Deep Inelastic Electron Scattering Research Articles

The parton model and its applications

This is a review of the program we started in 1968 to understand and generalize Bjorken scaling and Feynman's parton model in a canonical quantum field theory. It is shown that the parton model proposed for deep inelastic electron scatterings can be derived if a transverse momentum cutoff is imposed on all particles in the theory so that the impulse approximation holds. The deep inelastic electron–positron annihilation into a nucleon plus anything else is related by the crossing symmetry of quantum field theory to the deep inelastic electron–nucleon scattering. We have investigated the implication of crossing symmetry and found that the structure functions satisfy a scaling behavior analogous to the Bjorken limit for deep inelastic electron scattering. We then find that massive lepton pair production in collisions of two high energy hadrons can be treated by the parton model with an interesting scaling behavior for the differential cross-sections. This turns out to be the first example of a class of hard processes involving two initial hadrons.

The color dipole picture of low-x DIS

Deep inelastic electron scattering (DIS) from nucleons at low values of the Bjorken variable $x \cong Q^2/W^2 \lsim ~ 0.1$ proceeds via fluctuations of the photon into quark-antiquark dipole states that subsequently interact with the gluon field in the nucleon. Dependent on the interaction energy, $W$, the color-gauge-invariant dipole interaction with the gluon field in the nucleon, for any fixed dipole size, contains the limits of i) color transparency and ii) saturation, where "saturation" stands for the approach to a hadronlike dipole-proton interaction cross section. All essential features of the experimental results on low-x DIS, as a consequence of the color-gauge-invariant dipole interaction follow model independently i.e. without specific ansatz for the dipole cross section. The model-independent results in particular include the low-x scaling behavior of the photoabsorption cross section, $\sigma_{\gamma^*p} (W^2,Q^2) = \sigma_{\gamma^*p} (\eta (W^2,Q^2))$, with definite functional dependence on the low-x scaling variable $\eta (W^2,Q^2) \cong Q^2/\Lambda^2_{sat} (W^2)$ in the limits of $\eta (W^2,Q^2) \gg 1$ and $\eta (W^2,Q^2) \ll 1$, respectively. Consistency with the pQCD-improved parton model implies the definite value of $C_2 \cong 0.29$ for the exponent in the "saturation scale", $\Lambda^2_{sat} (W^2) \approx (W^2)^{C_2}$. The longitudinal-to-transverse ratio of the photoabsorption cross section at large $Q^2$ has the definite value of $R = 1/2 \rho$ with $\rho = 4/3$. For $W^2 \to \infty$ at any fixed $Q^2$, the photoabsorption cross section converges towards a $Q^2$-independent saturation limit that coincides with the cross section for $Q^2 = 0$ photoproduction.

The Role of the Quark from Deep Inelastic Electron and Muon Scattering Experiments

Deep inelastic charged lepton scattering has provided the main experimental evidence that the nucleon contains constituents which behave like point-like particles. The original concept of approximate scaling and the concept of scale-breaking were determined in new energy regions, and illustrate the importance of measuring over large kinematic ranges. The idea that the constituents were indeed the quarks of the strong interactions was the first step in the development of a theory which embraces properties of the strong, electromagnetic and weak interactions, i.e. quantum chromodynamics. The aim of this talk is to indicate the various stages in this development as given by deep inelastic charged lepton scattering.

Deep-Inelastic Electron Scattering fromC12

A systematic study of the deep-inelastic electron-scattering response function of /sup 12/C has been carried out at scattering angles of 60/sup 0/ and 130/sup 0/ and electron energies between 160 and 520 MeV. A pronounced transverse strength, the origin of which is not understood, is found in the region between the quasielastic and the N peak.

Residual Proton Production in Deep-Inelastic Electron Scattering

We have measured residual proton yields from deep-inelastic electron scattering as a function of the fractional longitudinal momentum, ${z}_{p} (=\frac{{p}_{l}}{{p}_{lmax}})$, imparted to the proton. We find a peaked distribution in ${z}_{p}$ centered near ${z}_{p}=\ensuremath{-}0.25$.

Surface Dominance in Deep-Inelastic Electron Scattering

Let a finite part of the scaling curve $\ensuremath{\nu}{W}_{2}({\ensuremath{\omega}}^{\ensuremath{'}})$ at low ${\ensuremath{\omega}}^{\ensuremath{'}}$ be locally dual to a set of resonances obeying a mass formula ${{M}_{n}}^{2}=a+{{m}_{0}}^{2}n$. Then it is shown that a simple way of satisfying this condition within the context of several models is that the contributing resonances satisfy the condition $j\ensuremath{\sim}\sqrt{s}$.

Conjecture on the Approach to Scaling in Deep-Inelastic Electron Scattering and Some Comments on Electromagnetic Mass Differences

Conjecture on the Approach to Scaling in Deep-Inelastic Electron Scattering and Some Comments on Electromagnetic Mass Differences

Partons and Deep-Inelastic Electron Scattering

A new parton model is defined. Two predictions are obtained for deep-inelastic $e\ensuremath{-}p$ scattering: (1) At an inyariant momentum transfer $\ensuremath{-}{Q}^{2}$ of 1 ${\mathrm{GeV}}^{2}$, at least half the final states will contain a $K$ meson. (2) For a value of $\ensuremath{-}{Q}^{2}$ somewhere between 8 and 30 ${\mathrm{GeV}}^{2}$ the Bjorken scaling prediction will be violated and a large fraction of the final states will contain an antibaryon.

Direct-Channel Resonance Model of Deep-Inelastic Electron Scattering. I. Scattering on Unpolarized Targets

We construct a resonance model of deep-inelastic electron scattering. Using semiempirical rules for the form of the nucleon spectrum and a universality hypothesis for the transition form factors, we obtain explicit expressions for the structure functions ${W}_{1}$ and ${W}_{2}$ in the Bjorken limit. The ratio of the longitudinal to transverse photoabsorption cross sections vanishes for large momentum transfers, and $\ensuremath{\nu}{W}_{2}$ becomes scale invariant. A one-parameter fit is obtained to $\ensuremath{\nu}{W}_{2}$ (proton), and a zero-parameter prediction is made of $\ensuremath{\nu}{W}_{2}$ (proton)-$\ensuremath{\nu}{W}_{2}$ (neutron). There is good agreement between the theory and experiment in the region where scale invariance is well established.

Direct-Channel Resonance Model of Deep-Inelastic Electron Scattering. II. Spin Dependence of the Cross Section

The spin dependence of the cross section of deep-inelastic electron (muon) scattering is investigated in the framework of the direct-channel resonance model. The structure functions entering the spin-dependent part of the cross section obey the following scaling laws in the Bjorken limit: $\ensuremath{\nu}{W}_{3}$ is a function of $\ensuremath{\omega}$, and $\ensuremath{\nu}{W}_{4}={W}_{3}$. The polarization asymmetry is calculated in the framework of a quark model with orbital excitations; sizable asymmetries are predicted. The spin-dependent part of the cross section is found to be strongly model dependent; therefore, polarized-beam-polarized-target experiments should be able to distinguish between various models.