B. Margolis

Forward scattering amplitudes in semi-hard QCD☆

Abstract We argue that the observation by UA4 of a high energy ρ value (real-to-imaginary ratio of the forward p p amplitude) in excess of what had been predicted is accommodated by QCD. At s ≅0.1−1 TeV , typical hadron collisions become semi-hard and therefore calculable in perturbative QCD. An “effective” threshold develops in this energy region as a result of the “exploding” gluon content of the proton. We associate the increase with energy of the total cross section with this threshold and show that it will also result in a rapid increase of ρ over and above what is expected from models which do not take into account this qualitative change in the structure of hadrons. The first signature of this “threshold” has arguably been seen by UA1 through the discovery of the minijet phenomena. We predict substantially higher cross section and ρ values at the Tevatron collider and the SSC.

Elastic scattering at √s = 1800 GeV. The first look at the asymptotic nucleon

Abstract At the Tevatron Collider, the E-710 Collaboration has measured the slope of the elastic scattering cross section up to |t| = 0.65 ( GeV c ) 2 , at √ s = 1800 GeV. The data clearly show a transition from the region in which the shape of the scattering is dominated by the hadronic matter form factor of the nucleon to the region in which the nucleon develops a sharp edge, i.e., a disk-like behavior. This transition is interpreted as the onset of asymptopia.

Can perturbative QCD predict a substantial part of diffractive LHC/SSC physics?

Abstract We examine a model of hadronic diffractive scattering which interpolates between perturbative QCD and non-perturbative fits. We restrict the perturbative QCD resummation to the large transverse momentum region, and use a simple Regge-pole parametrization in the infrared region. This picture allows us to account for existing data, and to estimate the size of the perturbative contribution to future diffractive measurements. At LHC and SSC energies, we find that a cut-off BFKL equation can lead to a measurable perturbative component in traditionally soft processes. In particular, we show that the total pp cross section could become as large as 228 mb (160 mb) and the ϱ parameter as large as 0.23 (0.24) at the SSC (LHC).

Search for “color thaw”: Radiative decays of B and D mesons

Abstract Photon emission from the annihilation contribution to B and D decays is shown to have a very characteristic spectrum. It overcomes helicity suppression, but is severely color suppressed. It is argued that an extra gluon overcomes some of that suppression (“color thaw”) and renders B0→γ+X and D0→γ+X via annihilation measurable. These decays will then serve as a testing ground for the previously suggested concept of thawing of color and other quantum numbers, with B being much more reliable than D decays.

In search of the ηc

Abstract We argue that the X(2.88) detected in π − p → γγ + n at 40 GeV/ c cannot be the η c . We discuss the possibility that a qqcc state is produced there, probably the same state discovered in radiative decay of the J/ψ. Only at much higher energies is the η c expected to dominate over qqcc in the π − p interaction. We also discuss coherent photoproduction and find that four quark state production would dominate over η c .

The gluon structure of high energy hadrons and their interactions

Abstract We argue that the production of gluon jets, a rare occurrence at low energy, becomes a feature of average hadron collisions at very high energies, √s > 1 TeV. This inspires a model where hadron interactions are mediated by semi-hard gluons rather than valence quarks. We calculate forward scattering as the shadow of the large inelastic cross sections associated with gluon jets. In this type of model the total cross section and event structure at future hadron colliders could be very different from what is routinely anticipated.

On hadronic production of the ηc and other cc̄ bound states

Abstract We discuss various mechanisms for inclusive production of cc bound states in hadron-hadron interactions. We conclude that for η c , η′ c alone, among the bound states, the cross section for production is mainly due to the annihilation of two constituent gluons in a color singlet state. We give detailed results for η c production cross sections.

Four quark states and open charm production

Abstract We discuss and calculate the contribution of resonances to open charm production through two-gluon annihilation in nucleon—nucleon interaction. Four-quark resonances, if they exist, make an important contribution because of their strong coupling to two gluons.

REGGE CUTS, MULTIPLE SCATTERING, AND THE POMERON SLOPE.

Abstract We analyze the Dubna-Serpukhov small momentum transfer data on p-p elastic scattering in terms of the moving pomeron plus cuts model of Frautschi et al. We find evidence for a pomeron slope α p ′ ≈ 1 (GeV/ c ) −2 .

LIMITS ON SYMMETRY-BREAKING ELECTROMAGNETIC INTERACTIONS OF THE ELECTRON AND PROTON.

SummaryThe experimental limits on the parity-violating polarization in electron-proton scattering are used to obtain limits onC- andP-violating electromagnetic interactions of the electron and proton. The effect of an electric-dipole moment of the proton on electron-proton scattering is discussed, and the cross-section is given including all proton spins.RiassuntoSi usano i limiti sperimentali della polarizzazione che viola la parità nello scattering elettrone-protone per ottenere limiti alle interazioni elettromagnetiche dell’elettrone e del protone che violanoC eP. Si discute l’effetto di un momento di dipolo elettrico del protone sullo scattering elettrone-protone e si dà la sezione d’urto tenendo conto di tutti gli spin del protone.РезюмеЭкспериментальные пределы на нарушающую четность поляри-зацию при электрон-протонном рассеянии используются для получения пределов на нарушающиеC иP электромагнитные взаимодействия электрона и протона. Обсуз-дается влияние электрического дипольного момента протона на электрон-протонное рассеяние, и приводится поперечное сечение, включая все протонные спины.