ILC and future high energy physics Yasuhiro Okada (KEK, Sokendai) Mini-Workshop on Frontiers in Particle Physics Phenomenology March 30, 2007, National Central University, Taiwan

Critical time for the high energy physics LHC starts its operation this year. The first look at the TeV scale physics. 14 TeV pp collider starting spring 2008 at CERN. Main targets of the LHC experiments are the Higgs boson and signals beyond the Standard Model. Outcome of LHC will determine the future direction of high energy physics.

International Linear Collider (ILC) The highest energy electron-positron collider. The CM energy is up to 500 GeV in the 1st stage, and then aims to about 1 TeV in the 2nd stage. High luminosity: 500 fb-1 for four years. .. Accelerator R&D has been continued since more than 15 years ago. Accelerator technology choice was made in August 2004. Since then the machine design work has been lead by GDE (Global Design Effort) ~30km

RDR and DCR Two reports are in preparation. Reference Design Report (RDR): Accelerator design report with the first cost estimate prepared by GDE. Detector Concept Report (DCR): The first comprehensive report on physics and detectors at ILC prepared by “Worldwide Study of the Physics and Detectors for Future e+e- Linear Colliders”. ~100 pages for physics part and ~200 pages for detector part. The final Draft will be released on April 1, 2007. The current draft is available at the ILC wiki page. http://www.linearcollider.org/wiki/doku.php

Why TeV scale? : Higgs physics SM Higgs mass constraints in the LEP era. TeV is the scale of weak interaction, i.e. the electroweak symmetry breaking. The Higgs boson is probably light. What is dynamics behind the Higgs mechanism? SUSY, Little Higgs? Extra dimensions? There should be a new interaction. TESLA TDR

Why TeV scale?: Dark matter About one fourth of the energy of the universe is carried by dark matter. This indicate existence of a new stable particle. If thermal production is assumed, the scale of the dark matter particle is likely to be near the TeV scale.

Why TeV scale?: Unification Three gauge coupling constants are consistent with SUSY GUT. If SUSY exists, this leads to a unified picture of particle physics and cosmology, which could include seesaw neutrino, leptogenesis, inflation and superstring unification. Coupling unification in SUSY GUT

Why do we need both LHC & ILC? Two machines have different characters. Advantage of lepton colliders: 　　e+ and e- are elementary particle　 　　　　(well-defined kinematics). 　　Less background than LHC experiments. 　　Beam polarization, energy scan. 　　g - g, e- g, e- e- options, Z pole option. LHC ILC

The more LHC finds, the more ILC is needed. Discovery of a Higgs boson at LHC. Is this really Higgs particle? Is the Higgs boson the SM one? If not, are there new phenomena besides the Higgs boson? Discovery of a new gauge boson at LHC. What are the properties of new force, and its meanings in unification and cosmology? Discovery of SUSY particles at LHC. Is this really SUSY? GUT? SUSY breaking? SUSY dark matter?

Higgs physics A Higgs boson will be discovered at LHC as long as its properties (production/decay) is similar to the SM Higgs boson. In order to study the Higgs mechanism at work, Higgs couplings to various particles have to be measured precisely.

Higgs boson search at LHC SM Higgs boson branching ratio Higgs boson discovery at LHC

Higgs study at ILC Precise determination of mass . Spin and CP property. Coupling determination.

Top Yukawa coupling Higgs self-coupling C.Castanier,P.Gay,L.Lutz,J.Orloff A.Gay

Proof of the mass generation mechanism of elementary particles LHC: (10)% for ratios of coupling constants ILC: a few % determination GLC project mH=120 GeV, Ecm=300-500 GeV.L=500fb-1 (Ecm>700 GeV for Htt )

New physics effects in Higgs boson couplings In many new physics models, the Higgs sector is extended and /or involves new interactions. The Higgs boson coupling can have sizable deviation from the SM prediction. The heavy Higgs boson mass in the MSSM SUSY correction to Yukawa couplings B(h->WW)/B(h->tt) B(h->bb)/B(h->tt) LC LHC LC ACFA report J.Guasch, W.Hollik,S.Penaranda

Radion-Higgs mixing in extra-dim model The triple Higgs coupling in 2HDM in the electroweak baryogenesis scenario HEPAP report Little Higgs model with T parity S.Kanemura, Y. Okada, E.Senaha Deviation to 5-10 % level can be distinguished at ILC C.-R.Chen, K.Tobe, C.-P. Yuan

SUSY Higgs search In the MSSM, there are five Higgs states. In the most of parameter space, the lightest one is a SM-like Higgs boson with mass less than 14 GeV. Other four states are nearly degenerate with a suppressed coupling to gauge bosons.

