Search

Following the improvements of compatibility of ICRF system with the tungsten (W) wall in ASDEX Upgrade (AUG) by using the boron-coated limiters on the 2-strap ICRF antennas and the 3-strap antennas with the W-limiters, the ICRF operating space was further extended in 3 areas: power, phase control between the antennas and frequency range. The available ICRF power in AUG was increased by using an additional RF generator to feed the central straps of the 3-strap antennas which require a 1.5:1 or 2:1 power ratio between the central strap and the two outer straps (combined) to minimize the ICRF-specific W sources. This increases the total experimentally achievable launched ICRF power in the optimized configuration to similar to 5.7 MW. A new phase control system enabled phase-locked operation of all 4 AUG ICRF antennas. This allows a better control of the launched k(parallel to) spectrum which on its turn is modified when both neighboring antennas are active, as well as of the structure of the global RF field distribution within the AUG vessel. Measurements by the RF magnetic field (B-dot) probes show that the RF field distribution can indeed be significantly affected by the variation of the phasing between the ICRF antenna pairs. However, its effect on the core plasma and on the residual ICRF specific plasma-wall interactions is small, for the cases so far limited to the H-modes at medium plasma densities. The available frequency range was extended and now covers four discrete frequencies (f): 30.0, 36.5, 41.8 and 55.1 MHz. In addition to the standard hydrogen (H) minority in deuterium (D) on-axis heating scheme at the magnetic field (B-t) of 2.0, 2.5, 2.8 and 3.1 T, the RF frequency range allows the use of the 3-ion D-(He-3)-H and He-4-(He-3)-H heating schemes at B-t=2.5-3.1 T (f=30 MHz - off-axis and on-axis), on-axis 3 omega(c) D heating at B-t=1.9 T (f=41.8 MHz) and at B-t=2.5 T (f=55.1 MHz) and 2 omega(c) H heating at B-t=1.9T (f=55.1 MHz).

Omega (ω) phase is formed in alpha (α) zirconium during dynamic loading and can be retained in the recovered material. The pathway for the α to ω change (or the reverse transformation) is not well understood. Zirconium was shock-loaded and the resulting two-phase microstructure was examined. Electron backscatter diffraction (EBSD) was used to characterize the orientation relationships and habit planes between phases to understand the pathways between α and ω phases and compare to Molecular Dynamics (MD) simulations. Based on key microstructural features, a significant amount of α phase appears to have originated from the reverse transformation from ω-Zr on unloading. Results of microstructural analysis will be discussed, along with implications toward phase transformation pathways.

Atomistic shock simulations are performed for single crystal titanium using four different interatomic potentials at impact velocities ranging from 0.5 km/s to 2.0 km/s. These potentials comprise of three parameterizations in the formulation of the embedded atom method and one formulation of the modified embedded atom method. The capability of the potentials to model the shock deformation and failure behavior is investigated by computing the shock hugoniot response of titanium and comparing to existing experimental data. In addition, the capability to reproduce the shock induced alpha (α) to omega (ω) phase transformation seen in Ti is investigated. The shock wave structure is discussed and the velocities for the elastic, plastic and the α-ω phase transformation waves are calculated for all the interatomic potentials considered.

In this talk we present an interpretation for the experimental data available on two different processes, namely, $J/\Psi \to \phi \pi^+ \pi^-$, $J/\Psi\to \gamma \omega \phi$, which seem to indicate existence of two new resonances with the same quantum numbers ($J^{\pi c}=0^{++}, I = 0$) and very similar mass (~1800 MeV) but with very different decay properties. However, our studies show that the peak structure found in the $\omega \phi$ invariant mass, in $J/\Psi \to \gamma \omega \phi$, is a manifestation of the well known $f_0(1710)$ while the cross section enhancement found in $J/\Psi \to \phi \pi^+ \pi^-$ is indeed a new $f_0$ resonance with mass near 1800 MeV. We present an explanation for the different decay properties of these two scalar resonances.

We investigate a direct transformation mechanism for the pressure driven α→ω martensitic transformation in pure Zr as described by Silcock [2]. A systematic study of coupled atomic shuffles and strains evaluates α→ω transformation energy-landscape. The calculated change in enthalpy along this transformation path as a function of pressure shows decrease in enthalpy barrier with increase of pressure. We find the ab-initio nudged elastic band barriers at 0 K for this pathway is 68 meV/atom.

