1 / 38

Strangeness in the Nucleon Newest Results from HAPPEx and G0

Strangeness in the Nucleon Newest Results from HAPPEx and G0. Physics case Electroweak Standard Model Experimental Aspects Results and Perspectives. Physics Case. Nucleon Structure: Valence quarks dressed by gluon exchange and qq fluctuations.

chavi
Download Presentation

Strangeness in the Nucleon Newest Results from HAPPEx and G0

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Strangeness in the NucleonNewest Results from HAPPEx and G0 • Physics case • Electroweak Standard Model • Experimental Aspects • Results and Perspectives D. Lhuillier - CEA Saclay

  2. Physics Case • Nucleon Structure: • Valence quarks dressed by gluon exchange and qq fluctuations. • Quark sea, key component on the nucleon. • Strangeness in the nucleon: s quark flavor decouples from valence quarks but may still be light enough to contribute. “Low Q” physics D. Lhuillier - CEA Saclay

  3. Strange Quarks in the Nucleon Strange sea measured in N scattering Strange sea is well-known, but contributions to nucleon matrix elements are somewhat unsettled: • Spinpolarized DIS • Inclusive: Ds = -0.08 ± 0.05 • Semi-inclusive: Ds = 0.03± 0.03 • Strange mass • pN scattering: 0-30% • Strange vector Form Factor D. Lhuillier - CEA Saclay

  4. Form Factors Elastic scattering off a static potential (no spin): (q) • Direct image of the charge distribution inside the target, in the limit of no recoil (Q2<M2). D. Lhuillier - CEA Saclay

  5. FT Electromagnetic Form Factors Nucleon target: 2S+1 form factors e- Charge (q) Magnetization p,n D. Lhuillier - CEA Saclay

  6. e- (q) Charge symmetry u-d Flavour Separation s quarks distributions? GEs(0) = 0, no other symmetry constraints… D. Lhuillier - CEA Saclay

  7. Z0 new probe of the nucleon, only assumes charge sym. • Sensitive to (s - s ). Weak Form Factors e- Vector Axial Z0 (q) • 3 flavors separation: D. Lhuillier - CEA Saclay

  8. 180 deg. • Electromagnetism • Gravitation • Strong interaction • Weak interaction Parité (Réflexion / O) O Sym. miroir g g g g g g Vector : Pseudo-vector: Scalar : Pseudo-scalar : r,p,E s=rLp,B m h=s.p -r,-p,-E +s,+B +m -h g g g g g g g g Parity Symmetry D. Lhuillier - CEA Saclay

  9. T.D.Lee/C.N.Yang Measure a Pseudoscalar… Propose to test PV in weak interactions C.S. Wu • decay of polarized 60Co M. Gell-Mann/R. Feynman (V-A) theory Lee & Yang M. Goldhaber Left handed neutrino 1957 ! D. Lhuillier - CEA Saclay

  10. (CERN, 1973) f Partial P in neutral weak current  electroweak unification. Z0 e± JZ0 = J3 – sin2qW Jem J+, J-, …. J3 SU(2)LxU(1)Y W± W+, W-, …. Z0  f cfV = T3 – 2sin2qWQf cfA = T3 (V-A) Electroweak Standard Model • Weak isospin group SU(2)L: D. Lhuillier - CEA Saclay

  11. -Z0 Interference 2 e- e- (Q) Z0 (Q) +  = |MgMZ|2 = Scale ~ 1 fm MZ ~ Q2 <<MZ2 << Mg~ Z0 contribution in the cross section is negligible… D. Lhuillier - CEA Saclay

  12. Parity Violating Asymmetry Lee & Yang:measure a pseudoscalar quantity APV, generated by helivcity flip of the e- beam NL NR D. Lhuillier - CEA Saclay

  13. E122@SLAC b e- e- PVDIS 2H X a Isoscalar target: aand b ~ cst (@ large x) C.Y. Prescott et al., 1978 APV~10-4 ±10-5 sin2qW = 0.224 ± 0.020 D. Lhuillier - CEA Saclay

