r. michaels, jlab ugm, june, 2011 lead ( pb) radius experiment : prex 208 208 pb e = 1 gev,...
TRANSCRIPT
![Page 1: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/1.jpg)
R. Michaels, Jlab UGM, June, 2011
Lead ( Pb) Radius Experiment : PREX208
208Pb
E = 1 GeV, electrons on lead
05
Elastic Scattering
Parity Violating Asymmetry
Spokespersons
Paul Souder, Krishna Kumar
Guido Urciuoli, Robert Michaels
Ran March – June 2010 in Hall A
Graduate Students
Ahmed Zafar, Chun Min Jen, Abdurahim Rakham (Syracuse)
Jon Wexler (UMass)
Kiadtisak Saenboonruang (UVa)
![Page 2: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/2.jpg)
R. Michaels, Jlab UGM, June, 2011
)(
sin4122 2
22
QF
QG
dd
dd
dd
dd
AP
WF
LR
LR
)( 2QF n
%1%3 n
n
R
dR
A
dA
Idea behind PREX
Z of Weak Interaction :
Clean Probe Couples Mainly to Neutrons( T.W. Donnelly, J. Dubach, I Sick 1989 )
0
In PWIA (to illustrate) :
w/ Coulomb distortions (C. J. Horowitz) :
0
![Page 3: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/3.jpg)
R. Michaels, Jlab UGM, June, 2011
Measured Asymmetry
Weak Density at one Q2
Neutron Density at one Q2
Correct for CoulombDistortions
Small Corrections forG
nE G
sE MEC
Assume Surface Thickness Good to 25% (MFT)
Atomic Parity Violation
Mean Field & Other
Models
Neutron
Stars
R n
PREX Physics Output
Slide adapted from C. Horowitz
![Page 4: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/4.jpg)
R. Michaels, Jlab UGM, June, 2011
Fundamental Nuclear Physics :
What is the size of a nucleus ?
Neutrons are thought to determine the size of heavy nuclei like 208Pb.
Can theory predict it ?
![Page 5: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/5.jpg)
R. Michaels, Jlab UGM, June, 2011
str
mb
d
d
1fmq
Reminder: Electromagnetic Scattering determines
r
rPb
208
(charge distribution)
1 2 3
d
d
![Page 6: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/6.jpg)
R. Michaels, Jlab UGM, June, 2011
Z of weak interaction : sees the neutrons
proton neutron
Electric charge 1 0
Weak charge 0.08 1
0
Analysis is clean, like electromagnetic scattering:
1. Probes the entire nuclear volume
2. Perturbation theory applies
6
![Page 7: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/7.jpg)
R. Michaels, Jlab UGM, June, 2011
)()()(ˆ5 rArVrV
)(
)(sin41
22 2
22
2
QF
QFQG
d
d
d
d
d
d
d
d
AP
NW
F
LR
LR
neutron weak charge >> proton weak charge
is small, best observed by parity violation
||)()(/
//3 rrrZrdrV )()()sin41(22
)( 2 rNrZG
rA NPWF
22 |)(| QFd
d
d
dP
Mott
)()(4
1)( 0
32 rqrjrdQF PP )()(
4
1)( 0
32 rqrjrdQF NN
Electron - Nucleus Potential
electromagnetic axial
Neutron form factor
Parity Violating Asymmetry
)(rA
1sin41 2 W
Proton form factor
0
Pb is spin 0208
![Page 8: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/8.jpg)
R. Michaels, Jlab UGM, June, 2011
( R.J. Furnstahl )
Measurement at one Q is sufficient to measure R
2
N
proposed error
Why only one parameter ?
(next slide…)
PREX:
![Page 9: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/9.jpg)
R. Michaels, Jlab UGM, June, 2011
ZN
Nuclear Structure: Neutron density is a fundamental observable that remains elusive.
Reflects poor understanding of symmetry energy of nuclear matter = the energy cost of
xn
)21()()2/1,(),( 2xnSxnExnE
n.m. density
ratio proton/neutrons
• Slope unconstrained by data
• Adding R from Pb will eliminate the
dispersion in plot.
N208
Slide adapted from J. Piekarewicz
![Page 10: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/10.jpg)
R. Michaels, Jlab UGM, June, 2011
Skx-s15Thanks, Alex Brown
PREX Workshop 2008
E/N
N
![Page 11: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/11.jpg)
R. Michaels, Jlab UGM, June, 2011
Skx-s20Thanks, Alex Brown
PREX Workshop 2008
![Page 12: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/12.jpg)
R. Michaels, Jlab UGM, June, 2011
Skx-s25Thanks, Alex Brown
PREX Workshop 2008
![Page 13: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/13.jpg)
R. Michaels, Jlab UGM, June, 2011
Application: Atomic Parity Violation• Low Q test of Standard Model
• Needs RN (or APV measures RN )
2
0
Isotope Chain Experiments e.g. Berkeley Yb
13
APV
rdrZrNG
H eePWNF
PNC35/2 )()sin41()(
22
![Page 14: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/14.jpg)
R. Michaels, Jlab UGM, June, 2011
Neutron
StarsWhat is the nature of extremely dense matter ?