We are studying material strength at high pressures (>1 Mbar) and high strain rates (106 - 108 sec-1) in Ta using the Omega laser. The Ta sample is maintained well below the melt temperature using a quasi-isentropic ramped drive based on a reservoir-gap-sample configuration. The strength is inferred from measurements of the growth of pre-imposed sinusoidal ripples on the sample via the Rayleigh-Taylor (RT) instability. The material strength can greatly suppress RT growth rate via an effective lattice viscosity (H. S. Park, et al., Phys. Rev. Lett. 104, 135504 (2010)). Our recent experiments measure the Ta RT growth in face-on radiography configuration. We find that the recently developed multi-scale dynamic material strength model matches our measured Ta RT strength data well, whereas the other constituent strength models disagree with our experimental observations.

Near threshold omega meson photoproduction is studied with the CBELSA/TAPS experiment at the ELSA accelerator of Bonn University. Single as well as double polarization observables are measured using either linear or circular polarized photon beams and a longitudinal polarized proton target., Proceeding for NSTAR 2011 conference

We present theoretical and computational analysis of the deformation regimes accessed by recent Rayleigh-Taylor (RT) material strength experiments in vanadium (V) and tantalum (Ta) done at the Omega laser at high pressures (>1 Mbar) and high strain rates (106 - 108 sec-1). Within the context of the LLNL multiscale models, the V-RT experiment appears to be dominated by deformation in the drag regime, whereas the Ta-RT experiment resides largely within the thermal activation regime.

We study whether the nonmonotonic behavior found in the differential cross section of the phi-meson photoproduction near threshold can be described by a resonance. The resonant contribution is evaluated by using an effective Lagrangian approach. We find that, with the assumption of a J^P=3/2^- resonance with mass of 2.10 \pm 0.03 GeV and width of 0.465 \pm 0.141 GeV, LEPS data can indeed be well described. The ratio of the helicity amplitudes A_1/2/A_3/2 calculated from the resulting coupling constants differs in sign from that of the known D13(2080). We further find that the addition of this postulated resonance can substantially improve the agreement between the existing theoretical predictions and the recent omega photoproduction data if a large value of the OZI evading parameter x_OZI = 12 is assumed for the resonance., Contribution to the Proceedings of BARYONS'10 - International conference on the structure of baryons, Dec. 7-11, 2010, Osaka, Japan

We study the mesons matter D-\bar{D} in the framework of sigma and omega meson exchange model using Walecka's mean field theory. We choose the equal number of D and anti-D meson then we get =0 and the field sigma exhibits a critical temperature around 1.2 GeV. We investigate effective mass, pressure, energy density and energy per pair. We conclude that this matter is a gas and these results are not favorable for the existence of D-\bar{D} bound state. Note: in arXiv:1211.5505 this interpretation has been updated where these results are favorable for the existence of $D-\bar{D}$ bound state.

We have investigated the in-medium modifications of ω mesons in photoproduction experiments using the Crystal Barrel(CB)/TAPS detector system at the ELSA accelerator facility in Bonn. The ω-mesons were reconstructed using the ω→π0γ channel. In a first analysis of the data set on a Nb target, published by Trnka et al. [Phys. Rev. Lett. 94(2005) 192303], evidence for an in-medium mass shift of the ω-meson was deduced from the observed ω line shape. The extracted signal shape was, however, found to be sensitive to the background subtraction. For this reason a re-analysis of the same data set was initiated with the goal to reduce the background and to deduce the shape and the absolute magnitude of the background directly from the data. Here we present recent results from this re-analysis. The omega signal resulting after background subtraction has been compared to different scenarios of GiBUU transport model calculations for the full incident photon energy range (900–2200 MeV) and near the production threshol...

We compute the radiative corrections, to first order in the fine structure constant {alpha}, to the asymmetry parameter {alpha}{sub {Omega}}of the {Omega}{sup -{yields}{Lambda}}+K{sup -} decay. We use previous results where Sirlin's procedure is used to separate the radiative corrections into two parts, one independent model contribution and a model dependent one.