  14. Backward angle Forward angle 4He target:GEs alone 2H target: enhanced GAe sensitivity Weak Form Factors Proton target: ~ few parts per million D. Lhuillier - CEA Saclay

  15. Experimental Strategies G0 : Large , Particle id, large Q2 range HAPPEx : small , integrating, single accurate Q2 D. Lhuillier - CEA Saclay

  16. Experimental Challenges Goal: down to ~50 ppb absolute error and 2% relative • High rate • High beam polarization • Control of beam asymmetries • Background rejection • Normalization D. Lhuillier - CEA Saclay

  17. « Table Top » Experiments DAQ • No “external” instrumentation: • Control of the polarized source • Redundant beam monitoring from injector to experimental hall D. Lhuillier - CEA Saclay

  18. The Polarized e- Source • Optical pumping of strained GaAs cathode produces highly-polarized e- beam. • “Strain” boosts polarization but introduces anisotropy in response. • Rapide and pseudo-random helicity flip. • Pair asymmetry measured several million times to reach stat. error. D. Lhuillier - CEA Saclay

  19. Beam Asymmetries Intensity: Beam Axis Position: Typical sensitivity: 10ppm/m • Azimuthally symmetric detector • Most h.c. beam asymmetries trace back to differences in preparation of circularly polarized laser light at the source. X=XR-XL D. Lhuillier - CEA Saclay

  20. PITA Effet Polarization Induced Transport Asymmetry Perfect ±l/4 retardation leads to perfect D.o.C.P. • Now L/R states have opposite sign linear components. • This couples to “asymmetric transport” in the optics system to produce an intensity asymmetry. Acommonretardation offset over-rotates one state, under-rotates the other Right helicity Left helicity This is theD phase D. Lhuillier - CEA Saclay

  21. Intensity Asymmetry using RHWP minimum analyzing power maximum analyzing power A rotatable l/2 plate downstream of the P.C. allows arbitrary orientation of DoLP Electron beam intensity asymmetry (ppm) 4q term measures Ana Power*DoLP (from Pockels cell) Rotating waveplate angle D. Lhuillier - CEA Saclay

  22. OpticsTable High Pe High Q.E. Low Apower Strategy • Rapid, pseudo-random helicity flip. • Careful config. to reduce beam asym. • Feedback systems to zero residual asym. measured in exp. hall. • Further cancellation by slow helicity reversals. controls effective analyzing power Tune residual linear pol. Slow helicity reversal Intensity Attenuator (charge Feedback) D. Lhuillier - CEA Saclay

  23. Feedback Reduce remaining effects Position (G0) charge Performances: Figures from K.Nakahara AI < 1 ppm x ~ 1 nm 10 ppb final correction Cates et al., NIM A vol. 278, p. 293 (1989) T.B. Humensky et. al., NIM A 521, 261 (2004) D. Lhuillier - CEA Saclay

  24. Asymmetry (ppm) Slug Slow Reversals Pure statistical distribution of the pair asymmetries Helicity Window Pair Asymmetry Sign flip of APV under insertion / removal of the half-wave plate at the source D. Lhuillier - CEA Saclay

  25. Polarimeters Compton 1% syst Continuous Møller 2% syst JLab Hall A E~3GeV, =6° Q2~0.1 GeV/c2 Target 400 W transverse flow 20 cm, LH2 20 cm, 200 psi 4He High Resolution Spectrometer S+QQDQ 5 mstr over 4o-8o D. Lhuillier - CEA Saclay

  26. PMT Elastic Rate: 1H: 120 MHz Cherenkov cones 4He: 12 MHz PMT Overlap the elastic line above the focal plane and integrate the flux Very clean separation of elastic events by HRS optics  Happex Detectors 100 x 600 mm ADC 12 m dispersion sweeps away inelastic events Large dispersion and heavy shielding reduce backgrounds at the focal plane D. Lhuillier - CEA Saclay

