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Back to 1994-1997 ( ) 1994-1997 ( CTP) : , ( , , ) Papers with Prof. Song Chiral perturbation theory versus

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Back to 1994-1997

고병원 (고등과학원)

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1994-1997

  • 송희성 선생님 (서울대 CTP)
  • 박사과정 학생 : 이정일, 백승원 (유채현, 정동원, 송완영…)
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Papers with Prof. Song

Chiral perturbation theory versus vector meson dominance in the decays phi --> rho gamma gamma and phi --> omega gamma gamma Pyungwon Ko (Hong-Ik U.), Jungil Lee, H.S. Song (Seoul Natl. U.). Oct 1995. 11 pp. Published in Phys.Lett. B366 (1996) 287-292 Inclusive S wave charmonium productions in B decays Pyungwon Ko (Hong-Ik U.), Jungil Lee, H.S. Song (Seoul Natl. U.). Oct 1995. 12 pp. Published in Phys.Rev. D53 (1996) 1409-1415 Color octet mechanism in γ + p→J/ψ + x Pyungwon Ko (Hong-Ik U.), Jungil Lee, H.S. Song (Seoul Natl. U.). Feb 1996. 22 pp. Published in Phys.Rev. D54 (1996) 4312-4325 Color octet heavy quarkonium productions in Z0 decays at LEP Seungwon Baek (Seoul Natl. U.), P . Ko (Hong-Ik U.), Jungil Lee, H.S. Song (Seoul Natl. U.). Jul 1996. 14 pp. Published in Phys.Lett. B389 (1996) 609-615 Color octet mechanism and J/ψ polarization at LEP Seungwon Baek (Seoul Natl. U.), P . Ko (Hong-Ik U.), Jungil Lee, H.S. Song (Seoul Natl. U.). Jan 1997. 15 pp. Published in Phys.Rev. D55 (1997) 6839-6843 Color octet mechanism in the inclusive D wave charmonium productions in B decays Pyung-won Ko (Hong-Ik U.), Jungil Lee, H.S. Song (Seoul Natl. U.). Jan 1997. 11 pp. Published in Phys.Lett. B395 (1997) 107-112 Polarized J / psi production at CLEO Seungwon Baek (Seoul Natl. U.), P . Ko (KAIST, Taejon), Jungil Lee, H.S. Song (Seoul Natl. U.). Apr 1998. 12 pp. Published in J.Korean Phys.Soc. 33 (1998) 97-101

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Chiral extensions

  • f the SM
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One scenario: gluon fusion + diphoton decay via loop

Production: gluon fusion Diphoton decay channel

g g γ γ

Colored particle Charged particle

  • It is not easy to get σ(gg→ΦNew)BR(ΦNew→γγ)~5 fb

Ex) Two Higgs doublet Model (Type-II)

σ(gg→H)~850 fb × cot2β

BR(H→γγ)~O(10-5)

σ(gg→A)~850 fb × 2cot2β

BR(A→γγ)~O(10-5)

We need exotic colored and/or charged particles

Let us discuss simple case of (SM) singlet scalar boson + exotic particles

(Angelescu, Djouadi, Moreau arxiv:1512.0492)

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Basic Questions

  • Raison d’être of (fundamental?) singlet scalar and vector-

like fermions ? Completely singlet particles ???

  • Uncomfortable to have a completely singlet
  • Two Options : Another new Higgs boson related with
  • New spontaneously broken gauge symmetry, or
  • Composite (pseudo)scalar boson
  • Why vector like fermions have EW scale mass ?
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Answers

  • New chiral U(1)’ symmetry broken by new singlet scalar (Higgs)
  • 750 GeV excess ~ U(1)’ breaking scalar (could be even dark Higgs)
  • Vectorlike fermions : chiral under new U(1)’ , anomaly cancellation,

and get massive by new Higgs mechanism ~ EW scale mass

  • Can we generate phi(750) decay width ~ 45 GeV without any

conflict with the known constraints ?

  • Yes, if phi(750) mainly decays into new particles
  • Many examples : (i) Leptophobic U(1)’ with fermions in the

fundamental representation of E6, (ii) anther similar 2HDM + singlet model (iii) Dark U(1)’ plus dark sector, Dark Higgs decay into a pair

  • f Z’
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A Type-II Extension has all the necessary ingredients

Table 1: Matter contents in U(1)′ model inspired by E6 GUTs. Here, i denotes the generation index: i = 1, 2, 3. Fields SU(3) SU(2) U(1)Y U(1)′ Zex