The recent measurement of the {omega}{sub b}{sup -} mass, 6054.4{+-}6.8(stat.){+-}0.9(syst.) MeV/c{sup 2} is in remarkable agreement with the prediction of a simple constituent quark model with baryon-meson supersymmetry, M({omega}{sub b}) = 6052.1{+-}5.6MeV. Results from the Tevatron for the masses of {sigma}{sub b}{sup {+-}}(uub and d db) and {xi}{sub b}{sup -}(dsb) baryons are also within 2 MeV of our theoretical predictions. These combined with other relations between masses and baryons of all flavors provides a strong challenge to QCD which does not simply relate meson and baryon masses.

We discuss the physics of B0s mesons focusing on CP violation in B0s -> J/Psi Phi decays at the Tevatron. We summarize measurements of the properties of bottom baryons at the Tevatron including the Sigma_b states and the Xi_b baryon. We also discuss the discovery of the Omega_b baryon.

Two of the former HEGRA atmospheric Cherenkov telescopes are being refurbished at the Universidad Nacional Autonoma de Mexico (UNAM) with the purpose of being installed as the Observatorio MExicano de GAmmas (OMEGA, Mexican Observatory of Gammas). Mexico has developed infrastructure around two astrophysical facilities with excellent atmospheric conditions, San Pedro Martir at 2800 m a. s. 1. and Sierra Negra at 4600 m a.s. 1. The Sierra Negra site has been chosen over San Pedro Martir to host OMEGA in order to test the performance, sensitivity and energy threshold of atmospheric Cherenkov telescopes at high altitude. OMEGA will also be located adjacent to the HAWC TeV gamma‐ray observatory in order to cross calibrate HAWC events and to follow up HAWC candidate sources. The primary scientific objective of OMEGA is to monitor TeV blazars, and OMEGA will work in synergy with the Sierra Negra consortium of observatories to perform broad band multi‐wavelength observations. We will present the OMEGA project in detail and its status.

We revisit the composition of neutral hydrogen, i.e. atomic (HI) and molecular (H2), in the local Universe, with focus on the H2-to-HI mass ratio R in various galaxies and the H2-mass function (MF). First, we derive the H2-MF from the CO-luminosity function (LF) of the FCRAO Extragalactic CO Survey, using a variable CO-to-H2 conversion fitted to nearby observations. This implies a universal H2 density Omega(H2)=(6.9±2.7)*10^-5/h and Omega(H2)/Omega(HI)=0.26±0.11, which could, however, suffer from incompleteness of the CO-sample. Therefore, a second approach derives the H2-MF from a HI-sample with well described completeness (HIPASS). This premisses an estimation of R, for which we introduce a set of phenomenological models based on a sample of 245 galaxies drawn from the literature. Our best model in terms of statistical scatter describes R as a function of galaxy type and cold gas mass. This model leads to an H2-MF that matches the one derived from the CO-LF, thus supporting that model and settling completeness uncertainties.

An ω‐inconsistent theory of the cumulative hierarchy of ZFC is presented, using an expanded language that includes a truth‐predicate, with formulas of the language of ZF being represented by urelements. This ω‐inconsistency makes it possible to distinguish, within the cumulative hierarchy itself, between sets and proper classes, taking the latter to be collections so large that they lead to ω‐inconsistency.

In last 10 years, $0^{++}$ resonances have been observed and studied at BES in many processes, such as $J/\psi\to\gamma\pi^+\pi^-\pi^+\pi^-$, $\gamma\pi^+\pi^-$, $\gamma\pi^0\pi^0$, $\gamma K^+K^-$, $\gamma K_SK_S$, $\gamma\omega\phi$, $\omega\pi^+\pi^-$, $\omega K^+K^-$, $\phi\pi^+\pi^-$, $\phi K^+K^-$, $\psi(2S)\to J/\psi\pi^+\pi^-$, $\chi_{c0}\to\pi^+\pi^-K^+K^-$, $\pi^+\pi^-\pi^+\pi^-$ etc.. The results on $0^{++}$ resonances observed at BES are reviewed.

