The Neutron Electric Form Factor at

1
The Neutron Electric Form Factor at
Q2 2.8 and 4.3 (GeV/c)2
via Recoil Polarimetry
Jeopardy Review of E04-110 Jefferson
Laboratory PAC 33
Spokespersons
R. Madey (Kent State University)
S. Kowalski (Massachusetts Institute of
Technology)
A. Semenov (University of Regina)
B. Anderson (Kent State University)
B. Plaster (University of Kentucky)
2
Overview of proposal
2
E04-110 approved by PAC 26
25 days (physics measurements) approved to
measure the neutron electric form factor GEn at
Q2 4.3 (GeV/c)2
Recoil polarimetry from the quasielastic 2H( e,
e n )1H reaction
Updated proposal to PAC 33
25 days for Q2 4.3 (GeV/c)2 with ?GEn 0.0020
4 days for Q2 2.8 (GeV/c)2 with ?GEn 0.0030
Overlap with E02-013 using polarized 3He target
at Q2 1.3, 2.4, and 3.4
(GeV/c)2 10 systematics proposed
Overlap with E93-038 via recoil polarimetry from
deuteron to Q2
1.45 (GeV/c)2 2.5 systematics achieved
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
3
Current published GEn data
3
Q2 1.13 and 1.45 (GeV/c)2 most precise values
for GEn published to date
R. Madey et al., PRL 91, 122002 (2003)
E93-038
B. Plaster et al., PRC 73, 025205 (2006)
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
JLab PAC33
4
Future GEn data
4
Published JLab Data
E04-110 error bars proposal
E02-013 error bars proposed
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
5
Scientific motivation
5
Theory Review Report
GEn is of such fundamental importance to our
understanding of hadron structure that the
physics motivations are strong.
Proposed measurements to Q2 4.3 (GeV/c)2 will
have sufficient precision to challenge our
understanding of nucleon structure
Fundamental lattice QCD calculations
Isovector electromagnetic form factors
Constraints on theoretical models of nucleon
structure
Comparisons must consider all four GEp, GMp, GEn,
and GMn
Extractions of GEn via recoil polarimetry from 2H
and asymmetry from polarized 3He ? Powerful
cross-check (nuclei, FSI, etc.)
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
6
Lattice QCD calculations
6
Precision experimental data have potential to
confront ab initio lattice QCD calculations of
nucleon form factors
from S. Boinepalli et al., PRD 74, 093005
(2006)
Connected Diagrams
Disconnected Diagrams
Requires proton AND neutron form factors
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
7
Lattice QCD calculations
7
LHPC Collaboration hep-lat/0610007
C. Alexandrou, G. Koutsou, J.W. Negele, and A.
Tsapalis, PRD 74, 034508 (2006)
GEV
F1V
Theory Review Report
comparison with lattice calculations is
important motivation
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
8
GEp vs. GEn
8
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
9
Model calculations
9
Pion cloud models
VMD models
Lomon
Miller LFCBM
Friedrich and Walcher
Bijker and Iachello
QMC
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
10
Model calculations
10
Relativistic quarks G. Miller LFCBM
Quark models
PFSA
Light-front OGE CQ FF
hCQM CQ FF
nucl-th/0206027
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
11
Recoil polarimetry technique
11
Recoil polarization
Analyzed by second scattering in polarimeter with
analyzing power Ay
Ratio Technique Measure Both Pt and Pl
determines sign of GEn/GMn (important, as noted
by TAC theory)
small systematics Ay and Pe cancel
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
12
Quasielastic 2H ( e, e n ) 1H reaction
12
Arenhövel (1987) For quasifree emission in 2H(
e, e n )1H
Pt proportional to GEn as in n ( e, e n )
Insensitive to FSI, MEC, IC, and choice of NN
potential for deuteron wavefunction
Pt
(Tnp)c.m. 180
perfect quasifree neutron emission
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
13
Overview of experiment NPOL
13
Primary NPOL components
Charybdis dipole field for spin precession
Pb curtain attenuates gammas, charged
Front Array analyzer via spin-dependent n-p
scattering
Top/Bottom Rear Array up-down
scattering asymmetry ?
