1

The Physics of Jefferson Lab 12 GeV Upgrade

Xiaochao Zheng (Univ. of Virginia)

Nov. 3, 2010

Jefferson Lab: its mission and current status

The Physics from 6 to 12 GeV: A few selected topics

Current status of the Upgrade

Summary and Outlook

2

Scientific Mission

In 1985:In 1985:

How are hadrons constructed from quarks and gluons of QCD?

What is the QCD basis for the nucleon-nucleon force?

Where are the limits of our understanding of nuclear structure? Where does the transition from nucleon-meson to QCD quark-gluon description occur?

Today also include:Today also include:

What is the mechanism of confinement? How does Chiral symmetry breaking occur?

Symmetry Tests in Nuclear Physics

3

JLab Accelerator (Present)

20 cryomodules

End Stations with complementary equipments

Recirculation arcs

HeliumRefrigerator

0.4-GeV linac

45 MeVInjector

20 cryomodules

State-of-art, superconducting RF cavities, combined with polarized electron source, provide high intensity, yet continuous-wave polarized beam for the past 15 years.

4

Structure of the Nucleon

Nucleon Electromagnetic Form Factors

d

d E , =

M [ GE

2 Q 2GM

2 Q2

12 G

M

2 tan 2 /2 ] M=

2 E ' cos2 / 2

4 E 3sin 4 /2 ∝

1

Q4

GE

p

GM

p= −

Pt

Pl

EE '

2 Mtan /2

5

Before JLab and Recent non-JLab Data

Fig

ure

cred

it: S

. Rio

rdan

JLab Data on the EM Form Factors Provide a Testing Ground for Theories Constructing Nucleons from Quarks and Glue

6

Today, with JLab 6 GeV Data, compared with theory

Fig

ure

cred

it: S

. Rio

rdan

JLab Data on the EM Form Factors Provide a Testing Ground for Theories Constructing Nucleons from Quarks and Glue

Inferences to date:Relativity essentialQuark angular momentum importantPion cloud makes critical contributions

7

JLab Data on the EM Form Factors Provide a Testing Ground for Theories Constructing Nucleons from Quarks and Glue

Today, with JLab Data

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JLab Data on the EM Form Factors Provide a Testing Ground for Theories Constructing Nucleons from Quarks and Glue

with JLab 12 GeV expected results

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Structure of the Nucleon

Valence Quark Structure

Model prediction at x=1 d/u

2/ 3 1/ 2 2/ 3 -1/ 3 0 5/ 9

Valence Quark + Hyperfi ne 1/ 4 0 1 -1/ 3 1 1

3/ 7 1/ 5 1 1 1 1

F2

n/F2

pD u/u D d/d A

1n A

1p

SU(6) = SU3 fl avor + SU2 spin

pQCD + HHC

x=Q 2

2 M

10

After 35 years: Miserable Lack of Knowledge of Valence d-Quarks

pQCD(Helicity

Conservation)

di-quarkcorrelations

SU(6)

Unpolarized Parton Distribution Function in the Valence Quark Region

11

>70MeV/c

BONUS Detector

F2n/F2p ratio by tagging almost unbound neutrons using detection of low momentum protons in a radial time projection chamber (BONUS).

e-D→e-psX

n

ps

pe-

e-

First model-independent measurement of F2n/F2p and F2n . At 12 GeV F2n will be measured up to xB =0.85.

CLASCLAS Neutron structure in spectator tagging

pQCD(HHC)

di-quark

SU(6)

SLAC (PLC suppression)SLAC (PLC suppression)SLAC (Fermi corrected)

CTEQ6X

F 2n

F 2p≈

14 d /u4d /u

BoNUS preliminary

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Hall A 11 GeV with Super BigBite + HRS, 3H/3He DISwith SoLID proton target

PVDIS

Hall B 11 GeV with CLAS122H w/ recoil detection

HelicityConservation

Unpolarized Parton Distribution Function in the Valence Quark Region

pQCD (HHC)di-quark correlations

SU(6)

d/u

0.2 0.4 0.6 0.8 1.0x 0.2 0.4 0.6 0.8 1.0

0.6

0.5

0.4

0.3

0.2

0.1

0

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Valence Polarized Structure Functions and PDFs

Before JLab

di-quark

pQCD(HHC)

SU(6)

pro

ton

A1p

neu

tron

A1n

di-quarkSU(6)

pQCD(HHC)

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pQCD with HHC

RCQMRCQM

RCQMRCQM

Valence Polarized Structure Functions and PDFs

with JLab 6 GeV data

pro

ton

(C

LA

S

2006)

CQM LSS(BBS):pQCD+HHCStatistical Model LSS 2001

1.0

0.5

0

neu

tron

(H

all A

2004)

1.0

0.5

0

-0.5

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pQCD with HHC

RCQMRCQM

RCQMRCQM

Valence Polarized Structure Functions and PDFs

with JLab 6 GeV data

pro

ton

(C

LA

S

2006)

CQM LSS(BBS):pQCD+HHCStatistical Model LSS 2001

1.0

0.5

0

neu

tron

(H

all A

2004)

1.0

0.5

0

-0.5

HHC not valid,quark OAM?

