Parity‐viola+on Studies at JLab‐12GeV

Kent Paschke

University of Virginia

Many figures from  K.Kumar, P.Souder, E. Chudakov, and others

2

Parity‐Viola+on in Electron ScaHering

•Incident beam is longitudinally polarized•Change sign of longitudinal polariza+on•Measure frac+onal rate difference

! =!!M! +MZ

!!2ScaHering cross‐sec+on

γ Z0

γ 2 !!!MZ

!!!!M!

!!

! 10!4 Q2!GeV2

"APV !

GF Q2

4!"

!ge

AgTV + #ge

V gTA

"

3

Precision Electroweak Physics

• pioneering• recent• next generation• future

The 12 GeV upgrade will open new opportuni+es for ‐ studies of nucleon structure in the valance regime‐ precision electroweak physics These opportuni+es will come with 

significant new technological challenges

Steady progress in technology:

• part per billion systematic control

• 1% systematic control

• Major developments in

- photocathodes ( I & P )

- polarimetry- high power cryotargets- nanometer beam stability- precision beam diagnostics- low noise electronics- radiation hard detectors

Electroweak Physics Away from Z pole

 Precision Z observables establish anchor points for the Standard ModelAway from the Z resonance, New Physics neutral‐current 

interac+ons can be found

4

Processes with poten+al sensi+vity to PV couplings:  ‐ neutrino‐nucleon deep inelas+c scaHering  ‐ Atomic parity viola+on (APV)  ‐ parity‐viola+ng electron scaHering

NuTeV at Fermilab 133Cs at Boulder

At low energies: 

The Standard Model neutral current is well studied at the Z pole

Proton Weak Charge

5

If measurement at low energy comes up different than SM predic+on, indicates proton charged for some other (parity‐viola+ng) interac+on

Proton Extrapolation

G0

PVA4

HAPPEX

SAMPLEProton

weak charge

SM

PDG

0 0.05 0.1 0.15 0.2 0.25 0.3

Q2 !GeV2"0

0.1

0.2

0.3

0.4

ALRp!!!!!

HAPPEX

SAMPLE

PVA4

G0

0 0.05 0.1 0.15 0.2 0.25 0.3

Q2 !GeV2"0

0.1

0.2

0.3

0.4

ALRp!!!!! Theory

estimate for anapole FF

RDY et al., PRL99,122003(2007)

slope due to proton structure

Global fit of exis+ng strange‐quark program data limits hadronic uncertain+es and constrains proton weak charge

“Strange Quark” program collected extensive precision WNC form‐factor data

Bounding the vector weak charge

6

SM value

R. Young et al., PRL 99 122003 (2007)

With this parameteriza+on for hadronic effects, what can be said about Standard Model parameters?

QpW = 2 C1u + C1d

These “form factor” measurements offer a powerful 

constraint on new physics orthogonal to other lepton‐quark coupling combina+ons

Neutral Weak charge of Up, Down quarks

Proton Weak Charge with Qweak

7

δQWp=4%

- Non‐perturba+ve theory g ~ 2π Λ ~ 29 TeV

- Extra Z’ g ~ 0.45 m Z’ ~ 2.1 TeV

Figure: R.Young

PV‐DIS with SOLID at 11 GeV

8

9

Deep Inelas+c ScaHering

For an isoscalar target like 2H, structure funcCons largely cancel in the raCo at high x

e-

N X

e-

Z* γ*

At high x, APV becomes independent of x, W, with well‐defined SM predic+on for Q2 and y

Sensi+ve to new physics at the TeV scale

a(x) and b(x) contain quark distribu+on func+ons fi(x)

0

1

at high x

a(x) =310

!2C1u

"1 +

2c+

u+ + d+

#!C1d

"1 +

2s+

u+ + d+

#+ · · ·

$

0b(x) =

310

[2C2u !C2d]!

uv + dv

u+ + d+

"+ · · ·

PVDIS w/ Base Equipment

Prescott et al(SLAC)

PDG Best Fit

Young Full Fit

Sample

6 GeV PVDIS 3% Ad measurement:Bands correspond to central values of either PDG best fit or Young et al.’s best fit.

StandardModel

SHMS

HMS

Proposal approved for 11 GeV:Factor of ~ 2 to 3 improvement

E08‐011: PVDIS off 2H at 6 GeV

•08-011 provides first look, at x~0.25-0.3• Insensitive to CSV, HT, but possibly sensitive to the quark sea?

