Anomalous Top Couplings in Whizard in Whizard Fabian Bach in - - PowerPoint PPT Presentation

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Anomalous Top Couplings in Whizard in Whizard Fabian Bach in collaboration with Thorsten Ohl Institut fr Theoretische Physik und Astrophysik, Uni Wrzburg Terascale Alliance Annual Workshop, DESY Hamburg, 04.12.2012 funded by: Outline

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SLIDE 1

Anomalous Top Couplings in Whizard in Whizard

Fabian Bach

in collaboration with Thorsten Ohl

Institut für Theoretische Physik und Astrophysik, Uni Würzburg Terascale Alliance Annual Workshop, DESY Hamburg, 04.12.2012

funded by:

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SLIDE 2

Outline

  • 1. Motivation
  • 2. Anomalous tbW Couplings

Outline

  • 2. Anomalous tbW Couplings
  • 3. Single Top Cross Sections
  • 4. Conclusions
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SLIDE 3

1 Motivation

Phenomenological studies on anomalous top couplings

  • idea:

use the large statistics at LHC to constrain trilinear top couplings to vector bosons with previously unknown precision model-independent effective approach to parameterize any new physics

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SLIDE 4

1 Motivation

Phenomenological studies on anomalous top couplings

  • idea:

use the large statistics at LHC to constrain trilinear top couplings to vector bosons with previously unknown precision model-independent effective approach to parameterize any new physics example: tbW coupling SM ~ γµ(1-γ5)

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SLIDE 5

1 Motivation

Phenomenological studies on anomalous top couplings

  • idea:

use the large statistics at LHC to constrain trilinear top couplings to vector bosons with previously unknown precision model-independent effective approach to parameterize any new physics example: tbW coupling SM

  • ff-resonant

new physics + ~ γµ(1-γ5) e.g. ~ σµνqν(1+γ5)

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SLIDE 6

1 Motivation

Phenomenological studies on anomalous top couplings

  • idea:

use the large statistics at LHC to constrain trilinear top couplings to vector bosons with previously unknown precision model-independent effective approach to parameterize any new physics

  • what has been done:

theoretical understanding of the relations and redundancies among different operators in a full gauge invariant operator set generating the different operators in a full gauge invariant operator set generating the various anomalous trilinear top couplings plethora of pheno & exp. studies, e.g. anomalous QCD and tbW couplings

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SLIDE 7

1 Motivation

Phenomenological studies on anomalous top couplings

  • idea:

use the large statistics at LHC to constrain trilinear top couplings to vector bosons with previously unknown precision model-independent effective approach to parameterize any new physics

  • what has been done:

theoretical understanding of the relations and redundancies among different operators in a full gauge invariant operator set generating the different operators in a full gauge invariant operator set generating the various anomalous trilinear top couplings plethora of pheno & exp. studies, e.g. anomalous QCD and tbW couplings

  • what we want to contribute:

provide all possible anomalous top couplings in one exhaustive MC tool,

  • i. e. Whizard 2 with anomalous tops

automatically ensure gauge invariance for all hard amplitudes relevant for detector level, including off-shell top production and subsequent decays link to hadron shower/fragmentation to produce detector-relevant final states do some phenomenological studies at LHC & ILC

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SLIDE 8
  • parameterization of the vertex:

Studies on anomalous tbW couplings

2 Anomalous tbW couplings

SM: VL = Vtb ≈ 1, VR = gL = gR = VL

  • ff = 0
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SLIDE 9
  • parameterization of the vertex:

Studies on anomalous tbW couplings

SM: VL = Vtb ≈ 1, VR = gL = gR = VL

  • ff = 0

2 Anomalous tbW couplings

usual on-shell parameterisation

  • cf. e.g. [Aguilar-Saavedra et al. 07-09]
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SLIDE 10
  • parameterization of the vertex:

Studies on anomalous tbW couplings

just another way of writing a ffff

SM: VL = Vtb ≈ 1, VR = gL = gR = VL

  • ff = 0

2 Anomalous tbW couplings

usual on-shell parameterisation

  • cf. e.g. [Aguilar-Saavedra et al. 07-09]

just another way of writing a ffff contact interaction (generated by the effective operator basis and not entirely redundant)

