Searches for Higgs bosons decaying to lepton pairs with the CMS detector!

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Searches for Higgs bosons decaying to lepton pairs with the CMS detector!

Jan Steggemann (CERN)!

on behalf of the CMS collaboration!

4 July 2014!

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Motivation!

2!

!

•  Does the Higgs boson decay to leptons/fermions? (H→ττ)!

•  Measurement of fermionic and bosonic couplings

(H→ττ)!

•  Enhanced decay rate to 2 nd generation leptons? (H→µµ)!

•  Lepton ﬂavour violation?

(H→µτ) – new result!

Jan Steggemann!

V

0 0.5 1 κ 1.5

f

κ

0 0.5 1 1.5

2

95% C.L.

b

→ b H

τ τ H →

→ ZZ H

→ WW H

γγ H →

CMS Preliminary s = 7 TeV, L ≤ 5.1 fb^-1 s = 8 TeV, L ≤ 19.6 fb^-1

SM Higgs Fermiophobic Bkg. only

Higgs couplings as of Moriond 2013

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Higgs Production and Event Categories!

3!

Gluon fusion (87%)

$0-jet/≥1-jet!

Jan Steggemann!

2 2 Analysis overview

and vector boson fusion (VBF), final states with H ! ^tt decays contain only two charged leptons, defining theLL⁰ channels. All sixt-pair final states are studied: LL⁰ = µt_h, et_h,t_ht_h, eµ,µµ, and ee.

q

g g

H

W/Z W/Z

q q

q H q

W /Z

q

¯ q

W/Z H

Figure 1: Leading-order Feynman diagrams for Higgs boson production through gluon-gluon fusion (left), vector boson fusion (middle), and the associated production with a W or a Z boson (right).

Sensitivity to the associated production with a W or a Z boson is achieved by requiring one or two additional electrons or muons compatible with leptonic decays of the W or Z boson. The four most sensitive final states are retained in the `+Lt_h channels aiming at the associated production with a W boson, `+Lt_h = µ+µt_h, e+µt_h/µ+et_h, µ+t_ht_h, and e+t_ht_h. In the``+LL⁰ channels that target the associated production with a Z boson decaying to``, the t-pair final statesµt_h, et_h, eµ, and t_ht_h are considered, leading to eight channels in total. The ee and µµt-pair final states are excluded because the corresponding events are already used in the search for H!^ZZ!⁴`[11].

To maximize the sensitivity of the analysis in theLL⁰channels, events are classified in categories according to the number of jets in the final state, excluding the jets corresponding to theLand L⁰ leptons. The events are further classified according to a number of kinematic quantities that exhibit different distributions for signal and background events (see section 6). In particular, the contribution of the VBF production process is enhanced for events with two or more jets by requiring a large rapidity gap between the two jets with the highest transverse momentum.

For the remaining events with at least one jet, requiring a largep_T of the reconstructed Higgs boson candidate increases the sensitivity to Higgs boson production through gluon fusion. A complete listing of all lepton final states and event categories is given in appendix B.

With the exception of the`+Lt_h, ee, andµµchannels, the signal is extracted from the distribution of the invariant mass of thet-lepton pair,mtt, calculated from theLandL⁰four-momenta and the missing transverse energy vector. In the`+Lt_h channels, the signal extraction is in- stead based on the invariant mass,mvis, of the visibleLt_h decay products because the missing transverse energy does not entirely arise from the neutrinos produced in the decay of the twot leptons. In the ee andµµchannels, a discriminating variable combining a number of kinematic quantities and other observables, includingmtt, is used.

The background composition depends on the channel and, in particular, on the number of electrons and muons in the final state. The Drell–Yan production of a Z boson decaying into a pair oft leptons constitutes the main irreducible background in allLL⁰ channels. Another source of background with the same leptonic final state is the production of top-quark pairs (tt), which is most important in the eµchannel. Reducible background contributions include QCD multijet production that is particularly relevant in thet_ht_hchannel and W(! `n) +jets production with a jet misidentified as a t_h in the `t_h channels. In the `+Lt_h and ``+LL⁰

and vector boson fusion (VBF), final states with H ! ^tt decays contain only two charged leptons, defining the LL⁰ channels. All sixt-pair final states are studied: LL⁰ = µt_h, et_h,t_ht_h, eµ,µµ, and ee.