2

Qi 3 2 1/6 −1/3 ui

R

3 1 2/3 2/3 di

R

3 1 −1/3 −1/3 Li 1 2 −1/2 + ei

R

1 1 −1 ni

R

1 1 1 H2 1 2 −1/2 H1 1 2 −1/2 −1 + Φ 1 1 −1 Di

L

3 1 −1/3 2/3 Di

R

3 1 −1/3 −1/3

  • Hi

L

1 2 −1/2 −

  • Hi

R

1 2 −1/2 −1 Ni

L

1 1 −1

Fermions : 27 of E6 (!!!) Scalar Bosons : 2 Doublets + 1 Singlet

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Basic Ingredients

  • New vectorlike fermions which are chiral under new

U(1)’ : non-decoupling effects on X->gg, gam gam

  • Diphoton at 750 GeV = Higgs boson from U(1)’ sym

breaking, mostly a SM singlet scalar

  • All the masses from dynamical (Higgs) mechanism
  • New decay modes to enhance the total decay rate

cf: SU(2)H by W.C.Huang, Y.L.S.Tsai,TCYuan (2015) and applied for 750 GeV diphoton excess

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Yukawa couplings

The U(1)′-symmetric Yukawa couplings in our model are given by Vy = yu

ijuj RH† 1iσ2Qi + yd ijdj RH2Qi + ye ijej RH2Li + yn ijnj RH† 1iσ2Li + H.c.,

(16) where σ2 is the Pauli matrix. The Yukawa couplings to generate the mass terms for the extra particles are V ex = yD

ijDj RΦDi L + yH ij

Hj

RΦ

Hi

L + yN IJNc LH† 1iσ2

Hi

L + y′N IJ

Hi

RH2Nj L + H.c. .

(17)

One can introduce new Zex

2 -odd scalar field X with the SU(3)C ×SU(2)L×U(1)Y ×U(1)H

quantum numbers equal to (1, 1, 0; −1). Then the gauge-invariant Lagrangian involving X is given by LX = DµX†DµX − (m2

X0 + λH1XH† 1H1 + λH2XH† 2H2)X†X − λX(X†X)2

−

  • λ

′′

ΦX(Φ†X)2 + H.c.

  • − λΦXΦ†ΦX†X − λ

′

ΦX|Φ†X|2

−

  • yD

dXdRDLX + y ˜ H LXL

HRX† + H.c.

  • (18)

Complex Scalar DM

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750 GeV Diphoton Excess

y10 y5 y1

tot10 GeV LHC13

200 400 600 800 1000 0.001 0.1 10 1000 mf ΣpphBRhΓΓfb

tot10 GeV tot1 GeV

500GeVmf1TeV LHC13

2 4 6 8 10 104 0.01 1 100 y ΣpphBRhΓΓfb

Ko, Omura, Yu, arXiv:1601.00586

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Key Aspects of the Model

  • Extra fermions are chiral under U(1)’, and vectorlike

under the SM gauge group : this is the consequence of gauge anomaly cancellation (27 rep. of E6 group)

  • Their masses from U(1)’ breaking > nondecoupling
  • U(1)’-breaking scalar produces a new singlet-like scalar

h_phi ~ 750 GeV scalar boson

  • Decay channels of 750 GeV are determined by gauge

symmetry of the underlying Type-II 2HDM with U(1)’ Higgs gauge symmetry (hh, Hh, HH, Z’Z’,DM DM etc.)

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Higgs portal DM

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15

  • Dark & visible matter and dark energy, neutrinos

Jan Oort (1932), Fritz Zwicky (1933) Strong gravitational lensing in Abell 1689 Bullet cluster

v ∝ r−1/2

  • bservation

expectation (Planck+WP+highL+BAO)

Ωb ' 0.048 ΩDM ' 0.259 ΩΛ ' 0.691

Heights of peaks ⇒ Ωb, ΩDM

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Singlet Portals

  • If there is a dark sector and DM is thermal,

then we need a portal to it

  • There are only three unique gauge singlets in

the SM + RH neutrinos for Type I seesaw

H†H, Bµν, NR

SM Sector Dark Sector

NR ↔ e HlL

Baek, Ko, Park, arXiv:1303.4280, JHEP

e.g. φ†

XφX, Xµν, ψ† XφX

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DM searches @ colliders : Beyond the EFT and simplified DM models

  • S. Baek, P

. Ko, M. Park, WIPark, C.Yu, arXiv:1506.06556, PLB (2016)

  • P

. Ko and Hiroshi Yokoya, arXiv:1603.04737, JHEP (2016)

  • P

. Ko, A. Natale, M. Park, H. Yokoya, arXiv:1605.07058, JHEP(2017)

  • P

. Ko and Jinmian Li, arXiv:1610.03997, PLB (2017)

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Crossing & WIMP detection

Correct relic density Efficient annihilation then

  • q

q

Efficient annihilation now (Indirect detection) Efficient scattering now (Direct detection) Efficient production now (Particle colliders)

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  • Usually effective operator is replaced by a

single propagator in simplified DM models

  • This is not good enough, since we have to

respect the full SM gauge symmetry (Bell et al for W+missing ET)

