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## Signatures of alternative models beyond the Standard Model

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**Signatures of alternative models beyond the Standard Model**이강영 (건국대학교) @ 연세대학교 2009. 10. 15.**Contents**• Introduction • Z’ • W’ • H+ • H++ • t’, b’ • Q, L • Dark matter • Summary**Introduction**• LHC will explore for the first time a relevant energy range, well above the Fermi scale. • LHC is the Energy frontier machine best to search for the new (heavy) particles. • We concentrate on the new particles discovery. • The detailed phenomenology depends upon the model.**LHC**Thevoyage to the ultimate world • 2008년 9월 10일 공식적으로 가동. • 올 11월부터 정식가동. • 둘레 27km에 이르는 • 지구상 최대의 실험장치. 다음과 같은 세계를 탐구하는 양성자-양성자 충돌장치. ECM = 14 TeV (max) ~ v = 0.999999991c (c=빛의속도) ~ d = 0.000000000000000000014 m**Underlying Physics**• Z’ : Extra neutral gauge boson • Exists when there is extra gauge symmetries. • U(1) extensions of the SM • LR model • Other gauge extended models • Other species : excited states of Z • Little Higgs model • Extra dimensional models**Examples of U(1) extensions**E6 models breaking chain χ model : β=0 ψ model : β=π/2 η model : β=arctan(-√5/3)**LR model**(WL3, WR3, B) basis Diagonalized to give eigenvalues**and eigenstates**where Note that Unknown model parameters are MZ’ Z-Z’ mixing angle**Z’ couplings to quarks and leptons**Lagrangian for a Z’ inE6 model The Z-Z’ mixing angle is given by**Phenomenology**Z’ Drell-Yan process**Experimental limits**PDG 2008**Identification of Z’ usingt and b**e.g. S. Godfrey and T. A. W. Martin, Phys. Rev. Lett., 101, 151803 (2008) Kq depends on QCD and EW corrections.**Measuring Z’ couplings at the LHC**e.g. F. Petriello and S. Quackenbush, Phys. Rev. D 77, 115004 (2008). • Z’ mass and totalwidth • Cross section to • Forward-backward asymmetry • Rapidity ratio • Off-peak asymmetry Basic Observables**Forward-backward asymmetry**where y1 is introduced to exclude low Z’ rapidity events. • Rapidity ratio**Acceptance Cuts**• Detector resolution effects are ignored. • Reconstruction efficiency of Z’ production is near 90% from CMS simulation. • CTEQ 6.5 NLO PDF used. • Integrated luminosity 100fb-1 unless stated otherwise. • Factorization and renormalization scale : MZ’**Calculation**Differential cross section Parity symmetric couplings Parity violating couplings**Rewrite the differential cross section**Absorbing We have**e.g. If we let**Solving the Master equation to have**If MZ’ =1.5 TeV, 100 fb-1 luminosity and y1=0.8 can**discriminate the example models with 90% C.L. and 1 ab-1 luminosity (SLHC) will provide precise determination. • If MZ’ =3 TeV, 100 fb-1 luminosity and y1=0.4 can discriminate some models. • For MZ’ =3 TeV, 1 ab-1 luminosity (SLHC) will provide reasonable determination.**Exotic Z’**• Generation-dependent couplings • Leptophobic • Hadrophobic • Flavour-violating • And more…**Underlying Physics**• W’ : Extra charged gauge boson • Exists when there are extra gauge symmetries more than U(1). • LR model • Other gauge extended models • Other species : excited states of W • Little Higgs model • Extra dimensional models**LR model (e.g.)**(WL+, WR+) basis Diagonalized to give where**Search for W’**W’ → l-ν • High energy single lepton final states • Single top production W’ → t b**Transverse mass**• Edges of transverse mass distribution are crucially related to the mass of W’. D0 collaboration, PRL 100, 031804 (2008)**Experimental limits**PDG 2008**D0 observations**D0 collaboration, PRL 100, 031804 (2008)**Feasibility of W’ at the CMS**e.g. C. Hof, Acta. Phys. Pol. B 38, 443 (2007) Reference models : same couplings as the SM**Exotic W’**• Left-right asymmetric : coupling constants and CKM • Leptophobic • Hadrophobic • Flavour-dependent SU(2) • Exotic gauge self-couplings : W’-W-Z, W’-W’-Z … • And more…**Underlying Physics**• H+: Charged scalar • Exists when there is extra Higgs sector more than SM singlet. • 2HD model • MSSM and more extensions (NMSSM etc.) • LR model • Other GUT-based model