1. Top Physics at the ILC: A (selective) Review
ILC Physics at Florence, GGI , Sept 12-14, 2007

2. Outline Review of some basic aspects of top physics Top Threshold Scan
Top Pair + Higgs
QCD Factorization for Top Mass Reconstruction
New Physics
EWSB
Precision Test
QCD
ILC Physics at Florence, GGI , Sept 12-14, 2007

3. What we know … Tevatron (Run I+II) Tev, LHC, ILC
Room for “fancy” New Physics ideas
Tev, LHC, ILC
Room for lots of “hard work”
Top quark is SM-like !
ILC Physics at Florence, GGI , Sept 12-14, 2007

4. What ILC can/will do … Tevatron/LHC: ILC:
first incisive tests of SM-top
discovery potential for new physics:
heavy resonances, FCNC decays,..
ILC:
high precision measurements
clean experimental environment
precise theoretical calculations
useful in any future scenario
ILC Physics at Florence, GGI , Sept 12-14, 2007

5. Top at the ILC EWSB New Physics EWSB Higgs mechanism Top Physics
just a heavy quark ?
active role in EWSB ?
constraint on any model
EWSB
Higgs mechanism
Top Physics
Precision Physics
QCD Laboratory
Summation of QCD effects and polarization essential!
2nd part of talk
ILC Physics at Florence, GGI , Sept 12-14, 2007

6. Top at the ILC EWSB New Physics EWSB Higgs mechanism Top Physics
just a heavy quark ?
active role in EWSB ?
constraint on any model
EWSB
Higgs mechanism
Top Physics
Precision Physics
QCD Laboratory
ILC Physics at Florence, GGI , Sept 12-14, 2007

7. Top FCNC’s ILC luminosity range
Any signal clear indication for new physics!
ILC luminosity range
production more sensitive than decay (larger phase space)
beam polarization improves sensitivity for production
ILC Physics at Florence, GGI , Sept 12-14, 2007

8. Top at the ILC Precision Physics: New Physics EWSB Top Physics
top mass essential parameter for testing
small error and precise mass def. needed
EWSB
any model at the quantum level
Top Physics
Precision Physics
QCD Laboratory
more examples see: Heinemeyer etal.
hep-ph/
ILC Physics at Florence, GGI , Sept 12-14, 2007

9. Top at the ILC Top, the QCD laboratory: New Physics EWSB Top Physics
top mass extremely large: short-distance
top width: provides IR cutoff for low-energy
EWSB
processes have well convergent pert. exp.
top quark dynamics
Top Physics
Precision Physics
QCD Laboratory
ILC Physics at Florence, GGI , Sept 12-14, 2007

10. Top at the ILC Top, the QCD laboratory: New Physics EWSB Top Physics
Chetyrkin, Kuhn, Steinhauser Teubner, AH, etal;
Bernreuther etal, Denner, Pozorini etal Penin etal, etc. etc.
Top Physics
Jezabek, Kuhn, etal, Teubner, Stewart, Manohar, AH; Penin etal, Melnikov etal, Beneke, Signer etal, Sumino, Kiyo etal.
Dittmaier etal, Dawson etal,; Denner/Delanger/You etal
Farrell, AH
Precision Physics
QCD Laboratory
ILC Physics at Florence, GGI , Sept 12-14, 2007

11. Top Mass from Threshold Scan
Miquel, Martinez;
Boogert, Gounaris
Threshold Scan
“threshold masses”
Theoretical Tool:
NRQCD sums singularities
ILC Physics at Florence, GGI , Sept 12-14, 2007

12. Top Mass from Threshold Scan
Miquel, Martinez;
Boogert, Gounaris
Threshold Scan
“threshold masses”
Theoretical Tool:
NRQCD
Fixed order pert. theory: LL, NLL NNLL (partly)
Manohar, Stewart, Teubner; Stahlhofen, AH; Pineda, Signer
RGE-improved pert. theory: LO, NLO, NNLO NNNLO (partly)
Teubner AH; Melnikov Yelkovski; Yakovlev; Beneke, Signer Smirnov; Penin, Sumino, Kiyo; Schuller;
ILC Physics at Florence, GGI , Sept 12-14, 2007

