Leptoquarks for LFU anomalies

Transcription

1 Leptoquarks for LFU anomalies Nejc Košnik LHCb SemiTau workshop Nov. 14, 17

2 LFU anomalies RD, RD* RK, RK* R(D*) BaBar, PRL109,10180(01) 0.5 Belle, PRD9,07014(015) LHCb, PRL115,111803(015) Belle, PRD94,07007(016) Belle, PRL118,11801(017) LHCb, FPCP017 Average χ = 1.0 contours SM Predictions R(D)=0.300(8) HPQCD (015) R(D)=0.99(11) FNALMILC (015) R(D*)=0.5(3) S. Fajfer et al. (01) σ 4σ R exp K =0.745 ± ±0.036 exp,low q RK = ± 0.04 (In SM = 1 ± %) exp,central q RK = ± HFLAV FPCP 017 P(χ ) = 71.6% R(D) [Belle ]

3 Sensitivity to new physics scale Both effects are ~0% correction to the amplitude. Naive scale sensitivity. RD (*) RK (*) Λ = 3 TeV (tree-level V-A) V cb v vs. 1 C9 = -1 Λ = 3 TeV (1-loop NP) V ts (4 ) v vs. 1 (4 ) Λ = 30 TeV (tree-level NP) V ts (4 ) v vs. 1 However, dimensionless couplings of NP are arbitrary parameters, so the scales just reflect different sensitivity to NP. Signals either: 1) tree for RD, loop for RK ) different scales responsible for the two processes 3) same scale, flavor coupling hierarchy of NP 3

4 Light leptoquarks LQ = color triplet Couplings with SM fermions - lepton, quark, LQ (F=1) b τ F=0 quark, quark, LQ (F=) [color 3x3x3] c ν spin SU(3)xSU()xU(1) F=3B+L B L vectors scalars V(3,,56) V(3,,-16) U3(3,3,3) U1(3,1,3) S1(3,1,-13) S3(3,3,-13) R(3,,76) R(3,,16)* S1(3,1,43) L=0, B=3 L=1, B=13 F= p M 0 l, M + ν F = LQs destabilize proton (baryon number violation) 4 R (3) R (-13) R (-13) p M + M + lνν h

5 R R (3,, 76) lr YR Q ū RZ(i R T )L b τ c ν Tree level RD(*) : RD works with real, RD-RD* with complex couplings L = ybτ 3 zuτ 4G F V p cb h(1 + g V )( µ L L )( c L µ b L ) i + g S ( R L )( c R b L )+g T ( µ R L )( c R µ b L ) ( `RYd L )R (3) +ū R Z L R (3) ( `R[YV ]u L )R (53) (ū R Z`L)R (53) g S (m b )=0.14g T (m b ) (0.5 without QCD corrections) [Sakaki,Watanabe, Tanaka,Tayduganov, ] [Freytsis, Ligeti, Ruderman, ] 5 see also [Becirevic, NK, Tayduganov, ] [Dorsner, Fajfer, NK, Nisandzic, ]

6 R R (3,, 76) lr YR Q ū RZ(i R T )L ( `RYd L )R (3) +ū R Z L R (3) ( `R[YV ]u L )R (53) (ū R Z`L)R (53) RK(*) at tree-level: C9 = C10 RK(*) at loop-level: C9 = -C10 Z = z cµ z c A 0 z tµ z t B! Kµµ high q B s! µµ B! K µµ high q P 1,,3 low,high q [Becirevic, Sumensari, ]

7 RK(*) at loop-level: C9 = -C10 R R (3,, 76) lr YR Q ū RZ(i R T )L ( `RYd L )R (3) +ū R Z L R (3) ( `R[YV ]u L )R (53) (ū R Z`L)R (53) Importance of Z μμ constraint! [Becirevic, Sumensari, ] Couplings needed for RK(*) incompatible with RD(*)

