MeV. From top down the centrality bins are: (1-5)%, (5-10)%, (10-20)%, (20-30)%, (30-40)%, (40-60)%, and (60-90)%. There is no additional scaling, neither on the data nor the calculations. See Ref. [ ?] for details of the calculation.
  • Figure 4: (Color online) The charged particle pseudorapidity distributions in the ATLAS centrality bins Aad:2015zza compared to $\mathtt{AMPT}$ calculations. From top down the centrality bins are: (0-1)%, (1-5)%, (5-10)%, (10-20)%, (20-30)%, (30-40)%, (40-60)%, and (60-90)%. There is no additional scaling, neither on the data nor the calculations.
  • Figure 5: (Color online) Charged particle $p_T$ distributions at $\sqrt{s_{_{NN}}} = 5.02$ TeV. The solid and dashed cyan curves outline the rcBK band Albacete:2012xq. The magenta curves, calculated with $\mathtt{HIJINGB\overline{B}2.0}$ are presented without (dot-dashed) and with (dotted) shadowing. The $\mathtt{AMPT}$ results are given by the dot-dash-dash-dashed (default) and dot-dot-dot-dashed (SM) blue curves. The data are from the ALICE ALICE:2012mj (left) and CMS CMS:2013cka (right) Collaborations. All the calculations were presented in Ref. [ ?].
  • ...and 30 more figures