Model-Independent Constraints on Lepton-Flavor-Violating Decays of - PowerPoint PPT Presentation

Model-Independent Constraints on Lepton-Flavor-Violating Decays of the Top Quark Jennifer Kile, Amarjit Soni Brookhaven National Laboratory Pheno ’08, April 28, 2008

Introduction LHC: huge top physics potential ( 10 8 t ’s!). t unique, good place to look for New Physics (NP). Neutrino osc: Nature has lepton flavor violation. t → u ( c ) e ± µ ∓ : distinctive experimental signature. Are there experimental constraints on NP contributions to t → u ( c ) e ± µ ∓ ? Take set of effective operators C i � L eff = Λ d − 4 O i + h.c. i to get constraints from B, K decays and µ → eγ . Model-Independent Constraints on Lepton-Flavor-Violating Decays of the Top Quark – p.1/10

Operators Contributing to t → u ( c ) e ± µ ∓ Take dimension-6, SU (3) × SU (2) × U (1) -invariant op’s. Separate into 2 classes, depending on T L or t R in operator. Class One : Class Two : ¯ L γ µ T L ¯ L j R γ µ t R ¯ L j u i L γ µ L k Q i L γ µ L k O 1 ,ijk = ¯ O 5 ,ijk = L L ¯ L γ µ T L ¯ R γ µ t R ¯ l j l j Q i R γ µ l k u i R γ µ l k O 6 ,ijk = O 2 ,ijk = ¯ R R ǫ ab ¯ La t R ¯ L j j L k R T La ¯ Q i Lb l k ǫ ab ¯ u i O 3 ,ijk = O 7 ,ijk = l R R Lb ǫ ab ¯ La σ µν t R ¯ L j j σ µν L k R σ µν T La ¯ Q i Lb σ µν l k ǫ ab ¯ u i O 4 ,ijk = O 8 ,ijk = l R R Lb i = u, c ; j, k = eµ, µe Q L , L L , T L : l.h. doublets a, b = SU (2) indices u R , l R , t r : r.h. singlets Model-Independent Constraints on Lepton-Flavor-Violating Decays of the Top Quark – p.2/10

Contributions of Op’s to t → u ( c ) e ± µ ∓ Top decay for all op’s proceeds via e − , µ − e − , µ − e − , µ − e − , µ − u, c u, c u, c u, c t t t t µ + , e + µ + , e + µ + , e + µ + , e + Assume can measure branching ratio of 10 − 7 . Taking m t = 170 GeV and | C n,ijk | = 1 , 2 . 1 TeV ( n = 1 , 2 , 5 , and 6 ) TeV ( n = 3 and 7 ) Λ ≥ 1 . 5 4 . 0 TeV ( n = 4 and 8 ) Results independent of flavor indices i, j, k . Model-Independent Constraints on Lepton-Flavor-Violating Decays of the Top Quark – p.3/10

Constraints from B decays Class Two op’s contain T L , include terms with b quarks. l j l j ex: O 6 ,ijk = ¯ L γ µ T L ¯ L γ µ t L + ¯ L γ µ b L )¯ Q i R γ µ l k u i d i R γ µ l k R = (¯ R → contribute at tree-level to B decay. ¯ ¯ e − , µ − ν e , ν µ b b 2-body µ + , e + µ + , e + s, d c, u ( b ) ( a ) e + , µ + e + , µ + µ − , e − ν µ , ν e ¯ s, ¯ ¯ ¯ ¯ c, ¯ 3-body b d b u u u, d ( a ) ( b ) Model-Independent Constraints on Lepton-Flavor-Violating Decays of the Top Quark – p.4/10

Constraints from 2-body B decays √ The Class Two op’s contribute to ( � 0 | ¯ dγ µ γ 5 b | B 0 ( p ) � = i 2 F B p µ ): | C n,ijk | 2 1 B 0 , B s → e ± µ ∓ , F 2 B m B m 2 Op’s 5 , 6 : Γ = µ Λ 4 32 π (helicity-suppressed) | C n,ijk | 2 m 5 1 B + , B c → ℓ + ν , F 2 Op 7: Γ = B Λ 4 ( m b + m u ( c ) ) 2 32 π B Op 8: 0 (tensor operator) 1 . 7 × 10 − 7 (90% CL ) → | C 5(6) ,ujk | 1 Br ( B 0 → e ± µ ∓ ) ≤ ≤ Λ 2 TeV ) 2 (3 . 7 6 . 1 × 10 − 6 (90% CL ) → | C 5(6) ,cjk | 1 Br ( B s → e ± µ ∓ ) ≤ ≤ Λ 2 TeV ) 2 (1 . 6 9 . 8 × 10 − 6 (90% CL ) → | C 7 ,uµe | 1 Br ( B + → e + ν ) ≤ ≤ Λ 2 TeV ) 2 (17 1 . 7 × 10 − 6 (90% CL ) → | C 7 ,ueµ | 1 Br ( B + → µ + ν ) ≤ ≤ Λ 2 TeV ) 2 (11 Model-Independent Constraints on Lepton-Flavor-Violating Decays of the Top Quark – p.5/10

