Search for d' in pion inclusive spectra from pp-interactions

We report on our measurement of the inclusive spectrum of positive pions from the reaction pp→π⁺+X on a CH ₂ internal target of the ITEP proton synchrotron at 1.5 GeV/c with a missing mass resolution of about 1 MeV/c². The goal of our experiment was the search for the hypothetical narrow πNN resonance (0.5\ MeV/c² width and a mass of 2.06\ GeV/c²) with I(J ^P P)=even(0⁻), called d′. We do not see any statistically significant d′-signal. The upper limit for d′ production cross-section in pp-interactions is near 2μb at 84%C.L. Received: 5 November 1997     

Chiral phenomenological relations between rates of rare radiative decays of kaon to pion and leptons and the meson form factors

In the framework of the chiral perturbation theory we obtain the phenomenological relations between decay branches of rare radiative kaon to pion and leptons K ⁺ → π⁺ l ⁺ l ⁻ and K _S ⁰ → π⁰ l ⁺ l ⁻ and meson form factors. The comparison of these results with the present-day experimental data shows us that the ChPT relations for a charge kaon can determine meson form factors from already measured decay rates at high precision level. However, in the case of the neutral kaon decays K ⁰ → π⁰ e ⁺ e ⁻(μ⁺μ⁻) the form factor data are known to a higher precision than data on the differential rates of radiative kaon decay K ⁰ π⁰ e ⁺ e ⁻(μ⁺μ⁻).     

Measurements of inclusive pion electroproduction

Measurements of the inclusive pion electroproduction reaction e^?+p → e^?+π^±+X made at the Wilson Synchrotron Laboratory are reported. Data were taken at points with nominal (Q², W) values of (0.6, 2.67), (1.2, 2.67), (2.0, 2.67) and (1.2, 2.15) in (GeV², GeV). A more complete angular distribution was taken at (1.2, 2.67). The virtual photoproduction cross section for π⁺ + missing mass is studied as a function of missing mass, Feynman scaling variables, Q² and W. The invariant cross section show a simple behavior as a function of Q² and W. Its dependenc on P_⊥², x′ and φ is determined.     

Determination of neutral current couplings from neutrino-induced semi-inclusive pion and inclusive reactions

We show that by looking at data from neutrino-induced semi-inclusive pion and inclusive reactions on isoscalar targets alone, one can determine completely the neutral current couplings. Predictions for various models are also presented.     

Revealing pion and kaon structure via generalised parton distributions

Clear windows onto emergent hadron mass(EHM)and modulations thereof by Higgs boson interactions are provided by observable measures of pion and kaon structure,many of which are accessible via generalised parton distributions(GPDs).Beginning with algebraic GPD Ans?tze,constrained entirely by hadron-scaleπand K valence-parton distribution functions(DFs),in whose forms both EHM and Higgs boson influences are manifest,numerous illustrations are provided.They include the properties of electromagnetic form factors,impact parameter space GPDs,gravitational form factors and associated pressure profiles,and the character and consequences of allorders evolution.The analyses predict that mass-squared gravitational form factors are stiffer than electromagnetic form factors;reveal that K pressure profiles are tighter than profiles,with both mesons sustaining near-core pressures at magnitudes similar to that expected at the core of neutron stars;deliver parameter-free predictions for and K valence,glue,and sea GPDs at the resolving scale l=2GeV;and predict that at this scale the fraction of meson mass-squared carried by glue and sea combined matches that lodged with the valence degrees-of-freedom,with a similar statement holding for mass-squared radii.     

Exploring light-cone sum rules for pion and kaon form factors

We analyze the higher-twist effects and the SU(3)-flavor symmetry breaking in the correlation functions used to calculate form factors of pseudoscalar mesons in the QCD light-cone sum rule approach. It is shown that the Ward identities for these correlation functions yield relations between twist-4 two- and three-particle distribution amplitudes. In addition to the relations already obtained from the QCD equations of motions, we have found a new one. With the help of these relations, the twist-4 contribution to the light-cone sum rule for the pion electromagnetic form factor is reduced to a very simple form. Simultaneously, we correct a sign error in an earlier calculation. The updated light-cone sum rule prediction for the pion form factor at intermediate momentum transfers is compared with the recent Jefferson Lab data. Furthermore, from the correlation functions with strange-quark currents the kaon electromagnetic form factor and the weak transition form factors are predicted with accuracy. Received: 30 June 2002 / Published online: 7 October 2002 RID="a"     

A study of inclusive vector meson production

Data are presented on the reactions π⁺n → ?⁰+X and $\text{K}{}^{\mathrm{?}}\text{p}\text{→}\text{K}{}^1\text{0}\text{(890)+}\text{X}\text{at 6.0}\text{and}\text{7.3}\text{GeV}\text{/c}$, respectively. Comparisons are made with related reactions at higher energies.     

