QCD: The $ \Lambda$(1405) as a hybrid

Using the QCD sum rule method, we estimate the mass of the lowest strange mixed hybrid/three-quark baryon with IJ ^P = 0(1/2)^- . We find the mass for a hybrid is approximately that of the L \Lambda(1405) , whose nature has been a puzzle for many decades. Possible tests of this result are discussed.     

Symmetry breaking and asymptotic freedom in colour SU(3) gauge models

A class of quark models based on the colour gauge group SU(3) is shown to be asymptotically free despite the conplete breakdown of local symmetry to guarantee infrared stability. The symmetry breakdown is achieved by the presence of elementary scalar fields either through the Higgs mechanism or dynamically as first proposed by Coleman and Weinberg. Asymptotic freedom is preserved by imposing eigenvalue conditions on the coupling constants as first proposed by Chang. New quark species must be present, but below their production threshold, colour can still be a global symmetry which is approximate under SU(3), but exact under SU(2). Among the many implications of this class of models is the possibility of producing isolated quarks and gluons of non-zero mass without altering the short-distance behaviour of the superstrong interaction which binds them.     

The process $\gamma(^*) + p \to \eta_c + X$: a test for the perturbative QCD odderon

The rates of inclusive photo- and electroproduction of the meson: are calculated in the triple Regge region, integrated over the diffractive mass X. For the Regge exchanges we use the hard pomeron and odderon, both being calculated in the framework of perturbative QCD. The integrated cross section depends upon the coupling of the BFKL pomeron to two C = -1 odderons, and it is found to be of the order of 60 pb for photoproduction and 1.5 pb at Q² = 25 GeV².Received: 16 April 2003, Published online: 25 February 2004     

Improved QCD vacuum for gauge groups SU(3) and SU(4)

The effective energy for a covariantly constant background field in a pure Yang-Mills theory is calculated to loop order one. For gauge group SU(3) [SU(4)] it is found that the “vacuum” configuration consists of two [three] constant color magnetic fields of equal non-zero magnitude orthogonal to each other in color as well as physical space. We conclude that the structure of the Copenhagen vacuum is more complex than previously expected.     

The QCD effective Lagrangian for ordinary quarks in a constant self-dual background mean-field is confining

The formalism is Adler's mean-field approximation to QCD. The model involves ordinary, massive quarks moving in a constant background field, which is Leutwyler's self-dual solution of the Yang-Mills equations. The outcome is quark confinement, independently of the number of flavors.     

The Coupling Constants for an Electroweak Model with an SU(4)PS\otimes SU(4)EW Unification Symmetry

We introduce the sequence of spontaneous symmetry breaking of a coupling between Pati-Salam and electroweak symmetries SU(4)_PS\otimes SU(4)_EW in order to establish a mathematically consistent relation among the coupling constants at grand unification energy scale. With the values of baryon minus lepton quantum numbers of known quarks and leptons, by including right-handed neutrinos, we can find the mixing angle relations at different energy levels up to the electromagnetic U(1)_EM scale.     

The Sugawara model in general relativity. A. The case for three current vectors (SU (2))

A general method of solving the equations of Sugawara's field theory of currents has been developed, and illustrated by applying it to the set of three currents. These are inserted into Einstein's field equations which have been solved together with the co-variant ‘gauge’ conditions for a gravitational field involving cylindrical symmetry. A further transformation exhibits the triad formed by the current vectors and exhibits clearly the deviations of the line-element from Schwarzschild's exterior solution. In a subsequent paper the case for eight vector currents corresponding toSU (3) will be treated in similar fashion.     

The Branching Rules for SU(2N)⊃(SU(N)⊃O(N)⊃O(3))⊗SU(2) and the Highest Weight States for SU(N) and O(N)

Simple analytical recurrent formulae of the branching rules for group chain SU(2N)⊃(SU(N)⊃O(N)⊃O(3))⊗SU(2) are obtained. The highest weight states for the irreducible representations [2^al^b] or {nS} of group SU(N) and for the irreducible representations (2^α1^β) or (υS) of group O(N) are constructed respectively     

The behavior of the effective gravitational constants for broken SU(5)

In a broken SU(5) GUT at scales much below the superheavy mass, heavy fields decouple. The light fields obey an effective field theory obtained by integrating away the heavy fields. The gravitational couplings are also affected by this integration. The effective gravitational couplings are found, and their space-time and scale dependence are investigated.     

X-ray scattering for the atomic structure of a barium-induced Si(111)-3 $\times$ 2 surface

We have investigated the atomic arrangement of a barium (Ba)-induced Si(111)-3×2 surface by using surface-sensitive synchrotron X-ray scattering. In-plane fractional-order reflections obtained from three rotational domains of 3×1 symmetry have been used to examine several competing structural models including the honeycomb-chain-channel (HCC) and the double-π-bonded chain (DπC) models. By fitting two different data sets, both the goodness-of-the fits χ² and the residuum R-factor strongly favor the HCC over the DπC model. We conclude that a Ba-paired HCC structure with a \(\frac{1}{3}\) monolayer of Ba coverage best describes the Ba-induced 3×2 surface with a Ba-Ba interatomic spacing d?=?1.93 Å.     

