The 37th General Meeting of ILC Physics Subgroup

→ Asia/Tokyo
Description
Date/Time: 10:30~17:30 JST, Jun. 21, 2014 Place: Room 425, Building No.3, KEK Official Language: English Video Conference ID: 291 (KEK MCU2)
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Since the 36th meeting on Apr. 19, 2014, the working group
had made significant progress, thanks to your contributions,
and we could successfully hold our 37th general meeting.

Thank you very much for those who participated in the meeting.
The following is a very short summary of the 37th meeting.
Minutes of the discussion session will be sent separately.

If you find any mistakes or accidental omissions, please let us know.

The next general meeting will be on August 30, 2014 (Conf.ID: 763).

Working group contact persons
A.Ishikawa, H,Ono, S.Kanemura, M.Kurata, T.Suehara
T.Tanabe, J.Tian, M.Nojiri, and K.Fujii


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A Summary of The 37th General Meeting of the ILC Physics Subgroup
June 21, 2014 (Sat) at Room 425, Building 3, KEK
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0) Attendants:
Present at KEK:
A.Ishikawa (Tohoku)
J.Strube   (Tohoku)
S.Watanuki (Tohoku)
C.Grews    (Tohoku)
C.Calancha (KEK)
Y.Okada    (KEK)
M.Nojiri   (KEK)
K.Fujii    (KEK)
J.Tian   (KEK)
T.Ogawa    (Sokendai)
A.Dubey    (Tohoku)
M.Kurata   (Tokyo)
T.Tanabe   (Tokyo)
K.Hidaka   (Gakugei)
H.Ono      (NDU)
S.Kanemura (Toyama)
H.Yokoya   (Toyama)
M.Kikuchi  (Toyama)
N.Machida  (Toyama)
T.Suehara  (Kyushu)

Remote connection:
K.Kotera   (Shinshu)
S.Kawada   (Hiroshima)
Y.Sudo     (Kyushu)

0) Opening comments (K.Fujii)

1) vvH: H \x{2014}> jj (Christian Drews)
Status:
- The study aims at updating the higgs mass at Ecm=250GeV to mh=125 GeV,
 while separating Higgsstrahlung and WW-fusion contributions to vvH.
- Results from template fitting
 Compared with the extrapolation from Ono’s results, H\x{2014}>cc precision 
 seems significantly worse. This might be improved, once LCFIplus is 
 tuned up at Ecm=250GeV.
 An interesting interference effect was found through generator level
 studies. This is, however, hard to observe after the smearing due to
 finite detector resolutions>
Next Step:
- Write up a summary.
- Study effects of overlay. 


2) ZH: Recoil mass using Z->ll (Shun Watanuki)
Status:
- eeX: new bremsstrahlung recovery
 \x{2014}> distribution became sharper.  
- Fitting
 Tried new fitting methods: Kernel estimation, CBX x Novosibirsk,
 Generally speaking the new methods provide better representation of 
 the line shape. However, for mass extraction, there is some problem.
Next Step:
- Investigate the problem with mass extraction.
- CP study.
C: Nice to see generator level plots for the production angle with 
  different eta values.
C: What about using Z decay angular distribution to extract eta.


3) ZH: Recoil mass study from p.o.v. of ECAL options (Tomohisa Ogawa)
  Z\x{2014}>qq: hadronic recoil mass: comparison of Si-ECAL and Sci-ECAL
Status:
- simulation conditions
  Ecm=350GeV, pol=(-0.8,+0.3)
  Z\x{2014}>qq, H\x{2014}>all, invisible (H\x{2014}>ZZ*\x{2014}>4v)
- analysis strategy (follow Mark Thomson)
- summary
 no significant difference for Z->ll
 The difference is not so significant also for Z\x{2014}>qq at Ecm=250GeV.
 At Ecm=350GeV, a slight difference has been seen.
Nest Step:
- MVA selecton.
C: Since the BG samples are common (generated with Si ECAL), the comparison
  is meaningful only between the signal samples.
C: For H->jets, the mass resolution is dominated by confusion in jet clustering.
  For the comparison of the ECAL technologies, we had better stick to the invisible
  decay analysis, where the recoil mass resolution is entirely determined by the
  jet energy resolution.


