Flavor and CP Violation in Higgs Decays - · PDF fileFlavor and CP Violation in Higgs Decays...

Flavor and CP Violation in Higgs Decays

Joachim Kopp

University of Mainz / PRISMA Cluster of Excellence

ERC Workshop Schloss Waldthausen,

November 10, 2014

Based on work done in collaboration withAdmir Greljo, Roni Harnik, Jernej Kamenik, Marco Nardecchia and Jure Zupan

Joachim Kopp Flavor and CP Violation in Higgs Decays 1

Outline

1 Flavor Mixing in the Higgs Sector

2 FCNC Higgs Couplings to Leptons

3 FCNC Higgs Couplings to quarks

4 CP Violation in FCNC Higgs Decays

5 Summary


Flavor Mixingin the Higgs Sector

Motivation

Scenario 1: Several sources of EW symmetry breakingIf fermion masses have more than one origin, they do not need to bealigned with the Yukawa couplings

Simplest example: Type III 2-Higgs-Doublet Model

LY ⊃ −Y (1)ij Liej

RH(1) − Y (2)ij Liej

RH(2) + h.c.

−→ −mi eiLei

R − Y effij ei

LejRh + couplings to heavier Higgs bosons + h.c.

(h = Lightest neutral Higgs boson, mh ∼ 125 GeV)

Assume heavy Higgs bosons are decoupled.see for instance Davidson Greiner, arXiv:1001.0434

Similar couplings for quarks


http://arxiv.org/abs/1001.0434

Motivation (2)

Scenario 2: Extra Higgs couplingsAssume existence of heavy new particles, which induce effective operatorsof the form

∆LY = −λ′ijΛ2 (ei

LejR)H(H†H) + h.c.+ · · · ,

→ after EWSB, new (but misaligned) contributions to mass matrices andYukawa couplings

Effective Lagrangian is again

LY ⊃ −mi eiLei

R − Y effij ei

LejRh + h.c.

see for instance Giudice Lebedev, arXiv:0804.1753



Effective Yukawa Lagrangfian

Effective Yukawa Lagrangian

LY = −mi f iLf i

R − Y aij (f i

Lf jR)ha + h.c.+ · · ·

Previously studied by many authors:

Bjorken Weinberg, PRL 38 (1977) 622 McWilliams Li, Nucl. Phys. B 179 (1981) 62Shanker, Nucl. Phys. B 206 (1982) 253 Barr Zee, PRL 65 (1990) 21Babu Nandi, hep-ph/9907213 Diaz-Cruz Toscano, hep-ph/9910233Han Marfatia, hep-ph/0008141 Arganda Curiel Herrero Temes, hep-ph/0407302Kanemura Ota Tsumura, hep-ph/0505191 Giudice Lebedev, 0804.1753Casagrande Goertz Haisch Neubert Pfoh, 0807.4937Blanke Buras Duling Gori Weiler, 0809.1073 Albrecht Blanke Buras Duling Gemmler, 0903.2415Aguilar-Saavedra, 0904.2387 Buras Duling Gori, 0905.2318Agashe Contino, 0906.1542 Azatov Toharia Zhu, 0906.1990Davidson Greiner, 1001.0434 Goudelis Lebedev Park, 1111.1715Blankenburg Ellis Isidori, 1202.5704 Wang Huang Li Li Shao Wang, 1208.2902McKeen Pospelov Ritz, 1208.4597 Arhrib Cheng Kong, 1208.4669. . .


















LY = −mi f iLf i

R − Y aij (f i

Lf jR)ha + h.c.+ · · ·

More recent studies:

Arhrib Cheng Kong, 1210.8241 Dery Efrati Hochberg Nir, 1302.3229Atwood Gupta Soni, 1305.2427 Zhang Maltoni, 1305.7386Arroyo Diaz-Cruz Diaz Orduz-Ducuara, 1306.2343 Celis Cirigliano Passemar, 1309.3564Khatibi Najafabadi, 1402.3073 Cao Han Wu Yang Zhang, 1404.1241Gorban Haisch, 1404.4873 Crivellin Hoferichter Procura, 1404.7134Arganda Herrero Marcano Weiland, 1405.4300 Bressler Dery Efrati, 1405.4545. . .
















LY = −mi f iLf i

R − Y aij (f i

Lf jR)ha + h.c.+ · · ·

New in this talk:Up-to-date low-energy constraints on FV decaysLHC limits on h→ µτ , h→ eτ , t → ch, t → uhStrategies for future LHC searchesPossibility of Flavor + CP violation


FCNC Higgs Couplingsto Leptons

Low-energy constraints on LFV in the Higgs sector

h

µ+

e−

e+

µ−

Y ∗eµPL + YµePR

Y ∗eµPL + YµePR

M–M oscillations

h

N

µ

N

eY ∗µePL + YeµPR

µ–e conversion

τ

h

τµ

γ

µY ∗µτPL + YτµPR Y ∗

τµPL + YµτPR

g − 2, EDMs

γτ

µ

µ

µ

Y ∗µµPL + YµµPR

= τ → µγ diagrams

τ → 3µ, µ→ 3e, etc.

τ

h

ττ

γ

µY ∗ττPL + YττPR Y ∗

τµPL + YµτPR

µ

h γ, Z

tt

τ

γ

µ

µ

h γ, Z

WW

τ

γ

µµ

h γ, Z

W W

τ

γ

µ

τ → µγ, µ→ eγ, etc.


