X. Zheng, PAVI06, Milos, Greece Massachusetts Institute of Technology Parity Violation in Deep Inelastic Region at JLab 6 GeV — Experiment 05-007 – Motivation,

X. Zheng, PAVI06, Milos, GreeceMassachusetts Institute of Technology

Parity Violation in Deep Inelastic Region at JLab 6 GeV

— Experiment 05-007

– Motivation, PVDIS, Implication on EW standard model and hadronic physics;

– Requirement on Instrumentation and Status

– Summary and Outlook

Xiaochao ZhengMassachusetts Institute of

TechnologyMay 19, 2006


Observables — parity violating asymmetries (APV)

(polarized beam + unpolarized target)

study nuclear matter (neutron skin) PREx

study hadron structure

elastic scattering: strange form factors A4, G0, HAPPEX, SAMPLE

DIS: non-perturbative higher twist effects, etc... PVDIS

test EW standard model E158, Atomic PV, Qweak

Parity Violation in Electron Scattering

ALR≡

r− l

r l≈

Q2

MZ

2≈120 ppm at Q2=1GeV /c2


SM works well at present energy range, however:

Data exist: cannot be explained by the SM ( m? NuTeV

anomaly?..);

Conceptual reasons: What happens in the “high-energy desert” (250GeV ~ 5 x 1014 GeV ~ 2.4 x 1018 GeV)?

Search for Physics beyond the Standard Model

Direct: LEP, LHC

Indirect: E158, Atomic PV, NuTeV, Qweak, PVDIS

Electro-Weak Standard Model


From Ad can extract C1,2q and sin2W.

PV DIS Asymmetries

For a deuterium target

In the SM, tree level

Ad= 540 ppmQ2

2 C1u[1R

C x ]−C

1d[1R

S x ]Y 2 C

2u−C

2dR

V x

5RS x 4 R

C x

C1d=g

A

e gV

d =1

2−

2

3sin2

W

C1u=g

A

e gV

u =−1

2

4

3sin2

W

C2d=g

V

e gA

d =1

2−2 sin2

W

C2u=g

V

e gA

u =−1

22 sin2

W

Rc,Rs,Rv: nucleon PDF; Y: kinematic factor


DIS Parity Experiment – History and Future

1970's, result from SLAC E122 consistent with sin2W=1/4, confirmed

the Standard Model prediction;C.Y. Prescott, et al., Phys. Lett. B77, 347 (1978)

Development in experimental technique allows to search for new physics

If all hadronic effects are small or can be understood, then any deviation of sin2W or Ciq from their SM predictions would be a hint of

new physics.

P. Bosted, et al., SLAC E149 (1993), LOI2003-1;


Current Knowledge on Weak Coupling Coeffecients

Facility Process Result SM Value

SLAC 1.39 -0.7185

SLAC 1.39 -0.0983

CERN 34 1.4351

CERN 66 1.4204

MAINZ 0.20 -0.8544

Bates 0.0225 0.1528

Bates 0.1 -0.0624

Bates 0.04 -0.0624

JLab 0.03 approved 0.0357

0 -73.16

0 -116.8

Q2 Ciq Combination

e--D DIS 2C1u-C1d -0.90± 0.17

e--D DIS 2C2u-C2d 0.62± 0.81

m±-D DIS 0.66(2C2u-C2d)+2C3u-C3d 1.80± 0.83

m±-D DIS 0.81(2C2u-C2d)+2C3u-C3d 1.53± 0.45

e--Be QE 2.68C1u-0.64C1d+2.16C2u-2C2d -0.94± 0.21

e--C elastic 2C1u+C1d 0.138±0.034

e--D QE C2u-C2d -0.042± 0.057

e--D QE C2u-C2d -0.12± 0.074

e--p elastic 2C1u+C1d

133Cs APV -376C1u-422C1d -72.69±0.48205Tl APV -572C1u-658C1d -116.6±3.7

J. Erler, M.J. Ramsey-Musolf, hep-ph/0404291 or Prog. Part. Nucl. Phys. 54, 351 (2005)

C2q=g

V

e gA

q C3q=g

A

e gA

qC1q=g

A

e gV

q


JLab Experiment 05-007

Use 85mA, 6 GeV, 80% polarized beam on a 25-cm LD2 target;