Dipole field permits access to both Pt and Pl
? spin precession angle
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
14
Enhanced E04-110 NPOL
14
converters (in blue)
Increased vertical acceptance
Larger front array 60 vs. 20 bars
Additional 10 ? 10 ? 100 cm3 and 10 ? 12.5 ?
100 cm3 bars
Better matched to HMS acceptance
Increased neutron polarimeter efficiency
3-cm-thick steel converters ahead of each layer
in rear array
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
15
Kinematics
15
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
16
Projected count rates
16
100 µA beam on 15-cm liquid deuterium target
Estimation of real-event rate includes analysis
cuts
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
17
Projected uncertainties
17
Asymmetry ratio for ?
Extraction of GEn/GMn
Projected statistical uncertainties
r ratio of reals/accidentals
Q2 4.3 (GeV/c)2
Q2 2.8 (GeV/c)2
? 25
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
18
Projected uncertainties
18
Asymmetry ratio for ?
Extraction of GEn/GMn
Projected statistical uncertainties
r ratio of reals/accidentals
? chosen sufficiently large to deflect
quasielastic protons from front array
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
19
Quasielastic events E93-038
19
E93-038 full range of kinematic acceptance at Q2
1.45 (GeV/c)2
pmiss vs. invariant mass W
E93-038 tight cuts on
Missing momentum
Scattered electron momentum bite
HMS-NPOL coincidence TOF
Powerful selection tool for quasielastic neutrons
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
20
Quasielastic events E04-110
20
Simulations for E04-110
Quasielastic and inelastic invariant mass spectra
normalized to SLAC NE-11 (similar kinematics)
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
21
E93-038 TOF spectra
21
HMS-NPOL Coincidence
NPOL Front-to-Rear
quasifree p0 prodn
9 ns window
suppressed by steel
Extraction of asymmetry
Cross-Ratio (or Super-Ratio)
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
22
FSI corrections
22
Arenhövel model for 2H(e,en)1H will be averaged
over acceptance
Relativistic PWBA model for kinematic acceptance
1)
2)
FSIMECIC corrections
E93-038
5.6
4.0
3.3
3.3 is robust upper estimate of FSI corrections
at Q2 2.8/4.3 (GeV/c)2
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
23
NPOL performance
23
Neutron Efficiency
Analyzing Power
Agreement between simulation/data basis for
extrapolation into E04-110 neutron energy range
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
24
Systematic uncertainties
24
E93-038 Systematic Uncertainties
(p,n)
(a) ? 40 precession
(b) ? 0, 90 precession
E04-110 systematic uncertainties estimated to be
small
Total error completely statistics dominated
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
25
Beamtime request
25
100 µA beam, 80 polarization, 15-cm LD2 target
measurements
LH2 target for assessment of false
asymmetry/dilution from contamination from
two-step process
Commissioning time with beam 7 days
HMS/NPOL/Möller check-out
(a) Overhead Charybdis dipole polarity changes
target changes DAQ operation
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
26
Prospects for 12-GeV running
26
For example
Ee 10 GeV beam
Q2 6.0 (GeV/c)2
?n 29.7
?GEn 0.0019
Ee 6.8 GeV
Tn 3.2 GeV
in 30 days
?e 17.1
Extraction of analyzing power and efficiency from
proposed measurement at Q2 4.3 (GeV/c)2 will
permit more reliable extrapolations to running in
the 12-GeV era
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
27
E04-110 collaboration
27
R. Madey, B.D. Anderson, A.R. Baldwin, D.M.
Manley, J.W. Watson, W.-M. Zhang
A. Ahmidouch, S. Danagoulian, A. Gasparian
S. Tajima
Los Alamos National Laboratory
Kent State University
North Carolina AT University
M. Khandaker, V. Punjabi, F. Wesselmann
M. Elaasar
R. Carlini, R. Ent, H. Fenker, D. Gaskell, M.K.
Jones, D. Higinbotham, A. Lung, D. Mack, G.
Smith, S. Taylor, W. Vulcan, B. Wojtsekhowski, S.
Wood, C. Yan
Southern University at New Orleans
Norfolk State Uniersity
R.E. Segel
H. Arenhövel
University of Mainz
Northwestern University
Jefferson Laboratory
R. Wilson
H. Mkrtchyan, R. Asaturyan, T. Navasardyan, V.
Tadevosyan
S. Kowalski
Harvard University
Massachusetts Institute of Technology
Yerevan Physics Institute
P.E. Ulmer
A. Yu. Semenov, G.J. Lolos, Z. Papandreou, I.A.
Semenova
Old Dominion University
A. Opper
George Washington University
A.I. Malakhov, A.K. Kurilkin, P.K. Kurilkin, V.P.