Constraints on h→ µe

10-8 10-7 10-6 10-5 10-410-8

10-7

10-6

10-5

10-4

Yukawa coupling ÈYeΜÈ

Yukaw

aco

upli

ng

ÈY ΜeÈΜ ® eΓ

Μ ® 3e HapproxLΜ ® e conv.

Mu2e HprojectionL

BRHh®

ΜeL

=10

-5

10

-12

10

-11

10

-10

10

-9

10

-8

10

-7

10

-6

Harnik JK Zupan, arXiv:1209.1397see also Blankenburg Ellis Isidori, arXiv:1202.5704

Goudelis Lebedev Park, arXiv:1111.1715


Assumption here:Diagonal Yukawa couplings unchangedfrom their SM values.




Constraints on h→ τµ and h→ τe

10-3 10- 2 10-1 100

10-3

10- 2

10-1

100

ÈYΜΤ È

ÈY ΤΜÈ

Τ®

ΜΓ

Τ ® 3Μ Happrox .LHg-2L Μ

+ED

MΜ

Hg-2L Μ�

ImHY ΤΜ

Y ΜΤL=0

ÈYΤΜ Y

ΜΤ È=mΜ m

Τ �v 2

BRHh

®ΤΜL

=0.99

10-

3

10-

2

10-

1

0.50.75

10- 5 10- 4 10-3 10- 2 10-1 10010- 5

10- 4

10-3

10- 2

10-1

100

ÈYeΤ ÈÈY ΤeÈ

Τ®

eΓΤ ® 3e Happrox .L

Hg-2Le +ED

Me

Hg-2Le for ImHY

Τe YeΤ L=0ÈY

Τe YeΤ È=m

e mΤ �v 2

BRHh

®ΤeL

=0.99

10-

6

10-

5

10-

3

10-

2

10-

1

0.5

EDM

e �ReHY

Τe YeΤ L=0

Substantial flavor violation (BR(h→ τµ, τe) ∼ 0.01) perfectly viable.Harnik JK Zupan, arXiv:1209.1397

see also: Blankenburg Ellis Isidori, arXiv:1202.5704Goudelis Lebedev Park, arXiv:1111.1715

Davidson Greiner, arXiv:1001.0434


Assumption here:Diagonal Yukawa couplings unchangedfrom their SM values.





h→ τµ and h→ τe at the LHC

Basic idea:

h→ τ` has the same final stateas h→ ττ`(but is enhanced by 1/BR(τ → `))

Recast h→ ττ searchhere: ATLAS, arXiv:1206.5971

Consider only 2-leptonfinal statesUse VBF cuts(much lower BG than gg fusion)

see howeverDavidson Verdier, arXiv:1211.1248




h→ τµ and h→ τe at the LHC

Basic idea:

h→ τ` has the same final stateas h→ ττ`(but is enhanced by 1/BR(τ → `))

Recast h→ ττ searchhere: ATLAS, arXiv:1206.5971

Consider only 2-leptonfinal statesUse VBF cuts(much lower BG than gg fusion)