Two Hall A High Resolution Spectrometers (HRS) detect scattered electrons;

Measure Ad at Q2=1.10 and 1.90 GeV2 to about 2% (stat.);

Co-spokesperson & contact: X. Zheng (MIT)Co-spokesperson: P.E. Reimer (ANL), R. Michaels (JLab)

(Hall-A Collaboration Experiment, approved by PAC27, rated A-)

ANL, Calstate, FIU, Jlab, Kentucky, U. of Ljubljana (Slovenia), MIT, UMD, UMass, UNH, Universidad Nacional Autonoma de Mexico, Rutgers, Smith C., Syracuse, UVa,

W&M


From Ad at Q2=1.90 (GeV/c)2, can

extract (2C2u-C2d) to ±0.03 — order

of magnitude improvement compared to world data (PDG);

provide constraints on new physics up to 1 TeV mass limit (complementary to Qweak, E158);

Z' Searches; Compositeness; Leptoquarks.

help to extract C3q

= gA

egA

q from CERN

m±-DIS data

E05-007 Physics Goals

Ad=

3GF

Q2

2 2

2 C1u[1R

C x ]−C

1d[1R

S x ]Y 2 C

2u−C

2dR

V x

5RS x 4 R

C x

(for review of new physics from PVES:J. Ramsey-Musolf, et al., hep-ph/0001250; hep-ph/0307270; nucl-th/0501023;

SM


To cleanly separate higher-twist (HT) from New Physics will require precision measurement at various kinematics, and we are making the first step now;

Existing models show negligible HT effects;

Ad at Q2=1.10 (GeV/c)2 will help to investigate if there are significant

HT effects:

Will help to investigate the HT contribution to the NuTeV anomaly:

May provide “clean” extraction of HT, and help with DIS analysis:

extract S at low Q2 from DIS data — test pQCD and understand

confinement.

Will provide important guidance for the future PVDIS program;

E05-007 Physics Goals


If 80% of this deviation is from HT, it would imply a 6% HT contribution to our Ad at Q2 = 1.9 and 10% at Q2 = 1.1 (GeV/c)2, way larger than our

expected error bar;

The NuTeV Anomaly

and Higher Twist

sin2W reported by NuTeV is 3s

away from SM;

Possible hadronic causes: CSV, strange sea asymmetry, HT, etc.

M. Gluck and E. Reya, Phys. Rev. Lett. 47, 1104 (1981);also: G.A. Miller & A.W. thomas, hep-ex/0204007

G.P. Zeller et al, PRL88,091802(2002)

T. Londergan, PAVI06 E158: P.L. Anthoney et al., PRL95, 081601 (2005)Cs-APV: S.C. Bennett, C.E. Wieman, PRL82,2484(1999)


Extraction of S at Low Q2 and Higher Twist

S extracted from Bjorken sum rule

at low Q includes HT;

HT from DIS (F2, g1...) — difficult to separate from higher order effects;

HT from PVDIS:

Leading Twist unambiguously determined by the SM;

More precise than polDIS;

If can use PVDIS HT for low Q DIS analysis, then may correct HT and compareS with pQCD predictions

® Test standard model of strong interaction.

A. Deur, V. Burkert, J.P. Chen, W. Korsch, hep-ph/0509113

Perhaps PVDIS can serve as a (powerful?) tool to study some long-lasting problem in hadronic physics — HT, d/u, anything else???

Ad=AdSM1

C4HT

Q 2


EXPERIMENTALHALLS

INJECTOR

RECIRCULATIONARCs (Magnets)

NORTHLINAC SOUTH

LINAC

CBA

“parity-quality”beam since 1998K. Paschke, PAVI06

The Accelerator at Jefferson Lab, Virginia, USA


Experimental Hall A


PV-DIS (E05-007) Requirements and Status


PV-DIS (E05-007) Requirements and Status

upgrade from IR to green laser to provide 1% precision

upgrade to flash-ADC based DAQ to count 1MHz rate


Compton Polarimetry

Compton polarimeter: measure asymmetry of Compton scattering of electron beam and high power laser (Fabry-Pérot cavity);

