Characterizing dark matter model with Higgs portal at the ILC

Transcription

1 Characterizing dark matter model with Higgs portal at the ILC Jinmian Li Korea Institute for Advanced Study May 8th, 217 Collaboration with T. Kamon and P. Ko Pheno 217, University of Pittsburgh Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

2 Outline 1 Gauge invariant models: FDM, VDM and 2 Collider searches on benchmark points (hadronic channel) Features of DM spin Discovery prospects Spin characterization 3 The leptonic channel 4 Varying the coupling 5 Conclusion Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

3 Fermion DM Simplest extension of the SM including fermion DM (Z 2 : χ χ) L FDM = L SM + χ(i/ m χ g χ S)χ µs µ S 1 2 m2 S 2 λ HS H HS 2 µ 3 S µ 1 SH H µ 2 3! S3 λ S 4! S4 After EW symmetry breaking, portal includes two propagators: ( ) ( ) ( ) h cos α sin α H1 = s sin α cos α H2 Interacitions of DM and SM particles: L int FDM = (H 1 cos α + H 2 sin α) m f 2m ff 2 W v h v h f W µ + W µ m2 Z Z µ Z µ v h + g χ (H 1 sin α H 2 cos α) χχ Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

4 Vector DM Introduce an abelian dark gauge group U(1) X and a dark Higgs Φ L VDM = 1 4 V µνv µν +D µ Φ D µ Φ λ Φ (Φ Φ v2 φ 2 )2 λ HΦ (H H v2 h 2 )(Φ Φ v2 φ 2 ) Z 2 symmetry: V µ V µ, D µ = ( µ + ig V Q Φ V µ )Φ Interaction Lagrangian: L int VDM = (H 1 cos α + H 2 sin α) f m f v h ff 2m 2 W v h W µ + W µ m2 Z Z µ Z µ v h 1 2 g V m V (H 1 sin α H 2 cos α) V µ V µ Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

5 Scalar DM The model can be constructed by simply introducing a new scalar S in addition to the SM L = 1 2 µs µ S 1 2 m2 S 2 λ HS H HS 2 λ S 4! S4 Interaction Lagrangian: H (, (v h + h)/ 2) T, S = L int = h [ 2m2 W v h W + µ W µ + m2 Z v h Z µ Z µ ] + λ HS v h hs 2 Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

6 Outline 1 Gauge invariant models: FDM, VDM and 2 Collider searches on benchmark points (hadronic channel) Features of DM spin Discovery prospects Spin characterization 3 The leptonic channel 4 Varying the coupling 5 Conclusion Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

7 Benchmark points The relevant parameters in FDM for collider search: g χ = 3, sin α =.3, m χ = 8 GeV and m H2 = (2, 3, 4, 5) GeV. Parameters for the vector DM production are chosen accordingly: sin α =.3, m V = 8 GeV and g V is chosen such that the total decay width of H 2 is the same as benchmark points of FDM. m H2 [GeV] Γ min (H 2 ) [GeV] g V Fix m S = 8 GeV and take appropriate λ HS such that the production cross section of the signal process is the same with that in the FDM. Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

8 Features of DM spin at the ILC The dominant DM production process: e + e Z( ff) H 1,2 ( DD) DM pair four-momentum: P µ DD = P µ + P µ P µ e + e Z = ( s E Z, p Z ) DM pair invariant mass: m 2 DD = s + m2 Z 2E Z s Differential cross section: dσ D dt = 1 2π σ h Z(s, t) G D (t) G S (t) = β S 8π λ HS v h t m 2 h + im 2, hγ h G χ (t) = β3 χ 8π 2g 1 χt t m 2 + im H H1 Γ H1 1 1 t m 2 H 2 + im H2 Γ H2 2, G V (t) = β V gv 2 t2 16π 4m 2 (1 4m2 V t V + 12m4 V 1 t 2 ) t m 2 + im H H1 Γ H1 1 1 t m 2 H 2 + im H2 Γ H2 2 Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

9 Features of DM spin at the ILC Event Fraction Parton, g =3 χ SM FDM2 FDM3 FDM4 FDM5 1 2 [GeV] m DD Event Fraction g χ = 3 Delphes, g =3 χ SM FDM2 FDM3 FDM4 FDM5 [GeV] m DD 1 3 σ [pb] 1 4 FDM2 FDM3 FDM4 FDM s [GeV] Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

