Neutron-Deuteron Breakup:

Transcription

1 Neutron-Deuteron Breakup: A Probe of the Neutron-Neutron Interaction Triangle Universities Nuclear Laboratory (TUNL) T.B. Clegg A.H. Couture A.S. Crowell C.R. Howell J. Deng J.H. Esterline University of Bonn W. von Witsch B. Fallin M.R. Kiser R.A. Macri S. Tajima W. Tornow NC Central University B.J. Crowe III L.C. Cumberbatch D.M. Markoff NC A&T State University R.S. Pedroni Jagellonian University H. Witala August 8, 01 CD 01 1

2 Low-Energy nd Breakup Observables: Sensitive to S-wave NN Interaction nn FSI cross-section measurement: determination of the 1 S 0 nn scattering length (a nn ) n 1 n p Star configuration cross-section measurement: sensitive to the 3 S 1 np interaction What s next? August 8, 01 CD 01

3 The neutron-neutron 1 S 0 Scattering Length 1. Highly sensitive to the nn potential strength V V nn nn ann a nn CD Bonn (l=1.0) a nn = fm r eff =.8 fm H. Witala and W. Glockle, PRC 83, (011).. Limits CSB a CSB a N nn a N pp r 0 -w mixing I 1 H a CSB em I 0 m fm u m d 4MeV G. A. Miller, B. M. K. Nefkens, and I. Slaus, Phys. Rep. 194, 1 (1990) August 8, 01 CD 01 3

4 Measurement of 1 S 0 nn-scattering Length NN ¼ s ¾ t nn ¼ s ¾ t =0 = ¼ s s (1 k 0 s nn a a 4a nn nn nn 4 k r nn ) k a 1 a a a August 8, 01 CD 01 4

5 Results from Kinematically Complete nd Breakup Measurements August 8, 01 CD 01 5

6 - + d n + n + g Determinations of the 1 S 0 a nn Using - + d n + n + g a nn = ± 0.4 ± 0.3 fm C.R. Howell et al., Phys. Lett. B 444, 5 (1998) a nn = ± 0.4 ± 0.3 fm Q. Chen et al., Phys. Rev. C 77, (008) a nn = ± 0.4 ± 0.3 fm B. Gabioud et al., Phys. Lett. B 103, 9 (1981) a nn = ± 0.6 ± 0.3 fm O. Schori et al., Phys. Rev. C 35, 5 (1987) Average: a nn = ± 0.3 ± 0.3 fm a N nn fm (corrected for MMI) Investigation of reducing theoretical error A. Gardestig and D.R. Phillips, Phys. Rev. C 73, (006) Constrains value of a nn with EFT: J. Kirscher and D.R. Phillips, arxiv;nucl-th, v1 N N acsb ann app 18.9 fm 17.3 fm fm August 8, 01 CD 01 6

7 Recent Determination of the 1 S 0 a nn at TUNL nn coincidence technique E n = 13.0 MeV H(d,n) Neutron-Neutron Coincidence Technique (a) active target (C6D1) (b) detection of both FSI neutrons (c) depends on efficiency of two neutron detectors (d) large neutron attenuation corrections (e) account for finite geometry effects (f) absolute cross section normalized to nd elastic scattering a nn = ± 0.7 fm D.E. Gonzalez Trotter et al., Phys. Rev. Lett. 83, 3788 (1999) D.E. Gonzalez Trotter et al., Phys. Rev. C 73, (006) August 8, 01 CD 01 7

8 A Warning Nice value of a nn you got there. It ll be a real shame if something bad would happen to it. August 8, 01 CD 01 8

9 Recoil Setup at University of Bonn E n = 5.3 MeV Recoil Geometry Technique (a) thin target (CD) (b) detect one FSI neutron with recoil proton (c) depends on efficiency of only one neutron detector (d) modest neutron attenuation corrections (e) account for finite geometry effects a nn = -16. ± 0.4 fm, V. Huhn et al., Phys. Rev. C 63, (000) August 8, 01 CD 01 9

10 Results from Kinematically Complete nd Breakup Measurements a nn =.5 ± 0.8 fm 3 SD difference August 8, 01 CD 01 10

11 Experiments Carried in the Tandem Laboratory August 8, 01 CD 01 11

12 Experimental Setup for Recent nd Breakup Experiments at TUNL Cross-section Measurements: nn FSI to determine 1 S 0 nn scattering length two star configurations (space and co-planar) Both experiments use the same technique: neutron source: H(d,n) reaction thin CD foil target detection of proton in coincidence with one neutron normalization using concurrent nd elastic scattering n 1 n nn FSI star p 70 cm neutron detectors CD foil 30 mg/cm charged-particle E-E telescopes neutron beam E scintillator 4.7 mg/cm August 8, 01 CD 01 1

13 charged-particle tof (E-E) Charged-particle ID with PH-vs-TOF deuterons protons electrons scintillator pulse height August 8, 01 CD 01 13

14 E p (MeV) nn FSI: E n0 = 19 MeV q n =51.7 and q p =45.0, f np =180 nn FSI np elastic scattering from CH contaminant np QFS E n (MeV) August 8, 01 CD 01 14