q

g g

H

W/Z W/Z

q q

q H q

W /Z

q

¯ q

W/Z H

Sensitivity to the associated production with a W or a Z boson is achieved by requiring one or two additional electrons or muons compatible with leptonic decays of the W or Z boson. The four most sensitive final states are retained in the `+Lt_h channels aiming at the associated production with a W boson, `+Lt_h = µ+µth, e+µth/µ+et_h, µ+thth, and e+thth. In the``+LL⁰ channels that target the associated production with a Z boson decaying to``, the t-pair final statesµt_h, et_h, eµ, andt_ht_hare considered, leading to eight channels in total. The ee and µµ t-pair final states are excluded because the corresponding events are already used in the search for H !^ZZ!⁴`[11].

To maximize the sensitivity of the analysis in theLL⁰channels, events are classified in categories according to the number of jets in the final state, excluding the jets corresponding to theLand L⁰leptons. The events are further classified according to a number of kinematic quantities that exhibit different distributions for signal and background events (see section 6). In particular, the contribution of the VBF production process is enhanced for events with two or more jets by requiring a large rapidity gap between the two jets with the highest transverse momentum.

For the remaining events with at least one jet, requiring a large p_T of the reconstructed Higgs boson candidate increases the sensitivity to Higgs boson production through gluon fusion. A complete listing of all lepton final states and event categories is given in appendix B.

With the exception of the`+Lt_h, ee, andµµchannels, the signal is extracted from the distribution of the invariant mass of thet-lepton pair,mtt, calculated from theLandL⁰four-momenta and the missing transverse energy vector. In the`+Lt_hchannels, the signal extraction is in- stead based on the invariant mass, m_vis, of the visibleLt_hdecay products because the missing transverse energy does not entirely arise from the neutrinos produced in the decay of the twot leptons. In the ee andµµchannels, a discriminating variable combining a number of kinematic quantities and other observables, includingmtt, is used.

The background composition depends on the channel and, in particular, on the number of electrons and muons in the final state. The Drell–Yan production of a Z boson decaying into a pair of t leptons constitutes the main irreducible background in all LL⁰ channels. Another source of background with the same leptonic final state is the production of top-quark pairs (tt), which is most important in the eµchannel. Reducible background contributions include QCD multijet production that is particularly relevant in the t_ht_h channel and W(! `n) +jets production with a jet misidentified as a t_h in the`t_h channels. In the `+Lt_h and ``+LL⁰

and vector boson fusion (VBF), final states with H ! ^tt decays contain only two charged leptons, defining theLL⁰ channels. All sixt-pair final states are studied: LL⁰ = µth, et_h,thth, eµ,µµ, and ee.

q

g g

H

W/Z W/Z

q q

q H q

W /Z

q

¯ q

W/Z H

Sensitivity to the associated production with a W or a Z boson is achieved by requiring one or two additional electrons or muons compatible with leptonic decays of the W or Z boson. The four most sensitive final states are retained in the `+Lt_h channels aiming at the associated production with a W boson, `+Lt_h = µ+µt_h, e+µt_h/µ+et_h, µ+t_ht_h, and e+t_ht_h. In the``+LL⁰ channels that target the associated production with a Z boson decaying to``, the t-pair final statesµth, et_h, eµ, andththare considered, leading to eight channels in total. The ee and µµ t-pair final states are excluded because the corresponding events are already used in the search for H!^ZZ!⁴`[11].

To maximize the sensitivity of the analysis in theLL⁰channels, events are classified in categories according to the number of jets in the final state, excluding the jets corresponding to theLand L⁰leptons. The events are further classified according to a number of kinematic quantities that exhibit different distributions for signal and background events (see section 6). In particular, the contribution of the VBF production process is enhanced for events with two or more jets by requiring a large rapidity gap between the two jets with the highest transverse momentum.

For the remaining events with at least one jet, requiring a large p_T of the reconstructed Higgs boson candidate increases the sensitivity to Higgs boson production through gluon fusion. A complete listing of all lepton final states and event categories is given in appendix B.

