Symmetries in Nuclear Physics

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 Symmetries in Nuclear Physics

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

3. 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 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 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 Symmetries in Nuclear Physics

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

7. 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) Symmetries in Nuclear Physics

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

10. (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 Symmetries in Nuclear Physics

11. WorldElectroweakData 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 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 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 Symmetries in Nuclear Physics

14. Design for 12 GeV APV = 40 ppb E’: 3-6 GeV lab = 0.53o-0.92o 4000 hours 150 cm LH2 target Ibeam = 100 µA (APV)=0.58 ppb Toroidal spectrometer ring focus • 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 Symmetries in Nuclear Physics

15. 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 Symmetries in Nuclear Physics

16. 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) ~ 0.0003 Symmetries in Nuclear Physics

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

18. 2H PV DIS at 11 GeV APV = 290 ppm E’: 6.8 GeV ± 10% lab = 12.5o 400 hours 60 cm LD2 target Ibeam = 90 µA 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 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 ~ 0.5-0.6 • precision measurement of APV at x ~ 0.7 to search for CSV Symmetries in Nuclear Physics

20. Higher Twist Effects • 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. Brodsky  Symmetries in Nuclear Physics

21. 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 Symmetries in Nuclear Physics

22. PV DIS Program • Hydrogen and Deuterium targets • 1 to 2% errors • It is unlikely that any effects are larger than 10% • x-range 0.3-0.7 • 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 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 Symmetries in Nuclear Physics

24. 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-05-007, 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-05-005, 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-05-006, 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 Symmetries in Nuclear Physics

25. 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 Symmetries in Nuclear Physics