1. PacSpin 2007, Vancouver, Canada
The JLab 12 GeV Upgrade
Antje Bruell, JLab
PacSpin 2007, Vancouver, Canada
Upgrade of accelerator and experimental equipment
Highlights of the physics 12 GeV
Highlights of spin dependent 12 GeV
Timelines and schedule

2. Jefferson Lab Today
2000 member international user community engaged in exploring quark-gluon structure of matter
Superconducting accelerator provides 100% duty factor beams of unprecedented quality, with energies up to 6 GeV B C A
CEBAF’s innovative design
allows delivery of beam with unique properties to three experimental halls simultaneously
Each of the three halls offers complementary experimental capabilities and allows for large equipment installations to extend scientific reach

3. Jefferson Lab Today A B C
Hall A
Hall B
Two high-resolution
4 GeV spectrometers
Large acceptance spectrometer electron/photon beams
Hall C
Be brief A B C
7 GeV spectrometer,
1.8 GeV spectrometer,
large installation experiments

4. 12 11 6 GeV CEBAF Upgrade magnets and power supplies
CHL-2
Upgrade magnets and power supplies
help me
Enhanced capabilities
in existing Halls
Lower pass beam energies
still available

5. Experimental equipment for 12 GeV
Hall D – exploring origin of confinement by studying exotic mesons
Hall B – understanding nucleon structure via generalized parton distributions
Hall C – precision determination of valence quark properties in nucleons and nuclei
Note BSM not included in project
Hall A – short range correlations, form factors, hyper-nuclear physics, future new experiments 5

6. Technical Performance Requirements
Hall D
Hall B
Hall C
Hall A
excellent hermeticity
luminosity
10 x 1034
energy reach
installation space
polarized photons
hermeticity
precision
Eg~8.5-9 GeV
11 GeV beamline
108 photons/s
target flexibility
good momentum/angle resolution
excellent momentum resolution
high multiplicity reconstruction
luminosity up to 1038
particle ID
Don’t dwell on this too long, they can read it quickly

7. Physics Experimental Equipment
total project cost: $ 310 M

8. High Energy Scattering
QCD and confinement
Asymptotic Freedom
Confinement
Small Distance
High Energy
Large Distance
Low Energy
Perturbative QCD
Strong QCD
High Energy Scattering
Spectroscopy
Gluon
Jets
Observed
Gluonic
Degrees of Freedom
Missing 8

9. Gluonic Excitations Gluonic Excitations predicted by QCD
crucial for understanding confinement
quantum numbers of the excited gluonic fields couple to those of the quarks to produce mesons with exotic quantum numbers
mass spectra calculated by lattice QCD
possibility for experimental search
From G. Bali

10. Hybrid mesons and mass predictions
Normal mesons
1 GeV mass difference
Hybrid mesons and mass predictions
Jpc = 1-+ q
Lattice
GeV
GeV
GeV
Lowest mass expected to be p1(1−+) at 1.9±0.2 GeV

11. Coherent Bremsstrahlung
GlueX / Hall D Detector
12 GeV electrons
collimated
Lead Glass
Detector
Solenoid
Coherent Bremsstrahlung
Photon Beam
Tracking
Target
Cerenkov
Counter
Time of
Flight
Barrel
Calorimeter
Note that tagger is
80 m upstream of
detector
Electron Beam from CEBAF

12. Finding an Exotic Wave
An exotic wave (JPC = 1-+) was generated at level of 2.5 % with 7 other waves. Events were smeared, accepted, passed to PWA fitter.
Output: /- 3 MeV
Output: /- 11 MeV
Double-blind M. C. exercise
Statistics shown here correspond to a few days of running.
Mass
Input: MeV
Width
Input: 170 MeV

13. Neutron/Proton Charge Form Factor @12 GeV
(Polarization Experiments only)
Here shown as ratio of Pauli & Dirac Form Factors F2 and F1,
ln2(Q2/L2)Q2F2/F1  constant when taking orbital angular momentum into account (Ji)

14. Charged Pion Electromagnetic Form Factor
Where does the dynamics of the q-q interaction make a transition from
the strong (confinement) to the perturbative (QED-like) QCD regime?
It will occur earliest in the simplest systems
 the pion form factor Fp(Q2) provides our best chance to
determine the relevant distance scale experimentally
applicability of pQCD (GPD’s) to exclusive pion production ?

