Flavor Violating Higgs Decays

Transcription

1 Flavor Violating Higgs Decays Joachim Kopp Galileo Galilei Institute November 26, 2012 Based on work done in collaboration with Roni Harnik and Jure Zupan arxiv: Joachim Kopp Flavor Violating Higgs Decays 1

2 Outline 1 Flavor mixing in the Higgs sector 2 Couplings to leptons 3 Couplings to quarks 4 Flavor-violating Higgs decays at the LHC 5 Summary Joachim Kopp Flavor Violating Higgs Decays 2

3 Flavor Mixing in the Higgs Sector

4 Motivation Scenario 1: Several sources of EW symmetry breaking If fermion masses have more than one origin, they do not need to be aligned with the Yukawa couplings Simplest example: Type III 2-Higgs-Doublet Model L Y Y (1) ij L i e j R H(1) Y (2) ij L i e j R H(2) + h.c. i f L f j R m i ē i Le i R Y eff ij (h = Lightest neutral Higgs boson, m h 125 GeV) Assume heavy Higgs boson are decoupled. h + couplings to heavier Higgs bosons + h.c. see for instance Davidson Greiner, arxiv: Joachim Kopp Flavor Violating Higgs Decays 4

5 Motivation (2) Scenario 2: Extra Higgs couplings Assume existence of heavy new particles, which induce effective operators of the form L Y = λ ij Λ 2 ( f i Lf j R )H(H H) + h.c. +, after EWSB, new (but misaligned) contributions to mass matrices and Yukawa couplings Effective Lagrangian is again L Y m i ēle i R i Yij eff i f L f j R h + h.c. see for instance Giudice Lebedev, arxiv: Joachim Kopp Flavor Violating Higgs Decays 5

6 Effective Yukawa Lagrangfian Effective Yukawa Lagrangian L Y = m i f i L f i R Y a ij ( f i Lf j R )ha + h.c. + Previously studied by many authors: Bjorken Weinberg, PRL 38 (1977) 622 McWilliams Li, Nucl. Phys. B 179 (1981) 62 Shanker, Nucl. Phys. B 206 (1982) 253 Barr Zee, PRL 65 (1990) 21 Babu Nandi, hep-ph/ Diaz-Cruz Toscano, hep-ph/ Han Marfatia, hep-ph/ Kanemura Ota Tsumura, hep-ph/ Blanke Buras Duling Gori Weiler, arxiv: Casagrande Goertz Haisch Neubert Pfoh, arxiv: Giudice Lebedev, arxiv: Aguilar-Saavedra, arxiv: Albrecht Blanke Buras Duling Gemmler, arxiv: Buras Duling Gori, arxiv: Azatov Toharia Zhu, arxiv: Agashe Contino, arxiv: Davidson Greiner, arxiv: Goudelis Lebedev Park, arxiv: Blankenburg Ellis Isidori, arxiv: Arhrib Cheng Kong, arxiv: McKeen Pospelov Ritz, arxiv: Joachim Kopp Flavor Violating Higgs Decays 6

7 Effective Yukawa Lagrangfian Effective Yukawa Lagrangian L Y = m i f i L f i R Y a ij ( f i Lf j R )ha + h.c. + New in this talk: Comprehensive list of up-to-date constraints (including subdominant ones) Omit approximations where feasible First LHC limits Strategy for future LHC searches Joachim Kopp Flavor Violating Higgs Decays 6

8 Couplings to Leptons

9 Low-energy constraints on LFV in the Higgs sector h µ e Yeµ PL + YµePR µ µ τ Y µτ PL + YτµPR Y τµpl + YµτPR τ µ τ h YµµPL + YµµPR µ µ + h Yeµ PL + YµePR e + γ g 2, EDMs τ Yτµ PL + YµτPR τ 3µ, µee, etc. µ µ µ M M oscillations τ τ Y ττpl + YττPR h τ Y τµpl + YµτPR µ h t γ, Z t µ Yµe PL + YeµPR e τ µ γ µ τ γ µ µ h h γ, Z h γ, Z N N W W W W µ e conversion γ τ µγ, µ eγ, etc. γ Joachim Kopp Flavor Violating Higgs Decays 8