15 E n Spectrum normalized to nd elastic scattering nn coincidence technique (En = 13 MeV) Gonzalez Trotter et al (TUNL 1999) nn FSI np QFS 41 days acquisition E n0 = 19 MeV q n =51.7 and q p =45.0, f np =180 August 8, 01 CD 01 15

16 Analysis c n a nn = ± 0.4 fm a nn (fm) August 8, 01 CD 01 16

17 Summary of Systematic Errors Description Uncertainty a nn (fm) Neutron detector efficiency ±.0% ±0.36 nd elastic scattering cross section ±1.5% ±0.7 nd elastic yields ±0.5% ±0.09 Neutron detector solid angle ±1.0% ±0.18 Proton detector solid angle ±0.8% ±0.15 E n (bin width) ± kev ±0.18 l n (n-detector position error) ±3 mm ±0.09 q p (proton angle alignment error) 0.06 ±0.10 Total uncertainty ±0.56 Results a nn = ± 0. (stat) ± 0.6 (syst) fm present work a nn = -16. ± 0.3 (stat) ± 0.3 (syst) fm Huhn et al. (000 ) a nn = ± 0.1 (stat) ± 0.7 (syst) fm Gonzalez Trotter et al. (006 ) August 8, 01 CD 01 17

18 d 5 /dw 1 dw ds (mb/sr MeV) The Space Star Anomaly n +d n + n + p E n = 13.0 MeV nd data, TUNL 1996 nd data, Erlangen Univ pd data, Univ. Cologne 1991 August 8, 01 CD 01 18

19 The Space Star: NN interaction sensitivity August 8, 01 CD 01 19

20 Previous Space-Star Measurements August 8, 01 CD 01 0

21 New Space and Coplanar Star Measurements E n0 = 16.0 and 19.0 MeV Space Star: q n = 5.0, q p = 5.0 and f np = 10 Coplanar Star: q n = 18.5, q p = 5.0 and f np = 180 Neutron and proton energies were determined by ToF. The ΔE detector was used as TDC start. Timing spectra were calibrated to np and nd elastic scattering. August 8, 01 CD 01 1

22 Measured Particle Energy Spectra for the Space Star Configuration August 8, 01 CD 01

23 nd Elastic Scattering Normalization Deuteron ToF Spectrum Excellent agreement between Monte Carlo and data for high energy deuterons. (χ 1) August 8, 01 CD 01 3

24 Systematic Uncertainties E n0 = 16.0 MeV Source of Uncertainty Estimated Uncertainty Elastic Normalization ±4.0% Background Subtraction ±.0% Solid Angle ±0.3% Detector Efficiency ±3.% Neutron Attenuation ±1.0% Energy Binning ±1.0% Total (SST) ±5.7% Total (CST) ±5.7% Y Y ndbu ndbu sys Y Y nde nde Y Y SBU SBU W Wn n n n n n E En n 1 August 8, 01 CD 01 5

25 Results Present data A.H. Couture et al., PRC 85, (01) (total uncertainty) August 8, 01 CD 01 6

26 Findings and Conclusions Measured 1 S 0 using nd breakup n-p coincidence technique a nn = ± 0.1 (stat) ± 0.7 (syst) fm TUNL (1999, 006 ) a nn = ± 0. (stat) ± 0.6 (syst) fm present work a nn = -16. ± 0.3 (stat) ± 0.3 (syst) fm Bonn (000 ) This new a nn value suggests an energy and geometry dependence in a nn from nd breakup The effective 1 S 0 interaction in the nd system differs from potenial models. Measured cross sections for the space and co-planar star configurations in nd breakup at 16 and 19 MeV using the n-p coincidence technique. The new space-star cross-section data are about 35% larger than theory and the co-planar star data are about 35% below theory. August 8, 01 CD 01 7

27 What s next? Measured 1 S 0 using nd breakup n-p coincidence technique a nn = ± 0.1 (stat) ± 0.7 (syst) fm TUNL (1999, 006 ) a nn = ± 0. (stat) ± 0.6 (syst) fm present work a nn = -16. ± 0.3 (stat) ± 0.3 (syst) fm Bonn (000 ) This new a nn value suggests an energy and geometry dependence in a nn from nd breakup The effective 1 S 0 interaction in the nd system differs from potenial models. Measured cross sections for the space and co-planar star configurations in nd breakup at 16 and 19 MeV using the n-p coincidence technique. The new space-star cross-section data are about 35% larger than theory and the co-planar star data are about 35% below theory. August 8, 01 CD 01 8

28 1. QFS np QFS W. von Witsch et al. (Bonn) E n =6 MeV nn-qfs H(n,nn)p August 8, 01 CD 01 9

29 Proposed experimental setup Pulsed Deuteron Beam Deuterium Gas Cell Transmission Foil Detector CD Target Proton Recoil Telescope Proton Detector C 6 D 1 Target Neutron Detector Neutron Detector Neutron Detector Neutron Beam Collimator & Shielding Wall 1.5 m np QFS setup nn QFS setup August 8, 01 CD 01 30

30 Photodisintegration of 3 He and 3 H At HIgS with Radial Time Projection Chamber Developing proposal for submission to the 01 HIgS PAC August 8, 01 CD 01 31

31 Backup Slides August 8, 01 CD 01 3