Disentangling the Origins of New Gauge Bosons at the ILC S. Godfrey, Carleton University Workshop on...

Disentangling the Origins of New Disentangling the Origins of New Gauge Bosons at the ILCGauge Bosons at the ILC

S. Godfrey, S. Godfrey, Carleton UniversityCarleton University

Workshop on Possible Parity Restoration at High Energy Jun. 11-12, 2007, IHEP, Beijing

S. Godfrey, Carleton University Disentangling the Origins of New Gauge Bosons at the ILC 2

OutlineOutline

•Models of new physics•Discovery and Identification at the LHC•Z’ Discovery and identification at the ILC•W’ Discovery and identification at the ILC•Final Comments

References:G. Weiglein et al. [LHC/LC Study Group] Phys. Rept. 426, 47 (2006) [hep-ph/0410364]TESLA TDR hep-ph/0106315 A. Leike, Phys. Rept. 317, 143 (1999) [hep-ph/9805494]M. Cvetic and S. Godfrey, hep-ph/9504216


Many Models of New PhysicsMany Models of New Physics

Extended gauge sectorsExtended gauge sectors•Extra U(1) factors:•Left-Right symmetric model:•“Un-unified” Model:

•Little HiggsLittle Higgs

•TopcolourTopcolour

•Extra dimensions (ADD, RS, UED…): KK Extra dimensions (ADD, RS, UED…): KK excitationsexcitations

•ADD: Graviton tower exchange effective operators:•Randall-Sundrum Gravitons: Discrete KK graviton Randall-Sundrum Gravitons: Discrete KK graviton spectrumspectrum•Ununified Extra Dimensions (UED)Ununified Extra Dimensions (UED)

Many, many modelsMany, many models


Left Right Symmetric ModelsLeft Right Symmetric Models

Expect:•Higgs Multiplets with an expanded Higgs sector, eg •Extra Gauge Bosons:

depends on Higgs content of the model with =1 for Higgs doublets and =2 for Higgs triplets

Will focus on phenomenology of gauge bosons

see Mohapatra Raychaudhuri Martins Simoes

Wu


•The little Higgs models are a new approach to stabilize the weak scale against radiative corrections

Little Little HiggsHiggs

Arkani-Hamed et al hep-ph/0206021

10 TeV

1 TeV

100 GeV

New Strong DynamicsGlobal Symmetry

Symmetries BrokenPseudo-Goldstone ScalarsNew Gauge Bosons related to SU(2):New Heavy Top cancels quadratic divergences

Light Higgs SM vector bosons & fermions

Han, Logan, McElrath, Wang, Phys.Rev.D67:095004,2003. [hep-ph/0301040]Han, Logan, Wang, JHEP 0601:099,2006. [hep-ph/0506313]

•Need to experimentally identify the little Higgs Mechanism•Also need to identify the particular little Higgs model

•Study properties of


Un-Unified Model:•Left handed Quarks and Leptons transform as doublets under separate SU(2) groups•qR and lR are singlets under both SU(2)q and SU(2)l

•Parametrize by - the mixing angle of charged gauge bosons

3rd Family Model:•Quarks and Leptons of 3rd family transform as doublets under a separate SU(2)h group

Effective Rank 5 E6 Model:

Many Other Many Other Models:Models:

Georgi, Jenkins, Simmons, PRL 62, 2789 (1989)Barger, Rizzo PL B206, 133 (1988)


What do these models have in What do these models have in common?common?

Spin 1 appear in many models:• Z’ in string inspired models• Z’, W’ in extended gauge sectors• ZR, WR in left-right symmetric models• ZKK, KK, WKK, in theories with extra dimensions• ZH, WH in Little Higgs Models

Also possible higher spin states:• Gravitons in theories with extra dimensions• String resonances

And scalar states:• Radions• Graviscalars

They all have new s-channel structure at ~TeV scale


•Likely that discoveries at the LHC will get us started•But will need the ILC to discriminate between models

Possible Routes:•Direct Discovery•Indirect discovery assuming specific models•Indirect tests of New Physics via Leff

Tools:•Di-fermion channel•Anomalous gauge boson couplings•Anomalous fermion couplings•Higgs couplings

•How do we discover the new physics? How do we discover the new physics? •How do we identify the new physics?How do we identify the new physics?


Z’ production

New Z’ Gauge Bosons at the New Z’ Gauge Bosons at the LHC:LHC:

[T. Martin]

p

p

q

b

µ+

µ-

, Z0, Z’

Di-lepton Resonance Di-lepton Resonance SearchSearch

•Select 2 opposite sign high pT

isolated leptons and examine invariant mass distribution•If you find a peak:

•quantify its significance•Measure its x BR


•If you don’t:•Derive upper limit on x BR •Constrain models

Di-lepton Resonance Di-lepton Resonance SearchSearch


SLH

KK

LH

Z’ production

Discovery Limits for Z’ Gauge Bosons Discovery Limits for Z’ Gauge Bosons at the LHCat the LHC

[Godfrey hep-ph/0201093 ]


LHC Discovers dilepton s-channel LHC Discovers dilepton s-channel Resonance !!Resonance !!

Eureka!

May be seen very early: first weeks

What is it? Many possibilities for s-channel resonance

See Brooijmans


How do we distinguish them?How do we distinguish them?