Constraints from 3-body B decays → No helicity suppression, op 8 can contribute. Op’s 5,6: Compare to exclusive via B → πℓ + ν . 6 . 4 × 10 − 3 → | C 5(6) ,ujk | 1 Br ( B + → π + e + µ − ) ≤ ≤ Λ 2 TeV ) 2 (1 9 . 1 × 10 − 8 → | C 5(6) ,cjk | 1 Br ( B + → K + e ± µ ∓ ) ≤ ≤ Λ 2 TeV ) 2 (16 Op’s 7,8: Take 2 × exp. error as estimate of NP contribution. | C 7 ,ujk | 1 Br ( B → X u ℓ + ν ) = 2 . 33 ± . 22 × 10 − 3 → ≤ Λ 2 TeV ) 2 (3 | C 8 ,ujk | 1 ≤ Λ 2 TeV ) 2 (7 | C 7 ,ceµ | 1 Br ( B − → X c e + ν ) = 10 . 8 ± 0 . 4 → ≤ Λ 2 TeV ) 2 (1 | C 8 ,ceµ | 1 ≤ Λ 2 TeV ) 2 (3 Model-Independent Constraints on Lepton-Flavor-Violating Decays of the Top Quark – p.6/10

Constraints from K decays s, ¯ ¯ e − , µ − d Op’s of both classes i.e., u, c can contribute at one loop to K L → e ± µ ∓ : t µ + , e + d, s ln v 2 | C 5(6) ,ujk (Λ) | 1 Br ( K L → e ± µ ∓ ) ≤ 4 . 7 × 10 − 12 → Λ 2 < Λ 2 (2 . 3 TeV ) 2 ln v 2 | C 5(6) ,cjk (Λ) | 1 Λ 2 < Λ 2 (1 . 6 TeV ) 2 | C 4 ,ujk | 1 � Λ 2 (1 TeV ) 2 Constraints from 3-body K decays weaker. Model-Independent Constraints on Lepton-Flavor-Violating Decays of the Top Quark – p.7/10

µ → eγ Ops 3, 4 can contribute to µ → eγ at 2 loops, i.e., γ γ W W u L , c L d L , b L t R t R µ L µ L e R e R ν µ Br ( µ → eγ ) < 1 . 2 × 10 − 11 → yet to come Model-Independent Constraints on Lepton-Flavor-Violating Decays of the Top Quark – p.8/10

Results t → u ( c ) e ± µ ∓ Operator B , 2-body B , 3-body K µ → eγ O 1(2) ,ijk 2.1 - - - - O 3 ,ijk 1.5 - - - maybe O 4 ,ujk 4.0 - - 1 maybe O 4 ,cjk 4.0 - - - maybe O 5(6) ,ujk 2.1 3.7 1 6 - O 5(6) ,cjk 2.1 1.6 16 3.7 - O 7 ,ueµ 1.5 11 3 - - O 7 ,uµe 1.5 17 3 - - O 7 ,ceµ 1.5 - 1 - - O 7 ,cµe 1.5 - - - - O 8 ,ujk 4.0 - 7 - - O 8 ,ceµ 4.0 - 3 - - O 8 ,cµe 4.0 - - - - Model-Independent Constraints on Lepton-Flavor-Violating Decays of the Top Quark – p.9/10

Conclusions Operators which can give t → u ( c ) e ± µ ∓ probe ∼ few TeV range. Several operators constrained by B , K decays, possibly µ → eγ . Some operators currently not constrained. t → u ( c ) e ± µ ∓ could occur at LHC! Model-Independent Constraints on Lepton-Flavor-Violating Decays of the Top Quark – p.10/10