DM from om chir hiral al U( U(1) 1) X dar dark k sect ector or And nd diphot diphoton on exces cess Takaaki Nomura (KIAS) Based on: P.Ko, T.N. arXiv:1601.02490 (to be published in PLB) and work in progress 2016-05-07 17 th New Higgs Working Group @ Toyama
1. Introduction 2. Model 3. Analysis 4. Summary
1. Introduction Diphoton excess at 750 GeV ATLAS-CONF-2015-081, CMS-PAS-EXO-15-004 Both ATLAS and CMS observed bump on diphton invariant mass distribution 3.6 σ : ATLAS 2.6 σ : CMS (Local significance)
1. Introduction Diphoton excess at 750 GeV Updated results are presented at the Moriond 2016 3.9 (2.0) σ : ATLAS Local (Global Significance) 3.4 (1.6) σ : CMS CMS added 0.6 fb -1 13 TeV data and combined with 8 TeV result ATLAS-CONF-2015-081, CMS-PAS-EXO-15-004 Both ATLAS and CMS observed bump on diphton invariant mass distribution 3.6 σ : ATLAS 2.6 σ : CMS (Local significance)
1. Introduction Diphoton excess at 750 GeV (ATLAS) ATLAS Collaboration, ATLAS-CONF-2016-018. Spin 2 Spin 0
1. Introduction Diphoton excess at 750 GeV (ATLAS) Spin 0 Spin 2 Ø m X ~750 GeV ATLAS Collaboration, ATLAS-CONF-2016-018. Ø Width can be narrow or wide Ø Local significance 3.9 (3.6) σ for spin 0(2) Ø Global significance 2.0(1.8) σ for spin 0(2)
1. Introduction Diphoton excess at 750 GeV (ATLAS) Consistency between 8 TeV and 13 TeV result Deviation between 8 TeV and 13 TeV result Ø Spin 0 : 1.2 (2.1) σ for gg(qq) prodcution Ø Spin 2 : 2.7 (3.3) σ for gg(qq) prodcution
1. Introduction Diphoton excess at 750 GeV (CMS) CMS collaboration CMS-PAS-EXO-16-018 Spin 2 Spin 0 Ø Evaluated through likelihood scan vs equivalent 13TeV cross-section at mX = 750GeV under both spin (narrow-width) hypotheses Combined with 8 TeV data
CMS collaboration CMS-PAS-EXO-16-018 1. Introduction Diphoton excess at 750 GeV (CMS) Spin 0 Spin 2 Spin 0 Spin 2
1. Introduction Diphoton excess at 750 GeV (CMS) Spin 2 Spin 0 Ø m X ~750 GeV Ø Narrow width is preferred Ø Local significance 3.4 σ (maximum) Ø Global significance 1.6 σ
1.introduction v Constraints from other modes arXiv:1604.06446 (Franceschini et. al.)
1.introduction How we can interpret the diphoton excess? Ø It could be new particle : spin 0 or 2 Spin 0 is preferred but spin 2 is not excluded Ø Cross section to produce a new particle φ σ ( pp → ϕ ) BR ( ϕ → γγ ) ≈ 3 − 10 fb Ø Width of φ Best fit value by ATLAS : Γ ~45 GeV (not so significant) CMS : Narrow width is preferred (<< 10 GeV) Narrow width? Or wide width? Width can be 0-100 GeV Ø No significant associated events (other jets, leptons etc.)
