p-d radiative capture and mesonic effects Ingo Sick

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1 /erice07/erice. p-d radiative capture and mesonic effects Ingo Sick 3-body system as ideal test-system for understanding of nuclei exact calculations for ground- and continuum state several independent groups (Bochum, Hannover, Pisa,...) can use for a number of purposes precision test of NN-potentials study role of tensor force and D-state can be emphasized using tensor-polarized deuterons, 1 H( d, γ) 3 He understand contribution of exchange currents can be emphasized by choice of observable close link S-D transition MEC (remember d(e,e ) at threshold) better than 2-body system as more polarization observables accessible test case for 3-body forces (?) importance of relativistic effects similar to d(γ,p)n at 0

2 In energy range below 100MeV capture dominated by E1 transition cross section sin 2 (θ), asymmetry from E1-E2 interference in E1 can include MEC implicitly via Siegert 45MeV 29MeV cross section understood since long time not sensitive to FSI, MEC,... at extreme angles ( 0, 180 ) M1... important

3 Polarization observables much more sensitive shown by pioneering experiment at 30MeV (Jourdan 1986) and early calculation by J. Torre A yy selectively sensitive to 3 He D-state l = λ = 1 component not l=2 continuum, not d D-state S-D transition particularly interesting more advantageous than p(n,γ)d as tensor polarization observables better accessible

4 Energy dependence of A yy goal of recent PSI-measurements provide precision data, as available data poor 30 MeV maximum of A yy 45 MeV zero crossing of A yy most sensitive important: want data at extreme angles where E1 not dominating

5 Recent PSI-experiments d Z d C pol D Q He pol Q TC D d FC 20-30nA beam current (rate limited), 1.5ns pulse width, optimized using d-c scattering mixed polarized d-beam, cycle through 5 polarization states i 1WF, 2SF RF-transitions typical p z =0.25, p zz =0.65 polarization measured with 4 He(d,α)d, A y =0.85, A yy =0.91, ±2% target: 2mm thick liquid H 2 measure A y and A yy over entire angular region Pro memoria: p z =(N N )/Σ N, p zz =(1 3N )/Σ N dσ dω = dσ 0 dω [ p za y p zza yy ]

6 Setup BaF 2 BaF 2 BaF 2 BaF 2 BaF 2 BaF 2 BaF 2 X d LH T TC D 3 He R d Y Z FC large, fast γ-detectors, BaF 2, 16x16x25cm 3 must if want to reach extreme angles, use long+short component measure γ 3 He coincidence to suppress background cross section very small, 50nb, background mb from d-breakup 3 He recoils at very small angle, 0-2 degrees separate 3 He from d-beam using magnet use segmented recoil detector (Pilot-U) measure TOF of 3 He and γ clean identification of capture

7 Results at E d = 29 MeV calculations with only 1-body currents: very good agreement among each other shows that also continuum-description under control large deviations from data

8 Results at E d = 45 MeV calculations with only 1-body currents: very good agreement among each other no similarity to data

9 Theoretical calculations shown Deltuva et al, PRC71(05)54005 Hannover, Lisbon AGS for continuum, CD-Bonn Coulomb, coupled N- (3-body), π, ρ, σ, ω MEC, rel.corr. in Siegert part Marcucci et al, PRC72(05)14001 Pisa, Old Dominion hyperspherical, AV18 + UIX π, ρ, σ, ω MEC consistent with V NN, Coulomb Skibisnski et al, PRC72(05)44002 Bochum, Krakau,.. Faddeev, AV18 + UIX π+ρ MEC consistent with V NN

10 Results at E d = 29 MeV: effect of 2-body currents beyond Siegert significant fraction of MEC not included when using Siegert

11 Calculations with full MEC for A y 29MeV 45MeV great improvement due to MEC

12 Calculations with full MEC for A yy 29MeV 45MeV good agreement with MEC included was wildly off without MEC ( 0.25 at 50deg) differences between theories << effect MEC note problem at 45MeV and large angles (θ > 150 )

13 Calculations with/without 3-body currents A y, 45MeV A yy, 45MeV effect of 3-body currents very small

14 Relativistic effects at 45MeV relativistic corrections of order (p/m) 2 important fix problems in wings of angular distribution even at 45MeV Coulomb not entirely negligible (E cm =15MeV)

15 Role of relativistic effects surprising? remember D(γ,p)n at 0 found by Cambi et al., late seventies show result of Friar et al., PRC30(84)441

16 Conclusions have now precise data for both A y and A yy covering also extreme angles where non-e1 important polarization much more sensitive than cross section dominating S-S amplitude does not contribute A y and A yy have very different sensitivity to physics need both to get full picture good agreement between high-quality calculations MEC very large already at low q in other observables (d(e,e ), F(q) A=3) MEC only large due to S-D interference polarization observables provide excellent testcase Find good agreement between experiment and theory great progress of theory during last years relativistic effects important at extreme angles PhD-students involved with PSI capture experiments: H. Anklin, T. Klechneva