The complete O(ɛ2) reggeon field theory scaling law dσel/dt and its applications at collider energies

We give the complete asymptotic reggeon field theory (RFT) scaling law for the elastic cross section in O(?²), extending previous results to include the 3-pomeron cut. This provides the most detailed realistic test of this theory. Numerically we find the encouraging result that the small-t SPS collider data for dσ_el/dt are in agreement with these new asymptotic RFT predictions. However, ISR data are not compatible with this theory, either in s or t dependence. Previous positive ISR results were largely due to the existence of a j = 1 fixed cut which is not present here. Our results, coupled with the observation that critical RFT fits to σ_tot require large non-leading terms, imply that a lower bound for the RFT asymptotic scale in single renormalized propagator processes (σ_tot,dσ_el/dt) lies around SPS-collider energies. The asymptotic scale for multi-propagator processes (the rapidity plateau, ab→aX reactions, multiplicity distributions etc.) is expected to be well beyond the SPS collider. A possible global RFT picture is them that perturbation theory (including finite rapidity scale effects due to the excitation of new quantum numbers) is applicable through ISR and up to the SPS collider, consistent with recent observations. The critical RFT can become the relevant diffractive theory for σ_tot and dσ_el/dt at larger t at and above the SPS collider. Predictions for dσ_el/dt at larger t at the SPS collider are given in this paper and we urge experimentalists to test them.     

Hadron weak interactions at high energy and the parton model

It is shown that, within the parton picture, weak (P-odd) effects increase with energy and momentum transfer. The presence of an effctive current with ΔS = 0 and 1 due to constituent interchange or annihilation is expected in the parton picture of hadron-hadron weak interactions. A typical value of P-odd effects, nucleon or hyperon polarization or asymmetry in quasi two-body reactions is about 10^?4 at E_lab ～ 10³ GeV and 10^?3 in large angle (t ～ s) scattering in the conventional current × current scheme of weak interactions. A principal possibility to clear up quark statistics is pointed out.     

Universality of the rate of growth of all hadron-nucleon total cross sections in the range 10 to 1500 GeV/c

The energy dependence of total cross section of hadron-nucleon collisions has been studied in terms of two components: the first component decreases with increasing energy of the incident hadron whereas the second component increases like ln s. The coefficient of ln s is found to be the same within 5% for p^±p, π^±p and K^±p collisions. The rate of growth of the rising component i.e., dσ /d(ln,s), of inelastic cross sections, deduced from σ_tot and σ_el, of pp and πp are found to be the same within 1.5 standard deviations; an attempt has been made to understand this near equality from factorization of the pomeron.     

Transverse momentum of jets in electroproduction from quantum chromodynamics

Detailed predictions of QCD on transverse momentum distributions of jets in leptoproduction are presented. The average p_⊥² is found to be asymptotically proportional to W² (the hadronic invariant mass squared) with a coefficient function that depends little on x and y. Contributions from gluons in the nucleon are relatively smaller than for σ_L/σ_T.     

The two gluon exchange model forγγ interactions at high energies

The work presents the model of γγ point-like interactions via the two gluon exchange. The model is developed using the Sudakov techniques for the high energy limit. Its predictions for the experimentally measured quantities of σ _inclusive ^tot and the structure functionF ₂(x, Q ²) are found in a good agreement with the predictions of GVDM model. Used together with the QPM it can explain the experimental data for the whole kinematical region available in the recent experiments.     

Semi-hard QCD: Minijets and elastic scattering

Starting from the QCD calculation of the amplitude for semi-hard interactions we establish a quantitative correlation between the growth of the cross section for minijet production and the changes in the pp̄ elastic differential cross section between ISR and Spp̄S collider energies. The fact that the semi-hard amplitude is central plays an essential role. The predicted behaviour for σ_tot, σ_tot/σ_tot, ϱ and dσ/dt at higher energies is presented.     

Studying gluon properties experimentally

We argue in this paper the following. (i) A large part of what is observed in high-energy hadron reactions may be rather directly interpretable in terms of gluon interactions. Since gluons do not interact directly with leptons and photons this could be a valuable way to study them experimentally. Earlier work in this direction is briefly summarized. We suggest how several quantities can be reinterpreted in terms of gluon interactions; the rise in σ_tot, and the more rapid increase of multiplicity with energy at very high energies, are particularly fruitful to examine. The possibility of interpreting inclusive polarization data in terms of gluon spin properties is considered. Most importantly, we propose that if certain of our predictions on central region particle ratios are correct, then the gluon distribution as a function of x may be measurable at energies in the ISABELLE range. (ii) The structure of gluon jets in mass, multiplicity and momentum is discussed; we suggest that gluon jets will be quite different from quark jets, with more of the energy of the gluon jet going into mass, so hard gluon jets may not exist.     