1. Introduction One scenario: gluon fusion + diphoton decay via loop Production: gluon fusion Diphoton decay channel γ g g γ Colored particle Charged particle
1. Introduction One scenario: gluon fusion + diphoton decay via loop Production: gluon fusion Diphoton decay channel γ g g γ Colored particle Charged particle It is not easy to get σ (gg →Φ New )BR( Φ New →γγ )~5 fb Ex) Two Higgs doublet Model (Type-II) (Angelescu, Djouadi, Moreau arxiv:1512.0492) σ (gg → A)~850 fb × 2cot 2 β σ (gg → H)~850 fb × cot 2 β BR(H →γγ )~O(10 -5 ) 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
1. Introduction Simple way: vector-like fermion + singlet scalar Yukawa coupling and masses of VLF are arbitrary ( ) ϕ M F FF y FF v Lets consider F to be chiral under dark gauge symmetry v F is massless before dark gauge symmetry breaking v These Yukawa coupling and mass are related
1. Introduction Simple way: vector-like fermion + singlet scalar Yukawa coupling and masses of VLF are arbitrary ( ) ϕ M F FF y FF v Lets consider F to be chiral under dark gauge symmetry v F is massless before dark gauge symmetry breaking v These Yukawa coupling and mass are related Let us discuss diphoton excess via Dark sector Dark sector : charged under dark (extra) gauge symmetry
1. Introduction Our proposal SM+U(1) X + New fermions and scalars with U(1) X charge v New fermions are VL under SM but chiral under U(1) X New fermions get masses after U(1) X breaking v Relevant couplings are related to new gauge coupling g X v 750 GeV scalar can decay into new massive gauge boson (Z’) v DM candidate is contained in a model
1. Introduction 2. Model 3. Analysis 4. Summary
2. Model Model : local U(1) X model with exotic particles Contents in dark sector （ anomaly free ） (3 generations of fermions) X,N : DM candidate
2. Model Model : local U(1) X model with exotic particles Contents in dark sector （ anomaly free ） (3 generations of fermions) X,N : DM candidate New Lagrangian Y = y E E L E R Φ + y N N L N R Φ * + y U U L U R Φ * + y D D L D R Φ L + y Ee E L e R X + y Uu U L u R X * + y Dd D L d R X + h . c . 2 + λ H 4 + µ Φ 2 + µ X V = µ 2 H 2 X 2 Φ 2 2 X 4 + λ X X 4 + λ H Φ H 2 Φ 2 + λ HX H 2 + λ X Φ X 2 Φ 2 + λ Φ Φ
2. Model Model : local U(1) X model with exotic particles Contents in dark sector （ anomaly free ） (3 generations of fermions) X,N : DM candidate New Lagrangian Y = y E E L E R Φ + y N N L N R Φ * + y U U L U R Φ * + y D D L D R Φ L Giving mass for new fermions + gg fusion and γγ decay of Φ + y Ee E L e R X + y Uu U L u R X * + y Dd D L d R X + h . c . 2 + λ H 4 + µ Φ 2 + µ X V = µ 2 H 2 X 2 Φ 2 2 X 4 + λ X X 4 + λ H Φ H 2 Φ 2 + λ HX H 2 + λ X Φ X 2 Φ 2 + λ Φ Φ
2. Model Model : local U(1) X model with exotic particles Contents in dark sector （ anomaly free ） (3 generations of fermions) X,N : DM candidate New Lagrangian Y = y E E L E R Φ + y N N L N R Φ * + y U U L U R Φ * + y D D L D R Φ L Giving mass for new fermions + gg fusion and γγ decay of Φ + y Ee E L e R X + y Uu U L u R X * + y Dd D L d R X + h . c . Decay of new fermions F 2 + λ H 4 + µ Φ 2 + µ X V = µ 2 H 2 X 2 Φ 2 F → X f SM 2 X 4 + λ X X 4 + λ H Φ H 2 Φ 2 + λ HX H 2 + λ X Φ X 2 Φ 2 + λ Φ Φ
