arXiv subjects

I. Schienbein

Publications and source records attributed to I. Schienbein.

115 records · Page 7Linked to original sources

arXiv1999

Radiatively Generated Parton Distributions of Real and Virtual Photons

The parton content of real (P^2=0) and virtual (P^2\neq 0) transverse photons γ(P^2) is expressed in terms of perturbative pointlike and nonperturbative hadronic (VMD) components, employing recently updated parton distributions of pions and protons. The resulting parameter-free and perturbatively stable LO and NLO parton densities f^{γ(P^2)}(x,Q^2) are smooth in P^2 and apply to all P^2 >= 0 whenever γ(P^2) is probed at scales Q^2 >> P^2 where transverse photons also dominate physically relevant cross sections. Predictions are given for the structure function F_2^{γ(P^2)}(x,Q^2) and f^{γ(P^2)}(x,Q^2), and are compared with all relevant data for real photons as well as with recent data for virtual photons as extracted from DIS ep dijet events. Simple analytic parametrizations of our predicted parton distributions are presented for the real photon in LO and NLO, and for the virtual photon in LO which, within sufficient accuracy, may be also used in NLO-QCD.

hep-ph↗

arXiv1999

Pionic Parton Distributions Revisited

Using constituent quark model constraints we calculate the gluon and sea-quark content of pions solely in terms of their valence density (fixed by πN Drell-Yan data) and the known sea and gluon distributions of the nucleon, using the most recent updated valence-like input parton densities of the nucleon. The resulting small-x dynamical QCD predictions for g^π(x,Q^2) and \bar{q}^π(x,Q^2) are unique and parameter free. Simple analytic parametrizations of the resulting parton distributions of the pion are presented in LO and NLO. These results and parametrizations will be important, among other things, for updated formulations of the parton distributions of real and virtual photons.

hep-ph↗

arXiv1998

Heavy Quark Fragmentation in Deep Inelastic Scattering

We perform an analysis of semi-inclusive production of charm (D-mesons) in neutral current (NC) and charged current (CC) deep inelastic scattering (DIS) at full O(alpha_s^1). Our calculation is based on the heavy quark scheme developed by Aivazis, Collins, Olness and Tung (ACOT) where we include an O(alpha_s^1) calculation of quark scattering contributions for general masses and couplings. We review the relevant massive formulae and subtraction terms and discuss their massless limits. We show how the charm fragmentation function can be measured in CC DIS and we investigate whether the charm production dynamics may be tested in NC DIS. We also discuss finite initial state quark mass effects in CC and NC DIS.

hep-ph↗

arXiv1998

Heavy Quark Initiated Contributions to Deep Inelastic Structure Functions

We present O(alpha_s^1) corrections to deep inelastic scattering amplitudes on massive quarks obtained within the scheme of Aivazis, Collins, Olness and Tung (ACOT). After identifying the correct subtraction term the convergence of these contributions towards the analogous coefficient functions for massless quarks, obtained within the modified minimal subtraction scheme (MSbar), is demonstrated. Furthermore, the quantitative relevance of the contributions to neutral current (NC) and charged current (CC) structure functions is investigated for several choices of the factorization scale.

hep-ph↗

arXiv1998

Leading log radiative corrections to polarized heavy flavour leptoproduction

O(α) QED radiative corrections to polarized neutral current leptoproduction of heavy quark flavours are calculated in the leading log approximation for HERMES, COMPASS, and HERA kinematics. Besides the inclusive case, we derive general $z_h$-differential formulae for the polarized boson gluon fusion process and use them to calculate radiative corrections to semi-inclusive polarized heavy flavour production in the case of HERA kinematics.

hep-ph↗

arXiv1997

Leading log radiative corrections to deep inelastic production of heavy quarks

O(α) QED radiative corrections to neutral current deep inelastic production of heavy quarks are calculated in the leading log approximation and compared with the corresponding corrections assuming a massless charm parton. Besides the inclusive case, corrections to the semi-inclusive d^3σ/dx dy dz and the effect of z-cuts are studied. In the latter case, the massless corrections differ from the correct massive radiative corrections to deep inelastic heavy quark production by about 40%-10% for 0.2\lesssim z \lesssim 0.5.

hep-ph↗

arXiv1997

Charged-Current Leptoproduction of D-Mesons in the Variable Flavor Scheme

We present formulae for the momentum (z) distributions of D-mesons produced in neutrino deep-inelastic scattering off strange partons. The expressions are derived within the variable flavor scheme of Aivazis et al. (ACOT-scheme), which is extended from its fully inclusive formulation to one-hadron inclusive leptoproduction. The dependence of the results on the assumed strange quark mass m_s is investigated and the m_ \to 0 limit is compared to the corresponding MSbar results. The importance of O(alpha_s) quark-initiated corrections is demonstrated for the m_s=0 case.

hep-ph↗