Jet production from nuclei at 400 GeV/c

Results are presented from a calorimeter study on the production of jets in large-E_T proton-nucleus collisions at 400 GeV/c. Jet-like large-p_T events from eight nuclear targets are seen with a special jet trigger. As previously observed, the cross section for such events increases slightly faster than the atomic number, much like in the production of large-p_T single hadrons. Data on energy flows and multiplicities suggest that a heavy nucleus does not significantly widen the angular distribution of the beam remmants. In the central region the particle flow in hard nuclear collisions is similar to that in soft nuclear collisions.     

Renormalization of the axial anomaly operators

An expressionE(d ³ σ/dp ³)=Kp _T ^?n exp(?E/τ, wheren, K and τ are parameters to be fitted, has been used to represent the large-p _T hadron invariant single-particle inclusive cross sections. In most cases the fitting is within the quoted experimental uncertainties. An interpretation of the expression in terms of fireballs is given. Scaling is seen to be violated in large-p _T phenomena.     

Dual topology in large-pT reactions

We investigate a dual-string approach to the study of jets in large-p_T proton-proton collisions. The model is discussed for the dominant planar topology of valence quark-valence quark scattering where final hadrons may be viewed as fragments of two strings stretched between quarks and forward- or backward-moving diquarks. We assume that in the string c.m. frame, its fragments form a jet analogous to that observed in e⁺e^?→hadrons. Going back to the overall c.m. frame we recover the four-jet structure of large-p_T reactions. We discuss away side multiplicity distributions and show that the string approach which unifies the treatment of large-p_T and background secodaries, is equivalent to the naïve approach when the secondary momentum is large enough compared to its mass. Specific effects emerge for small enough momentum secondaries which result in widening of multiplicity rapidity distributions. Comparison with ISR data shows that this improves the agreement with experiment. Non-dominant contributions are also briefly considered.     

On the anomalous large transverse energy events observed in proton-lead scattering

It has been shown that a study of correlation between the average rapidity, 〈y〉, and transverse energy,E _T , can be used to distinguish between different origins of large transverse energy events observed inp-Pb scattering in the HELIOS experiment. If the largeE _T events are to be attributed to a nuclear dependence of structure functions then the hard scattering picture implies a positive correlation among the above two quantities, contrary to that seen in experiment.     

Stripe fluctuations, carriers, spectroscopies, transport, and BCS-BEC crossover in the high-Tc cuprates

The quasiparticles of the high-T_c cuprates are found to consist of: polaron-like ‘stripons’ carrying charge, and associated primarily with large-U orbitals in stripe-like inhomogeneities; ‘quasi-electrons’ (QE) carrying charge and spin, and associated with hybridized small-U and large-U orbitals; and ‘svivons’ carrying spin and lattice distortion. It is shown that this electronic structure leads to the systematic behavior of spectroscopic and transport properties of the cuprates. High-T_c pairing results from transitions between pair states of stripons and QEs through the exchange of svivons. The cuprates fall in the regime of crossover between BCS and preformed-pairs Bose-Einstein condensation behaviors.     

Photoproduction of large transverse momentum mesons and production of large-pT photons and leptons in proton-proton collisions

The photoproduction of large transverse momentum mesons is examined in a leading particle model using the techniques of the covariant parton model. In the leading particle model the large-p_T meson is produced in a high-energy, wide-angle scattering: γ + q → M + q. Numerical results such as inclusive cross sectioons, angular distributions and particle ratios are presented for the pseudoscalar mesons. The Landshoff-Polking-horne quark-fusion model is then applied to the production of large transverse momentum photons and leptons in proton-proton collisions. In the lepton case this model differs from the usual Drell-Yan mechanism in that the lepton pair has a small invariant mass but comes from a large-p_T virtual photon.     

