a precision measurement of g e p /g m p with blast
DESCRIPTION
A Precision Measurement of G E p /G M p with BLAST. Chris Crawford MIT Laboratory for Nuclear Science May 18, 2005. Introduction Formalism World Data Experiment overview Experimental Setup LDS polarized target BLAST detector Calibrations. Analysis Cuts & Yields Asymmetry - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/1.jpg)
A Precision Measurement of GE
p/GMp with BLAST
Chris Crawford
MIT Laboratory for Nuclear Science
May 18, 2005
![Page 2: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/2.jpg)
Outline
Introduction» Formalism
» World Data
» Experiment overview
Experimental Setup» LDS polarized target
» BLAST detector
» Calibrations
Analysis» Cuts & Yields
» Asymmetry
» Extraction of GE/GM
» Systematic errors
Conclusion» Results: GE/GM
» Separation of GE, GM
![Page 3: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/3.jpg)
Introduction
GE,GM fundamental quantities describing charge/magnetization in the nucleon
Test of QCD based calculations and models
Provide basis for understanding more complex systems in terms of quarks and gluons
Probe the pion cloud QED Lamb shift
![Page 4: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/4.jpg)
Form Factors of the Nucleon
Form Factor definition
Nucleon current
Breit frame
![Page 5: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/5.jpg)
Elastic Cross Section
= target spin angle w/r to the beam line
![Page 6: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/6.jpg)
World DataWorld Unpolarized Data
![Page 7: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/7.jpg)
Polarization Transfer
Recoil proton polarization
Focal Plane Polarimeter» recoil proton scatters
off secondary 12C target» Pt, Pl measured from
φ distribution » Pb, and analyzing power
cancel out in ratio
![Page 8: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/8.jpg)
GE/GM — World Data
![Page 9: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/9.jpg)
Theory and ModelsDirect QCD calculations
» pQCD scaling at high Q2
» Lattice QCDMeson Degrees of Freedom
» Dispersion analysis, Höhler et al. 1976» Soliton Model, Holzwarth 1996» VMD + Chiral Perturbation Theory, Kubis et al. 2000» Vector Meson Dominance (VMD), Lomon 2002
QCD based constituent quark models (CQM)» LF quark-diquark spectator, Ma 2002» LFCQM + CBM, Miller 2002
†Nucleon Electromagnetic Form Factors, Haiyan Gao, Int. J. of Mod. Phys. E, 12, No. 1, 1-40(Review) (2003)
![Page 10: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/10.jpg)
Models Consistent with Polarized Data
![Page 11: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/11.jpg)
Form Factor Ratio @ BATES
Exploits unique features of BLAST» internal target: low dilution, fast spin reversal» large acceptance: simultaneously measure all Q2 points » symmetric detector: ratio measurement
Different systematics » also insensitive to Pb and Pt
» no spin transportQ2 = 0.1 – 0.9 (GeV/c) 2
» input for P.V. experiments» structure of pion cloud
![Page 12: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/12.jpg)
Asymmetry Super-ratio Method
Beam-Target Double Spin Asymmetry
Super-ratio
![Page 13: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/13.jpg)
Polarized Beam and Target
Storage Ring» E = 850 MeV» Imax=225 mA» Pb = 0.65
Internal ABS Target» 60 cm storage cell» t = 4.91013 cm-2 » Pt = 0.80
isotopically pure internal targethigh polarization, fast spin reversal L = 3.1 1031 cm-2s-1
H2: 98 pb-1 D2: 126 pb-1+2005 run
![Page 14: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/14.jpg)
Atomic Beam Source
Standard technologyDissociator & nozzle2 sextupole systems3 RF transitions
1
3
2
4nozzle
6-pole
1
2MFT (2->3)
1
3
6-pole
1Spin State Selection:
![Page 15: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/15.jpg)
Laser Driven Source (LDS)
Optical pumping& Spin Exchange
Spincell designTarget and
PolarimeterResults
![Page 16: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/16.jpg)
Spin-Exchange Optical pumping
![Page 17: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/17.jpg)
LDS Experimental Setup
![Page 18: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/18.jpg)
Pictures of the LDS
![Page 19: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/19.jpg)
Atomic Dissociation
![Page 20: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/20.jpg)