15. with enough luminosity to reach the high-Q2, high-x region!
Access to the DIS 12 GeV
with enough luminosity to reach the high-Q2, high-x region!
Counts/hour/
(100 MeV)2 (100 MeV2) for L=1035 cm-2 sec-1

16. Extending DIS to High x The Neutron Asymmetry A1
(similar precision for p and d)
The Neutron to Proton Structure Function Ratio
Hall C: 3H/3He
CLAS: tagging
spectator proton
Add overlay of 6 GeV data obtained to date (need to “stretch” to get on graph properly)
3He(e,e’)
12 GeV will access the valence quark regime (x > 0.3)

17. Flavor decomposition using SIDIS
Valence quarks
Ee =11 GeV NH3+He3

18. Flavor decomposition: polarized sea
Large flavor asymmetry in
unpolarized sea
Asymmetry in polarized sea?
First data from HERMES compatible with zero but have large uncertainties
Calculations:
Instantons (QSM)
Pion cloud models ?
(Goeke)
More data expected from RHIC SSA in future

19. Beyond form factors and quark distributions –
Generalized Parton Distributions (GPDs)
X. Ji, D. Mueller, A. Radyushkin ( )
Proton form factors, transverse charge & current densities
Structure functions,
quark longitudinal
momentum & helicity
distributions
Correlated quark momentum
and helicity distributions in
transverse space - GPDs

20. Kinematics for deeply excl. experiments
no overlap with other
existing experiments
compete with other
experiments

21. DVCS Single-Spin Asymmetry
Q2 = 5.4 GeV2
x = 0.35
-t = 0.3 GeV2
CLAS experiment
E0 = 11 GeV
Pe = 80%
L = 1035 cm-2s-1
Run time: 2000 hrs
Many x, Q2 and t values measured simultanously !

22. Projected precision in extraction of GPD H at x = x
Projected results
Spatial Image

23. orbital angular momentum carried by quarks : solving the spin puzzle* q q'  p p' e
At one value of x only
Ingredients:
1) GPD Modeling
2) HERMES 1H(e,e’g)p (transverse target spin asymmetry)
3) Hall A 2H(e,e’gn)p
Compared to Lattice QCD
For quarks 12 GeV will give final answers

24. Exclusive r0 production on transverse target
2D (Im(AB*))/p T
AUT = -
A ~ 2Hu + Hd r0
|A|2(1-x2) - |B|2(x2+t/4m2) - Re(AB*)2x2
B ~ 2Eu + Ed
AUT
A ~ Hu - Hd
B ~ Eu - Ed r+
Asymmetry depends linearly
on the GPD E, which enters
Ji’s sum rule. r0
K. Goeke, M.V. Polyakov,
M. Vanderhaeghen, 2001 xB

26. Longitudinally polarized Target SSA for p+
Measurement of kT dependent twist-2 distribution provides an independent test of the Collins fragmentation.
Real part of interfe-rence of wave functions with L=0 and L=1
In noncollinear single-hadron fragmentation additional FF H1(z,kT)
Efremov et al. p
Study the PT – dependence of AULsin2f
Study the possible effect of large unfavored Collins function. kT
quark

27. Transverse Target SSA @11 GeV
11GeV (NH3)
AUT ~
Collins p+ p0 p-
f1T┴, requires final state interactions + interference between different helicity states
Simultaneous (with pion SIDIS) measurement of, exclusive r,r+,w with a transversely polarized target important to control the background.
AUT ~
Sivers

28. Transversity in double pion production
The angular distribution of two hadrons is sensitive to the spin of the quark h1 h2
quark RT
“Collinear” dihadron fragmentation described by two functions at leading twist: D1(z,cosqR,Mpp),H1R(z,cosqR,Mpp)
Collins et al, Ji, Jaffe et al,
Radici et al.
relative transverse momentum of the two hadrons replaces the PT in single-pion production (No transverse momentum of the pair center of mass involved )
Dihadron production provides an alternative, “background free” access to transversity

29. Quark Structure of Nuclei: Origin of the EMC Effect
Observation that structure functions are altered in nuclei stunned much of the HEP community 23 years ago
~1000 papers on the topic; BUT more data are needed to uniquely identify the origin: What alters the quark momentum in the nucleus? x
JLab 12
Jlab at 12 GeV
Precision study of A-dependence
Measurements at x>1
“Polarized EMC effect”
Flavor-tagged (polarized) structure functions
valence vs. sea contributions
Explain what the EMC effect is.
Point out the three regions and their conventional explanations.
Cannot be fully explained by conventional nuclear physics
Amazing that we still don’t know the answer after nearly a quarter of a century
Coverage extends at least to x=1.5

