Λ-Hypernucleus formation in proton-nucleus reactions

We study the production of hyperons inp + A reactions within the BUU transport approach including elastic N rescattering and extract the sticking probabilities and hypernucleus formation cross sections as a function of bombarding energy and target mass. At 1.5 GeV about 25% of the hyperons are found to be bound in case of heavy nuclei like²³⁸U leading to large cross sections for-hypernuclei. The respective hypernuclei show broad distributions in excitation energy, momentum and angular momentum. The decay of the hyperon in case of heavy targets is found to be almost entirely due to nonmesonic decay channels, i.e.N NN processes.Supported by BMFT, GSI, Forschungszentrum Jülich and the Polish Committee for Scientific Research under Grant no. PB2593/2/91     

Contributions toΛ c + →πΣ,πΛ andp\bar K^0 from excited states

We consider contributions to _c ⁺ , and from excited states. The calculations are performed within the MIT-bag model and a heavy quark bag model. Because the mass of _c ⁺ is rather big compared to the strange baryons, excited baryon states with mass close to that of _c ⁺ in some cases give significant pole contributions to the decay amplitudes of _c ⁺ .     

On the asymptotics of nodes ofL 2-solutions of Schrödinger equations in dimensions ≧ 3

Let _R = ⁿ B _R, wheren3 andB _R={x ⁿ :|x|R}. We investigate the asymptotics of real valued solutions L ²( _R ) of the Schrödinger equation (–+V–E)=0, whereE<0>V(x)0 for |x|: LetD denote an unbounded nodal domain of (i.e. a component of _R {x:(x)=0}), and letS(r)={yS ^n–1:ryD} withS ^n–1 the unit sphere in ⁿ . Under suitable assumptions onV it is shown that for some >0,

O $$(\bar \Lambda /m_c )$$ effects in tests of factorization hypothesis for heavy-hadron nonleptonic decays

In the framework of the heavy-quark effective theory, theO ( O(_QCD)) corrections are estimated in the test of factorization hypothesis forB-meson nonleptonic decays proposed by Bjorken. Similar calculations are also carried out for _b nonleptonic decays. The effects of these corrections on the estimate of theD _s -meson decay constant are discussed.     

Heavy-quark bound states in potentials with the Bethe-Salpeter equation

The spinless Bethe—Salpeter equation is solved for three attractive static quark-antiquark potentials of the form V(r)=–ar^–+br+c, 01, and the effective non-Coulombic power-law potential of the formV(r)=ar ^0.1+c to obtain the spin-averaged energy levels in bottomonium (b ) and charmonium (c ) families. The shifted 1/N expansion technique is used. Calculations of the energy eigenvalues are carried out up to third order and parameters of each potential are adjusted to obtain the best agreement with the experimental spin-averaged data (SAD). Flavor-dependent and flavor-independent cases are considered in this work.     

K s →π+π−γ: a laboratory for meson dynamics

We discuss the decayK _{s +–} in the framework of chiral perturbation theory. The direct emission in this decay can be an useful test of meson dynamics.     

Partition temperatures ofK 0 andΛ 0 fromπ + p collisions

The rapidity distributions of inclusive ⁺ p ^–,K ⁰, ⁰ andK ^* (892) atP _1ab=16 GeV/c of CERN experiments, are analyzed using the covariant partition temperatureT _p model. In the fireball system, apart fromK ^* (892),T _p ^* m, no indication of thermal equilibrium, the average momentum ofK ⁰ and ⁰ being approximately equal and in the opposite direction, the entropy density is practically the same forK ⁰ and ⁰ but less than that of ^–. It is found that the principle of equipartition holds rather for the momenta of ,K, and in the fireball system.     

Is the channelH \to b\bar b observable at LHC?

