Unified QCD determination of all vector meson coupling constants

Coupling constants of all vector mesons are determined in QCD by means of a new QCD sum-rule method. The results are found to be sensitive to the binding energy (i.e. meson and quark mass differences). For standard values of quark masses we obtainf =202 MeV,f _K*=216 MeV,f _D*=212±22 MeV,f _B*=138±42 MeV, and . Based on this approach the spin-flavour symmetry for the heavy quark systems are also discussed.Supported by Bundesministerium für Forschung und Technologie     

Magnetic monopole interactions: Shell structure of meson and baryon states

It is suggested that a low-mass magnetic monopole of Dirac chargeg=(137/2)e may be interacting with ac-quark's magnetic dipole moment to produce Zeeman splitting of meson states. The massM ₀=2397 MeV of the monopole is in contrast to the 10¹⁶-GeV monopoles of grand unification theories (GUT). It is shown that shell structure of energyE _n =M ₀+1/4nM ₀+ exists for meson states. The presence of symmetric meson states leads to the identification of the shell structure. The possible existence of the 2397-MeV magnetic monopole is shown to quantize quark masses in agreement with calculations of quantum chromodynamics (QCD). From the shell structure of meson states, the existence of two new mesons is predicted:(1814±50 MeV) withI ^G(J ^PC =0⁺(0^–+) and _c (3907±100 MeV) withJ ^PC =0^–+. The presence of shell structure for baryon states is shown.     

The strange quark mass from QCD sum rules

The strange quark mass is calculated from QCD sum rules for the divergence of the vector as well as axialvector current in the next-next-to-leading logarithmic approximation. The determination for the divergence of the axial-vector current is found to be unreliable due to large uncertainties in the hadronic parametrisation of the two-point function.From the sum rule for the divergence of the vector current, we obtain a value of (1 GeV)=189±32 MeV, where the error is dominated by the unknown perturbativeO( _s ³ ) correction. Assuming a continued geometric growth of the perturbation series, we findm _s =178±18 MeV. Using both determinations ofm _s , together with quark-mass ratios from chiral perturbation theory, we also give estimates of the light quark massesm _u andm _d.     

The <Emphasis Type="Italic">η</Emphasis>′ meson from lattice QCD

We study the flavour-singlet pseudoscalar mesons from first principles using lattice QCD. With N _f=2 flavours of light quarks, this is the so-called η ₂ meson and we discuss the phenomenological status of this meson. Using maximally twisted-mass lattice QCD, we extract the mass of the η ₂ meson at two values of the lattice spacing for lighter quarks than previously discussed in the literature. We are able to estimate the mass value in the limit of light quarks with their physical masses.     

Some two body non-leptonicB decays and estimation off D in the heavy quark effective theory

We have studied some of the two body nonleptonic decays ofB meson in the context of heavy quark effective theory using factorization hypothesis. Treatinga ₁ as a free parameter, we have obtained its value asa ₁=0.822±0.045, by correlating the experimental and predicted branching ratio for process. With this value ofa ₁ the branching ratios obtained for other decay channels are in good agreement with the experiment. The decay constant ofD meson is extracted to be 280.82 MeV. Heavy quark spin symmetry has also been tested.     

Production rate and decay lifetime measurements ofBs0 mesons at LEP usingDs and? mesons

The study of the properties of inclusive production ofD _s mesons and of events in which a and a muon are present in the same jet provides two independent measurements of the probability,f _s ^w , for a heavy quark to hadronize into a strangeB orD meson. The data sample analysed corresponds to 243,000 hadronicZ ⁰ decays. The combined value of these measurements isf _s ^w =0.19±0.06±0.08. From the flight distance distributions ofD _s and of (-lepton) secondary vertices, with the lepton emitted at high transverse momentum relative to the jet axis, two values are obtained for theB _s ⁰ meson lifetime. Combining these measurements with a previous result based on the study ofD _s- events, theB _s ⁰ meson lifetime is measured to be: 0.96±0.37 ps.     

Is the number of light flavors in QCD great?

At a qualitative level, it is well known that QCD featuring a large number of quark flavors must differ drastically from actual QCD. However, it is possible to consider the large-N_f limit (where N_f is the number of light flavors in QCD) such that the basic dynamics of the system remains unchanged. This is the region of chiral perturbation theory, where the limit N_f → ∞ is simultaneously the limit of a large number of colors, N_c. Features are indicated that make it possible, in such a situation, to compare analytically the same quantity in a simplified model of actual QCD and in the large-N_f limit, and methods are proposed for calculating these features. Calculations in the limit N_f → ∞ are of no use in assessing quantities of the theory at small N f.     

