Quark Combinatorics Research Articles

Production of strange secondaries in high-energy Σ− A collisions

We describe the WA89 Collaboration experimental data on Lambda, Sigma(-), Sigma(+), Xi(-), and Omega(-) baryons, and bar(Lambda) and bar(Xi(+)) antibaryons production in Sigma(-) collisions with C and Cu targets at 345 GeV/c (sqrt(s_(Sigma N)) ~ 25.5 GeV) in the frame of the Quark-Gluon String Model. How the theoretical results compare to the experimental data is discussed. Finally, some relations among the values of the model parameters obtained with the help of quark combinatorics are presented.

Observation of the tensor glueball

In the reactions p-p → π0π0, ηη, ηη′, in the mass region 1900–2400 MeV there are four relatively narrow resonances f2(1920), f2(2020), f2(2240), and f2(2300) and a broad one f2(2000). In the framework of quark combinatorics, we carry out an analysis of the decay constants for all five resonances. It is shown that the relations for the decay constants corresponding to the broad resonance f2(2000) → π0π0, ηη, ηη′ are the same as those corresponding to a glueball. An additional argument in favor of the glueball nature of f2(2000) is the fact that f2(1920), f2(2020), f2(2240), and f2(2300) fit well the q-q trajectories in the (n, M2) plane (where n is the radial quantum number), while the broad f2(2000) resonance turns out to be an unnecessary extra state for these trajectories.

QUARK STRUCTURE OF HADRONS AND HIGH ENERGY COLLISIONS

The additive quark model is one of the simplest and oldest models for the description of soft processes at high energies, and it still works. We present here a review of this model and verify the rules of quark combinatorics following from it in hadronic Z0 decays.

Comparing fragmentation of strange quark in Z0 decays and K+p reactions

The ratios of the production rates K∗0(892)/K, φ/K, ρ0/π, ω/π, Δ++(1232)/p, Σ∗+(1385)/Λ, Ξ−/Λ and their xp-dependence obtained from results of the LEP and SLD experiments in Z0 hadronic decays are analyzed. The corresponding ratios for promptly produced mesons are estimated at xp→1. A comparison of the LEP results with those from the Mirabelle and BEBC K+p experiments at 32 and 70 GeV/c shows striking similarity in fragmentation of the s̄ valence quark of the incident K+ and strange quarks produced in Z0 decays. The JETSET model describes the LEP, Mirabelle and BEBC results. The model of Pei is consistent with the data for mesons, but presumably underestimates the fractions of primary octet baryons. The quark combinatorics model of Anisovich et al. is incompatible with the data.

Quark combinatorics and meson-production ratios in hadronic Z 0 decays

A vast body of experimental data accumulated in the past few years in hadronic Z 0 decays allows one to check quark-combinatorics relations for a new type of processes-namely, quark jets in the decays Z 0 → \(q\bar q\) → hadrons. In this paper, we review quark-combinatorics rules for the yields of vector and pseudoscalar mesons, V/P, in the central and fragmentation regions of hadronic Z 0 decays. It is emphasized that, in the central region, a direct verification of quark-combinatorics rules is rather problematic because of a considerable background associated with the decay of highly excited resonances; however, such a verification is possible in the fragmentation region, at x hadron∼0.5–1, where the contribution of resonance decays is suppressed owing to a fast decrease of the spectra with increasing x hadron. It is shown that, in the fragmentation region, experimental data on ρ0/π0 and p/π+ are in reasonable agreement with the predictions of quark combinatorics. The ratios of the heavy-meson yields, B*/B and D*/D, are also discussed: the data demonstrate good agreement with the quark combinatorial results. We analyze the structure of the suppression parameters for strange-and heavy-quark production in soft processes and estimate their orders of magnitude in multiperipheral processes; the ratio K ±/π± at x hadron∼0.5–0.8 and the production probabilities for \(c\bar c\) and \(b\bar b\) mesons are in good agreement with the estimates.

Vector-to-pseudoscalar and meson-to-baryon ratios in hadronic Z decays at LEP

Mass ( M) dependences of the total production rates per hadronic Z decay of all light-flavour hadrons measured so far at LEP were extrapolated to the point M=0 using the phenomenological laws of hadron production related to the spin, isospin, strangeness and mass of the particles. The vector-to-pseudoscalar and meson-to-baryon ratios at M=0 were found to be: ρ +/ 3 π +=1.2 ± 0.3 and π +/ p=2.8 ± 0.3 . They agree with predictions of the quark combinatorics model.

Energy dependence of single-hadron multiplicities in pp interaction and quark combinatorics

Multiplicities of different hadrons produced in pp reactions are computed by means of quark combinatorics. The number of negative hadrons is used as a measure of the incident energy. Both total multiplicities of non-strange long-lived secondaries and the production branching ratios in the central region agree with experiment. Predictions of the model for resonances from the 36 and 56 and for A hyperons are overestimated by a factor of 2–3, partly because we account only for the states with zero total orbital momentum in q q ¯ , qqq or q q q ¯ systems. The shape of the energy dependence is reproduced correctly in all cases.