It is known that the cosmological baryon density ($\Omega_{\rm{b}}$) and dark matter density ($\Omega_{\rm{dm}}$) have strikingly similar values. However, in most theories of the early Universe, each density is explained by separate dynamics and consequently there is no compelling reason for this observation. In this note, I briefly review a model in which the dark matter species possesses a particle-antiparticle asymmetry. This asymmetry determines both the baryon asymmetry and strongly affects the dark matter density, thus naturally linking $\Omega_{\rm{b}}$ and $\Omega_{\rm{dm}}$. In these models it is shown that sneutrinos can play the role of such dark matter.

The authors present a precision measurement of the mass of the {Lambda}{sub c}{sup +} and studies of the production and decay of the {Omega}{sub c}{sup 0} and {Xi}{sub c}{sup 0} charm baryons using data collected by the BABAR experiment. To keep the systematic uncertainty as low as possible, the {Lambda}{sub c}{sup +} mass measurement is performed using the low Q-value decays, {Lambda}{sub c}{sup +} {yields} {Lambda}{sup 0} K{sub S}{sup 0}K{sup +} and {Lambda}{sub c}{sup +} {yields} {Sigma}{sup 0} K{sub S}{sup 0}K{sup +}. Several hadronic final states involving an {Omega}{sup -} and a {Xi}{sup -} hyperon are analyzed to reconstruct the {Xi}{sub c}{sup 0} and the {Omega}{sub c}{sup 0}.

The invariant mass spectra of e+e− pairs produced in 12 GeV p+A reactions are measured at the KEK‐PS. We observed a significant enhancement over the known hadronic sources on the low‐mass side of the ω meson peak. The 95 % C.L. allowed parameter regions for ρ/ω ratio are obtained as ρ/ω < 0.15 and ρ/ω < 0.31 for C and Cu targets, respectively. As for the φ meson, the data obtained with a Cu target revealed a significant excess on the low‐mass side of the φ meson peak mainly in the βγφ < 1.25 region.

A review of the most recent BABAR results on electroweak penguin B decays is presented. The focus of this paper is on the measurement of observables in the decays B {yields} X{sub s}{gamma}, B {yields} K{sup (*)}l{sup +}l{sup -} B {yields} K{sub s}{sup 0}{pi}{sup 0}{gamma} (time-dependent analysis) and B {yields} ({rho}/{omega}){gamma}.

We investigate the feasibility that, in the field of a superstrong standing laser wave, high-order harmonics of the pumping laser are generated from vacuum. Analytical calculations employing adiabatic perturbation theory show that, for laser electric fields larger than ${E}_{\mathrm{cr}}={m}^{2}{c}^{3}/\ensuremath{\hbar}e=1.3\ifmmode\times\else\texttimes\fi{}{10}^{16}\text{ }\mathrm{V}/\mathrm{cm}$, high-order harmonics are generated. The harmonic spectrum shows a wide plateau followed by a cutoff. The cutoff starts approximately at photon energies $\ensuremath{\hbar}{\ensuremath{\omega}}_{M}\ensuremath{\sim}\sqrt{\ensuremath{\hbar}ec{E}_{L}}$, with ${E}_{L}$ being the amplitude of the laser field. In the opposite limit ${E}_{L}\ensuremath{\ll}{E}_{\mathrm{cr}}$, the emission of high harmonics is very unlikely. In this case, a feasibility analysis for the experimental observation of the photon-photon scattering process using x-ray free electron lasers shows that the requirements are much less restrictive than those required to observe electron-positron pair creation.

The HyperCP (E871) experiment collected ∼ 1010 hyperon decays, including ∼ 107 Omega decays. A signal of 134 events has been observed in the rare decay mode Ω− → Ⅺ−π+π−. We present preliminary results on the contribution of Ω− → Ⅺ1530*0 π− to this process.

The internal conversion and electron-positron pair creation processes provide a versatile tool for investigating various aspects of the nuclear structure. The most recent calculations of Internal Conversion Coefficients, based on relativistic self-consistent Dirac-Fock calculations are widely regarded as the most accurate numerical results available today. The International Nuclear Structure and Decay Data Network has adopted the new conversion coefficients to replace the Hager and Seltzer, Roessel et al., and Band and Trzhaskovskaya tables.In this paper we report on the development of a new conversion electron data base and associated programs, which includes the new internal conversion coefficients tables, published in At. Data and Nucl. Data Tables 81, (2002) 1. Additional calculations have been carried out to extend the energy range, as well as improve the interpolation accuracy to obtain conversion coefficients in the 1-keV to 6000-keV region. Additional data tables have been compiled from published data to obtain values of electron-positron pair conversion coefficients and {omega}(E0) electronic factors.

