universidad nacional de colombia departamento de física ii lawhep são miguel das missões, dec....

Universidad Nacional de ColombiaUniversidad Nacional de Colombia

Departamento de FísicaDepartamento de Física

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São Miguel das MissõesSão Miguel das Missões, , Dec. 2007Dec. 2007

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Grupo de Física Teórica de Altas EnergíasGrupo de Física Teórica de Altas Energías

Z’ Production in 331 modelsZ’ Production in 331 models

Fredy A. Ochoa and Roberto Martínez

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• Motivations Motivations

• Z’ Basics: Theoretical and experimental factsZ’ Basics: Theoretical and experimental facts

• The 331 ModelThe 331 Model

• Z’ Production at TevatronZ’ Production at Tevatron

• Z’ Production at LHCZ’ Production at LHC

• Conclusions and ProspectsConclusions and Prospects

OutlineOutliness

• The mechanism for breaking the electroweak symmetries andThe mechanism for breaking the electroweak symmetries and generating massgenerating mass

• The unification of forces, including gravity.The unification of forces, including gravity.

• The conection to cosmology (Baryon asymmetry, Cold Dark The conection to cosmology (Baryon asymmetry, Cold Dark Matter. ) Matter. )

• The mass hierarchy problemThe mass hierarchy problem

• The existence of 3 familiesThe existence of 3 families

• The electric charge quantizationThe electric charge quantization

• The neutrino masses and mixingThe neutrino masses and mixing

¿Why beyond ¿Why beyond SM?SM?

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Z’ Boson Basics:Z’ Boson Basics: Theoretical Theoretical FactsFacts

• An observation of the Z’ would provide information on the GUT groupAn observation of the Z’ would provide information on the GUT group and on its symmetry breakingand on its symmetry breaking..

• A Z’ particle is a neutral, spin-1, colorless and self-adjoint gauge bosonA 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 thearising from some extensions of the SM, which is more massive than the

SM Z boson.SM Z boson.

• Z’-models: +U(1) from E6, Left-Right, Little Higgs, Sequential SM, 331Z’-models: +U(1) from E6, Left-Right, Little Higgs, Sequential SM, 331

• Z and Z’ bosons are not true mass eigenstates. The physical bosons areZ and Z’ bosons are not true mass eigenstates. The physical bosons are

mixing states Zmixing states Z11 and Z and Z22 with a mixing angle with a mixing angle , which cause deviations from, which cause deviations from the SM (Z-pole parameters, shifts in the W couplings, shifts in the Weakthe SM (Z-pole parameters, shifts in the W couplings, shifts in the Weak Charge, F-B Asymmetries, etc.)Charge, F-B Asymmetries, etc.)

• The MThe MZZ’ is not constrained by the theory. It can be anywhere between’ is not constrained by the theory. It can be anywhere between

Eweak < MEweak < MZZ’ < E’ < EGUTGUT..

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Z’ Boson Basics:Z’ Boson Basics: Experimental Experimental FactsFacts

• In hadron colliders, the sensitivity to Z’ production decaying intoIn hadron colliders, the sensitivity to Z’ production decaying into

quarks pairs is reduced compared to lepton pairs due to the QCDquarks pairs is reduced compared to lepton pairs due to the QCD backgroundbackground

• A Z’ particle is a resonance, which is more massive than the SM Z,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.observed in the Drell-Yan process pp(pp ) l l + X.

• A Z’ can be directly observed through its decay products. It is possibleA Z’ can be directly observed through its decay products. It is possible

in lepton collisions (ILC) or in hadron collisions (Tevatron, LHC).in lepton collisions (ILC) or in hadron collisions (Tevatron, LHC).

• Present limits from direct production at Tevatron and virtual effects atPresent limits from direct production at Tevatron and virtual effects at

LEP through mixing with the Z boson, imply that MLEP through mixing with the Z boson, imply that MZZ’ ~ TeV and S’ ~ TeV and S ~ 10. ~ 10.

• An observation of a Z’ would serve as a calibration point for futureAn observation of a Z’ would serve as a calibration point for future

detectorsdetectors

-3-3

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¿What is ¿What is 331?331?

F. Pisano and V. Pleitez, Phys. Rev. D46, (1992) 410

P.H. Frampton, Phys. Rev. Lett. 69 (1992) 2889

qqLL : : (3, 3, Xq )(3, 3, Xq )

llLL : : (1, 3, Xl )(1, 3, Xl )

qqLL : : (3, 3, Xq )(3, 3, Xq )

llLL : : (1, 3, Xl )(1, 3, Xl )

SMSMSMSM 3-3-3-3-113-3-3-3-11

qqLL : : (3, 2, 1/6)(3, 2, 1/6)

llLL : : (1, 2, -1/2)(1, 2, -1/2) LL ==

qqRR : : (3, 1, 2/3)(3, 1, 2/3) llRR : : (1, 1, -1)(1, 1, -1)

R R ==

L =L =

qqRR : : (3, 1, X(3, 1, Xqq))

llRR : : (1, 1, Xl)(1, 1, Xl) R R ==

L =L =****

**

**

**

**

**

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¿Why 331?¿Why 331?

• From cancelation of Chiral Anomalies and asymptotic freedom, From cancelation of Chiral Anomalies and asymptotic freedom, thethe number of families should be 3number of families should be 3

• The third family is different from the two first, which could The third family is different from the two first, which could explainexplain why the t and b quarks are so heavy (hierarchy problem)why the t and b quarks are so heavy (hierarchy problem)

• Predict the quantization of electric charge and the vector nature Predict the quantization of electric charge and the vector nature of EM.of EM.

