EINN 2005

BLAST: A Detector for Internal Target Experiments

Introduction

Overview

Present Results

Outlook

John Calarco, EINN 2005

“We had a BLAST at MIT-Bates”

EINN 2005

Approved BLAST Scientific Program

Form Factor Measurements: Q2 1.0 (GeV/c)2

Proton Charge and MagnetismElastic 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)

EINN 2005

General Kinematics for Polarized e Scattering on a Polarized Target

EINN 2005

Bates Linac

500MeV Linac recirculated to reach up to 1GeV Inject into South Hall Ring Polarization maintained by Siberian snake Polarization monitored real time by Compton Polarimeter Internal Target located in the ring vacuum

EINN 2005

• 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

The BLAST Spectrometer

DRIFT CHAMBERS

CERENKOVCOUNTERS

SCINTILLATORSNEUTRON COUNTERS

TARGET

BEAM

BEAM

EINN 2005

BLAST: Configuration used for present data

EINN 2005

EINN 2005

ep Elastic Kinematic Correlation

EINN 2005

GE/GM Results

EINN 2005

Motivation: Why T20

• 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

EINN 2005

Kinematics:pe

=24MeV d=1o

… …

Mass: timing & trackingBlue: everythingRed: after coplanarity cut

Deuterons

Protons

+ ?

e-d Elastic Event Selection

e- left, d+ right

e- right, d+ left

EINN 2005

T20 and T21 for ed elastic scattering

EINN 2005

Difference between T20 and theory

EINN 2005

Helicity dependent T10 and T11 from ed elastic scattering

Acrobat Document

EINN 2005

GM from world A(Q2) and BLAST T20 , T21 , and helicity dependent T11

EINN 2005

Beam-Vector Asymmetry for D(e,e’p) QES

EINN 2005

Beam-Vector Asymmetry (cont.)

EINN 2005

Tensor Asymmetry Results

EINN 2005

Potential Dependence

• Monte Carlo for Bonn, Paris, and V18 potentials compared to BLAST data

• Potential dependence small compared to MEC and IC contributions

EINN 2005

GEn from Av

ed in polarized D(e,e’n)

EINN 2005

Conclusions and Outlook

• World-class data for GpE/Gp

M , GnE , D(e,e’) elastic T20 ,

T21 , and helicity dependent T11 , D(e,e’p) QES AVed and

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)H(e,e’n) , H(n+) , etc..

• Will BLAST run again at another facility?

EINN 2005

BLAST COLLABORATION 

R. Alarcon, E. Geis, J. Prince, B. Tonguc, A. YoungArizona 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. XuDuke University Durham, 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. ZwartMassachusetts Institute of Technology, Cambridge, MA 02139

andBates 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. RapaportOhio 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. PoolmanVrije Universitaet and NIKHEF, Amsterdam, The Netherlands

 W. Haeberli, T. Wise

University of Wisconsin, Madison, WI 53706 

   

EINN 2005

The BLASTers

EINN 2005

GnM

EINN 2005

Asymmetries AL and AR

EINN 2005

GE/GM from ep Elastic

EINN 2005

Tensor Asymmetry (cont.)

EINN 2005

GE/GM — World Data

EINN 2005

GE and GM ResultsBLAST + World Data

EINN 2005

Detector Performance• All detectors operated 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• Reconstruction resolutions good but still being

improved

current goal

p 3% 2%

0.5° 0.3°

0.5° 0.5º

z 1cm 1cm

EINN 2005

T20 for ed elastic scattering

EINN 2005

GnE from D(e,e’n)