The large-N deconfinement phase transition in a partially reduced Eguchi-Kawal model

We construct generalized twisted Eguchi-Kawai models which for large-N reduce space-time to a lattice of arbitrary size. Large-N lattice gauge theory at finite temperature is investigated in a model on a lattice with L₀ time slices and two lattice points in very time slice. We observe the large-N deconfinement phase transition in the weak coupling region. Assuming asymptotic scaling we find a transition temperature T_c = (101±4)Λ_L.     

Jets and quark confinement in the covariant parton model

A parton model incorporating quark confinement is discussed which (a) reproduces conventional parton model cross sections for deep inelastic lepton scattering and for large-p_T hadronic phenomena, (b) leads to final state jets and (c) accounts for the similar multiplicities observed in hadronic and lepton induced final states at low p_T.     

The transverse hadronic energy accompanying weak bosons

We study the hadronic transverse energy (E _T ) accompanyingZ ⁰ events in \(p\bar p\) interactions and compare our result with the observedE _T distribution in minimum bias events. We expect excess transverse energy to accompanyZ ⁰'s. This effect can also be probed experimentally using Drell-Yan lepton pairs and represents an interesting way to probe the multi-gluon structure of QCD.     

ϒ production at large transverse momentum as a probe of axigluons

Large-p_T production of J/Ψ and ϒ particles is suggested as a sensitive probe of axigluons of mass less than 40 GeV at the CERN collider and 80 GeV at the Tevatron. It is shown that existing CERN collider data on large-p_T ϒ production exclude axigluon masses less than around 20 GeV. At the projected SSC, ϒ and vector toponium production at large p_T through axigluon exchange by far outweighs the QCD contribution over a vast range of axigluon and toponium masses.     

Surface versus volume emissions in photon–hadron correlations

High-p _T photon–hadron correlations are studied within the next-to-leading order (NLO) perturbative QCD parton model with modified parton-jet fragmentation functions due to jet quenching in high-energy A+A collisions. In central A+A collisions, the away-side hadrons with large z _T=p _T ^h /p _T ^γ are controlled mainly by the surface emission of the gamma-jet events, while a small z _T region will be volume emission bias. In other words, gamma jets for a small-z _T region probe the dense matter deeper than those gamma jets for a large-z _T region, so the small-z _T gamma jets are found to be slightly more sensitive to the properties of the dense matter than the large-z _T gamma jets.     

Size-dependent threshold fields for Fröhlich conduction in niobium triselenide: Possible evidence for pinning by the crystal surface

The threshold field E_T for nonlinear “Fröhlich” conduction in niobium triselenide has been found to be correlated with the cross-sectional dimensions of the specimen. In 28 specimens from the same batch, E_T at 110 K was approximately proportional, over a range approaching 50 to 1, to the ratio C/A, where C is the circumference and A the area of the cross-section. No significant correlation was found between E_T and the resistance ratio R(293 K)/R(4.2 K), which was measured in 20 of the specimens and averaged 45. The diffraction evidence that the transverse phase coherence of the charge-density wave extends only over much smaller distances makes it unlikely that the cross-sectional dimensions influence E_T by limiting the Lee-Rice characteristic length for weak pinning by impurities. It is proposed that the pinning responsible for E_T is provided by the external surface of the crystal, supplemented in some cases by internal faults, rather than by impurities or other point defects within it.     

Quantum number effects in events with a charged particle of large transverse momentum: (I). Leading particles in single and diquark jets

In an experiment performed with the SFM facility at the CERN ISR, we have studied events with a large-p_T particle (π⁺, π^-, K^-, p) produced at polar angle settings of 20° and 45°. The longitudinal momentum distributions of leading fragments in the spectator jet of the same rapidity hemisphere as the trigger are strongly correlated to the nature of the trigger particle involved. These distributions are compared with predictions from dimensional counting rules, if parton scattering via vector gluon exchange is assumed for the large-p_T process. Given slight modifications of the original counting rules, we observe a fair agreement. As to the fastest particle (jet leader) in the “away” jet, its average charge is about $\text{1}\text{3}$ independent of the charge of the trigger; this value is expected for the case of three valence quarks participating in the hard scattering process. From the analysis of the trigger jet we find ?⁰/π⁺ and ?⁰/π^- production ratios near unity at a value of the transverse momentum of about 2 GeV/c.     