•11 GeV, allows greater precision at higher x, but doesn’t provide lever arm to fully separate QCD effects

10

11

CSV with PVDISParton-level charge symmetry assumed in deriving 2H APV

Charge Symmetry Violation may arise from• u,d quark mass difference• electromagnetic effects

• Direct sensitivity of parton-level CSV• Important implications for high energy collider pdfs• Could explain significant portion of the NuTeV anomaly

Sensi+vity will e enhanced if u+d falls off more rapidly than δu‐δd as x → 1

12

Higher Twist

≠• APV sensi+ve to diquarks: ra+o of weak to electromagne+c charge depends on amount of coherence (elas+c He vs PVDIS)• Do diquarks have twice the x of single quarks?  High x is prime spot for valance quark‐quark higher‐twist contribu+ons (in hadronic vector term, contribu+ons from smaller axial term require constraint from neutrino data).

Subject of recent workshop at Madison, Wisconsin

Parton Modelor

leading twist

Di‐quarks

Quark‐gluondiagram

13

Coherent Program of PVDIS Study

• Measure AD in NARROW bins of x, Q2 with 0.5% precision

• Cover broad Q2 range for x in [0.3,0.6] to constrain HT• Search for CSV with x dependence of AD at high x

• Use x>0.4, high Q2, and to measure a combination of the Ciq’s

Strategy: requires precise kinema+cs and broad range

x y Q2

New Physics no yes no

CSV yes no no

Higher Twist yes no yes

Fit data to:

C(x)=βHT/(1‐x)3

Addi+onal measurements from hydrogen target provides high precision on d/uMeasurement on nulcei gives access to “EMC” type effects 

(isovector vector mean field effects, Cloet, Bentz and Thomas)

 SOLID: Solenoid Spectrometer for PVDIS Physics

Figure from E.Chudakov

trackingE-calgas Cerenkovcollimator

A large solenoidal spectrometer works • need BaBar, CDF or CLEOII Solenoid• fast tracking, particle ID and “parity” counting

electronics• polarimetry ~ 0.4%

• 20o - 35o, E’~ 1.5 - 5 GeV• δp/p ~ 2% • some regions 10’s of kHz/mm2

• Pion rejection with Cerenkov + segmented calorimeter.

15PAC34

Sta+s+cal Errors (%) vs Kinema+cs

4 months at 11 GeV

2 months at 6.6 GeV

Sta+s+cal uncertainty σA/A (%)shown at center of bins in Q2, x

Strategy: sub-1% precision over broad kinema+c range for sensitive Standard Model test and detailed study of hadronic structure contributions

16

PAC34

Precision on sin2θW

fig from J. Erler

Impressive precision on sin2θw (comparable to Qweak) 

but real value is in sensi+vity to different  combina+on of couplings

Constraint on contact interac+ons

16

PAC34

Precision on sin2θW

fig from J. Erler

Impressive precision on sin2θw (comparable to Qweak) 

but real value is in sensi+vity to different  combina+on of couplings

Constraint on contact interac+ons

Theore+cal developments on higher‐twist contribu+ons, RγZ, target‐mass correc+ons, etc. will be crucial