The n-loop expansion of the Reggeon calculus

We apply the technique known in solid state physics as the n-loop expansion to calculate the critical indices of the φ³ Gribov Reggeon calculus directly in two transverse dimensions. Infrared pathologies of the massless theory require the calculation to be done in the infinite momentum limit of the massive theory. For n = 1 the results are close to those of the ε-expansion in O(ε). For n = 2 the β function has no zero, analogously to the case in solid state physics. Use of a Padé approximant for β yields σ_tot ≈ (1n s)^0.27 at infinity, close to the O(ε²) result.     

Frequency Dependence of the Dielectric Loss Angle in Disordered Semiconductors in the Terahertz Frequency Range

Frequency dependence of the real part of the conductivity σ₁(ω) in the region of the transition from almost linear (s < 1) to quadratic (s ≈ 2) can indicate a change in the conduction mechanism (the transition from the variable-range to the fixed-range hopping with increasing frequency); in this case, the sharpness of the change in the slope of the frequency characteristic is related to the dependence of the preexponential factor of the resonance integral on the intercenter distance in the pair. The frequency dependence of the imaginary part of the conductivity σ₂(ω) has no kink in the vicinity of the transition frequency ωcr, remaining almost linear. A large dielectric loss angle |cotγ| = |σ₂|/σ₁ can indicate that the imaginary part of the conductivity at ω < ω_cr is defined by the larger zero-phonon contribution in σ₂^res the region of weak variation in the loss angle γ(ω), which significantly exceeds the relaxation contribution σ₂^res.     

Elastic electron deuteron scattering on a tensor polarized solid ND3 target

Elastic electron deuteron scattering has been measured at the Bonn 2.5 GeV electron-synchrotron using a tensor polarized ND₃ target. The scattered electrons and deuterons were detected in coincidence by two magnetic spectrometers. Data were taken at an average value of four momentum transfer ofQ ²=0.495 (GeV/c)² in order to separate the electric monopole and quadrupole form factors of the deuteron. To have a sufficient control of systematic effects, both polarized and unpolarized cross sections were measured with an identical experimental set up. In the ratioR _EXP=dσ_pol/dσ_unp systematic effects are expected to cancel. This ratioR _EXP is related to the theoretical polarized cross section d dσ _T where the spin quantization axis for the deuterons is orientated in the ed-scattering plane, perpendicular to the virtual photon direction. Our final result for the corresponding recoil tensor polarization ist ₂₀=?2.01±1.13.     

Evidence of a rise in the antiproton-proton total cross section at the CERN intersecting storage rings

We measured the total cross section for $\text{p}$p scattering at $\text{s}\text{= 52.8}\text{GeV}$ at the CERN ISR, using the direct, total-rate method. The result obtained, $\text{σ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(}\text{p}\text{p}\text{) = 44.70 ± 0.53}\text{mb}$, shows that, in common with σ_tot(pp), this cross section also starts to rise in the ISR energy range. We remeasured the total cross section for pp scattering at the same energy, obtaining σ_tot(pp) = 43.26 ± 0.33 mb, and found for the difference, $\text{Δσ}{}_{\mathrm{<mtext>tot</mtext>}}\text{= σ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(}\text{p}\text{p}\text{) ? σ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(}\text{pp}\text{)}$, a value of 1.44±0.45 mb.     

Static and high-frequency hole transport in <Emphasis Type="Italic">p</Emphasis>-Si/SiGe heterostructures in the extreme quantum limit

Complex high-frequency (HF), σ^AC = σ₁ ? iσ₂, and static, σ^DC, conductivities, as well as current-voltage characteristics, have been measured in p-Si/SiGe heterostructures with a low hole density (p = 8.2 × 10¹⁰ cm^?2) at temperatures T = 0.3–4.2 K in the ultraquantum limit, when the filling factor is v < 1. In order to determine the components of the HF conductivity, the acoustic contactless method in the “hybrid configuration” is used, when the surface acoustic wave propagates on the surface of the LiNbO₃ piezoelectric and the heterostructure is pressed to the surface by a spring. The conductivities σ₁ and σ₂ are determined from the damping and velocity of the surface acoustic waves that are measured simultaneously with varying the magnetic field. The revealed HF conductivity features—σ₁ ? |σ₂|, the negative sign of σ₂, the threshold behavior of the current-voltage characteristic, and the dependence I ∝ exp(-A/V ^0.3) in the subthreshold region—indicate the formation of a pinned Wigner crystal (glass) in the ultraquantum limit (T = 0.3–0.8 K, B > 14 T).     

A study of π− charge-exchange reactions on nuclei at 48 GeV/c

The charge-exchange cross sections were measured for π^? on Li, C, Al and Cu nuclei at momentum 48 GeV/c. By comparing the data obtained for nuclei with those for hydrogen under the same conditions the effective numbers of protons are defined. The conclusion is made that η⁰ mesons are absorbed in nuclei weaker then π⁰. The total cross section of η⁰ interactions with the nucleon is determined to be σ_tot(η⁰ N) = 15 ± 5 mb in agre ement with the quark model.     

