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Implications of Br ( m  e g ) and D a m on Muonic Lepton Flavor Violating Processes

Implications of Br ( m  e g ) and D a m on Muonic Lepton Flavor Violating Processes. Chun-Khiang Chua Chung Yuan Christian University. Motivation. Charged lepton flavor violation decays are prohibited in the SM MEG recently set a tight bound on Br ( m  e g )

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Implications of Br ( m  e g ) and D a m on Muonic Lepton Flavor Violating Processes

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  1. Implications of Br(meg) and Damon Muonic Lepton Flavor Violating Processes Chun-Khiang Chua Chung Yuan Christian University

  2. Motivation • Charged lepton flavor violation decays are prohibited in the SM • MEG recently set a tight bound on Br(meg) • Muon g-2 remains an unsolved puzzle (3.xs) (since 2001) • Bounds on meg, 3e, muon to electron conversions (m N e N) are constantly improved (1-6 order of magnitude improvements are expected in future)

  3. Current limits and future sensitivities • “Ratios of current bounds” ~ O(1~10). • Sensitivities will be improved by 1-6 orders of magnitudes in future

  4. We consider… • Muon g-2 and LFV generated by f-yone-loop dig.s: • Use a bottom up approach: data  couplings, masses • Study the correlations among these processes

  5. Investigate Two Cases: • Case I: Cancellations among diagrams are not effective (~order of magnitudes) • Case II: Have some built-in cancellations, e.g. SGIM.

  6. Investigate Two Cases: • Case I: Cancellations among diagrams are not effective (~order of magnitudes) • Case II: Have some built-in cancellations, e.g. SGIM.

  7. Muon g-2 (case I) • gR(L): couplings of mR(L)-y-f int. • gRgR(gLgL) term: • From g2<4p and my,f >100GeV: my,f<300(200)GeV (tight) • g~e: my,f=10-30GeV (disfavored) • gRgL term: (chiral enh.) • From g2<4p and my,f >100GeV: mf<100TeV, my<3000TeV • g~e: my~ 20 TeV • More sensitive than the RR case 10-4 10-5

  8. m LFV (penguins) (case I) 10-8 10-9 Sensitive in RL is more than 3 orders of mag. better than the RR case megbound is most severe

  9. m LFV (penguins) (case I) Exp. bound ratios ~ O(1~10) megconstrains other processes

  10. m LFV (Z-penguins) (case I) • For my=(>)O(100)GeV, Z-peng. has similar (better) sensitivity as the RR g-peng. • Z-peng is less sensitive than the RL g-peng. unless my is as heavy as O(100) TeV • Br(Zme)<10-13~15 [BrUL(Zme)~10-6] 10-4 10-8 Z-peg. g-peg.

  11. m LFV (boxes) (case I) • Dirac and Majoranacases have different sensitivities • me g+perturbativity (+Dam+edm) exclude some (most) parameter space.

  12. Comparing Br(meg) and Dam • The ratio is smaller than any known coupling ratio among 1st and 2nd generations.

  13. Investigate Two Cases: • Case I: Cancellations among diagrams are not effective (~order of magnitudes) • Case II: Have some built-in cancellations, e.g. SGIM.

  14. Muon g-2 (case II) Bend up • d=(dm2/m2)f: mixing angle • gR(L)gR(L) term same as case I • gRgL term: (chiral enh.) • Cancelation is working at the low mf/my mass ratio region • need larger couplings, smaller mass • From g2<4p and my,f >100GeV: mf<100 TeV, my<fewTeV [mf<100TeV, my<3000TeV (case I)] • For g~ e, d=1, mf=my~3TeV [ my=20TeV (case I)] Case II Case I

  15. m LFV (penguins) (case II) meg bound is not always the most stringent one Sensitivities are relaxed

  16. For comparison, recall… m LFV (penguins) (case I) 10-8 10-9 Sensitive in RL is more than 3 orders of mag. better than the RR case megbound is most severe

  17. m LFV (penguins) (case II) meg bound is not always the most stringent one mNeN enhanced relatively (B~10-14 )

  18. m LFV (penguins)(comparing) Case II Case I mNeN is enhanced relatively in case II

  19. m LFV (Z-penguins) (case II) 10-2 10-7 Z-peg. g-peg. • Z-peng. sensitivity is relaxed in the low mass ratio region, for my=(>)O(300~1000)GeV, Z-peng. has similar (better) sensitivity as the RR g-peng. • Z-peng. is less sensitive than the RL g-peng. unless my is as heavy as O(103) TeV (not supported by g-2 [my<fewTeV]) • Z-peng. is subdominant in this case. • Br(Zme)<10-13~15 [BrUL(Zme)~10-6]

  20. m LFV (boxes) (case II) • Dirac and Majorana cases have different sensitivities • me g+perturbativity (+Dam+edm) exclude some (most) parameter space.

  21. Comparing Br(meg) and Dam • Can be satisfied with

  22. Conclusion • Consider y-f loop-induced LFV muon decays. • Bounds are translated to constraints on parameters (couplings and masses) • Muon g-2 favors non-chiral interaction • Z-penguin may play some role Box diagram contributions are highly constrained from other’s • Comparing different cases, we found that: • Case I (no cancellation): • Need fine-tune to satisfy Br(meg) and Dam • m 3e, mNe N bounded by me g (2~3 orders below expt.) • Case II (built-in cancellation): • Mixing angles soften the fine-tune in Br(meg) and Dam • m 3e remains suppressed, butmNe N is enhanced

  23. Back up

  24. m LFV (Z-penguins)

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