  • In general we need two propagators, not
  • ne propagator, because there are two

independent chiral fermions in 4-dim spacetime

1 Λ2

i

¯ qΓiq ¯ χΓiχ ! gqgχ m2

φ s ¯

qΓiq ¯ χΓiχ

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Our Model: a ’simplified model’ of colored t-channel, spin-0, mediators which produce various mono-x + missing energy signatures (mono-Jet, mono-W, mono-Z, etc.):

qR,L χ ¯ χ

e

qR, f QL ¯ qR,L g uL χ ¯ χ

f

QL ¯ dL W

¯ χ χ

e

qR, f QL qR,L qR,L g ¯ χ χ

e

qR, f QL qR,L qR,L g

arXiv:1605.07058 (with A. Natale, M.Park, H. Yokoya) for t-channel mediator W+missing ET : special

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  • This is good only for W+missing ET, and

not for other singatures

  • The same is also true for (scalar)x(scalar)
  • perator, and lots of confusion on this
  • perator in literature
  • Therefore let me concentrate on this case

in detail in this talk

1 Λ2

i

¯ qΓiq ¯ χΓiχ ! gqgχ m2

φ s ¯

qΓiq ¯ χΓiχ

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L = LSM µHSSH†H λHS 2 S2H†H +1 2(∂µS∂µS m2

SS2) µ3 SS µ S

3 S3 λS 4 S4 +ψ(i ⇥ ∂ mψ0)ψ λSψψ

Ψ SM H S

mixing invisible decay Production and decay rates are suppressed relative to SM.

22

This simple model has not been studied properly !!

Singlet fermion CDM

Baek, Ko, Park, arXiv:1112.1847

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Monojet+missing ET

1 Λ3

dd

! 1 Λ3

dd

 m2

125

s m2

125 + im125Γ125

  • m2

125

s m2

2 + im2Γ2

  • ⌘

1 Λ3

col(s)

Can be obtained by crossing : s <>t There is no single scale you can define for collider search for missing ET

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g g t Hi χ ¯ χ

q q q q Hi χ ¯ χ V

q ¯ q V V Hi χ ¯ χ

Figure 1: The dominant DM production processes at LHC.

dσi dmχχ ∝ | sin 2α gχ m2

χχ − m2 H1 + imH1ΓH1

− sin 2α gχ m2

χχ − m2 H2 + imH2ΓH2

|2

Interference between 2 scalar bosons could be important in certain parameter regions

sin α = 0.2, gχ = 1, mχ = 80GeV

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  • EFT : Effective operator Lint = mq

Λ3

dd ¯

qq ¯ χχ

  • S.M.: Simple scalar mediator S of

Lint =

  • mq

vH sin α

  • S¯

qq − λs cos αS ¯ χχ

  • H.M.: A case where a Higgs is a mediator

Lint = −

  • mq

vH cos α

  • H ¯

qq − λs sin αH ¯ χχ

  • H.P.: Higgs portal model as in eq. (2).
  • ■

■ ■ ■ ■ ■ ■ ■ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲

  • ■

■ ■ ■ ■ ■ ■ ■ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲

  • ■

■ ■ ■ ■ ■ ■ ■ ■ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲

  • ■

■ ■ ■ ■ ■ ■ ■ ■ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲

50 100 500 1000 5000 104 50 100 150

50 100 500 1000 5000 104 3 · 104

mχ = 400GeV mχ = 50GeV

50 100 150

M∗ [GeV]

H.P. S.M. mχ 50 GeV 400 GeV

mχ = 400GeV mχ = 50GeV

¯ Λdd ¯ Λdd

mH2 [GeV]

  • ■

■ ■ ■ ■ ■ ■ ■ ■ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲

  • ■

■ ■ ■ ■ ■ ■ ■ ■ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲

50 100 500 1000 5000 104 100 200 300 400

50 100 500 1000 5000 104 3 · 104

mχ = 400GeV mχ = 50GeV

100

M∗ [GeV]

H.P. S.M. mχ 50 GeV 400 GeV

mχ = 400GeV mχ = 50GeV

¯ Λdd ¯ Λdd 200 300 400

mH2 [GeV]

  • FIG. 3:

The experimental bounds on M∗ at 90% C.L. as a function of mH2 (mS in S.M. case) in the monojet+/ ET search (upper) and t¯ t + / ET search (lower). Each line corresponds to the EFT approach (magenta), S.M. (blue), H.M. (black), and H.P. (red), respectively. The bound of S.M., H.M., and H.P., are expressed in terms of the effective mass M∗ through the Eq.(16)-(20). The solid and dashed lines correspond to mχ = 50 GeV and 400 GeV in each model, respectively.

H.P.

  • !

m2

H2ˆ

s H.M.,

S.M. !

m2

Sˆ

s EFT,

H.M. 6= EFT .