Angular distributions and structure functions from two-jet events at the CERN SPS pp collider

The two-jet cross section measured in the UA1 apparatus at the CERN $\text{p}\text{p}$ Collider has been analysed in terms of the centre-of-mass scattering angle θ and the scaled longitudinal parton momenta x₁ and x₂. The angular distribution dσ/d cos σ rises rapidly as cos → 1, independent of x₂ and x₂, as expected in vector gluon theories (QCD). The differential cross section in x₁ and x₂ is consistent with factorization and provides a measurement of the proton structure function $\text{F(x) = G(x) +}\text{4}\text{9}\text{[Q(x) +}\text{Q}\text{(x)]}$ at values of the four-momentum transfer squared, -t? ≈ 2000 GeV². Over the range x = 0.10?0.80 the structure function shows an exponential x dependence and may be parametrized by the form F(x) = 6.2 exp (?9.5x).     

Inclusive Λ, Λ and Σ±(1385) production in 405 GeV/c pp interactions

We have investigated inclusive Λ, $\text{Λ}$ and Σ^±(1385) productions in 405 GeV/c pp interactions. The observed cross sections are σ(Λ)=4.05±0.39 mb, $\text{σ(}\text{Λ}\text{=0.63±0.17}$ mb, σ(Σ⁺(1385))=0.74±0.17 mb and σ(Λ^?(1385))=0.56±0.17 mb. $\text{Λ}$ production is dominant in a central region of ∣x∣≤0.4. The $\text{Λ/}\text{Λ}$ production ratio at ∣x∣≈0 is found to be 1.2±0.5. The excess, about 0.2 mb, of σ(Λ⁺(1385)) over σ(Λ^?(1385)) is most likely attributed to proton fragmentations (∣x∣≥0.4), and gives an evidence for scaling.     

Experimental comparison of Jψ production by π±, K±, p and p̄ beams at 39.5 GeV/c

Measurements have been made of relative production cross sections of the $\text{J}\text{ψ}$ by π^±, K^±, p and p? at 39.5 GeV/c incident on copper. $\text{J}\text{ψ}$ production rates from π^?, K^? and p? are similar. The $\text{J}\text{ψ}$ relative particle/anti-particle production cross sections for x>0 are $\text{σ(π}{}^{\mathrm{+}}\text{)}\text{σ(π}{}^{\mathrm{?}}\text{)=(0.87±0.14)}$, σ(K⁺)/σ(K^?)=(0.85±0.5) and $\text{σ(}\text{p}\text{)}\text{σ(}\text{p}\text{?}\text{)=(0.15 ±0.08)}$. The small p/p? cross section ratio disagrees with models of J/ψ production by gluon amalgamation.     

Recoil implantation from a thin source: I. Underlying theory and numerical results

Recoil implantation from a monolayer source, for example an adsorbed layer or a layer of altered stoichiometry, is considered. We introduce the incident ion current I, the fractional surface coverage characterizing the recoil source θ, the differential scattering cross-section dσ, and the integral distribution function F(x, ψ) for recoil-source atoms entering the target at angle ψ and stopping beyond x. The number of atoms implanted beyond x follows as $\text{H(x) = IθλN? σ F(x,ψ)}$. The receding of the target surface at velocity υ due to sputtering can be allowed for by integrating over $\text{x: H(x, t) = (}\text{1}\text{υ}\text{) ∫ H(x′)dx′}$. For very high doses the result is a steady-state situation in which the number of implanted atoms is given by H(x, ∞). Numerical results of four kinds are presented: H(x, H(x, ∞), the half-time for the build-up of the steady-state situation, and the half-depth of the implanted atoms, in all cases for oxygen on the surface of Be, Al, Mo and W.     

Testing QCD

QCD is used to predict that the ratio of up to down quarks → 5 as x → 1 and the rigor of the proof and the underlying assumptions are discussed. Measuring $\text{σ}{}^{\mathrm{<mtext>v</mtext><mtext>?</mtext>}}\text{P}\text{σ}{}^{\mathrm{v}}\text{P}\text{as}\text{x → 1}$ gives the best experimental test of this prediction.     