We present first results from contemporaneous observations of Cygnus X-1 with INTEGRAL and RXTE, made during INTEGRAL's performance verification phase in 2002 November and December. Consistent with earlier results, the 3-250 keV data are well described by Comptonization spectra from a Compton corona with a temperature of kT~50-90 keV and an optical depth of tau~1.0-1.3 plus reflection from a cold or mildly ionized slab with a covering factor of Omega/2pi~0.2-0.3. A soft excess below 10 keV, interpreted as emission from the accretion disk, is seen to decrease during the 1.5 months spanned by our observations. Our results indicate a remarkable consistency among the independently calibrated detectors, with the remaining issues being mainly related to the flux calibration of INTEGRAL., Comment: 6 pages, 3 figures. Figs. 2 and 3 are best viewed in color. Accepted for publication in the INTEGRAL special edition of A&AL

Within the one meson exchange and Regge models we study ω‐meson photoproduction at energies above the s channel resonance region. Here the vector meson photoproduction is dominated by exchanges in the t channel and free parameters of the meson exchange contribution can be fixed explicitly by available data. Thus, at the resonance region the t channel background might be separated from the contribution which might come from baryonic resonances coupled to ω‐meson. Furthermore, we investigate different model prescriptions for the ωNN vertex function by imposing gauge invariance as well as crossing symmetry. We show high precision measurements at small |u| provide an access to ωNN vertex. Our predictions are in reasonable agreement with the results from CLAS Collaboration obtained recently at Jefferson Laboratory.

A large acceptance surface muon channel “Dai Omega” was successfully constructed at KEK‐MSL. At Dai Omega, four large aperture superconducting coils were utilized for the muon collection with solid angle acceptance of 1sr. As a result, the muon intensity of 4×105μ+/sec has been realized at KEK‐NML (500MeV, 5μA). A μSR detection system was developed, and the event rate of 36M/hour was achieved. As for the particle separation, axially symmetric electric separator was installed at the inside of 4th coil.

The 2dF Galaxy Redshift Survey is the first to observe more than 100,000 redshifts, making possible precise measurements of many aspects of galaxy clustering. The spatial distribution of galaxies can be studied as a function of galaxy spectral type, and also of broad-band colour. Redshift-space distortions are detected with a high degree of significance, confirming the detailed Kaiser distortion from large-scale infall velocities, and measuring the distortion parameter beta = Omega_m^{0.6}/b = 0.49 +- 0.09. The power spectrum is measured to 0.02 h Mpc^{-1}, and is well fitted by a CDM model with Omega_m h =0.18 +- 0.02 and a baryon fraction of 0.17 +- 0.06. A joint analysis with CMB data requires Omega_m = 0.31 +- 0.05 and h = 0.67 +- 0.04, assuming scalar fluctuations. The fluctuation amplitude from the CMB is sigma_8 = 0.76 +- 0.04, assuming reionization at z < approx 10, so that the general level of galaxy clustering is approximately unbiased, in agreement with an internal bispectrum analysis. Luminosity dependence of clustering is however detected at high significance, and is well described by a relative bias of b/b^* = 0.85 + 0.15(L/L^*). This is consistent with the observation that L^* in rich clusters is brighter than the global value by 0.28 +- 0.08 mag., 16 pages. To appear in the proceedings of the 13th Annual October Astrophysics Conference in Maryland: The Emergence of Cosmic Structure, eds. S. Holt and C. Reynolds (AIP)

We present the construction of free energy functions for the α and ω phases of Ti. These free energies combine information from ambient pressure, static high pressure, and shock wave measurements as well as first principles total energy calculations. The Hugoniot data are analyzed in terms of this equation of state. The Hugoniot consists of three segments: a metastable α‐phase region, a transition region, and an ω‐phase branch. The extent of the metastability and time resolved wave profiles are discussed in terms of a model in which the transformation rate depends exponentially on the pressure, an assumption which is motivated by static high‐pressure data. This picture is consistent with the observed wave shapes and with the observation that the apparent transformation pressure is dependent on the peak shock pressure.