see howeverDavidson Verdier, arXiv:1211.1248

Harnik JK Zupan, arXiv:1209.1397based on ATLAS, arXiv:1206.5971

æ

æ

æ æ æ

æ æ

0 100 200 300 4000

5

10

15

20

25

ΤΤ collinear mass mΤΤ @GeV DE

ven

ts�1

0G

eV

ATLAS 4.7 fb-1

ATLAS MCææ ATLAS data

5 ´ H ® Τ{

Τ{

5 ´ H ® Τ{

Μ

H ÈY ΜΤ2

+ÈY ΤΜ2 L 1 � 2

=m Τ

v






LHC constraints on h→ τµ and h→ τe

10-3 10- 2 10-1 100

10-3

10- 2

10-1

100

ÈYΜΤ È

ÈY ΤΜÈ

Τ®

ΜΓ


+ED

MΜ

Hg-2L Μ�

ImHY ΤΜ

Y ΜΤL=0

ÈYΤΜ Y

ΜΤ È=mΜ m

Τ �v 2

BRHh

®ΤΜL

=0.99

10-

3

10-

2

10-

1

0.50.75

10- 5 10- 4 10-3 10- 2 10-1 10010- 5

10- 4

10-3

10- 2

10-1

100

ÈYeΤ ÈÈY ΤeÈ

Τ®

eΓ

Τ ® 3e Happrox .LHg-2Le +

EDM

e

Hg-2Le for ImHY

Τe YeΤ L=0ÈY

Τe YeΤ È=m

e mΤ �v 2

BRHh

®ΤeL

=0.99

10-

6

10-

5

10-

3

10-

2

10-

1

0.5

EDM

e �ReHY

Τe YeΤ L=0

Harnik JK Zupan, arXiv:1209.1397



LHC constraints on h→ τµ and h→ τe

10-3 10- 2 10-1 100

10-3

10- 2

10-1

100

ÈYΜΤ È

ÈY ΤΜÈ

Τ®

ΜΓ


+ED

MΜ

Hg-2L Μ�

ImHY ΤΜ

Y ΜΤL=0

ÈYΤΜ Y

ΜΤ È=mΜ m

Τ �v 2

Our LHC limitHATLAS 7 TeV , 4.7 fb-1L BRHh

®ΤΜL

=0.99

10-

3

10-

2

10-

1

0.50.75

10- 5 10- 4 10-3 10- 2 10-1 10010- 5

10- 4

10-3

10- 2

10-1

100

ÈYeΤ ÈÈY ΤeÈ

Τ®

eΓ

Τ ® 3e Happrox .LHg-2Le +

EDM

e

Hg-2Le for ImHY

Τe YeΤ L=0ÈY

Τe YeΤ È=m

e mΤ �v 2

Our LHC limitHATLAS 7 TeV , 4.7 fb-1L

BRHh

®ΤeL

=0.99

10-

6

10-

5

10-

3

10-

2

10-

1

0.5

EDM

e �ReHY

Τe YeΤ L=0

Harnik JK Zupan, arXiv:1209.1397



Strategy for a dedicated h→ τµ and h→ τe search

Possible improvementsDifferent invariant mass formula

I Avoids smearing of signalI Shifts Z → ττ peak to

lower invariant mass

Include hadronic τ ’sOptimized cuts

I Use higher lepton pT in h→ µτcompared to h→ ττ

I Use ∆φ and MT cutsI Allows inclusion of gg fusion

events

Harnik JK Zupan, arXiv:1209.1397Davidson Verdier, arXiv:arXiv:1211.1248

| τµ

|Y-410 -310 -210 -110 1

|

µτ|Y

-410

-310

-210

-110

1 = 8 TeVs, -119.7 fbCMS preliminary

BR

<0.1%

BR

<1%

BR

<10%

BR

<50%

ττ→LHC h

observed

expectedτµ→h

µ 3→τ

γ µ →τ

2/vτmµ

|=mµτ

Yτµ|Y

CMS-PAS-HIG-14-005




http://cds.cern.ch/record/1740976?ln=en

FCNC Couplings to Quarks

Constraints on Higgs couplings to light quarksTight constraints from neutral meson oscillations

h

d

b

b

dY ∗bdPL + YdbPR

Y ∗bdPL + YdbPR

t

h

h

t

u

c

c

uY ∗ctPL + YtcPR

Y ∗tuPL + YutPR Y ∗

ctPL + YtcPR

Y ∗tuPL + YutPR

Work in Effective Field Theory:

Heff = Cdb2 (bRdL)2 + Cdb

2 (bLdR)2 + Cdb4 (bLdR)(bRdL) + . . .

Wilson coefficients constrained by UTfit (Bona et al.), arXiv:0707.0636see also Blankenburg Ellis Isidori, arXiv:1202.5704




Constraints on Higgs couplings to light quarksTight constraints from neutral meson oscillationsWork in Effective Field Theory:

Heff = Cdb2 (bRdL)2 + Cdb

2 (bLdR)2 + Cdb4 (bLdR)(bRdL) + . . .

Wilson coefficients constrained by UTfit (Bona et al.), arXiv:0707.0636see also Blankenburg Ellis Isidori, arXiv:1202.5704

Technique Coupling Constraint

D0 oscillations |Yuc |2, |Ycu|2 < 5.0× 10−9

|YucYcu| < 7.5× 10−10

B0d oscillations |Ydb|2, |Ybd |2 < 2.3× 10−8

|YdbYbd | < 3.3× 10−9

B0s oscillations |Ysb|2, |Ybs|2 < 1.8× 10−6

|YsbYbs| < 2.5× 10−7

K 0 oscillations

<(Y 2ds), <(Y 2

sd ) [−5.9 . . . 5.6]× 10−10

=(Y 2ds), =(Y 2

sd ) [−2.9 . . . 1.6]× 10−12

<(Y ∗dsYsd ) [−5.6 . . . 5.6]× 10−11

=(Y ∗dsYsd ) [−1.4 . . . 2.8]× 10−13




But:

Indirect constraints very weak

for FCNC top couplings

⇒ Discovery potential at the LHC

Multileptons and diphotons from FCNC t–h couplings

u, c h

b

W

h

u, c

W

b

t t

t

g g

g

single top + Higgs production

Only relevant for tuh couplings(PDF suppression for charm)

`+ 2γ or up to 5`not included in LHC searches

t → hq decay

Relevant for tuh and tch couplings(no PDF suppression)

`+ 2γ or up to 5`


Combined CMS diphoton + multilepton results

BR(t → cH) < 0.0056 ↔√|ytc |2 + |yct |2 < 0.14

multileptons: CMS arXiv:1404.5801; CMS-SUS-13-002diphotons: CMS-PAS-HIG-13-034, recasting CMS-PAS-HIG-13-025

see also ATLAS t + (h→ γγ) analysis with tailored cuts, slightly worse limitdue to unlucky statistical fluctuations

ATLAS arXiv:1403.6293



https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsSUS13002

https://twiki.cern.ch/twiki/bin/view/CMSPublic/Hig13034TWiki



Future directionsSome ideas for future improvements

Include tuh couplings→ leads to factor 1.5 improvementOptimize cutsOther final states→ this talkηh as discriminator between tuh and tch couplings→ this talk

Greljo Kamenik JK, arXiv:1404.1278



The fully hadronic final stateAnalysis 1: pp → t(t → hj)→ hadrons

I Tagging SM t → Wb decays: HEPTopTaggerPlehn Salam Spannowsky Takeuchi Zerwas, arXiv:0910.5472, 1006.2833

