1 / 33

Primakoff Experiments with EIC

Primakoff Experiments with EIC. Outline Physics motivation: The first experiment at JLab:  0 lifetime Development of precision technique Results for  0 lifetime Experiments with EIC Summary. A. Gasparian NC A&T State University, Greensboro, NC For the PrimEx Collaboration. 1.

bethany-russo
Télécharger la présentation

Primakoff Experiments with EIC

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. Primakoff Experiments with EIC Outline • Physics motivation: • The first experiment at JLab: 0 lifetime • Development of precision technique • Results for 0 lifetime • Experiments with EIC • Summary A. Gasparian NC A&T State University, Greensboro, NC For the PrimEx Collaboration 1

  2. The QCD Lagrangian chiral limit:is the limit of vanishing quark masses mq→ 0. QCD Lagrangian with quark masses set to zero: Large global symmetry group:

  3. Fate of QCD Symmetries

  4. Lightest Pseudoscalar Mesoms • Chiral SUL(3)XSUR(3) spontaneously broken Goldstone mesons π0, η8 • Chiral anomalies Mass of η0 P→γγ ( P: π0, η, η׳) • Quark flavor SU(3) breaking The mixing of π0, η and η׳ The 0, η and η’ system provides a rich laboratory to study the symmetry structure of QCD at low energy.

  5. Experimental program Precision measurements of: Two-Photon Decay Widths: Γ(0→), Γ(→), Γ(’→) Transition Form Factors at low Q2 (0.001-0.5 GeV2/c2): F(*→0), F(* →), F(* →) The PrimEx Experimental Project Test of Chiral Symmetry and Anomalies via the Primakoff Effect 5

  6. Physics Outcome Fundamental input to Physics: • precision test of chiral anomaly predictions • determination of quark mass ratio • -’ mixing angle • 0, and ’ interaction electromagnetic radii • is the ’ an approximate Goldstone boson? 6

  7. First experiment: 0 decay width • 0→ decay proceeds primarily via the chiral anomaly in QCD. • The chiral anomaly prediction is exact for massless quarks: • Corrections to the chiral anomaly prediction: (u-d quark masses and mass differences) Calculations in NLO ChPT: (J. Goity, at al. Phys. Rev. D66:076014, 2002) Γ(0) = 8.10eV ± 1.0% ~4% higher than LO, uncertainty: less than 1% • Recent calculations in QCD sum rule: (B.L. Ioffe, et al. Phys. Lett. B647, p. 389, 2007) • Γ() is only input parameter • 0- mixing included Γ(0) = 7.93eV ± 1.5% 0→ • Precision measurements of (0→) at the percent levelwill provide a stringent test of a fundamental prediction of QCD.

  8. Decay Length Measurements (Direct Method) Measure 0decay length 1x10-16 sec too small to measure solution: Create energetic 0 ‘s, L = vE/m But, for E= 1000 GeV, Lmean 100 μm very challenging experiment 1984 CERN experiment: P=450 GeV proton beam Two variable separation (5-250m) foils Result: (0) = 7.34eV3.1% (total) • Major limitations of method • unknown P0 spectrum • needs higher energies for improvement 0→

  9. e+e- Collider Experiment DORIS II @ DESY e+e-e+e-**e+e-0e+e- e+,e- scattered at small angles (not detected) only  detected Results: Γ(0) = 7.7 ± 0.5 ± 0.5 eV ( ± 10.0%) 0→ • Not included in PDG average • Major limitations of method • knowledge of luminosity • unknown q2 for **

  10. ρ,ω Primakoff Method 12C target Primakoff Nucl. Coherent Nucl. Incoh. Interference Challenge: Extract the Primakoff amplitude from the experimental cross section 10

  11. Previous Primakoff Experiments • DESY (1970) • bremsstrahlung  beam, E=1.5 and 2.5 GeV • Targets C, Zn, Al, Pb • Result: (0)=(11.71.2) eV 10.% • Cornell (1974) • bremsstrahlung  beam E=4 and 6 GeV • targets: Be, Al, Cu, Ag, U • Result: (0)=(7.920.42) eV 5.3% • All previous experiments used: • Untagged bremsstrahlung  beam • Conventional Pb-glass calorimetry

