Color transparency inπ−-induced dilepton production on nuclei

Abstract

We argue that the observation of the color transparency effect in the semiexclusiveprocess is important for determining whether it is possible to extract the generalized parton distributions of the nucleon from the elementary reaction π − p → l + l − n at p lab = 15 − 20 GeV/c at small |t| and large invariant mass of the dilepton pair l + l − . Assuming that the transverse size of the pionic qq pair in the hard interaction point is similar to the one in the reaction γ * p → π + n studied at JLab we predict large color transparency effects in the discussed kinematic range. We also suggest that the semiexclusive ρ 0 production in π − -induced reactions in the same beam momentum region may provide new information on the dynamics of the interaction in the non-vacuum channel, while the J/ψ production can be used to get information on J/ψN total interaction cross section.

Nuclear transparency of the charged hadron produced in the inclusive electronuclear reaction

“…The calculated results due to GM+CT (i.e., πCT) are accord with both the Q 2 dependence and magnitude of the data. This is in concurrence with the earlier calculations [4,17]. The calculated T A (π + ) due to GM+SRC do not describe the Q 2 dependence of the data but the calculated results agree with the large number of data points within the errors.…”

“…According to Quantum Chromodynamics, a color neutral PLC has reduced interaction with the nucleon in the nucleus because the sum of its gluon emission amplitudes cancel [1,3]. The PLC expands to the size of physical hadron, as it moves up to a length (∼ 1 fm) called hadron formation length l h [1,4]:…”

“…Cosyn et al, [19] studied the effects of πCT and nucleon short-range correlation in the pion photo-and electro-production from nuclei. Larionov et al, [4] estimated the πCT in the (π − , l + l − ) reaction on nuclei for p π = 5 − 20 GeV/c, which can be measured at the forth-coming facilities in Japan Proton Accelerator Research Complex (J-PARC) [20]. This reaction provides the informations complementary to those obtained from the A(γ * , π) reaction.…”

Exploring QCD dynamics in medium energy γA semiexclusive collisions

“…The calculations are performed with the two values, ∆M 2 = 0.7 GeV 2 and 1.1 GeV 2 . The value of 0.7 GeV 2 is favored by the analyses [21,22] of the nuclear transparency in A(e, e ′ π + ) reaction in the collinear kinematics measured at TJNAF [23]. The value of 1.1 GeV 2 is close to the difference of masses squared of a N (1440) resonance and a nucleon.…”

Color Transparency and Hadron Formation Effects in High-Energy Reactions on Nuclei

“…The selection of the exclusive transition π − p → l + l − n in the nucleus can be done either by restricting the longitudinal momentum transfer q z for fixed q t and M 2 l + l − [26] or directly applying the missing mass method [25]. Figure 2 shows the transparency for the pionic Drell-Yan process as a function of p lab .…”