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 DØ. 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. I. INTRODUCTION: JET CROSS SECTIONS AT THE TEVATRONJet production at the Tevatron probes the highest momentum transfer region currently accessible. As this region is potentially sensitive to a wide variety of new physics, there was great interest when the inclusive jet cross section measured by the CDF collaboration in Run 1b exhibited an excess in the highest E T range, when compared to NLO predictions using then-current parton distribution functions [1]. In an attempt to determine if conventional physics could explain the deviation, the CTEQ PDF fitting group carried out a global analysis using information from deep-inelastic scattering and Drell-Yan data, as well as from jet data from the Tevatron, but giving a higher statistical emphasis to the high E T jet data from CDF [2]. NLO predictions using the resulting fit (CTEQ4HJ) reduced the size of the excess observed by CDF. The jet data from both CDF and DØ were also used in a more conventional fit (CTEQ4M) where no special emphasis was given to the high E T data [3].The dominant subprocess that contributes to jet production at high E T is quark-(anti)quark scattering. However, the quark distributions in the corresponding x range are very well constrained by the precise DIS and DY data used in the global fits. Only the gluon distribution has the flexibility to change significantly in the high x region, and indeed the gluon distribution increases by roughly a factor of 2 for x values of about 0.5 in the CTEQ4HJ fit. The gluon-quark scattering subprocesses increase from approximately 20% of the total jet cross section at high E T using CTEQ4M to 40% using CTEQ4HJ [2]. The next group of PDF's from CTEQ (CTEQ5) [4] also contained two sets: CTEQ5M, the standard lowest χ 2 solution, and CTEQ5HJ, defined by a similar statistical enhancement applied to the high E T data from CDF [5] and DØ [6].More recently, DØ has measured the inclusive jet cross section as a function of rapidity y over the range 0 ≤ |y| ≤ 3 [7]. This data set, comprised of 90 data points, has a greater statistical power in the global fits than the CDF and DØ jet cross section measurements in the central region alone. The CTEQ6M fit [8] utilizes these DØ jet cross section measurements, along with the CDF measurements in the central rapidity region, as well as the most recent DIS data from HERA an...

We critically examine uncertainties in parton distribution functions (PDFs) at large x arising from nuclear effects in deuterium F 2 structure function data. Within a global PDF analysis, we assess the impact on the PDFs from uncertainties in the deuteron wave function at short distances and nucleon off-shell effects, from the use of relativistic kinematics, and from the use of a less restrictive parametrization of the d/u ratio. We find in particular that the d-quark and gluon PDFs vary significantly with the choice of nuclear model. We highlight the impact of these uncertainties on the determination of the neutron structure functions, and on W boson production and parton luminosity at the Tevatron and the LHC. Finally, we discuss prospects for new measurements sensitive to the d-quark and gluon distributions but insensitive to nuclear corrections.

We review the present status of the determination of parton distribution functions (PDFs) in the light of the precision requirements for the LHC in Run 2 and other future hadron colliders. We provide brief reviews of all currently available PDF sets and use them to compute cross sections for a number of benchmark processes, including Higgs boson production in gluon-gluon fusion at the LHC. We show that the differences in the predictions obtained with the various PDFs are due to particular theory assumptions made in the fits of those PDFs. We discuss PDF uncertainties in the kinematic region covered by the LHC and on averaging procedures for PDFs, such as advocated by the PDF4LHC15 sets, and provide recommendations for the usage of PDF sets for theory predictions at the LHC.

We perform a χ 2 -analysis of Nuclear Parton Distribution Functions (NPDFs) using neutral current charged-lepton (ℓ ± A) Deeply Inelastic Scattering (DIS) and Drell-Yan data for several nuclear targets. The nuclear A dependence of the NPDFs is extracted in a next-to-leading order fit. We compare the nuclear corrections factors (F F e 2 /F D 2 ) for this charged-lepton data with other results from the literature. In particular, we compare and contrast fits based upon the charged-lepton DIS data with those using neutrino-nucleon DIS data.

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