With the exception of the`+Lt_h, ee, andµµchannels, the signal is extracted from the distribution of the invariant mass of thet-lepton pair,mtt, calculated from theLandL⁰four-momenta and the missing transverse energy vector. In the `+Lt_h channels, the signal extraction is in- stead based on the invariant mass,m_vis, of the visibleLt_hdecay products because the missing transverse energy does not entirely arise from the neutrinos produced in the decay of the twot leptons. In the ee andµµchannels, a discriminating variable combining a number of kinematic quantities and other observables, includingmtt, is used.

The background composition depends on the channel and, in particular, on the number of electrons and muons in the final state. The Drell–Yan production of a Z boson decaying into a pair of t leptons constitutes the main irreducible background in all LL⁰ channels. Another source of background with the same leptonic final state is the production of top-quark pairs (tt), which is most important in the eµchannel. Reducible background contributions include QCD multijet production that is particularly relevant in the t_ht_h channel and W(! `n) +jets production with a jet misidentified as a t_h in the `t_h channels. In the `+Lt_h and ``+LL⁰

VBF (7%)

$2-jet/VBF tag!

(2 jets with rapidity gap, no central jet)!

WH/ZH (6%)

$ VH!

(additional muons/

electrons from Z/W boson decay)!

Higgs decay branching fractions to leptons

•  H→ττ: 6.3%; H→µµ = 0.02% (m

H

= 125 GeV)!

•  H→τµ: < 10% (exp.)!

!

H→ττ

All analyses

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[GeV]

τ

mτ

0 50 100 150 200 250

[1/GeV]ττ1/dm

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16

= 125 GeV mH

τ τ H →

τ τ

→ Z = 8 TeV s

CMS Simulation µτ_h

[GeV]

mvis

0 50 100 150 200 250

[1/GeV]vis1/dm

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

= 125 GeV mH

τ τ H →

τ τ

→ Z = 8 TeV s

CMS Simulation µτ_h

Visible mass

SVFit mass

τ

_h

τ

_h

42%

τ

_h

µ 23%

τ

_h

e 23%

eµ 6%

ee 3%

µµ 3%

Search for H→ ττ: Strategy !

4!

!

•  Include all 6 di-tau decay channels

–  0-jet, 1-jet, and VBF-tag categories (gluon fusion & VBF)!

–  In addition, l+ττ (WH) and ll+ττ (ZH) ﬁnal states!

•  Observable: reconstructed di-tau mass with ! resolution of 10-20%!

–  Maximum likelihood ﬁt!

using di-tau decay products ! and missing energy!

! !

•  Optimisation!

–  Further divide events in categories!

based on lepton p T , di-tau p T, and VBF-jet properties !

Jan Steggemann!

JHEP05(2014)104!

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Challenges!

5!

•  Excellent control of all backgrounds!

•  Experimental: missing energy, forward jets, hadronic tau identiﬁcation!

Jan Steggemann!

41

[GeV]

τ

mτ

0 100 200 300

[1/GeV]ττdN/dm

0 5 10 15 20 25 30 35

40 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

1-jet high pT

boosted

τ τ SM H(125 GeV)→ Observed

τ τ Z→

t t

Electroweak QCD

Bkg. uncertainty

[GeV]

τ

mτ

0 100 200 300

0 20 40 60 80 100 120 140

160 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

0-jet high pT τ τ SM H(125 GeV)→ Observed

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0 10 20 30 40 50 60

70 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0.0 0.1 0.2 0.3 0.4 0.5

at 8 TeV CMS, 19.7 fb-1

τh

µ

Tight VBF tag

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0 200 400 600 800 1000 1200 1400

at 8 TeV CMS, 19.7 fb-1

τh

µ

τh

0-jet low pT

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0 20 40 60 80 100 120 140 160 180 200 220

240 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

1-jet low pT

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

2.0 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

Loose VBF tag

τ τ Z→

t t

Figure 20: Observed and predicted m tt distributions in the µt h channel, for all categories used in the 8 TeV data analysis. The normalization of the predicted background distributions corre- sponds to the result of the global fit. The signal distribution, on the other hand, is normalized to the SM prediction. The signal and background histograms are stacked.