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SLIDE 11
  • parameterization of the vertex:

Studies on anomalous tbW couplings

SM: VL = Vtb ≈ 1, VR = gL = gR = VL

  • ff = 0

2 Anomalous tbW couplings

just another way of writing a ffff usual on-shell parameterisation

  • cf. e.g. [Aguilar-Saavedra et al. 07-09]

Luckily we have implemented the full package in

Whizard 2 Whizard 2 Whizard 2 Whizard 2

Including all tbW, ttZ, ttA and ttg couplings!

just another way of writing a ffff contact interaction (generated by the effective operator basis and not entirely redundant)

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SLIDE 12
  • different types of single top production considered

1) t-channel tj + tbj production: 3 Single top cross sections

Single top cross sections: partonic production matrix elements

2) s-channel tb production: 3) tW production:

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SLIDE 13

not included

3 Single top cross sections

  • different types of single top production considered contact terms

1) t-channel tj + tbj production:

Single top cross sections: partonic production matrix elements

not included redundant

[AS et al. 09]

2) s-channel tb production: 3) tW production:

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SLIDE 14
  • basic idea to efficiently derive bounds from cross section measurements:

cross section σdet of a given final state selection i (detector level) with j partonic input processes

Single top cross sections

3 Single top cross sections with j partonic input processes εij detector transfer matrix (from fast detector simulation)

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SLIDE 15
  • basic idea to efficiently derive bounds from cross section measurements:

cross section σdet of a given final state selection i (detector level) with j partonic input processes

Single top cross sections

3 Single top cross sections with j partonic input processes εij detector transfer matrix (from fast detector simulation)

  • caveat: couplings might affect differential distributions, so where do we put

the detector acceptance Φ, into the (g-dependent) σpart or the (g-constant) ε?

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SLIDE 16
  • basic idea to efficiently derive bounds from cross section measurements:

cross section σdet of a given final state selection i (detector level) with j partonic input processes

Single top cross sections

3 Single top cross sections with j partonic input processes εij detector transfer matrix (from fast detector simulation)

  • caveat: couplings might affect differential distributions, so where do we put

the detector acceptance Φ, into the (g-dependent) σpart or the (g-constant) ε?

  • nomenclature:
  • n-shell approach

e.g. [Aguilar-Saavedra ‘08]

full matrix element (ME) approach

[FB, T Ohl ‘12]

(explanation follows…)

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SLIDE 17
  • typical matrix element (e.g. s-channel):

Single top cross sections

3 Single top cross sections

gj 2 gi ~ f(gi,gj) ?

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SLIDE 18
  • typical matrix element (e.g. s-channel):

Single top cross sections

3 Single top cross sections

gj 2 gi ~ f(gi,gj) ?

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SLIDE 19
  • typical matrix element (e.g. s-channel):

Single top cross sections

3 Single top cross sections

gj 2 gi ~ gi

2 !!!

Narrow Width Approximation at work: ME ~ order 2 polynomial in g

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SLIDE 20
  • typical matrix element (e.g. s-channel):

Single top cross sections

3 Single top cross sections

gj 2 gi ~ gi

2 !!!

Narrow Width Approximation at work: ME ~ order 2 polynomial in g

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SLIDE 21
  • typical matrix element (e.g. s-channel):

Single top cross sections

3 Single top cross sections

gj 2 gi ~ gi

2 ?

Narrow Width Approximation at work: ME ~ order 2 polynomial in g

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SLIDE 22

Single top cross sections

3 Single top cross sections

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SLIDE 23

Single top cross sections

3 Single top cross sections

full phase space

full matrix element (ME) approach

[FB, T Ohl ‘12]

  • n-shell approach

e.g. [Aguilar-Saavedra ‘08]

full phase space

Φdet

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SLIDE 24

Single top cross sections

3 Single top cross sections

full phase space

full matrix element (ME) approach

[FB, T Ohl ‘12]