4) Higgs to tau tau (Shin-ichi Kawada)
Status:
 new from previous meeting:
 - 500 GeV vvH
     tau finder & kT clustering
     TMVA
 - 250 GeV: first try.
- Setup:
 Ecm=500GeV, 500fb-1, mh=125GeV
- Results:
 - vvH @ 500GeV with 500fb-1
   kT: R=0.5 chosen based on tau finder performance
   TMVA (double TMVA first w/o aa_2f): 14.7sigma for R=0.5
   \x{2014}> 6.8% on vvH followed by H->tau tau 
 - qqH @ 250 GeV with 250fb-1
   \x{2014}> 4.3% on qqH followed by H\x{2014}> tau tau
Next:
- Finalize 500 GeV analysis.
- Separte Zh and WW-fusion in vvh
- mh=125GeV analysis at Ecm=250GeV with correct tau polarization.


5) Top Yukawa coupling study at 500 GeV (Yuji Sudo)
Status:
 new: overlay low Pt beam background
- Setup:
 mh=125 GeV, 500fb-1 at Ecm=500GeV, 
 beam polarization=(-0.8,+0.3)
- Results:
 At AWLC14: (w/o kT clustering)
   8-jet  : S/sqrt(S+B)=2.04
   L+6-jet: S/sqrt(S+B)=2.42
   \x{2014}>delta y_t / y_t = 15.7%
 kT clustering for 8-jet
   \x{2014}> efficiency increase by 26%
   \x{2014}> expect improvement in precision.
Nest Step:
- Update the results with kT


6) 2HDM searches at the ILC in the 4 top quarks process (Hiroshi Yokoya)
Setup:
 Searches for H/A \x{2014}> ttbar (low tan beta)
 e+e- \x{2014}> HA \x{2014}> tttt : O(1)fb for mH/A=450GeV (SM BG: 4ab @ 1TeV)
      photon collider: H/A \x{2014}> tt
Results:
 -> Simulation (theorist level;^)
    hadronization \x{2014}> smearing using TDR detector performance parameters.
Next Step:
- determination of mass and tan beta.
Q: Is there low tan beta constraints from LEP?
A: Not in the general 2HDM. There might be constraints from other low E measurements.


7) Radiative corrections to Higgs couplings in 2HDM (Mariko Kikuchi)
Setup: 2HDM
  M^2 = 2 m^3 / (sin 2*beta) : scale at which Z2 breaks.
  \x{2014}> 8 parameters, mh, mH, mA, mH+, v, alpha , beta, M^2
Results:
  deviation 
     tree level: kappa_W=sin(beta-alpha)
                 kappa_f=cos alpha / sin beta (, - sin alpha/cos beta)
     1-loop: calculated all yukawa couplings
                 possible to modify them by several %.
C: mass-coupling for SM in loop level is needed in order to compare this
  with the SM.
C: this comparison is made in on-shell scheme.
C: Fix kappa_v instead of sin^2(beta-alpha)?


8) m_nu, DM, baryogenesis from the SUSY gauge theory with confinement (Naoki Machida)
Setup:
  SUSY SU(2)H gauge theory
  Why mu^2 < 0?, Where does lambda_SM come from?
Big questions:
- Baryon asymmetry
 1st order phase transition: phi_C/T_C >~ 1 (~ (50GeV/m_h)^2 in SM) \x{2014}> excluded.
 m_Phi^2 = M^2 + lambda_i v^2
- m_v
 radiative seesaw
 e.g. Ma model (2006)
     Phi’: inert scalar doublet
     v_R: Z2-odd right-handed v
     \x{2014}> m_v and DM (lightest Z2-odd particle)
 Aoki-Kanemura-Seto model (2009)
     Phi_SM + Phi_2 + S+/- + eta^0 + v_R
- Fundamental theory:
 SUSY SU(2)_H
  slepton, squarks ~ 5TeV
Phenomenological consequences:
 - DM=v_R
 - m_v from v_R + hybrid radiative seesaw
 - EW Baryogenesis
 - collider phenomenology:
   - light inert doublet:
     e+e- \x{2014}> HA \x{2014}> ZHH
          -> H+H- \x{2014}> W+W-HH
   - Smoking gun evidence:
     e-e- \x{2014}> Omega- Omega- (v_R exchange)
Q: SUSY breaking mechanism?
A: several possibilities
Q: GUT?
A: we have to give up GUT.


