flavor violating higgs decays
TRANSCRIPT
Flavor Violating Higgs Decays
Joachim Kopp
Galileo Galilei InstituteNovember 26, 2012
Based on work done in collaboration withRoni Harnik and Jure Zupan
arXiv:1209.1397
Joachim Kopp Flavor Violating Higgs Decays 1
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
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 f i
Lf jRh + couplings to heavier Higgs bosons + h.c.
(h = Lightest neutral Higgs boson, mh ∼ 125 GeV)
Assume heavy Higgs boson are decoupled.see for instance Davidson Greiner, arXiv:1001.0434
Joachim Kopp Flavor Violating Higgs Decays 4
Motivation (2)
Scenario 2: Extra Higgs couplingsAssume existence of heavy new particles, which induce effective operators ofthe form
∆LY = −λ′ijΛ2 (f i
Lf jR)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 f i
Lf jRh + h.c.
see for instance Giudice Lebedev, arXiv:0804.1753
Joachim Kopp Flavor Violating Higgs Decays 5
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 Kanemura Ota Tsumura, hep-ph/0505191Blanke Buras Duling Gori Weiler, arXiv:0809.1073Casagrande Goertz Haisch Neubert Pfoh, arXiv:0807.4937Giudice Lebedev, arXiv:0804.1753 Aguilar-Saavedra, arXiv:0904.2387Albrecht Blanke Buras Duling Gemmler, arXiv:0903.2415Buras Duling Gori, arXiv:0905.2318 Azatov Toharia Zhu, arXiv:0906.1990Agashe Contino, arXiv:0906.1542 Davidson Greiner, arXiv:1001.0434Goudelis Lebedev Park, arXiv:1111.1715 Blankenburg Ellis Isidori, arXiv:1202.5704Arhrib Cheng Kong, arXiv:1208.4669 McKeen Pospelov Ritz, arXiv:1208.4597. . .
Joachim Kopp Flavor Violating Higgs Decays 6
Effective Yukawa Lagrangfian
Effective Yukawa Lagrangian
LY = −mi f iLf i
R − Y aij (f i
Lf jR)ha + h.c.+ · · ·
New in this talk:Comprehensive list of up-to-date constraints (including subdominant ones)
Omit approximations where feasibleFirst LHC limitsStrategy for future LHC searches
Joachim Kopp Flavor Violating Higgs Decays 6
Couplings to 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
hτ
µ
µ
µ
Y ∗τµPL + YµτPR
Y ∗µµPL + YµµPR
τ → 3µ, µee, 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.
Joachim Kopp Flavor Violating Higgs Decays 8
Constraints on h→ µe
10- 7 10-6 10- 510- 4 10-310- 2 10-1 100 10110- 7
10-6
10- 5
10- 4
10-3
10- 2
10-1
100
101
ÈYeΜÈ
ÈY ΜeÈ
Μ ® eΓ
M ® M
Μ ® 3e
Μ ® e conv.
Hg-2Le +ED
Me
Hg-2Le for ImHY
Μe YeΜ L=0
EDM
e for ReHYΜe Y
eΜ L=0
ÈYΜe Y
eΜ È=me m
Μ �v 2
BRHh
®ΜeL
=0.99
10-
910
-8
10-
710
-6
10-
510
-4
10-
310
-2
10-
10.5
see also: Blankenburg Ellis Isidori, arXiv:1202.5704Goudelis Lebedev Park, arXiv:1111.1715
Joachim Kopp Flavor Violating Higgs Decays 9
Assumption here:Diagonal Yukawa coupling 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
ÈY ΜΤ È
ÈY ΤΜ
È
Τ®
ΜΓ
Τ ® 3 Μ
H g -2 L Μ
+ED
MΜ
Hg -2 L Μ
�Im
HY ΤΜY ΜΤ
L =0
ÈYΤΜ Y
ΜΤ È =mΜ m
Τ � v 2
BRH
h®
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 Τ
eÈ
Τ®
eΓ
Τ ® eΜΜ
Hg-2 Le +
EDMe
H g-2 L
e forIm H Y
Τe YeΤ L =0
ÈYΤe Y
eΤ È =me m
Τ � v 2
BRH
h®
ΤeL=
0.99
10-
6
10-
5
10-
3
10-
2
10-
1
0.5
EDMe �
Re HYΤe Y
eΤ L =0
Substantial flavor violation (BR(h→ τµ, τe) ∼ 0.01) perfectly viable.
see also: Blankenburg Ellis Isidori, arXiv:1202.5704Goudelis Lebedev Park, arXiv:1111.1715
Davidson Greiner, arXiv:1001.0434
Joachim Kopp Flavor Violating Higgs Decays 10
Assumption here:Diagonal Yukawa coupling unchangedfrom their SM values.