  27. JLab Hall C Detector wheel G0 beam monitoring girder Superconducting magnet D. Lhuillier - CEA Saclay

  28. Forward angle configuration G0 Detectors protons Q2=0.1-1.0 GeV/c2 Detectors Magnet elastic protons Inelastic protons Beam + Target ToF histogram D. Lhuillier - CEA Saclay

  29. CED+ Cherenkov FPD Backward angle configuration e- beam target G0 Detectors electrons e~110° Magnet Beam Target D. Lhuillier - CEA Saclay

  30. Polarimetry Main normalization error, Aexp = Pe.APV - Moller polarimetry in hall C: solid target saturated in high B field 1.3% relative accuracy Interleaved runs at low current - Compton polarimetry in hall A: continuous monitoring FOM strongly depends on Ebeam 1.0% relative accuracy @ 3GeV D. Lhuillier - CEA Saclay

  31. Results @ Q2=0.1 GeV/c2 HAPPEX only : APVh=-1.58± 0.12 ± 0.04 ppm APVHe=6.40 ± 0.23 ± 0.12 ppm GMs = 0.18 ± 0.27 GEs = -0.005 ± 0.019 Global fit: GMs = 0.22 ± 0.20 GEs = -0.011 ± 0.016 <6% de p, <5% rs (95% CL) R.D.Young, et al, hep-ph/0704.2618 D. Lhuillier - CEA Saclay

  32. Results @ Q2=0.1 GeV/c2 16. Skyrme Model - N.W. Park and H. Weigel, Nucl. Phys. A 451, 453 (1992). 17. Dispersion Relation - H.W. Hammer, U.G. Meissner, D. Drechsel, Phys. Lett. B 367, 323 (1996). 18. Dispersion Relation - H.-W. Hammer and Ramsey-Musolf, Phys. Rev. C 60, 045204 (1999). 19. Chiral Quark Soliton Model - A. Sliva et al., Phys. Rev. D 65, 014015 (2001). 20. Perturbative Chiral Quark Model - V. Lyubovitskij et al., Phys. Rev. C 66, 055204 (2002). 21. Lattice - R. Lewis et al., Phys. Rev. D 67, 013003 (2003). 22. Lattice + charge symmetry -Leinweber et al, Phys. Rev. Lett. 94, 212001 (2005) & hep-lat/0601025 D. Lhuillier - CEA Saclay

  33. Q2 Dependence Proton Data • Small strange quarks contribution at low Q2 • G0 and PVA4 backward results to be released soon • Happex-III likely to run in 2009 D. Lhuillier - CEA Saclay

  34. Projected G0 Results D. Lhuillier - CEA Saclay

  35. Perspectives PRex: APV in elastic e--208Pb scattering (JLab Hall A) Goal: dRn/Rn~1% • Z0 couples mainly to neutrons: • --> new accurate measurement independent of nuclear models, pins down sym. energy • --> Constraint on neutron stars structure C.J. Horowitz, Phys. Rev. C 64, 062802 (2001) D. Lhuillier - CEA Saclay

  36. Perspectives Test of the Standard Model at Low Energy Combining global fit and extrapolation to Q2=0 sets new limits on C1q and constrains new physics at the TeV scale: Qweak @ JLab --> Further improvement by a factor 5 PV-DIS @ JLab • Constraint the C2q axial couplings using isoscalar target • New generation E122 exp. @ JLab R.D.Young, et al, hep-ph/0704.2618 D. Lhuillier - CEA Saclay

  37. MollerJlab Qweak Running of sin2w E158 LEP-SLC k(0)=1.03 sin2eff (E158) = 0.2397 ± 0.0013 D. Lhuillier - CEA Saclay

  38. Summary • Tremendous progress in experimental techniques over last 10 years • Study of the strange nucleon form factors almost completed. Stringent upper limits already set at low Q2. • Weak neutral current at low energy established as a new probe of the nucleon … and the weak interaction itself. • Perspectives at the crossing of nuclear, particle and astro physics with PRex and test of SM at low energy. D. Lhuillier - CEA Saclay

More Related