τ

h

r ec on st ru ct io n e ﬃ ci en cy

τ

_h

energy scale

[GeV]

τ

m

τ

0 100 200 300

[1/GeV]

ττ

S / ( S+ B ) W e ig h ted d N/ dm

0 500 1000 1500 2000 2500

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

-40 -20 0 20

40 SM H(125 GeV)^→^τ^τ

Data - background Bkg. uncertainty

at 8 TeV at 7 TeV, 19.7 fb-1

CMS, 4.9 fb-1

, eµ τh

τh h, , eτ τh

µ

41

[GeV]

τ

mτ

0 100 200 300

0 5 10 15 20 25 30 35

40 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

1-jet high pT

boosted

τ τ

→ SM H(125 GeV) Observed

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0 20 40 60 80 100 120 140

160 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

τ τ

→ Z

t t

[GeV]

τ

mτ

0 100 200 300

0 10 20 30 40 50 60

70 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

τ τ

→ Z

t t

[GeV]

τ

mτ

0 100 200 300

0.0 0.1 0.2 0.3 0.4 0.5

at 8 TeV CMS, 19.7 fb-1

τh

µ

Tight VBF tag

τ τ

→ Z

t t

[GeV]

τ

mτ

0 100 200 300

0 200 400 600 800 1000 1200 1400

at 8 TeV CMS, 19.7 fb-1

τh

µ

τh

0-jet low pT

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0 20 40 60 80 100 120 140 160 180 200 220

240 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

1-jet low pT

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

2.0 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

Loose VBF tag

τ τ Z→

t t

Figure 20: Observed and predicted m tt distributions in the µt h channel, for all categories used in the 8 TeV data analysis. The normalization of the predicted background distributions corre- sponds to the result of the global fit. The signal distribution, on the other hand, is normalized to the SM prediction. The signal and background histograms are stacked.

41

[GeV]

τ

mτ

0 100 200 300

0 5 10 15 20 25 30 35

40 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

1-jet high pT

boosted

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0 20 40 60 80 100 120 140

160 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

0-jet high pT τ τ

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0 10 20 30 40 50 60

70 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

1-jet high pT τ τ

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0.0 0.1 0.2 0.3 0.4 0.5

at 8 TeV CMS, 19.7 fb-1

τh

µ

Tight VBF tag

τ τ

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0 200 400 600 800 1000 1200 1400

at 8 TeV CMS, 19.7 fb-1

τh

µ

τh

0-jet low pT

τ τ

→ Z

t t

[GeV]

τ

mτ

0 100 200 300

0 20 40 60 80 100 120 140 160 180 200 220

240 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

1-jet low pT

τ τ

→ Z

t t

[GeV]

τ

mτ

0 100 200 300

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

2.0 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

Loose VBF tag

τ τ

→ Z

t t

Figure 20: Observed and predicted m tt distributions in the µt h channel, for all categories used in the 8 TeV data analysis. The normalization of the predicted background distributions corre- sponds to the result of the global fit. The signal distribution, on the other hand, is normalized to the SM prediction. The signal and background histograms are stacked.

41

[GeV]

τ

mτ

0 100 200 300

0 5 10 15 20 25 30 35

40 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

1-jet high pT

boosted

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0 20 40 60 80 100 120 140

160 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0 10 20 30 40 50 60

70 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0.0 0.1 0.2 0.3 0.4 0.5

at 8 TeV CMS, 19.7 fb-1

τh

µ

Tight VBF tag

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0 200 400 600 800 1000 1200 1400

at 8 TeV CMS, 19.7 fb-1

τh

µ

τh

0-jet low pT

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0 20 40 60 80 100 120 140 160 180 200 220

240 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

τh

1-jet low pT

τ τ Z→

t t

[GeV]

τ

mτ

0 100 200 300

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

2.0 ^{at 8 TeV}

CMS, 19.7 fb-1

τh

µ

Loose VBF tag

τ τ Z→

t t

Figure 20: Observed and predicted m tt distributions in the µt h channel, for all categories used

in the 8 TeV data analysis. The normalization of the predicted background distributions corre-

sponds to the result of the global fit. The signal distribution, on the other hand, is normalized

to the SM prediction. The signal and background histograms are stacked.

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Signiﬁcance and mass!

6!

!

•  3.2 sigma evidence for H→ττ decays (3.7 expected) at ! m H = 125 GeV

•  Mass: 122 ± 7 GeV – compatible with 125 GeV!

!

Jan Steggemann!