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 in UTfit (Bona et al.), arXiv:0707.0636see also Blankenburg Ellis Isidori, arXiv:1202.5704
Joachim Kopp Flavor Violating Higgs Decays 12
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 in 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
Joachim Kopp Flavor Violating Higgs Decays 12
Couplings involving top quarks
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
Joachim Kopp Flavor Violating Higgs Decays 13
Flavor-Violating Higgs Decaysat the Large Hadron Collider
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
We consider only 2-leptonfinal statesUse VBF cuts(much lower BG than gg fusion)
see howeverDavidson Verdier, arXiv:1211.1248
based 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
Joachim Kopp Flavor Violating Higgs Decays 15
h→ τµ and h→ τe at the LHC
Most important cuts2 forward jets (pT ,j1 > 40 GeV,pT ,j2 > 25 GeV, |∆η| > 3.0,minv
j1,j2 > 350 GeV)
no hard jet activity in betweenno b tags2 opposite sign leptons `1, `2 withpT ,` & 10–20 GeV (depending onflavors)
τ momentum fraction x carried by`1, `2 satisfies 0.1 < x1,2 < 1.0(computed in collinear approximation)
30 GeV < m`` < 75 (100) GeVfor same (opposite) flavor leptons
/ET > 20 (40) GeVfor same (opposite) flavor leptons
based 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
Joachim Kopp Flavor Violating Higgs Decays 15
Mass reconstruction for h→ τ`τ`
Problem: 4 neutrinos in final state
Solution: Assume all τ decay products collinearEllis Hinchliffe Soldate van der Bij, NPB 1987
Per τ :2 unknown (|pντ |, |pν` |)2 constraints: /ET ,x , /ET ,y
Joachim Kopp Flavor Violating Higgs Decays 16
Limits on h→ τµ and h→ τe from the LHC
Technicalities
Use MadGraph 5, v1.4.6,Pythia 6.4, PGSUse only 120–160 GeV binDerive one-sided 95% CL limit
based 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 D
Eve
nts
�10
GeV
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
Result
BR(h→ τµ) < 0.13√
Y 2τµ + Y 2
µτ < 0.011
BR(h→ τe) < 0.13√
Y 2τe + Y 2
eτ < 0.011
Joachim Kopp Flavor Violating Higgs Decays 17
LHC constraints on h→ τµ and h→ τe
10- 3 10- 2 10-1 100
10- 3
10- 2
10-1
100
ÈY ΜΤ È
ÈY ΤΜ
È
Τ®
ΜΓ
Τ ® 3 Μ
H g -2 L Μ
+ED
MΜ
Hg -2 L Μ
�Im
HY ΤΜY ΜΤ
L =0
ÈYΤΜ Y
ΜΤ È =mΜ m
Τ � v 2
BRH
h®
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 Τ
eÈ
Τ®
eΓ
Τ ® eΜΜ
Hg-2 Le +
EDMe
H g-2 L
e forIm H Y
Τe YeΤ L =0
ÈYΤe Y
eΤ È =me m
Τ � v 2
BRH
h®
ΤeL=
0.99
10-
6
10-
5
10-
3
10-
2
10-
1
0.5
EDMe �
Re HYΤe Y
eΤ L =0
Joachim Kopp Flavor Violating Higgs Decays 18
LHC constraints on h→ τµ and h→ τe
10- 3 10- 2 10-1 100
10- 3
10- 2
10-1
100
ÈY ΜΤ È
ÈY ΤΜ
È
Τ®
ΜΓ
Τ ® 3 Μ
H g -2 L Μ
+ED
MΜ
Hg -2 L Μ
�Im
HY ΤΜY ΜΤ
L =0
ÈYΤΜ Y
ΜΤ È =mΜ m
Τ � v 2
Our LHC limitH ATLAS 7 TeV , 4.7 fb - 1 L B
RHh
®Τ
ΜL=
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 Τ