10 Constraints on h µe Μ 3e M M g 2 e EDM e g 2 e for Im Y Μe Y eμ 0 YΜe Μ e conv. Μ eγ Assumption here: Diagonal Yukawa coupling unchanged from their SM values. EDM e for Re Y Μe Y eμ 0 Y Μe Y eμ m e m Μ v Y eμ BR h Μe 0.99 see also: Blankenburg Ellis Isidori, arxiv: Goudelis Lebedev Park, arxiv: Joachim Kopp Flavor Violating Higgs Decays 9

11 Constraints on h τµ and h τe YΤΜ 10 0 Τ 3 Μ Y ΤΜ Y ΜΤ m Μ m Τ v 2 Τ ΜΓ Y ΜΤ g 2 Μ Im Y ΤΜ Y ΜΤ 0 g 2 Μ EDM Μ BR h ΤΜ 0.99 YΤe Τ eμμ Y Τe Y eτ m e m Τ v 2 EDM e Re Y Τe Y eτ g 2 e EDM e g 2 e for Im Y Τe Y eτ Y eτ Τ eγ 0.5 BR h Τe 0.99 Substantial flavor violation (BR(h τµ, τe) 0.01) perfectly viable. Assumption here: Diagonal Yukawa coupling unchanged from their SM values. see also: Blankenburg Ellis Isidori, arxiv: Goudelis Lebedev Park, arxiv: Davidson Greiner, arxiv: Joachim Kopp Flavor Violating Higgs Decays 10

12 Couplings to Quarks

13 Constraints on Higgs couplings to light quarks Tight constraints from neutral meson oscillations b Ybd PL + YdbPR d c Y ctp L + Y tcp R h Y tup L + Y utp R u h t t d Ybd PL + YdbPR b ū Y tup L + Y utp R h Y ctp L + Y tcp R c Joachim Kopp Flavor Violating Higgs Decays 12

14 Constraints on Higgs couplings to light quarks Tight constraints from neutral meson oscillations Work in Effective Field Theory: H eff = C2 db ( b R d L ) 2 db + C 2 ( b L d R ) 2 + C4 db ( b L d R )( b R d L ) +... Wilson coefficients constrained in UTfit (Bona et al.), arxiv: see also Blankenburg Ellis Isidori, arxiv: Technique Coupling Constraint D 0 oscillations Y uc 2, Y cu 2 < Y uc Y cu < B 0 d oscillations Y db 2, Y bd 2 < Y db Y bd < B 0 s oscillations K 0 oscillations Y sb 2, Y bs 2 < Y sb Y bs < R(Yds 2 ), R(Y sd 2 ) I(Yds 2 ), I(Y sd 2 ) R(Yds Y sd) I(Yds Y sd) [ ] [ ] [ ] [ ] Joachim Kopp Flavor Violating Higgs Decays 12

15 Couplings involving top quarks Ytq q c, u t hq limit Craig et al Y qt q c, u BR h t q BR t hq single top bound on Y ut, Y tu single top bound on Yct, Y tc Constraints from Single top production t t Y ttpl + YttPR h g t Y tqpl + YqtPR CDF , DØ ATLAS t hq Craig et al based on CMS multilepton search Not sensitive t Zq q CMS Joachim Kopp Flavor Violating Higgs Decays 13

16 Flavor-Violating Higgs Decays at the Large Hadron Collider

17 h τµ and h τe at the LHC Basic idea: h τl has the same final state as h ττ l (but is enhanced by 1/BR(τ l)) Recast h ττ search here: ATLAS, arxiv: We consider only 2-lepton final states Use VBF cuts (much lower BG than gg fusion) see however Davidson Verdier, arxiv: Events 10 GeV based on ATLAS, arxiv: ATLAS 4.7 fb 1 ATLAS MC ATLAS data 5 H Τ Τ 5 H Τ Μ Y ΜΤ 2 Y ΤΜ m Τ v ΤΤ collinear mass m ΤΤ GeV Joachim Kopp Flavor Violating Higgs Decays 15