30. Multi-quark clusters are accessible at large x (>>1) and high Q2
12 GeV gives access to the high-x, high-Q2 kinematics needed to find multi-quark clusters
Fe(e,e’)
5 PAC days
Need to demonstrate we are in the scaling region here.
Errors are the size of the points.
Point out the five days.
TRANSITION:
Now will shift from unpolarized, inclusive experiments to semi-inclusive, where measure final state hadron in addition to electron.
These are new experimental approaches for nuclei, made possible by the 12 GeV upgrade: semi-inclusive measurements and polarization. First want to remind about
Semi-inclusive
Mean field
Six-quark bag
(4.5% of wave function)
Correlated nucleon pair

31. g1(A) – “Polarized EMC Effect”
New calculations indicate larger effect for polarized structure function than for unpolarized: scalar field modifies lower components of Dirac wave function
Spin-dependent parton distribution functions for nuclei nearly unknown
Can take advantage of modern technology for polarized solid targets to perform systematic studies – Dynamic Nuclear Polarization
(polarized EMC effect)
Curve follows calculation by W. Bentz, I. Cloet,
A. W. Thomas.
Explain the curve
Mention the effect is >25% in nuclear matter, here scaled to density of valence nucleon in 7Li 31

32. “Polarized EMC Effect” – Flavor Tagging
semi-inclusive DIS on polarized targets, measuring p+ and p-, decompose to extract DuA(x), DdA(x).
Challenging measurement, but have new tools:
High polarization for a wide variety of targets
Large acceptance to constrain syst. errors and tune models x
Duv(x)
free nucleon
+ scalar field
+ Fermi
+ vector field
(total)
Ddv(x)
DdA(x)
Dd(x)
Somewhere put nuclear lattice QCD and ChPT?
Can eliminate black dotted curve, redraw?
TRANSITION:
Have discussed five questions whose experimental answers will help us to finally understand the origin of the EMC effect.
Up until now, have assumed nuclear fragmentation functions known. Now talk about how to get them.
Get delta-U-A from inclusive, delta-U-D from semi-inclusive
Ratios
DuA(x)
Du(x)
nuclear matter
nuclear matter
W. Bentz, I. Cloet, A. W. Thomas

33. APV ~ 8 x 10-5 Q2 APV Measurements 0.1 to 100 ppm
Steady progress in technology
part per billion systematic control
1% normalization control
JLab now takes the lead
New results from HAPPEX
Photocathodes
Polarimetry
Targets
Diagnostics
Counting Electronics E

35. DOE Generic Project Timeline
We are here
DOE CD-2 Reviews
Almost half-way between CD1 and CD2
September 2007

36. 12 GeV Upgrade: Phases and Schedule
(based on funding guidance provided by DOE-NP in April 2007)
Conceptual Design (CDR) - finished
Research and Development (R&D) - ongoing
2006 Advanced Conceptual Design (ACD) - finished
Project Engineering & Design (PED) - ongoing
Construction – starts in ~18 months!
Accelerator shutdown start mid 2012
Accelerator commissioning mid 2013
Pre-Ops (beam commissioning)
Hall commissioning start late 2013
Now in intensive design phase.
Construction begins in two years.

37. Summary
The Jlab 12 GeV Upgrade will increase the energy of CEBAF, provide very high luminosities and will thus allow to measure with unprecedented precision:
the high x behaviour of (un)polarised structure functions
the spin and flavour decomposition in the valence region
pion and nucleon form factors at high Q2
single spin asymmetries and kt dependent effects
deep exclusive processes in multi-differential form
nuclear effects in (semi)-inclusive scattering
search for hybrid states
parity violating asymmetries as a test of the standard model
The ideal laboratory for valence quark physics !

39. Quantum Numbers of Hybrid Mesons
Excited Flux Tube
Quarks
Hybrid Meson
like
Exotic
Flux tube excitation (and parallel quark spins) lead to exotic JPC
like

40. exotic nonets Lattice 1-+ 1.9 GeV 2+- 2.1 GeV 0+- 2.3 GeV 2 + – 2 + +
Radial
excitations
1.0
1.5
2.0
2.5
qq Mesons
L = 0 1 2 3 4
Meson Map
Each box corresponds
to 4 nonets (2 for L=0)
Mass (GeV)
exotic
nonets
0 – +
0 + –
1 + +
1 + –
1– +
1 – –
2 – +
2 + –
2 + +
0 + +
Glueballs
Hybrids
Lattice
GeV
GeV
GeV
(L = qq angular momentum)

41. Unraveling the Quark WNC Couplings
12 GeV:
(2C2u-C2d)=0.01
PDG: ± 0.24
Theory:
Vector quark couplings
Axial-vector quark couplings