Searching for neutral Higgs bosons in non-standard channels

Searching for neutral Higgs bosons innon-standard channels

Arjun MenonUniversity of Oregon

April 9, 2013

Searching for neutral Higgs bosons in non-standard channels Arjun Menon University of Oregon

Motivation

• A SM-Higgs like resonance has been observed at the LHC• The Higgs sector may also have extra scalars and

pseudo-scalars.• The ττ -channel is the standard mode of searching for such

particles.• Examples of models with suppressed A/H → ττ rates:

• Enhanced bb couplings in 2HDM and MSSM.JHEP 1207 (2012) 091 w/ M. Carena, S. Gori, A. Juste, C.

Wagner & L-T. Wang• Enhance ZA couplings in NMSSM like models.

JHEP 1302 (2013) 152 w/ S. Chang


Searching Non-Standard Higgses with enhanced bb rates


Higgs Sector in 2HDMs

• The Neutral components acquire vevs and their ratio istanβ = vu/vd .

• Neglecting CP violation in the Higgs sector, electroweakbreaking leaves:

1 CP odd Higgs A1 charged Higgs H±, and2 CP even Higgs bosons h, H

• One CP-even (SM-like) Higgs has SM strength couplingsto gauge bosons.

• The other CP-even (Non-Standard) Higgs has suppressedcouplings to gauge bosons.


Couplings to b-quarks and τ -leptons in 2HDMs• General 2HDM Higgs fermions couplings are

LYuk = yu HuQU + yd Hd QD + yu H†d QU

+ yd H†uQD + y` Hd LE + y` H†u LE + h.c.

• d-type fermion couplings to Non-standard Higgses are:

gH/Af f 'mf

vtanβf

eff

where for f = b, τ

tanβfeff =

tanβ1 + εf tanβ

(1− εf

tanβ

)εf =

yf

yf


Fermion couplings in the MSSM• Including 1-loop effects, both quarks couple to both the

Higgs bosons so that:

−Leff = d0RYd[Φ0∗

d + Φ∗0u

(ε0 + εYY†uYu

)]d0

L + h.c.2

Φ02

*

dy

d~

RdL~

dL g~

g~ dR dL h

~1−

h2~ −

dR

yu

yd

uR~

yu

+

u~

L

Φ0 *

and have the structure:

εI0 ≈2αs

3πM3µC0(m2

d I1,m2

d I2,M2

3 )

εY ≈1

16π2 AtµC0(m2t1,m2

t2, µ2)

ετ ≈3α2

8πµM2C0(M2

τ1,M2

τ2,M2

1 )

Kolda, Babu, Buras, Roszkowski...


Non-standard Higgs boson production and decay

b

A

b

b

g

g

A

g

g

b

Gunion et.al. ’94, Balazs et.al, Diaz-Cruz et.al., & Huang et.al. ’98,Campbell et.al. ’03, Dawson et.al. ’03

• General b and τ couplings are

gAbb 'mb tanβb

eff

v; gAττ '

mτ tanβτeff

v


contd...• Enhanced production and decay modes:

σ(bb → A)

σ(bbh)SMBR(A → bb) ∝

9(tan βbeff)

4

(tan βτeff)

2 + 9(tan βbeff)

2,

σ(gg, bb → A)

σ(gg, bb → h)SMBR(A → ττ) ∝

(tan βτeff)

2(tan βbeff)

2

(tan βτeff)

2 + 9(tan βbeff)

2,

• In the MSSM the bb channel has greater modeldependence than ττ . Carena et.al. ’05


Non-Standard Higgs into 3b: Production and Decay

• tanβτeff can be small compared to tanβbeff ⇒ weaker reach

in the ττ channel.• The H/A→ bb can be enhanced enough to make it

competitive with the clean ττ channel.• In addition to the 4b-final state we also have:

H/A

g

b

b

• 3b channel can be important at 14 TeV LHC for mSUGRACao et.al. ’09, Baer et. al. ’11


Signal and Background Simulation

• Simulation used MG5 interfaced with Pythia 6.4.• QCD background: Separately simulated the 3b+X and

2b+j+X where X= 1,2j• Used kt matching, with matching scale of 30 GeV.• Background separation into bbj and 3b samples does not

model b jets with pT below ∼ 40 GeV very well.• b-jets are clustered using anti-kT with ∆R = 0.4.• Jet energy smearing of 100%/

√E/GeV.