[GeV]

m

H

100 120 140

lnL ∆ -2

0 5 10 15 20

Observed Parabolic fit

H (125 GeV) Expected Expected 1σ

±

Expected 2σ

±

1σ 2σ at 8 TeV at 7 TeV, 19.7 fb-1

, 4.9 fb-1

τ τ CMS H→

[GeV]

m

H

100 120 140

Local p-value

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

1

5σ 4σ 3σ 2σ 1σ

Observed p-value

H) Expected for SM H(m

at 8 TeV at 7 TeV, 19.7 fb-1

, 4.9 fb-1

τ τ CMS H→

(7)

Best fit µ

0 2 4

0-jet

±1.09 0.34

1-jet

±0.46 1.07

2-jet (VBF tag)

±0.41 0.94

τ

h

L + l ' + LL + ll

±1.02 -0.33

τ τ H →

±0.27 0.78 = 125 GeV

mH

at 8 TeV at 7 TeV, 19.7 fb-1

CMS, 4.9 fb-1

Signal strength by jet/lepton multiplicity!

7!

!

•  Most of the sensitivity from VBF and 1-jet categories!

–  0-jet category constrains backgrounds and tau energy scale!

•  Best ﬁt signal strength modiﬁer µ = 0.78 ± 0.27

!

Jan Steggemann!

(8)

Couplings!

8!

!

•  Constraints on !

fermionic and bosonic!

couplings!

–  compatible with SM expectation

•  Sensitivity to bosonic!

coupling from VBF!

production and H→WW ! decays (in particular in ! eµ channel)!

Jan Steggemann!

H→WW decays treated as signal"

31

[GeV]

m

H

100 120 140

lnL ∆ -2

0 5 10 15 20

Observed Parabolic fit

H (125 GeV) Expected Expected

1σ

±

Expected 2σ

±

1 σ 2 σ

at 8 TeV at 7 TeV, 19.7 fb-1

, 4.9 fb-1

τ τ CMS H→

κ

V

0.0 0.5 1.0 1.5 2.0

f

κ

0.0 0.5 1.0 1.5 2.0

95% CL 68% CL Best fit SM

= 125 GeV m

H

at 8 TeV at 7 TeV, 19.7 fb-1

, 4.9 fb-1

τ τ CMS H→

Figure 18: Scan of the negative log-likelihood difference, 2D ln L , as a function of m H (left) and as a function of k V and k f (right). For each point, all nuisance parameters are profiled. For the likelihood scan as a function of m H , the background-only hypothesis includes the pp ! H(125 GeV) ! WW process for every value of m H . The observation (solid line) is compared to the expectation (dashed line) for a SM Higgs boson with mass m H = 125 GeV. For the likelihood scan as a function of k V and k f , the H ! WW contribution is treated as a signal process.

10 Summary

We report a search for the standard model Higgs boson decaying into a pair of t leptons. The search is based on the full proton-proton collision sample recorded by CMS in 2011 and 2012, corresponding to an integrated luminosity of 4.9 fb 1 at a centre-of-mass energy of 7 TeV and 19.7 fb 1 at 8 TeV. The analysis is performed in six channels corresponding to the final states µt h , et h , t h t h , eµ, µµ, and ee. The gluon-gluon fusion and vector-boson fusion production of a Higgs boson are probed in the one-jet and two-jet final states, respectively, whereas the production of a Higgs boson in association with a W or Z boson decaying leptonically is tar- geted by requiring additional electrons or muons in the final state. An excess of events over the background-only hypothesis is observed with a local significance in excess of 3 standard deviations for Higgs boson mass hypotheses between m H = 115 and 130 GeV, and equal to 3.2 standard deviations at m H = 125 GeV, to be compared to an expected significance of 3.7 standard deviations. The best fit of the observed H ! tt signal cross section times branching fraction for m H = 125 GeV is 0.78 ± 0.27 times the standard model expectation. Assum- ing that this excess corresponds to a Higgs boson decaying to tt, its mass is measured to be m H = 122 ± 7 GeV. These results constitute evidence for the coupling between the t lepton and the 125 GeV Higgs boson discovered in 2012 by the ATLAS and CMS Collaborations.

Acknowledgements

We congratulate our colleagues in the CERN accelerator departments for the excellent perfor-

mance of the LHC and thank the technical and administrative staffs at CERN and at other CMS

institutes for their contributions to the success of the CMS effort. In addition, we gratefully

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Higgs decays to fermions!