<Emphasis Type="Italic">B</Emphasis> to light meson transition form factors calculated in perturbative QCD approach

We calculate the , (P is the light pseudoscalar meson, V the light vector meson) form factors in the large-recoil limit in the perturbative QCD approach, including both the vector (axial vector) and tensor operators. In general there are two leading components and for the B meson wave functions. We consider both contributions of them. Sudakov effects ( and threshold resummation) are included to regulate the soft end-point singularity. By choosing the hard scale as the maximum virtualities of the internal particles in the hard b quark decay amplitudes, Sudakov factors can effectively suppress the long-distance soft contribution. The hard contribution can be dominant in these approaches. Received: 27 December 2002 / Published online: 5 May 2003 RID="a" ID="a" e-mail: lucd@mail.ihep.ac.cn RID="b" ID="b" e-mail: yangmz@mail.ihep.ac.cn     

Study of the centrally producer ππ andK \bar K systems at 85 and 300 GeV/c

We have studied the andK systems centrally produced in proton proton collisions at 300 GeV/c and ⁺/p proton collisions at 85 GeV/c using the CERN spectrometer. Clear evidence forS ^*/f _o(975) production is observed. An analysis performed on the ^{+ –} mass spectrum in the 1.0 GeV region, using a coupled channel formalism, shows that it is possible to describe theS ^*/f _o(975) effect with one single resonance once interference of theS ^*/f _o(975) with theS-wave background is introduced. The resultingS ^*/f _o(975) parameters arem _o =979±4MeV,g =0.28±0.04,g _K =0.56±0.18 corresponding to a pole position on sheet II at (1001±2)–i(36±4) MeV. Evidence is also found for a structure having a mass of 1472±12 MeV and a width of 195±33 MeV.     

A determination ofα s from the transverse momenta of hadrons produced in neutrino and antineutrino interactions

TheW andQ ² dependence of the transverse momentum of the forward-going hadrons in deep inelastic neutrino charged current interactions on neon is studied. The data were obtained by exposing BEBC filled with a Ne/H₂ mixture to the CERN SPS wide-band neutrino beam. The data on average transverse momentum are compared to a model which includes first order QCD, intrinsic quark momentum in the nucleon and Fermi motion, as well as a simple model for hadronization. The model is found to describe the data well. Values of _s =0.16±0.02(stat)±0.02(syst.)±0.03(frag.) at an averageQ ² of 15.4±0.4 GeV²/c² and (stat.) _–90 ⁺¹⁰⁰ (syst.) _–90 ⁺¹³⁰ , (frag.) MeV/v for three flavours are extracted.     

Tests of the infinite mass effective theory and properties of the charming and beautiful mesons

Using an operator product expansion (OPE) in the inverse of the heavy quark massM _Q and a dispersive approach, we rederive theB andB ^* couplings and the Isgur-Wise function predicted by the infinite mass effective theory (IMET). We find that, at the subtraction pointM _Q and using VDM for the spectral function, these observables are governed by the universal light quark condensate. We also find that the corrections induced by finite values ofM _c andM _b are large and are due to the splitting _b between the ground state and its radial excitation. We review the determinations of the different decay constants, couplings and masses from QCD spectral sum rules (QSSR). Forf _B andf _D , we conclude the optimum average:f _B =(1.59±0.09±0.27)f andf _D =(1.31±0.12)f , where the main error is due to the quark mass, while the first one inf _B is due to the non-perturbative terms and to the choice of the continuum thresholdt _c from the onset of sum rule variable stability until thet _c -stability regions. We also find that the vector coupling _V satisfies approximately the IMETM _Q ^3/2 mass dependence scaling law, whilef _P obeys in units of GeV:f P/f(4.6±0.4)M _Q ^–1/2 (1–1.56/M _Q +0.88/M _Q ² ), forM _Q M _c . We also predict the flavour independence:M _P -M _Q 0.6-0.7 GeV andM _V -M _Q 0.7-0.8 GeV of the mass differences between the mesons and the corresponding quark. Finally we find that theBDev _e form factorf ₊(0)(0.55±0.10) deviates from the naive expectation (f ₊(0)=1).     

