Discovering the Higgswith Low Mass Muon Pairs

Jay WackerSLAC

June 3, 2009

with Mariangela LisantiarXiv:0903.1377

Plan of the Talk

Motivation for New Higgs Decay Modes

Analysis of Higgs Decaying into PNGBs

Searching for the Higgs at Hadron Colliders

Where is the Higgs Boson?

Higgs Mass (GeV)

95% 90%

Excluded by Tevatron

LEP Exclusion

95%

Excluded by Indirect Searches

95%

100 120 140 160 180 200

The shrinking parameter space

Z0

Z0!

h0

e+

e!b, !!

b̄, !+

gh0

W+

W!g

W! W!

!!

h0

Most BSM predicts light Higgs

Tension is between solving the Big Hierarchy Problem & Higgs Mass

! !MGUT

A.) Higgs is an elementary scalar (i.e. susy)quartic coupling is IR free and runs weak

B.) Higgs is a composite PNGB (i.e. LH or A5)quartic generated radiatively off SM couplings

LEP Limit usually leads to Little Hierarchy Problem (1 - 10% fine tuning)

C.) Higgs is a strongly interacting composite (RS)quartic is large, but usually Flavor/Precision EW problems

Mcomposite ! 10" 30 TeV

If there is BSM Physics,Higgs discovery can be easily altered

!h0 SM

mh0=

3m2b

4!v2! 10!4

h0

b

b̄

h0

X̄

X !h0 BSM

mh0=

g2hXX̄

4!! 10!2

New physics could open up unsuppressed decay channels

Br(h0 ! SM) " 10!2

Existing search strategies could be ineffective

EWSB/Higgs sector is extended

Additional approximate symmetries

Light PNGBs

New Higgs decay modes

Not a complicated story!

Minimal Module: 2 HDM + Singlet

3 U(1) Symmetries

Hu Hd S

Hypercharge + 2 Global

Hu ! v sin! eiau/vs! Hd ! v cos ! eiad/vc! S ! s eias/s

Eaten Z0 Goldstone Active A0 Inert a0

3 Pseudoscalars

Use Exp. basis for pseudoscalars

V0 ! |!|2, |!|4

Higgs Potential

Gives mass to non-PNGBs and EWSB

Globally invariant terms

V0 ! |!|2, |!|4

Higgs Potential

Gives mass to non-PNGBs and EWSB

Globally invariant terms

tan !a =v

!S" sin 2"

Gives mass to A0

Defines mixing angle between activeand inert pseudoscalars

V1 = !1S2H†

uH†d + h.c.

Explicit breaking of 1st U(1)

Determines all coupling not suppressed by ma0

V0 ! |!|2, |!|4

Higgs Potential

Gives mass to non-PNGBs and EWSB

Globally invariant terms

tan !a =v

!S" sin 2"

Gives mass to A0

Defines mixing angle between activeand inert pseudoscalars

V1 = !1S2H†

uH†d + h.c.

Explicit breaking of 1st U(1)

Determines all coupling not suppressed by ma0

V2 = !2S2HuHd + h.c.

Explicit breaking of 2nd U(1)

V2! = !2!S4 + h.c.Gives mass to a0

Determines symmetry breaking couplings

Lint = c̃hv

!S"2 h0!µa0!µa0 # d̃hm2

a0

vh0a0a0

Higgs Decaying Into PNGBs

c̃h = sin2 !a!S"2

v2=

sin2 2"

1 + v2 sin2 2!!S"2

# 4tan2 "

Symmetry preserving a0 ! a0 + !

Exists for exact Goldstones

Max size at sin !a = 1

!S" acts as decay constant

h0

v(!a0)2

Symmetry violating

d̃h =1

1 + 2!2! sin 2"!2 tan2 #a

>! 1 if !2! " #!2 tan2 "a

2 sin 2#

d̃h = 1 !2 ! !2!

Lint = c̃hv

!S"2 h0!µa0!µa0 # d̃hm2

a0

vh0a0a0

Higgs Decaying Into PNGBs

c̃h = sin2 !a!S"2

v2=

sin2 2"

1 + v2 sin2 2!!S"2

# 4tan2 "

Symmetry preserving a0 ! a0 + !