9!

!

•  Combination with VH→bb (previous talk)!

•  Observed (expected)

combined signiﬁcance of!

3.8 (4.4) sigma !

•  Best-ﬁt signal strength!

µ = 0.83 ± 0.24!

•  Evidence for direct decay of the Higgs boson to

fermions

!

Jan Steggemann!

µ

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

ln L ∆ 2 −

2 4 6 8 10 12 14 16 18 20

1σ 2σ 3σ 4σ 5σ

2.1 σ 3.2 σ 3.8 σ

= 125 GeV m

H

b

→ b VH

τ τ H →

Combined

CMS

s = 7 TeV, L = 5 fb^-1; s = 8 TeV, L = 19−20 fb^-1

model standard

Nature Physics 10 (2014)

Advance online publica<on

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2] ) [GeV/c µ M(µ 2 Events/1.0 GeV/c

0 1000 2000 3000 4000 5000 6000 7000 8000

9000 ^Data

Background Model

× 20

=125 GeV Signal mH

CMS Preliminary S/(S+B) Weighted

=7 TeV L = 5.0 fb-1

s

=8 TeV L = 19.7 fb-1

s

2] ) [GeV/c µ

M(µ

110 120 130 140 150 160

FitData-Fit

-3 -2 -1 0 1 2 3

2] [GeV/c mH

120 130 140 150

)µµ→ (H SMσ/σ95% CL Limit on

0 5 10 15 20 25 30 35 40

CMS Preliminary = 7 TeV L = 5.0 fb-1

s

= 8 TeV L = 19.7 fb-1

s

Combination

Search for H→ µµ !

10!

•  Fit of parameterised background & signal shapes in various event categories!

•  Observed limit: µ(H→ µµ ) < 7.4 x SM expectation (5.1 expected)!

–  Similar results in H→ee channel!

•  As expected, Higgs boson decays to leptons are not universal

!

Jan Steggemann!

CMS-PAS-HIG-13-007

Signal x 20

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A. Levine 3

SM H→ττ

●

H→τ μ τ h and H→τ μ τ e have a very similar signature to H→μτ

●

Allows us to use many of the same methods as the CMS SM H→ττ analysis

●

Differences in event topology

– Harder P T spectrum of muons

– Different Δ ϕ μ-MET Δ ϕ τ-MET

Search for H→ µτ !

11!

!

•  Previous best limits on B(H→µτ) <~ 10% from reinterpretation of LHC H→ττ searches and from τ→µγ$

arXiv:1209.1397!

–  Can do better with ﬁrst dedicated search

•  Consider hadronic (τ h ) and electron (τ e ) tau decays!

•  Same basic event selection and jet categories as SM H→ττ analysis (0-jet, 1-jet, VBF-tag)!

•  Diﬀerences in kinematics!

–  Harder muon p T spectrum –  Δϕ between µ, τ h /τ e , !

missing energy vector

!

CMS-PAS-HIG-14-005

Jan Steggemann!

NEW RESULT

(12)

Events / 20 GeV

0 1 2 3 4 5 6 7

τe

Data, µ

Bckg Uncertainty SM Higgs

(embedded) τ

Z+τ

e)

µτ (not τ l-

Z+l+

Single top quark +Jets t t

* γ / W γ W VV Fake leptons LFV Higgs (Br=0.9%)

= 8 TeV s

-1, 19.7 fb CMS preliminary

) [GeV]

τe

collinear M(µ

0 100 200 300

Bckg (fit)Data-Bckg (fit)

-0.5 0 0.5

Events / 10 GeV

0 100 200 300 400 500 600 700

τe

Data, µ Bckg Uncertainty SM Higgs

(embedded) τ Z+τ

l-

Z+l+

Single top quark t

t VV

* γ / W γ W

Fakes (leptons) LFV GG Higgs (Br=100%) LFV VBF Higgs (Br=100%)

= 8 TeV s

) [GeV]

τe

collinear M(µ

0 100 200 300

BckgData-Bckg -0.5

0 0.5

Observable and ﬁnal selection!

12!

•  Collinear approximation to reconstruct Higgs boson mass!

•  Optimise selection for each category based on various kinematic variables !

!

Jan Steggemann!