Scaling function for two-point correlations with long-range interactions to order 1/η

The two-point correlation function ? (q, ξ) is calculated in the critical region of momentum space q in terms of a suitable correlation lenght ξ, by means of perturbation expansion to order 1/n, for an n-vector system with long-range interactions decaying as $\text{|}\text{R}\text{/a|}{}^{\mathrm{?(d\; +\; \sigma )}}$, for $\text{|}\text{R}\text{/a|}\text{a}\text{?}\text{1}$, where a is the spacing on a d-dimensional lattice, σ < d < 2σ and 0 < σ ? 2 ? η_SR. The calculations are done in zero field for T ? T_c. Explicit expansions for long-range propagators are developed for $\text{σ « 1}$ and for the neighborhood of σ ? 2 ? η_SR, in terms of which a universal, cut-off independent scaling function is obtained over the whole range of $\text{x = |}\text{q}\text{| ξ}$, and it is shown that the amplitude of the correlation-length dependence of the susceptibility becomes a universal parameter. Both the exponents and the coefficients of the expansion for fixed q as $\text{(T ? T}{}_{\mathrm{<mtext>c</mtext>}}\text{)}\text{T}{}_{\mathrm{<mtext>c</mtext>}}\text{→0}$ are calculated explicitly. The former are shown to require the validity of the operator-product expansion and explicit logarithmic correction terms are obtained for $\text{d = d}{}^1\text{= 3σ/2}$. For these and other dimensionalities, the coefficients are shown to be finite functions of d and σ. The correction to the Ornstein-Zernike form is given explicitly, with non-integer powers of x that have finite coefficients.     

Non-diffractive Pomeron renormalization,multiplicities, and the topological expansion

The renormalization of the Pomeron due to nondiffractive K$\text{K}$, B$\text{B}$ production thresholds is considered within a simple generalization of the Chew-Rosenzweig multiperipheral realization of Veneziano's topological expansion. The results are consistent with the existence of both the “low-energy” bare Pomeron with intercept $\text{α=0.85}$ and Gribov bare Pomeron with intercept above one. The vacuum exchange part of 2σ_KN?σ_πN basically rises with energy. Qualitatively correct features of shrinkage and breaks of $\text{d}\text{σ}\text{d}\text{t}$ emerge. The multiplicity of product clusters (n) increases with energy faster than 1ns and agrees with experiment for an average number of particles per cluster of 3–4. Independently of our model the Harari-Freund multiperipheral realization of the topological expansion is shown to be in serious difficulty with multiplicities, requiring around 20 particles per cluster.     

Rising dσdt probes pp diffraction mechanisms

The s-dependence of $\text{d}\text{σ}\text{d}\text{t}$ at fixed t reveals important features of the underlying mechanism. In particular, it can clarify the origin of the structure near t = ?1.2 in high-energy pp elastic scattering. If this structure comes from destructive interference between two terms of different energy dependence (e.g. between single and double pomeron exchanges), the plot of ln $\text{d}\text{σ}\text{d}\text{t}$versus ln s in the interference region will show an inflexion or dip; $\text{d}\text{σ}\text{d}\text{t}$ may even rise with increasing s through a limited interval. Other mechanisms have no such feature. We give illustrations and stress the interest of measurements in the NAL and ISR momentum range.     

Spin-flip and resistivity scattering of conduction electrons due to metallic impurities dissolved in lithium and sodium

We analyse the impurity induced scattering cross sections with (σ_sf) or without (σ_r) spin-flip, for conduction electrons in lithium and sodium. We show that the experimental values of $\text{σ}{}_{\mathrm{sf}}\text{σ}{}_{\mathrm{r}}$, are approximately equal to the Elliott parameter $\text{(}\text{λ}\text{Δ}\text{)}{}^2$ (λ is the spin-orbit splitting of an impurity state (A) close to the impurity conduction band (C), and Δ is the energy separation between (C) and (A). We conclude that the Elliott calculation is valid not only for a spin-independent scattering potential, but also for the perturbation due to heavy impurities (strong spin-orbit coupling) dissolved in light metals (weak spin-orbit coupling).     