18 h τµ and h τe at the LHC Most important cuts 2 forward jets (p T,j1 > 40 GeV, p T,j2 > 25 GeV, η > 3.0, m inv j1,j2 > 350 GeV) no hard jet activity in between no b tags 2 opposite sign leptons l 1, l 2 with p T,l GeV (depending on flavors) τ momentum fraction x carried by l 1, l 2 satisfies 0.1 < x 1,2 < 1.0 (computed in collinear approximation) 30 GeV < m ll < 75 (100) GeV for same (opposite) flavor leptons /E T > 20 (40) GeV for same (opposite) flavor leptons Events 10 GeV based on ATLAS, arxiv: ATLAS 4.7 fb 1 ATLAS MC ATLAS data 5 H Τ Τ 5 H Τ Μ Y ΜΤ 2 Y ΤΜ m Τ v ΤΤ collinear mass m ΤΤ GeV Joachim Kopp Flavor Violating Higgs Decays 15

19 Mass reconstruction for h τ l τ l Problem: 4 neutrinos in final state Solution: Assume all τ decay products collinear Ellis Hinchliffe Soldate van der Bij, NPB 1987 Per τ: 2 unknown ( p ντ, p νl ) 2 constraints: /E T,x, /E T,y Joachim Kopp Flavor Violating Higgs Decays 16

20 Limits on h τµ and h τe from the LHC Technicalities Use MadGraph 5, v1.4.6, Pythia 6.4, PGS Use only GeV bin Derive one-sided 95% CL limit Events 10 GeV based on ATLAS, arxiv: ATLAS 4.7 fb 1 ATLAS MC ATLAS data 5 H Τ Τ 5 H Τ Μ Y ΜΤ 2 Y ΤΜ m Τ v ΤΤ collinear mass m ΤΤ GeV Result BR(h τµ) < 0.13 BR(h τe) < 0.13 Yτµ 2 + Yµτ 2 < Yτe 2 + Yeτ 2 < Joachim Kopp Flavor Violating Higgs Decays 17

21 LHC constraints on h τµ and h τe YΤΜ 10 0 Τ 3 Μ Y ΤΜ Y ΜΤ m Μ m Τ v 2 Τ ΜΓ Y ΜΤ g 2 Μ Im Y ΤΜ Y ΜΤ 0 g 2 Μ EDM Μ BR h ΤΜ 0.99 YΤe Τ eμμ Y Τe Y eτ m e m Τ v 2 EDM e Re Y Τe Y eτ g 2 e EDM e g 2 e for Im Y Τe Y eτ Y eτ Τ eγ 0.5 BR h Τe 0.99 Joachim Kopp Flavor Violating Higgs Decays 18

22 LHC constraints on h τµ and h τe YΤΜ 10 0 ATLAS 7 TeV, 4.7 fb 1 Τ 3 Μ Our LHC limit Y ΤΜ Y ΜΤ m Μ m Τ v 2 Τ ΜΓ Y ΜΤ g 2 Μ Im Y ΤΜ Y ΜΤ 0 g 2 Μ EDM Μ BR h ΤΜ 0.99 YΤe Τ eμμ Our LHC limit ATLAS 7 TeV, 4.7 fb 1 Y Τe Y eτ m e m Τ v 2 EDM e Re Y Τe Y eτ g 2 e EDM e g 2 e for Im Y Τe Y eτ Y eτ Τ eγ 0.5 BR h Τe 0.99 Joachim Kopp Flavor Violating Higgs Decays 18

23 LHC constraints on h τµ and h τe YΤΜ 10 0 ATLAS 7 TeV, 4.7 fb 1 Τ 3 Μ Our LHC limit Y ΤΜ Y ΜΤ m Μ m Τ v 2 Τ ΜΓ Y ΜΤ g 2 Μ Im Y ΤΜ Y ΜΤ 0 g 2 Μ EDM Μ BR h ΤΜ 0.99 YΤe 10 0 ATLAS 7 TeV, 4.7 fb Τ eμμ Our LHC limit Y Τe Y eτ m e m Τ v 2 EDM e Re Y Τe Y eτ 0 g 2 e EDM e g 2 e for Im Y Τe Y eτ 0 WORLD S BEST LIMIT! Y eτ Τ eγ 0.5 BR h Τe 0.99 Joachim Kopp Flavor Violating Higgs Decays 18