Contributions of exclusive pion electroproduction reactions to inclusive structure functions

The contributions of exclusive π⁺n, π⁰p, and π^?π⁺p channels to the inclusive structure function F ₂(x, Q ²) are determined from the CLAS collaboration data analysis. Reliability of the CLAS data on the inclusive structure function and single-pion electroproduction channels is verified. The total contribution of the uninvestigated π⁺π⁰n and π⁰p channels to this function and the integrated cross sections of these channels at photon virtualities Q ² = 0.4 and 0.5 GeV² are predicted.     

Effects of meson exchange currents on pion absorption

The effect of the π exchange current on the pion absorption process π⁺ + d → p + p has been investigated. The absorption cross section is significantly enhanced particularly in the energy region above the 33 resonance.     

Absorptive corrections and pion-exchange contributions to inclusive reactions

Pion-exchange contributions to inclusive reactions in the fragmentation domain are discussed and the importance of introducing absorptive corrections is stressed. An explicit model which incorporates the absorptive two-body correction is suggested and its experimental implications are examined.     

Applying Bayesian neural networks to identify pion, kaon and proton in BES Ⅱ

The Monte-Carlo samples of pion, kaon and proton generated from 0.3 GeV/c to 1.2 GeV/c by the 'tester' generator from SIMBES which are used to simulate the detector of BES Ⅱ are identified with the Bayesian neural networks (BNN). The pion identification and misidentification efficiencies are obviously better at high momentum region using BNN than the methods of X2 analysis of dE/dX and TOF information.The kaon identification and misidentification efficiencies are obviously better from 0.3 GeV/c to 1.2 GeV/c using BNN than the methods of X2 analysis. The proton identification and misidentification efficiencies using BNN are basically consistent with the ones of X2 analysis. The anti-proton identification and misidentification efficiencies are better below 0.6 GeV/c using BNN than the methods of X2 analysis.     

A dependence of inclusive pion double charge exchange

The A dependence of the forward cross section for inclusive pion double charge exchange on nine target nuclei from ⁶Li to ²⁰⁹Bi at T₀ = 0.59 GeV, as well as the cross section for ⁶Li, ⁷Li, and ¹²C nuclei at T₀ = 0.59, 0.75, and 1.1 GeV, was measured with the 3-m magnetic spectrometer of the Institute of Theoretical and Experimental Physics (ITEP, Moscow). The resulting A dependence is well described within the model involving two sequential single charge exchanges and taking into account the renormalization of the amplitude for pion single charge exchange in a nucleus. A relatively weak energy dependence of the cross section for the ⁶Li, ⁷Li, and ¹²C nuclei agrees with the analogous dependence obtained previously for the ¹⁶O nucleus, but it contradicts the predicted sharp decrease in the cross section within the model involving two sequential single charge exchanges. This result provides an additional piece of evidence that the contribution from the mechanism of inelastic Glauber rescattering is significant at T₀ ? 0.6 GeV.     

Fermi sea effects on pion and kaon properties in the Nambu-Jona-Lasinio model

We study modifications of hadronic properties in dense nuclear and neutron matter, in the context of a generalized three-flavor Nambu-Jona-Lasinio model, focussing mainly on Fermi sea effects. In symmetric nuclear matter, we observe the splitting between K^± and the occurrence of a low-lying K⁻ branch at baryonic densities around 0.4 times normal nuclear matter density ϱ₀. This branch is not significantly affected by the inclusion of strange matter in the medium while the flavor asymmetry is preserved. A similar π⁺ branch is found in neutron matter at neutron densities around 0.3ϱ₀. These low-lying modes are particle-hole excitations of the Fermi sea and decrease smoothly with density. In any case, the vacuum does not exhibit signs of instability associated with boson condensation.     

Sivers effect for pion and kaon production in semi-inclusive deep inelastic scattering

We study the Sivers effect in the transverse single spin asymmetries (SSA) for pion and kaon production in semi-inclusive deep inelastic scattering (SIDIS) processes. We perform a fit of which, by including recent high-statistics experimental data for pion and kaon production from HERMES and COMPASS Collaborations, allows a new determination of the Sivers distribution functions for quarks and antiquarks with u , d and s flavours. Estimates for forthcoming SIDIS experiments at COMPASS and JLab are given.     

Determination of vector meson properties by matching resonance saturation to a constituent quark model

The properties of mesonic resonances can be calculated in terms of the low-energy coefficients of chiral perturbation theory ( PT) by extending unitarized PT to higher energies. On the other hand, these low-energy coefficients can be calculated in two different models, namely i) by assuming resonance saturation and ii) within a constituent quark model. By matching the expressions of the two models combined with the results of unitarized PT and the Weinberg sum rules, the properties of vector and axial-vector mesons can be calculated in the combined large-N _c and chiral limit.Received: 30 September 2002, Published online: 22 October 2003PACS: 12.39.Fe Phenomenological quark models: Chiral Lagrangians - 14.40.Cs Properties of specific particles: Other mesons with S = C = 0, mass < 2.5 GeV