• We assume a constant b-tagging efficiency of 60%, a c-jetmis-tag rate of 10% and a light-jet mis-tag rate of 1%.

• Low mis-tag rate of c- and light-jets leads to the bbj and 3bbackgrounds being comparable


Selection I vs Selection II• Selection I: Exactly 3 b-tagged jets with pT > 60 GeV and|η| < 2.0.

• Selection II: Exactly 3 b-tagged jets with pb1T > 130 GeV,

pb2,3T > 50 GeV and |η| < 2.0.

• Require M12,M13 or M23 within 25 GeV window of Higgsmass.

For tanβbeff = 30 @ 30 fb−1 7 TeV LHC

Selection I Selection IIS/B S/

√B S/B S/

√B

mA = 150 GeV 0.06 14.1 0.047 6.2mA = 200 GeV 0.057 14.4 0.048 7.9mA = 300 GeV 0.035 7.3 0.038 6.8mA = 400 GeV 0.027 3.4 0.028 3.3


Signal and Background Distributions for tan β = 30


Reach in the general 2HDM Model


The 3b vs ττ in the MSSM


CMS Analysis

]2 [GeV/cAm100 150 200 250 300 350

βta

n

0

10

20

30

40

50

60

70 = 7 TeVs -1CMS preliminary 2.7-4.8 fb

obsexp (68%)exp (95%)exp (semi-leptonic)exp (all-hadronic)

-maxhMSSM m

= +200 GeVµ

]2 [GeV/cAm100 150 200 250 300 350

βta

n0

10

20

30

40

50

60

70 = 7 TeVs -1CMS preliminary 2.7-4.8 fb

obsexp (68%)exp (95%)exp (semi-leptonic)exp (all-hadronic)

-maxhMSSM m

= -200 GeVµ

HCP Nov. 2012


Conclusions

• The A→ ττ LHC search puts weak limits on regions oflarge tanβb

eff and small tanβτeff in 2HDMs.• The A/H → bb is a complementary channel that probes

parametric scenarios of large tanβbeff.

• The reach of the A/H → bb channel is limited by low S/Bfor low to moderate tanβb

eff, but can be powerful at largetanβb

eff.


Search for Non-Standard Higgs in the H → ZA channel


Motivation: excess in the 2`+ 0 ,1 and 2 τh’s

• CMS 2011: 2.1 fb−1 @ 7 TeV CMS-PAS-SUS-11-013

• CMS 2012: 4.8 fb−1 @ 7 TeV arXiv:1204.5341


Theoretical Implications of Signal

• The multi-lepton channel is sensitive to SM Higgs decaymodes and with 5 fb−1 of data, the region120 ≤ mh ≤ 150 GeV can be probed at 95% C.L.

E. Contreras-Compana, et.al. ’12

• The CMS 2012 multi-lepton data puts limits onBR(t → ch) < 2.7%

N. Craig et.al. ’12

• It also leads to constraints on 2HDM’s whenmultiple-channels from h,H,A and H± decay modes.

N. Craig et.al. ’13


Example: The NMSSM• The superpotential has the form

W = WYuk + λHuHd S +κ

3S3

with soft terms

Vsoft = m2Hu|Hu|2 + m2

Hd|Hd |2 + m2

S|S|2 +√

2(

mλSHuHd −mκ

3S3)

with mκ ≡ −κAκ/√

2 and mλ ≡ λAλ/√

2• In the basis where scalar basis (h0

v ,H0v ,h0

s) and thepseudo-scalar basis (A0

v ,A0s)

LKinHiggs ⊂ − g2

2cθW

Zµ(cθAA01 − sθAA0

2)←→∂µ

(s2βh0

v + c2βH0v

)where the hv is direction that acquires a VEV.

• H → Zτ+τ− Has been studied in context of explaining LEPanomalies.