g g H/A Laser e- beam a few mm Heavy Higgs search at ILC Heavy Higgs bosons are pair-produced at the e+e- collider mode. If the gg option is used the mass reach can be extended up to 80 % of e-e- energy. g H/A Laser e- beam a few mm g GLC project

Direct searches for New Physics Some type of new signals is expected around 1TeV range, if New Physics is related to a solution of the hierarchy problem. (SUSY, Large extra-dimension, etc ) The first signal of New Physics is likely to be obtained at LHC. (ex. squarks up to 2.5 TeV at LHC) ILC experiments are necessary to figure out what is New Physics, by measuring spin, quantum numbers, coupling constants of new particles, and finding lower mass particles which may escape detection at LHC. Beam polarization, energy scan, and well-defined initial kinematics play important roles in ILC studies.

SUSY studies at ILC SUSY is a symmetry between fermions and bosons. Spin determination is essential, ideal for ILC. W,Z,g, H gluon lepton quark neutralino, chargino gluino slepton squark SM particles Super partners Spin 1/2 Spin 0 Spin 1 neutralino mixing chargino mixing Mixing angle determination

Precision SUSY particle measurements at the ILC. Determination of SUSY breaking and GUT scenarios. Mass and mixing determination of chargino, neutralino, slepton, squark. Chargino threshold scan Smuon decay spectrum ~50 MeV ~100 MeV H.U.Martyn

Extrapolation of gaugino and scalar mass parameters to the GUT scale with inputs from combined analysis of LHC and ILC. Blair, Porod, Zerwas

Alternative Scenarios to SUSY Determination of the number of extra dim at ILC 500 and 800 GeV Main motivation for alternative scenarios is to explain the stability of the weak scale. Alternative scenarios involve new strong dynamics or change of space-time, and new signals at the TeV scale. Large extra dimensions Warped extra dimensions Universal extra dimensions Little Higgs models… If LHC find the first signal of new physics ILC will study new particles and interactions and identify the underlying theory. G.W. Wilson

Z’ coupling in various models Even if the initial ILC energy is not enough to produce a new particle, indirect effects can provide important information for new physics. Z’ mass =1,2,3,4 TeV e+ e- Z’ f Ecm=500 GeV, L=1/ab Godfrey, Kalyniak, Reuter

Connection to Cosmology Many new physics models contain dark matter candidates from various reasons. LSP in SUSY LKP in Universal Extra Dimension model LTP in Little Higgs model with T-parity If the dark matter particle is produced as decay products of new colored particles, missing transverse energy signal is likely found at the LHC experiment. ILC can distinguish different scenarios and determine dark matter particle’s properties to match the observed dark matter density in the universe. Identification of the dark matter particle.

Cosmological parameter determination WMAP, Planck, … Dark matter profile in our galaxy Thermal history of the Universe Cosmological parameter determination WMAP, Planck, … Direct and indirect (g, e+,anti-p, n ) searches for dark matter Thermal relic abundance Detection rate Collider search for a dark matter candidate particle at LHC and ILC. ILC will play a particularly important role in distinguishing different models and determine properties of the dark matter candidate. See, E.A.Baltz,M.Battaglia,M.E.Peskin,and T.Wizansky, hep-ph/0602187

SUSY Dark Matter Ellis,Olive,Santos, Spanos J.Feng Dark matter relic abundance calculated from ILC results, Bulk Focus Stau co-annihilation A-pole E.A.Baltz, M.Battaglia,M.E.Peskin,and T.Wizansky

Top Quark Physics Top quark mass and width Top quark anomalous interactions Top Yulawa coupling and anomalous coupling to gauge bosons Precision of the mass ~ 100-200 MeV Width measurement is unique at ILC. A.H.Hoang P.Bhartra and T,Tait

Coupling of Gauge Bosons Coupling among gauge bosons These measurements become very important for unexpected Higgs case. Example: WW g anomalous coupling W g

Indirect sensitivity to Z’ boson at GizaZ Very precise measurements at Z pole (GigaZ option) could provide an indirect sensitivity up to ~10 TeV though Z-Z’ mixing effects with improved masses of the top quark and the Higgs boson. FLC: 500GeVILC + GigaZ F.Richard

Conclusions The LHC experiment is expected to open a new era of the high energy physics by finding a Higgs boson and other new particles. Establishing the mass generation mechanism is the urgent question. This will be achieved by precise determination of the Higgs couplings, and ILC will play essential roles. In order to explore New Physics, Higgs coupling measurements, direct study of new particles and new phenomena, and indirect searches through SM processes are all important at ILC. TeV physics explored at LHC and ILC will lead to new understanding of unification and cosmology.