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H. Avakian, S. Brodsky, A. Deur, F. Yuan, Phys. Rev. Lett.99:082001(2007)

Figure credit: A. Deur

Polarized Structure Functions and PDFs in the Valence Quark Region

17

Polarized Structure PDFs in the Valence Quark Region at JLab

12 GeV

Neutr

on

(H

all

C)

Dq/q

with JLab 12 GeV projected results

Pro

ton

(C

LAS1

2)

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3D Imaging of the NucleonGPDs and TMDs

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Beyond form factors and quark distributions –

Generalized Parton Distributions (GPDs)

Proton form factors, transverse charge & current densities

Structure functions,quark longitudinalmomentum & helicity distributions

Correlated quark momentum and helicity distributions in transverse space - GPDs

4 GPDs:

X. Ji, D. Mueller, A. Radyushkin (1994-1997)

H x , , t , E x , , t , H x , ,t , E x , , t

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GPDs

Transverse momentum of partons

Quark spin distribution

s

Form factors(transverse

quark distributions)

Quark longitudinal momentum

distributions

Pion clou

d

Pion distributio

n amplitude

s

Quark angular

momentum

Beyond form factors and quark distributions –

Generalized Parton Distributions (GPDs)

J q=12qLq

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Jd

Ju

PPRL99, 242501 (2007)

GPDs: Results from JLab 6 GeV and Elsewhere

Remaining JLab 6 GeV programHall B (relative asymmetries)ALU, AUL , DVCS on He4: data taken (2009-2010), analysis on-goingAUT (HD-ice) : experiment to be scheduledHall A (absolute cross-sections): LH2 and LD2 targets, data taking fall 2010.Rosenbluth-type separation of BH2 and DVCS-BH interferenceL/T separation of the deeply virtual 0 production

Compass data with muon beam (~2013)

Deeply Virtual Compton Scattering: The simplest process that can be described by GPDs

model dependent analysis

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Projected results (CLAS12)

Projected precision in extraction of GPD H at x =

Spatial Image

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Parity Violating Electron Scattering at JLab

Weak Neutral Current (WNC) Interactions at Q2 << MZ2

Longitudinally Polarized Electron Scattering off Unpolarized Fixed Targets

∝∣AAweak∣2

Asym≈100 ppm Q2

GeV 2

longitudinallypolarized

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“Parity Quality” of JLab polarized beam

Beam Parameter HAPPEx-I HAPPEx-II PREX

Charge asymmetry < 0.1 ppm 0.41 ppm 200 ppb

Position difference

-11±2.3 nm,-10±1.0 nm

0.56±0.53 nm, 1.69±0.83 nm

2 nm

angle difference 0.2±0.6 nrad, 3±0.2 nrad

-0.26±0.24 nrad, 0.21±0.25 nrad

1 nrad

Energy difference -4±1 ppb 0.2ppb (0.6 eV) 1 eV

Total correction -0.02 ± 0.02 ppm

0.08 ± 0.03 ppm

HAPPEx-II (2005): • superlattice

(PB>85%)

• 35 A

e ePREX (2010): • superlattice

(PB>85%)

• 50-100 A

HAPPEx-I (1999): • strained GaAs

(PB~69%)

• 40 A beam current

High “parity-quality”, negligible uncertainties due to beam; Most of 6 GeV experiments measured strange quark

contribution to proton form factors: less than 5% to GEp and

less than 20% to GMp

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Quark Weak Neutral Couplings

