# teachers colloquium

Post on 19-Jan-2015

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Dheeraj Kumar SinghTRANSCRIPT

- 1. Beauty in the Universe

2. Innermost SpaceHigh Energy ParticlePhysics is a study of thesmallest pieces of matter.It investigates the deepestand most fundamentalaspects of nature.It investigates (among otherthings) the nature of theuniverse immediately afterthe Big Bang.It also explores physics attemperatures not commonfor the past 15 billion years(or so). 3. Helium NeonPeriodic TableAll atoms are madeof protons, neutronsand electrons u u u dd d ProtonNeutron Electron Gluons hold quarks together Photons hold atoms together 4. udWhile quarks have b tsimilar electric charge,they have vastly sdifferent masses (but czero size!) 5. ers ve niUWhy three dimensions? m n tuWhat gives particles theiruaQ mass? heAre there new forces andtsymmetries that we dont yet know? of srie Are the forces and particles of which we dote know just different faces of a deeper,ys unifying principle?M 6. =e2/c 7. Fermi National AcceleratorLaboratory (a.k.a. Fermilab) Begun in 1968 First beam 1972(200, then 400GeV) Upgrade 1983Jargon alert: 1 Giga Electron Volt(GeV) is 100,000 times more energy (900 GeV)than the particle beam in your TV. Upgrade 2001If you made a beam the hard way,(980 GeV)it would take 1,000,000,000 batteries 8. The Main Injector upgrade was completed in 1999. The new accelerator increases the number of possible collisions per second by 10-20. D and CDF have undertaken massiveExpectedupgrades to utilize the increased Number Huge statisticsoffor precision physicscollision rate.Eventsat low mass scales 1000 Run II began March 2001Formerly rare processesbecome high statistics 100processes10Run IIIncreased reachfor discovery physicsat highest masses1 Run I Increasing Violence of Collision 9. How Do You Detect Collisions? Use one of two large multi-purposeparticle detectors at Fermilab (D andCDF). Theyre designed to record collisions ofprotons colliding with antiprotons atnearly the speed of light. Theyre basically cameras. They let us look back intime. 10. Typical Detector Weighs 5,000 tons (Now) Can inspect 10,000,000 collisions/second Will record 50 collisions/second Records30approximately 10,000,000 bytes/ second Will record 1015(1,000,000,000,000,000)30bytes in the next50run (1 PetaByte). 11. Remarkable PhotosIn this collision, a top andanti-top quark were created,helping establish their existenceThis collision is the most violentever recorded (and fullyunderstood). It required thatparticles hit within 10-19 m or1/10,000 the size of a proton 12. Modern Cosmology Approximately 15 billion years ago, all of the matter in the universe was concentrated at a single point A cataclysmic explosion (of biblical proportions perhaps?) called the Big Bang caused the matter to fly apart. In the intervening years, the universe has beenexpanding, cooling as it goes. 13. Now(13.7 billion years)Stars form(1 billion years)Atoms form(380,000 years)Nuclei form(180 seconds)Nucleons form(10-10 seconds) 4x10-12Quarks differentiate seconds(10-34 seconds?)??? (Before that) 14. e rs ve ni UWhy three dimensions?m n tu What gives particles theiruaQmass? he Are there new forces andBack to thet symmetries that we dont yet know? ofMysteries srie Are the forces and particles of which we dote know just different faces of a deeper,ys unifying principle?M 15. In 1964, Peter Higgs postulated a physics mechanism which gives all particles their mass.This mechanism is a field which permeates the universe.If this postulate is correct, then one of thesignatures is a particle (called the Higgs Particle).Fermilabs Leon Lederman co-authored a bookon the subject called The God Particle. bottomtopUndiscovered! 