  • n-shell approach

e.g. [Aguilar-Saavedra ‘08]

full phase space

Φdet Φpart

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SLIDE 25

Single top cross sections

3 Single top cross sections

full phase space

full matrix element (ME) approach

[FB, T Ohl ‘12]

  • n-shell approach

e.g. [Aguilar-Saavedra ‘08]

full phase space

Φdet Φpart ε

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SLIDE 26

Single top cross sections

3 Single top cross sections

full phase space

full matrix element (ME) approach

[FB, T Ohl ‘12]

  • n-shell approach

e.g. [Aguilar-Saavedra ‘08]

full phase space

Φdet Φpart ε

NWA applies, decay insertions cancel: pro: κ ~ order 2 polynomial in g fast con: neglects non-SM distributions

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SLIDE 27

Single top cross sections

3 Single top cross sections

full phase space

full matrix element (ME) approach

[FB, T Ohl ‘12]

  • n-shell approach

e.g. [Aguilar-Saavedra ‘08]

full phase space

Φdet Φpart ε

con: κ ~ Monte Carlo scan over g slow pro: accounts for non-SM distributions NWA applies, decay insertions cancel: pro: κ ~ order 2 polynomial in g fast con: neglects non-SM distributions

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SLIDE 28

Single top cross sections

3 Single top cross sections

full phase space

full matrix element (ME) approach

[FB, T Ohl ‘12]

  • n-shell approach

e.g. [Aguilar-Saavedra ‘08]

full phase space

Φdet Φpart ε

con: κ ~ Monte Carlo scan over g slow pro: accounts for non-SM distributions NWA applies, decay insertions cancel: pro: κ ~ order 2 polynomial in g fast con: neglects non-SM distributions

compare!

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SLIDE 29
  • different types of single top production considered

contact terms 1) t-channel tj + tbj production:

included

3 Single top cross sections

Partonic matrix elements [FB, T Ohl ‘12]

2) s-channel tb production: 3) tW production: not included, because it‘s conceptually hard to model Φpart and stay inclusive w.r.t. s & t channels remove huge ttbar in the tWb matrix element

included

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SLIDE 30
  • different types of single top production considered

contact terms 1) t-channel tj + tbj production:

included

3 Single top cross sections

Partonic matrix elements [FB, T Ohl ‘12]

2) s-channel tb production: define partonic acceptance cuts Φpart :

included

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SLIDE 31
  • assume that the on-shell approximation holds

quadratic fits to κfull(g), e.g. for t-channel production: 3 Single top cross sections

Comparison of detector acceptance and full phase space

κ(VR

2)

Φpart ~ detector acceptance Φpart = full phase space VL

  • n-shell result
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SLIDE 32
  • assume that the on-shell approximation holds

quadratic fits to κfull(g), e.g. for t-channel production: 3 Single top cross sections

Comparison of detector acceptance and full phase space

κ(VR

2)

Φpart ~ detector acceptance Φpart = full phase space VL VL κ(gL

2)

κ(VRgL) VL

  • n-shell result
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SLIDE 33
  • set ε = 1 and plot |κfull - κon| in various anomalous coupling planes

to be compared with exp. sensitivities of ~14 % (tj sel.) resp. ~20 % (tb sel.) 3 Single top cross sections

Comparison of partonic ME response κon and κfull

tj tbj VL – VR plane

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SLIDE 34

3 Single top cross sections

Comparison of partonic ME response κon and κfull

tj

  • set ε = 1 and plot |κfull - κon| in various anomalous coupling planes

to be compared with exp. sensitivities of ~14 % (tj sel.) resp. ~20 % (tb sel.) tbj VL – VR plane

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SLIDE 35

3 Single top cross sections

Comparison of partonic ME response κon and κfull

tj

  • set ε = 1 and plot |κfull - κon| in various anomalous coupling planes

to be compared with exp. sensitivities of ~14 % (tj sel.) resp. ~20 % (tb sel.) tbj VL – VR plane VR – gL plane

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SLIDE 36

3 Single top cross sections

Comparison of partonic ME response κon and κfull

tj

  • set ε = 1 and plot |κfull - κon| in various anomalous coupling planes

to be compared with exp. sensitivities of ~14 % (tj sel.) resp. ~20 % (tb sel.) tbj VL – VR plane VR – gL plane gL – gR plane