A detailed study of associated Standard Model Higgs production (WH and ) at the LHC (or a possible upgraded Tevatron collider), where the Higgs boson decays to pairs, is reported for 80m _H <120 gev.=" even=" for=">b-tagging performances of the detector, the signal cannot be cleanly extracted from the background. For an integrated luminosity of 10⁴ pb ^–1 andm _H =100 GeV, one can expect at best 110 reconstructed decays fromWH production, above a resonant background of 150WZ events and a non-resonant background of 4800 events, and 100 reconstructed pairs (of which 50 from decay) from production, above a background of 4000 events. The main difficulty in extracting these two channels is in the expected low signal rate after reconstruction, the need for accurate control of all the background sources and for extremely goodb-tagging performance. Nevertheless, for a few years of running at a luminosity of 10³³ cm^–2s^–1, channel may be the best way to probe the region 80m _H <100>     

Triple Regge analysis of inclusiveΛ production inK + p and π+ p interactions at 250 GeV/c

A triple Regge analysis is performedof inclusive production in the proton fragmentation region ofK ⁺+X and ⁺+X at 250 GeV/c. Slope and intercept of the leading strange meson trajectory are determined. The results obtained here are compared with those of other experiments.Partially supported by grants from CPBP 01.06 and 01.09.     

Meyer's concept of quasicrystal and quasiregular sets

This paper relates two mathematical concepts of long-range order of a set of atoms , each of which is based on restrictions on the set of interatomic distances –. A set in ⁿ is aMeyer set if is a Delone set and there is a finite setF such that . Meyer proposed that such sets include the possible structures of quasicrystals. He obtained a structure theory for such sets, which reformulates results that he obtained in harmonic analysis around 1970, and which relates these sets to cut-and-project sets. In geometric crystallography V.I. Galiulin introduced the concept ofquasiregular set, which is a set such that both and – are Delone sets. This paper shows that these two concepts are identical.     

Analysis of the 33-133-133-1final state in photon-photon collisions

The reactione ⁺ e ^- e ⁺ e ^{- 00}e ⁺ e ^- 6 has been analysed using the full data sample taken with the Crystal Ball detector at the DORIS II storage ring at DESY. The ⁰⁰ invariant mass spectrum is dominated by the ', for which we determine the radiative width (') to be (4.5±0.3±0.5)keV. Near 1.9 GeV/c² we observe a second enhancement in the ⁰⁰ mass distribution. Assuming that these events are created by the production and subsequent decay of a wide resonanceX(1900), we have investigated the decay modes, the invariant mass distributions of the ⁰ and ⁰⁰ subsystems and the angular distributions of the final state mesons. We find that the data is best described byJ ^PC=2. For thisJ ^P assignment the resonance parameters are (X) BR(X)=(0.95±0.27±0.20) keV _tot (X)=(221±92±44)MeV, andM(X)=(1881±32±40) MeV/c².Deceased     

Measurement of γp→K + Λ and γp→K + Σ 0 at photon energies up to 1.47 GeV

The reactions pK ⁺ and pK ^{+ 0} have been measured with the multiparticle detector system SAPHIR at ELSA in Bonn. Besides the differential cross sections the polarization and, for the first time, the ⁰ polarization have been determined in a photon induced reaction. All data are presented as functions of the photon energy (from threshold up to 1.47 GeV) and of the kaon production angle (0°–180°). The polarization of both and ⁰ is substantial at all energies and varies strongly with the production angle.This work is supported by the Bundesminister für Forschung und Technologie (BMFT), FK 06 BN 621 I     

A study of the decays of tau leptons produced on theZ resonance at LEP

From the analysis of a data sample corresponding to an integrated luminosity of 4.63 pb^–1 taken during the 1990 run of LEP at centre of mass energies between 88.2 GeV an 94.2 GeV, the tau decays and their charge conjugates have been studied. The following branching ratios have been measured; , , Br(^{– –} (K^–)v)=11.9±0.7±0.7%, BR (^{– –} v)= 22.4±0.8±1.3%, in good agreement with world averages. The measured electronic and muonic branching ratios lead to a measurement of the strong coupling constant, _s (m) = 0.26 _–0.12 ^+0.09 . Extrapolating the _s value fromm tom _Z yields _s (m_Z) = 0.109 _–0.028 ^+0.012 .The average polarizationP of taus produced in Z ^{s s} decays has also been measured using the above decay modes. The weighted mean of the polarizations obtained from the four decay modes isP =–0.24±0.07. This value ofP gives, in the improved Born approximation, a ratio between the axial and vector coupling constants of the tau of /a = 0.12 ± 0.04, and hence a value of the effective electroweak mixing parameter sin² _W(m _Z ² ).     