Do collapsed stars form “exotic” phases of matter ? (strange stars, quark stars)
Crab Nebula (X-ray, visible, radio, infrared)
Application :
![Page 15: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/15.jpg)
R. Michaels, Jlab UGM, June, 2011
PREX & Neutron Stars
pn RRCrab Pulsar
( C.J. Horowitz, J. Piekarewicz )
R calibrates EOS of Neutron Rich Matter
Combine PREX R with Obs. Neutron Star Radii
Some Neutron Stars seem too Cold
N
N
Crust ThicknessExplain Glitches in Pulsar Frequency ?
Strange star ? Quark Star ?
Cooling by neutrino emission (URCA)
0.2 fm URCA probable, else not
Phase Transition to “Exotic” Core ?
![Page 16: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/16.jpg)
R. Michaels, Jlab UGM, June, 2011
How to do a Parity Experiment
Flux Integration Technique:HAPPEX: 2 MHzPREX: 500 MHz
(integrating method)
Example : HAPPEX
![Page 17: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/17.jpg)
R. Michaels, Jlab UGM, June, 2011
/)( AA
Pull Plot (example)
PREX Data
![Page 18: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/18.jpg)
R. Michaels, Jlab UGM, June, 2011
PAVI 09
Beam AsymmetriesA
raw = A
det - A
Q +
E+
ix
i
•natural beam jitter (regression) •beam modulation (dithering)
Slopes from
18
![Page 19: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/19.jpg)
R. Michaels, Jlab UGM, June, 2011
Slug # ( ~ 1 day)
Units: microns
RLhelicityforXX LR ,
Parity Quality Beam !
Helicity – Correlated Position Differences
< ~ 3 nm
Wien Flips helped !Average with signs = what exp’t feels
Points: Not sign corrected
![Page 20: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/20.jpg)
R. Michaels, Jlab UGM, June, 2011
Hall A Compton Upgrade
with Green Laser
Sirish Nanda, et. al.
1 % Polarimetry
at 1 GeV
![Page 21: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/21.jpg)
R. Michaels, Jlab UGM, June, 2011
Hall A Moller Upgrade
Superconducting Magnet from Hall C
Saturated Iron Foil Targets
1 % Polarimetry
Magnet and Target
DAQ Upgrade (FADC)
Sasha Glamazdin, et.al.
![Page 22: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/22.jpg)
R. Michaels, Jlab UGM, June, 2011
High Resolution Spectrometers
Elastic
Inelastic
detector
Q Q
Dipole
Quad
Spectrometer Concept: Resolve Elastic
target
Left-Right symmetry to control transverse polarization systematic
1st excited state Pb 2.6 MeV
![Page 23: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/23.jpg)
R. Michaels, Jlab UGM, June, 2011
Collimators
Septum Magnet
Top view
target
HRS-L
Q1
HRS-R
Q1
PREX Region After Target
Former O-Ring location which failed and caused significant time loss
Planned Tungsten Collimator and Shielding
![Page 24: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/24.jpg)
R. Michaels, Jlab UGM, June, 2011
10 m
-1 m
Geant 4 Radiation Calculations
• benchmarking against LD2 (ran at 100 uA)
• exploring shielding strategies
J. Mammei, L. Zana
Number of Neutrons per incident Electron
Z (distance along beamline)
1 mLD2 tgtPb tgt
1 - 50 MeV
50 - 500 MeV
0 - 1 MeV
Strategy
• Tungsten ( W ) plug
• Shield the W
• x10 reduction in 0.2 to 10 MeV neutrons
(similar to LD2)
00 37.0
W
PREX-II proposal
PREX -I
PREX -II
![Page 25: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/25.jpg)
R. Michaels, Jlab UGM, June, 2011
Pure, Thin 208 Pb Target
Momentum (GeV/c)
Lead 5- State
2.6 MeV
High Resolution Spectrometers
DETECTOR footprint
25
![Page 26: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/26.jpg)
R. Michaels, Jlab UGM, June, 2011
Diamond LEAD
• Three bays
• Lead (0.5 mm) sandwiched by diamond (0.15 mm)
• Liquid He cooling (30 Watts)
Lead / Diamond Target
![Page 27: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/27.jpg)
R. Michaels, Jlab UGM, June, 2011
Performance of Lead / Diamond Targets
Last 4 days at 70 uA
Targets with thin diamond backing (4.5 % background) degraded fastest.
Thick diamond (8%) ran well and did not melt at 70 uA.
meltedmelted
NOT melted
Solution: Run with 10 targets.
