13486962
Wave functions, evolution equations and evolution kernels from light ray operators of QCD
The widely used nonperturbative wave functions and distribution functions of QCD are determined as matrix elements of light-ray operators. These operators appear as large momentum limit of non-local hadron operators or as summed up local operators in light-cone expansions. Nonforward one-particle matrix elements of such operators lead to new distribution amplitudes describing both hadrons simultaneously. These distribution functions depend besides other variables on two scaling variables. They are applied for the description of exclusive virtual Compton scattering in the Bjorken region near forward direction and the two meson production process. The evolution equations for these distribution amplitudes are derived on the basis of the renormalization group equation of the considered operators. This includes that also the evolution kernels follow from the anomalous dimensions of these operators. Relations between different evolution kernels (especially the Altarelli-Parisi and the Brodsky-Lepage kernels) are derived and explicitly checked for the existing two-loop calculations of QCD. Technical basis of these results are support and analytically properties of the anomalous dimensions of light-ray operators obtained with the help of the α-representation of Green's functions.
118999304
Deeply virtual Compton scattering at a proposed high-luminosity Electron-Ion Collider
A bstractSeveral observables for the deeply virtual Compton scattering process have been simulated in the kinematic regime of a proposed Electron-Ion Collider to explore the possible impact of such measurements for the phenomenological access of generalized parton distributions. In particular, emphasis is given to the transverse distribution of sea quarks and gluons and how such measurements can provide information on the angular momentum sum rule. The exact lepton energy loss dependence for the unpolarized t-differential electroproduction cross section, needed for a Rosenbluth separation, is also reported.
199675393
The Evolution of the nonsinglet twist - three parton distribution function
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.
14431309
Generic modelling of non-perturbative quantities and a description of hard exclusive pi+ electroproduction
Based on Regge-inspired arguments and counting rules, we formulate empirical models for zero-skewness generalized parton distributions (GPDs) ${\widetilde H}^{(3)}$ and ${\widetilde E}^{(3)}$ in the iso-vector sector. If a hypothetical $a_1/\rho_2$ master trajectory is taken into account, we find that the polarized deep inelastic structure function $g_1^{(3)}$, axial-vector form factor, pseudoscalar form factor, and lattice data are well described. Thereby, we use a symmetric valence scenario in which the `spin puzzle' in the iso-vector sector is trivially resolved. Utilizing a minimalist `holographic' GPD principle, tying the $t$-channel angular momentum and collinear conformal spin together, we build skewness dependent GPD models. Confronting these models with HERMES and JLAB measurements of hard exclusive $\pi^+$ electroproduction within the collinear factorization approach, we might conclude that minimalist GPD models are disfavored at leading order. We provide then a set of GPDs on the cross-over line that fairly describes both HERMES and JLAB measurements.
45253761
Exclusive electroproduction of lepton pairs as a probe of nucleon structure.
We suggest the measurement of exclusive electroproduction of lepton pairs as a tool to study interparton correlations in the nucleon via generalized parton distributions in the kinematical region where this process is light-cone dominated. We demonstrate how the single beam-spin asymmetry allows one to perform such a kind of analysis and give a number of predictions for several experimental setups. We comment on other observables which allow for a clean separation of different species of generalized parton distributions.
124860285
Review of c, b and τ Lifetimes from e+e- Experiments
The current status of lifetime measurements of heavy flavored particles by experiments at e + e - colliders and their implications for the standard model are reviewed. This includes the most recent measurents of lifetimes of the tau lepton, the D mesons and B hadrons. The emphasis is on B hadron lifetimes, since there are several new results contributed to this conference. The first use of the B lifetime to tag and study bƃ events is also discussed.
119377344
Casimir Effect in Compact Universes
The Casimir effect in compact hyperbolic Universes was numerically obtained in previous publications. In this talk, I expose these results.
1646135
THE DIRC COUNTER: A NEW TYPE OF PARTICLE IDENTIFICATION DEVICE FOR B FACTORIES*
A very thin, solid radiator, totally internally reflecting, imaging Cherenkov counter (DIRC) is described. This device is well matched to requirements at an asymmetric e+e- B Factory. the hadronic charged particle identification 1. INTR~IXJ~TI~N Particle identification at a B factory is difficult, and highly constrained by the machine environment and the need for good energy measurement of soft photons in the calorimeter which surrounds the particle identification device [l]. Because of the high beam crossing rate and the potential for large backgrounds, the particle identification detector must be robust and relatively fast. Good r~‘dK separation is required over a wide momentum range between about 0.25 and 4 GeV/c. Most detectors measure dE/dx in the tracking chamber which allows good X/K separation up to about 600 MeV/c, but a specific identification device is required over most of the momentum region [2]. The amount of material in the device should be small (preferably less than 10% LRAD) and should be distributed as close as possible to the calorimeter in order to avoid degradation in the resolution performance of the calorimeter, and the loss of low energy conversion electrons in the magnetic field. In addition, the cost of the high quality calorimeter scales roughly like the radius squared and there will be substantial cost savings if the particle identification device can be made thin.
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}.
120017490
QCD studies of hadronic decays of Z0 bosons by SLD
Z0 bosons have been produced by collisions of longitudinally polarized electrons with unpolarized positrons at the SLAC Linear Collider and their decays have been recorded by the SLD experiment. We present preliminary QCD results based on the first 6000 such decays. We find good agreement between the inclusive properties of these data and the predictions of perturbative QCD plus fragmentation models. The strong coupling, αs, has been measured by three methods: jet rates yield αs(MZ)=0.119±0.002(stat.)±0.003(exp. syst.)±0.014(theor.); energy‐energy correlations yield αs(MZ)=0.121±0.002±0.004±0.0160.009; and the energy‐energy correlation asymmetry gives αs(MZ)=0.108±0.003±0.005±0.0080.003.