Atomic Polarization
![Page 21: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/21.jpg)
Comparison of Polarized Targets
![Page 22: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/22.jpg)
BLAST Detector PackageDetector Requirements
Definition of qe 2, e .°, z 1
cm e/p/n/ separation
PID: t 1, Čerenkov Optimize statistics
Large Acceptance Asymmetry Super-ratios
Symmetric Detector Polarized targets
1 m diameter in target regionZero field at targetB-gradients 50 mG/cm
![Page 23: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/23.jpg)
TOF Scintillators
timing resolution: σ=350 psvelocity resolution: σ= 1%
ADC spectrum coplanarity cuts
![Page 24: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/24.jpg)
Cosmics TOF Calibration
L 15
L 12
L 9
L 6
L 3
L 0
R 0 R 3 R 6 channels
channels
![Page 25: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/25.jpg)
TOF Scintillator Cuts
TOF paddle, electron
TO
F p
add
le,
pro
ton
![Page 26: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/26.jpg)
Čerenkov Detectors
1 cm thick aerogel tiles Refractive index 1.02-1.03 White reflective paint 80-90 % efficiency
5" PMTs, sensitive to 0.5 Gauss Initial problems with B field Required additional shielding 50% efficiency without shielding
![Page 27: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/27.jpg)
Drift Chambers 2 sectors × 3 chambers 954 sense wires 200μm wire resolution signal to noise ratio 20:1
![Page 28: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/28.jpg)
NSED (Online Display)
![Page 29: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/29.jpg)
Reconstruction
Scintillators» timing, calibration
Wire chamber» hits, stubs, segments
» link, track fit
PID, DST
![Page 30: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/30.jpg)
Newton-Rhapson Track Fitter
![Page 31: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/31.jpg)
Hyperbolic timedist function
D
TDC
![Page 32: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/32.jpg)
Linear T2D Calibration
28 MeV
12 MeV
p (GeV/c)
~ 1mm resolution
2
72
33
![Page 33: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/33.jpg)
Wire Chamber Efficiency
![Page 34: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/34.jpg)
WC Offsets/Resolution/Cuts
pe e e ze
pp p p zp
![Page 35: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/35.jpg)
Tracking Efficiency
![Page 36: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/36.jpg)
Comparison of Yields with MC
![Page 37: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/37.jpg)
Experimental Spin Asymmetry
![Page 38: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/38.jpg)
Single-asymmetry Method measure P first,
use to calculate R» model-dependent
Super-ratio Method2 equations in P, R
in each Q2 bin j
» independent measure of polarization in each bin!
» 2n parameters Pj, Rj
Global Fit Methodfit for P, R1, R2, … from
all Aij together» model independent
» better statistics
» n+1 parameters
» can also fit for
i = left,right sector
j = Q2 bin (1..n)
= spin angle
![Page 39: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/39.jpg)
Extractions of GE/GM
![Page 40: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/40.jpg)
Single AsymmetryExtraction
![Page 41: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/41.jpg)
Systematic Errors
Q2 (1.8%)» comparison of e and p
» difference between left and right sectorsmost problematic
» appeal to TOF timing !
(0.8%) » fieldmap: 47.1° ± 1°
» Hohler: 47.5° ± 0.8°
» Fit Method: 42° ± 3°
» (1st 7 bins) 48° ± 4°
» T20 analysis: 46.5° ± 3°
![Page 42: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/42.jpg)
GE/GM Results
![Page 43: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/43.jpg)
Extraction of GE and GM
![Page 44: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/44.jpg)
GE and GM ResultsBLAST + World Data
![Page 45: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/45.jpg)
Q2 Corrections from TOF
![Page 46: A Precision Measurement of G E p /G M p with BLAST](https://reader035.vdocument.in/reader035/viewer/2022062500/568157a3550346895dc535de/html5/thumbnails/46.jpg)
Conclusion
1st measurement of GE/GM using double spin asymmetry
2 – 3.5× improvement in precision of GE/GM at Q2 = 0.1– 0.5 GeV2
sensitive to the pion cloudis dip in GE around Q2=0.3 GeV2 real?
systematic errors are being reduced