1. Symmetries in Nuclear Physics
Krishna Kumar
University of Massachusetts
Editorial Board:
Parity Violation: K. K, D. Mack, M. Ramsey-Musolf, P. Reimer, P. Souder
Low Energy QCD: B. Bernstein, A. Gasparian, J. Goity
Jlab 12 GeV PAC Meeting, January 10, 2005
10 January, 2005
Symmetries in Nuclear Physics

2. Symmetries in Nuclear Physics
Symmetry Tests at 12 GeV
Strong Interaction
Chiral symmetry breaking
Axial Anomaly
Charge symmetry violation
Spin-Flavor symmetry breaking
Electroweak Interaction
TeV scale physics
10 January, 2005
Symmetries in Nuclear Physics

3. Symmetries in Nuclear Physics
Outline
Primakoff Production of Pseudoscalar Mesons
2 decay widths of  and ’
Transition Form Factors at low Q2
Parity-Violating Møller Scattering
Ultimate Precision at Q2<<MZ2: 25 TeV reach
Parity-Violating Deep Inelastic Scattering
New Physics at 10 TeV in Semileptonic Sector
Charge Symmetry Violation
d/u at High x
Higher Twist Effects
10 January, 2005
Symmetries in Nuclear Physics

4. Lightest Pseudoscalar Mesons
Spontaneous breaking of Chiral SUL(3)xSUR(3)
Goldstone bosons
Chiral anomalies
- Mass of 0
- 2 decay widths
Flavor SU(3) breaking
π0, , ’ mixing
Test fundamental QCD symmetries via the
Primakoff Effect
10 January, 2005
Symmetries in Nuclear Physics

5. Setup with Energy Upgrade
Larger X-Section
Lighter Nuclei: 1H and 4He
Better background separation
New high energy photon tagger
Improved PbWO4 calorimeter
10 January, 2005
Symmetries in Nuclear Physics

6. From 2 to 3π to Quark Mass Ratio
Leutwyler
10 January, 2005
Symmetries in Nuclear Physics

7. Symmetries in Nuclear Physics
Major Physics Impact
Determination of quark mass ratio
The nature of the ’: Goldstone boson?
Interaction Radii of π0, , ’
Chiral anomaly predictions
Number of colors Nc
Tests of QCD models
Tests of future lattice calculations
Input to light-by-light amplitude for (g-2)
10 January, 2005
Symmetries in Nuclear Physics

8. Symmetries in Nuclear Physics
PV Asymmetries to
(gAegVT + gVegAT)
For electrons scattering off nuclei or nucleons:
Z couplings provide access to different linear combination of underlying quark substructure
10 January, 2005
Symmetries in Nuclear Physics

9. Parity Violation at Jlab
Electron Beam Quality
Simple laser transport system; pioneers in PV experiments with high polarization cathodes (HAPPEX-I)
CW beam alleviates many higher order effects; especially in energy fluctuations
HAPPEX-II preliminary result: Araw correction ~ 60 ppb
High Luminosity
High beam current AND high polarization
Dense cryogenic targets with small density fluctuations
Progression of Precision Experiments
Facilitates steady improvements in technology
Strong collaboration between accelerator and physics divisions
(APV)/APV 1%
(APV) 1 part per billion
10 January, 2005
Symmetries in Nuclear Physics

10. The Annoying Standard Model
(it just wont break!)
The Annoying Standard Model
Nuclear Physics Long Range Plan:
What is the new standard model?
Low Q2 offers unique and complementary probes of new physics
Rare or Forbidden Processes
Symmetry Violations
Electroweak One-Loop Effects
- Double beta decay..
- neutrinos, EDMs..
- Muon g-2, beta decay..
Precise predictions at level of 0.1%
Indirect access to TeV scale physics
Low energy experiments are again relevant in the neutral current sector
10 January, 2005
Symmetries in Nuclear Physics

11. World Electroweak Data
16 precision electroweak measurements:
2/dof ~ 25.4/15
Probability < 5%
Leptonic and hadronic
Z couplings seem inconsistent
Perhaps the Standard Model is already broken
Perhaps there are bigger effects elsewhere
10 January, 2005
Symmetries in Nuclear Physics