Determination of the angular and energy dependence of hard constituent scattering from π0 pair events at the CERN intersecting storage rings

We present data on proton-proton collisions, obtained at the CERN Intersecting Storage Rings, in which two roughly back-to-back π⁰'s of high transverse momentum (p_T) were produced. The angular distribution of the dipion axis relative to the collision axis is found to be independent of both the effective mass m of the dipion system and the centre-of-mass energy √s of the proton-proton collision. The cross-sections $\text{d}\text{σ}\text{d}\text{m}$ at the values of √s satisfy a scaling law of the form $\text{d}\text{σ}\text{d}\text{m}\text{=}\text{G(x)}\text{m}{}^{\mathrm{n}}\text{,}\text{where}\text{x = m(π}{}^0\text{, π}{}^0\text{)//trs}\text{and}\text{n = 6.5 ± 0.5}$. We show from our data that the leading π⁰ carries most of the momentum of the scattered parton. Given this fact, the axis of the dipion system follows closely the direction of the scattered constituents, and we exploit this to determine the angular dependence of the hard-scattering subprocess. We also compare our data with the lowest order QCD predictions using structure functions as determined in deep-inelastic scattering and fragmentation functions from electron-positron annihilation.     

Λ and Λ production in K+p interactions at 32 GeV/c

A study of the inclusive and semi-inclusive Λ and $\text{Λ}$ production in K⁺p interactions at 32 GeV/c is presented. The inclusive cross sections for Λ and $\text{Λ}$ amount to 0.78 ± 0.05 and 0.42 ± 0.04 mb thus showing a remarkable growth between 16 and 32 GeV/c with a factor of 1.7 for Λ and 2.8 for $\text{Λ}$. Target and beam fragmentation processes are found to be dominant for Λ and $\text{Λ}$ production respectively with the following lower limits for the corresponding cross sections: $\text{σ(p}\text{→}\text{K}{}^{\mathrm{+}}\text{?) > 0.5}\text{mb}$ and $\text{σ(K}{}^{\mathrm{+}}\text{→}\text{p}\text{?}\text{) > 0.3}\text{mb}$. Although the early scaling conditions are fulfilled for the Λ production in the target fragmentation region, and $\text{Λ}$ production in the beam fragmentation region, scaling is not observed between 16 and 32 GeV/c in the x and p_T² Feynman variables. The Λ production is found to be very similar in the K⁺p inclusive reaction at 32 GeV/c and in the semi-inclusive reaction $\text{K}{}^{\mathrm{?}}\text{p}\text{→ Λ}\text{K}\text{K}\text{X}$ at the same energy. The $\text{Λ}\text{Λ}$ pair production cross section increases significantly in K⁺p interactions from 16 to 32 GeV/c where it reaches the value $\text{σ}{}_{\mathrm{<mtext>\Lambda </mtext><mtext>\Lambda </mtext>}}\text{= 47 ± 11 μ}\text{b}$. The cross sections for Λ or $\text{Λ}$ produced in association with an identified proton are also given and discussed.     

A new organic low temperature conductor: HMTSF-TNAP

Conductivity and optical data on a new organic, conducting charge transfer salt Δ^{2, 2′}-Bi-(4,5-trimethylene-1,3-diselenole) 11,11′,12,12′-tetracyano-2, 6-napthoquinodimethane (HMTSF-TNAP) are given. $\text{σ(300}\text{K}\text{)= 2400 ± 600 Ω}{}^{-1}\text{cm}{}^{-1}$. A maximum in σ(T) is found at T_M = 47 K with σ(T_M)/σ(300 K) = 6.0 ± 10%, and $\text{σ(1.5}\text{K}\text{) > 250 Ω}{}^{-1}$. σ(T) is well defined in the high temperature region, but is sample dependent at low temperatures. The optical data indicate a bandwidth and carrier density comparable to that of HMTSF-TCNQ.     

