1. U. Kentucky, 31 March 2005 BLAST: A Detector for Internal Target Experiments  Introduction ¶ Overview and status of the Program ¶ Present Results ¶ Outlook John Calarco, UNH and UT U. Kentucky, 31 March 2005

2. BLAST COLLABORATION R. Alarcon, E. Geis, J. Prince, B. Tonguc, A. Young Arizona State University, Tempe, AZ 85287 J. Althouse, C. D ’ Andrea, A. Goodhue, J. Pavel, T. Smith, Dartmouth College, Dartmouth, NH D. Dutta, H. Gao, W. Xu Duke University Durham, NC 27708-0305 H. Arenh ö vel, Johannes Gutenberg-Universit ä t, Mainz, Germany T. Akdogan, W. Bertozzi, T. Botto, M. Chtangeev, B. Clasie, C. Crawford, A. Degrush, K. Dow, M. Farkhondeh, W. Franklin, S. Gilad, D. Hasell, E. Ilhoff, J. Kelsey, M. Kohl, H. Kolster, A. Maschinot, J. Matthews, N. Meitanis, R. Milner, R. Redwine, J. Seely, S. Sobczynski, C. Tschalaer, E. Tsentalovich, W. Turchinetz, Y. Xiao, C. Zhang, V. Ziskin, T. Zwart Massachusetts Institute of Technology, Cambridge, MA 02139 and Bates Linear Accelerator Center, Middleton, MA 01949 J. Calarco, W. Hersman, M. Holtrop, O. Filoti, P. Karpius, A. Sindile, T. Lee University of New Hampshire, Durham, NH 03824 J. Rapaport Ohio University, Athens, OH 45701 K. McIlhany, A. Mosser United States Naval Academy, Annapolis, MD 21402 J. F. J. van den Brand, H. J. Bulten, H. R. Poolman Vrije Universitaet and NIKHEF, Amsterdam, The Netherlands W. Haeberli, T. Wise University of Wisconsin, Madison, WI 53706

3. U. Kentucky, 31 March 2005 Approved BLAST Scientific Program Form Factor Measurements: Q 2  1.0 (GeV/c) 2 Proton Charge and Magnetism Elastic Scattering with Polarized Beam and H Target (01-01) Neutron Charge and Magnetism and Deuteron Electromagnetic Structure Quasi-elastic Scattering with Polarized Beam and D Target (89-12 and 91-09) Elastic scattering off Tensor and Vector Polarized Deuterium (00-03 and 03-02)

4. U. Kentucky, 31 March 2005 General Kinematics for Polarized e Scattering on a Polarized Target

5. U. Kentucky, 31 March 2005 Bates Linac  500MeV Linac recirculated to reach up to 1GeV  Inject into South Hall Ring  Polarization maintained by Siberian snakes  Polarization monitored real time by Compton Polarimeter  Internal Target located in the ring vacuum

6. U. Kentucky, 31 March 2005 Left-right symmetric detector –simultaneous parallel and perpendicular asymmetry determination Large acceptance –covers 0.1GeV 2 ≤ Q 2 ≤ 1GeV 2 –out-of-plane measurements DRIFT CHAMBERS –momentum determination, particle identification CERENKOV COUNTERS –electron/pion discrimination SCINTILLATORS –TOF, particle identification NEUTRON COUNTERS –neutron determination MAGNETIC COILS –3.8kG toroidal field The BLAST Spectrometer DRIFT CHAMBERS CERENKOV COUNTERS SCINTILLATORS NEUTRON COUNTERS TARGET BEAM

7. U. Kentucky, 31 March 2005 BLAST: Present Configuration

8. U. Kentucky, 31 March 2005 Detector Performance All detectors operating at or near designed level –Drift chambers ~98% efficient per wire –TOF resolution of 300ps Clean event selection –Cerenkov counters 85% efficient in electron/pion discrimination –Neutron counters 10% (25-30%) efficient in left (right) sectors To be improved further Reconstruction resolutions good but still being improved currentgoal pp 3%2%  0.5°0.3°  0.5°0.5º zz 1cm

9. U. Kentucky, 31 March 2005

10. ep Elastic Kinematic Correlation

11. U. Kentucky, 31 March 2005 Asymmetries A L and A R

12. U. Kentucky, 31 March 2005  G E /G M from ep Elastic

13. U. Kentucky, 31 March 2005  G E /G M Comparison between BLAST and JLab

14. U. Kentucky, 31 March 2005 Inclusive H(e,e’) Cross Sections  TL  TT from MC

15. U. Kentucky, 31 March 2005 Inclusive H(e,e’) Cross Sections from Data

16. U. Kentucky, 31 March 2005 Motivation I: Why Deuteron N-N Interaction Deuteron as test-bed for N-N interaction models THE 2-nucleon bound state D-wave admixture … Tensor force Model predictions vary from 4% to 7% Deuteron as neutron target understand Deuteron structure

