Inclusive Jet Production, Parton Distributions, and the Search for New Physics

TL;DR

The study analyzes inclusive jet production at the Tevatron to constrain the high-$x$ gluon component of PDFs using Hessian uncertainty analysis with CTEQ6.1M, showing that Run 1b data favor an enhanced gluon at large $x$ and that NLO QCD predictions remain robust within PDF uncertainties. It assesses theoretical uncertainties from scale variation and threshold resummation, finding them smaller than the PDF-induced uncertainties, and explores limits on new physics via quark compositeness, proving that Run 1b already constrains the scale to $\Lambda>1.6$ TeV. The work provides detailed predictions for Run 2 and the LHC, including central cross sections and uncertainty bands, and demonstrates that cross-energy ratios can greatly reduce PDF and systematic uncertainties, guiding future jet measurements to sharpen the high-$x$ gluon determination and probe for new physics.

Abstract

Jet production at the Tevatron probes some of the smallest distance scales currently accessible. A gluon distribution that is enhanced at large x compared to previous determinations provides a better description of the Run 1b jet data from both CDF and D0. However, considerable uncertainty still remains regarding the gluon distribution at high x. In this paper, we examine the effects of this uncertainty, and of the remaining uncertainties in the NLO QCD theory, on jet cross section comparisons to Run 1b data. We also calculate the range of contributions still possible from any new physics. Predictions are also made for the expanded kinematic range expected for the ongoing Run 2 at the Tevatron and for the LHC.

Figures (31)

• Figure 1: The DØ inclusive jet cross section versus $E_{T}$ for five rapidity bins compared to NLO predictions using the CTEQ6.1M PDF's. The abscissa is $E_{T}$ in GeV. The ordinate is (data $-$ theory)/theory. The curves show the CTEQ5M, CTEQ5HJ, and CTEQ6M predictions, as fractional differences compared to CTEQ6.1M. The error bars are the statistical and systematic errors combined in quadrature.
• Figure 2: Left: The CTEQ5M, CTEQ5HJ, and CTEQ6M gluon distributions at $Q^{2}=10$ GeV$^{2}$. Right: The ratios of CTEQ5M and CTEQ5HJ gluon distribution to that of CTEQ6M. The dashed curves show the CTEQ6.1M gluon distribution.
• Figure 3: The subprocess contributions to central jet production.
• Figure 4: The subprocess contributions to jet production in the forward rapidity region.
• Figure 5: Left: Parton momentum fractions $x_{1}$ and $x_{2}$ for $y_{j}=0$; the solid and dashed curves are for $E_{T}=400$ and $200$ GeV, respectively. Right: Parton momentum fractions $x_{1}$ and $x_{2}$ for $y_{j}=2$; the solid and dashed curves are for $E_{T}=200$ and $100$ GeV, respectively.