  12. PrimEx Experiment at Hall B JLab • Requirements of Setup: • high angular resolution (~0.5 mrad) • high resolutions in calorimeter • small beam spot size (‹1mm) • Background: • tagging system needed • Particle ID for (-charged part.) • veto detectors needed • JLab Hall B high resolution, high intensity photon tagging facility • New pair spectrometer for photon flux control at high intensities • New high resolution hybrid multi-channel calorimeter (HYCAL)

  13. Fit to Extract Γ(0) Decay Width • Theoretical angular distributions smeared with experimental resolutions are fit to the data 12C 208Pb 13

  14. Estimated Systematic Errors L. Gan APS, April 15, 2008 14

  15. Current PrimEx Result () = 7.93eV2.3%1.6% 15

  16. Next Run 1.4% 16

  17. PrimEx @ High Energies with EIC Experimental program Precision measurements of: Transition Form Factors at low Q2 (0.001-0.5 GeV2/c2): F(*→0), F(* →), F(* →) 17

  18. ρ,ω Primakoff Method 12C target Primakoff Nucl. Coherent Interference Nucl. Incoh. Challenge: Extract the Primakoff amplitude 18

  19. Why do we need high energy? • Increase Primakoff cross section: • Better separation of Primakoff reaction from nuclear processes: • Momentum transfer to the nuclei becomes less reduce the incoherent background

  20. Transition Form Factors at Law Q2 • Direct measurements of slopes: F(*→0), F(* →), F(* →) • Interaction radii: Fγγ*P(Q2) ≈ 1 - 1/6▪<r2>PQ2 • ChPT for large Nc predicts relation between the slopes. • Extraction of Ο(p6) low-energy constant in the chiral Lagrangian • Extraction of decay widths: Γ(0→), Γ(→), Γ(’→) • Precision test of chiral anomaly predictions

  21. Experimental Status for F(*→0) F(*→0) ≈ 1 – a Q2/m2

  22. Experimental Status for F(* →)

  23. PrimEx @ High Energies with EIC Precision Measurement of → decay width • All  decay widths are calculated from  decay width and experimental Branching Ratios (B.R.): Γ(η→ decay) = Γ(→) × B.R. • Any improvement in Γ(→) will change the whole - sector in PDB 23

  24. Determination of quark mass ratio There are two ways to determine the quark mass ratio: • Γ(η→3π) is the best observable for determining the quark mass ratio, which is obtained from Γ(η→γγ) and known branching ratios: • The quark mass ratio can also be given by a ratio of meson masses:

  25. Determination of quark mass ratio Γ(η→3)=Γ(→)×B.R. 25

  26. Mixing Angles • Mixing corrections: • Decayconstant corrections: Γ(η/η´→γγ) widths are crucial inputs for obtaining fundamental mixing parameters.

  27. Summary • It looks possible to perform high precision transition form factor measurements of light pseudoscalar mesons at low Q2 with EIC at high energies • Extrapolation to Q2=0 will define the radiative decay widths: Γ(0→), Γ(→), Γ(’→) • Fundamental input to Physics: • precision test of chiral anomaly predictions • 0, and ’ interaction electromagnetic radii • extraction of Ο(p6) low-energy constant in the chiral Lagrangian • determination of quark mass ratio • -’ mixing angle • is the ’ an approximate Goldstone boson? 27

  28. The End Hall D, March 7, 2008 28

  29. ρ, ω The Primakoff Effect Challenge: Extract the Primakoff amplitude 29

  30. (0→)World Data • 0 is lightest quark-antiquark hadron • The lifetime:  = B.R.( 0 →γγ)/(0 →γγ) 0.8 x 10-16 second ±1% • Branching ratio: B.R. ( 0→γγ)= (98.8±0.032)% 0→ 30

  31. Estimated Systematic Errors 31

  32. Electromagnetic Calorimeter: HYCAL • Energy resolution • Position resolution • Good photon detection efficiency @ 0.1 – 5 GeV; • Large geometrical acceptance PbWO4 crystals resolution Pb-glass budget HYCAL only Kinematical constraint

  33. Beam Time and Statistics • Target: L=20 cm, LHe4 NHe = 4x1023 atoms/cm2 Nγ = 1x107 photon/sec (10-11.5 GeV part) <Δσ(prim.)> = 1.6x10-5 mb N() = NHexNγx<Δσ>xεx(BR) = 4x1023x 1x107x 1.6x10-32x0.7x0.4 = 64 events/hour = 1500 events/day = 45,000 events/30 days • Will provide sub-percent systematic error 15 Days

More Related