Photonic production ofS- andP-waveB c states and doubly heavy baryons

Numerical calculations for the production ofS-andP-wave levels ofB _c quarkonium inγγ collisions are performed in the leadingO(α _s ² α _em ² ) order of perturbation theory. The total cross-section ofP-wave state production is about 10 % of that for theS-wave levels. The contribution of fragmentation component (6+6 diagrams) is low, and the basic contribution is determined by the recombination mechanism (8 Feynman diagrams). The gauge invariant term of the $\bar b$ →B _c fragmentation (6 diagrams) quite accurately reproduces the result of the fragmentation model, whereas there is a strong deviation of thec→B _c fragmentation term from the predictions of the fragmentation model. The total cross-sections in photonic production of doubly heavy diquark, hadronizing into the baryons, are evaluated.     

Production of P-wave charmonium states in two-particle decays of B c mesons

On the basis of the model of hard one-gluon exchange, the two-particle hadronic decays of B _c mesons into S-and P-wave charmonium states, B _c → X _cc π(ρ), are considered at high momentum transfers and in the nonrelativistic approximation. It is shown that the width with respect to B _c-meson decay into S-wave charmonium states is two times greater than the width with respect to B _c-meson decay into P-wave states and that the yield of J/ψ mesons in the cascade processes of B _c-meson decay via the formation and radiative decay of P-wave charmonium states is approximately 8% of the yield of directly produced J/ψ mesons.     

Properties of<Emphasis Type="Italic">B</Emphasis><Subscript>c</Subscript> meson

The mass spectrum ofcb meson is investigated with an effective quark-antiquark potential of the form -α_c/r +Ar ^νwith ν varying from 0.5 to 2.0. TheS andP-wave masses, pseudoscalar decay constant, weak decay partial widths in spectator model and the lifetime ofB _cmeson are computed. The properties calculated here are found to be in good agreement with other theoretical and experimental values at potential index,ν = 1     

Hadrinoc production of χ c -nesons at LHC

Hadronic production of P-wave charmonium states χ _cJ in hadronic interaction is considered. Using the experimental results of CDF and LHCb collaborations, we show, that contributions of color singlet components are dominant. As for the color octet mechanism, then we show, that contributions from P-wave states can also be observed, while the contribution from S-wave is negligible. The best experimental observables that give information about relative importance of color-singlet and color-octet components are the ratios χ _c2/χ _c1 and χ _c 0/χ _c1.     

Determination of meson resonance contributions to pion and kaon inclusive spectra

π- andK-meson inclusive spectra with low transverse momenta inK-meson fragmentation region inKp-interactions are determined on the basis of the assumption on a recombination mechanism of hadron production. It is shown that the pion and kaon spectra (both “direct” and from resonance decay) inK-meson fragmentation region can be expressed by structure functions of initialK-meson. Contributions from resonance decays from different meson multiplets (vector, axial and tensor) to pion and kaon inclusive spectra are determined. α=(3A _T /5A _V )=0.28±0.02 is found for the suppression factor ofP-wave meson state production as compared to theS-wave one. It is shown that with decreasing final meson mass the relative contribution of direct production to meson inclusive spectrum increases. In the limits of available experimental errors in meson resonance spectra there is found no dependence of meson yields on the value of summary spin of quark and antiquark producing meson (β=3A _P /A _V =1). It is shown that analysis of meson resonance inclusive spectra allows one to determine not only the parameters of valence quark distribution in the initialK-meson but also the sea parton distributions. For the strange sea quark distribution inK-meson there is founds _S(x) ～(1?x) ^ns wheren _S =4.8±1.0, which agrees with the prediction of the quark counting rules for this quantity.     

Quark-hadron duality and meson-meson scattering amplitudes

We investigate a special concept of quarkhadron duality in meson physics at low and intermediate energies. With a relativistic propagator for confined quarks, we calculated masses and widths of the mesons which areS- andP-wave states ofq¯q (J ^P=0^?, 1^?, 0⁺, 1^+c, 2⁺) as well as meson-meson scattering amplitudes at energies up totrs ≤ 1.3 GeV by including light pseudoscalar and vector mesons into the interaction dynamics. Our investigation shows that the influence of the light meson dynamics resutls in:

1. a contribution to the constituent quark mass of approximately 200 MeV.
2. the appearance of a new soft confinement force barrier responsible for the formation of the highly excited meson states.

