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Probing super light neutral Higgs boson at the LHC in CP violating MSSM Higgs sector Dilip Kumar Ghosh Department of Theoretical Physics Indian Association for the Cultivation of Science 2A & 2B Raja S.C. Mullick Road, Kolkata, India

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Probing super light neutral Higgs boson at the LHC in CP violating MSSM Higgs sector

Dilip Kumar Ghosh Department of Theoretical Physics Indian Association for the Cultivation of Science 2A & 2B Raja S.C. Mullick Road, Kolkata, India Tohoku University,Sendai, Japan 1-2 September, 2010

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Plan

  • CP violating (

CP) MSSM Higgs sector

  • General feature of the phenomenology of the CP violating (

CP) MSSM Higgs sector

  • Study of ultra light Higgs boson (mH ≤ 60 GeV) at LHC in Four possible

scenarios

  • Summary

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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SLIDE 3

CP violation in Higgs sector

  • CP violation arises naturally in the three generation SM (Phase in the CKM

matrix)

  • The CP violation has been first measured in neutral K-meson decays.

[J. H. Christenson, J. W. Cronin, V. L. Fitch, and R. Turlay , Phys. Rev. Lett.13, 138 (1964)]

  • CP non-conservation provides a key ingredient for cosmological baryogenesis
  • It is possible to have CP violation in Multi-Higgs models
  • MSSM contains an extended Higgs sector : may realize CP violation

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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General frame work

  • Higgs potential of the MSSM is invariant under CP at the tree level
  • Two CP-even neutral Higgs bosons :h0, H0 (MH0 > Mh0)
  • One CP-odd neutral Higgs boson :A0
  • One charged Higgs boson :H±
  • MA, tan β, µ and At,b control the MSSM Higgs spectrum
  • The tree level CP invariance of the MSSM Higgs potential may be violated

sizeably by loop effects involving soft CP-violating trilinear couplings At,b [ A.

Pilaftsis, PRD58,096010 (1998) and PLB435,88 (1998)]

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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CP violation in MSSM

  • After radiative corrections to the tree level Higgs potential:

CP violation induced through loop effects via 3 generation sfermion and gaugino mass parameters

  • From the one loop effective potential Higgs boson mass matrix is calculated

[J.Ellis et al’90, Y.Okada et al ’90, E.Haber et al’90,..M.Carena et al’95...A.Demir’99, A.Pilaftsis et al’99... S.Y.Choi et al’99] M 2

N =

M 2

S

M 2

SP

M 2

P S

M 2

P

!

  • M 2

S, M 2 P and M 2 SP denote the 2 × 2 matrices of the scalar, pseudoscalar and

scalar-pseudoscalar squared mass terms of the neutral Higgs bosons. M 2

P S ≃ O

m4

t

v2 |µ||At| 32π2M 2

S

  • sin φCP
  • 1, |At|2

M 2

S

, |µ|2 tan βM 2

S

, |µ||At| M 2

S

  • MS is stop mass average, φCP = Arg(At,µ)

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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CP violation in MSSM Higgs sector

  • In CP conserving MSSM: MSP = 0: 2 CP-even h, H and one CP-odd A.
  • Diag(M 2

H1, M 2 H2, M 2 H3) = OTM 2 NO , with MH1 < MH2 < MH3

  • After diagonalization the Physical mass eigenstates are mixed states of CP,

H1,2,3 have undefined CP properties.

  • To get sizeable CP violation, large | µ |, | At,b | and large sin φCP

are needed

  • mA no longer a physical parameter, but the mH± can be used as a physical

parameter

  • Elements of matrix O are similar to cos α and sin α in the CP-conserving case.