Hadron spectrum and infrared-finite behavior of QCD running coupling

We study the behavior of the QCD effective coupling α _s in the low-energy region by exploiting the conventional meson spectrum within a relativistic quantum-field model based on analytical confinement of quarks and gluons. The spectra of quark-antiquark and two-gluon bound states are defined by using a master equation similar to the ladder Bethe-Salpeter equation. A new, independent and specific infrared-finite behavior of QCD coupling is found below energy scale ∼1 GeV. Particularly, an infrared-fixed point is extracted at α _s (0) ≅ 0.757 for confinement scale Λ = 345 MeV. We provide a new analytic estimate of the lowest-state glueball mass. As applications, we also estimate masses of some intermediate and heavy mesons as well as the weak-decay constants of light mesons. By introducing only a minimal set of parameters (the quark masses m _f and Λ) we obtain results in reasonable agreement with recent experimental data in a wide range of energy scale ∼0.1–10 GeV. We demonstrate that global properties of some low-energy phenomena may be explained reasonably in the framework of a simple relativistic quantum-field model if one guesses correct symmetry structure of the quark-gluon interaction in the confinement region and uses simple forms of propagators in the hadronisation regime. The model may serve a reasonable framework to describe simultaneously different sectors in low-energy particle physics.     

Flavor mixing in the low energy hadron dynamics: Interplay of theSU f (3) breaking and theU A (1) anomaly

We extend our previous investigation about the flavor mixing or the OZI violating process in the light quark systems with the use of the generalized Nambu-Jona-Lasinio model incorporating theU _A (1) anomaly. The OZI breaking effects newly studied in the meson sector include the and meson decay constants, their couplings with nucleon as well as the masses and the mixing property of the scalar mesons. As for the baryon sector, we reexamine the strangeness content of the proton and the -N sigma term _N by taking into account the interactions between the constituent quarks. It is found that the short-range spin-spin interaction between the quarks gives anO(10 MeV)-enhancement for the theoretical value of the sigma term. Anomalous quark contents of other octet and decuplet baryons (hyperons) are also examined. It is shown that the axial anomaly induces the anomalous quark contents which are not expected in the naive quark model, while the short-range interaction between the quarks acts to suppress (enhance) the quark contents of the decuplet (octet) baryons. All the results indicate that the following picture holds systematically:m _s is so large that (i) the strangeness mixing induced by the anomaly is considerably suppressed and that (ii) the naive chiral perturbation does not work in the strange sector even in the tree level of the meson fields (largeN _c limit). The spin problem of nucleon, which is another subject related to the flavor mixing, is also examined with the use of our effective model.This paper is a modified version of the paper SUNY-NTG-89-49, RYU-THP-89-2 (August 1989)     

Instanton interpolating current for σ-tetraquark

We perform a QCD sum rule analysis for the light scalar meson σ   (f₀(600)$f_0(600)$) with a tetraquark current related to the instanton picture for QCD vacuum. We demonstrate that instanton current, including equal weights of scalar and pseudoscalar diquark–antidiquarks, leads to a strong cancelation between the contributions of high dimension operators in the operator product expansion (OPE). Furthermore, in the case of this current direct instanton contributions do not spoil the sum rules. Our calculation, obtained from the OPE up to dimension 10 operators, gives the mass of σ-meson around 780 MeV.     

CP violating measures for D mesons

From the pole dominance approximation for transformation an estimate of the M _d or the mass difference of D _L ⁰ and D _s ⁰ meson has been found out. The results obtained are close to that of Donoghue et al. Two gamma decay width of D⁰ meson has also been calculated. Further calculations from the box diagram approach for this meson have been carried out by modifying the CKM matrix in the light of recent observation of top quark massm _t=174 GeV while maintaining the prediction for the K⁰ meson undisturbed.     

Leptonic constant of the pseudoscalar <Emphasis Type="Italic">B</Emphasis><Subscript><Emphasis Type="Italic">c</Emphasis></Subscript> meson

We calculate the leptonic constant for the pseudoscalar ground state of the B _c meson in the framework of a QCD-motivated potential model taking into account the two-loop anomalous dimension for the heavy quark current in nonrelativistic QCD as matched with full QCD.     

Particle masses,force constants,and Spin(8)

From a number of qualitative conjectures, the constantsm _e ,c, , and a spin(8) gauge field theory, I derive the following particle masses (quark masses are constituent masses) and force constants: up quark mass=312.7542 MeV; down quark mass=312.7542 MeV; proton mass=938.2626 MeV; neutrino masses (all types)=0; muon mass=104.76 MeV; strange quark mass=523 MeV; charmed quark mass=1989 MeV; tauon mass=1877 MeV; bottom quark mass=5631 MeV; top quark mass=129.5 GeV;W ⁺ mass=80.87 GeV;W ^– mass=80.87 GeV;W ₀ mass=99.04 GeV; fine structure constant= 1/137.036082; weak constant times the proton mass squared M _p ² =0.97×10^–5; color constant=0.6286. From the pion mass in addition, I derive the Planck mass (1–1.6)×10¹⁹ GeV, so that the gravitational constant times the proton mass squared GM _p ² (3.6–8.8)×10^–39.