     

J/ψ+η′ Production ine + e −-annihilation: A perturbative QCD calculation

The cross section for the reactione ⁺ e ^?→³S₁+¹S₀ is calculated in the framework of perturbative QCD, using the nonrelativistic approximation for the³S₁ and¹S₀ bound states. The model is applied toJ/Ψ plus η,η,η′, andl production. We find extremely small rates in contrast to previous estimates based on vector meson dominance and discuss possible reasons for this difference.     

ψψ production at collider energies

We estimate ψψ production at collider energies in the framework of perturbative QCD. TheO(α _s ² )?(α _s ⁴ ) parton cross-sections, with the non-relativistic approximation for the heavy quark bound states, are used. This first insight into the characteristics of the kinematical distributions allows predictions on the predominance of the quark, gluon orB meson production mechanisms in particular kinematical regions.     

Spin effects in two-body hadronic decays of the B c mesons

Spin effects in the weak two-body hadronic decays of the B _c and B _c ^* mesons into J/ψ and ρ(π) mesons are considered within the model of hard one-gluon exchange between quarks at high momentum transfers. It is shown that the polarization of the J/ψ meson in the decays of the B _c ^* meson differs substantially from that in the decays of the B _c ^* meson. The decay widths of the B _c ^* meson differ significantly from the widths of the B _c ^* meson.     

Perturbative fragmentation of a vector color particle into bound states involving a heavy antiquark

Vector-particle fragmentation into possible S-wave bound states involving a heavy antiquark is considered for high-energy processes at high transverse momenta, and the relevant fragmentation function is calculated in the leading order of perturbative QCD for various patterns of the anomalous magnetic moment. One-loop equations describing the q ² evolution of the fragmentation-function moments that is caused by hard-gluon emission from the vector particle are derived. The integrated probabilities of fragmentation are obtained. The distribution of the bound state in the transverse momentum defined with respect to the fragmentation axis is calculated in the scaling limit.     

Pseudoscalars and vector mesons in a unitary and self-consistently broken SU(6) W scheme

We estimate hadronic self-energy effects to “bare” pseudoscalar (P) and vector (V) meson states due to theP→PV→P, P→VV→P, V→ PP→V, V→PV→V andV→VV→V loops. We simulate higher order diagrams by consistently requiring external and internal particles to have the same mass. We find good agreement with all the experimental masses (exceptm _π), widths and mixing angles. The “bare”P andV states are heavy (≈1.26 GeV) and degenerate up to a smallm _s?m_u quark mass difference term. The “bare” coupling constants for thePPV, PVV andVVV vertices obey exact OZI rule and almost exact SU(6) _W symmetry. We use a common cut-off ofk _cm?0.7 GeV/c corresponding to a harmonic oscillator radius of ?0.7 fm for all SU(6) _W related thresholds except for the pion.     

Constant-cutoff approach to meson-hyperon couplings

The kaon coupling constants at hyperon-nucleon vertices and the pion coupling constants at hyperon-hyperon vertices are calculated in the framework of the constant-cutoff approach to the CHK bound-state model of hyperons, where the postive-parity hyperons such as Λ, Σ, and ∑^*=∑(1385) are theP-wave bound states of an antikaon and theSU(2) Skyrme soliton, while Λ^* is theS-wave bound state. Meson coupling constants are defined as matrix elements of the meson-source terms between two single-baryon states following the method developed for resolving the Yukawa coupling problem in theSU(2) Skyrme soliton model. The magnitudes of the meson coupling constants are found to be close to those obtained using the complete Skyrme model and the phenomenological values.     

Contributions of parity-violating baryon matrix elements to nonleptonic charmed-baryon decays

Baryon-baryon matrix elements of the parity-violating charm-changing weak Hamiltonian are calculated using the MIT bag model. The changes in thes- andp-wave amplitudes of Cabibbo-favored nonleptonic decays of charmed baryons due to these parity-violating baryon transition elements are in general not substantially significant. However, they can overwhelm or be comparable to the contributions arising from the parity-conserving matrix elements for some reactions such as thes-wave amplitude ofΛ _c ⁺ →Ξ ⁰ K ⁺ and Δ⁺⁺ K ^? and thep-wave amplitude ofΛ _c ⁺ →∑ ⁰π⁺.     

