Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle Munich, June 13 th 2011 XIV International Conference on Hadron Spectroscopy 2 Collaboration a
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Outline 1 Motivation 2 Single π 0 Photoproduction Status Experiment Results 3 Double π 0 Photoproduction Total Cross Sections Beam-Helicity Asymmetry 4 Conclusions Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions � Why Photoproduction of π 0 ? ◮ Test modern hadron models by studying nucleon resonances N ( J P N ( J P N ) N ) N ∗ ( J P N ∗ ) � � � π 0 ( L P γ ( L P γ ) π 0 ) ◮ Small coupling of photons to neutral mesons Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions � Why Photoproduction of π 0 ? ◮ Test modern hadron models by studying nucleon resonances N ( J P N ( J P N ) N ) N ∗ ( J P N ∗ ) � � � π 0 ( L P γ ( L P γ ) π 0 ) ◮ Small coupling of photons to neutral mesons Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Why on the Neutron? ◮ Isospin amplitudes of the elm. transitions depend on reactions on proton and neutron √ 2( A (0) + A ( − ) ) A ( γ p → π + n ) = √ 2( A (0) − A ( − ) ) A (0) := isoscalar A ( γ n → π − p ) = A ( γ p → π 0 p ) = ( A (+) + A (0) ) A (+) , A ( − ) := isovector A ( γ n → π 0 n ) = ( A (+) − A (0) ) ◮ meson photoproduction from light nuclei, i.e. deuteron ◮ nuclear effects (rescattering of the mesons, FSI, ...) Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions World π 0 Data γ p → p π o γ n → n π o 2 1.5 E γ [ GeV ] 1 0.5 0 -1 0 1 -1 0 1 cos( Θ π ) SAID Data Base - http://gwdac.phys.gwu.edu/ Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Former Results - MAMI 1999 x10 2 σ ( π 0 np ) / A 0.5 ● σ ( π 0 d ) / A 3 0.4 σ ( π 0 p ) � 0.3 σ /A [µ b ] 2 σ ( π 0 p ) folded 0.2 500 600 700 800 γ p →π o p 1 γ d →π o np ◮ significant reduction in σ/ A γ d →π o d compared to free proton ◮ can not be explained alone by 0 Fermi motion 200 400 600 800 photon energy [ MeV ] ◮ nuclear effect? FSI? B. Krusche et al., Eur. Phys. J. A 6(1999) 309 Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Former Results - LNS Sendai 2009 σ ′ ( − 0 . 7 < cos θ ∗ π 0 < 0 . 6) σ ( π 0 np ) ● σ ( π 0 p ) � σ ( π 0 n ) = σ ( π 0 np ) − σ ( π 0 p ) △ 0 . 8 ∗ MAID folded ◮ can not be explained alone by Fermi motion ◮ nuclear effect? FSI? H. Shimizu, NNR workshop 2009 Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Experiment MAinzer MIcrotron, Dec 2007 ◮ Photon beam energies up to ∼ 1 . 4 GeV ◮ Target: ∼ 5 cm LD 2 ◮ Detectors: ◮ Crystal Ball ( CB ): ◮ surrounding the target ◮ Two Arm Photon Spectrometer ( TAPS ): ◮ placed as forward wall ◮ ∼ 4 π steradian Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Identification of the Reaction Channels Reaction mechanism for π 0 photoproduction on deuterium: π 0 + p ( n ) QF on proton π 0 + n ( p ) QF on neutron γ + d → E γ > 500 MeV π 0 + d Coherent ( 0) − → Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Identification of the Reaction Channels Reaction mechanism for π 0 photoproduction on deuterium: π 0 + p ( n ) QF on proton π 0 + n ( p ) QF on neutron γ + d → E γ > 500 MeV π 0 + d Coherent ( 0) − → Measurements: γ + d → π 0 + p Exclusive on P: γ + d → π 0 + n + Exclusive on N: γ + d → π 0 + ( N ) QF-Inclusive: ≈ Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions π 0 Total Cross Sections PRELIMINARY 80 σ π 0 ( p) 70 σ π 0 ( n) 60 MAID folded 50 SAID folded b] µ 40 [ σ 30 20 10 0 400 600 800 1000 1200 1400 E [MeV] γ Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions π 0 Total Cross Sections PRELIMINARY PRELIMINARY 80 140 σ π 0 σ π 0 ( np) ( p) 70 σ π σ π 0 0 ( n) + ( p) 120 σ π 0 ( n) 60 σ π 0 ( np) B. Krusche et al. MAID folded 100 50 MAID folded SAID folded b] b] SAID folded 80 µ µ 40 [ [ σ σ 60 30 40 20 20 10 0 0 400 600 800 1000 1200 1400 400 600 800 1000 1200 1400 E [MeV] E [MeV] γ γ Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Comparison to Models PRELIMINARY 60 σ π 0 ( p) σ π 0 50 ( n) σ π 0 ( np) 0.8*MAID folded 40 0.8*SAID folded b] MAID and SAID model µ 30 [ scaled down with factor σ 0 . 8 20 10 0 600 700 800 900 1000 110012001300 1400 E [MeV] γ Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Resonance Contributions Contributions Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Resonance Contributions D 13 : p,n Contributions Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Resonance Contributions D 13 : p,n Contributions F 15 : p Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Resonance Contributions D 13 : p,n Contributions F 15 : p D 15 : n Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions 2 π 0 Total Cross Sections (M. Oberle et al.) Dominated by sequential decay PRELIMINARY N * (I=1/2) π ∆ (1232) ρ σ π N(938) Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Resonance Contributions p ( γ, 2 π 0 ) p n ( γ, 2 π 0 ) n ◮ Electromagnetic excitation ◮ Electromagnetic excitation of the F 15 stronger on the of the D 15 stronger on the proton neutron Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions The Beam-Helicity Asymmetry Helicity h = � S ˆ P = − S , ..., S d σ + − d σ − N + − N − 1 1 I ⊙ (Φ) = d σ + + d σ − = N + + N − P γ P γ Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Former Results (D. Krambrich, F. Zehr et al.) � Data ◮ Asymmetry indicates strong Fit to Data sensitivity to reaction mechanisms Fix and Arenh¨ ovel model ◮ Early results contradicted many Roca model predictions BoGa model D. Krambrich, F. Zehr et al., Phys. Rev. Lett. 103 (2009) 052002 Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Helicity Asymmetries for 2 π 0 (M. Oberle et al.) PRELIMINARY p ( γ, 2 π 0 ) p n ( γ, 2 π 0 ) n p ( γ, 2 π 0 ) p Fermi defolded compared to free p (F.Zehr et al.) Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Single π 0 Photoproduction Double π 0 Photoproduction Outline Motivation Conclusions Conclusions Single π 0 Photoproduction: ◮ Cross Sections for Single π 0 in good agreement with former results ◮ MAID/SAID overestimate the cross sections by 25% ◮ Reduction can not only be explained by Fermi motion Double π 0 Photoproduction: ◮ Same asymmetries for 2 π 0 on the proton as on the neutron ◮ Model predictions not yet in agreement with results, further input needed ◮ Electromagnetic excitation of the resonances different for proton and neutron. De-excitation of the resonances different for single and double pion production. Single and Double Pion Photoproduction off the Deuteron Manuel Dieterle
Recommend
More recommend