Large corrections to high-pT hadron-hadron scattering in QCD

We have computed the first non-trivial QCD corrections to the quark-quark scattering process which contributes to the production of hadrons at large p_T in hadron-hadron collisions. Using quark distribution functions defined in deep inelastic scattering and fragmentation functions defined in one particle inclusive e⁺e^? annihilation, we find that the corrections are large. This implies that QCD perturbation theory may not be reliable for large-p_T haron physics.     

Relation between elastic modulus and glass softening temperature in the delocalized atom model

The ratio of softening temperature (glass transition temperature) to elastic modulus (T _g /E) is mainly determined by the limiting elastic deformation of an interatomic bond, which characterizes the transition of a structural microregion from an elastic into a viscous-flow state. In silicate glasses, this transition is caused by the limiting deformation of directed ionic-covalent Si-O-Si bonds. In the case of amorphous hydrocarbons, it is related to the relatively weak intermolecular bonds between regions in chain macromolecules, and the T _g /E ratio is significantly higher than in inorganic glasses. In glassy systems of one class, this ratio turns out to be constant (T _g /E ?? const), and a linear correlation is detected between softening temperature and elastic modulus, which can be explained in terms of the delocalized atom model. The values of T _g /E can be used to classify glasses similarly to the well-known Angell classification according to so-called fragility.     

Off-shell effects in the three-nucleon bound state

Phase-shift-equivalent separable potentials are used to study the sensitivity of the triton binding energy E_T to the off-shell behavior of the two-nucleon T matrix. It is found that the deuteron wave function significantly constrains the theoretical uncertainty in E_T and that the properties of the off-shell T matrix at intermediate energies are only weakly reflected in E_T.     

The magnetized electron gas in terms of Hurwitz zeta functions

We obtain explicit expressions for thermodynamic quantities of a relativistic degenerate free electron gas in a magnetic field in terms of Hurwitz zeta functions. The formulation allows for systematic expansion in all regimes. Three energy scales appear naturally in the degenerate relativistic gas: the Fermi energy E_F, the temperature T and an energy related to the magnetic field or Landau level spacing, eB/E_F. We study the cold and warm scenarios, T⪡eB/E_F and eB/E_F⪡T, respectively. We reproduce the oscillations of the magnetization as a function of the field in the cold regime and the dilution of them in the warm regime.     

Deep inelastic Compton scattering and large-p T pion photoproduction in QCD hard collision model

Inclusive photon(pion) production at large-p _T in γp collisions is studied in the framework of QCD perturbation theory, taking into account the effects due to parton transverse momenta. The contributions from various components of photons are equally important at relatively smallp _T (e.g.,p _T?4 Ge V/c at \(\sqrt s = 17GeV\) ). At largep _T, however, the contributions from the subprocesses with direct photon coupling are most important; quark Compton scattering is the dominant subprocess in inelastic Compton scattering.     

On the large order expansion for the anharmonic oscillators

Using functional approaches, we investigate the large-K behaviour of theK ^th coefficientE _k in the perturbation expansion for the ground-state energyE(g) of the generalized anharmonic oscillatorX ^2N with internalO(_n)-symmetry. We establish the equivalence between the pure functional approach and the method of Collins-Soper at any order in 1 /K. For that purpose, we first develop an algebraic treatment of perturbation series and prove a theorem on Borelsummable functions. Finally, we compute analytically the 1 /K and 1 /K ² corrections to the leading term forN=2.     

Author index to volume 87B

We study large-p_T hadron production off nuclear targets in the framework of the QCD inspired parton model. The anomalous nuclear enhancement is interpreted as being due to multiple scattering of partons. The curious trigger dependence of the enhancement results mainly from a particularly intense multiple scattering of gluons. This is a novel and interesting observable manifestation of the existence of the gluon self-coupling.