Left-Right Symmetry and the Charged Higgs Bosons … Left-Right Symmetry and the Charged Higgs...

1

Left-Right Symmetry and the Charged HiggsBosons at the LHC

Gulab BambhaniyaTheoretical Physics Division

Physical Research Laboratory, Ahmedabad

December 10, 2014

XXI DAE-BRNS High Energy Physics Symposium 2014

Based on JHEP 1405, 033 (2014), in collaboration withJ. Chakrabortty, J. Gluza, M. Kordiaczyska and R. Szafron

Gulab Bambhaniya LR Symmetry and the Charged Higgs Bosons at LHC

2

Introduction

Standard Model:

Gauge Group

GSM = SU(3)c ⊗ SU(2)L ⊗ U(1)Y

SM Field Content

Fermions: [QL = (uL, dL)T , uR, dR, LL = (νL, eL)T , eR]× 3Gauge Bosons: γ,W±, Z, gluonsScalar : Φ = (φ+,φ0)T

The SM field content is not symmetric.

LR symmetry =⇒ Left and Right handed fields should betreated in symmetric way.


3

Motivations for LR symmetric models

They explain parity violation through spontaneousbreaking of Left-Right symmetry

Naturally neutrino mass in the theory via seesawmechanism

In the SM, hypercharge (Y) is ad-hoc, while in LRsymmetric model it emerges from physical quantumnumbers: lepton and baryon numbers


4

Start: 1973-1974,Pati, Salam, Senjanovic, Mohapatra

Gauge group: SU(2)L ⊗ SU(2)R ⊗ U(1)B−L

This gauge group can be embedded in SO(10) GUT group.

(i) Restores left-right symmetry to e-w interactions

!

νLeL

"

,

!

νReR

"

,

!

uL

dL

"

,

!

uR

dR

"

(ii) Hypercharge in terms of baryon and lepton numbers

Q = T3L + T3R +B − L

2.

W±L ,W 0

L

W±R ,W 0

RB0

→W±

1 ,W±2

Z1, Z2

γ


5

Scalar sector and symmetry breaking in MLRSM

SU(2)L ⊗ SU(2)R ⊗ U(1)B−L# $% &

Y =T3R+B−L

2

!!

SU(2)L ⊗ U(1)Y# $% &

Q=T3L+Y

!!

U(1)Q

Triplet Scalars

∆L,R =

⎛

⎜

⎝

δ+L,R/√2 δ++

L,R

δ0L,R −δ+L,R/√2

⎞

⎟

⎠

: (3, 1, 2) & (1, 3, 2)

Higgs bi-doublet

Φ =

⎛

⎝

φ01 φ+

1

φ−2 φ0

2

⎞

⎠ : (2, 2, 0)

with vacuum expectation values allowed for the neutral particles:vL√2= ⟨δ0L⟩, new HE scale :

vR√2= ⟨δ0R⟩,

κ1√2= ⟨φ0

1⟩,κ2√2= ⟨φ0

2⟩, SM VEV scale :'

κ21 + κ2

2.


6

Potential of Minimal Left Right Symmetric

Model

LHiggs = −µ21Tr[Φ†Φ]− µ2

2(Tr[ΦΦ†] + Tr[Φ†Φ])− µ23(Tr[∆L∆

†L] + Tr[∆R∆†

R])

+λ1Tr[ΦΦ†]2 + λ2(Tr[ΦΦ†]2 + Tr[Φ†Φ]2) + λ3(Tr[ΦΦ†]Tr[Φ†Φ])

+λ4(Tr[ΦΦ†](Tr[ΦΦ†] + Tr[Φ†Φ]))

+ρ1(Tr[∆L∆†L]

2 + Tr[∆R∆†R]2)

+ρ2(Tr[∆L∆L]Tr[∆†L∆

†L] + Tr[∆R∆R]Tr[∆†

R∆†R])

+ρ3(Tr[∆L∆†L]Tr[∆R∆†

R]) + ρ4(Tr[∆L∆L]Tr[∆†R∆†

R] + Tr[∆R∆R]Tr[∆†L∆

†L])

+α1(Tr[ΦΦ†](Tr[∆L∆†L] + Tr[∆R∆†

R]))

+α2(Tr[ΦΦ†]Tr[∆R∆†R] + Tr[ΦΦ†]Tr[∆L∆

†L]))

+α∗2(Tr[Φ†Φ]Tr[∆R∆†

R] + Tr[Φ†Φ]Tr[∆L∆†L]))