Exists for exact Goldstones

Max size at sin !a = 1

!S" acts as decay constant

h0

v(!a0)2

Branching Fraction to a0

500 1000 1500 2000

0.01

0.02

0.05

0.10

0.20

0.50

1.00

!s"!sin2b "GeV#

Br"h#"

aa#

5%

100 120 140 160 180 200

0.05

0.10

0.20

0.50

1.00

m_h !GeV"1!MaxBr!h!"

aa"

10%

20%

50%

100%

Br(

h0!

a0a0

)

!S"/ sin 2! (GeV)

mh0 (GeV)100 120 140 160 180 200

mh0 = 100 GeV

5%

10%

20%

50%

Min

Br(

h0!

SM)

2%

1%

100%

symmetry-preserving interaction dominates

below 1 TeVd̃h = 1

d̃h = 0

Up to 98% into PNGBs!

Symmetry preserving decays dominate unless a0 fine tuned lightmoderate !S"

!h0!a0a0

mh0!

c̃2hm4

h0

"S#4 +d̃2

hm4a0

v2m2h0

Lint = igfmf

vf̄!5fa0

gf = sin !a

!cot" (up-type quarks)tan " (down-type quarks/leptons)

suppressed by 2 powers of tan !

Coupling to SM Fermions

sin !a ! v

"S# tan"

!S"Small ! strong coupling of a0 to fermions

Lint = igfmf

vf̄!5fa0

gf = sin !a

!cot" (up-type quarks)tan " (down-type quarks/leptons)

suppressed by 2 powers of tan !

Coupling to SM Fermions

Below bottom threshold, a0 decays to taus over charm quarks

h0 ! a0a0 ! (!+!!)(!+!!)Possible dominant Higgs decay mode:

sin !a ! v

"S# tan"

!S"Small ! strong coupling of a0 to fermions

85 90 95 100 105 110 1150

200

400

600

800

Higgs Mass !GeV"

!S"!GeV

"

Higgs Mass (GeV)

!S"/

sin

2!(G

eV)

h0!

4!

h0 ! SM(LEP)

(LE

P)

Living Beneath 114 GeV...LEP famously only searched for

h0 ! a0a0 ! (!+!!)(!+!!) mh0 ! 86 GeV3.5 GeV ! ma0 ! 9.5 GeVIf there is a large BR into a0s and

if

mh0 ! 114 GeV and may be less fine tuning

4 5 6 7 8 90.0

0.5

1.0

1.5

2.0

m_a !GeV"

!!gd

ma0 (GeV)

!S"/ sin 2! # 1000 GeV

!S"/ sin 2! # 500 GeV

!S"/ sin 2! # 250 GeV

CLEO places bounds on a0 coupling

Direct a0 searches

mh0 ! 114 GeV Becoming constrained

Br(!! a0!)Br(!! µ+µ!)

=GF m2

!

4"

2"#g2

d!!

a0

unless explicit symmetry breaking decays

1% tuning of a0 mass

Finding the Higgs if 2m! ! ma0 ! 2mb

Dominant decay mode is h0 ! (!+!!)(!+!!)

Br(!!) !h!h !h" ""

!h!h 17.6% 38.0% 10.4%!h" 20.4% 11.2%"" 1.5%

Table 1: The decay branching ratios of four ! decays.

Triggers Used:

Dileptons:Electrons with pT > 4 GeV, # < 1, !Riso= 0.4Muons with pT > 4 GeV, # < 1

Single Leptons:Electron with pT > 8 GeV, # < 1, !Riso= 0.4Muon with pT > 8 GeV, # < 1.

A 5 GeV track with no tracks in a cone 0.17 ! !Riso ! 0.52.AND either a 8 GeV lepton separated from the seed track by !$ > 10!.

Table 2: Potentially useful triggers. The last trigger is modelled on a ! -trigger, where one ! decaysleptonically, and the other is a thin, isolated jet.

The Higgs production through gluon fusion is then given by

%(gg " h0) = (rhtt)2 %SM(gg " h0). (18)

In the R-axion limit of the NMSSM, chtt is with in a few percent of cSMhtt .

One channel with very little Standard Model background is the case where at least three ofthe final state ! ’s decay leptonically. Then we have a tri-lepton signature, a final state well knownfrom supersymmetry searches at the Tevatron[22]. As shown in that context, the Standard modelbackground can be made tiny (< 1 event/fb"1) with an appropriate set of cuts. There are tworelevant caveats. First, the three leptons will be somewhat softer than those expected from thetraditional supersymmetry signature. Since the Higgs mass is shared between the observed leptonsand several neutrinos, the leptons will have energies of roughly 10 GeV. Because of this, care mustbe taken to set hardness cuts appropriately, while avoiding the background from soft leptons comingfrom o"-shell photons.