12. Electroweak Physics at Low Q2
Q2 << scale of EW symmetry breaking
Logical to push to higher energies, away from the Z resonance
LEPII, Tevatron, LHC access scales greater than L ~ 10 TeV
Q2<<MZ2
Complementary:
Parity Violating vs Parity Conserving
10 January, 2005
Symmetries in Nuclear Physics

13. Fixed Target Møller Scattering
Purely leptonic reaction
QWe ~ 1 - 4sin2W
Figure of Merit rises linearly with Elab
Maximal at 90o in COM (E’=Elab/2)
Highest possible Elab with good P2I
Moderate Elab with LARGE P2I
SLAC E158
Jlab at 12 GeV
Unprecedented opportunity: The best precision at Q2<<MZ2 with the least theoretical uncertainty until the advent of a linear collider or a neutrino factory
10 January, 2005
Symmetries in Nuclear Physics

14. Symmetries in Nuclear Physics
Design for 12 GeV
E’: 3-6 GeV
APV = 40 ppb
lab = 0.53o-0.92o
150 cm LH2 target
4000 hours
Ibeam = 100 µA
Toroidal spectrometer ring focus
(APV)=0.58 ppb
Beam systematics: steady progress
(E158 Run III: 3 ppb)
Focus alleviates backgrounds:
ep  ep(), ep  eX()
Radiation-hard integrating detector
Normalization requirements similar
to other planned experiments
Cryogenics, density fluctuations
and electronics will push the state-
of-the-art
10 January, 2005
Symmetries in Nuclear Physics

15. Symmetries in Nuclear Physics
New Physics Reach
Jlab Møller
LHC
ee ~ 25 TeV
New Contact Interactions
Complementary; 1-2 TeV reach
LEP200
ee ~ 15 TeV
SUSY provides a dark matter candidate if baryon (B) and lepton (L) numbers are conserved
Kurylov, Ramsey-Musolf, Su
However, B and L need not be conserved in SUSY, leading to neutralino decay (RPV)
QeW and QpW would have
new contributions from RPV
10 January, 2005
Symmetries in Nuclear Physics

16. Symmetries in Nuclear Physics
Electroweak Physics
QWe
modified
Marciano and Czarnecki
sin2W runs with Q2
Semileptonic processes have
significant uncertainties
E158 established running,
probing vector boson loops
Jlab measurement would
probe scalar loops
(sin2W) ~
10 January, 2005
Symmetries in Nuclear Physics

17. Parity Violating Electron DISZ* * X N
fi(x) are quark distribution functions
For an isoscalar target like 2H, structure functions largely cancel in the ratio
+ small corrections
b(x) is a factor of 5 to 10 smaller
Elastic scattering measures C1i, but C2i are less well-known
12 GeV:
Moderate x, high Q2, W2
1% measurements feasible
TeV scale physics
10 January, 2005
Symmetries in Nuclear Physics

18. Symmetries in Nuclear Physics
2H PV DIS at 11 GeV
E’: 6.8 GeV ± 10%
APV = 290 ppm
lab = 12.5o
400 hours
Ibeam = 90 µA
60 cm LD2 target
xBj ~ 0.45
Q2 ~ 3.5 GeV2
W2 ~ 5.23 GeV2
1 MHz DIS rate, π/e ~ 1
HMS+SHMS or MAD
(APV)=1.5 ppm
Systematic limit: Beam polarization
Beam systematics easily controlled
moderate running time
Best constraint on 2C2u-C2d
Similar sensitivity to NuTeV
Theoretical interpretability issues:
Important in themselves!
PV DIS can address these issues
10 January, 2005
Symmetries in Nuclear Physics