The (BFKL) Pomeron-\gamma^*-\gamma vertex for any conformal spin

To study diffractive photon production at HERA, we compute the projection of the impact-factor on the BFKL leading-order eigenfunctions for non-zero transfer. This calculation supplements former ones performed for n = 0. We provide an expression for and check that all the other components are zero. Received: 6 September 1999 / Revised version: 21 November 1999 / Published online: 17 March 2000     

SU(3) analysis of annihilation contributions and CP violating relations in B\to P P decays

Several methods proposed to measure the angle in the KM unitarity triangle assumed that the tree contribution to is purely due to annihilation contributions and is negligibly small. This assumption has to be tested in order to have a correct interpretation of the experimental data. In this paper we show that using SU(3) symmetry, the smallness of the tree contribution can be tested in a dynamic model-independent way. We also derive several relations between CP violating rate differences for decays without assuming the smallness of the annihilation contributions. These relations provide important tests for the standard model of CP violation. Received: 5 January 1999 / Revised version: 4 March 1999 / Published online: 18 June 1999     

Estimates for parameters and characteristics of the confining SU(3)-gluonic field in neutral kaons and chiral limit for pseudoscalar nonet

The first part of the paper is devoted to applying the confinement mechanism proposed earlier by the author to estimate the possible parameters of the confining SU(3) -gluonic field in neutral kaons. The estimates obtained are consistent with the widths of the electromagnetic decays K ⁰,[`(K)]⁰ \bar{{K}}^{0}_{} ? \rightarrow 2g \gamma too. The corresponding estimates of the gluon concentrations, electric and magnetic colour field strengths are also adduced for the mentioned field at the scales of the mesons under consideration. The second part of the paper takes into account the results obtained previously by the author to estimate the purely gluonic contribution to the masses of all the mesons of the pseudoscalar nonet and also to consider a possible relation with a phenomenological string-like picture of confinement. Finally, the problem of masses in particle physics is shortly discussed within the framework of the approach to the chiral symmetry breaking in quantum chromodynamics (QCD) proposed recently by the author.     

The string tension and the scaling behavior of SU(2) gauge theory on a random lattice

The SU(2) gauge theory on an 8⁴ random lattice has been studied by the Monte Carlo method. The string tensions have been evaluated. They display the expected scaling behavior for β=1.2−1.3. The scale parameter Λ_RAN has been determined approximately.     

The goldstone pion in SU(2) lattice QCD at low quark mass: Scaling and finite size effects

Results for the pion sector of an extensive numerical simulation of quenched SU(2) QCD with staggered fermions are presented. A wide range of quark masses, gauge couplings and lattice sizes is investigated. The systematic and statistical errors are carefully analyzed. Finite size effects occurring on small lattices and/or at low quark masses are studied in detail. When they are absent or weak, we find that the pion mass and coupling constant verify approximate scaling behaviour at low quark mass for β ≳ 2.4. We determine the K and π coupling constants to be in the ratio 1.25(5). At β = 2.3, we show that the square pion mass contains a substantial contribution which is non-linear in the quark mass and renders chiral limit extrapolations less reliable.     

Radiative return at $\Phi$ - and B-factories: FSR for muon pair production at next-to-leading order

Muon pair production through the radiative return is of importance for a measurement of the hadronic production cross section in two ways: it provides an independent calibration and it may give rise to an important background for the measurement of the pion form factor. With this motivation the Monte Carlo event generator PHOKHARA is extended to include next-to-leading order radiative corrections to the reaction . Furthermore, virtual ISR corrections to FSR from pions are introduced, which extends the applicability of the generator into a new kinematical regime. Finally, the effect of photon vacuum polarization is introduced into this new version of the generator.Received: 8 April 2004, Revised: 3 December 2004, Published online: 25 January 2005Work supported in part by BMBF under grant number 05HT9VKB0, EC 5th Framework Programme under contract HPRN-CT-2002-00311 (EURIDICE network), TARI project HPRI-CT-1999-00088, Polish State Committee for Scientific Research (KBN) under contract 2 P03B 017 24, BFM2002-00568, Generalitat Valenciana under grant GRUPOS03/013, and MCyT under grant FPA-2001-3031.     

Properties of the πη,$ \eta{^\prime}$,σ, f0(980) and a0(980) mesons and their relevance for the polarizabilities of the nucleon

The signs and values of the two-photon couplings F _Mγγ of mesons (M) and their couplings g_MNN to the nucleon as entering into the t -channel parts of the difference of the electromagnetic polarizabilities (α - β) and the backward angle spin polarizabilities γ_π are determined. The excellent agreement achieved with the experimental polarizabilities of the proton makes it possible to make reliable predictions for the neutron. The results obtained are α_n = 13.4±1.0 , β_n = 1.8±1.0 (10^-4fm^3), and γ⁽ⁿ⁾ _π = 57.6±1.8 (10^-4fm^4). New empirical information on the flavor wave functions of the f ₀(980) - and the a ₀(980) -meson is obtained.     

The \gamma \gamma \to Z Z process and the search for virtual SUSY effects at a \gamma \gamma Collider

We study the helicity amplitudes of the process in the Standard Model at high energy. These amplitudes receive contributions from the W and charged quark and lepton loops, analogous to those encountered in the cases studied before. But also receives contributions from the Higgs s-channel poles involving the effective Higgs- vertex. At energies , the amplitudes in all three processes are mainly helicity-conserving and almost purely imaginary; which renders them a very useful tool in searching for New Physics. As an example, a SUSY case is studied, and the signatures due to the virtual effects induced by a chargino-, charged slepton- or a lightest stop-loop in , are explored. These signatures, combined with the analogous ones in and , should help identifying the nature of possible New Physics particles. Received: 3 September 1999 / Published online: 3 February 2000