8 S3 S 3 (3, 3, 13) L = y ij QC i i S 3 L j + z ij QC i i ( S 3 ) Q j Left-handed couplings Diquark couplings.? If S3 is part of a Grand Unified scalar field, we can avoid diquark couplings. We need a second LQ light state, ~R, to ensure unification. S3(3,3,-13) F= GUT scalar representations: R(3,,16) F=0 L = ỹ ij dri R i L j 5 = (1,,1) (3,1,-13) doublet-triplet 15 = (1,3,1) (3,,16) (6,1,-3) 4 = (8,1,0) (1,3,0) (3,,-56) (3,,56) (1,1,0) 45 = (8,,1) (6*,1,-13) (3,3,-13) (3*,,-76) (3,1,-13) (3*,1,43)

9 S3 orand ~R Require S3 and R to be light, and impose unification of couplings at 1-loop B ij = X J (b J i b J j )r J B 3 B 1 SM =0.53 r J = log(m GUTm J ) log(m GUT m Z ) Both fields have positive b J - b J 3 and negative b J 1 - b J, they tend to aid unification. Furthermore, the GUT scale is raised Yukawas of S3 do not contain diquark couplings, thanks to GUT symmetry. Baryon number is conserved L = y ij QC i i S 3 L j + z ij QC i i ( S 3 ) Q j L = ỹij dri R i L j

10 S3 features - RK(*) and RD(*) Interactions in mass basis of fermions L = y ij dc i L j L S13 3 p yij dc i L e j L S p (V y) ij ū Ci L j L S 3 3 (V y) ij ū Ci L e j L S13 3 y = y sµ y s A 0 y bµ y b RK(*) [ 0.81, 0.50] y bµ y sµ [0.7, 1.3] 10 3 (m S3 TeV) RD(*) b S3 13 ν L cb ` k = 4G F p "(V cb `k + gcb;`k)( c L µ L b L )( `L µ L) k #. V ( ) cb V (µ) cb = c 1 v m S 3 1 v m S 3 l V cs V cb y s y b + y b V cs V cb y sµ y bµ + y bµ 1.3 Need large sτ-bτ andor large bμ 10

11 S3 and RD(*) V ( ) cb V (µ) cb = 1 v m S 3 1 v m S 3 V cs V cb y s y b + yb V cs V cb y sµ y bµ + y bµ 1.3 Exercise: try to explain RD(*) with muonic couplings Two limiting factors: [Belle , ] pp! µ + µ high pt tails [Greljo, Marzocca 17] 11

12 S3 and RD(*) V ( ) cb V (µ) cb = 1 v m S 3 1 v m S 3 V cs V cb y s y b + yb V cs V cb y sµ y bµ + y bµ 1.3 Expand the analysis to tauonic couplings Positive correlation with leptonic decay: Two limiting factors for large ysτ ybτ: 1) ) Rνν = B(B K(*)νν)B(B K(*)νν)SM [Fajfer, Dorsner, NK, Faroughy, ] 1

13 S3 and LHC High mass ττ searches at ATLAS 13

14 ~R features - RK(*) and RD(*) RK C 0 9 = C 0 10 No RK*: RH current implies RK* > 1 if RK < 1 RD: By adding a right-handed neutrino L = d R 0 YL ( e ) L 0 + Q 0 Y R 0 R R L = d R (Y L U PMNS ) L ( 13) d R Y L`L (3) + u L (V CKM Y R ) R (3) + d L Y R R ( 13) gate to semileptonic 14

15 ~R features - RD L e = p G F V ud u µ P L d ` µp L + g S up R d`p R + g T u µ P R d` µ P R RD leptonic constraints K μν, τ Kν, Ds τν, Ds μν, B τν Modification of semi-muonic and semitauonic Only possible with form factors for B Dlν 15

16 ~R - LHC [Faroughy, Greljo, Kamenik 16] pp(bb ) τ τ searches probes only left-handed couplings ΓmLQ < 1 is a stronger constraint 16

17 ~R predictions 1.0< < LPT, Orsay, Nov

18 Bottomline on S3 and ~R RK* explained by S3 RD accommodated by ~R (and νr) Both are part of SU(5) GUT setup Possibility of radiative generation of neutrino masses R 13 H S 1,S 13 3 λ 1,λ 3 H S R 3 S 3 3 κ ν L ν L ν L d ỹ RL y1 LL,yLL 3 ν L u VCKM yll y RL 3 RD* : strong constraints from interplay B Kνν, LHC direct searches, lepton universality in μe, 18