I Tagging FCNC t → hq decays: Modified HEPTopTaggerwith adapted kinematic cuts

I Require b tags in likely b subjets

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40.0

0.2

0.4

0.6

0.8

1.0

arctanHm13 � m12 L

m2

3�m

12

3

m23 > mh

m13 > mhm12 > mh

t t ® hhjj ® bb bb jj

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40.0

0.2

0.4

0.6

0.8

1.0


m2

3�m

12

3

m23 > mh

m13 > mhm12 > mh

t t ® W + W - bb ® 4 j+ bb

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40.0

0.2

0.4

0.6

0.8

1.0


m2

3�m

12

3

m23 > mh

m13 > mhm12 > mh

QCD multijet

Analysis 2: pp → th→ hadrons (single top + Higgs productions)I Tagging SM t → Wb decays: HEPTopTagger

Plehn Salam Spannowsky Takeuchi Zerwas, arXiv:0910.5472, 1006.2833I Higgs tagging: Mass drop tagger

Butterworth Davison Rubin Salam 0802.2470; Cacciari Salam Soyez 1111.6097I Require b tags in likely b subjetsI Cuts on mH (reconstructed Higgs mass) and |ηh| (reconstructed Higgs rapidity)

60 80 100 120 140 160 180 20010- 2

10-1

10 0

101

10 2

10 3

Reconstructed m H @GeV D

Cro

ssse

ctio

npe

rbi

n@

fbD

-3 -2 -1 0 1 2 310- 2

10-1

10 0

101

10 2

10 3

Higgs pseudorapidity Η h

Cro

ssse

ctio

npe

rbi

n@

fbD sing le t

tt

QCD

t+ H

t H t® HjL










The fully hadronic final stateAnalysis 1: pp → t(t → hj)→ hadronsAnalysis 2: pp → th→ hadrons (single top + Higgs productions)


I Higgs tagging: Mass drop taggerButterworth Davison Rubin Salam 0802.2470; Cacciari Salam Soyez 1111.6097

I Require b tags in likely b subjetsI Cuts on mH (reconstructed Higgs mass) and |ηh| (reconstructed Higgs rapidity)

60 80 100 120 140 160 180 20010- 2

10-1

10 0

101

10 2

10 3


Cro

ssse

ctio

npe

rbi

n@

fbD

-3 -2 -1 0 1 2 310- 2

10-1

10 0

101

10 2

10 3


Cro

ssse

ctio

npe

rbi

n@

fbD sing le t

tt

QCD

t+ H

t H t® HjL








Comparison of current and projected future limits√

y2ut + y2

tu BR(t → hu)√

y2ct + y2

tc BR(t → hc)

New limits from existing dataMultilepton < 0.19 < 0.010 < 0.23 < 0.015Diphoton plus lepton < 0.12 < 0.0045 < 0.15 < 0.0066Vector boson plus Higgs < 0.16 < 0.0070 < 0.21 < 0.012

Projected future limits (13 TeV, 100 fb−1)Vector boson plus Higgs < 0.076 < 0.0015 < 0.084 < 0.0019Multilepton < 0.087 < 0.0022 < 0.11 < 0.0033Fully hadronic < 0.12 < 0.0036 < 0.13 < 0.0048




Discriminating between tuh and tch couplingsIn ug → th, interaction products tend to be boostedin the direction of the u quark.(Valence quarks carry larger fraction of proton momentum.)

Moreover: In center of mass frame, Higgs boson is emitted preferentiallyin the direction of the up quark(angular momentum conservation + chirality flip in tuh Yukawa vertex.)

Result (parton level):

13TeV, 1fb-1; ytq=yqt=0.13

ug®thpp®tt, t®hc

ug®thcg®th

-4 -2 0 2 40

200

400

600

800

1000

Ηh

Eve

nts


Khatibi Najafabadi, arXiv:1402.3073Greljo Kamenik JK, arXiv:1404.1278



Discriminating between tuh and tch couplingsIn ug → th, interaction products tend to be boostedin the direction of the u quark.(Valence quarks carry larger fraction of proton momentum.)

Moreover: In center of mass frame, Higgs boson is emitted preferentiallyin the direction of the up quark(angular momentum conservation + chirality flip in tuh Yukawa vertex.)

Parton level vs. analysis level:

Ηh,13TeV, 1fb-1; ytq=yqt=0.13 Η{{h, Η{{

-4 -2 0 2 40

1

2

3

4

5

6

Η

Eve

nts

pp ® th ® b3{3Ν


Khatibi Najafabadi, arXiv:1402.3073Greljo Kamenik JK, arXiv:1404.1278



Discriminating between tuh and tch couplings (2)Conclusion: Rapidity η`` of dilepton system from h→WW ∗ → ``νν is agood discriminator between tuh and tch couplings.

Moreover: Final state lepton charges as an additional discriminant.

Result for multilepton search:

BHt®chL: blue

BHt®uhL: red

Solid, thick: 95% CL limitsDotted, thick: 5Σ discoveryDashed, thin: 2Σ prefered

10 20 50 100 200 500 1000 2000

0.05

0.10

0.20

0.50

1.00

2.00

Luminosity @fb-1D

BHt

®qh

L@%

D

For a 5σ discovery, discrimination between tuh and tch is possible at 2σ.