Ladygin, S.M. Piyadin
University of Regina
S. Wells, N. Simicevic
B. Plaster, W. Korsch
Louisiana Tech
Joint Institute for Nuclear Research
University of Kentucky
J. Martin, A. Micherdzinska
P. Markowitz, B. Raue, J. Reinhold
C. Howell
University of Winnipeg
Duke University
Florida International University
S. Jin, W.-Y. Kim, S.
Stepanyan, S. Yang
J.M. Finn, C. Perdrisat
D. Day, P. McKee
The College of William and Mary
Kyungpook National University
University of Virginia
C. Keppel, L. Tang, I. Albayrak, O. Ates,
C. Chen, M.E. Christy, M. Kohl, Y. Li,
A. Liyanage, Z. Ye, T. Walton, L. Yuan, L. Zhu
W. Tireman
H. Breuer
Northern Michigan University
University of Maryland
Hampton University
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
28
E04-110 collaboration
28
T. Reichelt
Major responsibilities
University of Bonn
NPOL Kent State
L. Gan
University of North Carolina Wilmington
Charybdis MIT
I. Sick
University of Basel
HMS JLab Hall C
K. McCormick
Analysis/Simulations Kentucky,
Pacific Northwest National Laboratory
Regina
Large/Experienced Collaboration 30 Institutions
from USA, Canada, Germany, Armenia, Russia,
Korea, Switzerland
Vetos Kentucky, Southern
University (New Orleans)
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
29
TAC Comments
29
PAC26 TAC Report
Given the experience gained by the
collaboration during E93-038, it is not
likely that any show stoppers will turn up in
this experiment.
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
30
Backup slides
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
31
Enhanced E04-110 NPOL
15
Schematic Not to scale
B-field ? to momentum of all neutrons from target
Charybdis modifications to match increased
vertical acceptance
E93-038 21.0-cm pole gap for 0.5-m vertical
acceptance
E04-110 tapered 19.5-cm to 40.4-cm pole gap
for 1.2-m vertical acceptance
field integral
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
32
FSI corrections
Arenhövel FSIMECIC model for 2H(e,en)1H
averaged over acceptance 2 independent
simulations
Relativistic PWBA model for kinematic acceptance
1)
2)
FSIMECIC corrections
E93-038
5.6
With similar range of acceptance/cuts in pmiss,
3.3 should be robust estimate of upper range for
FSI corrections at Q2 2.8/4.3 (GeV/c)2
4.0
3.3
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
33
GEp vs. GEn
Possible zero crossing in isovector electric form
factor GEV at Q2 4.5 (GeV/c)2
J.J. Kelly (2004)
Powerful test for models and lattice QCD
LFCBM
VMD
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
34
Reals/accidentals simulation
Projection for E04-110
Q2 2.8 (GeV/c)2
R/A 37.8
Results reliable with R/A so high
Q2 4.3 (GeV/c)2
R/A 21.0
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
35
Two-photon exchange for GEn/GMn
2-gamma correction smaller than statistical error
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
36
Calculation of kinematic variables
Note pmiss calculated solely
from (?, q ) and ?nq no TOF
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
37
Projected NPOL particle flux
mean target-front-array flight path 7.0 m
quasielastics
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
38
Corrupted events
Using singles rates for neutral/charged particles
shown on previous slide, estimated corrupted
event fraction
true hit in NPOL
background particle hit near true hit in NPOL
coincidence gate
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
39
Pb-curtain thickness
If singles rates unacceptably high, will increase
Pb-curtain thickness
Decrease in neutron rate (partly) compensated by
smaller corrupted event fraction
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
40
Model calculations
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
41
Isoscalar/isovector cross sections
Ratio of isoscalar to isovector cross sections
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
42
Beam polarization stability
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster
43
(No Transcript)
44
E93-038 asymmetries
23
Q2 1.13 (GeV/c)2
JLab PAC33
R. Madey, S. Kowalski, A. Semenov, B. Anderson,
B. Plaster