16. Higgs: AnAnalogy 17. Hunting for HiggsFor technical reasons, we look for Higgs bosons in association with a W or Z boson. b jet In the region where the Higgs boson is expected, we expect itelectron to decay nearly- exclusively into b- quarksneutrino(MET)H bb 18. SymmetriesTranslationalRotational 19. More Complex Symmetries In a uniform gravitational field, a balls motion is independent of vertical translation. The origin from where potential energy is chosen is hirrelevant. 1 2 mv = mgh 2The equations of motion aresymmetric under vertical orhorizontal translations.v = 2 gh 20. Complex Familiar Symmetries yr r2r1 x1 q1q12 2qqV= 4 o | r1 r2 |r 21. Complex Familiar Symmetries yTranslations:rx x + xy y + y r2r1r2 x r11 q1q2V= 4 o | r1 r2 | 22. Complex Familiar Symmetries yReflections:rx -xy -y r2x r1 x1 q1q2V= 4 o | r1 r2 | y 23. Complex Familiar Symmetries yRotations:r r2r1 x1 q1q2V= 4 o | r1 r2 | 24. Complex Familiar Symmetries yCharge Flip:rqqr2 r1 x1 q1q21 (q1 )( q2 )V===V 4 o | r1 r2 | 4 o | r1 r2 | 25. Complex Familiar Symmetriesy rBottom Line:Electromagnetic force r2exhibits a symmetryunder: r1TranslationRotationReflection xCharge Congugation1q1q 1 (q1 )( q2 )V=(and many others) 2==V4 o | r1 r2 | 4 o | r1 r2 | 26. Fermions and BosonsFermions: matter particles integer spinBosons: force particles integer spin 27. Unfamiliar SymmetriesOne possible symmetry that is not yet observed is theinterchange of fermions (spin particles) and bosons(integral spin particles) Known equation Equation = Fermions + Bosons Interchanged equation (pink green) Equation = Fermions + Bosons 28. Unfamiliar SymmetriesOne possible symmetry that is not yet observed is theinterchange of fermions (spin particles) and bosons(integral spin particles) Fermions + Bosons+ Known equation Equation = Fermions + Bosons Interchanged equation (pink green) + Fermions + BosonsThis New=Symmetry+is calledEquation Fermions BosonsSuperSymmetry (SUSY) 29. SUSY Consequence SUSY quark squark SUSY lepton slepton SUSY boson bosino 30. The Golden Tri-lepton SuperSymmetry Signature muonsThis is the easiest toobserve signature forSUSY.electronNo excess yet observed.neutrino 31. The Conundrum of Gravity Why is gravity so much weaker(~10-35) the other forces? Completely unknown One possibility is that gravity canaccess more dimensions than the otherforces 32. The Dimensionality of Space Affectsa Forces StrengthQencl Gauss Law = E dAo 1 Qencl1 Qencl E=E=2 o r4 o r 22D3D 33. Are More Dimensions Tenable? Newtons Law of GravityGm1m2 F=2 r Clearly indicates a 3D space structure. Or does it? 34. Nature of Higher Dimensions What if the additional dimensions had adifferent shape? What if the additional dimensions weresmall? 35. Access to Additional Dimensions What if gravity alone had access to theadditional dimensions? 36. Access to Additional Dimensions What if gravity alone had access to theadditional dimensions? 37. A Model with n Dimensions. Gravity communicating withthese extra dimensions couldproduce an unexpectedlylarge number of electron orphoton pairs. Thus, analysis of theproduction rate of electronsand photon providessensitivity to these extradimensions. Large energies are requiredto produce such pairs. pe q q G pe 38. Once again there are interesting events! (way out on the mass tail.)ee pair pairelectronsphotons 39. Data-Model Comparison 40. Data-Model Comparison 41. Summary Particle physics allows us to study someof the deepest mysteries of reality. We know a whole bunch of stuff.Send students. The things we dont know, were studyinglike mad. The mysteries mentioned here areunsolved. We need help. 42. www-d0.fnal.gov/~lucifer/PowerPoint/Teacher_Colloquium.ppt 43. Available at Amazon, BarnesandNoble.com + local book stores