But 3rd row and column are zero in the non-diagonal elements in such a case

  • Large mH± implies H1 → Hsm

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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The interaction between Higgs and gauge bosons

LHiV V = gmW

3

  • i=1

gHiV V [HiW +

µ W −,µ +

1 2c2

W

HiZµZµ] LHiHjZ = g 2cW

3

  • j>i=1

gHiHjZ (Hi

↔

∂µ Hj)Zµ LHH∓W ± = g 2cW

3

  • i=1

gHiH−W + (Hi

↔

∂µ H−)W +,µ gHiV V = O1i cos β + O2i sin β, gHiHjZ = O3i(cos βO2j − sin βO1j) − (i ↔ j) gHiH+W − = O2i cos β − O1i sin β + iO3i gHkV V = ǫijkgHiHjZ

  • We have the following Sum rules: 3

X

i=1

g2

HiV V = 1,

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Implications of CP violating phases on Higgs searches

The CPX Scenario (Carena, Ellis, Pilaftsis & Wagner, PLB495(2000) 155)

  • Designed to showcase the effects of CP violation in the MSSM Higgs sector

M˜

t = M˜ b = M˜ τ = MSUSY

µ = 4MSUSY, | At,b,τ |= 2MSUSY, | M˜

g |= 1TeV

  • Allows the following parameters to vary:

tan β, MH±, MSUSY ΦAt, ΦAb, ΦAτ, Φ˜

g, Φµ

  • The spectrum is generated by CPSUPERH code

[J. S. Lee etal, Comput.Phys.Commun. 156,283(2004), hep-ph/0307377] Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Implications of CP violating phases on Higgs searches

10

  • 2

10

  • 1

1 20 40 60 80 100 120 arg (At) = arg (Ab) [ deg ] MH1, MH2 [ GeV ]

CPX scenario

(a) MSUSY = 0.5 TeV arg (At) = arg (Ab) [ deg ] g2

H1ZZ

, g2

H2ZZ

, g2

H3ZZ

g2

H3ZZ

g2

H3ZZ

g2

H2ZZ

g2

H1ZZ

(b) 40 50 60 70 80 90 100 110 120 130 140 20 40 60 80 100 120

  • (a) MH1, MH2 and (b) g2

HiZZ as functions of

Arg(At), in the CPX scenario for MSUSY = 1 TeV and for the following choices

  • f

(MH±, tan β): (160 GeV, 4)(solid lines), (150 GeV, 5) (dashed lines) and (140 GeV, 6) (dotted lines)

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Implications of CP violating phases on Higgs searches

  • In CPC MSSM, we have access only two neutral Higgses h, H in Higgsstrahlung

/WW fusion process

  • In CPV MSSM, the three neutral Higgs mass eigenstates Hi (i=1,2,3) do not

have well defined CP quantum numbers.

  • Each of them can be produced in the Higgs-Strahlung process: (e+e− → ZHi)

and/or in the WW fusion (e+e− → Hiνe ¯ νe)

  • Also in pair (e+e− → HiHj(i = j))
  • The relative rates depend of the choice of the parameters describing the

CP-odd/even mising. [A.Akeroyd & A. Arhrib, PRD64,095018 (2001)]

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Higgs production in CP violating MSSM

  • We studied WHi and ZHi, (i = 1, 2, 3) pair production at Tevatron (p¯

p) Run II and LHC (pp) Collider.

[Arhrib,Ghosh & Kong,PLB’2002]

  • Our parameters are fixed as:

Set A:

  • MQ =

Mt = Mb = 1TeV, |µ| = 4TeV, |At| = |Ab| = 2TeV, Arg(At) = Arg(Ab), tan β = 6 Set B:

  • MQ =

Mt = Mb = 0.5TeV, |µ| = 2TeV, |At| = |Ab| = 2TeV, Arg(At) = Arg(Ab), tan β = 15

  • Interested in MH± <

∼ 300 GeV MH± > 300 is the decoupling scenario and H1 is SM like V V H1 = 1, V V H2 = V V H3 = 0

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Higgs production in CP violating MSSM

50 70 90 110 130 150

Higgs Mass (GeV) H1 H2 H3 (a)

100 120 140 160 180 200

H1 H2 H3 (d)

1e-06 0.0001 0.01 1

σ(pb) ZH1 ZH2 ZH3 (b) ZH1 ZH2 ZH3 (e)

1e-06 0.0001 0.01 1 20 40 60 80 100 120 140 160 180

σ (pb)

Φ

CP (degree)

WH1 WH2 WH3 (c)

20 40 60 80 100 120 140 160 180

Φ

CP (degree)

WH1 WH2 WH3 (f)

  • Tevatron Run II energy.