The role of the nucleon resonances ($N^*$) in $\omega$ photoproduction is investigated by using the resonance parameters predicted by Capstick and Roberts. The contributions from the nucleon resonances are found to be significant in various spin asymmetries. In particular, we found that a crucial test of our predictions can be made by measuring the parity asymmetry and beam-target double asymmetry at forward scattering angles., Comment: 5 pages, aipproc.sty, 3 figs (4 eps files), talk at the 14th International Spin Physics Symposium (SPIN 2000), Osaka, Japan, October, 2000

We report on a target of opportunity program to study GRB afterglows based on observations with the Calar Alto 3.5-m telescope equipped with the near-infrared camera Omega Cass.

Electroproduction of ω(783) mesons from a proton target has been measured at CLAS in a search for so called “missing” baryon resonances. Scattered electrons were measured in coincidence with the recoiling proton and a π+ from the ω decay. Missing mass techniques were applied to identify the outgoing ω and to reduce the contributions of ρ(770) and 2 π final states. The resulting ep missing mass distributions clearly show an ω peak superimposed on a predominantly 3-pion phase space. Preliminary analysis indicates that t distributions monotonically decrease for W>2 GeV, as expected from pi-exchange and diffractive processes but for 1.8 GeV

A finite energy sum rule (FESR) analysis of the isospin-breaking vector current correlator is used to determine the isospin-breaking electromagnetic (EM) decay constants of the low-lying vector mesons. These results are used to evaluate the corrections required to extract the flavor diagonal 33 and 88 resonance contributions from the full resonance EM contributions to the EM spectral function. A large (~15%) correction is found in the case of the omega contribution to the isoscalar spectral function. The implications of these results for sum rules based on the isovector-isoscalar spectral difference are considered., Comment: Presentation to the 3rd International Conference on Symmetries in Subatomic Physics, Adelaide, Mar. 13-17, 2000

Two examples of ``exotic'' phenomena which become possible and important in the presence of nuclear matter are discussed: omega -> pi pi decay, and rho-omega mixing. Significance of these processes for the low-mass dilepton production in relativistic heavy-ion collisions is indicated., 8 pages, uses aipproc.cls, talk presented by W. Florkowski at the International Workshop on Hadron Physics "Effective Theories of Low Energy QCD", Coimbra, Portugal, September 10-15, 1999

We present results concerning the angular resolution of the LISA detector for monochromatic sources, such as white-dwarf binaries. We compare with the angular resolution achievable by OMEGA.

It is known that in e+e− annihilation the energy region near 1.6 GeV contains at least two isovector JPC=1−− ρ′ states and very similar situation is for isoscalar ω′ mesons [1]. Another possible ρ′ state with mass in the range 1.1–1.3 GeV having a long history, not a long ago has been seen in the process K−p→π+π−Λ [2]. We discuss the properties of these states using different methods keeping unitarity.

We make a re-analysis of I=0 \pi\pi scattering phase shift \delta_0^0 through a new method of S-matrix parametrization (IA; interfering amplitude method), and show a result suggesting strongly for the existence of \sigma-particle -- long-sought Chiral partner of \pi-meson. Furthermore, through the phenomenological analyses of typical production processes of the 2\pi-system, the pp-central collision and the J/\Psi \to \omega\pi\pi decay, by applying an intuitive formula as sum of Breit-Wigner amplitudes, (VMW; variant mass and width method), the other evidences for the \sigma-existence are given. The validity of the methods used in the above analyses is investigated, using a simple field theoretical model, from the general viewpoint of unitarity and the applicability of final state interaction(FSI-) theorem, especially in relation to the ``universality'' argument. It is shown that the IA and VMW are obtained as the physical state representations of scattering and production amplitudes, respectively. The VMW is shown to be an effective method to obtain the resonance properties from production processes, which generally have the unknown strong-phases. The conventional analyses based on the ``universality'' seem to be powerless for this purpose., Comment: Plenary talk at HADRON'97, the 7th int. conf. on hadron spectroscopy, BNL, August 1997. 10 pages with 2 eps figures

