Hunting for New Particles & Forces

Example: Two particles produced Animations: QPJava-22.html u u d u d u

Example: Dark Matter Particle produced Animations: QPJava23.html u u d u d u

Physics at the Tevatron mb -  b - nb - pb - fb Higgs Mass [GeV/c 2 ]  Total Inelastic bb WZWZ tt - - WZ Tevatron 3 x x x x ,000 16,000, 12,000 Higgs WH,ZH 4000 ~ ~ 40 jets (qq, qg, gg) Single Top observed

Tevatron Cross Sections The Higgs cross section is orders of magnitudes lower than the total inelastic cross section. Recent evidence of single top quark production is an important milestone towards the Higgs boson. Light quarks are ubiquitous. Plenty of W and Z bosons → calibration. Total inelastic cross section.

WWWW top bottom Higgs Tevatron: Improve Higgs Mass Pred. via Quantum Corrections M top (GeV) M W (GeV) GeV = 1 GeV / c 2 ~ proton mass M higgs = 100 GeV 200 GeV 300 GeV 500 GeV 1000 GeV

W top bottom Z top W, Z Higgs Tevatron: Higgs Mass Prediction via Quantum Corrections Clues to the Higgs ? M H = GeV; M H < 95% CL M top (GeV) Tevatron Run II M W (GeV)

Tevatron: Higgs Mass Prediction via Quantum Corrections Clues to the Higgs ? M H = GeV; 114 < M H < 95% CL Winter 2007

Higgs boson Tevatron Associated Production m H < 135 GeV –  (W,Z+H) ¼ 0.15 pb H  bbH  WW Gluon fusion m H > 135 GeV –  (H) ¼ 0.45 pb

Higgs boson decays H  ff, WW, ZZ –couples to mass; – heaviest final state dominates m H < 135 GeV –H  bb m H > 135 GeV –H  WW Tevatron can explore bb and WW(  ℓ + ℓ - ) decay modes

SM Higgs: Event Signatures m H <135 GeV m H >135 GeV

Status of Direct Search for Higgs boson 2010: 8 fb -1 –Exclude115 < m H < 125 GeV and 150 <m H < 180 GeV

The Next Energy Frontier The Large Hadron Collider

SM Higgs boson production Gluon fusion Vector Boson Fusion W, Z associated production tt, bb associated production

Tevatron: Improve Higgs Mass Pred. via Quantum Corrections M top (GeV) M W (GeV) LHC: Designed to discover Higgs with M higgs = 100 ~ 800 GeV M  (GeV) 130 GeV Higgs L = 100 fb -1 # of events / 0.5 GeV TevatronLHC

M Higgs (GeV) 5  Discovery Luminosity (fb -1 ) Tevatron: Improve Higgs Mass Pred. via Quantum Corrections M top (GeV) M W (GeV) LHC: Designed to discover Higgs with M higgs = 100 ~ 800 GeV TevatronLHC

M top (GeV) M W (GeV) M Higgs (GeV) 5  Discovery Luminosity (fb -1 ) Tevatron: Improve Higgs Mass Pred. via Quantum Corrections LHC: Designed to discover Higgs with M higgs = 100 ~ 800 GeV TevatronLHC easy hard Will the Tevatron’s prediction agree with what LHC sees?

tan  M A (GeV) LHC M top (GeV) MSSM M W (GeV) Tevatron LHC TevatronLHC Higgs in Minimal Supersymmetric Extension of Standard Model LHC will be the best place to discover Higgs particles!

Unification of the Forces

Unification We want to believe that there was just one force after the Big Bang. As the universe cooled down, the single force split into the four that we know today. 1TeV = 10 3 GeV (10 16 K) s GeV (10 29 K) s GeV (10 32 K) s 2.3 x GeV (2.7K) 12x10 9 y Energy Temp Time

Unification of electromagnetic & weak forces (electroweak theory) Long term goal since 60’s We are getting there. Beautifully demonstrated at HERA ep Collider at DESY The main missing link is Higgs boson HERA Q 2 [GeV 2 ] Electromagnetic Force Weak Force f  HERA: H1 + ZEUS

  -1   -1   Q [GeV]  orders of magnitude higher energy The Standard Model fails to unify the strong and electroweak forces.

Adding super-partners

Q [GeV]  -1   -1   -1   -1 With SUSY

Unifying gravity with the other 3 is accomplished by string theory. String theory predicts extra hidden dimensions in space beyond the three we sense daily. Other models predict large extra dimensions: large enough to observe up to multi TeV scale.

Extra Dimensions? Attempts to unify gravity with other forces predicts extra dimensions. Explains why gravity appears weak. These extra dimensions could be very small, which is why we don't see them. –To a tightrope walker, the tightrope is one-dimensional: he can only move forward or backward –But to an ant, the rope has an extra dimension: the ant can travel around the rope as well

Large Extra Dimensions of Space LHC can discover partner towers up to a given energy scale. qq,gg  G N  e + e -,  +  - M ee,  [GeV] LHC M ee [GeV] DZero Tevatron GNGN qqqq e+e-e+e- Tevatron Sensitivity 2.4 CL M ee [GeV] Events / 50 GeV / 100 fb LHC

New forces of nature  new gauge boson LHC has great discovery potential for multi TeV Z’. M ee [GeV] M  [GeV] Tevatron LHC Events/2GeV qq  Z’  e + e - Tevatron sensitivity ~1 TeV CDF Preliminary Little Higgs Models ? New strong Dynamics ?

New Particles? Solution to the dark matter problem?

We are hoping in the next ~5 years we will discover Higgs. This will open windows for discovering new laws of nature. Discovering “laws of nature” is exciting!!

Physics Beyond Borders

Why high energy? E= hc (courtesy Louis de Broglie) Smallest length scale probed

Particles Tell Stories! The discovery of a new particle is often the opening chapter revealing unexpected features of our universe. Particles are messengers telling a profound story about nature and laws of nature in microscopic world. The role of physicists is to find the particles and to listen to their stories.

What is the story they may tell…

Entire new particle spectrum? Super Symmetry –Attempting to unify gravity with the other fundamental forces leads to a startling prediction: every fundamental matter particle should have a massive "shadow" force carrier particle, and every force carrier should have a massive "shadow" matter particle. ….