• Contains a natural Peccei-Quinn symmetry Contains a natural Peccei-Quinn symmetry

• New types of matter relevant at LHCNew types of matter relevant at LHC

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Fermion Structure (3 flias.)

If = -1/ 3:QE = 0 EL = (R) c

NeutralNeutral

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Neutral Neutral CurrentsCurrents

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Cross section for pp Z’ f fCross section for pp Z’ f fffq/A q/A : PDFs,: PDFs,

ZZ’ : Total Z’ width’ : Total Z’ width

s : C.M Energys : C.M Energy

ggv,a : v,a : Z’ couplingsZ’ couplings

y : rapidityy : rapidity

ppzz : long. momentum : long. momentum

E: total energyE: total energy

Scattering angleScattering angle

M = MM = Mffff : invariant mass : invariant mass

xxA,BA,B : momentum fractions : momentum fractions

K(M) : QED and QCD K(M) : QED and QCD correctionscorrections

Z’ at Z’ at TevatronTevatron

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At NWA aproximation: (At NWA aproximation: (ZZ’/M’/MZZ’) << 1 ’) << 1 22

Total Z’ production Total Z’ production cross sectioncross section

Branching ratioBranching ratio

331 model with = -1/ 3 :

z’ / Mz’ ) ~ 4 x 10z’ / Mz’ ) ~ 4 x 1022 -- 4 4

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Kinematics at CDF IIKinematics at CDF II

• pp collisions at C.M. energy s = 1.96 TeV,pp collisions at C.M. energy s = 1.96 TeV,

• Integrated Luminosity = 1.3 fbIntegrated Luminosity = 1.3 fb

• Azimuthally and F-B symmetric,Azimuthally and F-B symmetric,

• Search for Z’ in the channel qq Z’ e e Search for Z’ in the channel qq Z’ e e

• Events with invariant mass Mee > 200 GeV/cEvents with invariant mass Mee > 200 GeV/c

++ --

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22

• Central Calorimeter with pseudorapidity Central Calorimeter with pseudorapidity < 1.1 < 1.1

• Plug Calorimeter with pseudorapidity 1.2 < Plug Calorimeter with pseudorapidity 1.2 < < 3.6, < 3.6,

• Transverse energy ETransverse energy ETT > 25 GeV. > 25 GeV.

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MMZZ’ > 920 GeV ’ > 920 GeV

T. Aaltonen et.al. (CDF Collaboration), T. Aaltonen et.al. (CDF Collaboration),

Phys. Rev. Lett. 99, (2007) 171802Phys. Rev. Lett. 99, (2007) 171802

331331(CalcHep Package)(CalcHep Package)Z’Z’SMSM

Z’Z’

Z’Z’

Z’Z’

Z’Z’331331

923923

822822

891891

822822

920920

Z’-modelsZ’-models 95% C.L. 95% C.L. BoundsBounds

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Z’ at Z’ at LHCLHC

Kinematics at ATLASKinematics at ATLAS

• pp collisions at C.M. energy s = 14 TeV,pp collisions at C.M. energy s = 14 TeV,

• Integrated Luminosity = 100 fbIntegrated Luminosity = 100 fb

• Azimuthally and F-B symmetric,Azimuthally and F-B symmetric,

• Search for Z’ in the channel qq Z’ e e Search for Z’ in the channel qq Z’ e e ++ --

-1-1

• Pseudorapidity Pseudorapidity < 2.5 < 2.5

•Transverse energy ETransverse energy ETT > 20 GeV. > 20 GeV.


for Mz’ = 1500 GeVfor Mz’ = 1500 GeV

N = N = LL


LHC Projections for 1 TeV < MZ’ < 5 TeVLHC Projections for 1 TeV < MZ’ < 5 TeV

N = N = LL

Z’331

Z’LR

Z’

Z’

SM bkg

Z’

ConclusioConclusionsns

• For 331 model with For 331 model with = -1/ 3, we get the limit Mz’= -1/ 3, we get the limit Mz’331331 > 920 > 920 GeV atGeV at 95% C.L in Tevatron95% C.L in Tevatron

• For Mz’ = 1500 GeV, we get about 800 events for each 20 GeV For Mz’ = 1500 GeV, we get about 800 events for each 20 GeV

ofof energy with L = 100 fb at LHCenergy with L = 100 fb at LHC

• At Mz’ = 1 TeV we found ~ 10.000 events with low expected SM At Mz’ = 1 TeV we found ~ 10.000 events with low expected SM

bcgbcg

• The model pull the LHC dicovery potential up to 5 TeV, with 1 The model pull the LHC dicovery potential up to 5 TeV, with 1

event event

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ProspectsProspects

• Calculations for other 331 models and other Mz’ limitsCalculations for other 331 models and other Mz’ limits

• Effects of exotic decay modes as fermions, charged heavyEffects of exotic decay modes as fermions, charged heavy bosons, higss, etc (smaller branching ratios)bosons, higss, etc (smaller branching ratios)

• Effects on the lepton F-B Asymmetries Effects on the lepton F-B Asymmetries

• Extension to ILCExtension to ILC

Back Back silidessilides

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Scalar Structure (3 Scalar Structure (3 tripletes)tripletes)

8 Gauge Bosons

1 Gauge Boson

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Vector Structure (9 Vector Structure (9 campos)campos)

NeutralNeutralChargeChargedd

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universidad nacional de colombia departamento de física ii lawhep são miguel das missões, dec....

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