Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Inclusive jet cross section in $pp$ collisions at $\sqrt{s} = 200$ and $510$ GeV

The STAR Collaboration

Abstract

Jets are collimated clusters of particles formed by the hadronization of partons following a hard interaction. In proton-proton ($pp$) collisions at the Relativistic Heavy Ion Collider (RHIC), jet production is dominated by $gg$ and $qg$ partonic processes, allowing us to directly probe the gluon parton distribution function (PDF) in the proton in a way complementary to deep inelastic scattering. In this paper, we report the double-differential inclusive-jet cross sections as a function of jet transverse momentum, $p_{\rm T}$, and pseudorapidity, $η$, at center-of-mass energies $\sqrt{s} = 200$ and $510$~GeV, from $pp$ collisions studied with the STAR detector. The jet $p_{\rm T}$ is corrected for underlying event contributions by applying an off-axis cone method. At mid-pseudorapidity, $|η| < 0.9$, the kinematic coverage of our data extends to $0.07 < x_{\rm T} \text{ (}= 2p_{\rm T}{} / \sqrt{s} \text{)} < 0.5$ and $0.03 < x_{\rm T} < 0.31$ at $\sqrt{s} = 200$~and 510 GeV, respectively, where the gluon PDF is poorly constrained by the TeV-scale $pp$~($p\bar{p}$) colliders. The inclusive jet cross sections are compared to the next-to-next-to-leading order perturbative quantum chromodynamics calculations using several recent PDF sets as inputs. These results will further constrain the gluon PDF, help tune Monte Carlo generators, and provide critical reference data needed to study the quark-gluon plasma.

Inclusive jet cross section in $pp$ collisions at $\sqrt{s} = 200$ and $510$ GeV

Abstract

Jets are collimated clusters of particles formed by the hadronization of partons following a hard interaction. In proton-proton () collisions at the Relativistic Heavy Ion Collider (RHIC), jet production is dominated by and partonic processes, allowing us to directly probe the gluon parton distribution function (PDF) in the proton in a way complementary to deep inelastic scattering. In this paper, we report the double-differential inclusive-jet cross sections as a function of jet transverse momentum, , and pseudorapidity, , at center-of-mass energies and ~GeV, from collisions studied with the STAR detector. The jet is corrected for underlying event contributions by applying an off-axis cone method. At mid-pseudorapidity, , the kinematic coverage of our data extends to and at ~and 510 GeV, respectively, where the gluon PDF is poorly constrained by the TeV-scale ~() colliders. The inclusive jet cross sections are compared to the next-to-next-to-leading order perturbative quantum chromodynamics calculations using several recent PDF sets as inputs. These results will further constrain the gluon PDF, help tune Monte Carlo generators, and provide critical reference data needed to study the quark-gluon plasma.

Paper Structure

This paper contains 17 sections, 7 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Experiment and Data
  3. The STAR detector at RHIC
  4. Luminosity measurement
  5. Triggered events
  6. Jet reconstruction
  7. Underlying event correction
  8. Counting jets
  9. Simulation
  10. Embedding process
  11. Unfolding
  12. Systematic uncertainties
  13. Detector effect uncertainty
  14. Unfolding uncertainty
  15. Hadronization correction
  16. ...and 2 more sections

Figures (7)

  • Figure 1: The distribution of reconstructed jets as a function of $\frac{p_{\text{T},\text{detector jet}}}{p_{\text{T},\text{particle jet}}}$ for various particle-jet $p_{\text{T}}$ bins from the embedding sample where the corresponding detector jets were required to satisfy the exclusive JP0 trigger for the lowest $p_{\text{T}}$ bin, exclusive JP1 for the intermediate $p_{\text{T}}$ bin, and exclusive JP2 for the highest $p_{\text{T}}$ bin. The exclusive-trigger selections were based on the choice made in this analysis to avoid double counting among three jet-patch-triggered events with increasing thresholds. The left plot is for $\sqrt{s}=200$ GeV and the right plot is for $510$ GeV.
  • Figure 2: A comparison between data and simulation of the charge-separated $f_{h}$ distribution for tracks with momenta, 2 $<p<$ 3 GeV/$c$ from 510 GeV $pp$ collisions. The reason to separate by hadron charge is that $K^{-}$ has a larger interaction cross section with the electromagnetic calorimeter materials than $K^{+}$, and that $\bar{p}$ can annihilate with $p$ from the $\text{Pb}$ plates in the calorimeter.
  • Figure 3: Hadronization correction factor at $\sqrt{s} = 200$ and $510$ GeV. Error bars represent systematic uncertainty obtained from Perugia 2012 tune variations which are related to alternative parameters for initial-state and final-state radiations, fragmentation process, and hadronization.
  • Figure 4: Unfolded double-differential jet cross section, $\frac{d^2\sigma}{dp_{\text{T}}{}d\eta}$, as a function of the jet $p_{\text{T}}{}$ at $\sqrt{s} = 200$ and 510 GeV. The double-differential jet cross sections from the NNLO pQCD with CT18 PDF after hadronization corrections and the Pythia 6 STAR tune are also plotted.
  • Figure 5: Ratio of jet cross section predicted by Pythia 6 and Pythia 8 to the present measurements at $\sqrt{s} = 200$ GeV (on the left) and at $\sqrt{s} = 510$ GeV (on the right).
  • ...and 2 more figures