13. Top Mass from Threshold Scan
Miquel, Martinez;
Boogert, Gounaris
Threshold Scan
“threshold masses”
Main experimental problem:
monitoring (Babbha)
parametrization
ILC Physics at Florence, GGI , Sept 12-14, 2007

14. Top Mass from Threshold Scan
Miquel, Martinez;
Boogert, Gounaris
Threshold Scan
“threshold masses”
“Official” ILC prospect:
(Top/QCD working groups)
ILC Physics at Florence, GGI , Sept 12-14, 2007

15. Top Mass from Threshold Scan
Miquel, Martinez;
Boogert, Gounaris
Threshold Scan
“threshold masses”
Outlook:
(Top/QCD working groups)
needed for measurements of
completion of NNLL (RGE-improved) and NNNLO (fixed-order) total cross section
Monte-Carlo for top threshold (total cross section + distribution)
finite life-time corrections (non-factorizable, interference, distributions)
application to squark pair production, etc.
ILC Physics at Florence, GGI , Sept 12-14, 2007

16. Top at the ILC Top, the QCD laboratory: New Physics EWSB Top Physics
Chetyrkin, Kuhn, Steinhauser Teubner, AH, etal;
Bernreuther etal, Denner, Pozorini etal Penin etal, etc. etc.
Top Physics
Jezabek, Kuhn, etal, Teubner, Stewart, Manohar, AH; Penin etal, Melnikov etal, Beneke, Signer etal, Sumino, Kiyo etal.
Dittmaier etal, Dawson etal,; Denner/Delanger/You etal
Farrell, AH
Precision Physics
QCD Laboratory
ILC Physics at Florence, GGI , Sept 12-14, 2007

17. Top Yukawa Coupling Top quarks are nonrelativistic
very sensitive to CP property of Higgs
Bhupal, Djuadi, Godbole, etal
Top quarks are nonrelativistic
Fixed order perturbation theory breaks down
NRQCD treatment necessary
very sensitive to CP properties of Higgs
ILC Physics at Florence, GGI , Sept 12-14, 2007

18. Top Yukawa Coupling factor 2 from summation of terms
Farrell, AH
NLL
1-loop
tree
hard Wilson coeff
soft Green fct
factor 2 from summation of terms
factor 2 from polarization
essential for realistic studies
Juste ‘02, ‘06
tree-level, no polarization
ILC Physics at Florence, GGI , Sept 12-14, 2007

19. Top at the ILC Top, the QCD laboratory: New Physics EWSB Top Physics
Bernreuther, Brandenburg, etal, Parke, Shadmi etal., etc
Bernreuther, Bonciani, Gehrmann, Heinesch, Leineweber, Mastrolia, Remiddi etal., Huber
Top Physics
Fadin, Khoze; Reisser, AH
Beneke, Signer, Zanderighi, etal., Reisser AH
Precision Physics
QCD Laboratory
Denner, Dittmaier, Roth, Wieders; Beenakker etal; Jadach etal.
ILC Physics at Florence, GGI , Sept 12-14, 2007

20. Top Mass Measurements ILC Tev +LHC + ILC Threshold Scan
Miquel, Martinez;
Boogert, Gounaris
ILC
Threshold Scan
“threshold masses”
Tev +LHC + ILC
Invariant Mass Reconstruction
data available soon
uncertainties (much) more involved
many different methods available
error around 1 GeV challenging
What mass is measured?
How to quantify a theory error?
ILC Physics at Florence, GGI , Sept 12-14, 2007

21. ILC: Ideal Study Case Resonance region: ILC at large c.m. energy:
No beam remnant : all soft radiation can be assigned to top or antitop
Resonance region:
ILC at large c.m. energy:
Dijet limit: QCD factorization á la Korchemsky/Sterman
related to thrust and heavy jet mass event shapes
set up similar to Chekanov/Morgunov analyis except for use of k_T
ILC Physics at Florence, GGI , Sept 12-14, 2007

