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BLAST: A Detector for Internal Target Experiments

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. BLAST COLLABORATION R. Alarcon, E. Geis , J. Prince, B. Tonguc, A. Young

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BLAST: A Detector for Internal Target Experiments

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  1. 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 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 UniversityDurham, NC 27708-0305 H. Arenhövel, Johannes Gutenberg-Universität, 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 U. Kentucky, 31 March 2005

  3. Approved BLAST Scientific Program Form Factor Measurements: Q2  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) U. Kentucky, 31 March 2005

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

  5. 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 Bates Linac U. Kentucky, 31 March 2005

  6. The BLAST Spectrometer BEAM DRIFT CHAMBERS TARGET • Left-right symmetric detector • simultaneous parallel and perpendicular asymmetry determination • Large acceptance • covers 0.1GeV2 ≤ Q2 ≤ 1GeV2 • 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 CERENKOV COUNTERS BEAM NEUTRON COUNTERS SCINTILLATORS U. Kentucky, 31 March 2005

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

  8. 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 U. Kentucky, 31 March 2005

  9. U. Kentucky, 31 March 2005

  10. ep Elastic Kinematic Correlation U. Kentucky, 31 March 2005

  11. Asymmetries AL and AR U. Kentucky, 31 March 2005

  12. mGE/GM from ep Elastic U. Kentucky, 31 March 2005

  13. mGE/GM Comparison between BLAST and JLab U. Kentucky, 31 March 2005

  14. Inclusive H(e,e’) Cross Sections sTL , sTT from MC U. Kentucky, 31 March 2005

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

  16. 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 U. Kentucky, 31 March 2005

  17. Deuteron Electrodisintegration • 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 Gne • Beam-vector dilution (h•Pz) gotten from analysis U. Kentucky, 31 March 2005

  18. Beam and Target Performance • Beam fills to 175mA with 25min lifetime, average polarization = 65% ± 4% • Deuterium polarization in tri-state mode • (Vector, Tensor) : (-Pz, +Pzz) ( +Pz, +Pzz) (0, -2Pzz) • Flow = 2.2  1016 atoms/s, Density = 6.0  1013 atoms/cm2 • Luminosity = 4.0  1031 /cm2/s @ 140mA • Target polarizations from data analysis: Pz = 88% ± 4%, Pzz = 65% ± 2% U. Kentucky, 31 March 2005

  19. e-d elastic scattering: GC GM GQ • GQ > D-state > Tensor Force • Rosenbluth Separation • 3rd Measurement to separate 3 form factors • Tensor Asymmetry in e-d elastic scattering Motivation II: Why T20 U. Kentucky, 31 March 2005

  20. Everything Colpanarity Kinematics Full cuts e-d Elastic Event Selection • 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. • Timing Cuts • Coplanarity: =1o U. Kentucky, 31 March 2005

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

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

  23. From Measurements of the Elastic Vector Asymmetry AVed U. Kentucky, 31 March 2005

  24. Deuterium Wave Functions (Bonn Potential) • 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 pM ~ 0.3GeV (Bonn Potential) U. Kentucky, 31 March 2005

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

  26. 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 mM = mn helps ensure that X = n Momentum magnitude corrections greatly improve mM spectra Missing Mass U. Kentucky, 31 March 2005

  27. Missing Momentum Left Sector Electron Right Sector Electron • Good MC agreement up to pM = 0.5GeV/c U. Kentucky, 31 March 2005

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

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

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

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

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

  33. Determination of hPz U. Kentucky, 31 March 2005

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

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

  36. GE/GMfor the Neutron from D(e,e’n) QES U. Kentucky, 31 March 2005

  37. GnM U. Kentucky, 31 March 2005

  38. GnEfrom D(e,e’n) U. Kentucky, 31 March 2005

  39. Conclusions and Outlook • World-class data for GpE/GpM , GnE/GnM , D(e,e’) elastic T20 , D(e,e’p) QES AVedand ATd,, Inclusive H(e,e’)X and D(e,e’)X • Analysis still in progress • Many other channels to be analyzed: H(e,e’p)p0 , H(e,e’n)p+ , H(g,n)p+ , D(g,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 U. Kentucky, 31 March 2005

  40. The BLASTers U. Kentucky, 31 March 2005

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