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SLIDE 37

3 Single top cross sections

Comparison of partonic ME response κon and κfull

tj

  • set ε = 1 and plot |κfull - κon| in various anomalous coupling planes

to be compared with exp. sensitivities of ~14 % (tj sel.) resp. ~20 % (tb sel.) tbj largest discrepancy along momentum-dependent couplings gL,R

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SLIDE 38
  • set ε = εDet and plot 1σ combined limits in the gL – gR plane (VL = 1, VR = 0)

3 Single top cross sections

Comparison of detector level limits

qualitatively different limits in the s and t channel combination

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SLIDE 39

3 Single top cross sections

Comparison of detector level limits

  • set ε = εDet and plot 1σ combined limits in the gL – gR plane (VL = 1, VR = 0)

R observable appears to relax the discrepancy …

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SLIDE 40

3 Single top cross sections

Comparison of detector level limits

  • set ε = εDet and plot 1σ combined limits in the gL – gR plane (VL = 1, VR = 0)

… but this depends heavily on the exp. uncertainty of R

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SLIDE 41

Conclusions

  • abundant top production at the LHC

high statistics allows for precise measurements of top couplings etc. look for deviations from SM in the min. set of trilinear top couplings tfV, ttH gauge invariance & consistency requires quartic terms (e.g. ttgg, 4-fermion) 4 Conclusions

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SLIDE 42

Conclusions

  • abundant top production at the LHC

high statistics allows for precise measurements of top couplings etc. look for deviations from SM in the min. set of trilinear top couplings tfV, ttH gauge invariance & consistency requires quartic terms (e.g. ttgg, 4-fermion)

  • the Whizard

Whizard Whizard Whizard 2 2 2 2 front all anomalous trilinear top couplings and associated contact terms at hand implementation validated @ 22 4 Conclusions implementation validated @ 22 importance of off-shell effects illustrated

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SLIDE 43

Conclusions

  • abundant top production at the LHC

high statistics allows for precise measurements of top couplings etc. look for deviations from SM in the min. set of trilinear top couplings tfV, ttH gauge invariance & consistency requires quartic terms (e.g. ttgg, 4-fermion)

  • the Whizard

Whizard Whizard Whizard 2 2 2 2 front all anomalous trilinear top couplings and associated contact terms at hand implementation validated @ 22 4 Conclusions implementation validated @ 22 importance of off-shell effects illustrated

  • physics results

crucial to adapt the partonic ME integration to the final state selection in order to get the ME response to anomalous couplings right

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SLIDE 44

Conclusions

  • abundant top production at the LHC

high statistics allows for precise measurements of top couplings etc. look for deviations from SM in the min. set of trilinear top couplings tfV, ttH gauge invariance & consistency requires quartic terms (e.g. ttgg, 4-fermion)

  • the Whizard

Whizard Whizard Whizard 2 2 2 2 front all anomalous trilinear top couplings and associated contact terms at hand implementation validated @ 22 4 Conclusions implementation validated @ 22 importance of off-shell effects illustrated

  • physics results

crucial to adapt the partonic ME integration to the final state selection in order to get the ME response to anomalous couplings right careful when mapping cross section measurements onto effective operator coefficients: in general, there are more parameters than just the set of anomalous trilinear tbW couplings (cf. VL

  • ff)
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SLIDE 45

Conclusions

  • abundant top production at the LHC

high statistics allows for precise measurements of top couplings etc. look for deviations from SM in the min. set of trilinear top couplings tfV, ttH gauge invariance & consistency requires quartic terms (e.g. ttgg, 4-fermion)

  • the Whizard

Whizard Whizard Whizard 2 2 2 2 front all anomalous trilinear top couplings and associated contact terms at hand implementation validated @ 22 4 Conclusions implementation validated @ 22 importance of off-shell effects illustrated

  • physics results

crucial to adapt the partonic ME integration to the final state selection in order to get the ME response to anomalous couplings right careful when mapping cross section measurements onto effective operator coefficients: in general, there are more parameters than just the set of anomalous trilinear tbW couplings (cf. VL

  • ff)

Thank you!

