1. ACFA 7th Nov.9-12 2004 Taipei Taiwan
Towards Higgs Precision Measurement at ILC What we have done ? & What we have to do?
JAPAN LC Physics study group Higgs subgroup
and
KEK Minamitateya Collaboration
Yoshiaki Yasui
(Tokyo Management Collage)

2. Why Precision Measurement?
What we can do after Higgs LHC? 
Higgs Precision Measurement
EW SSB, mass generation
Direct measurement of self coupling
e+e- →hh X
 luminosity upgraded LHC (SLHC)
 (e+e- → hh X ) >> (e+e- → hhh X)　　　Diouadi et.al
  SM New Physics!!
Higgs coupling may be a probe of BSM

3. MSSM at ILC?
But .....
Decoupling limit MH0 ≈ MH ≈ MA0 >> MZ hhh = (3gMZ/Cw)cos2sin()  3gMh02/2MW = hhhSM (MhSM=Mh0) hhhh = (3g2/Cw2)cos22   3g2Mh02/4MW2 =SMhhhh(MhSM=Mh0)
Top Yukawa corrections are small Hollik et.al.
Higgs self coupling = gauge coupling?
We need more idea!!

4. Non SUSY THD at ILC? Higgs self coupling as a probe of THD
Kanemura et.al LCWS’04 Paris
Baryogenesis  talk by Senaha-san

5. Radion(graviscalar)-Higgs mixing
Extra-dim at ILC?
Radion(graviscalar)-Higgs mixing
Ex:Warped Extra Dim model Randall Sundrum
m > 2mh ⇒ hh bbbb
m < mh, >> 1 ⇒ gg 0
Dominici et.al. Nucl.Phys. B671 (2003)
zzh
hhh
=5GeV
=5GeV
radion mass mPlanck-warped scale

6. Towards Higgs Precision Measurement
Machine design parameters
(CM energy, Luminosity,etc.)
Detailed study of SM Higgs
(Simulation, RC, etc.)　　
feedback
this talk
New Physics at ILC
(SUSY,THD,LH,Extra-Dim,etc.)

7. What we have done? Priority ⇒ Higgs Physics at TeV LC
Higgs self coupling⇒ We started (from 2002)
Top Yukawa
Heavy Higgs, etc.
etc..

8. @LCWS '02 Jeju Korea Assumption No bkg effects 100% signal efficiency
dominant for
ECM > 1TeV
by Yasui et.al.
　LCWS’04 Paris France
　Quick Simulation (includes bkg.) study!!

9. Our Strategy for simulation studies
Parton level Generator (tree level ⇔ GRACE-loop)
LCGrace talk by Yasui, ACFA 6th India package for LC Higgs physics study: Mh ≤ 140 GeV e+e-  6f
based on the GRACE System
Bases ⇒ Monte Carlo integration ⇒ Cross section
Spring ⇒ Events generator
Hadronizer
Pythia (interface from Spring to Pythia6)
Simulator (Quick Simulation → Full Simulation)
Analysis

10. Simulation Study Ecm = 1 TeV main mode  W-fusion
Higgs mass = 120 GeV 　　　　　SM decay Br
ISR/BSR included
Signal & bkg event generator LCGrace (BASES+SPRING)
Signal MC: X + hh /SM from 0.0 to 2.0 with 0.2 step
Smearing simulation at parton level Jet energy resolution ~ 30%/√E (GeV) (detector R&D target value)
ννhh quick analyses
only for hh decaying to 4b
Br(hh4b) ~ 47 %
for 120 GeV SM Higgs
Signal characteristics
Large missing energy, missing Pt
Only 4 b jets
M1 jj ~ Mh M2 jj ~ Mh
No isolated lepton

11. Signal and Background processes
By LCGrace
Main bkg processes
4b + missing
ννbbbb (~ ννZZ, ννZγ*)
ννbbh (~ ννZh)
Signal
(for SM)

12. ννhh Analysis Flow bkg further reduction 2. Separate Zhh & fusion
Reconstructed ‘Higgs’ mass
ννhh Analysis Flow
ννbbbb
=
1. Likelihood selection
bkg further reduction
2. Separate Zhh & fusion
different dependence
(positive/negative interferences)
3. Combine with Zhh analyses
for s-channel process
4. Check hh invariant mass
5. hhh measurements
ννbbh
=SM
L = 1 ab-1
dep. of cross-section
Zhh
eehh
/SM

13. ννhh ννhh selection Separate Zhh & fusion ννhh channel = =SM
L = 1 ab-1
ννbbbb
=
counts
counts
ννhh
‘fusion’
=SM
ννbbh
‘Zhh’
Likelihood
Missing mass [GeV]
(~ OPAL Higgs scheme)

14. HH invariant mass distributions
‘Zhh-channel’
‘fusion-channel’
counts
counts
=2  SM
=
Zhh
ννhh
=SM
=SM
hh invariant mass [GeV]
hh invariant mass [GeV]
(= visible mass)

15. hhh Measurement sensitivity
By Yamashita et.al. LCWS 2004
Mh=120 GeV
Measured /SM
True /SM
95%CL upper bound
95%CL lower bound
67%CL range
Ilumi=1 ab-1
Pol beam= -80%
@1TeV
(SM Higgs Br)
Use only hh4b
(Br(hh4b)~47%)
Eff.(4b) 80%
Precise study  Radiative corrections are also important!!
 Systematic study of the RC for Higgs physics at LC with GRACE

16. Radiative correction for e+e-ZHH
GRACE Phys.Lett.B576(2003)152
Zhang et al. Phys.Lett.B578(2004)349

17. Radiative correction for e+e-ee HH
=(O())/(tree)-1
Yasui et.al. ECFA2004 Durham UK W
WG=W- 4r
r=2.267%
QED for Mh=120 GeV
W for Mh=120GeV

18. Recent progress on the loop calculations
Single Higgs production
e+e-ZH (full number of graphs = 341)
e+e-H (1350) Phys.Lett. B559 (2003) A.Denner et.al. PLB 560(2003)196, NPB 660(2003)289
e+e-e+e- H (4470) Phys.Lett.B600(2004)65-76
top Yukawa
e+e-t t H (2327) Phys.Lett. B571 (2003) Y.You et.al.PLB 571(2003) A.Denner et.al. PLB 575(2003)290, NPB 68(2004)85
Multi Higgs production
e+e-ZHH (5417) Phys.Lett. B576 (2003) R.Zhang et.al.PLB(2004)349
e+e-ee　HH (19638)  New results!! of 2 to 4
Weak corrections are sizable O(5-10)%

19. Summary What we have done? What we have to do?
A quick simulation study has been performed for Ecm=1 TeV
For Mh=120 GeV: measurement sensitivity (only hhbbbb only)
for =SM /SM= (1) (95%CL)
/SM=  (1) (95%CL)
/SM=  (1) (95%CL)
What we have to do?
Non-b decay of the Higgs  increase sensitivity
Mh>140GeV  W-par decay of the Higgs ννhh 8f, 10f New version of Grace system
Radiative corrections (systematic study have been done)
sizable  include in the event generator
New Physics study