Spin Based Physics at Jefferson Lab
Hugh Montgomery
October 10, 2008

• State-of-the-art technologies
• Spin physics at Jefferson Laboratory
– The first ten years
– The remaining “6 GeV” program
• Jlab 12 GeV Upgrade
• ELIC
• Summary
2

Polarimeter
Injector Mott
Hall A Compton
Hall A Moller
Hall B Moller
Hall C Moller
I ave
P x
P
2

A x x y
70

A
1

A x
10 nA
1

A
P x x x x x z
3
Under development
<0.5% Atomic Beam Polarimeter (Hall A)
<1% Compton Polarimeter (Hall C)
3

Hall A: 3 He
G
E n , SSAs
Transversity
Hall B: eg1
Dynamically polarized NH
3
ND
3,
Q 2 evolution of
Nucleon Spin
Structure, DVCS
Hall B: FROST
Frozen Spin
Target, Butanol
“Missing” N*
Search.
Hall C:
Dynamically polarized, NH
3
ND
3
G
E n , SANE, g
1 p , g
1 d
4
HDIce from BNL under development:
Polarized neutron target for N* expts.
4

• QCD and the Structure of Hadrons
– Discovery of unexpected behavior of G
E p
– Strangeness content of the proton
; Measurement of G
– The deformation of
 and N* transition form factors
E n
– Spin dependent structure functions:
Bjorken & GDH sum rule; g
1n
; |∆ G|
– Measurement of the pion form factor
– Exploration of duality, pQCD counting rules, color transparency
– Initial exploration of Generalized Parton Distributions (GPDs) towards mapping of angular momentum in the proton
• Nuclei: From Structure to Exploding Stars
– New information on correlations in nuclei and the role of the tensor force
– Studies of hypernuclei – better than 400keV resolution
• In Search of the New Standard Model
– factor 5 increase in precision of Standard Model couplings
5

Jefferson Lab – Spin Structure Functions g
1
(x,Q 2 )
World data on the proton including Jlab covering the resonance region and overlapping with the DIS domain
Similar coverage for the
Deuteron
Enormous contribution towards understanding the spin of and in the nucleon.
Halved the uncertainties in the parton distribution functions.
6
6

2
E n
• G
E n
• G
E n at 1.7 GeV at 3.4 GeV
2
2 is well above G is closer to G
Galster
Galster
.
and far below CQM and GPD
• Final accuracy for 3.4 GeV
2 expected to improved by factor 1.5
• Next release will be the result at 2.5 GeV 2
7

Science Remaining for CEBAF@6 GeV ?
• Completion of data-taking for milestone-related physics
–
Baryon spectroscopy (FROzen Spin Target and HDIce target data)
– DVCS (CLAS Phase II and Hall A separation of BH

DVCS and DVCS 2 )
– Structure function moments (SANE, d
2 n )
– …..
• Important new data on:
– Strange quark distributions (HAPPEx III)
–
Hypernuclear spectroscopy
–
Correlations ( 4 He( e,e’pN) data extended)
– Dispersive effects in electron scattering [(e + ,e + ) vs (e ,e )]
– Transversity
– …..
• Unique new experimental directions:
– PREx (rms radius of neutron dist. for nuclear structure, astrophysics, and atomic PV Standard Model tests)
–
Q
Weak
(Weak charge of the proton for a Standard Model Test)
• Measurements in new areas of research that will be a focus of science with the 12 GeV Upgrade, such as:
–
Single spin asymmetries
–
DVCS w/ Longitudinally polarized target
– PVDIS, …..
8

Deep Virtual Compton Scattering : Gen. Parton Dists ?
Three A-rated experiments combined allow the separation of Generalized
Parton Distributions.
Hall A Experiment will separate the Bethe-Heitler from the Deep Compton
Hall B E1-DVCS and EG1-DVCS are scheduled to run in 2008/2009 and use polarized electron beams and longitudinally polarized proton target.
HD-DVCS is conditionally approved (relying on the operation of the HD-Ice target with electron beams) will use a transversely polarized proton (and deuterium) target.
9

All Data & Fits
Plotted at 1 σ
Standard Model
Prediction
Isovector weak charge
10
HAPPEx: H, He
G 0 : H,
PVA4: H
SAMPLE: H, D
Q-weak expected precision