22. Factorization Theorem
Fleming, Mantry, Stewart, AH
hep-ph/
SOFT
QCD
JET
JET
SCET
HQET
SOFT
LO factorization theorem
JET
JET
SOFT
ILC Physics at Florence, GGI , Sept 12-14, 2007

23. Factorization Theorem
Jet functions:
perturbative, any mass scheme
depends on → “jet” mass
Breit-Wigner at tree level
Soft function:
non-perturbative
renormalized due to UV divergences
also governs massless dijet thrust and jet mass event distributions
Short distance top mass can (in principle) be determined to better than
Korshemsky, Sterman, etal.
Bauer, Manohar, Wise, Lee
ILC Physics at Florence, GGI , Sept 12-14, 2007

24. Closing Remarks .. ILC is a precision machine …
.. I only touched a few interesting issues …
.. plenty of interesting conceptual things to work on …
.. QCD aspects of top are no free lunches, needs hard work …
.. even in the beyond-SM era…
ILC Physics at Florence, GGI , Sept 12-14, 2007

25. Backup Slides
ILC Physics at Florence, GGI , Sept 12-14, 2007

26. LO Numerical Analysis Single differential distribution:
Non-perturbative effects shift the peak to higher energies and broaden the distribution.
ILC Physics at Florence, GGI , Sept 12-14, 2007

27. LO Numerical Analysis
Different invariant mass prescriptions/soft functions:
Fairly precise determination of jet mass from determination of Q-dependence of the peak position and extrapolation Q to zero
ILC Physics at Florence, GGI , Sept 12-14, 2007

28. Short-distance Top Jet Mass
One-loop: shift in the pole scheme 300 MeV
shift in the pole scheme contains renormalon
jet mass scheme: defined such that peak located at the mass to all orders
What mass is measured?
Answer: the one that gives the best convergence in the theoretical expansion.
Top Jet mass is the scheme where we expect that a LO analysis contains the least theoretical uncertainties.
ILC Physics at Florence, GGI , Sept 12-14, 2007

29. ILC Top Mass Reconstruction
Chekanov, Morgunov
hep-ex/
All-hadronic channel
Event Selection
every particle is assigned to top or antitop (fully inclusive !!)
ILC special
k_T (Durham) jet algorithm all particles are assigned to exactly 6 jets
reduces events for massless quark pair production
selects hadronic events
Top Reconstruction
6 jets with momenta
group in pairs of 3:
b-tagging
massless jet pair mass:
both invariant masses close to
selects back-to-back events
reduces combinatorics
Analysis:
ILC Physics at Florence, GGI , Sept 12-14, 2007

30. Event Shapes e.g. Thrust distribution on the peak region:
Chekanov; Morgunov
hep-ex/
ILC Physics at Florence, GGI , Sept 12-14, 2007

31. Theory Issues for definition of jet observables
initial state radiation
final state radiation
underlying events
color reconnection & soft gluon interactions
beam remnant
parton distributions
summing large logs
relation to Lagrangian short distance mass
Can be addressed in the framework of the ILC.
Requires extensions of ILC concepts and other known concepts
Hadron event shapes
ILC Physics at Florence, GGI , Sept 12-14, 2007

32. ATLAS Reconstruction Methods
Lepton + Jets
Plain Method:
W reconstruction + b tagging
Inv. mass from
events after cuts
Major error sources:
b jet energy scale:
FSR jets:
Kinematic Fit:
reconstruct entire event
impose constraints ( e.g )
vary unknows freely
b jet energy scale:
FSR jets:
Continuous Jet Definition:
plain method for varying cone size:
take weighted average
FSR error reduced
Large Events:
select events with
top pair back-to-back decay products in different hemispheres
large cone size around top/antitop jet axes:
and from in-cone momenta
strong sensitivity to soft jets + Underlying Events
Mass scale calibrations (W mass)
UE:
calibration
ILC Physics at Florence, GGI , Sept 12-14, 2007