Assume the LHC discovers a single heavy resonance

Tools to determine what it is:•Cross sections & Widths•Angular Distributions•Couplings (decays, polarization…)


LHC can give some information:LHC can give some information:

Z’:

Rizzo, hep-ph/0305077

Invariant Mass Distributions:Invariant Mass Distributions:

[Azuelos et al, hep-ph/0402037]

Z’ production


Forward Backward AsymmetriesForward Backward Asymmetries

Dittmar, Nicollerat, Djouadi, hep-ph/0307020

LHC can resolve to some extentHan, Logan, Wang, JHEP 0601:099,2006.

[hep-ph/0506313]


What about the ILC?What about the ILC?

Advantages of ILC

•Precision•well defined energy •well known initial state•High luminosity•Excellent particle ID•Clear event signatures

•Polarization of e-, e+ gives helicity information•e and options also being considered

•New resonances lead to new s- and t-channel contributions•ILC is the ideal facility to measure this


MZ’=750 GeVZ

ZLR

ZALR

ee++ee--ffff

-ef+


Many observables:

•Sensitive to flavour•Sensitive to helicity


Numerous difermion observablesNumerous difermion observables18 di-fermion observables:


Discovery vs ExclusionDiscovery vs Exclusion

2 Exclusion Limits (95% C.L.) 2 vs 5 Limits


Dependence on measurement precisionDependence on measurement precision

[From TESLA TDR]


95% C.L. bounds

L=1 ab-1 L=0.2%, P-=0.8, P+=0.6, P=0.5%

Extraction of Z’ couplings assuming MZ’ is known from LHC

Z’ IdentificationZ’ Identification

Note sign ambiguity

S. Riemann: TESLA TDR & LHC/LC Study


What else can we learn? What else can we learn?

Godfrey, Kalyniak, Tomkins hep-ph/0511335


The Importance of PolarizationThe Importance of Polarization

•No polarization•Only electron •electron & positron


What happens for higher mass?What happens for higher mass?


How does it change with more How does it change with more observables?observables?


What happens with higher energy?What happens with higher energy?


•If the Z’ is too heavy •Or if couplings to quarks small

•The distance from the SM helps determine the model and the mass

•Measurement at several s to disentangle mass and couplings

L=1ab-1

L=50fb-1

What happens if Z’ not detected at LHC?What happens if Z’ not detected at LHC?

S. Riemann


Off Resonance: Interference of exchange of virtual graviton KK states with SM amplitudes

Leads to deviations in dependent on both and s/MH

Indirect Signatures for GravitonsIndirect Signatures for Gravitons

SM

Hewett, hep-ph/9811356 Hewett, hep-ph/9811356

Can use multipole moments to distinguish spin 2 from spin 1

Rizzo: hep-ph/0208027


Search and Identification of W’Search and Identification of W’

•Limits from LHC up to ~5.9 TeV assuming SM strength couplings•But very model dependent

In e+e- consider two processes:


In e+e- :

Search and Identification of W’Search and Identification of W’

Kinematic cuts to reflect detector acceptance:

Radiative Bhabba-scatter with e lost down beam:

Where mrad is minimum angle for veto detector

SG, Kalyniak, Kamal, Leike, PR D61, 113009 (2000)


Sensitive to W’ but also to Z’

Peaks are due to Z’

+


d/dEdepends on W’ model sensitivity to W’

LRM

SSM(W’+Z’)KK

eL eR


•Limits not competitive with LHC

•But if LHC discovers them can measure their couplings


Constraints on Couplings: Z’ Constraints on Couplings: Z’

Includes systematic errors


Constraints on Couplings: W’Constraints on Couplings: W’ee


Varying MVarying MW’W’


•No Z’ in process to complicate picture•Sensitive to both q and l couplings•Can enhance t-channel exchange by imposing cut that q is collinear to beam •Can then approximate with simpler process•Results are consistent with exact calculation•Convolute with either WW or backscattered laser spectrum

SG, Kalyniak, Kamal, Doncheski, PR D63, 053005 (2001)


SM, LRUUM

KKSSM

MW’=750 GeV

Backgrounds: 2 jets with one lost down the beam

Can be eliminated with:

SM


Exclusion Limits for W’ using Exclusion Limits for W’ using eeqqqq

•At s=500 GeV, in general not competitive with LHC•LR model already ruled out by Tevatron•Higher limits from e mode argument for ecollider •At s=1 TeV KK, UUM, and SSM competitive or surpass LHC

e+e-

e


Constraints on W’ couplings from Constraints on W’ couplings from eeqqqq•Assume W’ discovered at LHC•Results for backscattered laser mode•95% C.L. contours

SSM

KK

LR

SMKK

SSM

LR


SummarySummary•Extra gauge bosons are a feature of many theories of physics Beyond the Standard Model

•If the LHC discoveries such a state the ILC will be an extremely powerful tool for disentangling it’s origins

•Depending on MZ’ the ILC would be able to determine the origins of the Z’ and determine if it arose from Parity Restoration at high energy

•Precision measurements of ILC crucial for this:•Many independent observables give high resolving power•Polarization to study different helicities


Measuring Little Higgs ParametersMeasuring Little Higgs Parameters

MH not known from LHC

s’ fixed

J. Conley, M.P. Le, J. Hewett


Follows del Aguila, Cvetic and Langacker, PR D48 R969 (1993)Godfrey & Cvetic, [hep-ph/9504216]

Disentangling the Origins of New Gauge Bosons at the ILC S. Godfrey, Carleton University Workshop on...

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