TJNAF E06-002: PREX
A Clean Measurement of the Neutron Skin in 208 Pb
Q 2 ~0.008 GeV 2 , E = 1 GeV
,  
5
0
Z 0 : Clean Probe Couples Mainly to Neutrons
δ(A
PV
) ~ ± 3%
δ(R n
) ~ ±1%
( Dany Page )
Subject of Aug
08 JLab workshop that attracted
70 experts from many different fields
Physics Implications
•Nuclear Equation of State
•Neutron stars
•Size and density
•Crust
•Cooling
•Heavy Ion Collisions
•Atomic Parity Violation
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• Technical Status
• R&D 98% complete
• Overall PED 76% complete (Civil design 100% complete)
• 18 major procurement packages issued
• bid packages under review for 5 major procurements
• 2009-2014 Construction
• Is starting FY2009
• Accelerator shutdown – May 2011 through Oct 2011 (6 months)
•
Accelerator shutdown start mid-May 2012 ; commissioning mid-May 2013
• 2013-2015 Hall Pre-Ops (beam commissioning)
• Hall A commissioning start ~October 2013
• Hall D commissioning start ~April 2014
• Halls B and C commissioning start ~October 2014
12

CHL-2
New Hall
Enhanced capabilities in existing Halls
13
Maintain capability to deliver lower pass beam energies

14

REQUIRES:
• High beam polarization
• High electron current
• High target polarization
• Large solid angle spectrometers
12 GeV will access the regime (x > 0.3), where valence quarks dominate
15

A V
C
1 i
V
 2 g
A e g
V i C
2 i
A
 2 g
V e g
A i
 

(2C
12 GeV:
2u
-C
2d
)=0.01
PDG: -0.08 ± 0.24
Theory: +0.0986
Vector quark couplings
16
Axial-vector quark couplings

Møller Parity-Violating Experiment: New Physics Reach


JLab
Møller
JLab ee
New Contact Interactions
~ 25 TeV
LEP200
 ~ 15 TeV
LHC
Complementary; 1-2 TeV reach
Kurylov, Ramsey-Musolf, Su
 candidate for dark matter?
•
LHC
~ 15 TeV numbers are conserved
• However, B and L need not be conserved in SUSY, leading to neutralino decay (RPV)
 sin 2

W
~ 0.00025
95% C.L.
JLab 12 GeV
Møller
17

18

• Recommended as a generic capability by:
– NSAC Long Range Report
– IUPAP WG9 Working Group on world-wide nuclear facilities
• Candidate Facilities with different key characteristics
– LHeC at CERN
– eRHIC at Brookhaven National Laboratory
– ELIC – ELectron Ion Collider at Jlab
– MANUEL at FAIR-GSI
• Natural Extension of Jlab nuclear physics agenda
• Issues
– Physics Case(s) not yet broadly accepted
– Cost scale is thought to be large
• Collaboration with BNL
• Directors to commission an advisory group to help advise prepare the case for the next NSAC Long Range Plan. Group exists, charge drafted, need date.
19

EL
I
C
20

 Ring-Ring (R-R) design taking CEBAF advantage as full energy polarized injector
• 12 GeV CEBAF Upgrade polarized source/injector already meets beam requirement of R-R design (0.1 mA)
 Spin Capabilities
• Longitudinal polarization at the IP for both beams
• Transverse polarization of ions
• Spin-flip of both beams
• All polarizations >70% desirable
 “ Figure-8 ” ion and lepton storage rings
• Ensure spin preservation and ease of spin manipulation
• No spin sensitivity to energy for all species.
 Luminosity of 3 ·10 34 cm -2 s -1 (per IP, 4 IP’s) at 0.5 GHz collision frequency, with a 10 σ aperture for proton and 13σ aperture for electrons
21

•
Parton distribution functions
• Longitudinal and transverse spin distribution functions
• Generalized parton distributions
•Transverse momentum distributions
22

Spin-Flavor Decomposition of the Light Quark Sea u u u
> d d u d d
Many models predict
 u > 0,
 d < 0
RHIC-Spin region
23

 The physics program thus far has been dominated by that part depending on SPIN
 The remaining 6 GeV Program is dominated by SPIN
 The 12 GeV Program, as far as we understand it now, is dominated by SPIN
 ELIC Capabilities emphasize SPIN
 At JLAB SPIN is very much an everyday tool and will likely remain so.
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