Non-invasive, high current capacity;

Currently using: 200mW 1064nm laser;

Difficult for < 2GeV beam;

Providing 2-3% precision for 4 GeV beam, larger for <4 GeV;

see also: J. Diefenbach, PAVI06


Present UpgradeWavelength(nm) 1064 532Cavity Power (W) 1500 3000

Upgrade required by: PVDIS, PRex, 12 GeV

Upgrade includes:

from IR to Green (532nm) laser, completely new optics including the Fabry-Pérot cavity, factor of 4 increase in FOM — JLab;

Green Compton Upgrade

new electron detectors (narrower micro-strip) to improve resolution — Univ. of Clement-Ferrand;Photon integration method — improve systematics (JLab);

Will provide 1% precision down to 1 GeV beam energy;

(PRex) R. Michaels, PAVI06


Green Compton Lab


Green Compton Optics Setup

CurrentlyIn Progress


Green Compton Cavity Alignment


Green Compton Optics Setup

Green laserwith safty cover FOI

L1QWP

PA510

L2

Aiming in cavity locking July/August 2006.


DAQ Upgrade

Current Hall A HRS DAQ:

Max event rate 4KHz (VDC limited);

Previous Hall A PV Experiments (HAPPEX) used Integrating DAQ

Will not work for DIS (large pion background);

Flash ADC (FADC) based DAQ is required:

FADC: 250MHz main sampling rate with on-board processor (FPGA);

Provide on-board fast PID on a counting basis up to 1MHz;

Full event information sampled at lower rate for cross-check;

Can be used for other high rate experiments.


FADC DAQ on HRS

Inputs:

Scintillators (S1, S2, 12 channels each);

Gas cherenkov (GC,10CH);

Lead glass counter (“Pre-shower” 48CH, “Shower” 80CH);


FADC DAQ on HRS

On-board Processing:

S1+S2 for track quality evaluation;sum GC, Lead glass for PID;segments GC and Lead glass blocks for pile-up rejection;pile-up separation (signal shape analysis);

Shower sum

pions

electrons

Outputs:

helicity-gated electron and pion counts (per ~second);full event sampling at low rate for quality control, including pile-up events for further off-line evaluation;cross check with regular DAQ at low event rate (<4KHz);

Pre

-Sho

wer

sum

Regular DAQ Spectrum


Status:

Preliminary test using a 100 MHz module (no processor built-in) completed — design algorithm, signal shape analysis (Oct.2005):

Specification/algorithm provided to JLab DAQ group — Dec 2005;

First prototype will be available in summer 2006, more tests will follow;

Expect to completely test the full system in late 2007.

Schedule of E05-007:

Phase I (13 days) approved, will run in late 2008 – early 2009;

Will re-propose phase II (33 days) soon, hopefully will complete both at the same time;

FADC DAQ on HRS


The approval of E05-007 started the PV-DIS program @ JLab:

SM test, precision C2q and sin2W

(complimentary to other HEP and Nuclear experiments)

Study of hadronic effects:

Higher-twist study (low Q2 S , test pQCD);

Using a proton target: measure PDF ratio d/u at high x;

Measure Charge Symmetry Violation (CSV).

Leading program @ 12 GeV upgrade (2012?~)

Future of PV-DIS at JLab

JLab Hall A pCDR

P.E. Reimer, PAVI06


Summary

PV-DIS is a powerful tool to test the Standard Model and to study many interesting hadronic effects:

C2q's, sin W;

low Q2 S , d/u at high x, higher twist... Anything else?

This program will start soon at JLab (E05-007):

Two major instrumentation need to be upgraded, in progress;

Will run in late 2008-2009;

extract (2C2u-C2d) to ±0.03, factor of 8 improvement w.r.t PDG;

first HT extraction from PVDIS.

Will be one of the leading experiments of JLab 12 GeV.


Experimental Hall A


The CollaborationA. Afanasev, D.S. Armstrong, J. Arrington, T.D. Averett, E.J. Beise,

W. Bertozzi, P.E. Bosted, J.R. Calarco, G.D. Cates, J.-P. Chen, E. Chudakov, P. Decowski, A. Deur, J. Erler, R. Feuerbach, J.M. Finn,

O. Gayou, S. Gilad, R. Gilman, C. Glashausser, K.A. Griffioen, K. Hafidi,J.-O. Hansen, R. Holmes, R.J. Holt, T. Holmstrom, H.E. Jackson, X.

