Signatures of alternative models beyond the Standard Model 이강영 ( 건국대학교 ) @ 연세대학교 2009. 10. 15.
Signatures of alternative models beyond the Standard Model
description
Transcript of Signatures of alternative models beyond the Standard Model
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.
2008 년 9 월 10 일 공식적으로 가동 .
올 11 월부터 정식 가동 .
둘레 27km 에 이르는 지구상 최대의 실험장치 .
다음과 같은 세계를 탐구하는 양성자 - 양성자 충돌장치 .
ECM = 14 TeV (max) ~ v = 0.999999991c (c= 빛의 속도 ) ~ d = 0.000000000000000000014 m
LHC The voyage to the ultimate world
Z’
• 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
Underlying Physics
Examples of U(1) extensions
E6 models breaking chain
χ model : β=0ψ model : β=π/2η model : β=arctan(-√5/3)
LR model
Diagonalized to give eigenvalues
(WL3, WR3, B) basis
Unknown model parameters are
MZ’ Z-Z’ mixing angle
Note that
where
and eigenstates
Z’ couplings to quarks and leptons
The Z-Z’ mixing angle is given by
Lagrangian for a Z’ in E6 model
e.g. Couplings for E6 inspired models and LR model
where
Phenomenology
Drell-Yan process
Z’
Experimental limits
PDG 2008
CDF collab., Phys. Rev. Lett., 95, 252001 (2005)
Identification of Z’ using t and b
S. Godfrey and T. A. W. Martin, Phys. Rev. Lett., 101, 151803 (2008)
Kq depends on QCD and EW corrections.
e.g.
S. Godfrey and T. A. W. Martin, PRL 101, 151803 (2008)
• Z’ mass and total width• Cross section to• Forward-backward asymmetry• Rapidity ratio• Off-peak asymmetry
Basic Observables
Measuring Z’ couplings at the LHCe.g.
F. Petriello and S. Quackenbush, Phys. Rev. D 77, 115004 (2008).
• Forward-backward asymmetry
where
• Rapidity ratio
y1 is introduced to exclude low Z’ rapidity events.
M. Dittmar, Phys. Rev. D 55, 161 (1997)
• 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’
Acceptance Cuts
Differential cross section
Parity symmetric couplings
Parity violating couplings
Calculation
Rewrite the differential cross section
Absorbing
We have
Define four observables
which are expressed in terms of observables
where
We derive the Master equation
e.g. If we let
Solving the Master equation to have
Results
• 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…
W’
• 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
Underlying Physics
LR model (e.g.)
Diagonalized to give
(WL+, WR
+) basis
where
Search for W’
• High energy single lepton final states
• Single top production
W’ → l- ν
W’ → t b
D0 collaboration, PRL 100, 031804 (2008)
2 22 ( ) ( ) ( ) ( )
2 ( ) ( ) 1 cos
T T T T T
T T
M p e p p e p
p e p
Transverse mass
Edges of transverse mass distribution are crucially related to the mass of W’.
Experimental limits
PDG 2008
CDF constraints
D0 observations
D0 collaboration, PRL 100, 031804 (2008)
Feasibility of W’ at the CMS
C. Hof, Acta. Phys. Pol. B 38, 443 (2007)
Reference models : same couplings as the SM
e.g.
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…
H+
• 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
Underlying Physics
Higgs sector in the LR model
Two triplets
a bidoublet
: breaking of SU(2)R and its L-R partner
: electroweak symmetry breaking and fermion masses
with VEVs
Note that
define
Charged Higgs boson in the LR model
Mass matrix
where
Charged Higgs mass
Diagonalization by
relevant tbH+ couplings
similarly for lepton sector
Phenomenology Light charged Higgs from t Hb at Tevatron
Light charged Higgs boson :
Absence of observed charged Higgs boson
Constrained by
CDF collaboration, PRL 96, 042003 (2006)
Pair production of charged Higgs boson at LEP
ALEPH collaboration, PLB 543, 1 (2002)
B and charged Higgs boson
R. Barlow, ICHEP 2006
Experimental constraints for LR charged Higgs
allowedallowed
D.-W. Jung, K. Y. Lee., Phys. Rev. D 76, 095016 (2007)
Light charged Higgs production at the LHC
sequential decay after tt pair production
108 top quarks produced
More than 105 charged Higgs expected
D.-W. Jung, K. Y. Lee., Phys. Rev. D 78, 015022 (2008)
Heavy charged Higgs production at the LHC
dominant channel :
K-factors for the NNLO QCD corrections
considered
N. Kidonakis, JHEP 05, 011 (2005).
D.-W. Jung, K. Y. Lee., Phys. Rev. D 78, 015022 (2008)
D.-W. Jung, K. Y. Lee., Phys. Rev. D 78, 015022 (2008)
in the LR model
in the 2HD model
Decay of produced charged Higgs boson
D.-W. Jung, K. Y. Lee., Phys. Rev. D 78, 015022 (2008)
• Different structure of the Yukawa couplings in the LR model leads to different phenomenology of the Higgs bosons from those of the 2HD model.
• Production cross section of the charged Higgs in the LR model is generically larger than that of the 2HD model at the LHC.
• Decays of the heavy charged Higgs boson in the
LR model combined with the production cross section might discriminate the LR charged Higgs from the 2HD charged Higgs boson.
H++
• H++: Doubly charged scalar• appears when there exist Higgs triplets or higher
multiplets.
• LR model• 3-3-1 model• Little Higgs model• Higgs triplet model for neutrinos
Underlying Physics
H++ in the LR model
• Production depends on WR mass
• Phenomenology depends on neutrino structure and see-saw mechanism.
Lepton number violating terms are
∝ mWR
Productions
Decays
Reconstructed pp→H++H-- →μ+ μ+ μ- μ-
CMS collab., J. Phys., G 34, N47 (2007)
Expected discovery of pp→H++H-- →μ+ μ+ μ- μ-
CMS collab., J. Phys., G 34, N47 (2007)
100% dilepton assumed
a. 100 fb-1
b. 300 fb-1
ATLAS collab., J. Phys., G 32, 73 (2006)
q’
• t’, b’: Fourth generation quarks
• Generically heavier than t and b since they are not observed yet.
• Why not even in the SM?
• LEP data on invisible decay of Z boson restricts the number of generations =3
: 4th neutrino should be heavier than mZ/2.
Underlying Physics
Why 3 generations?
LEP data on invisible decays
n =
Astrophysical data of He production
D.N. Schramm and M.S. Turner., Rev. of Mod. Phys. 70, 303 (1998)
Decays
• Charged current decays
• FCNC decays
…
Present bounds
PDG 2008
Q, L
• Excited quarks and leptons : Heavy states of quarks and leptons sharing quantum numbers with ordinary quarks and leptons.
• Appear in the composite models.
• Quarks and leptons are bound states of some constituents. (“Preon”)
• Experimentally similar to 4th generations.
Underlying Physics
• Excited fermions can be pair-produced via gauge couplings.
• If the compositeness scale is high enough, the compositeness manifests through effective 4-fermion contact interactions
PDG 2008
Dark Matter
• Dark matter : (Large) missing energy at the collider
• Appears in various models
• LSP in the MSSM• Lightest heavy states in the Little Higgs model• Lightest KK states in the extra dimensional model• And many other models…
Underlying Physics
• Many possibilities are open at the LHC.
Summary