Transverse Target Research Articles

Azimuthal single spin asymmetries in SIDIS in the light of chiral symmetry breaking

An attempt is made to understand the z-dependence of the azimuthal single spin asymmetries observed by the HERMES Collaboration in terms of chiral models based on effective quark and Goldstone boson degrees of freedom. The effects of respectively neglecting and considering Gaussian intrinsic parton transverse momenta and the Sivers effect are explored. Predictions for the transverse target polarization experiment at HERMES are presented.

Two-Photon Processes and Photon Structure

In this article aspects of photon–photon physics related to the structure of real and virtual photons are reviewed. A recalculation of the virtual photon–photon box is performed and some discrepancies in the literature are clarified. A useful compilation of various relevant limits derived from the most general expressions is provided. Furthermore, structure functions of spin-averaged, transverse, and longitudinal virtual target photons are defined and discussed. Finally, the factorization of two-photon processes in the Bjorken limit is demonstrated to hold also for the case of virtual target photons.

Two-Photon Processes and Photon Structure

In this article aspects of photon–photon physics related to the structure of real and virtual photons are reviewed. A recalculation of the virtual photon–photon box is performed and some discrepancies in the literature are clarified. A useful compilation of various relevant limits derived from the most general expressions is provided. Furthermore, structure functions of spin-averaged, transverse, and longitudinal virtual target photons are defined and discussed. Finally, the factorization of two-photon processes in the Bjorken limit is demonstrated to hold also for the case of virtual target photons.

Spin observables in [formula omitted] with a transverse initial state polarization

The formalism describing the scattering of two spin- 1 2 objects is reviewed for the case of p ̄ p→ Λ ̄ Λ . It is shown that an experiment utilizing a transverse target polarization can, in principle, completely determine the spin structure of the reaction. Additional measurements, even those using both beam and target polarizations, would not be sensitive to any additional spin dynamics. Thus, the transverse target polarization allows access to the complete set of spin observables, not just the subset upon which the literature has previously focused. This discussion is especially relevant in light of the data collected by PS185/3 at LEAR.

A proposed transverse electron target for the ESR to study QED effects in the interaction of highly charged heavy ions with electrons

The investigation of electron-ion collisions using highly charged heavy ions in the storage ring ESR at GSI have so far been performed by using the electron cooler. The switching between cooling and probing mode and the interaction angle limit the attainable center-of-mass energies to a few hundred eV. This limitation can be overcome by the use of a separate transverse or longitudinal target. We propose to use the high energy electron beam of an electron beam ion source and trap without the use of a focusing magnetic field (XEBIST). An electron beam of up to 100 keV will be launched from a cathode with high emission density to form a target with a transverse temperature of about 10 meV resulting from beam expansion. The total center-of-mass energy spread for typical ions like U91+ may be as low as 10 eV, which will give eV-range resolution at high counting rates, allowing significant tests of QED theories.

Independent particle model description of multiple ionization dynamics in fast ion-atom collisions

The time-dependent dynamics of the many-electron density and its interaction with projectile and target nuclei is described within the semiclassical (=0) Vlasov model. Differential cross sections for multiple ionization as a function of projectile scattering angle and transverse target recoil momentum are calculated. Average scattering angles are obtained as a function of impact parameter within the model taking into account a given number of ejected electrons for each recoil ion charge state. Other results include projectile energy loss and the relationship between projectile and target nucleon motion. Comparison with experiment and classical N-particle simulations (N-CTMC) is made for two systems, namely, C6+-Ne and U3+-Ne at collision energies of 0.8 and 1.4 MeV amu-1 respectively.

Measurement of the total cross section difference ΔσT(pp) in the energy range from 0.43 to 2.4 GeV

The SATURNE II polarized proton beam and the Saclay frozen spin polarized proton target were used to measure the total cross section difference Δσ T = −2 σ 1 tot at 26 energies between 0.43 and 2.4 GeV. Here Δσ T is the total cross section difference for transverse beam and target spins parallel and antiparallel, respectively, and σ 1tot is one of spin-dependent terms in the total cross section σ tot. The energy dependence of Δσ T below 1 GeV shows similar structures as for Δσ L. An additional minimum appears at about 1.3 GeV, which involves a structure in singlet spin partial waves.

Intrinsic transverse momentum and structure function evolution in deep inelastic lepton hadron scattering

A model is constructed that allows to implement intrinsic transverse momentum and target mass in the QCD analysis ofQ2-evolution of structure functions in deep inelastic lepton hadron scattering without losing the factorization property of mass singularities. The modified evolution equations are integrated numerically and the results are compared to experimental data. It turns out that no further higher twist contributions are required.

A possible origin for temperature in strong interactions

We present the idea that the large transverse acceleration, a, of projectile and target, which occurs in the course of a high-energy hadronic collision, is connected with the thermal emission of particles at a temperature given by kT = a 2π . From the computation of an average acceleration, we give a formula for T, which explains why it is largely independent of the nature of the projectile, and of the energy in the present domain of accelerator energies.