Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new informa- tion on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion (πN ) TDAs from p ̄ p → e+ e−π0 reaction with the future PANDA ̄ detector at the FAIR facility. At high center- of-mass energy and high invariant mass squared of the lepton pair q 2 , the amplitude of the signal channel p ̄ p → e+ e−π0 admits a QCD factorized description in terms of πN TDAs and nucleon Distribution Am- plitudes (DAs) in the forward and backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring p ̄ p → e+ e−π0 with the PANDA ̄ detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. p ̄ p → π+π− π 0 were performed for the center-of-mass energy squared s = 5 GeV 2 and s = 10 GeV2 , in the kinematic regions 3.0 < q2 < 4.3 GeV2 and 5 < q 2 < 9 GeV2 , respectively, with a neutral pion scattered in the forward or backward cone | cos θπ0 | > 0.5 in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the PANDA ̄ detector will allow to achieve a background rejection factor of 5 · 107 (1 · 107 ) at low (high) q 2 for s = 5 GeV 2, and of 1 · 108 (6 · 106) at low (high) q2 for s = 10 GeV2 , while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 fb−1 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with PANDA ̄ will provide a new test of the perturbative QCD description of a novel class of hard exclusive reactions and will open the possibility of experimentally accessing πN TDAs.

Experimental access to Transition Distribution Amplitudes with the P̄ANDA experiment at FAIR

BIANCONI, Andrea;
2015-01-01

Abstract

Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new informa- tion on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion (πN ) TDAs from p ̄ p → e+ e−π0 reaction with the future PANDA ̄ detector at the FAIR facility. At high center- of-mass energy and high invariant mass squared of the lepton pair q 2 , the amplitude of the signal channel p ̄ p → e+ e−π0 admits a QCD factorized description in terms of πN TDAs and nucleon Distribution Am- plitudes (DAs) in the forward and backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring p ̄ p → e+ e−π0 with the PANDA ̄ detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. p ̄ p → π+π− π 0 were performed for the center-of-mass energy squared s = 5 GeV 2 and s = 10 GeV2 , in the kinematic regions 3.0 < q2 < 4.3 GeV2 and 5 < q 2 < 9 GeV2 , respectively, with a neutral pion scattered in the forward or backward cone | cos θπ0 | > 0.5 in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the PANDA ̄ detector will allow to achieve a background rejection factor of 5 · 107 (1 · 107 ) at low (high) q 2 for s = 5 GeV 2, and of 1 · 108 (6 · 106) at low (high) q2 for s = 10 GeV2 , while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 fb−1 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with PANDA ̄ will provide a new test of the perturbative QCD description of a novel class of hard exclusive reactions and will open the possibility of experimentally accessing πN TDAs.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11379/492552
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