10 Discovery prospects of the hadronic channel Dominant background processes: e Z νe j e Z νe νe e νe j e + νe j e + Z j j e + W νe Z νe j Kinematic distributions: Event Fraction SM FDM2 FDM3 FDM4 FDM5 Event Fraction SM FDM2 FDM3 FDM4 FDM Event Fraction p (j1) [GeV] T SM FDM2 FDM3 FDM4 FDM miss E T [GeV] Event Fraction p (Z) [GeV] T SM FDM2 FDM3 FDM4 FDM min φ φ min = min i=1,2 φ(pmiss T, p(j i )) Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

11 Discovery prospects of the hadronic channel (FDM) Preselection cuts: Lepton veto Exactly two jets E miss T > 5 GeV Boosted decision tree analysis with inputs: m DD, p T (j 1 ), p T (Z), ET miss, φ min, p T (j 2 ), m jj NS/NB FDM2 FDM3 FDM4 FDM5 Significance FDM2 FDM3 FDM4 FDM5 L =1 fb BDT Cut BDT Cut Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

12 Discovery prospects of the hadronic channel (FDM) FDM2 FDM3 FDM4 FDM5 σ [fb] ɛ pre BDT N S /1 fb N B /1 fb N S / N S + N B Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

13 Spin characterization The same preselection and BDT cuts as used for FDM the benchmark point FDM2 (FDM3) are applied to the corresponding benchmark point 2 (3) and VDM2 (VDM3). 2 3 VDM2 VDM3 σ [fb] ɛ pre N S /1 fb S Event Number After BDT cut (m =2 GeV) H 2 +SM VDM+SM Event Number After BDT cut (m =3 GeV) +SM VDM+SM FDM+SM H 2 : δχ 2 = 5 ( N FDM+SM i i=1 VDM: S = N FDM S N +SM i N FDM+SM i N VDM S / N B ) 2 2 FDM+SM m χχ [GeV] m χχ [GeV] Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

14 The leptonic channel Smaller signal production rate: Br(Z l + l ).1 Br(Z qq) Lager background cross section: signal and pair W prodution Better final state resolution Event Fraction Parton, g =3 χ SM FDM2 FDM3 FDM4 FDM5 Event Fraction Delphes, g =3 χ SM FDM2 FDM3 FDM4 FDM m DD [GeV] m DD [GeV] Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

15 Discovery prospects of the leptonic channel Preselection cuts: Jet veto Exactly two opposite sign same flavor leptons E miss T > 5 GeV Two leptons invariant mass m ll [75, 15] GeV Two DM invariant mass m DD > 16 GeV Boosted decision tree analysis with inputs: p T (l 1 ), p T (l 2 ), ET miss, m ll, m DD, p T (Z), r(l, l), φ min Leptonic channel FDM2 FDM3 FDM4 FDM5 σ [fb] ɛ pre BDT N S /1 fb N B /1 fb N S / N S + N B Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

16 Spin characterization of the leptonic channel Leptonic channel 2 VDM2 σ [fb] ɛ pre N S /1 fb S Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

17 Varying the coupling: g χ = 1, g χ = 1 The benchmark points in VDM and are chosen with the same strategy as before. Changing of the H 2 decay width Off-shell contribution become important when g χ is large Event Fraction SM FDM2 FDM3 FDM4 FDM5 Delphes, g =1 χ Event Fraction SM FDM2 FDM3 FDM4 FDM5 Delphes, g =1 χ m DD [GeV] m DD [GeV] Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

18 Discovery prospects for varying g χ g χ = 1 g χ = 1 FDM2 FDM3 FDM4 FDM5 σ [fb] ɛ pre BDT N S /1 fb N B /1 fb N S / N S + N B σ [fb] ɛ pre BDT N S /1 fb N B /1 fb N S / N S + N B Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

19 Spin characterization for varying g χ g χ = 1: g χ = 1: 2 3 VDM2 VDM3 σ [fb] ɛ pre N S /1 fb S VDM2 VDM3 VDM4 VDM5 σ [fb] ɛ pre N S /1 fb S Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2

20 Conclusion The gauge invariant DM simplified models for FDM and VDM require at least two mediators. For the benchmark scenario with g χ = 3: (1) m H2 3 GeV can be probed at more than 3-σ level; (2) For those discoverable benchmark points in the FDM model, the spin discriminating against can be made with 3-σ level, spin discriminating against VDM is difficult. The leptonic channel has worse discovery potential than the hadronic channel. The smaller g χ increase the difference between the m χχ distributions of the FDM and the models, achieve better signal significances and spin discriminating powers. For g χ approaching the perturbative limit, benchmark points with H 2 in the full mass region of interest are discoverable and the spin discriminating against both the and VDM are quite promising. Jinmian Li (KIAS) DM Characterizing at ILC Pheno / 2