Masses ofq 2 \bar q 2 states in a Bethe-Salpeter model

Ground-state masses ofq ^{2 –2} states (true and mock baryonium) are investigated in the framework of a Bethe-Salpeter formalism motivated from QCD. The four-particle system is described by pairwise interactions betweenqq orq pairs with a spectator approximation for the non-interacting pair. The quark-quark interactions are Coulomb plus harmonic interactions; the harmonic terms have been modified to produce linear confinement for heavier quarks, in agreement with experimental spectra. The confining interaction is proportional to the strong coupling constant _s. Apart from the quark masses, the confining interaction is characterized by three basic parameters: (i) a universal spring constant ₀; (ii) a constantC ₀/ ₀ ² , which defines the vacuum structure; (iii) a constantA ₀, which provides a smooth transition from quadratic to linear confinement as one goes from light to heavy quark systems. These three constants [ ₀ = 0.158 GeV;C ₀=0.296;A ₀=0.0283] have been shown to produce excellent fits to all quarkonia states [q ,q ,Q ] as well as baryon spectra (qqq); thus our predictions forq ^{2 2} states contain no free parameters. In this model, theL=0 ground states occur in the range 1.8–2 GeV, 2.15–2.3 GeV and 6.72–6.75 GeV foru ^{2 2},s ^{2 2} andc ^{2 2} states, respectively. We discuss the prospects for these states to be seen experimentally. In the case of thes ^{2 2} state, this is likely to have a rather narrow width, and may correspond to theX(2.22 GeV) meson observed in radiative decays of theJ/ meson. Thec ^{2 2} state might also be visible as a resonance with an appreciable width.Research supported in part by the National Science Foundation under grant NSF-PHY 86-06364Research supported in part by the U.S. Department of Energy     

B c and $$b\bar bc\bar c$$ at theZ 0-boson pole

The cross-section for the production of quarks ine ⁺ e ^– annihilation, that proves to be at a level of for is calculated within the frames of the QCD perturbation theory. The cross sections for the associated production of 1S-and 2S-wave states ofB _c-meson in the reaction were calculated in the nonrelativistic model of a heavy quarkonium. The number of _bc -hyperons to be expected at LEP is estimated on the basis of the assumption on quark-hadron duality.     

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.     

Understanding the scalar mesonq\bar q nonet

It is shown that one can fit the available data on thea _o(980),f _o(1300) andK _o ^* (1430) mesons as a distorted 0⁺⁺ nonet using very few (5–6) parameters and an improved version of the unitarized quark model. This includes all light two-pseudoscalar thresholds, constraints from Adler zeroes, flavour symmetric couplings, unitarity and physically acceptable analyticity. The parameters include a bare or mass, an over-all coupling constant, a cutoff and a strange quark mass of 100 MeV, which is in accord with expectations from the quark model. It is found that in particular for thea ₀(980) andf ₀(980) the component, in the wave function is large, i.e., for a large fraction of the time the state is transformed into a virtual pair. This component, together with a similar component of for thea ₀(980), and , and components for thef ₀(980), causes the substantial shift to a lower mass than what is naively expected from the component alone. Mass, width and mixing parameters, including sheet and pole positions, of the four resonances are given, with a detailed pedagogical discussion of their meaning.     

Composite weak bosons inpp(p\bar p) \to W^ \pm Z^0 X

We study the production process , where is a proton (antiproton), allowing an anomalous weak magnetic dipole moment parameter _Z in the ZWW vertex. We compute the pairWZ mass invariant, and total cross section production for various values of _Z .     

Binary reactions in $$\bar pp$$ collisions at intermediate energies

We discuss here the binary reactions of strange and charmed particle production in collisions at intermediate energies. In the case of baryon production with only one strange or charmed quark the cross section is determined by planar diagrams withK ^*,K ^** orD ^*,D ^**-meson poles in thet-channel. We calculated these diagrams in the frame of quark-gluon string model (QGSM) proposed earlier. We obtained also the cross-sections for reactions with baryon exchange in thet-channel with and pair in the final state. Predicted cross-sections for the reactions of production are of the order of hundred nanobarns. Using reggeon calculus we estimated cross-sections of binary reactions with two or three strange quarks in the final state: and . We discuss also the possible manifestation of color transparency effects in reactions with antiprotons on nuclei where all antiproton quarks annihilate.     

Scaling in prong-number distribution in\bar pp collisionscollisions

The prong-number distributions in collisions at relatively low laboratory momenta (≾7 GeV/c) exhibit the same type of scaling which has been observed in pp and π-N collisions at momenta ≿ 50 GeV/c.     

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.     

Partial wave analysis of $\bar pp \to \bar \Lambda \Lambda$

A partial wave analysis of PS185 data for is presented. A ³ S ₁ cusp is identified in the inverse process at threshold, using detailed balance to deduce cross sections from . Partial wave amplitudes for ³ P ₀, ³ F ₃, ³ D ₃ and ³ G ₃ exhibit a behaviour very similar to resonances observed in Crystal Barrel data. With this identification, the data then provide evidence for a new I = 0, J ^PC = 1^- resonance with mass MeV, MeV, coupling to both ³ S ₁ and ³ D ₁.Received: 4 June 2004, Published online: 9 July 2004     

Application of the method of hill determinant to theq \bar q confinement potentials

The Hill determinant method is discussed in the context ofq confinement power potential of typeV(r)= – V ₀–a/r + br, b > 0, which is commonly used for thec andb systems. The masses predicted by the potential are in good agreement with the experimental results.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia May 27–June 1, 1985.     