Neutrino data will pay a key role in controlling these effects

17

D. Armstrong, T. Averett, J. M. Finn

William and Mary P. Decowski

Smith College L. El Fassi, R. Gilman,

R. Ransome, E. SchulteRutgers

W. Chen, H. Gao, X. Qian, Y. Qiang, Q. Ye

Duke UniversityK. A. Aniol

California StateG. M. Urciuoli

INFN, Sezione di RomaA. Lukhanin, Z. E. Meziani,

B. SawatzkyTemple University

P. M. King, J. RocheOhio University

E. BeiseUniversity of Maryland

W. Bertozzi, S. Gilad, W. Deconinck, S. Kowalski,

B. Moffit MIT

Benmokhtar, G. Franklin, B. Quinn

Carnegie MellonG. Ron

Tel Aviv University

T. HolmstromLongwood University

P. MarkowitzFlorida International

X. JiangLos Alamos

W. KorschUniversity of Kentucky

J. Erler Universidad Autonoma de

MexicoM. J. Ramsey-Musolf

University of WisconsinC. Keppel

Hampton UniversityH. Lu, X. Yan, Y. Ye, P. Zhu

University of Science and Technology of China

N. Morgan, M. PittVirginia Tech

J.-C. PengUniversity of Illinois

H. P. Cheng, R. C. Liu, H. J. Lu, Y. Shi

Huangshan UniversityS. Choi, Ho. Kang, Hy. Kang B. Lee,

Y. OhSeoul National University

J. Dunne, D. DuttaMississippi State

K. Grimm, K. Johnston, N. Simicevic, S. WellsLouisiana Tech

O. Glamazdin, R. PomatsalyukNSC Kharkov Institute

for Physics and Technology

Z. G. XiaoTsinghua University

B.-Q. Ma, Y. J. MaoBeijing UniversityX. M. Li, J. Luan, S. Zhou

China Institute of Atomic Energy

B. T. Hu, Y. W. Zhang, Y. Zhang

Lanzhou UniversityC. M. Camacho, E. Fuchey,

C. Hyde, F. ItardLPC Clermont,

Université Blaise Pascal A. Deshpande

SUNY Stony BrookA. T. Katramatou,

G. G. PetratosKent State University

J. W. MartinUniversity of Winnipeg

Collabora+onP. Bosted, J. P. Chen, E. Chudakov, A. Deur,

O. Hansen, C. W. de Jager, D. Gaskell, J. Gomez,

D. Higinbotham, J. LeRose, R. Michaels, S. Nanda, A. Saha, V. Sulkosky,

B. Wojtsekhowski

Jefferson LabP. A. Souder, R. Holmes

Syracuse UniversityK. Kumar, D. McNulty,

L. Mercado, R. Miskimen

U. MassachusettsH. Baghdasaryan, G. D. Cates, D. Crabb, M. Dalton, D. Day,

N. Kalantarians, N. Liyanage, V. V. Nelyubin, B. Norum, K. Paschke, S. Riordan,

O. A. Rondon, M. Shabestari, J. Singh, A. Tobias, K. Wang,

X. Zheng

University of VirginiaJ. Arrington, K. Hafidi,

P. E. Reimer, P. Solvignon

Argonne

MOLLER(Measurement of Lepton‐Lepton Electroweak Reac+on)

MØller scaHering at 11 GeV

18

Møller ScaHering at 11 GeV

19

Purely leptonic reac+on

�

APV ∝meElab (1− 4sin2ϑW )

�

δ(sin2ϑW )sin2ϑW

≅ 0.05δ(APV )APV

�

σ ∝ 1Elab

Figure of Merit rises linearly with Elab

Møller ScaHering at 11 GeV

19

•Comparable to the best measurements (LEP and BaBar)•Best new measurement un+l Linear Collider or Neutrino Factory•At this level, one‐loop effects from “heavy” physics

Compelling opportunity with high luminosity, polarized 11 GeV beam:

APV = 35.6 ppbδ(APV) = 0.73 ppb δ(QeW) = ± 2.1 (stat.) ± 1.0 (syst.) %

δ(sin2θW) = ± 0.00026 (stat.) ± 0.00012 (syst.) ~ 0.1%

Luminosity and Stability at Jlab upgrade makes feasible a factor of 5 improvement over E158

Λee ~ 25 TeV reach

not just “another measurement” of sin2θW  ; 0.0003 passes a threshold 

Purely leptonic reac+on

�

APV ∝meElab (1− 4sin2ϑW )

�

δ(sin2ϑW )sin2ϑW

≅ 0.05δ(APV )APV

�

σ ∝ 1Elab

Figure of Merit rises linearly with Elab

1‐loop EW Physics / Contact Interac+ons

20

102

103

0.23 0.232 0.234

sin2!

lept

eff

mH [G

eV]

"2/d.o.f.: 11.8 / 5

Al(SLD) 0.23098 ± 0.00026

A0,b

fb 0.23221 ± 0.00029

± 0.00029

Average 0.23153 ± 0.00016

had= 0.02758 ± 0.00035(5)

mt= 172.7 ± 2.9 GeV

1‐loop EW Physics / Contact Interac+ons

20

102

103

0.23 0.232 0.234

sin2!

lept

eff

mH [G

eV]

