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Search for New Physics via η Rare Decay

Search for New Physics via η Rare Decay. Liping Gan University of North Carolina Wilmington Wilmington, NC, USA. Contents. Physics Motivation Why η meson is interesting? η →  0  η →  0  0 Suggested experiments at Jlab Summary. Why η meson is interesting?.

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Search for New Physics via η Rare Decay

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  1. Search for New Physics via η Rare Decay LipingGan University of North Carolina Wilmington Wilmington, NC, USA

  2. Contents • Physics Motivation • Why η meson is interesting? • η→0 • η→00 • Suggested experiments at Jlab • Summary Liping Gan, UNCW

  3. Why η meson is interesting? • One of the Goldstone bosons due to spontaneous chiral symmetry breaking • The heaviest member in the octet pseudoscalar mesons • Provide a rich program to investigate evidences of symmetry breaking and the new physics beyond the Standard Model Liping Gan, UNCW

  4. Some Interesting η Rare Decay Channels Liping Gan, UNCW

  5. Study ofη→0 0 Reaction • The Origin of CP violation is still a mystery • CP violation is described in SM by the phase in the Cabibbo-Kobayashi-Maskawa quark mixing matrix. A recent SM calculation predicts BR(η→0 0)<3x10-17 • The η→0 0 is one of a few available flavor-conserving reactions listed in PDG to test CP violation. • Unique test of P and PC symmetries, and search for new physics beyond SM Liping Gan, UNCW

  6. Study of theη→0Decay • A stringent test of the χPTh prediction at Ο(p6) level • Tree level amplitudes (both Ο(p2) and Ο(p4)) vanish; • Ο(p4) loop terms involving kaons are suppressed large mass of kaon • Ο(p4) loop terms involving pions are suppressed by G parity • The first sizable contribution comes at Ο(p6) level • A long history that experimental results have large discrepancies with theoretic predictions. • Current experimental limits in PDG is BR(η→0 )<4.4x10-4 Liping Gan, UNCW

  7. Theoretical Status on η→0 By E. Oset et al. Average of χPTh 0.42 Liping Gan, UNCW

  8. History of the η→0 Measurements After 1980 A long standing “η” puzzle is still un-settled. Liping Gan, UNCW

  9. High Energy η ProductionGAMS Experiment at SerpukhovD. Alde et al., Yad. Fiz 40, 1447 (1984) • Experimental result was first published in 1981 • The η’s were produced with 30 GeV/c- beam in the -p→ηn reaction • Decay ’s were detected by lead-glass calorimeter Final result: (η→0 ) = 0.84±0.17 eV • Major Background • -p→ 00n • η →000 Liping Gan, UNCW

  10. Low energy η production CB experiment at AGSS. Prakhovet al. Phy.Rev.,C78,015206 (2008) η →000 • The η’s were produced with 720MeV/c - beam through the -p→ηn reaction • Decay ’s energy range: 50-500 MeV • Final result: • (η→0 ) = 0.285±0.031±0.061 eV Liping Gan, UNCW

  11. CB Data Analysis II N. Knechtet al. phys. Lett., B589 (2004) 14 • Final result • (η→0γγ)=0.32±0.15 eV Liping Gan, UNCW

  12. Low Energy η Production Continue KLOE experiment B. Micco et al., Acta Phys. Slov. 56 (2006) 403 • Produce Φ through e+e- collision at √s~1020 MeV • The decay η→0γγproceeds through: Φ→η, η→0γγ, 0→γγ • Final result: • (η→0γγ)=0.109±0.035±0.018 eV Liping Gan, UNCW

  13. What can be improved at 12 GeVJlab? • High energy tagged photon beam to reduce the background from η→ 30 • Lower relative threshold for -ray detection • Improve calorimeter resolution • Tag η by recoiled particles to reduce non-resonance 00background • High resolution, high granularity Calorimeter • Higher energy resolution → improve 0γγinvariance mass • Higher granularity→ better position resolution and less overlap clusters • Large statistics to provide a precision measurement of Dalitz plot Liping Gan, UNCW

  14. Suggested Experiments in Hall D at Jlab FCAL Photon Tagger GlueX • η produced on LH2 target with 11 GeV tagged photon beam γ+p → η+p • Tag η by measuring recoil p with GlueX detector • Forward calorimeter to detect multi-photons from the η decay Counting House Simultaneously measure the η→0, η →00: 75 m LipingGan, UNCW

  15. Kinematics of Recoil Proton Recoil Pp vsθη (Deg) Angle θη (Deg) • Polar angle ~55o-80o • Momentum ~300-1400 MeV/c Recoil θp (Deg) vs Pp (GeV) Liping Gan, UNCW

  16. Reconstructed Missing Mass by GlueX Det. E=11.5 Gev ΔP/P=1.5% Δθ=7 mrad σ=43 MeV Missing Mass (GeV) Liping Gan, UNCW

  17. Invariant Mass Resolution σ=6.9 MeV σ=3.2 MeV PWO M0 M σ=6.6 MeV σ=15 MeV Pb glass M M0 Liping Gan, UNCW

  18. S/N Ratio vs. Calorimeter Granularity PWO dmin=4cm S/N=1.4 Pb Glass dmin=8cm S/N=0.024 Liping Gan, UNCW

  19. Rate Estimation • The η production rate:LH2 target length L=30cm, ρ=0.0708 g/cm3 • The +p→η+p cross section ~1 μb • Photon beam intensity Nγ~1.5x107 Hz • The η→0 detection rate: BR(η→0 )~4x10-4 , detection efficiency ~11.4% Liping Gan, UNCW

  20. Summary • Jlab 12 GeV with GlueX setup will provide a great opportunity for precise measurements of various η rare decays to test P, CP and C symmetries, and search for new physics beyond the Standard Model • Propose simultaneous measurements on BR(η→0) and BR(η →00) will test the χPTh prediction, P and CP symmetries. • Three experimental techniques will be combined: • A 12 GeV high intensity tagged photon beam to produce η’s. • Tag η’s by measuring recoil p with GlueX detector to reduce the p→ 00p background • High resolution and high granularity calorimeter to reduce the η →000background

  21. The End Liping Gan, UNCW

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