Symmetries in Nuclear Physics

  • View

  • Download

Embed Size (px)


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. Symmetry Tests at 12 GeV. - PowerPoint PPT Presentation

Text of Symmetries in Nuclear Physics

  • Symmetries in Nuclear PhysicsKrishna KumarUniversity of Massachusetts

    Editorial Board:Parity Violation: K. K, D. Mack, M. Ramsey-Musolf, P. Reimer, P. SouderLow Energy QCD: B. Bernstein, A. Gasparian, J. Goity

    Jlab 12 GeV PAC Meeting, January 10, 2005

  • Symmetry Tests at 12 GeVStrong InteractionChiral symmetry breakingAxial AnomalyCharge symmetry violationSpin-Flavor symmetry breakingElectroweak InteractionTeV scale physics

  • OutlinePrimakoff Production of Pseudoscalar Mesons2 decay widths of and Transition Form Factors at low Q2Parity-Violating Mller ScatteringUltimate Precision at Q2
  • 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 0, , mixingTest fundamental QCD symmetries via the Primakoff Effect

  • Setup with Energy Upgrade Larger X-Section Lighter Nuclei: 1H and 4He Better background separationNew high energy photon taggerImproved PbWO4 calorimeter

  • From 2 to 3 to Quark Mass RatioLeutwyler

  • Major Physics Impact Determination of quark mass ratioThe nature of the : Goldstone boson?Interaction Radii of 0, , Chiral anomaly predictionsNumber of colors NcTests of QCD modelsTests of future lattice calculationsInput to light-by-light amplitude for (g-2)

  • PV AsymmetriestoFor electrons scattering off nuclei or nucleons:Z couplings provide access to different linear combination of underlying quark substructure(gAegVT + gVegAT)

  • Parity Violation at JlabElectron Beam QualitySimple laser transport system; pioneers in PV experiments with high polarization cathodes (HAPPEX-I)CW beam alleviates many higher order effects; especially in energy fluctuationsHAPPEX-II preliminary result: Araw correction ~ 60 ppbHigh LuminosityHigh beam current AND high polarizationDense cryogenic targets with small density fluctuationsProgression of Precision ExperimentsFacilitates steady improvements in technologyStrong collaboration between accelerator and physics divisions(APV) 1 part per billion(APV)/APV 1%

  • The Annoying Standard ModelRare or Forbidden ProcessesSymmetry ViolationsElectroweak One-Loop Effects- Double beta decay..- neutrinos, EDMs..- Muon g-2, beta decay..Nuclear Physics Long Range Plan:What is the new standard model?Precise predictions at level of 0.1%Indirect access to TeV scale physicsLow energy experiments are again relevant in the neutral current sectorLow Q2 offers unique and complementary probes of new physics(it just wont break!)

  • World Electroweak Data2/dof ~ 25.4/15Probability < 5% Leptonic and hadronicZ couplings seem inconsistentPerhaps the Standard Model is already brokenPerhaps there are bigger effects elsewhere16 precision electroweak measurements:

  • Electroweak Physics at Low Q2LEPII, Tevatron, LHC access scales greater than L ~ 10 TeVLogical to push to higher energies, away from the Z resonanceParity Violating vs Parity ConservingQ2
  • Fixed Target Mller ScatteringPurely leptonic reaction QWe ~ 1 - 4sin2W Maximal at 90o in COM (E=Elab/2) Highest possible Elab with good P2I Moderate Elab with LARGE P2IFigure of Merit rises linearly with ElabSLAC E158Jlab at 12 GeVUnprecedented opportunity: The best precision at Q2
  • Design for 12 GeVE: 3-6 GeVlab = 0.53o-0.92oAPV = 40 ppbIbeam = 100 A4000 hours(APV)=0.58 ppb150 cm LH2 targetToroidal 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

  • New Physics Reachee ~ 25 TeVJlab Mlleree ~ 15 TeVLEP200LHCComplementary; 1-2 TeV reachNew Contact InteractionsSUSY provides a dark matter candidate if baryon (B) and lepton (L) numbers are conservedHowever, B and L need not be conserved in SUSY, leading to neutralino decay (RPV)QeW and QpW would havenew contributions from RPVKurylov, Ramsey-Musolf, Su