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SLIDE 46

Backup: contact term unitarity

Unitarity bound on the contact coupling size

  • perform a partial-wave analysis on the ffff contact diagram
  • depending on input pdf‘s, infer unitarity limit on the coupling strength

~C/Λ2, in terms of VL

  • ff

0.5 0.6 a L L 2 L 1 L 0 3.5 4.0 s

crit TeV

2 0.1 7 TeV s

crit

0.5 1.0 1.5 2.0 s TeV 0.1 0.2 0.3 0.4 a L 1 2 L 2 0.0 0.2 0.4 0.6 0.8 1.0 V L

  • ff

1.0 1.5 2.0 2.5 3.0 .5 2 0.1 14 TeV 2 0.1 7 TeV

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SLIDE 47

Backup: contact term unitarity

Unitarity bound on the contact coupling size

0.5 0.6 a L L 2 L 1 L 0 3.5 4.0 s

crit TeV

2 0.1 7 TeV s

crit

  • perform a partial-wave analysis on the ffff contact diagram
  • depending on input pdf‘s, infer unitarity limit on the coupling strength

~C/Λ2, in terms of VL

  • ff

LHC @ 7 TeV: VL

  • ff < 0.75

LHC @ 14 TeV: VL

  • ff < 0.25 (exp. sensitivity ~ 0.05 @ 10 fb-1)

0.5 1.0 1.5 2.0 s TeV 0.1 0.2 0.3 0.4 a L 1 2 L 2 0.0 0.2 0.4 0.6 0.8 1.0 V L

  • ff

1.0 1.5 2.0 2.5 3.0 .5 2 0.1 14 TeV 2 0.1 7 TeV

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SLIDE 48

Whizard Whizard Whizard Whizard validation

Backup: Whizard validation

  • independent validation of Whizard 2:

compute partonic s channel production u dbar t bbar analytically (no cuts) get the κ‘s and compare to W2‘s numerical results as a function of √s

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SLIDE 49
  • independent validation of Whizard 2:

compute partonic s channel production u dbar t bbar analytically (no cuts) get the κ‘s and compare to W2‘s numerical results as a function of √s Backup: Whizard validation

Whizard Whizard Whizard Whizard validation

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SLIDE 50

Backup: Whizard validation

  • independent validation of Whizard 2:

compute partonic s channel production u dbar t bbar analytically (no cuts) get the κ‘s and compare to W2‘s numerical results as a function of √s

Whizard Whizard Whizard Whizard validation

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SLIDE 51

W2 seems to underestimate the numerical error, Backup: Whizard validation

  • independent validation of Whizard 2:

compute partonic s channel production u dbar t bbar analytically (no cuts) get the κ‘s and compare to W2‘s numerical results as a function of √s

Whizard Whizard Whizard Whizard validation

W2 seems to underestimate the numerical error, but looks like stat. fluctuations @ O(10-6)

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SLIDE 52
  • set ε = εDet and plot 1σ combined limits in the VL – VL
  • ff plane

Backup: contact interaction bounds

Include the contact interaction VL

  • ff
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SLIDE 53
  • set ε = εDet and plot 1σ combined limits in the VL – VL
  • ff plane

Include the contact interaction VL

  • ff

Backup: contact interaction bounds

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SLIDE 54
  • set ε = εDet and plot 1σ combined limits in the VL – VL
  • ff plane

Include the contact interaction VL

  • ff

Backup: contact interaction bounds

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SLIDE 55
  • set ε = εDet and plot 1σ combined limits in the VR – gL plane

Include the contact interaction VL

  • ff

Backup: contact interaction bounds

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SLIDE 56
  • set ε = εDet and plot 1σ combined limits in the VR – gL plane

Include the contact interaction VL

  • ff

Backup: contact interaction bounds

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SLIDE 57
  • set ε = εDet and plot 1σ combined limits in the VR – gL plane

Include the contact interaction VL

  • ff

Backup: contact interaction bounds