Threshold pion electroproduction at large momentum transfers

Abstract

We consider pion electroproduction close to threshold for Q 2 in the region 1 − 10 GeV 2 on a nucleon target. The momentum transfer dependence of the S-wave multipoles at threshold, E0+ and L0+, is calculated in the chiral limit using light-cone sum rules. Predictions for the cross sections in the threshold region are given taking into account P-wave contributions that, as we argue, are model independent to a large extent. The results are compared with the SLAC E136 data on the structure function F2(W, Q 2 ) in the threshold region.

Consistent model forπNtransition distribution amplitudes and backward pion electroproduction

“…As argued in [34,35], this allows us to express πN GDAs at the threshold in terms of the nucleon DAs V p , A p and T p . In the chiral limit, the soft-pion theorem for GDAs also constrains πN TDAs similarly to the way [36] the soft-pion theorem [32] for 2π GDAs in the chiral limit links the isovector pion GPD at ξ = 1, ∆ 2 = 0 to the pion DA ϕ π .…”

Threshold pion electroproduction at large momentum transfers

“…[2] for the details. In particular we use the parametrisation of the proton magnetic form factor from [18] and for the neutron magnetic form factor from [19].…”

“…In Refs. [1,2] the G 1 and G 2 form factors were estimated in the LCSR approach for the range of momentum transfers Q 2 2 10 GeV 2 . A new technical element in these calculations is taking into account the semidisconnected pion-nucleon contributions in the intermediate state.…”

PANIC08. Proceedings of the eighteenth Particles and Nuclei International Conference

“…In order to minimise the dependence of various parameters one may use the LCSRs to predict certain form factor ratios only, and then normalise to the electromagnetic nucleon form factors as measured in the experiment, see [2] for the details. The results are shown by the solid curves in Fig.…”

“…Pion electroproduction at threshold from a proton target, e(l)+p(P ) → e(l ′ )+π + (k)+ n(P ′ ) and e(l)+p(P ) → e(l ′ )+π 0 (k)+p(P ′ ), can be described in terms of two generalised form factors [1,2] N (P ′ )π(k)|j em µ (0)|p(P ) = (1)…”