Dermisek ’08, Dermisek and Gunion ’09Searching for neutral Higgs bosons in non-standard channels Arjun Menon University of Oregon

Higgs mass of Benchmark points

Model λ κ tβ Aλ Aκ At µeff Mq(GeV) (GeV) (TeV) (GeV) (TeV)

BM1 0.71 1.10 1.5 -11.0 -8.0 0.0 160 0.5BM2 0.71 1.10 1.5 -9.1 -7.0 0.0 166 0.5BM3 0.67 0.78 1.5 -4.2 -40.6 0.0 170 0.5

Model mH01

mH02

mA01

mH± gred.t tH0

1gred.

t tH02

(GeV) (GeV) (GeV) (GeV)BM1 125.2 270 8.9 266 0.982 -0.691BM2 125.1 283 19.7 278 0.984 -0.690BM3 124.5 252 117 248 0.992 -0.668


Higgs couplings of Benchmark pointsBR of H0

1 bb γγ WW ∗ ZZ ∗ A01A0

1BM1 0.63 2.6× 10−3 0.19 2.1× 10−2 2.9× 10−3

BM2 0.61 2.5× 10−3 0.18 2.0× 10−2 4.3× 10−2

BM3 0.64 2.7× 10−3 0.18 2.0× 10−2 0.0

BR : γγSM = 2.28×10−3; WW ∗SM = 2.15×10−1; ZZ ∗SM = 2.64×10−2

BR of H02 bb H0

1 H01 ZA0

1 A01A0

1BM1 4.5× 10−3 5.6× 10−4 0.78 0.17BM2 4.3× 10−3 4.9× 10−4 0.70 0.16BM3 1.9× 10−2 1.7× 10−6 0.78 0.19

BR of A01 ττ bb gg Signal Rate (µ)

BM1 0.74 0.0 0.12 0.28BM2 5.9× 10−2 0.92 1.1× 10−2 5.7× 10−3

BM3 9.1× 10−2 0.87 2.9× 10−2 0.01


Event Simulation

• Simulation used Pythia8.170 for pp collisions.• Include the effects of ISR, FSR, multiple interactions and

fragmentation.• The Z-bosons were allowed to decay only into e, µ, τ .• No detector simulator was used, but instead implemented

an CMS-like τh reconstruction algorithm.• Trigger requirements:

• 1-lepton: muon (electron) has a pT > 35 (85) GeV• 2-lepton: p1

T ≥ 20 GeV and p2T ≥ 10 GeV.

• Lepton identification: pT ≥ 8 GeV and |η| ≤ 2.1.• Lepton isolation: IRel = Econe/E` ≤ 0.15, where

E` = energy of lepton andEcone = energy in a ∆R = 0.3 (0.4) for muons (electrons).


τh reconstruction• τh reconstruction: 1-pronged track with pT ≥ 8.0 GeV.• τh isolation: Eann/Econe ≤ 0.15 where,

Eann = energy in 0.1 < ∆R ≤ 0.3Econe = energy in ∆R ≤ 0.1.

0.4 ArcTan@HpT-8L�20D

0 20 40 60 800.0

0.2

0.4

0.6

0.8

1.0

Generated Τ pT HGeVL

Τh Reconstruction Efficiency in Z®ΤΤ events


Z ττ efficiency in

7 ´ 10-3

5 ´ 10-3

3 ´ 10-3

1 ´ 10-3

160 180 200 220 240 260 280 300

20

40

60

80

100

mH HGeVL

mA

HGeV

L

Efficiency Ε: 0 Τh Channel

3 ´ 10-2

2 ´ 10-2

1 ´ 10-2

5 ´ 10-3

160 180 200 220 240 260 280 300

20

40

60

80

100

mH HGeVL

mA

HGeV

L


3.5 ´ 10-2

2.5 ´ 10-2

1.5 ´ 10-2

5 ´ 10-3

160 180 200 220 240 260 280 300

20

40

60

80

100

mH HGeVL

mA

HGeV

L


ε =Number of events to pass cutsNumber of events generated


Toy-Model for τh reconstruction

mH = 200 GeV and mA = 10 GeV

pT Cut

Π+Π-

-1.0 -0.5 0.0 0.5 1.00

10

20

30

40

Cos ΘCM

p THG

eVL

Charged Pion pT

Isolation Annulus

-1.0 -0.5 0.0 0.5 1.00.0

0.2

0.4

0.6

0.8

1.0

Cos ΘCM

Charged Track DR

θCM = Angle of π+ in rest frame of A when τ+ → π+ντpT is measured in the H rest frame

∆R = the angle between the two charged tracks.