Full selection

µτ

_e

VBF-tag pre-selection

µτ

_e

VBF-tag ﬁnal selection

B = 100% B = 0.9%

(13)

Events / 10 GeV

0 100 200 300 400

500 ^had

τ µ Data, Bckg Uncertainty SM H

had) µτ (not τ l- Z+l+ Single top quark

+Jets t t VV

) τ

→ Fakes (jet LFV Higgs (Br=0.9%)

= 8 TeV s

) [GeV]

τhad

collinear M(µ

100 200 300

-0.5 0 0.5

Events / 20 GeV

0 1 2 3 4 5 6 7

τe

(embedded) τ τ Z+

e)

µτ (not τ l-

Z+l+

= 8 TeV s

) [GeV]

τe

collinear M(µ

0 100 200 300

-0.5 0 0.5

Final collinear mass distributions!

Jan Steggemann! 13!

VBF-tag

Events / 10 GeV

0 10 20 30 40 50 60

τe

e)

µτ (not τ l-

Z+l+

= 8 TeV s

) [GeV]

τe

collinear M(µ

50 100 150 200 250 300

-0.5 0 0.5

Events / 10 GeV

0 10 20 30 40 50 60

τe

e)

µτ (not τ l-

Z+l+

= 8 TeV s

) [GeV]

τe

collinear M(µ

50 100 150 200 250 300

-0.5 0 0.5

µτ

_e

µτ

_h

1-jet 0-jet

B = 0.9%

Events / 50 GeV

0 2 4 6 8 10 12 14 16 18 20

τhad µ Data, Bckg Uncertainty SM H

+Jets t t VV

) τ

= 8 TeV s

) [GeV]

τhad

collinear M(µ

0 100 200 300

Bckg (fit)Data-Bckg (fit) -0.50 0.5 1

VBF-tag

Events / 10 GeV

0 20 40 60 80 100 120 140 160 180

τhad µ Data, Bckg Uncertainty SM H

+Jets t t VV

) τ

= 8 TeV s

) [GeV]

τhad

collinear M(µ

0 100 200 300

-0.5 0 0.5

1-jet

0-jet

(14)

τ ), % µ

95% CL Limit on Br(h →

0 2 4 6 8 10

1.57% (obs.) 0.75% (exp.)

τ µ h →

3.84% (obs.) 3.77% (exp.)

, 2 Jets τ

e

µ

2.38% (obs.) 1.66% (exp.)

, 1 Jet τ

e

µ

2.04% (obs.) 1.32% (exp.)

, 0 Jets τ

e

µ

3.29% (obs.) 1.95% (exp.)

, 2 Jets τ

had

µ

2.11% (obs.) 2.10% (exp.)

, 1 Jet τ

had

µ

2.94% (obs.) 2.35% (exp.)

, 0 Jets τ

had

µ

Observed Expected

1σ Expected ±

2σ Expected ±

= 8 TeV s

-1

, 19.7 fb CMS preliminary

Limits on H→µτ branching ratio!

14!

! !

•  Comparable sensitivity!

from all channels!

•  Observed limit 1.57% (exp.

0.75%)!

!

•  Large improvement of previous limits!

•  Background-only

p-value of 0.007 (2.46σ)

–  Best-ﬁt ! B(H→µτ) =

!

Jan Steggemann!

12 8 Results

category in Tables 7 and 8. Combining all the channels an expected upper limit of B ( H !

238

µt ) < 0.75% ± 0.38% is obtained. The observed upper limit is B ( H ! µt ) < 1.57% which

239

exceeds the expected limit due to a slight excess of events. The fit can then be used to estimate

240

the branching fraction if this excess were to be interpreted as a signal.

241

The best fit values for the branching fractions are given in table 9. The limits and best fit

242

branching fractions are also summarized graphically for comparison in Figure 5. The combined

243

categories give a best fit of B ( H ! µt ) = 0.89 + 0.40 0.37 %.

244

Finally the categories are combined in Figure 6 which also shows a MC Higgs signal for a

245

branching fraction of 0.89%. The combined excess is 2.5 s which corresponds to a p-value of

246

0.007. The combined plot in which each category is weighted by “global” significance is shown

247

in figure 7. Global significance means the significance (S / ( S + B ) ) i

Searches for Higgs bosons decaying to lepton pairs with the CMS detector!