MH± = 150(left pannel) and 200 GeV (right pannel). Other MSSM parameters correspond to set A.

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Higgs production in CP violating MSSM

50 70 90 110 130 150

Higgs Mass (GeV) H1 H2 H3 (a)

100 120 140 160 180 200

H1 H2 H3 (d)

1e-06 0.0001 0.01 1 10

σ (pb) ZH1 ZH2 ZH3 (b) ZH1 ZH2 ZH3 (e)

1e-06 0.0001 0.01 1 10 20 40 60 80 100 120 140 160 180

σ (pb)

Φ

CP (degree)

WH1 WH2 WH3 (c)

20 40 60 80 100 120 140 160 180

Φ

CP (degree)

WH1 WH2 WH3 (f)

  • LHC energy. MH± = 150(left pannel) and

200 GeV (right pannel). Other MSSM parameters correspond to set A.

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Higgs search in CP violating MSSM Higgs sector

MH1 (GeV) tanβ LEP(95)/TeV(3σ)/LHC(5σ) for CPX0.5

2 5 10 20 30 40

900

2 5 10 20 30 40

600

2 5 10 20 30 40

300

2 5 10 20 30 40

00

20 40 60 80 100 120 20 40 60 80 100 120 20 40 60 80 100 120 20 40 60 80 100 120

  • M. Carena etal.

[NPB659,145 (2003)] looked for several channels for Higgs boson Hi searches at hadron colliders

  • 45◦ line: Tevatron: W/ZHi(→ b¯

b).

  • 135◦

line: LHC: gg → Hi → γγ( 100 fb−1), t¯ tHi(→ b¯ b)( 100 fb−1), W W/ZZHi(→ τ +τ −)( 100 fb−1).

  • dark grey → LEP exclusion.
  • Gaps at MH1 ≤ 50 GeV for 90◦ and 60◦

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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LEP-2 exclusion

1 10 20 40 60 80 100 120 140 1 10

mH1 (GeV/c

2)

tanβ

Excluded by LEP Theoretically Inaccessible

CPX (b)

  • Exclusions, at 95%CL(light-green) and the

99.7%CL(dark-green)

  • Two main channels LEP studied :

(a) e+e− → H1Z(H2Z) and (b) e+e− → H1H2

  • For low MH1, LEP looked at e+e−H1H2 →

H1(H1H1) → 6b jets,and 6τ leptons

[Eur.Phys.J.C47, 547 (2006)]

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Light Higgs window : Scenario I

  • LEP can not exclude the light Higgs mass in these two regions of parameter

space:

  • ΦCP = 90◦, tan β ∼ 4 − 5,

MH± ∼ 125 − 140 GeV, MH1

< ∼ 60 GeV

  • ΦCP = 60◦, tan β ∼ 2 − 3,

MH± ∼ 105 − 130GeV, MH1

< ∼ 40 GeV

  • Suppressed H1ZZ coupling and also the H1t¯

t.

  • Tevatron also can not probe this because of suppressed W/ZH1 coupling.
  • No hope at the LHC through t¯

tH1 and W/ZH1.

[with D. P. Roy and R. M. Godbole, PLB628,131(2005)] Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Light Higgs window : Scenario I

  • H1ZZ coupling is suppressed, H+W −H1 coupling remains large
  • Large H±WH1 coupling ⇒ large Br (H± → H1W ±)
  • Small tan β, light H±, (MH+ < Mt) ⇒ H± can be produced in the top decay.

tan β 3.6 5 Br(H+ → H1W +)(%) > 90(87.45) > 90(46.57) Br(t → bH+)(%) ∼ 0.7 1.0 – 1.3 MH+ (GeV) < 148.5 (149.9) < 126.2(134) MH1 (GeV) < 60.62 (63.56) < 29.78(53.49)

The BR (H± → H1W) > 0.47 over the entire kinematic region in the light H1 window still allowed by LEP. BR (H± → τντ) is suppressed by over an order of magnitude.