eÈ
Τ®
eΓ
Τ ® eΜΜ
Hg-2 Le +
EDMe
H g-2 L
e forIm H Y
Τe YeΤ L =0
ÈYΤe Y
eΤ È =me m
Τ � v 2
Our LHC limitH ATLAS 7 TeV , 4.7 fb - 1 L
BRH
h®
ΤeL=
0.99
10-
6
10-
5
10-
3
10-
2
10-
1
0.5
EDMe �
Re HYΤe Y
eΤ L =0
Joachim Kopp Flavor Violating Higgs Decays 18
LHC constraints on h→ τµ and h→ τe
10- 3 10- 2 10-1 100
10- 3
10- 2
10-1
100
ÈY ΜΤ È
ÈY ΤΜ
È
Τ®
ΜΓ
Τ ® 3 Μ
H g -2 L Μ
+ED
MΜ
Hg -2 L Μ
�Im
HY ΤΜY ΜΤ
L =0
ÈYΤΜ Y
ΜΤ È =mΜ m
Τ � v 2
Our LHC limitH ATLAS 7 TeV , 4.7 fb - 1 L B
RHh
®Τ
ΜL=
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 Τ
eÈ
Τ®
eΓ
Τ ® eΜΜ
Hg-2 Le +
EDMe
H g-2 L
e forIm H Y
Τe YeΤ L =0
ÈYΤe Y
eΤ È =me m
Τ � v 2
Our LHC limitH ATLAS 7 TeV , 4.7 fb - 1 L
BRH
h®
ΤeL=
0.99
10-
6
10-
5
10-
3
10-
2
10-
1
0.5
EDMe �
Re HYΤe Y
eΤ L =0
Joachim Kopp Flavor Violating Higgs Decays 18
WORLD’S BEST LIMIT!
Strategy for a dedicated h→ τµ and h→ τe search
Possible improvementsDifferent invariant mass formula(assuming 1 neutrino rather than 3)
I Avoids smearing of signalI Shifts Z → ττ peak to
lower invariant mass
Consider hadronic τ ’s(especially for CMS)
Modified cutsI CMS h→ τhadτ` search requires
mT (`, /pT ) < 40 GeV to suppressW + jets
I In h→ τhadµ, neutrino and muontypically not collinear→ large mT (`, /pT )
50 100 150 2000
2
4
6
8
10
12
Transverse mass of the Μ-p�T system @GeV D
Eve
nts
�10G
eV
5 fb-1, 7 TeVMG �Pythia �Delphes
BG rescaled toCMS-HIG -11-029
W+jets
Z+jets
h ® Τ had Τ Μ
h ® Τ had Μ
HÈY ΜΤ2+ÈY ΤΜ
2L1� 2= mΤ
v
QCD BG neglected
Joachim Kopp Flavor Violating Higgs Decays 19
Strategy for a dedicated h→ τµ and h→ τe search
Possible improvementsDifferent invariant mass formula(assuming 1 neutrino rather than 3)
I Avoids smearing of signalI Shifts Z → ττ peak to
lower invariant mass
Consider hadronic τ ’s(especially for CMS)
Modified cutsI CMS h→ τhadτ` search requires
mT (`, /pT ) < 40 GeV to suppressW + jets
I In h→ τhadµ, neutrino and muontypically not collinear→ large mT (`, /pT )
50 100 150 2000
2
4
6
8
10
12
Transverse mass of the Μ-p�T system @GeV DE
ven
ts�10
GeV
5 fb-1, 7 TeVMG �Pythia �Delphes
BG rescaled toCMS-HIG -11-029
W+jets
Z+jets
h ® Τ had Τ Μ
h ® Τ had Μ
HÈY ΜΤ2+ÈY ΤΜ
2L1� 2= mΤ
v
QCD BG neglected
Joachim Kopp Flavor Violating Higgs Decays 19
Strategy for a dedicated h→ τµ and h→ τe search
50 100 150 200 250 3000
5
10
15
20
ΤΜ invariant mass mΤΜ @GeV D
Eve
nts
�10G
eV
5 fb-1, 7 TeVMG �Pythia �Delphes
BG rescaled toCMS-HIG -11-029
W+jets
Z+jets
h ® Τ had Τ Μ
h ® Τ had Μ
HÈY ΜΤ2+ÈYΤΜ
2L1� 2= mΤ
v
QCD BG neglected
50 100 150 200 250 3000
5
10
15
ΤΜ invariant mass mΤΜ @GeV DE
ven
ts�10
GeV
5 fb-1, 7 TeVMG �Pythia �Delphes
BG rescaled toCMS-HIG -11-029
W+jets
Z+jets
h ® Τ had Τ Μ
h ® Τ had Μ
HÈY ΜΤ2+ÈYΤΜ
2L1� 2= mΤ
v
QCD BG neglected
For Yµτ , Yτµ close to the current upper limits, spectacular signals possible.
