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Hunting for New Particles & Forces
Example: Two particles produced • Animations: • QPJava-22. html u u d u
Example: Dark Matter Particle produced • Animations: • QPJava 23. html u u d u
Physics at the Tevatron mb b - observed nb pb WH, ZH Total Inelastic jets (qq, qg, gg) bb 3 x 1014 W Z tt WZ 6 x 107 2 x 107 Higgs 2 x 1011 28, 000 Single Top 16, 000, 12, 000 4000 ~ 400 ~ 40 fb - - 100 Tevatron 120 140 160 180 Higgs Mass [Ge. V/c 2] 200
Tevatron Cross Sections Total inelastic cross section. Light quarks are ubiquitous. Plenty of W and Z bosons → calibration. Recent evidence of single top quark production is an important milestone towards the Higgs boson. The Higgs cross section is 10 -11 orders of magnitudes lower than the total inelastic cross section.
Tevatron: Improve Higgs Mass Pred. via Quantum Corrections 80. 5 W bottom M hi gg s = 80. 4 10 20 0 G 30 0 G e. V 5 0 e 10 00 Ge V 00 G V G e. V MW (Ge. V) top 80. 3 Higgs W 150 175 200 Mtop (Ge. V) 1 Ge. V = 1 Ge. V / c 2 ~ proton mass
Clues to the Higgs ? Tevatron: Higgs Mass Prediction via Quantum Corrections top bottom MW (Ge. V) Higgs Z W top W, Z Tevatron Run II Mtop (Ge. V) MH = 92+45 -32 Ge. V; MH < 186 @ 95% CL
Clues to the Higgs ? Tevatron: Higgs Mass Prediction via Quantum Corrections MH = 76+33 -24 Ge. V; 114 < MH < 182 @ 95% CL Winter 2007
Higgs boson production @ Tevatron • Associated Production • m. H < 135 Ge. V – (W, Z+H) ¼ 0. 15 pb H bb • Gluon fusion • m. H > 135 Ge. V – (H) ¼ 0. 45 pb H WW
Higgs boson decays • H ff, WW, ZZ – couples to mass; – heaviest final state dominates • m. H < 135 Ge. V – H bb • m. H > 135 Ge. V – H WW Tevatron can explore bb and WW( ℓ+ℓ-nn) decay modes
SM Higgs: Event Signatures m. H<135 Ge. V m. H>135 Ge. V
Status of Direct Search for Higgs boson • 2010: 8 fb-1 – Exclude 115 < m. H < 125 Ge. V and 150 <m. H < 180 Ge. V
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 LHC: Designed to discover Higgs with Mhiggs = 100 ~ 800 Ge. V LHC MW (Ge. V) # of events / 0. 5 Ge. V Tevatron Mtop (Ge. V) 130 Ge. V Higgs L = 100 fb-1 M (Ge. V)
Tevatron: Improve Higgs Mass Pred. via Quantum Corrections LHC: Designed to discover Higgs with Mhiggs = 100 ~ 800 Ge. V LHC MW (Ge. V) 5 Discovery Luminosity (fb-1) Tevatron Mtop (Ge. V) MHiggs (Ge. V)
Tevatron: Improve Higgs Mass Pred. via Quantum Corrections LHC: Designed to discover Higgs with Mhiggs = 100 ~ 800 Ge. V LHC MW (Ge. V) 5 Discovery Luminosity (fb-1) Tevatron Mtop (Ge. V) hard easy MHiggs (Ge. V) Will the Tevatron’s prediction agree with what LHC sees?
Higgs in Minimal Supersymmetric Extension of Standard Model Tevatron LHC MS Tevatron LHC Mtop (Ge. V) tan MW (Ge. V) SM MA (Ge. V) LHC will be the best place to discover Higgs particles!
Unification of the Forces
Unification 2. 3 x 10 -13 Ge. V (2. 7 K) 12 x 109 y 1 Te. V = 103 Ge. V (1016 K) 10 -11 s 1016 Ge. V 1019 Ge. V (1029 K) (1032 K) 10 -38 s 10 -41 s Energy Temp Time 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.
Unification of electromagnetic & weak forces (electroweak theory) Ele ctr om ag Weak Forc e ne tic HERA: HERA Fo rce 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 f Q 2 [Ge. V 2] H 1 + ZEUS
13 orders of magnitude higher energy 60 40 -1 20 0 -1 -1 104 108 1012 1016 Q [Ge. V] 1020 The Standard Model fails to unify the strong and electroweak forces.
60 With SUSY -1 40 -1 20 0 -1 104 108 1012 1016 Q [Ge. V] 1020
Unifying gravity with the other 3 is accomplished. With by string theory. SUSY 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 Te. V 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 Tevatron GN q e+ e- Tevatron Sensitivity 2. 4 Te. V @95% CL qq, gg GN e+e-, + 2 10 Events / 50 Ge. V / 100 fb-1 q LHC 10 1 10 -1 DZero 10 -2 Mee [Ge. V] Mee, M [Ge. V] ee [Ge. V] LHC can discover partner towers up to a given energy scale.
New forces of nature new gauge boson Little Higgs Models ? New strong Dynamics ? Tevatron Events/2 Ge. V 104 LHC qq Z’ e+e- 103 Tevatron sensitivity ~1 Te. V 102 CDF Preliminary 10 1 10 -1 Mee [Ge. V] M [Ge. V] LHC has great discovery potential for multi Te. V Z’.
New Particles? • Solution to the dark matter problem?
Discovering “laws of nature” is exciting!! We are hoping in the next ~5 years we will discover Higgs. This will open windows for discovering new laws of nature.
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. …. http: //www. particleadventure. org