Since these events contain a substantial number of neutrinos, it is impossible to reconstruct theHiggs boson mass. In fact, they should be marked by the presence of a rather substantial amountof missing energy. However, this is unlikely to be of much assistance in decreasing the background.One significant Standard Model background comes from di-boson production (Z0W± or &W±),which also has large missing energy from the neutrino in the W± decay.

Several triggers are listed in Table 2 that should be e"ective in selecting out the Higgs decayswe have enumerated. The last entry is a ! trigger that looks for a thin, isolated jet. This dedicated

7

!!

!

!

g

g

h0 a0

a0

A heterogenous decay mode!

35%!

!!

!!̄

!65%

!+!!

!!

!!!

E! !112

mh0

Only have hadron machines... make a lot, but difficult to see

3 GeV <! pT !<! 10 GeV

!!

g

g

h0

a0

a0

µµ

!(a0 ! µ+µ!)!(a0 ! !+!!)

=m2

µ

m2!

!1" (2m!/ma0)2

Large gluon fusion production cross sectionovercomes small branching fraction to muons

Br(a0 ! µ+µ!) = 0.4%Br(a0 ! !+!!) = 98%

For 7 GeV a0:

Using a Subdominant Decay ModeAlways have coupling to muons

Br(h0 ! (µµ)(!!)) " 0.8%

µ

µ!!

a0 a0

h0ET!

Geometry of Decays

Mass of a0 reconstructedMET pointing away from muonsHigh pT muonsHiggs mass reconstructable pT

>! 15 GeV

Enough striking characteristics to be very clean channel

4 5 6 7 8 9

0

5

10

15

20

25

Muon Invariant Mass !GeV"

Events

4 5 6 7 8 9

0

100

200

300

400

500

600

700

Muon Invariant Mass !GeV"

Events

Eve

nts

Eve

nts

Muon Invariant Mass (GeV)

Muon Invariant Mass (GeV)

Signal E!ciencySelection Criteria Relative Cumulative

Pre-Selection Criteria 26% 26%Jet veto 99% 26%

Muon iso & tracking ! 50% 13%Mµµ < 10 GeV 98% 13%pµµ

T > 40 GeV 76% 9.8%ET" > 30 GeV 29% 2.8%

"!(µ,ET" ) > 140! 73% 2.1%"R(µ, µ) >0.26 63% 1.8%

Clean up Cuts

*

*Removes muons from semileptonic hadron decays

fb/GeV TeV LHCDY+j 0.15 0.24

W+W! 0.03 0.08tt̄ 0.02 0.14bb̄ <! 0.001 ! 0.03

! + j 0.001 0.002µµ+!! " 0.001 <! 0.001J/" + j " 0.001 " 0.001Total 0.20 0.49

Continuum Backgrounds after cutsHave many ~20 mass bins

100 120 140 160 180 2000.2

0.5

1.0

2.0

5.0

10.0

Higgs Mass !GeV"

!Br!h"#

aa"

Higgs Mass (GeV)

TeV

!pro

d!

Br(

h0"

a0a0

)(p

b)

250500LEP

Exclusion

10 fb!1

5 fb!1

20 fb!1

Tevatron SensitivityGetting close to the necessary sensitivity

!S"/ sin 2!

100 120 140 160 180 2001

2

5

10

20

50

100

Higgs Mass !GeV"

!Br!h"#

aa"

Higgs Mass (GeV)

!pro

d!

Br(

h0"

a0a0

)(p

b)

250

500

750

1000

LHC

.5 fb!1

5 fb!1

LHC

.5 fb!1

5 fb!1

LEP

Exclusion

LHC Projected SensitivityAn early LHC Higgs search and will probe 1% BRs

!S"/ sin 2!

D0 Results

4 events in relevant mass window

Drell-Yan + Jet peaked at lower invariant mass

0.2 fbGeV

! 6.5 GeV! 3.7 fb!1 = 4.4 Events

Having additional Higgs decay modes is “generic”

Could alter Higgs discovery even if mh0 >! 114 GeV

Some model-independent tension with“hiding the Higgs” with 4 tau decay mode

2 mu 2 tau decay mode is better than 4 tau

Could lead to early discovery at LHC,even if mode is not the dominant decay mode

Summary