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Summary on Physics Session

Summary on Physics Session. Nobuchika Okada (KEK & Grad. Univ. Advanced Studies). The 8 th ACFA Workshop July 14, 2005, Daegu, Korea. 1. Introduction. Why do we need LC? What can we do with LC?. New physics search! LC < LHC for discovery potential

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Summary on Physics Session

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  1. Summary on Physics Session Nobuchika Okada (KEK & Grad. Univ. Advanced Studies) The 8th ACFA Workshop July 14, 2005, Daegu, Korea

  2. 1. Introduction Why do we need LC? What can we do with LC? New physics search! LC < LHC for discovery potential Precision measurements! LC > LHC Specify new physics  SUSY or Extra-dim model or other? Precisely measure parameters of new physics: coupling, CPV, .. properties of new particles: spin, party, CP, .. Target  New physics around 100 GeV – 1 TeV

  3. From CMB + SN1a + structure formation Do the current experiments and /or observations suggest New Physics around 100 GeV -1 TeV? Maybe Yes! Observations of the present Universe after WMAP Dark Energy 73 % (cosmological constant) Dark Matter23 % Baryon 4 %

  4. No dark matter candidates in the SM!  need New Physics if DM is a thermal relic  WIMP dark matter with mass O(100) GeV ! What is the origin of baryon asymmetry in the present universe (BAU)?  need mechanism of Baryogenesis EW baryogenesis SM cannot produce enough BAU with CP-phase in CKM-matrix and  New Pysics around EW scale

  5. Are there any well-motivate New Physics models? What properties of them can be revealed at ILC? SUSY models light Higgs boson < 150 GeV lots of new particles (superpartners) DM candidates  neutralino with mass around 100 GeV Models with extra-dimensions Large extra-dim model M* = O(1TeV) Randall-Sundrum model  KK mode mass = O(1TeV) O(1TeV)  to solve gauge hierarchy problem KK graviton phenomena occurs around 1 TeV Universal extra-dim model(higher dimensional SM) DM candidate (LKP) with mass around 100 GeV -1 TeV KK modes of SM particles around 100GeV – 1 TeV

  6. Extended Higgs sector models Little Higgs model etc. dynamical origin of EW symmetry breaking with T parity DM candidates heavy particles around 1 TeV Multi-Higgs doublet models successful EW baryogenesis New source of Lepton Flavor Violation (LFV) variation of Higgs mass and Higgs CP properties etc. What can we do with ILC in order to reveal these new physics?

  7. 2. Talks in Physics Session There were 12 talks including 4 mini-reviews Lots of interesting LC studies have been reported SUSY related topics K. Cheung: Splitting split SUSY and signal at LC (mini-reviews) R. Godbole: Fermion polarization in sfermion decays Y.G. Kim: Probing the Majorana nature and CP properties of neutralinos Lepton flavor violation S. Kanemura: Search for LFV at ILC K. Tsumura: Lepton flavor violating decays of Higgs bosons under the rare tau decay results

  8. LC and cosmology interface through EW baryogenesis scenario Y. Okada: Electroweak baryogenesis and LC (mini-review) Extended Higgs sector models J. Song: Little Higgs Models (mini-review) D.W. Jung: Partially composite Two-Higgs-doublet models Extra-dimensional models S. Matsumoto: Resonant signatures of Universal Extra Dimension model at LC S. Raychaudhuri: Hunting resonances in e+e-  mu+ mu- at LC with beamstrahlung and ISR Probing anomalous coupling R. Godbole: Probing anomalous VVH couplings at an e+e- collider Generator development Y. Yasui: Calculation of the six-fermion production at ILC with Grcft

  9. 3. Brief summary on each talks Splitting split SUSY and signal at LC (mini-review) Talk by Kingamn Cheung Split SUSY scenario ino mass <<sfermion mass  solves SUSY FCNC and CP problems easily Fine-tuning problem returns but we do not care about it Still has good features of SUSY model  gauge coupling unification Dark matter candidate (light neutralino) light SM-like Higgs boson

  10. DM Some extensions: Original split SUSY: Bino, Wino, Higgsino High-mu split SUSY Wino DM Low mu split Higgsino DM Gauge coupling unification is OK

  11. Collider signatures  Neutralino and chargino production and decay via intermediate sfermions disappear Production processes Decay processes

  12. Fermion polarization in sfermion decays Talk by Rohini Godbole Polarization of final state f  information of coupling • In SUSY model, 3rd generation sfermion is among the lightest • Measurement of tau/top polarization from stau/stop decay is important to extract the information of L-R sfermion mixing Example) mSUGRA Bino is likely to be the lightest  AMSB Wino is the lightest 