Inclusive measurement of [`(p)]\bar p annihilation at rest in gaseous hydrogen to final states containingρ andf2

Antiproton annihilation at rest in gaseous hydrogen (16 bar pressure) to the final states (770)X andf ₂(1270)X, whereX stands for one or more neutral mesons, has been studied at LEAR using the CPLEAR detector. Relative branching ratios are given forX = ⁰,2 ⁰, 3 ⁰ in the case, and forX = ⁰, in thef ₂ case. The annihilation channel has not been measured before. The fraction of P-wave annihilation is deduced from the ratiof ₂ ⁰/ ⁰ to be 0.38±0.07, in good agreement with the result previously obtained by CPLEAR from the ratioK ⁺ K ^-/ ^{+ -}.     

Deeply bound pionic states with the (Σ −,Λ) reaction

We study the reaction ^– +A + (A ^–) with the ^– bound in the nucleus, as a means of producing deeply bound pionic states in nuclei, so far unobserved. The reaction is similar to the (n, p) reaction but, because of the ^–, mass difference, it allows the reaction to occur with smaller momentum transfer, thus increasing the transition probability and reducing the effects of distortion. The ratios of signal to background are one to two orders of magnitude better than in the (n, p) reaction.We would like to thank C. Dover and G. Tamas who helped us to get a perspective of the present and future possibilities of this and other reactions.One of us, J. Nieves wishes to acknowledge a fellowship from the Ministerio de Educatión y Ciencia. This work is partially supported by the CICYT. All the calculations have been done in the Centro Informático de la Universidad de Valencia.     

Chargino-neutralino production inp\bar p-collisions for the left-right supersymmetric model

An extension of the Supersymmetric Standard Model to the supersymmetricSU(2) _L×SU(2) _R×U(1) _B–L model is considered. The gauge group contains a bidoublet and triplet Higgs field. We investigate the possibility of detecting chargino and neutralino production in -collisions atCDF, namely . A numerical analysis is performed for , tan 1 and a lower bound on the lightest supersymmetric particle (LSP) mass, GeV. Using conservative assumptions ofM _WR300 GeV andgg _Lg _R, we find the cross sections are: , and pb, and thus _L 24 _L at TeV. Cross sections are also given for larger values of the center of mass energy up to those available at the SSC. The results are compared with the prompt-lepton background of theW _{L, R} ^– decays from . Both decays for bosons show Jacobian peaks for (p _T150 GeV forM _WR) at =90°. Furthermore the chargino signature unlike the promptlepton background is symmetric under the Jacobian peak. We also exhibit the dependence of the angular distribution of the chargino on the c.m. angle forp _T40 GeV, 150 GeV at TeV.     

LargeN expansion of QED: asymptotic photon propagator and contributions to the muon anomaly,for any number of loops

We calculate analytical contributions to then-loop asymptotic photon propagator from diagrams withn–1 electron loops, i.e. theO(1/N) terms in the largeN limit. The corresponding contributions to the on-shell -function, ()=6 log / logm reduced to rational combinations of _s = _p p ^–s . For the -function of the MOM scheme (i.e. the Gell-Man-Low function) we obtain theO(1/N) terms of

Logarithmic Sobolev inequality for lattice gases with mixing conditions

Let denote the grand canonical Gibbs measure of a lattice gas in a cube of sizeL with the chemical potential and a fixed boundary condition. Let be the corresponding canonical measure defined by conditioning on . Consider the lattice gas dynamics for which each particle performs random walk with rates depending on near-by particles. The rates are chosen such that, for everyn andL fixed, is a reversible measure. Suppose that the Dobrushin-Shlosman mixing conditions holds for forall chemical potentials . We prove that for any probability densityf with respect to ; here the constant is independent ofn orL andD denotes the Dirichlet form of the dynamics. The dependence onL is optimal.Research partially supported by U.S. National Science Foundations grant 9403462, Sloan Foundation Fellowship and David and Lucile Packard Foundation Fellowship.