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Light Higgs window : Scenario I

pp →

✲

t b

✲

H+

✲

W ℓν(q¯ q)

✲

H1 b¯ b +

✲

¯ t ¯ b

✲

W q¯ q(ℓν) + X

  • Process allows a probe of a light H± and light neutral Higgs.
  • Use t¯

t production with: t → bH+ → bH1W → bb¯ bW and ¯ t → ¯ bW, with one W decaying leptonically the

  • ther hadronically.
  • Look for WWbbbb events, demand 3 or more tagged b’s.
  • The mass of the b¯

b pair with the smallest value will cluster around MH1 and b¯ bW around MH+

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Light Higgs window : Scenario I

As a basic selection criteria we require

  • | ηj,ℓ |< 2.5 :
  • pi

Tjets(i = 1, 2, 3) > 30 GeV

  • pT of all the other jets, lepton > 20 GeV,
  • ∆Rjj,ℓj > 0.4
  • Three or more tagged b-jets in the final state, ǫb = 0.5.
  • Signal cross-section varies between 20-150 fb for the range of light Higgs mass

20-50 GeV

  • The main SM background σ(pp → t¯

tb¯ b) ∼ 0.5 fb after all cuts

  • With 30 fb−1 data one expects upto ∼ 4500 events after all cuts

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Light Higgs window : Scenario I

1 2 3 4 5 6 7 8 9 10 50 100 150 200 d σ/dminv (fb/GeV) minv (GeV) ΦCP = 90o tan β = 5 MH1 = 51 (GeV) MH+ = 133 (GeV) Mt = 175 (GeV)

mbb

  • mbbW
  • mbbWb
  • (a)

(b)

m

b b

  • mbbW
  • Tohoku University, Sendai, Japan, 1-2 September, 2010

Dilip Kumar Ghosh

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Light Higgs window : Scenario II

  • Use the same fact that W ±H∓H1 coupling is enhanced
  • We look at pp → H± + H1 → (H1W ±) + (b¯

b) → (b¯ b)(ℓν) + (b¯ b)

  • Signal will be 4b + ℓ± with missing energy
  • Important feature : Two pairs of b-jets reconstruct at light Higgs mass
  • The signal cross-section is not large (production process is a weak interaction)
  • After all cuts σsignal can reach up to 1.6 fb for MH1 ∼ 45 GeV

[with S. Moretti, EPJC42,341 (2005)] Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Light Higgs window : Scenario II

  • Following SM backgrounds were generated using MADGRAPH :
  • We used same set of basic cuts as in Scenario I
  • (a)

σ(gg → b¯ bjjℓν) < ∼ 2.2 × 10−3 fb

  • (b)

σ(q¯ q′ → ZZW ± → b¯ bjjℓν) < ∼ 4.0 × 10−3 fb;

  • (c)

σ(gg → t¯ t → b¯ bjjℓν) < ∼ 2.9 × 10−2 fb

  • We have assumed the b-tagging efficiency ǫb = 0.5 (for each b-jet) and the

appropriate light-quark rejection factors (Ru,d,s = 1/50 and Rc = 1/25).

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Light Higgs window : Scenario II

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 50 100 150 200 dσ dmbb (GeV)-1 1 σ mbb (GeV)

  • EW background

(a) QCD background MH1= 54.34 (GeV) MH1= 32.41 (GeV) tt background

  • Tohoku University, Sendai, Japan, 1-2 September, 2010

Dilip Kumar Ghosh

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Light Higgs window : Scenario III

  • Use ˜

t1˜ t∗

1h1 coupling

  • σ(˜

t1˜ t∗

1h1) is large in CPV scenario, due to large value of At.

