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Progress in Double Parton Scattering Studies

Sunil Bansal, Paolo Bartalini, Boris Blok, Diego Ciangottini, Markus Diehl, Fiorella M. Fionda, Jonathan R. Gaunt, Paolo Gunnellini, Tristan Du Pree, Tomas Kasemets, Daniel Ostermeier, Sergio Scopetta, Andrzej Siódmok, Alexander M. Snigirev, Antoni Szczurek, Daniele Treleani, Wouter J. Waalewijn

TL;DR

Progress in Double Parton Scattering studies surveys both theory and experiment on DPS at the LHC and beyond. Theoretical sections analyze factorization, double parton distributions, and the role of correlations, evolution, and nuclear effects in DPS. Phenomenology sections summarize CMS and ALICE measurements of W+2 jets, V+bb, double J/psi, 4-jet final states, and charm multiplicities, highlighting significant DPS contributions and guiding modeling efforts. The work emphasizes non-universality of sigma_eff across processes and energies, and identifies HE-LHC/HL-LHC as promising avenues to probe extreme kinematic regimes and heavy-boson DPS final states.

Abstract

An overview of theoretical and experimental progress in double parton scattering (DPS) is presented. The theoretical topics cover factorization in DPS, models for double parton distributions and DPS in charm production and nuclear collisions. On the experimental side, CMS results for dijet and double J/ψ production, in light of DPS, as well as first results for the 4-jet channel are presented. ALICE reports on a study of open charm and J/ψ multiplicity dependence.

Progress in Double Parton Scattering Studies

TL;DR

Progress in Double Parton Scattering studies surveys both theory and experiment on DPS at the LHC and beyond. Theoretical sections analyze factorization, double parton distributions, and the role of correlations, evolution, and nuclear effects in DPS. Phenomenology sections summarize CMS and ALICE measurements of W+2 jets, V+bb, double J/psi, 4-jet final states, and charm multiplicities, highlighting significant DPS contributions and guiding modeling efforts. The work emphasizes non-universality of sigma_eff across processes and energies, and identifies HE-LHC/HL-LHC as promising avenues to probe extreme kinematic regimes and heavy-boson DPS final states.

Abstract

An overview of theoretical and experimental progress in double parton scattering (DPS) is presented. The theoretical topics cover factorization in DPS, models for double parton distributions and DPS in charm production and nuclear collisions. On the experimental side, CMS results for dijet and double J/ψ production, in light of DPS, as well as first results for the 4-jet channel are presented. ALICE reports on a study of open charm and J/ψ multiplicity dependence.

Paper Structure

This paper contains 13 sections, 1 equation, 3 figures.

Table of Contents

  1. Progress in the Theory of Double Parton Scattering
  2. Introduction
  3. Progress in Factorization
  4. Correlations in Proton Models
  5. Charm Cross Sections
  6. Nuclear Collisions
  7. Progress in the Phenomenology of Double Parton Scattering
  8. Introduction
  9. DPS in W + 2-jet final states with CMS at the LHC
  10. Understanding the impact of DPS on V+bb production with CMS at the LHC
  11. Double $\mathrm{J}\space/\space\psi$ production with CMS at the LHC
  12. DPS in 4-jet final states with CMS at the LHC
  13. Open charm and $\mathrm{J}\space/\space\psi$ multiplicity dependence in pp collisions at $\sqrt{s}$ = 7 TeV with ALICE at the LHC

Figures (3)

  • Figure 1: Top: fully corrected data distributions, normalized to unity, for the DPS-sensitive observable. The second panel in this plot shows the ratio of data over madgraph5 + pythia8 with and without MPI, whereas in the third panel the ratio with powheg2 + pythia6 is shown. The ratio of the data and pythia8 is shown in the fourth panel. The band represents the total uncertainty of the data. Bottom: centre-of-mass energy dependence of $\sigma_{\rm eff}$ measured by different experiments using different processes Akesson:1986ivAbe:1993rvAbe:1997xkAbazov:2009gcAad:2013bjmChatrchyan:2013xxa. These measurements used different approaches for extraction of the DPS fraction and $\sigma_{\rm eff}$. The corrected CDF data point indicates the $\sigma_{\rm eff}$ value corrected for the exclusive event selection Bahr:2013gkj.
  • Figure 2: Distribution of the azimuthal angle $\Delta \phi_{Z,bb}$ between the Z boson and the dijet system in Z+2b-jets final states in pp interactions at $\sqrt{s}=7$ TeV along with the Monte Carlo predictions: Inclusive Z+jets and tt events are simulated with madgraph 5.1.1.0, using pythia 6.424 with the Z2 tune for the parton showers, hadronization, and MPIs. The CTEQ6L1 parton distribution functions are used. The ZZ sample is simulated using pythia. Simulated samples are normalized to the theoretical predictions Chatrchyan:2014dha.
  • Figure 3: Top: differential cross section for prompt double $\mathrm{J}\space/\space\psi$ production as a function of the double $\mathrm{J}\space/\space\psi$ invariant mass ($M_{\rm JJ}$). Center: absolute rapidity difference between $\mathrm{J}\space/\space\psi$ mesons ($|\Delta y|$). Bottom: double $\mathrm{J}\space/\space\psi$ transverse momentum ($p_T^{\rm JJ}$). The gray boxes represent statistical errors only, and the error bars represent statistical and systematic errors added in quadrature.