Quark microscopic picture for vector and pseudoscalar mesons in the nucleon and their quasielastic knockout by high-energy electrons

10.1007/s11450-008-3016-1

“…In the previous studies of our group [1][2][3][4][5][6][7], it was shown that, in charged-pion electroproduction, the t-channel pole diagram is dominant at rather high values of the square of the virtual-photon momentum, Q 2 = −q 2 = 1-3 (GeV/c) 2 . This fact made it possible to introduce the concept of quasielastic pion knockout from a nucleon as a development of the concept of the nonrelativistic quasielastic knockout of constituents from nuclei.…”

“…The possibility of extracting the constituent wave function in a composite system-more precisely, the constituent momentum distribution-is a point of paramount importance in this concept. Later, the idea that the t-channel pole diagram is dominant was extended to the case of rho-and omega-meson knockout accompanied by the ρ, ω → π spin-flip transition in the electromagnetic vertex [3,5,7]. This made it possible to extract directly information about the momentum distributions of rho and omega mesons in the nucleon.…”

“…One version of the quark approach relies on the model of a 3 P 0 -wave scalarqq fluctuation [10][11][12][13][14][15][16]. A microscopic technique for projecting the wave function for the q 3 qq multiquark configuration in the nucleon onto channels of the virtual decay of pions, kaons [1,4], and rho mesons [3] was developed on the basis of the 3 P 0 -wave model. The known value of the phenomenological pion-nucleon coupling constant g πN N was used to determine the constant g s of the scalar fluctuation of the QCD vacuum in the 3 P 0wave model [11] and to calculate the pion momentum distributions for the B = N , ∆(1232), N * * 1/2 + (1440), and N * 1/2 -(1535) channels [1,4]; the kaon momentum distributions for the Y = Λ and Σ channels [1]; and the rho-meson momentum distributions for the B = N channel [3].…”

“…A microscopic technique for projecting the wave function for the q 3 qq multiquark configuration in the nucleon onto channels of the virtual decay of pions, kaons [1,4], and rho mesons [3] was developed on the basis of the 3 P 0 -wave model. The known value of the phenomenological pion-nucleon coupling constant g πN N was used to determine the constant g s of the scalar fluctuation of the QCD vacuum in the 3 P 0wave model [11] and to calculate the pion momentum distributions for the B = N , ∆(1232), N * * 1/2 + (1440), and N * 1/2 -(1535) channels [1,4]; the kaon momentum distributions for the Y = Λ and Σ channels [1]; and the rho-meson momentum distributions for the B = N channel [3]. The pion momentum distribution obtained in this way for the B = N channel has a pronounced maximum in the region around |k| ∼ 0.1 GeV/c and agrees fairly well with available experimental data on p(e, e π + )n quasielastic longitudinal cross sections [8], while the longitudinal cross section calculated for quasielastic kaon electroproduction complies with its experimental counterpart [17,18].…”

“…In view of this, we elaborate on the formalism of quasielastic electroknockout, refining its potential and extending it to higher values of |k|. By analogy with previous studies of our group that were devoted to electroknockout reactions involving a t-channel pion and a t-channel rho meson [1][2][3], we include the b 1meson structure of the nucleon in our consideration and calculate the amplitude for a virtual decay in the channel N → N + b 1 , as well as the wave function, the momentum distribution, and the spectroscopic factor in this channel. Also, we determine the coupling constant g b 1 NN В within the microscopic 3 P 0wave model.…”