19. Charge Symmetry Violation (CSV)
Charge symmetry: assume
are negligible
u-d mass difference
electromagnetic effects
Small effects are possible from:
Search for unambiguous signal of CSV at the partonic level
No theoretical issues at high Q2, W2
For PV DIS off 2H:
10% effect possible if u+d falls off more rapidly than u-d at x ~ 0.7
From pdf fits: 1/3 of NuTeV discrepancy from CSV
But at 90% C.L., effect could be 3 to 4 times bigger….
Londergan & Thomas
Strategy for PV DIS:
measure or constrain higher twist effects at x ~
precision measurement of APV at x ~ 0.7 to search for CSV
10 January, 2005
Symmetries in Nuclear Physics

20. Symmetries in Nuclear Physics
Higher Twist Effects
Brodsky 
APV sensitive to diquarks: ratio of weak to electromagnetic charge depends on amount of coherence
If Spin 0 diquarks dominate, likely only 1/Q4 effects.
Novel interference terms might contribute
Other higher twist effects may cancel, so APV may have little dependence on Q2.
10 January, 2005
Symmetries in Nuclear Physics

21. Symmetries in Nuclear Physics
d/u at High x
SU(6) breaking (scalar diquark dominance), expect d/u ~ 0
Perturbative QCD prediction for x ~ 1: d/u ~ 0.2
No consensus on existing deuteron structure function data
Proposed methods have nuclear corrections
APV in DIS on 1H
+ small corrections
d/u measurement on a single proton!
No nuclear corrections!
Must control higher twist effects
Verify Standard Model at low x
Must obtain ~ 1% stat. errors at x ~ 0.7
10 January, 2005
Symmetries in Nuclear Physics

22. Symmetries in Nuclear Physics
PV DIS Program
Hydrogen and Deuterium targets
1 to 2% errors
It is unlikely that any effects are larger than 10%
x-range
W2 well over 4 GeV2
Q2 range a factor of 2 for each x point
(Except x~0.7)
Moderate running times
TeV physics, higher twist probe, CSV probe, precision d/u…
The Standard Model test can be done with proposed Hall upgrade equipment
A dedicated spectrometer/detector package is needed for rest of program
10 January, 2005
Symmetries in Nuclear Physics

23. A Concept for PV DIS Studies
Magnetic spectrometer
would be too expensive
Calorimeter to identify
electron clusters and reject
hadrons a la A4 at Mainz
Toroidal sweeping field to
reduce neutrals, low energy
Mollers and pions
Cherenkov detectors for pion
rejection might be needed
CW 100 µA at 11 GeV
20 to 40 cm LH2 and LD2 targets
Luminosity > 1038/cm2/s
solid angle > 200 msr
Count at 100 kHz
pion rejection of 102 to 103
10 January, 2005
Symmetries in Nuclear Physics

24. Symmetries in Nuclear Physics
High x Physics Outlook
Parity-Violating DIS can probe exciting new physics at high x
One can start now (at 6 GeV)
Do 2 low Q2 points (P , X. Zheng contact)
Q2 ~ 1.1 and 1.9 GeV2
Either bound or set the scale of higher twist effects
Take data for W<2 (P , P. Bosted contact)
Duality
Could help extend range at 11 GeV to higher x
A short run to probe TeV physics in PV DIS off 2H: Hall A or C
The bulk of the program requires a dedicated spectrometer/detector
CSV can also be probed via electroproduction of pions
6 GeV beam can probe x ~ 0.45 (P , K. Hafidi contact)
Should be able to go to higher x with 12 GeV beam
Other physics topics could be addressed:
Transverse (beam-normal) asymmetries in DIS
Polarized targets: g2 and g3 structure functions
Higher twist studies of A1p and A1n
10 January, 2005
Symmetries in Nuclear Physics

25. Symmetries in Nuclear Physics
Summary
New window to symmetry tests opened by 12 GeV upgrade
Precision measurements of pseudoscalar meson properties: tests of low energy QCD and extraction of fundamental parameters
APV in Møller scattering has unique sensitivity to leptonic contact interactions to 25 TeV
APV in DIS off 2H at x ~ 0.45 would probe for TeV physics in axial-vector quark couplings
An exciting array of important topics in high x physics can be addressed by a new, dedicated spectrometer/detector concept
10 January, 2005
Symmetries in Nuclear Physics