The magnetic response of the charged anyon fluid at temperatures lower and larger than the fermion enery gap $\omega_{c}$ is investigated in the self-consistent field approximation. We prove that the anyon system with boundaries exhibits a total Meissner effect at temperatures smaller than the fermion energy gap ($T\ll \omega_{c}$). The London penetration length at $T$ $\sim 200K$ is of the order $\lambda \sim 10^{-5}cm$. At $T\gg \omega_{c}$ a new phase, characterized by an inhomogeneous magnetic penetration, is found. We conclude that the energy gap, $\omega_{c},$ defines a scale that separates two phases: a superconducting phase at $T\ll \omega_{c}$, and a non-superconducting one at $T\gg \omega_{c}$., Comment: 7 pages, Talk presented at SILAFAE'98. April 8-11, 1998, San Juan, Puerto Rico

Experimental evidence indicates that the dynamics of channeled propagation arising from a relativistic/charge-displacement mechanism can produce exceptionally high intensities (>10{sup 20} W/cm{sup 2}) and power densities (>10{sup 19} W/cm{sup 3}) under spatially well-controlled conditions in the interior of the channel. This process opens up a new domain of high intensity interactions in which controllable field strengths in the 10-50(e/a{sub 0}{sup 2}) range can be applied to materials. Furthermore, these field strengths can be developed on very fast rise times ({approx}1-3 fs), since the dynamical response of the channel formation can be on the order of the plasma time {approx}2{pi}/{omega}{sub p}. Under these conditions, matter is expected to respond in a highly complex and nonlinear way. Of particular significance are (1) the detailed dynamics of the channeling mechanism, including the wavelength scaling, and (2) the development of advanced analytical tools to represent the interactions theoretically.

We present a study on hyperon/anti-hyperon production asymmetries in the framework of the recombination model. The production asymmetries for Lambda 0/Lambda 0-bar, Xi-/Xi+ and Omega-/Omega+ are studied as a function of x_F. Predictions of the model are compared to preliminary data on hyperon/anti-hyperon production asymmetries in 500 GeV/c pi- p interactions from the Fermilab E791 experiment. The model predicts a growing asymmetry with the number of valence quarks shared by the target and the produced hyperons in the x_F < 0 region. In the positive x_F region, the model predicts constant asymmetries for Lambda 0/Lambda 0-bar and Omega-/Omega+ production and a growing asymmetry with x_F for Xi-/Xi+. We found a qualitatively good agreement between the model predictions and data, showing that recombination is a competitive mechanism in the hadronization process.

Within the US ICF program the direct‐drive method has been chosen using the OMEGA facility based on the Neodymium glass laser. Requirements for the future experiments are reviewed and the design is outlined.

In this paper we consider a formalism for multi-dimensional simple MHD waves using ideas developed by Boillat. For simple wave solutions one assumes that all the physical variables (the density rho, gas pressure p, fluid velocity V, gas entropy S, and magnetic induction B in the MHD case) depend on a single phase function phi(r,t). The simple wave solution ansatz and the MHD equations then require that the phase function has the form phi = r x n(phi) - lambda(phi)t, where = n(phi) = Delta phi / (absolute value of Delta phi) is the wave normal and lambda(phi) = omega/k = -phi t / (absolute value of Delta phi) is the normal speed of the wave front. The formalism allows for more general simple waves than that usually dealt with in which n(phi) is a constant unit vector that does not vary along the wave front. The formalism has implications for shock formation for multi-dimensional waves.

Strange and multistrange baryon and antibaryon production has been studied in sulphur sulphur interactions at 200 GeV/c per nucleon at central rapidity. Particle production ratios and transverse mass spectra are presented for Λ, Ξ−, Ξ and Ξ−. In addition preliminary results on charged kaon production are presented, and the status of identified charged particle track reconstruction using the Omega RICH is reviewed.

Following the work of Chen and Dawson on Ion‐Channel Laser (ICL), we study the amplification mechanism of the ICL by using the one‐particle model proposed by them, and methods of secular perturbation theory. We calculate the conditions for resonance in the wave‐particle interaction, and estimate the gain expected. The resonant Electro‐Magnetic wave frequency appears to depend strongly on the amplitude of oscillations of the beam particles. This may significantly reduce the amplification, and limit the use of ICL to relatively low frequencies, up to Infra‐Red, where high output power (∼GW) is achievable. Analytical results are confirmed by numerical simulations.