P-Matrix analysis of the dibaryon1 D 2 resonance

We study the relation between intermediate energy nucleon-nucleon scattering and the eigenstates of the bag model using theP-matrix formalism. Data of existing phase-shift analyses are employed to calculate theP-matrix for the coupled¹ D ₂(pp) and⁵ S ₂(NΔ) channels in the energy region above the Δ-isobar production threshold. TheP-matrix calculated for the equivalent hadronic bag radiib=1.4?1.5 fm is shown to have a pole in the mass range 2.31–2.34 GeV in agreement with the MIT bag model prediction of theI=1,J ^P =2⁺ 6-quark state with the mass 2.34 GeV. The hadronic shift of this state is shown to be ≈200 MeV; the dibaryon pole of theS-matrix is located at the energy 2.15–2.17 GeV with the width ≈100–200 MeV.     

Uncertainties in estimating <Emphasis Type="Italic">B</Emphasis><Subscript><Emphasis Type="Italic">c</Emphasis></Subscript> hadronic productionand comparisons of the production at TEVATRON and LHC

The uncertainties in estimating the hadronic production of the B _c meson are studied in the framework of the complete approach of perturbative QCD and the gluon-gluon fusion mechanism. Quantitative comparisons of the production at TEVATRON and LHC are made. Considering the detectors at TEVATRON and LHC, we have also estimated the production with proper kinematic cuts. Based on the results, we conclude that the experimental studies of the B _c meson at the two colliders will be complementary and mutually stimulative. We find that as the CM energy is increasing from RUN-I to RUN-II at TEVATRON, the production cross section increases by about .Received: 21 July 2004, Published online: 18 November 2004PACS: 12.38.Bx, 13.85.Ni, 14.40.Nd, 14.40.Lb     

QCD sum rules calculation ofB c decays

Leptonic and semileptonic decay widths of theB _c meson, as well as its mass, are evaluated by QCD sum rules. The possibility of discovering this meson at present and future high energy machines is also discussed.     

Meson-photon transition form factors and resonance cross-sections in e+e− collisions

Meson-photon-photon transition form factors for S-, P-, and D-wave states are calculated, the meson being treated as a non-relativistic heavy-quark-antiquark pair. The full dependence on both photon virtualities is included. Cross-section formulas for charge-conjugation even mesons with J^p = 0⁻, 0⁺, 1⁺, 2⁺, and 2⁻ in electron-positron collisions are presented and numerical results for LEP energies are given. In particular, we find two-photon event rates for χ_c1, η_c(2S), and η_b(1S) within reach of LEP.With minor modifications to incorporate SU(3)-flavour breaking we estimate rates for 18 light mesons as well, based on the observation that their two-photon decay widths agree remarkably well with measured data. Finally we point out that e⁺e⁻ cross sections for 1⁺ states do not vanish at low Q², the Landau-Yang suppression factors of the two-photon cross sections being compensated by the photon propagators.     

TheS 11-P 11 phase shifts of pion-nucleon scattering

TheS ₁₁ andP ₁₁ partial amplitude is calculated using theN/D method. The present calculation differs from the previous ones in the handling of the divergent behavior of the forces due to first-order diagrams, by parameterizing the short-range forces, and in the way of including inelasticity. We obtain the nucleon as a bound state with correct mass and residue and the correctS ₁₁ andP ₁₁ scattering lengths. The calculatedS-wave andP-wave phase shifts and absorption coefficients are in substantial agreement with those from the CERN Theoretical and Almehed-Lovelace phase shift analyses.     

The role of valence quarks in proton fragmentation

Following earlier theoretical and experimental work (Kalinowski et al. [6], Bourquin et al. [7]), baryon production by fragmentation of incident protons in high energy hadron collisions is re-investigated in terms of a fragmentation-recombination mechanism similar to a model proposed by Fukuda and Iso [4]. The multiplicitiesn _f (B) for the various types of baryonsB produced in proton fragmentation are expressed in terms of the probabilitiesa _i fori=0, ..., 3 valence quarks of the incident proton to emerge in the baryonB and 3?i to emerge in mesons (following [7] we suppose that antibaryon production is mostly due to baryon-antibaryon pair production by a mechanism of non-fragmentation type, and this is taken into account in deducingn _f (B) from baryon and antibaryon multiplicity data). The positivity of thea _i is found to impose remarkably narrow constraints on then _f (B) for (meta)stableB, and we find the data to satisfy these constraints. We show furthermore that the data are compatible with uncorrelated behaviour of the valence quarks of the incident proton, each of them having a probability ? 0.6 to emerge in the fragmentation baryonB, and a probability ? 0.4 to emerge in a meson. We also briefly discuss the relation of our analysis to previous work on the recombination model of proton fragmentation and its possible extension to meson fragmentation.