CERN ISR Research Articles

Composite structure of the nucleon

The nonlinear σ-model with vector mesons introduced as gauge bosons and an interacting chiral quark sector depicts the nucleon as a topological soliton embedded in a chiral condensate. High-energy elastic pp and ¯pp scattering data from CERN ISR and SPS Collider appear to provide strong evidence in favor of this nucleon structure.

Nuclear fusion of protons with ions of boron

This paper describes a method of extracting energy from the fusion events occurring between the collision of a beam of protons with a beam of ions of11B. The two beams are circulating in separated and intersecting storage rings where they collide head-on in a common long-straight section. Requirements on the beam parameters in the collider are presented. Limitations due to space-charge forces are discussed; it is found necessary to provide beam-charge neutralization with electrons. The paper discusses also the effects of Coulomb scattering between particles of the same beam and in the opposing beams. Methods are proposed for controlling the electromagnetic interaction.

Generalized geometrical scaling behavior of elastic hadron-hadron scattering amplitudes at high energies.

A detailed comparison of the generalized geometrical scaling (GGS) hypothesis for elastic hadron-hadron scattering amplitudes is made with the measurements of differential cross sections of $\mathrm{pp}$ and $\overline{p}p$ scattering as well as ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p$ and ${K}^{\ifmmode\pm\else\textpm\fi{}}p$ scattering at high energies. The GGS predictions for $\mathrm{pp}$ and $\overline{p}p$ scattering show good agreement with the experiments in the energy range from the CERN Intersecting Storage Ring to the Fermilab Tevatron collider ($\sqrt{s}=20\ensuremath{-}1800$ GeV). In the region below 20 GeV, where we also analyze ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p$ and ${K}^{\ifmmode\pm\else\textpm\fi{}}p$ scattering, we observe GGS behavior down to \ensuremath{\sim} 10 GeV, especially for $\mathrm{pp}$ scattering.

Evidence forf 2 (1720) production in the reaction pomeron-pomeron→π+π−π+π−

Data are presented on pomeron-pomeron interactions which produce a central π+π−π+π− system in proton-proton collisions at √s=62 GeV at the CERN Intersecting Storage Rings. A spin-parity analysis of the π+π−π+π− system shows evidence for the production of the statef 2 (1720) with decay to ρ0π+π−. Since pomeron-pomeron interactions are expected to favor the production of gluonic bound states, observation of thef 2 (1720) supports earlier interpretations of it as a glueball. In addition, enhancements near threshold give indication of the statef 2 (1270) decaying to ρ0ρ0 and the statef 0 (1400) decaying to ρ0π+π−.

Generalized geometrical scaling for elastic hadron-hadron scattering at high energies.

We propose generalized geometrical scaling for elastic hadron-hadron scattering which has the scaling dimensional parameter $\sqrt{\frac{{\ensuremath{\sigma}}_{t}}{\ensuremath{\kappa}(x)}}$, $\ensuremath{\kappa}(x)$ being a function of the elasticity $x$ characteristic of the form of the eikonal. This hypothesis presents a unified explanation of the features of the differential cross sections of $\mathrm{pp}$ and $\overline{p}p$ scattering in the energy region from the CERN Intersecting Storage Ring to the Fermilab Tevatron collider with the eikonal corresponding to the dipole-type form factor.

High-energy elastic hadron scattering in Coulomb and hadronic regions.

The analysis of {ital pp} elastic scattering data at an energy of 53 GeV, reached at the CERN Intersecting Storage Rings, is performed with the help of a formula which is based on the impact parameter approach and is more general than the currently used formula of West and Yennie. More precise values of {sigma}{sub tot}, {ital B}, and {rho} are established (some of them differing from those derived earlier). The peripheral picture of elastic {ital pp} hadron scattering is shown to be fully consistent with experimental data; it seems even to be preferred.

