Fixed target Drell-Yan data and NNLO QCD fits of parton distribution functions

We discuss the influence of fixed target Drell-Yan data on the extraction of parton distribution functions at next-to-next-to-leading order (NNLO) in QCD. When used in a parton distribution fit, the Drell-Yan (DY) data constrain sea quark distributions at large values of Bjorken x. We find that not all available DY data are useful for improving the precision of parton distribution functions (PDFs) obtained from a fit to the deep inelastic scattering (DIS) data. In particular, some inconsistencies between DIS-based parton distribution functions and DY data for large values of dilepton rapidity are found. However, by selecting a sample of the DY data that is both representative and consistent with the DIS data, we are able to perform a combined PDF fit that significantly improves the precision of non-strange quark distributions at large values of x. The NNLO QCD corrections to the DY process are crucial for improving the precision. They reduce the uncertainty of the theoretical prediction, making it comparable to the experimental uncertainty in DY cross-sections over a broad range of x.Comment: 12 pages, revte

Transverse Lepton Polarization in Polarized W Decays

Calculations of transverse polarization of leptons in the decay $W\rightarrow l\nu$ with polarized $W$'s are presented. Planned accelerators will produce enough $W$'s for observation of the Standard Model contributions to this polarization. One loop corrections to the polarization are given; these are too small to be seen at presently available $W$ sources. The exchange of Majorons will contribute to these polarizations; these may provide limits on the couplings of these particles to leptons.Comment: 8 pages set in RevTex III and 4 uucompressed figures. This revised version studies polarization effects due to the exchange of charged Majoron doublet

Threshold corrections to rapidity distributions of Z and W^\pm bosons beyond N^2 LO at hadron colliders

Threshold enhanced perturbative QCD corrections to rapidity distributions of $Z$ and $W^\pm$ bosons at hadron colliders are presented using the Sudakov resummed cross sections at N${}^3$LO level. We have used renormalisation group invariance and the mass factorisation theorem that these hard scattering cross sections satisfy to construct the QCD amplitudes. We show that these higher order threshold QCD corrections stabilise the theoretical predictions for vector boson production at the LHC under variations of both renormalisation and factorisation scales.Comment: 17 pages, 8 eps figures. This paper is dedicated to the memory of W.L.G.A.M. van Neerve

Detection of an enol intermediate in the hydroperoxide lyase chain cleavage reaction

AbstractGuava (Psidium guajava) hydroperoxide lyase (HPL) preparations were incubated with [1-14C](9Z,11E,13S,15Z)-13-hydroperoxy-9,11,15-octadecatrienoic acid for 1 min at 0°C, followed by rapid extraction/trimethylsilylation. Analysis of the trimethylsilylated products by gas chromatography–mass spectrometry and radio-high-performance liquid chromatography revealed a single predominant 14C-labelled compound, identified by its 1H-nuclear magnetic resonance, ultraviolet and mass spectra as the trimethylsilyl ether/ester of (9Z,11E)-12-hydroxy-9,11-dodecadienoic acid. Longer time incubations afford smaller yield of this enol due to its partial tautomerization into (9Z)-12-oxo-9-dodecenoic acid. The data obtained demonstrate that formation of (9Z)-12-oxo-9-dodecenoic acid in the HPL reaction is preceded by unstable enol oxylipin, and further suggest that hemiacetals are the true products of HPL catalysis

Parton distribution functions from the precise NNLO QCD fit

We report the parton distribution functions (PDFs) determined from the NNLO QCD analysis of the world inclusive DIS data with account of the precise NNLO QCD corrections to the evolution equations kernel. The value of strong coupling constant \alpha_s^{NNLO}(M_Z)=0.1141(14), in fair agreement with one obtained using the earlier approximate NNLO kernel by van Neerven-Vogt. The intermediate bosons rates calculated in the NNLO using obtained PDFs are in agreement to the latest Run II results.Comment: 8 pages, LATEX, 2 figures (EPS

Subtraction Terms for Hadronic Production Processes at Next-to-Next-to-Leading Order

I describe a subtraction scheme for the next-to-next-to-leading order calculation of single inclusive production at hadron colliders. Such processes include Drell-Yan, W^{+/-}, Z and Higgs Boson production. The key to such a calculation is a treatment of initial state radiation which preserves the production characteristics, such as the rapidity distribution, of the process involved. The method builds upon the Dipole Formalism and, with proper modifications, could be applied to deep inelastic scattering and e^+ e^- annihilation to hadrons.Comment: 4 page

Threshold Corrections in Precision LHC Physics: QED otimes QCD

With an eye toward LHC processes in which theoretical precisions of 1 percent are desired, we introduce the theory of the simultaneous YFS resummation of QED and QCD to compute the size of the expected resummed soft radiative threshold effects in precision studies of heavy particle production at the LHC. Our results show that both QED and QCD soft threshold effects must be controlled to be on the conservative side to achieve such precision goals.Comment: 4 pages, no figures; presented by B.F.L. Ward in DPF200

Higher-Order Corrections in Threshold Resummation

We extend the threshold resummation exponents G^N in Mellin-N space to the fourth logarithmic (N^3LL) order collecting the terms alpha_s^2 (alpha_s ln N)^n to all orders in the strong coupling constant as. Comparing the results to our previous three-loop calculations for deep-inelastic scattering (DIS), we derive the universal coefficients B_q and B_g governing the final-state jet functions to order alpha_s^3, extending the previous quark and gluon results by one and two orders. A curious relation is found at second order between these quantities, the splitting functions and the large-angle soft emissions in Drell-Yan type processes. We study the numerical effect of the N^3LL corrections using both the fully exponentiated form and the expansion of the coefficient function in towers of logarithms.Comment: 20 pages, LaTeX, 6 eps-figures. Misprints in equations and fig. 5 correcte

Higher-Order Soft Corrections to Lepton Pair and Higgs Boson Production

Utilizing recent three-loop results on the quark and gluon splitting functions and form factors, we derive the complete threshold-enhanced third-order (N^3LO) QCD corrections to the total cross sections for the production of lepton pairs and the Higgs boson in hadron collisions. These results, for the latter case obtained in the heavy top-quark limit, are employed to extend the threshold resummation for these processes to the fourth logarithmic order. We investigate the numerical impact of the higher-order corrections for Higgs boson production at the Tevatron and the LHC. Our results, suitably treated in Mellin N-space, provide a sufficiently accurate approximation to the full N^3LO contributions. Corrections of about 5% at the LHC and 10% at the Tevatron are found for typical Higgs masses. The N^3LO predictions exhibit a considerably reduced dependence on the renormalization scale with, for the first time, stationary points close to the Higgs mass.Comment: 11 pages, LaTeX, 2 eps-figures. Slightly revised text of journal version, with two new references. Misprint in eq. (13) correcte

Next-to-Next-to-Leading Order Higgs Production at Hadron Colliders

The Higgs boson production cross section at pp and p\bar{p} colliders is calculated in QCD at next-to-next-to-leading order (NNLO). We find that the perturbative expansion of the production cross section is well behaved and that scale dependence is reduced relative to the NLO result. These findings give us confidence in the reliability of the prediction. We also report an error in the NNLO correction to Drell-Yan production.Comment: 5 pages, 4 figures, minor change