"2/d.o.f.: 11.8 / 5

Al(SLD) 0.23098 ± 0.00026

A0,b

fb 0.23221 ± 0.00029

± 0.00029

Average 0.23153 ± 0.00016

had= 0.02758 ± 0.00035(5)

mt= 172.7 ± 2.9 GeV

1‐loop EW Physics / Contact Interac+ons

20

This proposal

Powerful impact on Standard Model consistency in 1‐loop EW fit

102

103

0.23 0.232 0.234

sin2!

lept

eff

mH [G

eV]

"2/d.o.f.: 11.8 / 5

Al(SLD) 0.23098 ± 0.00026

A0,b

fb 0.23221 ± 0.00029

± 0.00029

Average 0.23153 ± 0.00016

had= 0.02758 ± 0.00035(5)

mt= 172.7 ± 2.9 GeV

1‐loop EW Physics / Contact Interac+ons

20

This proposal

Powerful impact on Standard Model consistency in 1‐loop EW fit

!!|g2

RR ! g2LL|

= 7.5 TeV

Le1e2 =!

i,j=L,R

g2ij

2!2ei!µeiej!

µej

Extremely sensi+ve to new physics at heavy mass scales

102

103

0.23 0.232 0.234

sin2!

lept

eff

mH [G

eV]

"2/d.o.f.: 11.8 / 5

Al(SLD) 0.23098 ± 0.00026

A0,b

fb 0.23221 ± 0.00029

± 0.00029

Average 0.23153 ± 0.00016

had= 0.02758 ± 0.00035(5)

mt= 172.7 ± 2.9 GeV

1‐loop EW Physics / Contact Interac+ons

20

This proposal

!!|g2

RR + g2LL|

= 4.4 TeV !gRL

= 5.2 TeV |g2RR ! g2

LL|

Best current limits on 4-electron contact interactions: LEPII at 200 GeV(Average of all 4 LEP experiments)

insensi+ve toOR

Powerful impact on Standard Model consistency in 1‐loop EW fit

!!|g2

RR ! g2LL|

= 7.5 TeV

Le1e2 =!

i,j=L,R

g2ij

2!2ei!µeiej!

µej

Extremely sensi+ve to new physics at heavy mass scales

g2RR ! g2

LL

!2=

e2R ! e2

L

M2Z!

! 1(7.5TeV)2

Example of Complementarity to LHC: Heavy Z’

21

•Most unified theories predict addi+onal neutral Z’•LHC can find these ~5 TeV, can determine proper+es 1‐2 TeV •11 GeV Moller can help pin down couplings

LHC can extract mass, width, and AFB to get constraint on 

     eR/eL

Moller sensi+vity:

Figure: F. Petriello & S. Quackenbush

eR/eL

eR2 ‐ eL2

New Challenges

22

• ~ 150 GHz sca0ered electron rate– Design to flip Pockels cell ~ 2 kHz

– 80 ppm pulse‐to‐pulse staDsDcal fluctuaDons

• Electronic noise and density fluctuaDons < 10‐5

• Pulse‐to‐pulse beam ji0er ~ 10s of microns at 1 kHz

• Pulse‐to‐pulse beam monitoring resoluDon ~ few micron at 1 kHz 

• 1 nm control of beam centroid on target– Modest improvement on control of polarized source laser transport elements

– Improved methods of “slow helicity reversal”

• > 10 gm/cm2 target needed to achieve desired luminosity– 1.5 meter Liquid Hydrogen target: ~ 5 kW @ 85 μA

• Full Azimuthal acceptance with θlab ~ 5 mrad– novel two‐toroid spectrometer

– radiaDon hard integraDng detectors

• Robust and Redundant 0.4% beam polarimetry– Plan to pursue both Compton and Atomic Hydrogen techniques

Two Toroid Spectrometer

x (m)−0.1 −0.05 0 0.05 0.1

y (

m)

−0.1

−0.05

0

0.05

0.1

0.006

0.008

0.01

0.012

0.014

0.016

0.018

z=6.00 m

x (m)−0.2 −0.15 −0.1 −0.05 0 0.05 0.1 0.15 0.2

y (

m)

