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Physics at the TeV Scale Particles and forces The known particle spectrum The need for TeV energies The origin of mass The path to Grand Unification Supersymmetry.

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Presentation on theme: "Physics at the TeV Scale Particles and forces The known particle spectrum The need for TeV energies The origin of mass The path to Grand Unification Supersymmetry."— Presentation transcript:

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2 Physics at the TeV Scale Particles and forces The known particle spectrum The need for TeV energies The origin of mass The path to Grand Unification Supersymmetry Conclusions Phil Allport University of Liverpool

3 Particle physics studies the fundamental building blocks of nature and their interactions. The 20th Century yielded: an explosion of particles and interactions a beautiful explanation in terms of symmetries hints of deeper unity in nature. We are on the verge of a revolution in understanding: new forces and symmetries (super-symmetries ?) complexity turned to simplicity the origin of mass, unification of the forces Einsteins dream of deeper unification (Gravity?) Introduction

4 + Forces in Physics Classically, forces are described by + Field chargesand fields + +

5 Forces in Physics Continuous field exchange of quanta Low energies and large distances classical mechanics ++ For Electromagnetism The quanta are photons, Other forces are mediated by other particles... High energies and small distances quantum mechanics Forces in Particle Physics

6 The Forces of Nature Gravity Nucleus Atom Gluon, g W Z 0 Photon, Not directly accessible at accelerators -decay, sunshine Mass GeV 91 GeV Electro- magnetic: Strong: Weak: Mediator Spin They are all bosons (integer spin)

7 Positron Mediation of the Forces Electron Feynman Diagram The strength of the force

8 The Matter Particles e Neutrino Electron Proton mass m p = kg size ~ m charge +1 mass ~ m p ? size = 0 ? charge 0 Mass ~ m p size =0 ? charge -1 u u d (Neutron)(charge 0)

9 Leptons charge = 0 charge = - 1 The First Generation e uu d d u d e Quarks with 3 colours charge = + 2/3 charge = - 1/3 velocity All these matter particles are spin-1/2 Left HandedRight Handed all are fermions 2 helicity states

10 The Dirac Equation Special Relativity + Quantum Mechanics An equation that describes spin-1/2 particles Correct magnetic moments Predicted the existence of antimatter A further doubling of the spectrum... centenary

11 The First Generation uu d d u d e e ucuc ucuc dcdc dcdc ucuc dcdc ecec -t c tctc tb tctc tb tb c bcbc bcbc bcbc -u c ucuc ud ucuc ud u d ecec dcdc dcdc dcdc e e Multiplicity of states Completion of a pattern? -u c ucuc ud ucuc ud u d ecec dcdc dcdc dcdc e e -c cc cs c cs cs c scsc scsc scsc Cosmic rays Accelerators s Number of generations = ?...

12 Precision e + e - Measurements N gen = LEP : e + e -, E cms ~ 210 GeVLHC : pp, E cms ~ 14 TeV CERN

13 u d The Known-Particle Spectrum GeV ? E scale GeV e GeV e 2 GeV u d s c 200 GeV s c b t Spin ½Spin 1, g Z0Z0 W Spin 0 ?

14 In high energy physics, the existence of at least one fundamental spin-0 `Higgs particle is required to consistently explain how particles have mass. But what about Spin-0? The Large Hadron Collider (LHC) accelerates counter-rotating bunches of protons in two 27km rings to 7 TeV and collides them at 4 interaction regions instrumented with 4 giant detector systems. Two `General Purpose Experiments are designed to find such Higgs particles over the full range of masses (0.1 to 1TeV) allowed by current theoretical and experimental results.

15 The ATLAS experiment is 26m long, stands 20m high, weighs 7000 tons and has 200 million read-out channels. One of these is ATLAS. It is being built by a collaboration of 2000 physicists from nearly 200 different institutes in 33 different countries including 13 UK universities.