C 1i≡ 2 g Ae g V

i

A

V

V

A

C 2i≡2 g Ve g A

i

Vector quark coupling Axial-vector quark coupling

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SAMPLE

C2

u+C

2d

1.25

1.5

1.75

1.0

0.75

0.5

0.25

0

0.25

-0.5

-0.75

C2u-C2d

- 0.25 0.50.250- 0.5

SAMPLE

C2

u+C

2d

1.25

1.5

1.75

1.0

0.75

0.5

0.25

0

0.25

-0.5

-0.75

C2u-C2d

- 0.25 0.50.250- 0.5

Quark Weak Neutral Couplings C1,2q

without recent PVES data without JLab data

all are 1 limit

PDG best fit

SLAC/ Prescott

PDG best fit

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SAMPLE

C2

u+C

2d

1.25

1.5

1.75

1.0

0.75

0.5

0.25

0

0.25

-0.5

-0.75

C2u-C2d

- 0.25 0.50.250- 0.5

SAMPLE

C2

u+C

2d

1.25

1.5

1.75

1.0

0.75

0.5

0.25

0

0.25

-0.5

-0.75

C2u-C2d

- 0.25 0.50.250- 0.5

HAPPEx: H, HeG0: H, PVA4: HSAMPLE: H, D

Quark Weak Neutral Couplings C1,2q

with recent PVES data without JLab data

all are 1 limit

PDG best fit

SLAC/ Prescott

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SAMPLE

C2

u+C

2d

1.25

1.5

1.75

1.0

0.75

0.5

0.25

0

0.25

-0.5

-0.75

C2u-C2d

- 0.25 0.50.250- 0.5

Factor of 5 increase in precision of Standard Model test

PRL99,122003(2007)

Quark Weak Neutral Couplings C1,2q

with recent PVES data without JLab data

all are 1 limit

PDG best fit

SLAC/ Prescott

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SAMPLE

C2

u+C

2d

1.25

1.5

1.75

1.0

0.75

0.5

0.25

0

0.25

-0.5

-0.75

C2u-C2d

- 0.25 0.50.250- 0.5

Quark Weak Neutral Couplings C1,2q

with recent PVES data and Qweak without JLab data

all are 1 limit

PDG best fit

SLAC/ Prescott

Qweak in Hall C (2010-): another factor of 5 improvement in knowledge of C1q, New Physics scale from 0.9 to 2

TeV

1H + e e’ + p

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Quark Weak Neutral Couplings C1,2q

with recent PVES data and Qweak with JLab 6 GeV

all are 1 limit

SAMPLE

SLAC/ Prescott

C2

u+C

2d

1.25

1.5

1.75

1.0

0.75

0.5

0.25

0

0.25

-0.5

-0.75

C2u-C2d

- 0.2 0.40.20- 0.4

PVDIS in Hall A (Oct-Dec 2009): potential to improve C2q

knowledge if hadronic effects are small.

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SAMPLE

R. Young (combined)

all are 1 limit

PVDIS with 11 GeV beam and SoLID spectrometer in Hall A: potential to improve C2q knowledge by another order of magnitude

and better separation from hadronic effects.

Knowledge on C1,2q with Projected JLab 12 GeV Results

C2u-C2d

C2

u+C

2d

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Nee ~ 25 TeV

JLab MøllerLHC

New Contact Interactions

Møller Parity-Violating Experiment: New Physics Reach

(a large installation experiment with 11 GeV beam energy)

Czarnecki and Marciano (2000)Erler and Ramsey-Musolf (2004)

Expected precision comparable to the two most precise measurements from colliders, but at lower energy.

No other experiment with comparable precision in the forseeable future!

12 GeV

12 GeV

6 GeV

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Search for Gluonic Degree of Freedom – predicted by theories of confinement

34

Gluonic Excitations and the Origin of Confinement

Flux-tubes – a possible mechanism of confinement – comes

naturally from self-interaction nature of gluons in QCD.

PRD31, 2910 (1985)PLB124,247 (1983)

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Gluonic Excitations and the Origin of Confinement

Flux-tubes – a possible mechanism of confinement – comes

naturally from self-interaction nature of gluons in QCD.

ground state

1st excitation: /r ~ 1 GeV

Jpc = 1-+

PRD31, 2910 (1985)PLB124,247 (1983)

This gluonic degree of freedom predicts glueballs and hybrid

mesons, with exotic quantum numbers. Yet no solid observation

of these states.

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Gluonic Excitations and the Origin of Confinement

PRD82:034508 (2010)

Lattice QCD gives

more detailed

predictions

exotics

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q

q

afte

rq

q

befo

re

beam

With the upgraded CEBAF, a linearly polarized photon beam, and the GlueX detector, Jefferson Lab will be uniquely poised to: - discover these states- map out their spectrum - measure their properties

Searching for Gluonic Excitations in Hall D

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For many physics topics such as GPDs, valence quark structure, PVDIS etc., 6 GeV experiments have demonstrated the feasibility of measurements in a regime that we have barely touched.

For some topics such as Moller and searching for gluonic degree of freedom, we have not yet started.

