Top/QCD program

(b)

Higher Order EW + QCD

Fixed order vs resummed

• Normalization (and peak position) stabilised by higher orders;– summation of leading logs important– N3LO improves NNLO considerably

Pineda

Instability Effects

• Experimental threshold complicated by beam effects

– Luminosity spectrum

– Absolute beam energy

• Machine parameters (interaction point beam sizes) change beamstrahlung component of luminosity spectrum

• Increase beamstrahlung reduces effective luminosity at threshold

– Small modification to shape

Threshold top quark production

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σ obs s( ) = 1L0

L x( )0

1

∫ σ x s( )dx€

dLd s

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s

Boogert, Gournaris

ILC accelerator parameters• Parameter group question

Is there any impact of decreasing (increasing) beamstrahlung by a factor of two relative to the standard parameters?

• Simulated 5 possible scenariosLow-Q, Nominal, Large-Y, Low-P, High-L

• Simulated using Guinea-Pig– Fitted using CIRCE-like

parameterization

• Total luminosity spectrum also includes– Intrinsic energy spread– Initial state radiation

• Bhabha acolinearity– Theoretical developments

• New 2 loop calculations• Monte Carlo generators

– Beamstrahlung extraction• Statistical error small• Systematic errors being evaluated

Boogert, Gournaris

Projected total top mass error

• Statistical error– Obtained directly from threshold fit

mt(stat-fit) = 100 to 15 MeV– Depends on parameter set

• Theory error (estimate)– From theoretical uncertainty in threshold

cross sectionmt(theory) = 35 MeV

• Absolute beam energy scale– Assumed precision of beam energy

diagnostics 1 part in 104

mt(e-beam) = 35 MeV

• Luminosity spectrum– Beamstrahlung component can be well

measured – K. Mönig & S. Boogert– Systematic error studies ongoing

mt(spectrum) = 2 MeV and 70 MeV

Boogert, Gournaris

At the ILC with , several hundred events are expected. Statistical error is less than 10 %. Therefore the effect of dim.6 couplings can be observed.

– We discuss the W-fusion with the non-SM Yt which are characterized by dim.6 operators.

– They are constrained by experimental data and unitarity.• Our calculations have been checked by ET.• The W-fusion has been analyzed by EWA and CalcHEP.

• Dim.6 couplings can enhance.

Dimension 6 top-Higgs coupling

Conclusion

Koji Tsumura