Nonlinear σ-model and nucleon structure

The nonlinear σ-model with the Wess-Zumino action describes the nucleon as a soliton and incorporates the non-abelian chiral anomalies. Several studies have shown that the model works well except for the nucleon mass, which comes out consistently too large. We investigate this question beginning with the more general framework of the linear σ-model, which has besides a pseudoscalar meson sector, a fermion or quark sector, a scalar field and an interaction between the fermions via the scalar field. Using a path integral formulation, we express the fermion measure of the model as the product of a Jacobian and an invariant measure. Identifying this Jacobian as exp[iΓwz] , we find that the model breaks up into two parts, when in the pseudoscalar meson sector the scalar field is replaced by its vacuum value. The pseudoscalar part of the model becomes the nonlinear σ-model with the Wess-Zumino actionΓwz. The other part involves chiral fermions, the scalar field and their interaction. We continue this part back to the Minkowski space to determine its ground state and energy levels. We find that for a scalar field that vanishes at smallr, but rises sharply to its vacuum value at someR, the ground state energy of the interacting quark-scalar-field system can be lower than the ground state energy of the non-interacting quark system. This means the interaction between quarks and the scalar field can lead to a condensed ground state or vacuum and can reduce the overall energy of the system (a phase transition as in superconductivity). It is, therfore, not surprising that the nonlinear σ-model predicts too large a nucleon mass, since it implicitly assumes a normal non-interacting vacuum in the quark sector. Quarks are now quasiparticles that appear as excitations of the condensed vacuum. The nucleon structure that emerges from this investigation agrees fully with the phenomenological nucleon structure found from analysis of high energy elasticpp and\(\bar p\)p scattering at CERN ISR and SPS Collider.

Further evidence for pomeron-quark interactions: observation of large Λ 0 polarization in pp→( Λ0K +)p

We report an analysis of the diffractive reaction pp→( Λ 0K +)p, measured at r√ s=63 GeV in an open geometry forw spectrometer experiment at the CERN Intersecting Storage Rings. In the rest frame of the (Λ 0K +) system, which has nearly the beam momentum of 31.4 GeV, the Λ 0 is observed to be sharply peaked forward, similar to earlier observations in the reaction pp→( Λ 0 φ 0K +)p, which were interpreted as the first direct evidence for pomeron-quark interactions. A smaller backward peak is also observed which may be evidence for pomeron-diquark interactions. The polarization of the Λ 0 increases to more than 60% when the diffractive mass reaches ≈2.8 GeV.

High-flux x-ray undulator radiation from proposed B factory storage rings at Cornell University

Two intersecting storage rings (8 GeV, 1 A and 3.5 GeV, 2 A) have been proposed to be built at Cornell University to enhance both the production of B mesons and synchrotron radiation. Exceedingly high x-ray flux from 3-m long undulators will be the new feature of a B factory for the CHESS laboratory. The flux produced integrated over the central cone of radiation can be as much as an order of magnitude higher than from the third-generation storage rings (now under construction) operating at 0.1 A.

Measurement of the π0π0 cross section in [formula omitted] annihilations at √ s ≈ 3.0 GeV

Data collected in the experiment R704 at the CERN ISR are used to study the annihilation process p p → π 0π 0 at several centre-of-mass energies between 2.97 and 3.56 GeV. A total sample of 7359 events has been identified, from which cross sections and angular distributions in the interval 0 < | cosθ ∗| < 0.5 have been measured.

Thepp- $$p\bar p$$ difference and the behaviour of phases at high energies

Predictions based on axiomatic field theory are obtained from the assumption that the difference between thepp and thep\(\bar p\) elastic scattering observed at the CERN ISR is caused by an “odderon-like” term in the scattering amplitude. A wide class of amplitudes violating the Pomeranchuk relation is considered. Contrary to common opinion, severe restrictions on the high-energy behaviour of the phase of the crossing-odd amplitude are shown to follow for the whole class. Less pronounced but still visible consequences follow for the phases of thepp andp\(\bar p\) amplitudes separately. We derive the corresponding high-energy bounds and correlations using the general frame of analyticity, crossing symmetry and unitarity. As a special case, the maximal odderon amplitude is discussed.

Higher order QCD effects and particle density in full phase space from highp T interactions at the ISR

A comparison of QCD parton models with events including a high transverse momentum trigger particle is performed. The data were obtained with the Split Field Magnet (SFM) detector at the CERN ISR. The effective intrinsic transverse momentum, 〈k T 〉, of a parton is found to be about 1 GeV/c from an analysis of inclusive cross sections based upon lowest order parton-parton scattering. Large values of 〈k T 〉 are also needed to obtain a good description of the particle density in the azimuthal hemisphere opposite to the trigger. The measured recoil of the spectator jets tends to require much smaller values of 〈k T 〉. The model is improved by including higher-order QCD effects. Thus, starting from 〈k T 〉=0.45 GeV/c, an effective 〈k T 〉 of about 1 GeV/c at hard scattering is generated through perturbative parton showers, which provides a consistent description of the measurements in full phase space. This analysis shows therefore that well-known problems of lowest-order QCD calculations can be resolved by inclusion of higher-order effects.