16 The ATLAS central tracker is made of thousands of modules which each require several thousand connections This double-sided module has 6144 connections and has 1536 read-out channels. The required connections are at pitch down to 240 per cm

17 New matter particle charge = ? mass = ? New force carrier particle mass = ? Energy (E = m c 2 ) Positron spin=½ spin = ? Spin structure ? spin = ? Initial spin Energy precision Initial spin precision Luminosity (particle flux) Mediation of the Forces Electron spin ½

18 Energy (E = m c 2 ) Initial spin Energy precision Initial spin precision Luminosity (particle flux) The Linear e + e - Collider cm -2 s GeV ~ 0.5% P el ~ 80 %, P pos ~ 60 %

19 Precision at e + e - Colliders E, pE, - p e+ e-e- E tot =2E p tot =0 Broad Reach at Proton Colliders p p E, p E, - p d u E tot =? P tot =? Polarization No polarization Event Energy Precise Broad Range of Event Energies

20 Energy Complementarity LHCLinear Collider Energy

21 Need for a High Precision Detector Excellence Tracking Calorimetry Vertexing Granularity Hermeticity

22 Precision studies of the top-quark Physics Opportunities at the TeV Scale Precision studies of the origin of mass Supersymmetry Grand Unification New spatial dimensions Strong Electroweak Symmetry Breaking Compositeness Leptoquarks Anomalous couplings GigaZ...

23 Precision Measurement of the Top Mass Precision measurement of fundamental particle properties The top quark is the heaviest: most sensitive to new physics E tot (GeV) Cross section (pb) Statistical Precision ~0.05 GeV 0.02% M top =175 GeV 100 fb -1 per point

24 00 00 Origin of Mass ? 1. Start with a mass-less particle 2. Introduce a new field H that interacts with the particle 3. Let H be non-zero in the vacuum m=0, v = speed of light H H H H V 0

25 Should be < ~200 GeV Hint of a signal at mass=115 GeV ? Discover a Higgs Particle Measure its mass The vacuum has no preferred direction the Higgs must be spin 0 Measure its spin Every field has quanta The decay amplitude m Measure its lifetime Measure branching ratios H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H h H m H m Clear Predictions from Higgs Theory h

26 The vacuum potential The Higgs Mechanism Energy shape h hh Discover a Higgs Particle. Measure its mass. Measure its spin. Measure its lifetime. Measure its branching ratios. Measure the shape of potential Measure the shape of potential. Yes (Even if decays invisibly) Yes to high precision (0.05%) Yes (few %) Yes Yes (few %) Yes (~20 %)

27 Higgs discovered before the LHC ? Yes No Yes No Explore quantum level (GigaZ) No Explore! Yes Light higgs: Super- symmetry? Precision measurements Invisible Higgs ? New physics ? No-Lose for TeV Colliders

28 Unification of the Forces The strength of the force Three Forces 1, 2, 3 1/ 1 ~ 60 1/ 2 ~ 30 1/ 3 ~ 10 Could there be one unified force? Need to extrapolate to ultra-high energies...

29 (Energy) The Vacuum Higgs field The Vacuum is exceedingly complex Particle properties depend on energy scale The entire particle spectrum contributes Virtual particles (quantum effects) What remains after all the atoms have gone ?

30 The masses and couplings are fundamental physical quantities They enter the procedure for extrapolation to ultra-high energy scales i -1 Log 10 [Energy Scale (GeV)] Simple Grand Unification ? Before precision e + e - After precision e + e Either: No Grand Unification or: more particles... The Need for Precision TeV scale supersymmetry? Precision Measuremets

31 A further doubling of the particle spectrum eLeL ee A Candidate: Supersymmetry A symmetry relating fermions with bosons -u c ucuc ud ucuc ud u d ecec d dcdc dcdc e e eReR ucuc ud ucuc ud u d ecec d dcdc dcdc e e Spin ½ ? 0 Spin GeV~ 1 TeV E scale t t Necessary Tasks Produce the particles ( E = mc 2 ) High Energy, high luminosity Measure to high precision their mass, spin, couplings, decay channels High precision, polarization Combine e + e - and pp measurements Complementarity

32 Simplicity at Ultra-High Energy Scales s s 10 3 GeV10 15 GeV Complexity Simplicity New fine structures ? Age of Universe Energy Scale

33 The Need for Precision LHC OnlyLHC + LC Supersymmetric Mass Terms (GeV) 0 Log 10 [Energy Scale (GeV)] TeV scale measurements U1U1 L1L1 E1E1 Does gravity mediate with the superworld ?

34 Summary Particle physics explores: the fundamental forces An e + e - linear collider, building on the results from the LHC, will be uniquely placed for: Searches for new particles and forces Detailed tests of the origin of mass Precision measurements explore the physics of ultra-high energy scales the interface between gravity and particle physics? the fundamental building blocks of matter The richness and diversity of this programme make the combined potential of both a pp and an e + e - TeV collider vital for particle physics.


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