Large At = ⇒ lighter stop. In addition, both h2 and h3 also couple favorably to the t¯ t pair can add modestly to the signal

  • Typical masses (GeV) :mhi = (48.9, 103.3, 135.7); m˜

ti = (322, 664); m˜ χ0

1,2 =

(99.6, 198.4); m˜

χ±

1 = 198.4; m˜

g = 1000

  • Cross-sections(fb):

σ˜

t1˜ t∗

1h1 = 440; σ˜

t1˜ t∗

1h2 = 6; σ˜

t1˜ t∗

1h3 = 4; σt¯

th1 = 8; σt¯ th2 =

198; σt¯

th3 = 135; σ˜ g˜ g = 134

  • Typical Branching fractions: Br(˜

t1 → b˜ χ+

1 ) = 0.81; Br(˜

t1 → t˜ χ0

1) = 0.19; Br(h1 →

b¯ b) = 0.91; Br(h2 → h1h1) = 0.71; Br(h3 → h1h1) = 0.82; Br(˜ g → t˜ t∗

1) = 0.16 [P. Bandyopadhyay, PRD78, 015017 (2008)] Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Light Higgs window : Scenario III

  • They looked at pp → ˜

t1˜ t∗

1h1 and pp → t¯

th2,3

  • h1 and both top (stop) dominantly decay to b quarks
  • For the signal, the associate Ws (or ˜

χ±

1 ) produced in the decay of t (or ˜

t1) are required to decay leptonically

  • These decay lead to 4b + 2ℓ + missing pT final state
  • Low mh1 give rise to softer b-jet ( less than 40 GeV)
  • This forced them to look for 3 tagged b + 2ℓ + other untagged jets + missing pT
  • Backgrounds: Two sources : CPC MSSM, & SM
  • CPC MSSM : pp → ˜

g˜ g, pp → t¯ th

  • SM : pp → t¯

t, t¯ tZ, t¯ tb¯ b, t¯ th

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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Light Higgs window : Scenario III

  • Decisive cuts:
  • 1. Missing pT ≥ 110 GeV
  • 2. pjet

T

≤ 300 GeV

  • 3. Nj ≤ 5
  • Cut (1) remove mainly SM t¯

th

  • Cut (2) & (3) remove ther CPC (pp → ˜

g˜ g) and rest of the SM backgrounds

  • Assuming L = 30 fb−1, they expect S/

√ B ∼ 7

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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SLIDE 27

Light Higgs window : Scenario IV

  • Look for ˜

χ0

2 → ˜

χ0

1h1

  • Br(˜

χ0

2 → ˜

χ0

1h1) ∼ 0.79 and Br(˜

g → ˜ χ0

2q¯

q) ∼ 0.17 in the region where a light Higgs is unexcluded by the present data

  • Consider the SUSY cascade decay chain starting with a gluino:
  • ˜

g → ˜ χ0

2q¯

q → ˜ χ0

1h1q¯

q → ˜ χ0

1q¯

qb¯ b(τ +τ −)

  • σ˜

g˜ g ≈ 8.5 pb for M˜ g = 500 GeV

  • Around 13% gluinos produced in this scenario will decay into h1
  • More detailed analysis (even parton level) is required to establish their claims

[A.C. Fowler and G. Weiglein, arXiv:0909.5165] Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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SLIDE 28

Summary

  • CP violation in the MSSM Higgs sector can be generated at loop level leading

to very interesting phenomenology in the MSSM Higgs sector

  • LEP-2 still allows very light Higgs in the CP violating MSSM Higgs sector, due

to strong suppression of the H1ZZ coupling

  • No hope from Tevatron and LHC either through conventioanl channel:

H1W ±W ∓ and H1t¯ t couplings are suppressed in the same parameter space

  • At LHC the light Higgs window scenario may be closed through:

– pp → t¯ t → (bW +)(¯ bH−) → (bℓν)(bH1W −) → (bℓν)(bb¯ b)(jj) – pp → H±H1 → (H1W ±) + (b¯ b) → (b¯ bℓν) + (b¯ b)

  • Other possible channels:

– pp → ˜ t1˜ t∗

1h1, followed by 3 tagged b + 2ℓ + other untagged jets + missing pT

– Look for ˜ χ0

2 → ˜

χ0

1 + h1 decay Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh

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SLIDE 29

Summary

– σ˜

g˜ g is large. ˜

g → ˜ χ0

2q¯

q → ˜ χ0

1h1q¯

q → ˜ χ0

1q¯

qb¯ b(τ +τ −)

  • So far no dedicated analysis using B decays
  • Question : Can B → µ+µ−, Xsγ, τντ close this light Higgs window ?

Tohoku University, Sendai, Japan, 1-2 September, 2010 Dilip Kumar Ghosh