A new generation of parton distribution functions with increased precision and quantitative estimates of uncertainties is presented. This work significantly extends previous CTEQ and other global analyses on two fronts: (i) a full treatment of available experimental correlated systematic errors for both new and old data sets; (ii) a systematic and pragmatic treatment of uncertainties of the parton distributions and their physical predictions, using a recently developed eigenvector-basis approach to the Hessian method. The new gluon distribution is considerably harder than that of previous standard fits. A number of physics issues, particularly relating to the behavior of the gluon distribution, are addressed in more quantitative terms than before. Extensive results on the uncertainties of parton distributions at various scales, and on parton luminosity functions at the Tevatron RunII and the LHC, are presented. The latter provide the means to quickly estimate the uncertainties of a wide range of physical processes at these high-energy hadron colliders, based on current knowledge of the parton distributions. In particular, the uncertainties on the production cross sections of the W, Z at the Tevatron and the LHC are estimated to be ±4% and ±5% respectively, and that of a light Higgs at the LHC to be ±5%.Progress on the determination of the parton distribution functions (PDF's) of the nucleon, from global quantum chromodynamics (QCD) analysis of hard scattering processes, is central to precision standard model (SM) phenomenology, as well as to new physics searches, at lepton-hadron and hadron-hadron colliders. There have been many new developments in recent years, beyond the conventional analyses that underlie the widely used PDF's [1-3]. These developments have been driven by the need to quantify the uncertainties of the PDF's and their physical predictions [4][5][6][7][8][9][10][11][12]. We report in this paper on a comprehensive new global QCD analysis based on the most current data, and on the recently developed methods of uncertainty study of [10][11][12]. This new analysis includes a full treatment of all available correlated experimental errors, as well as an extensive exploration of the parametrization of the input nonperturbative PDF's.Although this work is built on the series of previous CTEQ parton distributions [2], it represents more than an evolutionary updating of previous work to incorporate new experimental data sets. The methodology of [10-12] goes beyond the traditional paradigm of producing some subjectively chosen "best fits." It introduces a set of efficient and practical tools to characterize the parton parameter space in the neighborhood of the global minimum. This allows the systematic exploration of the uncertainties of parton distributions and their physical predictions due to known experimental errors and due to the input theoretical model parameters.There are many complex issues involved in a comprehensive global parton distribution analysis. Foremost among these on the experimental sid...

We extract new parton distribution functions (PDFs) of the proton by global analysis of hard scattering data in the general-mass framework of perturbative quantum chromodynamics. Our analysis includes new theoretical developments together with the most recent collider data from deep-inelastic scattering, vector boson production, and single-inclusive jet production. Due to the difficulty in fitting both the DO Run-II W lepton asymmetry data and some fixed-target DIS data, we present two families of PDFs, CT10 and CT10W, without and with these high-luminosity W lepton asymmetry data included in the global analysis. With both sets of PDFs, we study theoretical predictions and uncertainties for a diverse selection of processes at the Fermilab Tevatron and the CERN Large Hadron Collider.Comment: 42 pages; minor adjustment

We present new parton distribution functions (PDFs) at next-to-next-to-leading order (NNLO) from the CTEQ-TEA global analysis of quantum chromodynamics. These differ from previous CT PDFs in several respects, including the use of data from LHC experiments, and the new DØ charged lepton rapidity asymmetry data, as well as the use of a more flexible parametrization of PDFs that, in particular, allows a better fit to different combinations of quark flavors. Predictions for important LHC processes, especially Higgs boson production at 13 TeV, are presented. These CT14 PDFs include a central set and error sets in the Hessian representation. For completeness, we also present the CT14 PDFs determined at the leading order (LO) and the next-to-leading order (NLO) in QCD.Besides these general-purpose PDF sets, we provide a series of (N)NLO sets with various αs values and additional sets in general-mass variable flavor number (GM-VFN) schemes, to deal with heavy partons, with up to 3, 4, and 6 active flavors.

The latest CTEQ6.6 parton distributions, obtained by global analysis of hard scattering data in the framework of general-mass perturbative QCD, are employed to study theoretical predictions and their uncertainties for significant processes at the Fermilab Tevatron and CERN Large Hadron Collider. The previously observed increase in predicted cross sections for the standard-candle W and Z boson production processes in the general-mass scheme (compared to those in the zero-mass scheme) is further investigated and quantified. A novel method to constrain PDF uncertainties in LHC observables, by effectively exploiting PDF-induced correlations with benchmark standard model cross sections, is presented. Using this method, we show that the top-antitop pair cross section can potentially serve as a standard candle observable for the LHC processes dominated by initial-state gluon scattering. Among other benefits, precise measurements of $t\bar{t}$ cross sections would reduce PDF uncertainties in predictions for single-top quark and Higgs boson production in the standard model and minimal supersymmetric standard model.Comment: 32 pages, 15 figures; figures with embedded fonts available at http://hep.pa.msu.edu/cteq/public/6.6/pdfs/; extended discussion of small-x strangeness, added references, minor changes in Figs. 2-4 in the revised versio

An up-to-date global QCD analysis of high energy lepton-hadron and hadronhadron interactions is performed to better determine the gluon and quark parton distributions in the nucleon. Improved experimental data on inclusive jet production, in conjunction with precise deep inelastic scattering data, place good constraints on the gluon over a wide range of x; while new data on asymmetries in Drell-Yan processes contribute to better determine the d/u ratio. Comparisons with results of other recent global analyses are made, and the differences are described. Open issues and the general problem of determining the uncertainties of parton distributions are discussed.

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...

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We present next-to-next-to-leading order (NNLO) parton distribution functions (PDFs) from the CTEQ-TEA group. The CT10NNLO PDF fit is based on essentially the same global data sets used in the CT10 and CT10W NLO PDF analyses. After exploring the goodness of the fits to the HERA combined data and the Tevatron jet data, we present various predictions at NNLO accuracy for both existing and forthcoming precision measurements from the CERN Large Hadron Collider. The range of variations in the gluon distribution introduced by correlated systematic effects in inclusive jet production is also examined.