SCLC

Physics with 500 GeV LC : Physics with 500 GeV LC Hitoshi Murayama (UC Berkeley) LC Retreat Santa Cruz, June 27, 2002


We are interested inthings we don’t see : We are interested in things we don’t see


Energy budget of Universe : Energy budget of Universe Stars and galaxies are only 0.1% Neutrinos are ~0.1–10% Rest of ordinary matter (electrons and protons) are ~5% Dark Matter ~25% Dark Energy ~70% Anti-Matter 0% Higgs boson ~1062%??


The Cosmic Questions : The Cosmic Questions What is Dark Matter? What is Dark Energy? How much is Neutrino component? Is Higgs Boson really there? Where did Anti-Matter go?


Synergy at TeV scale : Synergy at TeV scale Dark Matter Fermi (Higgs) scale v~250GeV Dark Energy rL~(2meV)4 vs (TeV)2/MPl~0.5meV Neutrino (Dm2LMA)1/2~7meV vs (TeV)2/MPl~0.5meV TeV-scale physics likely to be rich


Fermi’s dream era : Fermi’s dream era Fermi formulated the first theory of weak force (1933) Knew the required energy to study the problem: ~TeV We are finally getting there!


Higgs Boson : Higgs Boson


Mystery of the “weak force” : Mystery of the “weak force” Gravity pulls two massive bodies (long-ranged) Electric force repels two like charges (long-ranged) “Weak force” pulls protons and electrons (short-ranged) acts only over 10–16 cm [need it for the Sun to burn!]


Something is in the Universe : Something is in the Universe There is something filling our Universe It doesn’t disturb gravity or electric force It does disturb weak force and make it short-ranged What is it??


Like a superconductor : Like a superconductor In a superconductor, magnetic field gets repelled (Meißner effect), but penetrates only over “penetration length”  Magnetic field is short-ranged! Imagine a physicist living in a superconductor Finally figured: magnetic filed must be long-ranged there must be mysterious charge-two condensate in his “Universe” But doesn’t know what the condensate is, nor why it condenses Doesn’t have enough energy to break up Cooper pairs That’s the stage where we are!


Higgs Boson is Most Likely “Just Around the Corner” : Higgs Boson is Most Likely “Just Around the Corner” All current data combined, sensitive to quantum effects of the Higgs boson mH<196GeV (95%CL) (LEPEWWG Winter 2002) Tevatron at Fermilab, IL, has chance to discover Higgs boson by 2008


Higgs Boson at LHC : Higgs Boson at LHC LHC would discovery Standard Model Higgs boson of any mass within 3 years! (2011?) Does it settle the issue? I’m afraid not. Suppose Hgg discovered, cross checked by ttH final state Technipion? Scalar or pseudo-scalar? Does it couple to W/Z?


Questions to be answered : Questions to be answered Is the particle discovered really the Higgs boson? Is it really responsible for particle masses? Does this have the right quantum number 0+? Is it condensed in the Universe? Prove it is the “Origin of Mass” Spin/Parity Couplings Vacuum expectation value Branching Ratios


Higgs Boson at LC : Higgs Boson at LC Angular distribution in e+e–ZX depends on X=h, A, V Is it a 0+ boson?


Higgs Boson at LC : Higgs Boson at LC Branching Fractions test the relation coupling  mass  proves that Higgs Boson is the “Origin of Mass”(Battaglia)


Higgs Boson at LC : Higgs Boson at LC ZH final state ALR proves it is due to s-channel Z-exchange


Higgs Boson at LC : Higgs Boson at LC ZH final state ALR proves it is due to s-channel Z-exchange We know Z:gauge boson, H: scalar boson  only two vertices


Higgs Boson at LC : Higgs Boson at LC ZH final state ALR proves it is due to s-channel Z-exchange We know Z:gauge boson, H: scalar boson  only two vertices Need a VEV to get ZZH vertex


Higgs Boson at LC : Higgs Boson at LC ZH final state ALR proves it is due to s-channel Z-exchange We know Z:gauge boson, H: scalar boson  only two vertices Need a VEV to get ZZH vertex proves it is the origin of mZ HM, LBNL-38891


Absolute confidence is crucialfor a major discovery : Absolute confidence is crucial for a major discovery “New York Times” level confidence “Origin of Mass Uncovered” still a long way to “Halliday-Resnick” level confidence “We have learned that masses of all elementary particles originate in the condensate of so-called Higgs boson of mass 124GeV/c2.”


Post-Higgs Problem : Post-Higgs Problem


Post-Higgs Problem : Post-Higgs Problem We see “what” is condensed But we still don’t know “why” Two problems: Why anything is condensed at all Why is the scale of condensation ~TeV<

Three Directions : Three Directions History repeats itself Crisis with electron solved by anti-matter Double #particles again  supersymmetry Learn from Cooper pairs Cooper pairs composite made of two electrons Higgs boson may be fermion-pair composite  technicolor Physics ends at TeV Ultimate scale of physics: quantum gravity May have quantum gravity at TeV  hidden dimensions


Task : Task Find physics responsible for condensation We can eliminate many possibilities at LHC But new interpretations necessarily emerge Elucidate what that physics is Reconstruct the Lagrangian from measurements


Many theories look alike : Many theories look alike Supersymmetry Missing energy, high pT jets, leptons, b, t, t Fourth generation Missing energy, high pT jets, leptons, b, t, t


Many theories look alike : Many theories look alike Pseudo-Nambu-Goldstone bosons in technicolor Universal Extra Dimensions (Cheng, Matchev, Schmaltz) Lightest Kaluza-Klein states ~ LSP If models well-defined and only a few parameters, LHC can exclude many interpretations of data Race will be on: theorists coming up with new interpretations experimentalists excluding new interpretations  A loooong process of elimination Crucial information is in details


LC is good at details : LC is good at details Supersymmetry Fourth generation Ejj distribution tells if mB 0 Cross sections vs polarization determine quantum numbers ~


Supersymmetry at LC : Supersymmetry at LC Discovery at Tevatron Run II or LHC Test they are really superpartners Spins differ by 1/2 Same SU(3)SU(2)U(1) quantum numbers Supersymmetric couplings Spin 0?


Supersymmetry at LC : Supersymmetry at LC Is gaugino coupling = gauge coupling? Mass Measurement


Superpartners as probe : Superpartners as probe Most exciting thing about superpartners beyond existence: They carry information of small-distance physics to something we can measure “Are forces unified?”


Hidden Dimensions : Hidden Dimensions Randall-Sundrum scenario with warped extra 1D  TeV-scale KK gravitons  determine the shape of the hidden dimension


Produce Dark Matter : Produce Dark Matter Dark Matter likely to be TeV-scale electrically neutral weakly interacting particle (e.g., LSP, Lightest KK) With LC, measure its mass, couplings Can calculate its cosmic abundance If it agrees with cosmological observation, we understand Universe back to 10–12 sec after the Big Bang


Conclusion : Conclusion Physics at TeV scale likely to be rich To fully understand it, we will likely need a lot of detailed information LC will study new particles one by one  reconstruct the fundamental Lagrangian Then we would like to move on further with absolute confidence