Nonrelativistic distorted wave born approximation predictions for 500 MeV (p, p') spin-rotation observables

We discuss couplings of scalar gluonium σ on the basis of the low energy theorems of broken chiral symmetry and the anomalous trace of the energy—momentum tensor, implemented using a phenomenological lagrangian. Taking the ITEP value of the gluon consensate as input, we find $\text{Γ(σ → ππ) ? 0.6}\text{GeV}\text{× (}\text{m}{}_{\mathrm{\sigma }}\text{1}\text{GeV}\text{)}{}^5$ and $\text{Γ(σ → γγ) ? 90}\text{eV}\text{× (}\text{m}{}_{\mathrm{\sigma }}\text{1}\text{GeV}\text{)}{}^5$, while m_σ is undetermined. These results suggest that if the scalar gluonium mass is above 1 GeV, it is probably unobservably wide, while production in γγ collisions is probably too small to be detectable if m_σ < 1.5 GeV. We comment on the observability of J/ψ → σ + γ and on the relevance of our results to other gluonia.     

A note on the minimally coupled Bhabha field

The Bhabha field with multimass and maximum spin S, a system transforming reducibly under a representation of the homogenous Lorentz group is considered. The field is quantized in the presence of a minimally coupled electromagnetic field. The relation $\text{ψ(x)=ψ(}\text{x}\text{σ}\text{)}$ does not hold for the case of S integer contrary to the half-integer S or lower spin (S<) case, but the usual difficulties of high spin field theories seem to be absent. The propagation of the interacting (classical) equations is casual, since their principal part is unaffected by the introduction of an interaction, analogous to the lower spin case. This good nature of the Bhabha field equations appears due to the absence of secondary constraints. This is further supported with a similar example of a vector-spinor field.     

The surface critical exponent η⊥ in the two dimensional Ising model

The asymptotic decay of the two point diagonal correlation function «σ₀₀σ_NNå ～ N-(d-2)-η at T_c is analysed in the two dimensional Ising model with boundaries. The scaling estimate $\text{η⊥ =}\text{5}\text{8}$ is confirmed by rigorous calculations.     

Rising total cross sections and the flavoring of the pomeron

The relationship of the non-diffractive renormalization of the bare pomeron via$\text{K}\text{K}$ and $\text{B}\text{B}$ production - or its “flavoring” by λ quark loops and di-quark loops - and the shape of the NN total cross section is studied in some detail. The “unflavored” bare pomeron P? generated by non-strange quark loops with intercept $\text{α}\text{=0.85}$ is non-diffractively renormalized into the “flavored” (Gribov) bare pomeron P with intercept α above one (α = 1.06 here). We utilize inclusive data on $\text{K}\text{K}\text{and}\text{B}\text{B}$ production as well as inelastic diffraction to constrain parameters, and we fit the combination $\text{1}\text{2}\text{(σ}{}_{\mathrm{<mtext>pp</mtext>}}\text{+ σ}{}_{\mathrm{<mtext>p</mtext><mtext>p</mtext>}}\text{)}$ from s = 10 GeV² through ISR energies, including the new Fermilab data, to high accuracy. No pronounced long wavelength oscillations are observed. We suggest that these data favor the Chew-Rosenzweig realization of the topological expansion over that of Harari-Freund. We show that our scheme is consistent with the rising behavior of 2σ_KN ? σ_πN.     

Nuclear excitation by electrons and positrons

Existing measurements of the ratio $\text{σ}{}^{\mathrm{?}}\text{σ}{}^{\mathrm{+}}$, the nuclear excitation cross sections produced by electrons and positrons, are compared with the results of distorted wave calculations. The behaviour as a function of atomic number Z and electron energy E₀ is shown to be principally due to Coulomb distortion. The value of $\text{σ}{}^{\mathrm{?}}\text{σ}{}^{\mathrm{+}}$ displays no clear structure corresponding to resonances in the photoabsorption cross section, except that it should be quite sensitive to the presence of quadrupole strength.