Neutrino dimuon production and the dynamical determination of strange parton distributions

Utilizing recent neutrino dimuon production measurement from NuTeV the assumptions on the determination of the strangeness content of the nucleon within the dynamical approach to parton distributions are investigated. The data are found to be in good agreement with the predictions derived from our (GJR08) dynamical parton distributions, which have been generated entirely radiatively starting from vanishing strange input distributions at an optimally chosen low resolution scale. Further, the data induce an asymmetry in the strange sea which is found to be small and positive in agreement with previous results.Comment: 6 pages, 2 figure

Dynamical Parton Distributions of the Nucleon up to NNLO of QCD

A new generation of (unpolarized) dynamical parton distribution functions of the nucleon is determined. After introducing basic elements of perturbative QCD, the dynamical model is discussed and compared with the approach to parton distributions used by most other groups ("standard"). Parton distributions sets (with uncertainties) at different orders (LO, NLO, NNLO), using different factorization schemes (\overline{MS}, DIS) and different treatments of heavy quark masses (FFNS, VFNS) are extracted and compared. The astrophysical implications of the dynamical predictions are outlined before focusing on collider phenomenology. There, the relevance and perturbative stability of the longitudinal structure function of the nucleon is studied, and the role of heavy quark flavors in high-energy colliders is analyzed. In addition, it is shown how isospin violations in the nucleon help to explain the so-called "NuTeV anomaly".Comment: Ph.D. Thesis, 98 page

Phenomenology of the Flavor-Asymmetry in the Light-Quark Sea of the Nucleon

A phenomenological ansatz for the flavor-asymmetry of the light sea distributions of the nucleon, based on the Pauli exclusion principle, is proposed. This ansatz is compatible with the measured flavor-asymmetry of the unpolarized sea distributions, $\bar{d}>\bar{u}$, of the nucleon. A prediction for the corresponding polarized flavor-asymmetry is presented and shown to agree with predictions of (chiral quark--soliton) models which successfully reproduced the flavor-asymmetry of the unpolarized sea.Comment: 5 pages, LaTeX, 2 figures, uses epsfi

CJK- Improved LO Parton Distributions in the Real Photon and Their Experimental Uncertainties

A new analysis of the radiatively generated, LO quark (u,d,s,c,b) and gluon densities in the real, unpolarized photon, improved in respect to our paper [1], is presented. We perform four new global fits to the experimental data for F2^gamma, two using a standard FFNS approach and two based on ACOT(chi) scheme [2], leading to the FFNS(CJK) and CJK models. We also present the analysis of the uncertainties of the new CJK 2 parton distributions due to the experimental errors, the very first such analysis performed for the photon. This analysis is based on the Hessian method, for a comparison for chosen cross-sections we use also the Lagrange method.Comment: Prepared for Photon 2003: International Conference on the Structure and Interactions of the Photon (Including the 15th International Workshop on Photon-Photon Collisions), Frascati (Italy), 7-11 April 2003; 10 pages, Latex using espcrc2 style, 1 tex and 5 postscript figures; FORTRAN programs available at http://www.fuw.edu.pl/~pjank/param.htm

Forecast quality and simple instrument rules: a real-time data approach

We start from the assertion that a useful monetary policy design should be founded on more realistic assumptions about what policymakers can know at the time when policy decisions have to be made. Since the Taylor rule – if used as an operational device - implies a forward looking behaviour, we analyze the reliability of the input information. We investigate the forecasting performance of OECD projections for GDP growth rates and inflation. We diagnose a much better forecasting record for inflation rates compared to GDP growth rates, which for most countries are almost uninformative at the time a Taylor rule should sensibly be applied. Using this data set, we find significant differences between Taylor rules estimated over revised data compared to real-time data. There is evidence that monetary policy seems to react more actively in real time than rules estimated over revised data suggest. Given the evidence of systematic errors in OECD forecasts, in a next step we attempt to correct for these forecast biases and check to which extent this can lower the errors in interest rate policy setting. An ex-ante simulation for the years 1991 to 2001 supports the proposal that correcting for forecast errors and biases based on an error model can lower the resulting policy error in interest rate setting for most countries under consideration. In addition we investigate to what extent structural changes in the policy reaction behaviour can be handled with moving instead of expanding samples. Our results point out that the information set available needs a careful examination when applied to instrument rules like those of the Taylor type. Limited forecast quality and significant data revisions recommend a more sophisticated handling of the dated information, for which we present an operational procedure that has the potential of reducing the risk of severe policy errors. --Monetary policy rules,economic forecasting,OECD,real-time data

Radiatively Generated Isospin Violations in the Nucleon and the NuTeV Anomaly

Predictions of isospin asymmetries of valence and sea distributions are presented which are generated by QED leading ${\cal{O}}(\alpha)$ photon bremsstrahlung effects. Together with isospin violations arising from nonperturbative hadronic sources (such as quark and target mass differences) as well as with even a conservative contribution from a strangeness asymmetry ($s\neq \bar{s}$), the discrepancy between the large NuTeV `anomaly' result for $\sin^2\theta_W$ and the world average of other measurements is removed.Comment: 10 pages, 2 figure

Towards a NNLO calculation in hadronic heavy hadron production

We calculate the Laurent series expansion up to ${\cal O}(\epsilon^2)$ for all scalar one-loop one-, two-, three- and four-point integrals that are needed in the calculation of hadronic heavy flavour production. The Laurent series up to ${\cal O}(\epsilon^2)$ is needed as input to that part of the NNLO corrections to heavy hadron production at hadron colliders where the one-loop integrals appear in the loop-by-loop contributions. The four-point integrals are the most complicated. The ${\cal O}(\epsilon^2)$ expansion of the four-point integrals contains polylogarithms up to $Li_4$ and the multiple polylogarithms.Comment: 5 pages, 2 Postscript figure

Longitudinally Polarized Photoproduction of Inclusive Hadrons Beyond the Leading Order

We present a complete next-to-leading order QCD calculation for single-inclusive large-pT hadron production in longitudinally polarized lepton-nucleon collisions, consistently including ``direct'' and ``resolved'' photon contributions. This process could be studied experimentally at a future polarized lepton-proton collider like eRHIC at BNL. We examine the sensitivity of such measurements to the so far completely unknown parton content of circularly polarized photons.Comment: 15 pages, 7 eps figure

Threshold resummation for the prompt-photon cross section revisited

We study the resummation of large logarithmic perturbative corrections to the partonic cross sections relevant for the process pp->gamma X at high transverse momentum of the photon.These corrections arise near the threshold for the partonic reaction and are associated with soft-gluon emission. We especially focus on the resummation effects for the contribution to the cross section where the photon is produced in jet fragmentation. Previous calculations in perturbation theory at fixed-order have established that this contribution is a subdominant part of the cross section. We find, however, that it is subject to much larger resummation effects than the direct (non-fragmentation) piece and therefore appears to be a significant contribution in the fixed-target regime, not much suppressed with respect to the direct part. Inclusion of threshold resummation for the fragmentation piece leads to some improvement in comparisons between theoretical calculations and experimental data.Comment: 12 pages, 5 figure