9) H125 -> ccbar at full 1-loop level in MSSM (Keisho Hidaka)
Setup:
  MSSM with QFV
  Constraints: 
    LHC SUSY, MSSM Higgs bosons
    b->sgamma, DeltaM_Bs, Bs->mu+mu-, B+->tau+ nu, etc.
  Parameters:
    M_1=170, M_2=350GeV, M_3=1000GeV, …
[Large scharm-stop and stop_L stop_R mixings 
   + large trilinear couplings (T_U23,T_U32,T_U33)]
  -> su_1,2-su_1,2-h0 coupling large 
  -> gluino loop large 
  -> h0 -> ccbar large!
Results:
  MSSM partial width for h0->ccbar can be ~50% larger than SM.
theoretical uncertainty ~ 2% (from renormalization scale dependence)
                             ~ 4% (from error of charm mass m_c(m_c))
  -> experimental error      ~ 3% (at ILC(500GeV)_LumiUP)
Q: Does top Yukawa receive a similar big deviation?
A: Yes. working on it now.
Q: Is this large deviation for h0 \x{2014}> ccbar a unique feature of this model?
A: needs to measure deviation pattern of various observables to fingerprint the model.


10) Tools for ILC cross section database (Constantino Calancha)
- Web interface
   Ecm: mandatory \x{2014}> cross section info.
- Command line tool
   preferred method is to use the tool on kekcc.


11) General particle ID study and its application (Masakazu Kurata)
Status:
- In search of possible analysis improvement:
 Possible lepton ID improvements using
   dE/dx in TPC
   Shower profile in ECAL&HCAL
   \x{2014}> lepton ID ~30% improvement has been achieved.
   Energy correction
   B-tagging
- MC matching
   improved and now matching efficiency is ~100%.
   \x{2014}> mu ID    : 80% (AWLC) \x{2014}> 70%
      hadron ID: 68% (AWLC) \x{2014}> 75%
- Energy correction
 by correct mass assignment using particle ID:
 -> moves m_Z and m_H to the right direction
- b-tagging
 decay products are being investigated to get some hints for improvements.
Next Step:
- p-ID optimization
- study B decay more
- study D meson decay
C: pi0 reconstruction may be useful for c-tagging?
Q: Does pi0 mass constraint help energy scale calibration?


12) Physics case for the ILC: Post LHC8 (Tomohiko Tanabe)
Tomohoko presented a set of slides being prepared as background material
for the MEXT’s ILC physics review. The material has been worked on by
the LCC physics working group and a ad hoc local working group. 

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The slides shown at the meeting is available from
http://agenda.linearcollider.org/conferenceDisplay.py?confId=6422
see them for details.
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Discussions on future direction and milestones
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*) Discussions
Following the presentation by Tomohiko, we discussed the future direction of the 
working group activities. 
a) short-term goal:
 Be prepared for the review of ILC physics case by the physics WG set up under 
 the MEXT expert panel. For this we should be flexible and take action as needed.
b) middle-term goal:
 Provide inputs to the LCC ILC-parameter WG for staging scenarios.
c) longer-term goal:
 Be prepared for the LHC Run2.
For (b) and (c), our next milestone is the LCWS 2014 in Belgrade, Oct. 6-10.
Going through Tomohiko’s slides, we tried to identify places where we need updating
or new studies.
More information on the discussions will later be circulated separately.

*) Meeting Schedule:
 Next general meeting (2014/08/30 10:30) : Conf.ID: 763


Working group web page:
http://www-jlc.kek.jp/jlc/en/subg/physics
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