Jiang,W. Korsch, K. Kumar, N. Liyanage, D.J. Mack, D.J. Margoziotis, P. Markowitz, R. Michaels (co-spokesperson), P. Monaghan,

V. Nelyubin, K. Paschke, D.H. Potterveld, A.J. Puckett, Y. Qiang, R. Ransome, P.E. Reimer (co-spokesperson), B. Reitz, E.C. Schulte, J. Singh, S. Sirca, R. Snyder, P. Souder, V. Sulkosky, W.A. Tobias,

B. Zeidman, X. Zhan, X. Zheng (spokesperon)The Hall A Collaboration

ANL, Calstate, FIU, Jlab, Kentucky, U. of Ljubljana (Slovenia), MIT, UMD, Umass, UNH, Universidad Nacional Autonoma de Mexico, Rutgers, Smith C.,

Syracuse, Uva, W&M

We have strong support from theorists and experts of parity experiments.


Beam Time Allocation for Running In Two Phases

Phase I: 13 days

4 days of commissioning and systematic checks including:

Commissioning fast counting DAQ and Compton

9 days with the HRS-L at Q2=1.10 (GeV/c)2 and the HRS-R at Q2=1.90 (GeV/c)2

Phase II: 33 days

complete both Q2 measurements.

Approved (Jan.2005), rated A-


Data Analysis

Electron asymmetries

3He asymmetries

From 3He to Neutron

Araw=N p /Q p−Nm /Q m

N p /Q pNm /Q m

Aparallel ,perp=A raw

f PbPt


Exploring Nucleon Structure Using EM Probe (cont.)

elastic

quasi-elastic

resonances

DIS

The nucleon changes its appearance with the way we study it, and we have developed different models/languages for each facet;However, all of them shall form a coherent picture, and perhaps one day all these aspects can be unified within QCD.


Scaling Violation in QCDBjorken limit: , xBj fixed, (strict) one photon exchange

no scale (Q2 )dependence, scaling

High , soft gluon emission, logQ2 dependence

Low , hard gluon emission 1/(Q2)(t-2) dependence “higher-twist effects”

Q2∞

Q2 0

Q2


Structure Functions in the Quark-Parton Model

After 35 years of DIS experiments, the unpolarized structure of the nucleon is reasonably well understood (for moderate xBj

region).

F1 x =

1

2 e

i

2 [qi x ] in the infinite momentum frame

(IMF)

(P ® ∞)


Jlab 6 GeV


Upgrade magnets Upgrade magnets and power and power suppliessupplies

CHL-2CHL-2

Jlab 6 GeV12

Add new hallAdd new hall

Enhance equipment Enhance equipment in existing hallsin existing halls


Design on-board algorithm;Event pile-up at 3% level at 1MHz (e-e pileup <1%), on-board identification possible;

Preliminary test using 100MHz module and 1-2 CH/detector (Oct.2005):

Gas cherenkov (10 ch sum)

Pre-shower (2ch sum) Shower (1ch)

First FADC Test and Design for Algorithm


Extraction of S at Low Q2 and Higher Twist

A. Deur, V. Burkert, J.P. Chen, W. Korsch, hep-ph/0509113

S extracted from Bjorken sum rule

at low Q includes HT;

HT from DIS (F2, g1...) — difficult to separate from higher order effects;

HT from PVDIS:

Leading Twist unambiguously determined by the SM;

More precise than polDIS;

If can use PVDIS HT for low Q DIS analysis, then may correct HT and compareS with pQCD predictions

® Test standard model of strong interaction.

Perhaps PVDIS can serve as a (powerful?) tool to study some long-lasting problem in hadronic physics — HT, d/u, anything else???

Prelim

inary

!


The Accelerator at Jefferson Lab, Virginia, USA

X. Zheng, PAVI06, Milos, Greece Massachusetts Institute of Technology Parity Violation in Deep Inelastic Region at JLab 6 GeV — Experiment 05-007 – Motivation,

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