CP Violation in FCNC Higgs Decays

CP violation in FCNC Higgs decays

h1

ℓ−

ℓ′+

ℓm

hk

ℓn

h1

ℓ−

ℓ′+ℓm

ℓn

hk

h1

ℓ−

ℓ′+

(a) (b) (c)

Basic idea:

Interference of tree and loop diagrams leads to CP violationWeak phase from non-standard Yukawa couplingsStrong phase from loop function(since m` < mh/2)

JK Nardecchia, arXiv:1406.5303



Example: A Two Higgs-Doublet Model

L ⊃ −√

2mi

vδij Li

L`jRΦ1 −

√2Yij Li

L`jRΦ2 + h.c. ,

In the physical basis:

L = −mi ¯iL`

iR −

∑r=1,2,3

Y hrij

¯iL`

jR hr + h.c. (r = 1,2,3)

with

Y hrij =

miδij

vO1r + YijO2r + iYijO3r ,

O = SO(3) (real 3× 3) rotation matrix




Example: A Two Higgs-Doublet Model

L ⊃ −√

2mi

vδij Li

L`jRΦ1 −

√2Yij Li

L`jRΦ2 + h.c. ,

Result:

AµτCP =∑α=2,3

14π|Yτµ|2 − |Yµτ |2

|Yτµ|2 + |Yµτ |2(|Yµτ |2 + |Yτµ|2 + |Yττ |2

)

× Rα ×[g(

m2h

m2hα

)+

m2h

m2h −m2

hα

]with

Rα =(O3αO21 −O2αO31) (O2αO21 + O3αO31)

O221 + O2

31

. . . suppressed only by loop factorJK Nardecchia, arXiv:1406.5303



Sensitivity to CPV in FCNC Higgs decays @ HL-LHC

0. 0.002 0.004 0.006 0.008 0.0110-1

100

101

Higgs mixing angle Θ12 =Θ13

Yuk

awa

coup

lin

gY

ΤΜ

Θ12 =Θ13

m h2 =190 GeVm h3 =200 GeV

BRHh1 ®ΜΤL limit

ÈBRH h®ΜΤL ACP È=10-1

10- 2

10- 3

10- 4

10- 5

10- 7

Sensitivity to CPVH ±1Σ ,2 ΣL � 300 fb -1

Best discovery potential in small Higgs mixing regimeCP violation visible only at high-luminosity LHCWould require a detection of h→ τµ or h→ τe very soon.




Summary

SummaryFlavor-violating Higgs couplings arise in

I Models with several sources of electroweak symmetry breakingI Models with heavy fields coupled to the Higgs

In the lepton sector:I In the µ–e sector: strong constraints from LFV searchesI In the τ–e and τ–µ sectors: strongest constraints from the LHCI If h→ τµ or h→ τe is discovered soon:

Possibility to look for CP violation in the future.

In the quark sector:I Light quarks: strong constraints from meson mixingI Top quark: Limits on t → ch from multileptons, diphotonsI Future improvements:

F Include anomalous single-t production for tuh couplingsF Optimized cutsF Other final states (fully hadronic is feasible with jet substructure techniques)F Use Higgs rapidity ηh and lepton charges as a discriminator between

tuh and tch couplings


Thank you!

CMS event selection for multilepton analysisAt least 3 leptons(electrons, muons, hadronic tau candidates (“τh”)

Standard pT and η cutsI pe,µ

T > 10 GeV, |ηe,µ| < 2.4I pτh

T > 20 GeV, |ητh | < 2.3I at least one e or µ must be above 20 GeV

Isolation criteriaLepton tracks required to start close to the primary vertexJets are reconstructed with the anti-kT algorithm; must havepT > 30 GeV, |η| < 2.5Combined secondary vertex algorithm for b-tagging

CMS arXiv:1404.5801; CMS-SUS-13-002




CMS event classification for multilepton analysisEvents are sorted in non-overlapping categories according to

Number of leptons (3 or ≥ 4)/ET

Number of τh candidatesNumber of b-tagged jetsNumber of OSSF (“opposite sign, same flavor”) lepton pairsOSSF pairs on/off the Z -resonance

→ A very versatile search that is sensitive to many types of new physics





Backgrounds for CMS multilepton analysisZ + jets(two leptons from Z decay, one lepton from misidentified jet or heavy flavor decay)

SM WZ or ZZ productiont t production(two leptons from W decay, one lepton from semileptonic b decay)

Internal conversion of photonsRare processes(triple boson production, t t + V production)

Relative importance of backgrounds varies significantlybetween event categories.

So do systematic uncertainties.





Results: 3-lepton categories

∗ = channels used for normalization, excluded from new physics searchesJoachim Kopp Flavor and CP Violation in Higgs Decays 34

Results: 4-lepton categories


The most sensitive channels in the t → cH search

(GeV)missTE

0-50 50-100 100-150 150-200 >200

Eve

nts/

Bin

1

10

210

310 ObservedBkg Uncertainties

Data-driven

ttWZZZ

WttZtt

CMS Preliminary -1 = 19.5 fbt dL∫ = 8 TeV, s

T3 leptons: OSSF1, low-Z, no taus, at least 1 b-jet, low H

(GeV)missTE

0-50 50-100 100-150 150-200 >200

Eve

nts/

Bin

-110

1

10

210

310ObservedBkg Uncertainties

Data-driven

ttWZZZ

WttZtt


T3 leptons: OSSF0, no taus, at least 1 b-jet, low H

(GeV)missTE

0-50 50-100 100-150 150-200 >200

Eve

nts/

Bin

1

10

210Observed

Bkg Uncertainties

Data-driven

tt

WZ

ZZ

Wtt

Ztt


T3 leptons: OSSF1, low-Z, no taus, at least 1 b-jet, high H

u, c h

b

W

h

u, c

W

b

t t

t

g g

g

Relevant are mostly the two lowest /ET bins.CMS arXiv:1404.5801; CMS-SUS-13-002




t → cH: CMS Constraints20 References

Higgs Decay Mode obs exp 1σ rangeh → WW∗ (BR = 23.1 %) 1.58 % 1.57 % (1.02–2.22) %h → ττ (BR = 6.15 %) 7.01 % 4.99 % (3.53–7.74) %h → ZZ∗ (BR = 2.89 %) 5.31 % 4.11 % (2.85–6.45) %

combined 1.28 % 1.17 % (0.85–1.73) %

Table 7: Comparison of the observed and median expected 95% C.L. limits on BR(t → ch) fromindividual Higgs decay modes along with the 1σ uncertainty ranges.