Joachim Kopp Flavor Violating Higgs Decays 20
Exploiting Higgs production in gluon-gluon fusionDavidson Verdier, arXiv:1211.1248
ObservationsComputed pT ,ν (using collinear approximation) is ' /ET
Muon in h→ τµ is much harder than in h→ τ`τ`.
TEδ
10 8 6 4 2 0 2 4 6 8 10
Even
ts / 0
.2
110
1
10
210 + jets
l
+ l→Z
tt
WW,WZ,ZZ
singlet
SM Higgs
Signal
(GeV)T
Muon p0 20 40 60 80 100 120 140 160 180 200
Even
ts / 2
GeV
110
1
10
210
+ jets
l+
l→Z
tt
WW,WZ,ZZ
singlet
SM Higgs
Signal
Projected sensitivity Davidson Verdier, arXiv:1211.1248
BR(h→ τµ), BR(h→ τe) < 4.5× 10−3
Joachim Kopp Flavor Violating Higgs Decays 21
Exploiting Higgs production in gluon-gluon fusionDavidson Verdier, arXiv:1211.1248
ObservationsComputed pT ,ν (using collinear approximation) is ' /ET
Muon in h→ τµ is much harder than in h→ τ`τ`.
TEδ
10 8 6 4 2 0 2 4 6 8 10
(G
eV
)T
Mu
on
p
0
20
40
60
80
100
120
140
160
180
200
210
110
1
TEδ
10 8 6 4 2 0 2 4 6 8 10
(G
eV
)T
Mu
on
p
0
20
40
60
80
100
120
140
160
180
200
310
210
110
Background Signal
Projected sensitivity Davidson Verdier, arXiv:1211.1248
BR(h→ τµ), BR(h→ τe) < 4.5× 10−3
Joachim Kopp Flavor Violating Higgs Decays 21
Exploiting Higgs production in gluon-gluon fusionDavidson Verdier, arXiv:1211.1248
ObservationsComputed pT ,ν (using collinear approximation) is ' /ET
Muon in h→ τµ is much harder than in h→ τ`τ`.
TEδ
10 8 6 4 2 0 2 4 6 8 10
(G
eV
)T
Mu
on
p
0
20
40
60
80
100
120
140
160
180
200
210
110
1
TEδ
10 8 6 4 2 0 2 4 6 8 10
(G
eV
)T
Mu
on
p
0
20
40
60
80
100
120
140
160
180
200
310
210
110
Background Signal
Projected sensitivity Davidson Verdier, arXiv:1211.1248
BR(h→ τµ), BR(h→ τe) < 4.5× 10−3
Joachim Kopp Flavor Violating Higgs Decays 21
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 Constraints from `1 → `2 + γ, `1 → `2 + X , µ–e conversion in nuclei, g − 2,
EDMs, M–M oscillationsI Strong constraints in the µ–e sectorI Very weak constraints in the τ–e and τ–µ sectors
In the quark sector:I Strong constraints on couplings to light quarksI Very weak constraints on couplings to top quarks
At the LHCI Constraints on anomalous top–Higgs couplings from single top productionI A recast ATLAS h→ τ`τ` search already provides strongest limits on
h→ τµ and h→ τeI A dedicated search would be much more sensitive
Joachim Kopp Flavor Violating Higgs Decays 22
Thank you!