1. Z’ Production in 331 models
Universidad Nacional de Colombia
Departamento de Física
Grupo de Física Teórica de Altas Energías
Z’ Production in 331 models
Fredy A. Ochoa and Roberto Martínez
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São Miguel das Missões, Dec. 2007

2. Outlines Motivations Z’ Basics: Theoretical and experimental facts
The 331 Model
Z’ Production at Tevatron
Z’ Production at LHC
Conclusions and Prospects
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3. ¿Why beyond SM?
The mechanism for breaking the electroweak symmetries and
generating mass
The unification of forces, including gravity.
The conection to cosmology (Baryon asymmetry, Cold Dark Matter. )
The mass hierarchy problem
The existence of 3 families
The electric charge quantization
The neutrino masses and mixing
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4. Z’ Boson Basics: Theoretical Facts
A Z’ particle is a neutral, spin-1, colorless and self-adjoint gauge boson
arising from some extensions of the SM, which is more massive than the
SM Z boson.
Z’-models: +U(1) from E6, Left-Right, Little Higgs, Sequential SM, 331
Z and Z’ bosons are not true mass eigenstates. The physical bosons are
mixing states Z1 and Z2 with a mixing angle q, which cause deviations from
the SM (Z-pole parameters, shifts in the W couplings, shifts in the Weak
Charge, F-B Asymmetries, etc.)
The MZ’ is not constrained by the theory. It can be anywhere between
Eweak < MZ’ < EGUT.
An observation of the Z’ would provide information on the GUT group
and on its symmetry breaking.
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5. Z’ Boson Basics: Experimental Facts
A Z’ particle is a resonance, which is more massive than the SM Z,
observed in the Drell-Yan process pp(pp ) l l + X.
A Z’ can be directly observed through its decay products. It is possible
in lepton collisions (ILC) or in hadron collisions (Tevatron, LHC).
Present limits from direct production at Tevatron and virtual effects at
LEP through mixing with the Z boson, imply that MZ’ ~ TeV and Sq ~ 10. -3
In hadron colliders, the sensitivity to Z’ production decaying into
quarks pairs is reduced compared to lepton pairs due to the QCD
background
An observation of a Z’ would serve as a calibration point for future
detectors
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6. SU(3)C X SU(2)L X U(1)Y SU(3)C X SU(3)L X U(1)X Q = T3 + Y
¿What is 331?
F. Pisano and V. Pleitez, Phys. Rev. D46, (1992) 410
P.H. Frampton, Phys. Rev. Lett. 69 (1992) 2889
3-3-1 SM
SU(3)C X SU(2)L X U(1)Y
SU(3)C X SU(3)L X U(1)X
Q = T3 + Y
Q = T3 + T8 + X b *
qL : (3, 3, Xq )
lL : (1, 3, Xl )
qL : (3, 3, Xq )
lL : (1, 3, Xl ) * *
qL : (3, 2, 1/6)
lL : (1, 2, -1/2)
yL =
yL =
yL = * * * *
qR : (3, 1, Xq)
lR : (1, 1, Xl)
qR : (3, 1, 2/3)
lR : (1, 1, -1)
yR =
yR =
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7. ¿Why 331?
From cancelation of Chiral Anomalies and asymptotic freedom, the
number of families should be 3
The third family is different from the two first, which could explain
why the t and b quarks are so heavy (hierarchy problem)
Predict the quantization of electric charge and the vector nature of EM.
Contains a natural Peccei-Quinn symmetry
New types of matter relevant at LHC
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8. Fermion Structure (3 flias.)
If b = -1/ 3:
QE = EL = (nR) c
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9. Neutral
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10. Neutral Currents
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11. Cross section for pp Z’ f f
Z’ at Tevatron
Cross section for pp Z’ f f
fq/A : PDFs,
GZ’ : Total Z’ width
s : C.M Energy
gv,a : Z’ couplings
y : rapidity
pz : long. momentum
E: total energy
: Scattering angle
M = Mff : invariant mass
xA,B : momentum fractions
K(M) : QED and QCD corrections
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12. At NWA aproximation: (GZ’/MZ’) << 1
Z’ at Tevatron 2
At NWA aproximation: (GZ’/MZ’) << 1
Branching ratio
Total Z’ production cross section
331 model with b = -1/ 3 : 2
- 4
( Gz’ / Mz’ ) ~ 4 x 10
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13. Z’ at Tevatron Kinematics at CDF II -
pp collisions at C.M. energy s = 1.96 TeV,
Integrated Luminosity = 1.3 fb
Azimuthally and F-B symmetric,
Search for Z’ in the channel qq Z’ e e
Events with invariant mass Mee > 200 GeV/c + - -1 2
Central Calorimeter with pseudorapidity h < 1.1
Plug Calorimeter with pseudorapidity 1.2 < h < 3.6,
Transverse energy ET > 25 GeV.
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14. MZ’ > 920 GeV Z’ at Tevatron Z’SM Z’y Z’h Z’c Z’331 923 822 891 920
95% C.L.
Bounds
Z’-models
331
(CalcHep Package)
Z’SM
Z’y
Z’h
Z’c
Z’331
923
822
891
920
T. Aaltonen et.al. (CDF Collaboration),
Phys. Rev. Lett. 99, (2007)
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15. Z’ at LHC Kinematics at ATLAS -
pp collisions at C.M. energy s = 14 TeV,
Integrated Luminosity = 100 fb
Azimuthally and F-B symmetric,
Search for Z’ in the channel qq Z’ e e -1 + -
Pseudorapidity h < 2.5
Transverse energy ET > 20 GeV.
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16. Z’ at LHC
for Mz’ = 1500 GeV
N = s.L

17. Z’ at LHC N = s.L LHC Projections for 1 TeV < MZ’ < 5 TeV Z’331
Z’LR
Z’c
Z’h
Z’Y
SM bkg
N = s.L

18. Conclusions
For 331 model with b = -1/ 3, we get the limit Mz’331 > 920 GeV at
95% C.L in Tevatron
For Mz’ = 1500 GeV, we get about 800 events for each 20 GeV of
energy with L = 100 fb at LHC
At Mz’ = 1 TeV we found ~ events with low expected SM bcg
The model pull the LHC dicovery potential up to 5 TeV, with 1 event -1

19. Prospects Calculations for other 331 models and other Mz’ limits
Effects of exotic decay modes as fermions, charged heavy
bosons, higss, etc (smaller branching ratios)
Effects on the lepton F-B Asymmetries
Extension to ILC

20. Back silides

21. SU(3)L X U(1)X c SU(2)L X U(1)Y h,r U(1)Q
Scalar Structure (3 tripletes)
SU(3)L X U(1)X c
SU(2)L X U(1)Y
h,r
U(1)Q
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22. SU(3)L X U(1)X 8 Gauge Bosons 1 Gauge Boson
Vector Structure (9 campos)
SU(3)L X U(1)X
8 Gauge Bosons
1 Gauge Boson
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23. Charged
Neutral
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