17. U. Kentucky, 31 March 2005 Loosely-bound deuterium readily breaks up electromagnetically into two nucleons –e + d  e’ + p + n Most generally, the cross section can be written as : In the Born approximation, vanishes in the L = 0 model for the deuteron (i.e. no L = 2 admixture) –Measure of L = 2 contribution and thus tensor NN component –Reaction mechanism effects (MEC, IC, RC) convoluted with tensor contribution “There is no direct measure of the tensor component.” -- somebody provides a measure of reaction mechanisms Useful for extraction of G n e Beam-vector dilution (hPz) gotten from analysis Deuteron Electrodisintegration

18. U. Kentucky, 31 March 2005 Beam and Target Performance Beam fills to 175mA with 25min lifetime, average polarization = 65% ± 4% Deuterium polarization in tri-state mode –(Vector, Tensor) : (-P z, +P zz ) ( +P z, +P zz ) (0, -2P zz ) Flow = 2.2  10 16 atoms/s, Density = 6.0  10 13 atoms/cm 2 Luminosity = 4.0  10 31 /cm 2 /s @ 140mA Target polarizations from data analysis: P z = 88% ± 4%, P zz = 65% ± 2%

19. U. Kentucky, 31 March 2005 Motivation II: Why T 20 e-d elastic scattering: G C G M G Q G Q > D-state > Tensor Force Rosenbluth Separation 3 rd Measurement to separate 3 form factors Tensor Asymmetry in e-d elastic scattering

20. U. Kentucky, 31 March 2005 e-d Elastic Event Selection  Timing Cuts  Coplanarity:   =1 o Need clean e-d elastic sample e-d Elastic rate ~ 3% of coincident rate by one positive and one negative charge scattered into either sector. Everything Colpanarity Kinematics Full cuts

21. U. Kentucky, 31 March 2005  Kinematics:  p e =24MeV   d =1 o …  Mass: timing & tracking Blue: everything Red: after coplanary cut Deuterons Protons  + ? e-d Elastic Event Selection e - left, d + right e - right, d + left

22. U. Kentucky, 31 March 2005 Preliminary T20 Result

23. U. Kentucky, 31 March 2005 From Measurements of the Elastic Vector Asymmetry A V ed

24. U. Kentucky, 31 March 2005 Deuterium Wave Functions The NN interaction conserves only total angular momentum Spin-1 nucleus lies in an L = 0, 2 admixture ground state: A tensor component must be present to allow  L = 2 Fourier transform into momentum space: L = 2 component becomes dominant at p M ~ 0.3GeV (Bonn Potential)

25. U. Kentucky, 31 March 2005 Deuteron Density Functions Calculate the density functions: One-to-one correspondence between m d and the (P Z,P ZZ ) polarization states: In the absence of a tensor NN component, these plots are spherical and identical Famous “donut” and “dumbbell” shapes P ZZ PZPZ (-1,+1)(+1,+1) (0,-2)

26. U. Kentucky, 31 March 2005 Missing Mass Only the e - and p + are measured –actually measure d(e,e’p)X and thus need cuts to ensure that X = n Define “missing” energy, momentum, and mass: Demanding that m M = m n helps ensure that X = n Momentum magnitude corrections greatly improve m M spectra

27. U. Kentucky, 31 March 2005 Missing Momentum Good MC agreement up to p M = 0.5GeV/c Left Sector ElectronRight Sector Electron

28. U. Kentucky, 31 March 2005 Beam-Vector Asymmetry

29. U. Kentucky, 31 March 2005 Beam-Vector Asymmetry (cont.)

30. U. Kentucky, 31 March 2005 Tensor Asymmetry Results

31. U. Kentucky, 31 March 2005 Tensor Asymmetry (cont.)

32. U. Kentucky, 31 March 2005 Potential Dependence Monte Carlo for Bonn, Paris, and V18 potentials compared to BLAST data Potential dependence small compared to MEC and IC contributions

33. U. Kentucky, 31 March 2005 Determination of hP z

34. U. Kentucky, 31 March 2005 D(e,e’n) Kinematic Distribution

35. U. Kentucky, 31 March 2005 Missing Mass from D(e,e’n) QES

36. U. Kentucky, 31 March 2005 G E /G M for the Neutron from D(e,e’n) QES

37. U. Kentucky, 31 March 2005 GnMGnM

38. G n E from D(e,e’n)

39. U. Kentucky, 31 March 2005 Conclusions and Outlook World-class data for G p E /G p M, G n E /G n M, D(e,e’) elastic T 20, D(e,e’p) QES A V ed and A T d,, Inclusive H(e,e’)X and D(e,e’)X Analysis still in progress Many other channels to be analyzed: H(e,e’p)    H(e,e’n)  , H( ,n)  , D( ,pn), … etc. Continuing to take data on D until June (?); expect to at least double data set (or more!) Shut down and decommission; relocate detectors and remap BLAST field

40. U. Kentucky, 31 March 2005 The BLASTers