2. Model Gauge Symmetry breaking and Z’ v VEVs of scalar fields U(1) X is broken by < Φ > H = 1 Φ = 1 v , v φ 2 2 Massive Z’ − µ 2 2 − µ Φ ( ) v ≈ λ , v φ ≈ λ H Φ << 1 We assume H- Φ mixing is negligible λ Φ Φ = ( v φ + φ + iG X ) / 2 v Masses of Z’ and new fermions 2( a + b ) g X m F y F = m F = y F 2 ≈ ( a + b ) 2 g X m Z ' 2 v φ 2 , m Z ' v φ 2 2 g X 2 λ Φ = 2 m φ 2 m Z ' v Z’ decays through small Z-Z’ mixing
2. Model BRs of Z’ in model 1.00 Z Z’ f SM q q 0.50 e � e � � Μ � Μ � f SM 0.20 BR Ν Ν Τ � Τ � 0.10 0.05 150 200 250 300 350 m Z ' � GeV � v Z’ decays into SM fermions via kinetic mixing of U(1) Y and U(1) X
2. Model BRs of Z’ in model 1.00 Z Z’ f SM q q 0.50 e � e � � Μ � Μ � f SM 0.20 BR Ν Ν Τ � Τ � f SM Z’ 0.10 F X 0.05 F f SM 150 200 250 300 350 m Z ' � GeV � v Z’ decays into SM fermions via kinetic mixing of U(1) Y and U(1) X v Yukawa interaction XFf may change the BRs (we ignore in this talk)
2. Model Stability of Dark Matter candidate v Accidental Z 2 symmetry after U(1)X breaking F L , F R , X : Z 2 odd Others : Z 2 even Neutral Z 2 odd particle can be DM candidate : X, N Note: There can be a term : Φ n X ( Φ n X*) a/(a+b)=n for gauge invariance : suitable choice of a, b can make a/(a+b) non-integer (absolutely stable), or make n very large (long-lived X). We choose a~b~1 for simplicity
1. Introduction 2. Model 3. Analysis 4. Summary
3. Analysis Relic density of the Dark Matter X, N We focus on the annihilation processes N N Z’ Z’ XX → Z’Z’ NN → Z’Z’ N Z’ Z’ N X Z’ Z’ X X Z’ Z’ X Relevant gauge interactions Search for the parameter region satisfying observed relic density 0.1159 ≤ Ω D h 2 ≤ 0.1215 Planck data (90% C.L.) P.A.R. Ade et al [Planck Collaboration] (2013) Ω D is Calculated with MicrOMEGAs ( G. Belanger, F. Boudjema, A. Pukhov and A. Semenov)
3. Analysis Relic density of the Dark Matter X 2.00 M N � 600 GeV Λ X � � 0 0.70 1.00 g x � 0.1 M N � 600 GeV 0.50 0.50 0.20 Λ X � g X g x � 0.3 0.30 0.10 0.05 0.20 0.15 0.02 150 200 300 500 150 200 300 500 m X � GeV � m X � GeV � v For non-zero λ X Φ s-channel and t(u)-channel interfere v The resonant effect around m X ~ m Φ /2 for non-zero λ X Φ v g x = 0.2 ~ 0.5 can provide with relic density (m X = 120~500 GeV)
3. Analysis Relic density of the Dark Matter N m X � 600 GeV 0.70 0.50 g X 0.30 0.20 0.15 150 200 300 500 m N � GeV � v s-channel and t(u)-channel always interfere v The resonant effect around m X ~ m Φ /2 v g x < 0.5 can provide with relic density (m X = 120~500 GeV)
3. Analysis Direct detection constraint of DM Possible DM-nucleon scattering processes v Z’ exchanging suppressed by small Z-Z’ mixing v The SM Higgs exchanging suppressed by small λ XH v φ exchanging non-trivial if λ X Φ is not zero XXGG effective interaction X-nucleon scattering cross section (F. Giacchino, A. Ibarra, L. L. Honorez, M. H. G. Tytgat and S. Wild, JCAP 1602, no. 02, 002 (2016) [arXiv:1511.04452 [hep-ph]] ) f TG is the numerical value Ø In current case σ DN < 10 -48 cm 2
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