THREE-PARTICLE RAPIDITY CORRELATIONS IN PROTON-PROTON INTERACTIONS AT ISR ENERGIES

Measurements are presented of short range three-particle rapidity correlation in pp interactions at c.m. energies [Formula: see text], 44 and 62 GeV. The data were obtained at the CERN Intersecting Storage Rings (ISR) using the Split Field Magnet Detector (SFM) with a minimum bias trigger. Three-particle short range rapidity correlations are observed for the (-+-) and (+-+) combinations; no short-range correlation is observed for the (---) and (+++) configurations. The rapidity range of the three-particle correlations is approximately the same as for the two-particle correlations.

Pion interferometry testing the validity of hydrodynamical models

We show how a joint analysis of the transversal momentum spectrum, rapidity distributions and the interferometrical correlator can test and distinguish between different models of hydrodynamical expansion of matter. Our study shows that the hydrodynamical picture is inadequate for minimum bias events at CERN ISR energies. On the other hand, current data on ultra-relativistic nucleus-nucleus collisions are shown to be consistent with the existence of hydrodynamical flows in the matter formed in these processes. More complete and accurate interferometrical data is demanded for clarifying the matter evolution in time and space.

A study of massive electron pairs and associated particles produced at the CERN ISR

A sample of 105 e + e − events with an invariant mass greater than 11 GeV/ c 2 produced in pp collisions at a center-of-mass energy of 62.3 GeV is discussed. Cross sections are presented as a function of mass and transverse momentum. The multiplicity, transverse momentum, and azimuthal dependence of associated particles are also studied.

The reaction Pomeron-Pomeron →π + π − and an unusual production mechanism for thef 2 (1270)

Data are presented on Pomeron-Pomeron interactions which produce a centralπ+π− system in proton-proton collisions at\(\sqrt s = 62 GeV\) at the CERN Intersecting Storage Rings. This process may favor the production of gluonic bound states. A partial-wave analysis of theπ+π− system shows evidence for the production of the statesf0(975),f0(1400), andf2(1270). The fitted mass for thef2(1270) is about 50 MeV below the world average. In addition, the production mechanism for thef2(1270) is uniquely different from that for the other final states in that there is a correlation between the outgoing protons. this is consistent with a picture of two-gluon exchange with thef2(1270) produced by gluon fusion, and could indicate that thef2(1270) has a glueball component.

Quantum correlations in high-energy multihadron distributions.

We have used the Jaiswal and Mehta formulation as a model of hadronic multiplicity distributions to evaluate the joint forward-backward multiplicity distribution {ital P}({ital N}{sub {ital F}},{ital N}{sub {ital B}}) in hadronic interactions, where the underlying field includes a mixture of a coherent component and Gaussian noise. This allows us to investigate the effect of the quantum correlation length in rapidity on the strength of the forward-backward correlation, the validity of the binomial distribution for fixed {ital N}{sub {ital F}}+{ital N}{sub {ital B}}, and the Koba-Nielsen-Olesen distribution. The resultant parameters indicated that for the NA22 and CERN ISR regions, the relative noise content rises slowly with energy, while the correlation length also increases with the total width of the rapidity window.

A sensitive test of QCD from parton-parton scattering at the ISR

Production of jets with fast leading fragments has been studied in deep inelastic proton-proton interactions using the Split Field Magnet detector at the CERN ISR. The kinematics of the underlying parton processes is determined on an event-by-event basis. Parton scattering amplitudes are extracted for scattering angles, Θ ∗, in the interval −0.4 < cos Θ ∗ < 0.9 . The data which are known to be dominated by quark gluon scattering, agree with predictions from lowest order QCD, while e.g. an abelian theory can be excluded.

Jet physics at the CERN intersecting storage rings

Jet physics at the CERN intersecting storage rings

Some aspects of the structure of pp(p-barp) scattering at high energy.

The structure of the high-energy inelastic cross section of {ital pp} ({ital {bar p}p}) scattering are extensively discussed in terms of the basic quantum-geometrodynamics/anisotropic-chromodynamics mechanism. Predictions on the general structure of final states (charged-particle multiplicities and pseudorapidity distributions) are compared with experimental data at CERN ISR and CERN Collider energies, showing excellent agreement.