119193340
The concept of phenomenological light-front wave functions -- Regge improved diquark model predictions
We introduce a classification scheme for parton distribution models and we model generalized parton distributions (GPDs), their form factors, and parton distribution functions (PDFs), integrated and unintegrated ones, in terms of unintegrated double distributions that are obtained from the parton number conserved overlap of effective light-front wave functions. For a so-called "spherical" model we present general expressions for all twist-two related non-perturbative quantities in terms of one effective light-front wave function, including chiral-odd GPDs. We also discuss the Regge improvement of such quark models from the $s$-channel point of view and study the relations between zero-skewness GPDs and unintegrated PDFs on a more general ground. Finally, we provide a few phenomenological applications that emphasize the role of orbital angular momenta.
55515915
Integrated and unintegrated PDFs and GPDs from effective two-body light-cone wave functions
We suggest a classification scheme for parton distribution m odels, clarify the geometrical origin of unintegrated parton distribution relations, which were observed in various models, present new model relations, and provide for a so-called “spherical” model the analogous constraints for generalized parton distributions. Our findings suggest tha t various classes of uPDF and GPD models can be obtained from effective two-body light-cone wave functions.
29739080
Exclusive hard Reactions and QCD
Exclusive reactions at large momentum transfer allow to probe the structure of hadrons, in particular of the pion and nucleon, on the amplitude level. They are challenging both the experimental measurements and the theoretical understanding of Quantum Chromodynamics. We shortly introduce the concept of factorization, emphasize the importance of new experimental nucleon and photon-to-pion form factor measurements, and report on phenomenological progress in the description of hard exclusive electroproduction of photons, providing access to generalized parton distribution.
119000479
A partonic interpretation of DVCS at small xBj
We describe small‐XBj deeply virtual Compton scattering measurements at HERA in terms of generalized parton distributions at leading order of perturbation series.
14145062
Next-to-next-to-leading order corrections to deeply virtual Compton scattering: the non-singlet case
We study perturbative QCD corrections to deeply virtual Compton scattering on an unpolarized nucleon target in the flavor non-singlet sector to next-to-next-to-leading order accuracy, restricting ourselves to the kinematically dominant amplitude. The difference between the standard minimal subtraction and the conformal scheme, in which conformal symmetry is manifest, is studied to next-to-leading order. Beyond this order we employ conformal symmetry for the evaluation of perturbative corrections. Within a certain class of generalized parton distributions we find moderate radiative corrections.
15091219
Broken conformal invariance and spectrum of anomalous dimensions in QCD
Abstract Employing the operator algebra of the conformal group and the conformal Ward identities, we derive the constraints for the anomalies of dilatation and special conformal transformations of the local twist-2 operators in Quantum Chromodynamics. We calculate these anomalies in the leading order of perturbation theory in the minimal subtraction scheme. From the conformal consistency relation we derive then the off-diagonal part of the anomalous dimension matrix of the conformally covariant operators in the two-loop approximation of the coupling constant in terms of these quantities. We deduce corresponding off-diagonal parts of the Efremov-Radyushkin-Brodsky-Lepage kernels responsible for the evolution of the exclusive distribution amplitudes and non-forward parton distributions in the next-to-leading order in the flavour singlet channel for the chiral-even parity-odd and -even sectors as well as for the chiral-odd one. We also give the analytical solution of the corresponding evolution equations exploiting the conformal partial wave expansion.
84154696
Results from PETRA on the Average Lifetime of B Hadrons
119112341
Measurement of Inclusive Production of Light Charged Hadrons at BaBar
Inclusive hadron production cross sections in e+e-collisions shed light on the fundamental fragmentation and hadronization processes. We present measurements of the inclusive spectra of charged pions, kaons and protons in hadronic events at a center-of-mass energy of 10.54 \gev. These results are compared with theoretical predictions and the predictions of three hadronization models. Along with previous measurements at higher energies, they are also used to study the scaling properties of hadron production.
10514085
Fragmentation and Hadronization in e+e- Collisions
We present a number of jet fragmentation and hadronization measurements in e{sup +}e{sup -} {yields} Z{sup 0} {yields} hadrons. The L3 collaboration has searched for pointlike color singlet radiation in multi-jet events, limiting any such contribution to rapidity gap events at the few percent level. ALEPH and SLD have measured production rates of a number of identified hadrons, including precise, full-coverage spectra of B hadrons. L3 and SLD have studied charged track and identified hadron production in heavy- and light-flavor events. OPAL has made a pioneering comparison of charged multiplicities between events of the three light flavors, u{bar u}, d{bar d} and s{bar s}.
118472353
BIANCHI I SOLUTIONS OF EFFECTIVE QUADRATIC GRAVITY
It is believed that soon after the Planck time, Einstein's general relativity theory should be corrected to an effective quadratic theory. Numerical solutions for the anisotropic generalization of the Friedmann "flat" model E3 for this effective gravity are given. It must be emphasized that although numeric, these solutions are exact in the sense that they depend only on the precision of the machine. The solutions are identified asymptotically in a certain sense. It is found solutions which asymptote de Sitter space, Minkowski space and a singularity. This work is a generalization for nondiagonal spatial metrics of a previous result obtained by one of us and a collaborator for Bianchi I spaces.
119092137
Physics results from SLD using the CRID
Abstract We review recent Z 0 physics results from SLD that use CRID particle identification. The performance of the detector and likelihood method are described briefly. Several hadronization measurements are presented, including identified hadron production in events of different primary flavors, leading hadron production, and new correlation studies sensitive to details of both leading and nonleading hadron production. Identified K ± have been used in conjunction with precision vertexing to study charmless and doubly charmed B-hadron decays. This combination has also been used to tag b, b , c and c jets, yielding precise measurements of B 0 - B 0 mixing and of the asymmetric couplings A b and A c . Identified K ± and Λ 0 / Λ 0 have been used to tag s and s jets, yielding a measurement of A s . The clean identified particle samples provided efficiently by the CRID allow the purities of these tags to be measured from the data, an essential ingredient for precision physics.