24 Strategy for a dedicated h τµ and h τe search Possible improvements Different invariant mass formula (assuming 1 neutrino rather than 3) Avoids smearing of signal Shifts Z ττ peak to lower invariant mass Consider hadronic τ s (especially for CMS) Modified cuts CMS h τhad τ l search requires m T (l, /p T ) < 40 GeV to suppress W + jets In h τhad µ, neutrino and muon typically not collinear large m T (l, /p T ) Joachim Kopp Flavor Violating Higgs Decays 19

25 Strategy for a dedicated h τµ and h τe search Possible improvements Different invariant mass formula (assuming 1 neutrino rather than 3) Avoids smearing of signal Shifts Z ττ peak to lower invariant mass Consider hadronic τ s (especially for CMS) Modified cuts CMS h τhad τ l search requires m T (l, /p T ) < 40 GeV to suppress W + jets In h τhad µ, neutrino and muon typically not collinear large m T (l, /p T ) Events 10 GeV fb 1, 7 TeV MG Pythia Delphes W jets Z jets h Τ had Τ Μ h Τ had Μ Y ΜΤ 2 Y ΤΜ m Τ v QCD BG neglected BG rescaled to CMS-HIG Joachim Kopp Flavor Violating Higgs Decays 19

26 Strategy for a dedicated h τµ and h τe search Events 10 GeV fb 1, 7 TeV MG Pythia Delphes W jets Z jets h Τ had Τ Μ h Τ had Μ Y ΜΤ 2 Y ΤΜ m Τ v QCD BG neglected BG rescaled to CMS-HIG Events 10 GeV fb 1, 7 TeV MG Pythia Delphes W jets Z jets h Τ had Τ Μ h Τ had Μ Y ΜΤ 2 Y ΤΜ m Τ v QCD BG neglected BG rescaled to CMS-HIG ΤΜ invariant mass m ΤΜ GeV ΤΜ invariant mass m ΤΜ GeV For Y µτ, Y τµ close to the current upper limits, spectacular signals possible. Joachim Kopp Flavor Violating Higgs Decays 20

27 Exploiting Higgs production in gluon-gluon fusion Observations Computed p T,ν (using collinear approximation) is /E T Muon in h τµ is much harder than in h τ l τ l. Davidson Verdier, arxiv: Events / Z l l + jets tt WW,WZ,ZZ single t SM Higgs 10 Signal Events / 2 GeV Z l l + jets tt WW,WZ,ZZ single t SM Higgs Signal δe T Muon p (GeV) T Joachim Kopp Flavor Violating Higgs Decays 21

28 Exploiting Higgs production in gluon-gluon fusion Observations Computed p T,ν (using collinear approximation) is /E T Muon in h τµ is much harder than in h τ l τ l. Davidson Verdier, arxiv: Muon p (GeV) T Background 1 Muon p (GeV) T Signal δe T δe T Joachim Kopp Flavor Violating Higgs Decays 21

29 Exploiting Higgs production in gluon-gluon fusion Observations Computed p T,ν (using collinear approximation) is /E T Muon in h τµ is much harder than in h τ l τ l. Davidson Verdier, arxiv: Muon p (GeV) T Background 1 Muon p (GeV) T Signal δe T δe T Projected sensitivity Davidson Verdier, arxiv: BR(h τµ), BR(h τe) < Joachim Kopp Flavor Violating Higgs Decays 21

30 Summary Flavor-violating Higgs couplings arise in Models with several sources of electroweak symmetry breaking Models with heavy fields coupled to the Higgs In the lepton sector: Constraints from l1 l 2 + γ, l 1 l 2 + X, µ e conversion in nuclei, g 2, EDMs, M M oscillations Strong constraints in the µ e sector Very weak constraints in the τ e and τ µ sectors In the quark sector: Strong constraints on couplings to light quarks Very weak constraints on couplings to top quarks At the LHC Constraints on anomalous top Higgs couplings from single top production A recast ATLAS h τl τ l search already provides strongest limits on h τµ and h τe A dedicated search would be much more sensitive Joachim Kopp Flavor Violating Higgs Decays 22

31 Thank you!