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
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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
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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
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•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
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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)
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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
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•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?
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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
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•If you don’t:•Derive upper limit on x BR •Constrain models
Di-lepton Resonance Di-lepton Resonance SearchSearch
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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 ]
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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
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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…)
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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
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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]
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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
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MZ’=750 GeVZ
ZLR
ZALR
ee++ee--ffff
-ef+
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Many observables:
•Sensitive to flavour•Sensitive to helicity
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Numerous difermion observablesNumerous difermion observables18 di-fermion observables:
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Discovery vs ExclusionDiscovery vs Exclusion
2 Exclusion Limits (95% C.L.) 2 vs 5 Limits
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Dependence on measurement precisionDependence on measurement precision
[From TESLA TDR]
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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
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What else can we learn? What else can we learn?
Godfrey, Kalyniak, Tomkins hep-ph/0511335
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The Importance of PolarizationThe Importance of Polarization
•No polarization•Only electron •electron & positron
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What happens for higher mass?What happens for higher mass?
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How does it change with more How does it change with more observables?observables?
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What happens with higher energy?What happens with higher energy?
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•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
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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
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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:
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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)
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Sensitive to W’ but also to Z’
Peaks are due to Z’
+
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d/dEdepends on W’ model sensitivity to W’
LRM
SSM(W’+Z’)KK
eL eR
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•Limits not competitive with LHC
•But if LHC discovers them can measure their couplings
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Constraints on Couplings: Z’ Constraints on Couplings: Z’
Includes systematic errors
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Constraints on Couplings: W’Constraints on Couplings: W’ee
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Varying MVarying MW’W’
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•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)
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SM, LRUUM
KKSSM
MW’=750 GeV
Backgrounds: 2 jets with one lost down the beam
Can be eliminated with:
SM
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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
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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
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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
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Measuring Little Higgs ParametersMeasuring Little Higgs Parameters
MH not known from LHC
s’ fixed
J. Conley, M.P. Le, J. Hewett
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Follows del Aguila, Cvetic and Langacker, PR D48 R969 (1993)Godfrey & Cvetic, [hep-ph/9504216]