+α3(Tr[ΦΦ†∆L∆†L] + Tr[Φ†Φ∆R∆†

R]) + β1(Tr[Φ∆RΦ†∆†L] + Tr[Φ†∆LΦ∆†

R])

+β2(Tr[Φ∆RΦ†∆†L] + Tr[Φ†∆LΦ∆†

R]) + β3(Tr[Φ∆RΦ†∆†L] + Tr[Φ†∆LΦ∆†

R]),

invariant under the symmetry ∆L ↔ ∆R, Φ ↔ Φ†, βi = 0.Deshpande, Gunion, Kayser, Olness, 1991


7

After Symmetry breaking

Physical scalars are

4 neutral scalars: H00 , H

01 , H

02 , H

03 ,

(the first can be considered to be the light Higgs of the SM),

2 neutral pseudo-scalars: A01, A

02,

2 singly-charged scalars: H±1 , H±

2 ,

2 doubly-charged scalars: H±±1 , H±±

2 .


8

Strategy

Already now MW2> 2.8 TeV, it means vR > 5 TeV, for such a high

scale most of effects connected with heavy gauge bosons decouples.

We choose conservatively:

vR = 8 TeV (MW2≥ 3.5 TeV, expected limit in the next LHC

run)

masses of neutral Higgs particles ≃ 15 TeV (to suppress FCNC)

charged Higgs particles with masses testable by LHC

In such a scenario there is a chance to pin down charged Higgs bosonsignals


9

Strategy (contd..)

124.7 GeV < MH00< 126.2 GeV

µ1, µ2, µ3, ρ1, ρ2, ρ3, ρ4,α1,α2,α3, λ1,λ2,λ3,λ4

Minimization conditions are used to get values of dimensionfulmass parameters µ1, µ2 and µ3 which can be arbitrarily large, allother parameters are considered as free, but limited to theperturbative limit.


10

Mass relations

M2H0

1≃

1

2α3v

2R,

M2A0

1≃

1

2α3v

2R − 2κ2

+ (2λ2 − λ3) ,

M2

H±1

≃1

2v2R (ρ3 − 2ρ1) +

1

4α3κ

21, M2

H±2

≃1

2α3

(

v2R +1

2κ21

)

,

M2

H±±1

≃1

2

*

v2R (ρ3 − 2ρ1) + α3κ21

+

, M2

H±±2

≃ 2ρ2v2R +

1

2α3κ

21.

MH01,MA0

1are large to suppress FCNC =⇒ MH±

2is also large

But other charged scalars (MH±±1

,MH±±2

and MH±1) can be light


11

Neutral - charged Higgs mass splitting

Neutral Single Charged Double Charged

0 5 10 15 20100

500

1000

5000

1! 104

M!GeV"

Neutral Single Charged Double Charged

5000 10000 15000 20000

0.2

0.4

0.6

0.8

1.0

One example of mass spectra for charged scalar is

MH±±1

= 483 GeV, MH±±2

= 527 GeV, MH±1

= 355 GeV, MH±2

=15066 GeV.