\left\langle {:\bar \psi \psi :} \right\rangle and three-point functions in QCD

We calculate the coefficients of to leading order in _s in the operator product expansion of the fundamental three-point functions of QCD in the deep Euclidean region. We demonstrate that these coefficients satisfy the Ward identities.Supported by BMFT 0233 REB4     

Determination of the strange quark content of the nucleon from a next-to-leading-order QCD analysis of neutrino charm production

We present the first next-to-leading-order QCD analysis of neutrino charm production, using a sample of 6090 ^– and -induced opposite-sign dimuon events observed in the CCFR detector at the Fermilab Tevatron. We find that the nucleon strange quark content is suppressed with respect to the non-strange sea quarks by a factor =0.477 _–0.053 ^+0.063 , where the error includes statistical, systematic and QCD scale uncertainties. In contrast to previous leading order analyses, we find that the strange seax-dependence is similar to that of the non-strange sea, and that the measured charm quark mass,m _c =1.70±0.19 GeV/c², is larger and consistent with that determined in other processes. Further analysis finds that the difference inx-distributions betweenxs(x) and is small. A measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V _cd |=0.232 _–0.020 ^+0.018 is also presented.     

Elastic pp scattering in the cern sps energy region

The pronounced dip-bump structure with a sharp minimum at |t| = 1.5 (GeV/c)², recently observed in elastic $\text{p}$p scattering at P_L = 50 GeV/c at the CERN SPS, is explained by the quark multiple scattering model with a realistic wavefunction for the proton and the antiproton. It is predicted that a second dip will appear around |t| = 7 (GeV/c)² at P_L = 50 GeV/ c and at higher energies.     

Phase transitions in random uniaxial systems with dipolar interactions

The critical behaviour of random uniaxial ferromagnetic (ferroelectric) systems with both short range and long range dipolar interactions is investigated, using the field theoretic renormalization method of Brézin et al. for the free energy above and below the transition pointT _c. The randomness is due to externally introduced fluctuations in the short range interactions (quenched case) or (and) magneto-elastic coupling to the lattice (annealed case). Strong deviations in the critical behaviour with respect to the pure systems are found. In the quenched case e.g. the specific heatC and the coefficientf ₂ (ofM ³ in the equation of state, whereM is the magnetization) change fromC |ln|t^1/3,f ₂ |ln|t^–1 in the pure system toC is the reduced temperature andA _±,C _± are constants) in the random situation. This change should e.g. be experimentally observable by deuterization of the ferroelectric tri-glycine sulfate where the logarithmic behaviour off ₂ has already been detected in the pure case. For nonvanishing magnetoelastic coupling a complex critical behaviour is obtained and discussed. We find the interesting result that if both quenched randomness and a weak magnetoelastic coupling are present the quenched random critical behaviour dominates in the close vicinity ofT _c. Finally the influence of the magnetoelastic coupling on the longitudinal phonons in investigated and it is found that the relative changes in the corresponding elastic constant and structure factor are proportional to the specific heat and the wavevector dependent energy-energy correlation function respectively, suggesting new experiments.     

Invariant measures for the2D-defocusing nonlinear Schrödinger equation

Consider the2D defocusing cubic NLSiu _t+u–u|u|²=0 with Hamiltonian . It is shown that the Gibbs measure constructed from the Wick ordered Hamiltonian, i.e. replacing ||⁴ by ||⁴ :, is an invariant measure for the appropriately modified equationiu _t + u‒ [u|u ²–2(|u|² dx)u]=0. There is a well defined flow on thesupport of the measure. In fact, it is shown that for almost all data the solutionu, u(0)=, satisfiesu(t)–e ^it C _Hs (), for somes>0. First a result local in time is established and next measure invariance considerations are used to extend the local result to a global one (cf. [B2]).     

Evidence for non-q \bar q mesons

The non-Abelian nature of QCD suggests that particles that have a gluon constituent, such as glueballs or hybrids, should exist. In addition,q q states are also predicted. This paper describes a search for these non-q q mesons performed by experiment WA 76 using the CERN Omega Spectrometer and discusses three candidates which have been observed.Invited talk at HEXAM 89, Bechyn Castle, Czechoslovakia, June 25–30, 1989.     

Hyperon production in\bar pp interactions at 22.4 GeV/c

In the present paper we investigate the production of charged hyperons and antihy-perons in p interactions at 22.4 GeV/c recorded in the 2m hydrogen bubble chamber Ludmila. After correction for losses due to the kinematics of hyperon decays and for scanning efficiency we have obtained 610 events with charged hyperons or antihyperons. A total cross section of 1.3 _–0.05 ^+0.4 mb for ^±/ has been obtained, and various associated charged particle multiplicity distributions are presented.We would like to express our gratitude to the Ludmila collaboration for the experimental material and continuous interest in this work. Especially we would express our sincere thanks to Professor I. M. Gramenitskii for his critical comments and fruitful discussions.     

Q\bar Qg state at finite temperature

Within the framework of ellipsoidal bag model, the state at finite temperature is investigated, and the dependence of the energy of the system on the interquark separation is obtained. We calculate the spectrums of and statesat different temperature for TM and TE mode respectively.     

What Can High-Energy Elastic Scattering Tell Us About Nucleon Structure?

Basic assumptions used in the analysis of elastic differential cross section data will be discussed and the arguments for the transparency of nucleons will be analyzed. It will be shown that the transparency of nucleon is a direct consequence when a weak t dependence of hadronic amplitude phase is used in analogy with optics. The phase t dependence may be hardly uniquely determined from elastic scattering data, being only partially limited by the Coulomb-hadronic interference existing in a very narrow region of small |t| values. The given situation will be demonstrated with the help of data for collisions at 541 GeV; nucleons being transparent or having hard cores may be admitted by the elastic data themselves. However, when further characteristic of inelastic and elastic processes are compared, the nucleon with hard core should be preferred. The most probable characteristics of nucleon structure derived from the data will be presented.