  13. Measurement of tau polarization is the key  How to measure it? See tau hadronic decay modes J=0 J=1  Differently depends on tau polarization Distribution of R is peaked at R < 0.2, 0.8 < R for around R =0.5 for

  14. Probing the Majorana nature and CP properties of neutralinos Talk by Yeong-Gyun Kim In SUSY model, neutralinos are spin1/2 Majorana particle To probe the Majorana nature and CP properties of neutrinos  see charge self-conjugate 3 body decayof polarized neutralinos : neutralino polarization vector Neutralino produced in decays are 100% polarized Differential decay distribution with four kinematic functions with

  15. Charge self-conjugate-ness by Majorana particle CP and CPT invariance  relations among Marorana nature of the neutralinos can be checked thorough lepton energy distribution lepton angler distribution w.r.t neutralino polarization vector Results of numerical analysis Lepton energy distribution Lepton angular distribution

  16. Search for LFV at ILC (mini-review) Talk by Shinya Kanemura LFV is a clear signal of physics beyond the SM Many new physics models predict LFV Search for LFV at ILC LFV in LC SUSY model : Direct LFV Yukawa determination via the Higgs boson decays Two Higgs model: LFV in a deep inelastic scattering process at a fixed target experiment Two Higgs model:

  17. Tau associated LFV processes may be interesting at ILC less constrained Yukawa coupling is large  Higgs mediated process is involved Decoupling property of LFV for gauge and Higgs mediated processes are deferent  gauge Higgs Higgs mediated processes are not necessarily decoupled even in the case of decoupling SUSY mass  Higgs mediated processes become important !

  18. Proposal of fixed target option Cross section in SUSY model • Each sub-process e q (μq) →τq is proportionalto the down-type quark masses. • For the energy > 60 GeV, the total cross section is enhanced due to the b-quark sub-process E ＝50 GeV 10^(-5)fb 100 GeV10^(-4)fb 250 GeV10^(-3)fb CTEQ6L

  19. Lepton flavor violating decays of Higgs bosons under the rare tau decay results Talk by Koji Tsumura LFV via Higgs decay in two Higgs doublet model  Extended Higgs sector violates lepton flavor LFV decay of the lightest Higgs boson at ILC Tau associated process is important  large Yukawa Less constraint from tau rare decay

  20. LFV Higgs boson decay v.s. constraint from rare tau decay Excluded by tau rare decay  Constrained by Higgs decay from ILC can be tested 3 sigma level

  21. Electroweak baryogenesis and LC (mini-review) Talk by Yasuhiro Okada EW baryogenesis offers an important connection between cosmology and particle physics EW Baryogenesis Strong 1st order phase transition is required  Spharelon condition should be satisfied BUT SM with only CP-phase in KM-matrix and cannot satisfy the condition  New physics around 100GeV - 1TeV

  22. Examples of new physics for EW baryogenesis • MSSM with light right-handed stop • new CP violation sources  phase of Numerical results on baryon number C.Balazs et al., 2005  LC physics

  23. 2) Two Higgs doublet model Correlation between Spharelon condition and deviations of the Higgs triple coupling from that of SM are examined Strong 1st order phase transition occurs for Large deviation of O(10%) for Higgs triple coupling from that on SM Compare: MSSM with light stop O(6%) deviation Precise measurement of Higgs self coupling  ILC

  24. Little Higgs Models (mini-review) Talk by Jeonghyeon Song EW scale stability (in non-SUSY)  Constraints from precision measurements  is most likely 10 TeV  1% fine-tuning is needed: little hierarchy problem Little Higgs Model solves the problem Higgs boson as a pseudo-NG boson No quadratic divergence at 1 loop level cancelled out by new heavy particles • Existence of new heavy SM-like gauge boson & fermions • interesting targets for ILC

  25. Some Little Higgs models: Littlest Higgs, simplest Little Higgs, etc. ``Littlest Higgs model with T-Parity’’ would be the most interesting one Under T-parity: SM particle even Heavy gauge boson (W’, Z’, A’) odd Similar to R-parity  Lightest T-parity odd particle is stable and DM candidate! Also, some phenomenologically dangerous interactions among SM particle and new heavy particles are switched-off by T-parity Consistent with WPAM

  26. Partially composite Two-Higgs-Doublet models Talk by Don-Won Jung Top condensation model dynamical EW symmetry breaking model composite Higgs model Top quark gets its mass by its condensation Drawback  predicted top mass is too heavy > 200 GeV To cure this problem  lower top condensation value One composite One elementary Idea: Two Higgs doublet model We can take  Top mass can be consistent with exp.