Our pursuit of these topics rely on the higher beam energy and more sophisticated equipment of the JLab 12 GeV Upgrade.

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NSAC 2007 Long Range Plan

Recommendation I

“We recommend completion of the 12 GeV Upgrade at Jefferson Lab. The Upgrade will enable new insights into the structure of the nucleon, the transition between the hadronic and quark/gluon descriptions of nuclei, and the nature of confinement.”

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ONGOING CONSTRUCTION EFFORTS

Hall D - Central Drift Chamber Endplates @ CMU

Hall C – Drift Chambers @ HU & Scintillators @ JMU

Hall B - Drift Chambers @ JLab,

ODU and ISU

12 GeV Groundbreaking

(Apr2010

)

Hall D Concrete Wall Erection

(Apr 2009)

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The Hadron spectra as probes of QCDThe transverse structure of the hadrons The longitudinal structure of the hadronsThe 3D structure of the hadronsHadrons and cold nuclear matterLow-energy tests of the Standard Model and Fundamental Symmetries

Jefferson Lab is fulfilling its scientific mission. Its 12 GeV Upgrade is well underway and will greatly enhance its scientific reach. 32 proposals already approved and program already established in:

Summary and Perspectives

Beam off 2012 for the upgrade. Hall commissioning (experiments start) 2013-14,.

Stay tuned!Stay tuned!PAC37 (Jan 2011) new PAC37 (Jan 2011) new

proposal welcome, come join proposal welcome, come join us!us!

Plan for the next “upgrade”!Plan for the next “upgrade”!

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Backup Slides

43

44

12 GeV Upgrade Physics InstrumentationGLUEx (Hall D): exploring origin of confinement by studying hybrid mesons

CLAS12 (Hall B): 3D imaging of the nucleon via generalized parton distributions

SHMS (Hall C): precision determination of valence quark properties in nucleons and nuclei, form factors

Hall A: short range correlations, form factors, hypernuclear physics, & new “installation” experiments (SBS, Møller, SOLID,…..)

45

The Upgrade to the accelerator can be done in a relatively cost-efficient way.

12 GeV Upgrade Accelerator

46

Staff: ~650

User community: ~1300

A CB

47

Three Experimental Halls (Present)Hall A:pair of high resolution spectrometers (HRS), E' up to 4 GeV/c, = 7 msrluminosity up to 1039 cm-2 s-1

Hall C:High Momentum (HMS and Short-Orbit Spectrometers (SOS)luminosity up to 1039 cm-2 s-1

Hall B:CEBAF Large Acceptance Spectrometer (CLAS) luminosity up to 1034 cm-2 s-1

48

Topics not covered in this Talk

6 GeV: GDH sum rule, short-range correlation, PRIMEX,

Hadron spectroscopy (N* program)

Hadrons and cold nuclear matter(Medium modification of the nucleons, quark hadronization, N-N correlations, hypernuclear spectroscopy, few-body experiments)

49

Beam was first delivered in 10/95

In full operation for ~13 years (since 11/97);

283 PRL and PL to date: ½ expt, ½ theory)

334 PhDs to date and 249 in progress (~1/3 of US PhDs in Nuclear Physics)

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Facilities Accelerator Beam Time

low 1995 - ... ...

SLAC Stanford Linear Accelerator 1962 - ... ... 0.03%

“CW”

CERN low 1989-2000

DESY low

MAINZ 1979 - ... ... “CW”

MIT Bates MIT Bates Linear Accelerator 1975-2005

Energy, polarization

Luminosity (cm-2 s-1)

duty factor

FermiLab Tevatron 1.96 TeV

50 GeV, 80% 1036

J LabContinuous Electron Beam Accelerator Facility (CEBAF)

6 GeV, 85% 12 GeV, 85%

1038-39 1985 - ... ... 2015 - ... ...

Large e-/e+ Collider (LEP) 90-209 GeV

Deutsches Elektronen Synchrotron 27.5 GeV 1987 - ... ... (DESY-II)

Mainz Microtron MAMI 0.8/1.6 GeV 1038

0.8 GeV 1037

Medium & High Energy Physics Facilities for Lepton Scattering

e−.

e−.

e−. ,e.

,

e−. ,e.

,

e−. ,e.

High luminosity, yet “continuous” polarized beam makes JLab an unique facility.

~ns: “continuous”>>ns: “pulsed”

51

Today, with JLab Data

Fig

ure

cred

it: S

. Rio

rdan

JLab Data on the EM Form Factors Provide a Testing Ground for Theories Constructing Nucleons from Quarks and Glue

52

Main Physics Programs:

Nucleon structure functions in the valence quark region;

Nucleon form factors (electromagnetic and strange);

Hadronic-Partonic transition: Sum rules and duality;

Hadron spectroscopy;

Nuclear Physics:

form factor and structure of light nuclei

nuclear medium effects (“EMC” effects)

Standard Model test (parity violation in electron scattering)

... ...