8 ConclusionWe have performed a search for physics beyond the SM using a variety of multilepton finalstates. We see good agreement between observations and expectations in channels with largeSM expectations both on-Z and off-Z.

We used SUSY scenarios as benchmarks for new physics with multiple leptons. We were ableto probe new regions of the natural Higgsino NLSP, slepton co-NLSP, stau-(N)NLSP, T1tttt,and T6ttWW scenarios. In the absence of any indication of new physics we place limits onsupersymmetric mass spectra.

These models span a range of parameters, and the limits on intermediate and final state massesillustrate the reach of this analysis for most new physics scenarios with multiple leptons inthe final state. Although we have chosen specific SUSY models to interpret our results, themasses and couplings from many other SUSY or non-supersymmetric new physics modelscan be translated into the framework of the models discussed here, and the limits applied tothose models. The sensitivity of the analysis was further demonstrated by placing a limit onBR(t → ch).

References[1] New Physics Working Group Collaboration, “New Physics at the LHC. A Les Houches

Report: Physics at TeV Colliders 2009 - New Physics Working Group”,arXiv:1005.1229.

[2] H. P. Nilles, “Supersymmetry, Supergravity and Particle Physics”, Phys. Rept. 110 (1984)1, doi:10.1016/0370-1573(84)90008-5.

[3] H. E. Haber and G. L. Kane, “The Search for Supersymmetry: Probing Physics Beyond theStandard Model”, Phys. Rept. 117 (1985) 75, doi:10.1016/0370-1573(85)90051-1.

[4] W. de Boer, “Grand unified theories and supersymmetry in particle physics andcosmology”, Prog. Part. Nucl. Phys. 33 (1994) 201,doi:10.1016/0146-6410(94)90045-0.

[5] LHC New Physics Working Group Collaboration, “Simplified Models for LHC NewPhysics Searches”, J.Phys. G39 (2012) 105005,doi:10.1088/0954-3899/39/10/105005, arXiv:1105.2838.

[6] J. K. R. Essig, E. Izaguirre et al., “Heavy Flavor Simplified Models at the LHC”, JHEP074 (2012) 1201, doi:10.1007/JHEPD01(2012)074.

BR(t → cH) < 0.013

√|ytc |2 + |yct |2 < 0.21





Diphoton + lepton — Backgrounds

γγM0 50 100 150 200

Eve

nts

0

10

20

30

40

50

60

70

80

,MET 0-30GeVγ+2τFit from upto 2

,MET 30-50GeVγFit 1lep+2

CMS Preliminary -1 = 19.5 fbint = 8 TeV Ls

Background from sideband fit at mγγ < 120 GeV and mγγ > 130 GeV.

CMS-PAS-HIG-13-034, recasting CMS-PAS-HIG-13-025




t → cH search in the diphoton + lepton channelRequirements:

One isolated lepton (pT > 10 GeV, |η| < 2.4)Two photons (pT1 > 40 GeV, pT 1 > 20 GeV, |η| < 2.5)120 GeV < mγγ < 130 GeV

Events are classified according to/ET

b-tagged jetsτh candidates





Diphoton + lepton — Results

Most sensitive channel has one b-jet, medium /ET , no τh.





ATLAS t + (h→ γγ) analysisIncludes diphoton + lepton and diphoton + jets final statesRequires b-jetsImposes criteria on invariant masses mγγj , m`ν j , mjjj

Uses mγγ as discrimination variable

[GeV]γγm100 110 120 130 140 150 160

Eve

nts/

4 G

eV

0

2

4

6

8

10

12

14

16 ATLAS

s = 8 TeV√, -1

L dt = 20.3 fb∫s = 7 TeV√,

-1L dt = 4.7 fb∫

Hadronic Selection

Data 2011+2012Sig.+SM Higgs+continuum bkg. fit

= 125.5 GeV)H

(mSM Higgs+continuum bkg.Continuum bkg.

qH → tB0 0.002 0.004 0.006 0.008 0.01 0.012 0.014

sC

L

-210

-110

1ATLAS

s = 8 TeV√, -1

L dt = 20.3 fb∫s = 7 TeV√,

-1L dt = 4.7 fb∫

ObservedExpected

σ 1 ±σ 2 ±

BR(t → cH) < 0.0079 ↔√|ytc |2 + |yct |2 < 0.17

(slightly worse than CMS combined limit BR(t → cH) < 0.0056,√|ytc |2 + |yct |2 < 0.14)




Diphoton analysis from ATLASDiphoton + lepton analysis: cuts similar to CMS, but in addition:

