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**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 II LAWHEP São Miguel das Missões, Dec. 2007

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**Outlines Motivations Z’ Basics: Theoretical and experimental facts**

The 331 Model Z’ Production at Tevatron Z’ Production at LHC Conclusions and Prospects II LAWHEP São Miguel das Missões, Dec. 2007

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¿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 II LAWHEP São Miguel das Missões, Dec. 2007

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**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. II LAWHEP São Miguel das Missões, Dec. 2007

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**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 II LAWHEP São Miguel das Missões, Dec. 2007

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**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 = II LAWHEP São Miguel das Missões, Dec. 2007

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¿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 II LAWHEP São Miguel das Missões, Dec. 2007

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**Fermion Structure (3 flias.)**

If b = -1/ 3: QE = EL = (nR) c II LAWHEP São Miguel das Missões, Dec. 2007

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Neutral II LAWHEP São Miguel das Missões, Dec. 2007

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Neutral Currents II LAWHEP São Miguel das Missões, Dec. 2007

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**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 II LAWHEP São Miguel das Missões, Dec. 2007

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**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 II LAWHEP São Miguel das Missões, Dec. 2007

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**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. II LAWHEP São Miguel das Missões, Dec. 2007

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**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) II LAWHEP São Miguel das Missões, Dec. 2007

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**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. II LAWHEP São Miguel das Missões, Dec. 2007

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Z’ at LHC for Mz’ = 1500 GeV N = s.L

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**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

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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

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**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

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Back silides

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**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 II LAWHEP São Miguel das Missões, Dec. 2007

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**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 II LAWHEP São Miguel das Missões, Dec. 2007

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Charged Neutral II LAWHEP São Miguel das Missões, Dec. 2007

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