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

2. Nov 10, 2009Liping Gan, UNCW Contents  Physics Motivation Why η meson is interesting?Why η meson is interesting? η →  0 η →  0  η →  0  0η →  0  0  Suggested experiments at Jlab  Summary

3. Nov 10, 2009Liping Gan, UNCW Why η meson is interesting? One of the Goldstone bosons due to spontaneous chiral symmetry breakingOne of the Goldstone bosons due to spontaneous chiral symmetry breaking The heaviest member in the octet pseudoscalar mesonsThe 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

4. Some Interesting η Rare Decay Channels ModeBranching RatioPhysics Highlight π0 π0π0 π0 <3.5 × 10 − 4 <3.5 × 10 − 4 CP, P π 0 2γ ( 2.7 ± 0.5 ) × 10 − 4 ( 2.7 ± 0.5 ) × 10 − 4 χPTh, Ο(p 6 ) π+ π−π+ π− <1.3 × 10 − 5 <1.3 × 10 − 5 CP, P π0 π0 γπ0 π0 γ <5 × 10 − 4 <5 × 10 − 4 C 3γ3γ <1.6 × 10 − 5 <1.6 × 10 − 5 C π0 π0 π0 γπ0 π0 π0 γ <6 × 10 − 5 <6 × 10 − 5 C π0 e+ e−π0 e+ e− <4 × 10 − 5 <4 × 10 − 5 C 4π04π0 <6.9 × 10 − 7 <6.9 × 10 − 7 CP, P Nov 10, 2009Liping Gan, UNCW

5. Nov 10, 2009Liping Gan, UNCW Study of η →  0  0 Reaction The Origin of CP violation is still a mysteryThe 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 -17CP 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.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 SMUnique test of P and PC symmetries, and search for new physics beyond SM

6. Nov 10, 2009Liping Gan, UNCW Study of the η →  0  Decay A stringent test of the χPTh prediction at Ο(p 6 ) levelA stringent test of the χPTh prediction at Ο(p 6 ) level  Tree level amplitudes (both Ο(p 2 ) and Ο(p 4 )) vanish;  Ο(p 4 ) loop terms involving kaons are suppressed large mass of kaon  Ο(p 4 ) loop terms involving pions are suppressed by G parity  The first sizable contribution comes at Ο(p 6 ) level A long history that experimental results have large discrepancies with theoretic predictions.A long history that experimental results have large discrepancies with theoretic predictions. Current experimental limits in PDG is BR(η →  0  )<4.4x10 -4Current experimental limits in PDG is BR(η →  0  )<4.4x10 -4

7. Nov 10, 2009Liping Gan, UNCW Theoretical Status on η →  0  Average of χPTh 0.42 By E. Oset et al.

8. Nov 10, 2009Liping Gan, UNCW History of the η →  0  Measurements A long standing “η” puzzle is still un-settled. After 1980

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

10. Low energy η production CB experiment at AGS S. Prakhov et al. Phy.Rev.,C78,015206 (2008) The η’s were produced with 720 MeV/c  - beam through the  - p → ηn reactionThe η’s were produced with 720 MeV/c  - beam through the  - p → ηn reaction Decay  ’s energy range: 50-500 MeVDecay  ’s energy range: 50-500 MeV Final result: Final result:  (η →  0   (η →  0  ) = 0.285±0.031±0.061 eV Nov 10, 2009Liping Gan, UNCW η →  0  0  0

11. Nov 10, 2009Liping Gan, UNCW CB Data Analysis II N. Knecht et al. phys. Lett., B589 (2004) 14 Final result Final result  (η →  0 γγ)=0.32±0.15 eV

12. Nov 10, 2009Liping Gan, UNCW Low Energy η Production Continue KLOE experiment B. Micco et al., Acta Phys. Slov. 56 (2006) 403 Produce Φ through ee collision at √s~1020 MeVProduce Φ through e + e - collision at √s~1020 MeV The decay η→  0 γγproceeds through: Φ→  η, η→  0 γγ,  0 →γγThe decay η→  0 γγproceeds through: Φ→  η, η→  0 γγ,  0 →γγ Final result: Final result:  (η →  0 γγ)=0.109±0.035±0.018 eV

13. Nov 10, 2009Liping Gan, UNCW What can be improved at 12 GeV Jlab? High energy tagged photon beam to reduce the background from η → 3  0High 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  0 backgroundTag η by recoiled particles to reduce non-resonance  0  0 background High resolution, high granularity CalorimeterHigh resolution, high granularity Calorimeter  Higher energy resolution → improve  0 γγinvariance mass  Higher granularity → better position resolution and less overlap clusters Large statistics to provide a precision measurement of Dalitz plotLarge statistics to provide a precision measurement of Dalitz plot

14. Nov 10, 2009Liping Gan, UNCW Suggested Experiments in Hall D at Jlab 75 m Counting House Photon TaggerGlueX FCAL η produced on LH 2 target with 11 GeV tagged photon beam γ+p → η+pη produced on LH 2 target with 11 GeV tagged photon beam γ+p → η+p Tag η by measuring recoil p with GlueX detectorTag η by measuring recoil p with GlueX detector Forward calorimeter to detect multi- photons from the η decayForward calorimeter to detect multi- photons from the η decay Simultaneously measure the η →  0 , η →  0  0 :

15. Nov 10, 2009Liping Gan, UNCW Kinematics of Recoil Proton Polar angle ~55 o -80 oPolar angle ~55 o -80 o Momentum ~300-1400 MeV/cMomentum ~300-1400 MeV/c Angle θη (Deg) Recoil P p vs θ η (Deg) Recoil θp (Deg) vs Pp (GeV)

16. Nov 10, 2009Liping Gan, UNCW Reconstructed Missing Mass by GlueX Det.  E  =11.5 Gev ΔP/P=1.5% Δθ=7 mrad Missing Mass (GeV) σ=43 MeV

17. Nov 10, 2009Liping Gan, UNCW Invariant Mass Resolution PWO Pb glass σ=15 MeV σ=6.9 MeV σ=3.2 MeV σ=6.6 MeV  M   0 M  0  M 

18. Nov 10, 2009Liping Gan, UNCW S/N Ratio vs. Calorimeter Granularity PWO d min =4cm S/N=1.4 Pb Glass d min =8cm S/N=0.024

19. Nov 10, 2009Liping Gan, UNCW Rate Estimation The η production rate: LH2 target length L=30cm, ρ=0.0708 g/cm 3The η production rate: LH2 target length L=30cm, ρ=0.0708 g/cm 3 The  +p → η+p cross section ~1 μb The  +p → η+p cross section ~1 μb Photon beam intensity N γ ~1.5x10 7 Hz Photon beam intensity N γ ~1.5x10 7 Hz The η →  0  detection rate: BR(η →  0  )~4x10 -4, detection efficiency ~11.4%The η →  0  detection rate: BR(η →  0  )~4x10 -4, detection efficiency ~11.4%

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 ModelJlab 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  ) andPropose simultaneous measurements on BR(η →  0  ) and BR(η →  0  0 ) will test the χPTh prediction, P and CP symmetries. BR(η →  0  0 ) will test the χPTh prediction, P and CP symmetries. Three experimental techniques will be combined:Three experimental techniques will be combined: 1.A 12 GeV high intensity tagged photon beam to produce η’s. 2.Tag η’s by measuring recoil p with GlueX detector to reduce the  p →  0  0 p background 3.High resolution and high granularity calorimeter to reduce the η →  0  0  0 background

21. The End Nov 10, 2009Liping Gan, UNCW