53

“Classification” Categories to be Used for the Assignment of Scientific Priority to the 12 GeV

Experiments

The Hadron spectra as probes of QCD(GluEx and heavy baryon and meson spectroscopy)

The transverse structure of the hadrons (Elastic and transition Form Factors)

The longitudinal structure of the hadrons (Unpolarized and polarized parton distribution functions)

The 3D structure of the hadrons(Generalized Parton Distributions and Transverse Momentum Distributions)

Hadrons and cold nuclear matter(Medium modification of the nucleons, quark hadronization, N-N correlations, hypernuclear spectroscopy, few-body experiments)

Low-energy tests of the Standard Model and Fundamental Symmetries(Møller, PVDIS, PRIMEX, …..)

53

54

Plan View of the Spectrometer

BaBarSolenoid?

55

N

ee ~ 25 TeV

JLab MøllerLHC

New Contact Interactions

Møller Parity-Violating Experiment: New Physics Reach

(example of large installation experiment with 11 GeV beam energy)

AFB(b) measures product of e- and b-Z couplingsALR(had) measures purely the e-Z couplings

Proposed APV(b) measures purely thee-Z couplings at a different energy scale

Not “just another measurement” of sin2(w)

56

TMDs are complementary to GPDs in that they allow to construct 3-D images of the nucleon in momentum space

TMDs are connected to orbital angular momentum (OAM) in the nucleon wave function – for a TMD to be non-zero OAM must be present.

TMDs can be studied in experiments measuring azimuthal

asymmetries or moments.

Several proposals have been accepted by PAC34 that propose to upgrade CLAS12 with improved Kaon identification.

CLAS12CLAS12Transverse Momentum Distributions

57

Exclusive 0 production on transverse target

2D (Im(AB*))/ T

|A|2(1-2) - |B|2(2+t/4m2) - Re(AB*)22

AUT = -

Asymmetry depends linearlyon the GPD E, which enters “Ji’s sum rule” best known way to access quark angular momentum.

A ~ 2Hu + Hd

B ~ 2Eu + Ed0

K. Goeke, M.V. Polyakov,M. Vanderhaeghen, 2001

A ~ Hu - Hd

B ~ Eu - Ed+

AUT

xB

0

Great opportunity for 12 GeV-Upgrade science program

CLAS12

58

Transverse Momentum Dependence of Semi-Inclusive Pion Production

• Not much is known about the orbital motion of partons• Significant net orbital angular momentum of valence quarks implies significant transverse momentum of quarks

Pt = pt + z kt + O(kt

2/Q2)

Final transverse momentum of the detected pion Pt arises from convolution of the struck quark transverse momentum kt with the transverse momentum generated during the fragmentation pt.

z = E/

pT ~ < 0.5 GeV optimal for studies as theoretical framework for Semi-Inclusive Deep Inelastic Scattering has been well developed at small transverse momentum

Emerging new area of study

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The road to orbital motionThe difference between the +, –, and K+ asymmetries reveals that quarks and anti-quarks of different flavor are orbiting in different ways within the proton.

Swing to the left, swing to the right: A surprise of transverse-spin experiments

Illustration of the possible correlation between the internal motion of an up quark and the direction in which a positively-charged pion (ud) flies off.-

PT-dependences of the double and single-spin asymmetries provide important input for studies of flavor and helicity dependence of quark transverse momentum dependent distributions.

e.g., lattice: Higher probability to find a d-quark at large kT

Also higher probability to find a quark anti-aligned with proton spin at large kT (not shown)

Experimental Evidence for Exotic Hybrids 1−+

“Classification” Categories Used for the Assignment of Scientific Priority to the 12

GeV Experiments

The Hadron spectra as probes of QCD(GluEx and heavy baryon and meson spectroscopy)

The transverse structure of the hadrons (Elastic and transition Form Factors)

The longitudinal structure of the hadrons (Unpolarized and polarized parton distribution functions)

The 3D structure of the hadrons(Generalized Parton Distributions and Transverse Momentum Distributions)

Hadrons and cold nuclear matter(Medium modification of the nucleons, quark hadronization, N-N correlations, hypernuclear spectroscopy, few-body experiments)

Low-energy tests of the Standard Model and Fundamental Symmetries(Møller, PVDIS, PRIMEX, …..)

61