I Require mT ,`ν > 30 GeVI Consider two leading jets (2nd jet replaced by 3rd/4th if 3rd/4th is b-tagged)I Require one b-jetI Define m1 = mγγj and m2 = m`ν j such that either m1 or m2 (or both)

are close to mt

[GeV] jγγ m0 50 100 150 200 250 300 350 400 450 500

Ent

ries/

10 G

eV

0

2

4

6

8

10

12

14

16

18

20ATLAS

-1 L dt = 20.3 fb∫ = 8 TeV, s

Leptonic Selection No b-tag

(a)

Data

), normalised to luminosityγ & W(tt

))γ & W(t l, norm. to data- (t→j γγSHERPA

Signal, B = 5%

[GeV] jνl m0 50 100 150 200 250 300 350 400 450 500

Ent

ries/

10 G

eV

0

1

2

3

4

5

6

7

8

9

10ATLAS

-1 L dt = 20.3 fb∫ = 8 TeV, s

Leptonic Selection No b-tag

< 191 GeV jγγ156 < m

(b)

Data

), normalised to luminosityγ & W(tt

))γ & W(t l, norm. to data- (t→j γγSHERPA

Signal, B = 5%




Diphoton analysis from ATLASDiphoton + lepton analysis: cuts similar to CMS, but in addition:Diphoton + jets analysis

I Require two photons as beforeI In addition, four jets, at least one b-jetI Define m1 = mγγj and m2 = mjjj such that either m1 or m2 (or both)

are close to mt

[GeV] jγγ m0 50 100 150 200 250 300 350 400 450 500

Ent

ries/

10 G

eV

0

10

20

30

40

50

60

70

80

90

100ATLAS

-1 L dt = 20.3 fb∫ = 8 TeV, s

Hadronic Selection

(a)

Data

j, norm. to data γγSHERPA

Signal, B = 5%

[GeV] jjj m0 50 100 150 200 250 300 350 400 450 500

Ent

ries/

10 G

eV

0

2

4

6

8

10

12

14

16

18

20

22ATLAS

-1 L dt = 20.3 fb∫ = 8 TeV, s

Hadronic Selection < 191 GeV jγγ 156 < m

(b)

Data

j, norm. to dataγγSHERPA

Signal, B = 5%




Couplings involving top quarks (anno 2012)

10- 2 10-1 100 10110- 2

10-1

100

101

ÈYqt È Hq = c, uL

ÈY tqÈHq=

c,u

L

0.5

10-1

10- 2

10- 3

10- 4

10-5

0.5

10-1

10- 2

10- 3

10- 4

BRHh® t * q LBRHt ® hq L

single

top

bo

un

do

nÈYct È,ÈY

tc Èsin

gleto

pb

ou

nd

onÈY

ut È,ÈY

tu È

t®h

qlim

itHCraig

etal.L

Constraints from

Single top production

t

h

tt

g

qY ∗ttPL + YttPR Y ∗

tqPL + YqtPR

CDF 0812.3400, DØ 1006.3575ATLAS 1203.0529

t → hqCraig et al. 1207.6794

based on CMS multilepton search1204.5341

Not sensitive

t → ZqCMS 1208.0957








Limits on tuh couplingsRecast the CMS multilepton search including also gq → th:

u, c h

b

W

h

u, c

W

b

t t

t

g g

g


Greljo Kamenik JK, 1404.1278see also Atwood Gupta Soni, 1305.2427

Khatibi Najafabadi, 1402.3073





u, c h

b

W

h

u, c

W

b

t t

t

g g

g

Result (multileptons)

OSSF pair Nb-jets HT (GeV) EmissT (GeV) N(t → hj) N(th) Nobs Nexp

1. below Z ≥ 1 ≤ 200 50− 100 10.8 6.7 48 48± 232. no OSSF ≥ 1 ≤ 200 50− 100 4.4 3.0 29 26± 133. below Z ≥ 1 ≤ 200 ≤ 50 6.8 3.8 34 42± 114. no OSSF ≥ 1 ≤ 200 ≤ 50 4.2 2.5 29 23± 105. below Z ≥ 1 > 200 50− 100 2.5 0.6 10 9.9± 3.76. below Z ≥ 1 > 200 ≤ 50 2.0 0.4 5 10± 2.57. below Z 0 ≤ 200 50− 100 9.2 5.1 142 125± 278. no OSSF 0 ≤ 200 50− 100 4.0 2.5 35 38± 159. above Z ≥ 1 ≤ 200 ≤ 50 1.9 1.2 17 18± 6.7

(signal predictions are for BR(t → hu) = 0.01)

Most sensitive channels have3 leptons, low HT , one b-jet








u, c h

b

W

h

u, c

W

b

t t

t

g g

g

Result (multileptons): Limit on Yukawa couplings y2tu + y2

utis a factor of 1.5 stronger than limit on y2

tc + y2ct

Specifically:

BR(t → hc) < 0.015BR(t → hu) < 0.010

Limit on BR(t → hu) is a factor 1.5 better than limit on BR(t → hc).

