Isoscalar electromagnetic form factors and the structure of the deuteron at high momentum transfer

We derive general expressions for isoscalar electromagnetic form factors of nuclei including meson-exchange processes such as π, ?, ω and ?πγ exchange. Meson-nucleon vertices for nonzero momentum transfer as well as the effect of the finite width of the ?-meson are taken care of. Specifically, the electromagnetic form factors of the deuteron are calculated up to a momentum transfer of q² ≈ 200 fm^?2. A detailed numerical discussion of the various effects on meson-exchange processes is given. The effect of different deuteron wave functions and two types of photon-nucleon form factors are also discussed.     

Exclusive deuteron electrodisintegration at high neutron recoil momentum

We have determined the ²H(e, e′p)n cross section for neutron recoil momenta between 295 and 500 MeV/c. In this region the ³D₁ state contribution is predominant in the deuteron wave function. The high excitation energy (E_cm^np = 179 MeV) and the small momentum transferred (|;q_cm|;² = 1.66 fm^?) emphasize the influence of isobar configurations (IC). Experimental data are compared with calculations including isobar contributions, mesonic exchange currents and final state interactions.     

Probing the high momentum component of the deuteron at high Q2

The (2)H(e,e'p)n cross section at a momentum transfer of 3.5 (GeV/c)(2) was measured over a kinematical range that made it possible to study this reaction for a set of fixed missing momenta as a function of the neutron recoil angle θ(nq) and to extract missing momentum distributions for fixed values of θ(nq) up to 0.55 GeV/c. In the region of 35°≤θ(nq)≤45° recent calculations, which predict that final-state interactions are small, agree reasonably well with the experimental data. Therefore, these experimental reduced cross sections provide direct access to the high momentum component of the deuteron momentum distribution in exclusive deuteron electrodisintegration.     

Relativistic effects in electromagnetic meson-exchange currents for one-particle emission reactions

Following recent studies of non-relativistic reductions of the single-nucleon electromagnetic current operator, here we extend the treatment to include meson-exchange current operators. We focus on one-particle emission electronuclear reactions. In contrast to the traditional scheme where approximations are made for the transferred momentum, transferred energy and momenta of the initial-state struck nucleons, we treat the problem exactly for the transferred energy and momentum, thus obtaining new current operators which retain important aspects of relativity not taken into account in the traditional non-relativistic reductions. We calculate the matrix elements of our current operators between the Fermi sphere and a particle-hole state for several choices of kinematics. We present a comparison between our results using approximate current operators and those obtained using the fully relativistic operators, as well as with results obtained using the traditional non-relativistic current operators.     

Neutron-proton elastic scattering at high energies and small momentum transfers

It is shown that the most recent measurements of differential cross-section at small momentum transfers, integrated and total cross-sections, and the slope of np elastic scattering from 100 to 400 GeV/c are successfully fitted by using the simple Regge pole model proposed by the authors several years ago.     

Measurement of np elastic scattering at high energies and very small momentum transfers

The np elastic differential cross section has been measured for incident neutron momenta 100–400 GeV/c in the |t| range 6 · 10^?6 ? 5 · 10^?1 (GeV/c)². The np data of this experiment provide a first direct measurement of the hadronic amplitude for |t| < 10^?2 (GeV/c)², which is consistent with the extrapolations from higher |t| values. Our data for |t| < 10^?4 (GeV/c)² are consistent with a rise which can be attributed to Schwinger scattering, caused by the interaction of the neutron magnetic moment with the proton.     

Non-perturbative QCD effects at large momentum transfers

We calculate the simplest one-instanton correction to the perturbative QCD prediction for e⁺e^? annihilation to hadrons. At high centre-of-mass energies Q we find a contribution to the total cross section from a simple fermion loop of the form

$\text{δR}\text{R}\text{∝}\text{Q}{}^2\text{→∞}\text{Q}{}^{\mathrm{<mtext>?11?</mtext><mtext>Nf</mtext><mtext>3</mtext>}}\text{(1n Q}{}^2\text{)}{}^{\mathrm{<mtext>6(33?4Nf)</mtext><mtext>(33?2Nf)</mtext><mtext>or</mtext>}}\text{(1n Q}{}^2\text{)}{}^{\mathrm{<mtext>6(33?4Nf)</mtext><mtext>(33?2Nf)?1</mtext>}}$

where N_f is the number of quark flavours. The numerical value of this contribution is O(1) for Q ～ 1 to 2 GeV.     

High momentum component in the deuteron

The high momentum component in the deuteron, which stems from the short range part of the nucleon-nucleon interaction, is studied in they-scaling function and the structure functionF ₂ of the deuteron. We use not only some non-relativistic wave functions but also relativistic ones. It is shown that the relativistic mechanism or a six-quark state in the nucleon-nucleon interaction yields a large high momentum component.     

The four-momentum transfer distribution for the deuteron break up at 3.3 GeV/c incident deuteron momentum

The differential cross section (dσ/dt) for the dp → ppn charge retention reaction at 3.3 GeV/c deuteron momentum is studied and compared with the Glauber multiple scattering theory. Within the limits of the uncertainties of the existing elementary nucleon-nucleon data, the simple Glauber model calculations give, in general, a fair agreement with experiment, except for the low |t| region where possible spin effects may play a role.     

Energy and angular momentum transfers from an electromagnetic wave to a copper ring in the UHF band

Electromagnetic waves could carry orbital angular momentum. Such momentum can be transferred to macroscopic objects and can make them rotate under a constant torque. Based on experimental observations, we investigate the origin of orbital angular momentum and energy transfer. Due to angular momentum and energy conservation, we show that angular momentum transfer is due to the change in the sign of angular momentum upon reflection. This leads to a rotational Doppler shift of the electromagnetic wave frequency, ensuring energy conservation.     

A new contribution to deuteron screening at high energies

Effects arising from the structure of the Pomeron are shown to lead to a decrease in the apparent size of the Glauber screening correction to the π-d total cross section. This decrease is large enough to partially cancel effects arising from the usual inelastic intermediate state corrections to Glauber.