  27. Effective description of this model  two Higgs doublet model with some constraints on parameters originated from compositeness of one Higgs doublet (compositeness condition at the composite scale ) Measure the model parameters at ILC

  28. Resonant signatures of universal extra dimension model at LC Talk by Shigeki Matsumoto Universal Extra Dimension (UED) model  SM in TEV scale extra-dimensions From a 4-dim point of view, UED contains Minimal setup M4×S1/Z2 SM particles and their KK-modes (gauge) γ, W, Z, γ(n), W(n), Z(n) (lepton) Li, Ei Li(n), Ei(n) (quark) Qi, Ui, Di Qi(n), Ui(n), Di(n) (higgs) h H(n) nth-KK particles m ~ n/R R 1 2 I. Compactification scale R is constrained by LEP (1/R > 300 GeV) II. Z2-orbifolding is required for produsing the chiral fermion at 0-mode. UED has KK-parity [+(-) for even (odd) n] (momentum conservation of 5th dim.) I. The lightest KK particle (LKP) is stable. Dark matter candidate II. Single KK particle (odd n) cannot be produced.

  29. Spectrum of 1st KK modes All interactions in UED are determined by those in SM. No CP & Flavor problems UED has only two new-physics parameters. R: Size of extra dimension, Λ：Cutoff scale 1st KK spectrum The spectrum of 1st KK modes in the model is very similar to that of super-particles in MSSM (mSUGRA). 1/R = 500 GeV ΛR = 20 Kinematics are essentially same !! It is difficult to distinguish between these two models at LHC. We need a lepton collider such as ILC. if UED is actually realized

  30. Resonant signatures of UED What is a difference? UED has a structure similar to SUSY models I.∃higher KK modes, II. Difference of spins between 1st KKs & Super-particles There are resonances originated from these differences !! (The resonances does not appear in supersymmetric models.) II. I. B(1) e+ q(1) e+ L(1) q γ Z(2) q e- q(1) B(1) e- L(1) 1-loop quakonium

  31. Cross section of resonances e+e- b(1)b(1) bb + E e+e- Z(2)  μ+μ- + E (pb) (pb) 1/R = 400 (GeV) ΛR = 20 1/R = 400 (GeV) ΛR = 20 1 10 0.1 1 0.01 0.1 930 854 935 846 850 (GeV) (GeV) We can distinguish UED from MSSM by using resonances. We can determines model parameters such as R &Λ. 1/R  Overall locations of resonances, Λ Relative distance between the locations, their widths

  32. Hunting Resonances in e+e-  mu+ mu- at LC with beamstrahlung and ISR Talk by Sreerup Raychaudhuri Randal-Sundrum model: 5 dim gravity model with warped geometry Model parameters: Interactions with SM particle: KK graviton tower: If  resonant production of KK gravitons are possible!

  33. Beam effects at LC Radiation phenomena: initial state radiation (ISR) beamstrahlung  cause large energy loss and disrupt the focusing of the beam This is nuisance and cannot be completely eliminated Idea: this may be useful for resonance hunting LC energy is fixed  off-resonance ISR and beamstrahlung will cause effective beam energy spread  might excite the resonance of X Similar to the effect of ``radiative return’’ of the Z-pole at LEP 1.5

  34. LC with

  35. Useful for multi-resonance case Tower of KK gravitons in RS model LC with Measurement of resonance points

  36. Probing anomalous VVH couplings at an e+e- collider Talk by Rohini Godbole In the SM, In New Physics model  Higgs may have different CP properties wider range of allowed masses • It is important to probe its CP properties through VVH couplings in model independent ways

  37. Numerical analysis for ZZH and WWH anomalous couplings ZZH vertex WWH vertex

  38. Calculation of the six-fermion production at ILC with Grcft Talk by Yoshiaki Yasui Upgrade of GRACE system GRACE: the computer code which performs the automatic calculation of the Feynman amplitudes • 6 f, 8f and more final states are important at LC studies • In principle, GRACE can calculate these processes BUT… very slow • Upgrade GRACE to implement new algorithm to construct sub-sets of the sub-graphs automatically Grcft : upgrade version of GRACE O(5-100) times faster than GRACE

  39. 4. Conclusions There are lots of well-motivated New Physics whose scale lies around 100 GeV -1 TeV scale. This range is accessible at future colliders: ILC and LHC. ILC has a great advantage to specify the new physics model uniquely and to measure model parameters and new particle properties precisely. LHC is planed to start running from 2007. Before LHC, we have to have done many LC physics studies. To do so, collaborations among theorists and experimentalists are very important. Theorists (experimentalists) should recruit experimentalists (theorists) and push forward with the ILC projects.

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