−0.2

−0.15

−0.1

−0.05

0

0.05

0.1

0.15

0.2

0.006

0.008

0.01

0.012

0.014

0.016

0.018

z=9.00 m

x (m)−0.4 −0.3 −0.2 −0.1 0 0.1 0.2 0.3 0.4

y (

m)

−0.4

−0.3

−0.2

−0.1

0

0.1

0.2

0.3

0.4

0.006

0.008

0.01

0.012

0.014

0.016

0.018

z=14.50 m

x (m)−0.6 −0.4 −0.2 0 0.2 0.4 0.6

y (

m)

−0.6

−0.4

−0.2

0

0.2

0.4

0.6

0.006

0.008

0.01

0.012

0.014

0.016

0.018

z=20.00 m

x (m)−0.8 −0.6 −0.4 −0.2 0 0.2 0.4 0.6 0.8

y (

m)

−0.8

−0.6

−0.4

−0.2

0

0.2

0.4

0.6

0.8

0.006

0.008

0.01

0.012

0.014

0.016

0.018

z=24.00 m

x (m)−1 −0.8 −0.6 −0.4 −0.2 0 0.2 0.4 0.6 0.8 1

y (

m)

−1

−0.8

−0.6

−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

0.006

0.008

0.01

0.012

0.014

0.016

0.018

z=28.25 m

Radial Fields (edge effect) creates azimuthal defocussing which populates the full ring at the detector

1 meter radial focus, 30 meters from targetClean separa+on from backgrounds

PMTs

Air Light-guides

straggled primary beam to 5*theta_mscatt

shield

Lead

beam of neutrals from target

e+p

e+e

Target & Detectors

24

parameter value

length 150 cm

thickness 10.7 gm/cm2

X0 17.5%

p,T 35 psia, 20K

power 5000 WE158 scaNeringchamber

25

MOLLER collabra+on

The Parity Program at 11 GeV

26

Each experiment is a significant technical challenge•MOLLER:  high rate, low noise, beam asymmetries, backgrounds•PVDIS: fast coun+ng, backgrounds, detector development•BOTH: polarimetryBoth Experiments will have a big impact with important physics•Endorsed by NSAC Long Range Plan

Proposals were submiHed for each to the last PAC

APPROVED!

Next steps: Technical Design Review in late 2009 / early 2010 for MOLLER~1 year later for PVDIS

Moller and PVDIS apparatus in Hall A

These are big projects• 100+ authors on each proposal• Beam +me ~2 years each• Earliest +me to run 2015• Es+mated construc+on cost (together) ~25M$• Not part of the original JLab upgrade

Requires independent funding

Summary

27

0.001 0.01 0.1 1 10 100 1000

[GeV]

0.225

0.230

0.235

0.240

0.245

0.250

sin

2!

W

^ APV(Cs)

Qweak [JLab]

Moller [SLAC]

"-DIS

ALR

(had) [SLC]

AFB

(b) [LEP]

AFB

(lep) [Tevatron]

screening

antiscreening

Moller [JLab]

PV-DIS [JLab]

SM

current

future

µ

(µ)Precision electroweak physics is already being 

done at Jefferson Lab.

Future measurements in the 11 GeV JLab erawill be challenging but feasible, and present a tremendous opportunity to play a role in discovery in the LHC era.

28

29

30

Sensi+vity of proposed 11 GeV program

Cs

PVDIS

Qweak

6 GeV

PVDIS

Polarimetry

Compton Polarimetry

Need major effort to establish unimpeachable credibility for 0.4% polarimetry = two separate measurements, with separate techniques, which can be cross‐checked.

For scaHered electrons in chicane:two Points of well‐defined energy

• Asymmetry zero crossing• Compton Edge

Integrate between to minimize error on analyzing power

“independent” Photon analysis also normalizable at ~0.5%

0 500 1000 1500 2000 2500 30000

0.1

0.2

0.3

0.4

0.5

0.6

0.7 Ee=11GeVλ=532nm

k (MeV)

Cross‐sec+on

 (barn)

0 500 1000 1500 2000 2500 3000

−5

0

5

10

15

20

25

30

Asymmetry (%

)

k (MeV)

Ee=11GeVλ=532nm

31

High Precision ComptonAt high energies, SLD achieved 0.5%.

Why do we think we can do beHer?  

