Signatures in alternative models beyond the Standard Model

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Signatures in alternative models beyond the
Standard Model

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_at_ Korean CMS group workshop 2008. 12. 19.
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Contents

• Introduction
• Z
• W
• H
• H
• t, b
• Q, L
• Dark matter
• Summary

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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.

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Z
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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

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Examples of U(1) extensions
E6 models breaking chain
? model ß0 ? model ßp/2 ? model
ßarctan(-v5/3)
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LR model
(WL3, WR3, B) basis
Diagonalized to give eigenvalues
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and eigenstates
where
Note that
Unknown model parameters are
MZ Z-Z mixing angle
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Z couplings to quarks and leptons
Lagrangian for a Z
The Z-Z mixing angle is given by
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Couplings for E6 inspired models and LR model
e.g.
where
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Phenomenology
Drell-Yan process
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Experimental limits
PDG 2008
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CDF collab., Phys. Rev. Lett., 95, 252001 (2005)
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Identification of Z using t and b
e.g.
S. Godfrey and T. A. W. Martin, Phys. Rev.
Lett., 101, 151803 (2008)
Kq depends on QCD and EW corrections.
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S. Godfrey and T. A. W. Martin, PRL 101, 151803
(2008)
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Measuring Z couplings at the LHC
e.g.
F. Petriello and S. Quackenbush, Phys. Rev. D 77,
115004 (2008).
Basic Observables

• Z mass and total width
• Cross section to
• Forward-backward asymmetry
• Rapidity ratio
• Off-peak asymmetry

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• Forward-backward asymmetry

where
y1 is introduced to exclude low Z rapidity
events.

• Rapidity ratio

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M. Dittmar, Phys. Rev. D 55, 161 (1997)
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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

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Calculation
Differential cross section
Parity symmetric couplings
Parity violating couplings
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Rewrite the differential cross section
Absorbing
We have
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Define four observables
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which are expressed in terms of observables
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We derive the Master equation
where
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e.g. If we let
Solving the Master equation to have
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Results
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• If MZ 1.5 TeV, 100 fb-1 luminosity and y10.8
  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 y10.4 can
  discriminate some models.
• For MZ 3 TeV, 1 ab-1 luminosity (SLHC) will
  provide reasonable determination.

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Exotic Z

• Generation-dependent couplings
• Leptophobic
• Hadrophobic
• Flavour-violating
• And more

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W
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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

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LR model (e.g.)
(WL, WR) basis
Diagonalized to give
where
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Search for W
W ? l- ?
W ? t b

• High energy single lepton final states
• Single top production

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Transverse mass
Edges of transverse mass distribution are
crucially related to the mass of W.
D0 collaboration, PRL 100, 031804 (2008)
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Experimental limits
PDG 2008
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CDF constraints
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D0 observations
D0 collaboration, PRL 100, 031804 (2008)
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Feasibility of W at the CMS
e.g.
C. Hof, Acta Phys. Pol. B 38, 443 (2007)
Reference models same couplings as the SM
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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

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H
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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

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Higgs sector in the LR model
Two triplets
breaking of SU(2)R and its L-R partner
a bidoublet
electroweak symmetry breaking and fermion masses
with VEVs
Note that
define
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Charged Higgs boson in the LR model
Mass matrix
where
Diagonalization by
Charged Higgs mass
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relevant tbH couplings
similarly for lepton sector
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Phenomenology
Light charged Higgs from t? H??b at Tevatron
Light charged Higgs boson
Absence of observed charged Higgs boson
Constrained by
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CDF collaboration, PRL 96, 042003 (2006)
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Pair production of charged Higgs boson at LEP
ALEPH collaboration, PLB 543, 1 (2002)
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B? ? ???? and charged Higgs boson
R. Barlow, ICHEP 2006
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Experimental constraints for LR charged Higgs
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allowed
allowed
D.-W. Jung, K. Y. Lee., Phys. Rev. D 76, 095016
(2007)
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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)
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Heavy charged Higgs production at the LHC
dominant channel
K-factors for the NNLO QCD corrections
considered N. Kidonakis, JHEP 05, 011 (2005).
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D.-W. Jung, K. Y. Lee., Phys. Rev. D 78, 015022
(2008)
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D.-W. Jung, K. Y. Lee., Phys. Rev. D 78, 015022
(2008)
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Decay of produced charged Higgs boson
in the LR model
in the 2HD model
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D.-W. Jung, K. Y. Lee., Phys. Rev. D 78, 015022
(2008)
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• 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.

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H
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Underlying Physics

• 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

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H in the LR model
Lepton number violating terms are

• Production depends on WR mass
• Phenomenology depends on neutrino structure and
  see-saw mechanism.

? mWR
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Productions
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Decays
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Reconstructed pp?HH-- ?µ µ µ- µ-
CMS collab., J. Phys., G 34, N47 (2007)
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Expected discovery of pp?HH-- ?µ µ µ- µ-
CMS collab., J. Phys., G 34, N47 (2007)
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100 dilepton assumeda. 100 fb-1b. 300 fb-1
ATLAS collab., J. Phys., G 32, 73 (2006)
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q
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Underlying Physics

• 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.

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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)
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Decays

• Charged current decays
• FCNC decays

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Present bounds
PDG 2008
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Q, L
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Underlying Physics

• 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.

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• 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
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Dark Matter
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Underlying Physics

• 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

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Summary

• Many possibilities are open at the LHC.