(Our limits are slightly worse than CMS limits because τh channels are omitted.)








u, c h

b

W

h

u, c

W

b

t t

t

g g

g



tc + y2ct

Result (diphoton+lepton)Nb-jets Emiss

T (GeV) N(t → hj) N(th) Nobs Nexp1. ≥ 1 50− 100 3.2 1.3 1 2.3± 1.22. ≥ 1 30− 50 2.2 0.92 2 1.1± 0.63. ≥ 1 ≤ 30 1.9 0.83 2 2.1± 1.14. 0 50− 100 2.4 1.1 7 9.5± 4.45. ≥ 1 > 100 0.82 0.49 0 0.5± 0.46. 0 > 100 0.87 0.52 1 2.2± 1.07. 0 30− 50 1.6 0.64 29 21± 10








u, c h

b

W

h

u, c

W

b

t t

t

g g

g



tc + y2ct

Result (diphoton+lepton): Limit on Yukawa couplings y2tu + y2


tc + y2ct

Specifically:

BR(t → hc) < 0.0066BR(t → hu) < 0.0045







Optimized cutsExample: recast CMS search for V + H production

CMS-PAS-HIG-12-053Greljo Kamenik JK, 1404.1278

Cuts:Exactly two same-sign light leptons (→ suppress Z backgrounds)One hadronic τVeto ee events (→ suppress fake leptons)Veto b jets (→ not optimal for tuh and tch search!)

æ

æ

æ

æ

æ æ

æ

æ

æ

æ

0 50 100 150 2000

10

20

30

40

mΤΤ

vis @GeV D

Eve

nts�2

0G

eV

tuh coupling K y ut2+ y tu

2= 0.14 O

5.0 + 19.5 fb-1{{Τh

ææ CMS data

CMS predictions

ZZ

Reducible BG

WZ

Our predictionsZZWZtuh Signal

æ

æ

æ

æ

æ æ

æ

æ

æ

æ

0 50 100 150 2000

10

20

30

40

mΤΤ

vis @GeV D

Eve

nts�2

0G

eV

tch coupling K y ct2+ y tc

2= 0.14 O

5.0 + 19.5 fb-1{{Τh

ææ CMS data

CMS predictions

ZZ

Reducible BG

WZ

Our predictionsZZWZtch Signal




Optimized cutsExample: recast CMS search for V + H production

CMS-PAS-HIG-12-053Greljo Kamenik JK, 1404.1278

Result: √y2

ut + y2tu BR(t → hu)

√y2

ct + y2tc BR(t → hc)

Multilepton < 0.19 < 0.01 < 0.23 < 0.015Diphoton plus lepton < 0.12 < 0.0045 < 0.15 < 0.0066Vector boson plus Higgs < 0.16 < 0.0070 < 0.21 < 0.012






F Cluster “fat jets” (R = 1.5)F Uncluster to find three subjets most likely to originate from top decay based on

their invariant mass m123F Along the way, use filtering to remove pile-up and underlying event

contaminationF Impose cuts on invariant masses of subjet pairs to require one pair to be ∼ mW


I Require b tags in likely b subjetsI Dominant backgrounds:

F t tF single topF QCD
















0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40.0

0.2

0.4

0.6

0.8

1.0


m2

3�m

12

3

m23 > mh

m13 > mhm12 > mh

t t ® hhjj ® bb bb jj

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40.0

0.2

0.4

0.6

0.8

1.0


m2

3�m

12

3

m23 > mh

m13 > mhm12 > mh

t t ® W + W - bb ® 4 j+ bb

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40.0

0.2

0.4

0.6

0.8

1.0


m2

3�m

12

3

m23 > mh

m13 > mhm12 > mh

QCD multijet
























Background√

y2ut + y2

tu = 0.1√

y2ct + y2

tc = 0.1t t single-t QCD t → hu t + h t → hc t + h

Analysis 1: th tag + top tagloose th tags 3 510 5.5 125 70 4.0 69 0.57tight th tags 324 0.52 85 28 1.1 26 0.15

Analysis 2: Higgs tag + top tagpreselection 14 800 113 4 125 152 120 209 14.0final cuts 450 2.3 71 6.9 32.6 8.4 1.1













60 80 100 120 140 160 180 20010- 2

10-1

10 0

101

10 2

10 3


Cro

ssse

ctio

npe

rbi

n@

fbD

-3 -2 -1 0 1 2 310- 2

10-1

10 0

101

10 2

10 3


Cro

ssse

ctio

npe

rbi

n@

fbD sing le t

tt

QCD

t+ H

t H t® HjL













Background√

y2ut + y2

tu = 0.1√

y2ct + y2

tc = 0.1t t single-t QCD t → hu t + h t → hc t + h

Analysis 1: th tag + top tagloose th tags 3 510 5.5 125 70 4.0 69 0.57tight th tags 324 0.52 85 28 1.1 26 0.15

Analysis 2: Higgs tag + top tagpreselection 14 800 113 4 125 152 120 209 14.0final cuts 450 2.3 71 6.9 32.6 8.4 1.1







Example: Effective Field Theory

LEFT ⊃ −mi ¯iL`

iR − Y h

ij (¯iL`

jR)h + h.c. ,

Result:

AµτCP =Γ(h→ µ−τ+)− Γ(h→ µ+τ−)

Γ(h→ µ−τ+) + Γ(h→ µ+τ−)

=1− log 2

8πIm[Y hττ

(Y h

eµY h∗eτ Y h∗

µτ − Y hµeY h∗

τe Y h∗τµ

)]∣∣Y hµτ

∣∣2 +∣∣Y hτµ

∣∣2+

18π

m2τ

m2h

∣∣Y hµτ

∣∣2 − ∣∣Y hτµ

∣∣2∣∣Y hµτ

∣∣2 +∣∣Y hτµ

∣∣2 Im[(Y hττ )2] .

... suppressed by m2τ/m2

h and Y heµ, Y h

µe.


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