On the change of polarization of positive muons in alkali halides

Positive muons implanted in nonconducting solids form with high probability hydrogenlike muonium atoms (µ ⁺ e ^–) with properties similar to those ofU ₂-centers. The influence of superhyperfine interactions with neighbor nuclei on the evolution of the polarization of the muon is investigated theoretically. The resulting muon polarization in longitudinal magnetic fields is calculated for muonicU ₂-centers in some alkali halides.     

On total photon cross sections and contributions of the new quark states

The vector dominance model is used to calculate the contributions of the ψ-family to total photon cross sections, the parameters being estimated from the radiative and leptonic decays of the ψ-states. This is found to be rather small when compared to the recent data of Caldwell et al. on σ_tot(γp) at Fermilab energies. To explain this discrepancy, it is then conjectured that, within the context of VDM, one may have to invoke the recently hypothesized multiquark states to give the observed increase in σ_tot(γp); upper limits are set on their contributions.     

Electrical and magnetic properties of single crystal [NEt4]2[CuII(mnt)2]

We report electrical and magnetic studies of [NEt₄]₂[Cu^II(mnt)₂]. This crystal is composed of chains of theplanar [Cu^II(mnt)₂]^?2 anions (space group $\text{P}\text{1}$ and z = 1) which exhibit only weak magnetic interactions. The material behaves as a semiconductor; from 300–400°K the conductivity increases by six orders of magnitude and the resistivity values above 300°K are comparable to those of some of the better known wide band-gap inorganic semiconductors. In contrast with the behavior of other linear chain systems, at room temperature the conductivity along the chain (σ_∥) is less than that perpendicular to the chain (σ_⊥). As the temperature is increase, the anisotropy ratio, σ_∥/σ_⊥, becomes greater than unity and increases to 1.6 × 10² at 400°K.     

Momentum conservation,time dependent Ginzburg Landau equation and paraconductivity

Superconductors exhibit increasing electrical conductivity as the temperature approachesT _c from above, due to superconducting fluctuations. The functions σ_f1=σ(ω, ?)-σ _n (ω), ?=(T-T _c )/T _c , have been derived by Schmidt phenomenologically using the time dependent Ginzburg-Landau equation (TDGL). These functions fail to vanish in the absolute clean limit τ → ∞ as they must. We have therefore reinvestigated the derivation of the linearized TDGL-equation and the corresponding current expression in the presence of a time dependent vector potential. We find several new terms, which are important for the rather clean superconductor only and are easily interpreted physically in terms of momentum conservation. Applying these corrected equations to the paraconductivity problem, we derive σ_fl(ω, ?) which has an extra factor (1 —iωτ)^?2 compared to Schmidt's result. There is also an additional term, which is connected to the problem of the contribution calculated by Maki. By comparison with the linear response function belowT _c , we show that this term is valid in the limit ¦ω¦?¦Δ¦ only and may not be continued to ω=0. There remains, however, a problem connected with this term, which cannot be solved within the present phenomenological framework.     

Total cross section for hadron production bye + e − annihilation between 9.4 and 9.5 GeV

The total cross section fore ⁺ e ^? annihilation into hadrons for center of mass energies from 9.4 to 9.5 GeV has been measured with the nonmagnetic DESY-Heidelberg detector at DORIS. A value ofR=σ_had/σ_µµ=3.8±0.7 for the continuum region around the Υ (9.46) resonance has been determined. The ratioΓ _ee Γ _had/Γ _tot of electronic, hadronic and total widths has been reevaluated to be (1.00±0.23) keV for the Υ resonance and (0.37±0.16) keV for the Υ′. In addition, a search for directly produced pohotons from Υ decays of the type Υ→γ+gluon+gluon has been performed. The Υ decay into muon pairs has also been searched for.     

Doubly radiative thermal neutron capture in 2H and 16O: Experiment and theory

Measurements and calculations are presented for the cross sections for two-photon emission following thermal neutron capture in ²H and ¹⁶O. Upper limits for σ_2γ were measured in both cases. For ²H, σ_2λ = 8 ± 15 μb, for γ-rays in the energy region 700 < E_γ < 5550 keV. A detailed threeparticle calculation gives σ_2γ^tot = 26 nb. For ¹⁶O, the experimental result is σ_2γ = 3 ± 19 μb for 1200 < E_γ < 2943 keV. A single-particle, direct-capture calculation for ¹⁶O gives σ_2γ^tot = 41 nb. Contributions from excitation of the giant dipole state of the core change this result by ± 16 %. In a separate measurement the total cross section for ¹⁶O(n, γ)¹⁷O was measured to be 202 ± 28 μb. Branching ratios of (82 ± 3)% and (18 ± 3)% were determined for decays to the 3055 and 871 keV levels of ¹⁷O, respectively.