![Page 28: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/28.jpg)
R. Michaels, Jlab UGM, June, 2011
y
z
xS
k
+ -
AT > 0 means
)'( eeeT kkSA
Beam-Normal Asymmetry in elastic electron scatteringi.e. spin transverse to scattering plane
Possible systematic if small transverse spin component
New results PREX
ppmAC T 35.036.052.6:12
ppmAPb T 36.019.013.0:208
• Small AT for 208Pb is a big (but pleasant) surprise. • AT for 12C qualitatively consistent with 4He and available calculations (1) Afanasev ; (2) Gorchtein & Horowitz
![Page 29: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/29.jpg)
R. Michaels, Jlab UGM, June, 2011
Error Source Absolute (ppm) Relative ( % )
Polarization (1) 0.0071 1.1
Beam Asymmetries (2) 0.0072 1.1
Detector Linearity 0.0071 1.1
BCM Linearity 0.0010 0.2
Rescattering 0.0001 0
Transverse Polarization 0.0012 0.2
Q2 (1) 0.0028 0.4
Target Thickness 0.0005 0.112C Asymmetry (2) 0.0025 0.4
Inelastic States 0 0
TOTAL 0.0130 2.0
Systematic Errors
(1) Normalization Correction applied
(2) Nonzero correction (the rest assumed zero)
![Page 30: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/30.jpg)
R. Michaels, Jlab UGM, June, 2011
PREX Physics Result
LR
LRPVA
)(0130.0)(0604.06571.0 syststat ppm
at Q2 = 0.00906 GeV2
Statistics limited ( 9% )
Systematic error goal achieved ! (2%)
9.2 % 2.0 %
![Page 31: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/31.jpg)
R. Michaels, Jlab UGM, June, 2011
PREX Asymmetry (Pe x A)
ppm
Slug ~ 1 day
(blinded, raw)
![Page 32: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/32.jpg)
R. Michaels, Jlab UGM, June, 2011
PREX Physics Interpretation
![Page 33: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/33.jpg)
R. Michaels, Jlab UGM, June, 2011
Asymmetry leads to RN
Neutron Skin = RN - RP = 0.34 + 0.15 - 0.17 fm
arXiv:1010.3246 [nucl-th] Shufang Ban, C.J. Horowitz, R. Michaels
Establishing a neutron skin at 95% CL
![Page 34: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/34.jpg)
R. Michaels, Jlab UGM, June, 2011
PREX – II Proposal
Future ?
![Page 35: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/35.jpg)
R. Michaels, Jlab UGM, June, 2011
Future ?
![Page 36: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/36.jpg)
R. Michaels, Jlab UGM, June, 2011
Other Nuclei ?
Shape Dependence ?RN
RN
Surface thickness
Surface thickness
arXiv:1010.3246 [nucl-th]
Parity Violating Electron Scattering Measurements of Neutron Densities Shufang Ban, C.J. Horowitz, R. Michaels
![Page 37: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/37.jpg)
R. Michaels, Jlab UGM, June, 2011
PREX : Summary • Fundamental Nuclear Physics with
many applications
• Achieved a 9% stat. error in Asymmetry (original goal : 3 %)
• Systematic Error Goals Achieved !!
• Significant time-losses due to O-Ring problem and radiation damage
• Proposal for PREX-II in preparation
![Page 38: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/38.jpg)
R. Michaels, Jlab UGM, June, 2011
Extra Slides
![Page 39: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/39.jpg)
R. Michaels, Jlab UGM, June, 2011
Corrections to the Asymmetry are Mostly Negligible
• Coulomb Distortions ~20% = the biggest correction.
• Transverse Asymmetry (to be measured)
• Strangeness
• Electric Form Factor of Neutron
• Parity Admixtures
• Dispersion Corrections
• Meson Exchange Currents
• Shape Dependence
• Isospin Corrections
• Radiative Corrections
• Excited States
• Target Impurities
Horowitz, et.al. PRC 63 025501
![Page 40: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/40.jpg)
R. Michaels, Jlab UGM, June, 2011
PAVI 09
Optimum Kinematics for Lead Parity: E = 1 GeV if <A> = 0.5 ppm. Accuracy in Asy 3%
n
Fig. of merit
Min. error in R
maximize:
1 month run
1% in R
n
(2 months x 100 uA 0.5% if no systematics)
5
![Page 41: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/41.jpg)
R. Michaels, Jlab UGM, June, 2011
Liquid/Solid Transition Density
• Thicker neutron skin in Pb means energy rises rapidly with density Quickly favors uniform phase.
• Thick skin in Pb low transition density in star.
FP
TM1Solid
Liquid
Neutron Star Crust vs Pb Neutron Skin
208Pb
Neutron Star
C.J. Horowitz, J. Piekarawicz
![Page 42: R. Michaels, Jlab UGM, June, 2011 Lead ( Pb) Radius Experiment : PREX 208 208 Pb E = 1 GeV, electrons on lead Elastic Scattering Parity Violating Asymmetry](https://reader036.vdocuments.mx/reader036/viewer/2022081518/5514df9c550346b0338b57cf/html5/thumbnails/42.jpg)
R. Michaels, Jlab UGM, June, 2011
.../ 3/12
4
AaA
ZNaa
A
Esv
)1(
PREX: pins down the symmetry energy (1 parameter)
( R.J. Furnstahl )
energy cost for unequal # protons & neutrons
PREX
PREX error bar
Pb208 Actually, it’s the
density dependence of a4 that we pin down.