12

MLRSM processes at the LHC

Primary production Secondary production Signal

I. H+1

H−1

ℓ+ℓ−νLνL ℓ+ℓ− ⊕ MET

– ℓ+ℓ−NRNR depends on NR decay modes

– ℓ+ℓ−νLNR depends on NR decay modes

II. H+2

H−2

ℓ+ℓ−νLνL ℓ+ℓ− ⊕ MET

– ℓ+ℓ−NRNR depends on NR decay modes

– ℓ+ℓ−νLNR depends on NR decay modes

III. H++1

H−−1

– ℓ+ℓ+ℓ−ℓ−

– H+1

H+1

H−1

H−1

See I

– H±1

H±1

H∓2

H∓2

See I & II

– H+2

H+2

H−2

H−2

See II

– W+i

W+i

W−j

W−j

depends on W ’s decay modes

IV. H++2

H−−2

– ℓ+ℓ+ℓ−ℓ−

– H+2

H+2

H−2

H−2

See II

– H±1

H±1

H∓2

H∓2

See I & II

– H+1

H+1

H−1

H−1

See I

– W+i

W+i

W−j

W−j

depends on W ’s decay modes

V. H±±1

H∓1

– ℓ±ℓ±ℓ∓νL

VI. H±±2

H∓2

– ℓ±ℓ±ℓ∓νL

VII. H±1

Zi, H±1

Wi – See I & Zi,Wi decay modes

VIII. H±2

Zi, H±2

Wi – See II & Zi,Wi decay modes

IX. H±1

γ – See I

X. H±2

γ – See II


13

Signal Processes

pp → (H++

1/2H−−1/2 ) → ℓi

+ℓi+ℓj

−ℓj− and

pp → (H±±1/2H

∓1/2) → ℓi

±ℓi±ℓj

∓νℓ

q

q

H++1/2

H−−1/2

ℓ+

ℓ+

ℓ−

ℓ−

q

q′

H±±1/2

H∓1/2

ℓ±

ℓ±

ℓ∓

νℓ

So final signals are: 4ℓ and 3ℓ+MET


14

Significance of signals over background

We have estimated the SM backgrounds for both the signals atLHC14TeV

4ℓ signal has better significance than 3ℓ+MET signal

MLRSM can be probed up to 600 GeV in 4ℓ channel atLHC14TeV with 300 fb−1 integrated luminosity.


15

Conclusion

We discussed charged Higgs boson sector within classicalMLRSM.

Though different low energy data and the LHC exclusion plotsconstrain already W2 and Z2 very much, still the charged scalarscan be relatively light.

We have chosen the benchmark points in such a way that signalsconnected with doubly charged scalars can dominate overnon-standard signals coming from both heavy gauge and neutralHiggs bosons.

If planed integrated luminosity in the next LHC run at√s = 14

TeV is about 10 times larger than present values, clear signalswith four-leptons and tri-lepton signals can be detected.


16

Conclusion (contd..)

These multi lepton final states posses very small SM background.We have shown that MLRSM model can give such signals fordoubly charged masses up to approximately 600 GeV.


17

THANK YOU


18

Background estimation

processes 3ℓ (fb) 4ℓ (fb)tt 18.973 –tt(Z/γ⋆) 1.103 0.0816ttW± 0.639 –W±(Z/γ⋆) 10.832 –(Z/γ⋆)(Z/γ⋆) 1.175 0.0362

TOTAL 32.722 0.1178

Table: Dominant Standard Model background contributions (in fb)for tri- and four-lepton signals at the LHC with

√s = 14 TeV after

obeying suitable selection criteria. While computing the SMcontributions to 4ℓ final state, no missing pT cut has been applied.


19

Backup Slides


20

Mass relations considering κ2 = 0

M2H0

0≃ 2κ2

1λ1,

M2H0

1≃

1

2α3v

2R,

M2H0

2≃ 2ρ1v

2R, M2

H03≃

1

2v2R (ρ3 − 2ρ1) ,

M2A0

1≃

1

2α3v

2R − 2κ2

+ (2λ2 − λ3) ,

M2A0

2≃

1

2v2R (ρ3 − 2ρ1) ,

M2

H±1

≃1

2v2R (ρ3 − 2ρ1) +

1

4α3κ

21, M2

H±2

≃1

2α3

(

v2R +1

2κ21

)

,

M2

H±±1

≃1

2

*

v2R (ρ3 − 2ρ1) + α3κ21

+

, M2

H±±2

≃ 2ρ2v2R +

1

2α3κ

21.


21

Relations among physical and unphysical fields

Here “G” stands for Goldstone modes.

φ01 ≃

1√2

,

H00 + iG0

1

-

,

φ02 ≃

1√2

*

H01 − iA0

1

+

,

δ0R =1√2

.

H02 + iG0

2

/

, δ0L =1√2

.

H03 + iA0

2

/

,

δ+L = H+1 , δ+R ≃ G+

R,

φ+1 ≃ H+

2 , φ+2 ≃ G+

L ,

δ±±R = H±±

1 , δ±±L = H±±

2 .


22

FCNC constraint on neutral heavy Higgs masses

FCNC effects appear through the A0 part of the following Lagrangian

Lquark−Higgs(u, d) = − U*

PL

.

MudiagB

∗0 + UCKMMd

diagUCKM†A0

/

+ PR

.

MudiagB0 + UCKMMd

diagUCKM†A∗

0

/+

U,

where

B0 =

√2φ0

1

k1=

1

k1

0

H00 + iG0

1

1

,

A0 =

√2φ0

2

k1=

1

k1

.

H01 − iA0

1

/

.

To suppress the effects connected with these fields, their masses needsto be at least ∼ 10 TeV. In our analysis we have kept them to be ∼15 TeV:

MH01, MA0

1> 15 TeV.


Date post:	07-May-2018
Category:	Documents
Upload:	buikiet
View:	220 times
Download:	3 times

Left-Right Symmetry and the Charged Higgs Bosons … Left-Right Symmetry and the Charged Higgs...

Documents