•SLD polarimeter near interac+on region ‐ background heavy•No photon calorimeter for produc+on

•Hall A has “coun+ng” mode (CW)•Efficiency studies•Tagged photon beam

• Greater electron detector resolu+on

So why haven’t we done beHer before?

0 10 20 30 40

−5

0

5

10

15

20

25

30

Design (4.5GeV)

PREX

H‐III

PV‐DIS

11 GeV

Distance from primary beam [mm]

Asymmetry

•Small asymmetries = long +me to precision = cross‐checks are difficult

•No one tried zero‐crossing technique (zero crossing gets hard near the beam)

•photon calorimetry gets tricky at small Eγ

32

High Precision ComptonAt high energies, SLD achieved 0.5%.

Why do we think we can do beHer?  

•SLD polarimeter near interac+on region ‐ background heavy•No photon calorimeter for produc+on

•Hall A has “coun+ng” mode (CW)•Efficiency studies•Tagged photon beam

• Greater electron detector resolu+on

So why haven’t we done beHer before?

0 10 20 30 40

−5

0

5

10

15

20

25

30

Design (4.5GeV)

PREX

H‐III

PV‐DIS

11 GeV

Distance from primary beam [mm]

Asymmetry

•Small asymmetries = long +me to precision = cross‐checks are difficult

•No one tried zero‐crossing technique (zero crossing gets hard near the beam)

•photon calorimetry gets tricky at small Eγ

Its a major effort and a full +me job, but there is no obvious fundamental show‐stopper

32

�

n+

n−= e−2µB / kT ≈ 10−14

Atomic Hydrogen For Moller TargetMoller polarimetry from polarized atomic hydrogen gas, stored in an ultra-cold magnetic trap

• 100% electron polarization

• tiny error on polarization

• thin target (sufficient rates but no dead time)

• Non-invasive

• high beam currents allowed

• no Levchuk effectE. Chudakov and V. Luppov, IEEE Transactions on Nuclear Science, v 51, n 4, Aug. 2004, 1533‐40Brute force polarization

10 cm, ρ = 3x1015/cm3 in B = 7 T at T=300 mK

33

34

CSV Theory and Data

MRST PDF global with fit of CSVMar+n, Roberts, S+rling, Thorne [Eur Phys J C35, 325 (04)]: 

90% conf limitBroad minimum

(90% C.L.)

fully explains NuTeV

doubles NuTeV deviation

Analy+c calcula+on similar to global fit

35

Analysis ofBlumlein and

Botcher

F2 dominates the cross sec+on

Best HT Data

Higher twist is clearlyseen at the PVDIS 

kinema+cs.  

36

QWeakMeasuring the proton form-factor weak charge

Small angle, low Q2 ∼ 0.03 GeV2 to suppress target structureProton structure F, constrained by strange quark program, contributes ~30% to asymmetry, ~2% to δ(QW

p)/ QWp

36

QWeakMeasuring the proton form-factor weak charge

Small angle, low Q2 ∼ 0.03 GeV2 to suppress target structureProton structure F, constrained by strange quark program, contributes ~30% to asymmetry, ~2% to δ(QW

p)/ QWp

�

APV ≈ −230 ± 5 ± 4 ppb

�

δ QWp = ± 4% ⇒ δ(sin2θW ) = ± 0.3%

36

QWeakMeasuring the proton form-factor weak charge

Small angle, low Q2 ∼ 0.03 GeV2 to suppress target structureProton structure F, constrained by strange quark program, contributes ~30% to asymmetry, ~2% to δ(QW

p)/ QWp

A new standard in precision• New Spectrometer system• Control and correction for beam systematics• Polarimetry approaching 1% (new)• Low system noise - 6.5 GHz rate!• High rate, radiation hard readout• Background and calibration precision

mid‐2010 through 2011

�

APV ≈ −230 ± 5 ± 4 ppb

�

δ QWp = ± 4% ⇒ δ(sin2θW ) = ± 0.3%

37

PVDIS on the Proton: d/u at High x

Deuteron analysis has largenuclear corrections (Yellow)

APV for the proton has no such corrections

(complementary to BONUS)

The challenge is to get statistical and systematic errors ~ 2%

3-month run

38

CSV in Heavy Nuclei: EMC Effect

Addi+onal possible

applica+on of SoLID

Isovector‐vector mean

field.  (Cloet, Bentz,

and Thomas)

5%