  • Electroweak PhysicsQWemodifiedsin2W runs with Q2 Semileptonic processes have significant uncertainties E158 established running, probing vector boson loops Jlab measurement would probe scalar loops(sin2W) ~ 0.0003Marciano and Czarnecki

  • Parity Violating Electron DISfi(x) are quark distribution functionse-NXe-Z**TeV scale physicsFor an isoscalar target like 2H, structure functions largely cancel in the ratio+ small correctionsb(x) is a factor of 5 to 10 smallerElastic scattering measures C1i, but C2i are less well-known1% measurements feasible12 GeV: Moderate x, high Q2, W2

  • 2H PV DIS at 11 GeVE: 6.8 GeV 10%lab = 12.5oAPV = 290 ppmIbeam = 90 A400 hours(APV)=1.5 ppm60 cm LD2 target1 MHz DIS rate, /e ~ 1 HMS+SHMS or MADxBj ~ 0.45Q2 ~ 3.5 GeV2W2 ~ 5.23 GeV2 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

  • Charge Symmetry Violation (CSV)Charge symmetry: assumeare negligibleSmall effects are possible from:u-d mass differenceelectromagnetic effectsSearch for unambiguous signal of CSV at the partonic level From pdf fits: 1/3 of NuTeV discrepancy from CSVBut at 90% C.L., effect could be 3 to 4 times bigger.For PV DIS off 2H: 10% effect possible if u+d falls off more rapidly than u-d at x ~ 0.7measure or constrain higher twist effects at x ~ 0.5-0.6precision measurement of APV at x ~ 0.7 to search for CSVStrategy for PV DIS:No theoretical issues at high Q2, W2 Londergan & Thomas

  • Higher Twist EffectsAPV sensitive to diquarks: ratio of weak to electromagnetic charge depends on amount of coherenceIf Spin 0 diquarks dominate, likely only 1/Q4 effects.Novel interference terms might contributeOther higher twist effects may cancel, so APV may have little dependence on Q2.


  • d/u at High xSU(6) breaking (scalar diquark dominance), expect d/u ~ 0Perturbative QCD prediction for x ~ 1: d/u ~ 0.2No consensus on existing deuteron structure function dataProposed methods have nuclear correctionsMust control higher twist effectsVerify Standard Model at low xMust obtain ~ 1% stat. errors at x ~ 0.7d/u measurement on a single proton!No nuclear corrections!

    + small correctionsAPV in DIS on 1H

  • PV DIS ProgramHydrogen and Deuterium targets1 to 2% errorsIt is unlikely that any effects are larger than 10%x-range 0.3-0.7W2 well over 4 GeV2Q2 range a factor of 2 for each x point(Except x~0.7)Moderate running times The Standard Model test can be done with proposed Hall upgrade equipment A dedicated spectrometer/detector package is needed for rest of programTeV physics, higher twist probe, CSV probe, precision d/u

  • A Concept for PV DIS StudiesCW 100 A at 11 GeV20 to 40 cm LH2 and LD2 targetsLuminosity > 1038/cm2/s solid angle > 200 msrCount at 100 kHz pion rejection of 102 to 103 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

  • High x Physics OutlookParity-Violating DIS can probe exciting new physics at high xOne can start now (at 6 GeV)Do 2 low Q2 points (P-05-007, X. Zheng contact)Q2 ~ 1.1 and 1.9 GeV2Either bound or set the scale of higher twist effectsTake data for W
  • SummaryNew window to symmetry tests opened by 12 GeV upgradePrecision measurements of pseudoscalar meson properties: tests of low energy QCD and extraction of fundamental parametersAPV in Mller scattering has unique sensitivity to leptonic contact interactions to 25 TeVAPV in DIS off 2H at x ~ 0.45 would probe for TeV physics in axial-vector quark couplingsAn exciting array of important topics in high x physics can be addressed by a new, dedicated spectrometer/detector concept