16739726
Spacings of quarkonium levels with the same principal quantum number.
The spacings between bound-state levels of the Schr{umlt o}dinger equation with the same principal quantum number {ital N} but orbital angular momenta {ital l} differing by unity are found to be nearly equal for a wide range of power potentials {ital V}={lambda}{ital r}{sup {nu}}, with {ital E}{sub {ital Nl}}{approx_equal}{ital F}({nu},{ital N}){minus}{ital G}({nu},{ital N}){ital l}. Semiclassical approximations are in accord with this behavior. The result is applied to estimates of masses for quarkonium levels which have not yet been observed, including the 2{ital P} {ital c{bar c}} states and the 1{ital D} {ital b{bar b}} states. {copyright} {ital 1996 The American Physical Society.}
119346926
Improved constraints on states bound by a class of potentials
Recent work on states bound by a central potential whose Laplacian is positive is extended to cover a wider class of potentials for which energy level ordering theorems can be proved. This class includes power law potentials in particular. Constraints on the moments of the radial distance are improved and similarly for the kinetic energy. These constraints are shown to provide tight bounds on the energies of ground states for power law potentials, and on their variation with angular momentum. They are also used to bound the position of the maximum of the wavefunction for these states.
120439787
A fit of upsilon and charmonium spectra
We show that upsilon and charmonium spectra can be fitted by a common potential of the form A + Br α , with α close to 0.1. In particular the mass difference of ϒ″′ and ϒ is reproduced within 10 MeV. In this way it is confirmed that for the
 b b ¯ and cĉ systems the relevant part of the potential is flavour-independent and approximately though not exactly logarithmic. At the same time the claims, according to which the short-distance part of the potential could be shown to agree with the predictions of QCD by a comparison of charmonium and upsilon spectra, are put in serious doubt.
2463282
A Theorem on the real part of the high-energy scattering amplitude near the forward direction
Abstract We show that if for fixed negative (physical) square of the momentum transfer t , the differential cross-section dσ/dt tends to zero and if the total cross-section tends to infinity, when the energy goes to infinity, the real part of the even signature amplitude cannot have a constant sign near t = 0.
122648419
Some comparison theorems on moments in the ground state and in excited states of a two-body system
Abstract We prove and extend some conjectures by Dib, Franzini and Gilman on the comparison of expectation values of r v in the ground state and the first radial excited state of a two-body system for a given, non-zero angular momentum. One of the by-products is that for usual potentials, the overall splitting of the P states is likely to be smaller for the excited state than for the ground state. We also make comparisons between the ground state and angular excitations and prove that the expectation values of r v , −3⩽ v l .
118027493
Some aspects of quarkonium spectroscopy
10832623
Sparticle spectrum constraints.
The supersymmetric standard model with supergravity-inspired soft breaking terms predicts a rich spectrum of sparticles to be discovered at the SSC, LHC, and NLC. Because there are more supersymmetric particles than unknown parameters, one can write down sum rules relating their masses. We discuss the spectrum of sparticles from this point of view. Some of the sum rules do not depend on the input parameters and can be used to test the consistency of the model, while others are useful in determining the input parameters of the theory. If supersymmetry is discovered but the sum rules turn out to be violated, it will be evidence of new physics beyond the minimal supersymmetric standard model with universal soft supersymmetry-breaking terms.
29640694
Parton distributions at small x.
We perform a next-to-leading-order QCD analysis of the recent data for deep-inelastic lepton-nucleon scattering and related processes, in which we pay particular attention to the forms of the parton distributions at very small {ital x}. We discuss in detail, and we incorporate in the analysis, the theoretical QCD results leading to the singular {ital x}{sup {minus}1/2}-type behavior of the gluon and sea-quark distributions, as well as the modifications due to shadowing effects. We find the QCD shadowing corrections are significant for {ital x}{approx lt}10{sup {minus}3} even though the parton distributions are below their saturation limit. We give predictions for the structure functions {ital F}{sub 2} and {ital F}{sub {ital L}} accessible at the DESY {ital ep} collider HERA, and for {ital W} and {ital Z} production up to the energies of the CERN Large Hadron Collider and the Superconducting Super Collider. We discuss the possibility of experiments at these colliders probing the parton distributions in the very-small-{ital x} region.
36873731
Interference radiative phenomena in the production of heavy unstable particles.
We discuss the characteristic interference phenomena, including real as well as virtual radiative corrections, to the inclusive cross sections for production of heavy unstable systems such as {ital t{bar t}} or {ital W}{sup +}{ital W{minus}} pairs. We demonstrate explicitly the (fortunate) cancellation between emissions associated with the production of unstable particles and with their decays, and between emissions accompanying the decay stages. As a result the total interference effect is shown to be of {ital O}({alpha}{sub {ital i}}{Gamma}/{ital M}) or better (where {alpha}{sub {ital i}}={alpha} or {alpha}{sub {ital s}} as appropriate).
28650811
Crossing intrinsic depolarizing resonances by varying a partial Siberian snake.
We recently forced a 140 MeV polarized proton beam to cross intrinsic depolarizing resonances by varying a partial Siberian snake{close_quote}s strength for different values of the vertical and horizontal betatron tunes {nu}{sub {ital y}} and {nu}{sub {ital x}}. A weak second-order intrinsic resonance was observed in the {nu}{sub {ital x}} sweep; moreover, an unexpected partial spin flip was found in the {nu}{sub {ital y}} sweep. We also varied the snake ramp time to identify the {nu}{sub {ital y}} and {nu}{sub {ital x}} regions where the resonance crossings occurred during the snake variation; in these crossings the polarization partially deviated from Froissart-Stora behavior. {copyright} {ital 1996 The American Physical Society.}
23673028
New information on parton distributions.
New data on structure functions from deep-inelastic scattering provide new information on parton distributions, particularly in the 0.01[lt][ital x][lt]0.1 interval. This has important implications for predictions for the DESY [ital ep] collider HERA and for present and future high-energy hadron colliders. We present the results of updated fits to all available precision structure function and related data. We focus in particular on two issues: (a) the increase in the sea-quark distribution at small [ital x] implied by new [ital F][sub 2] data from the New Muon Collaboration, and its implications for other processes, and (b) the evidence for SU(2)-symmetry breaking in the light-quark sea. We show that although good fits can be obtained with or without this symmetry breaking, more physically reasonable parton distributions are obtained if we allow [ital [bar d]][gt][ital [bar u]] at small [ital x]. With the inclusion of the latest deep-inelastic data we find [alpha][sub [ital s]]([ital M][sub [ital Z]])=0.111[sub [minus]0.005][sup +0.004]. We also show how [ital W], [ital Z], and Drell-Yan production at [ital [bar p]p] colliders can give information on parton distributions.