Limits of signal due to CMS data• Due to low statistics we assume a Poisson distribution for

the number of events.• We assume the background errors are gaussian• The maximum allowed number of signal events at 95%

C.L. (SMax95 ) is found by solving∫ ∞

0dB

Γ(Nobs + 1,SMax95 + B)

Nobs!

1NB

exp

[−(B − µB)2

2σ2B

]= 0.05

• The bounds on σsig, normalized to σSM is

µi95 ≡

Si Max95

σHSM × BR(Z → l+l−)× εi × L


contd.

0.25

0.5

0.75 1

160 180 200 220 240 260 280 300

20

40

60

80

100

mHHGeVL

mA

HGeV

L95% CL Limit Μ95

0.05

0.08

0.15

0.25

160 180 200 220 240 260 280 300

20

40

60

80

100

mHHGeVLm

AHG

eVL

30 fb-1 Projected 95% CL Limit Μ95

7 TeV 8 TeV

1-τh constraint is the strongest due to large ε1τh andNCMS

obs ∼ Nbkg


H and A Mass reconstruction in the 2τh channel• Transverse Mass:

mTA =

√p2

V + 2(EV ET+ − pT

V · pT+)

mTH =

√(pV + pZ )2 + 2((EV + EZ )ET

+ − (pTV + pT

Z ) · pT+)

where mTi ≤ mi

Barr et. al., 2009• Collinear Mass: Solve kinematics under assumption that

neutrinos are collinear with the visible momenta

λ1 pTV1

+ λ2 pTV2

= pT+.

where by assumption λi ’s are positive.Ellis et. al., 1987


H and A Trial Mass Reconstruction in the 2τh channel• The 8 kinematic constraint equations are:

p2ν1

= 0 = p2ν2(

pν1 + pV1

)2= m2

τ =(pν2 + pV2

)2

m2A =

(pν1 + pV1 + pν2 + pV2

)2

m2H =

(pZ + pν1 + pV1 + pν2 + pV2

)2

pxν1

+ pxν2

= px+

pyν1

+ pyν2

= py+

• However 10 unknowns pνi ,mH and mA.• Solve for the mean values of mH and mA where solutions

exist.


Comparison of Mass reconstructions

180 190 200 210 2200

50100150200250300350

mH HGeVL

Eve

nts�G

eV

Mass Variables: HmH , mAL= H200, 10L GeV

6 8 10 12 14 16 18 200

200

400

600

800

1000

1200

mAHGeVL

Eve

nts�G

eV


260 280 300 320 3400

200

400

600

800

mH HGeVL

Eve

nts�G

eV


80 90 100 110 1200

1000

2000

3000

4000

mAHGeVL

Eve

nts�G

eV



Latest CMS analysis

CMS-PAS-SUS-12-026

But visible pτT ≥ 20 GeV⇒ reduced efficiencies.


Conclusion

• The possibility of enhanced H → ZA→ Zτ+τ− decayexists.

• The NMSSM example scenario needs low tanβ and largepseudo-scalar mixing.

• The efficiencies for detecting such a scenario are thelargest in the 1τh and 2τh channel.

• The shape of the efficiency curves is due to an interplaybetween the isolation and min(pT ) cuts.

• For low mA a boosted τ strategy similar to Englert et. al.,’11 may be needed.


contd...

• 1-τh is the most constraining of the channels.• The projected reach with 30 fb−1 CMS data could probe a

large region interesting parameter space.• For such decays the trial mass reconstruction method is

more efficent than the transverse and collinearapproaches.

• The phenomenology of non-Standard Higgs bosons canbe quite rich and appear in many channels other than ττ .


Searching for neutral Higgs bosons in non-standard channels

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