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Why Large Hadron Collider?

Why Large Hadron Collider?

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Why Large Hadron Collider?

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  1. Why Large Hadron Collider? ROY, D. (2011). Why Large Hadron Collider?. Pramana: Journal Of Physics, 76(5), 741-756. doi:10.1007/s12043-011-0083-6

  2. High Energy colliders • Usually accelerate particle and an antiparticle beams . • They have identical orbits in in same vacuum pipe on top of one another. • Made to collide with a magnetic switch • Detector observes the particles coming out of the collision • Electron-antielectron – more precision • Proton-antiproton – less expensive

  3. Large Hadron Collider • Proton-proton collider • Gives high luminosity than proton-antiproton • Allows production of collision with energy greater than the current limit ~2Tev • Why do we want to do this? Stay tuned!

  4. THE FERMIONS: • Three pairs of leptons • (electron, muon, tau, plus their neutrinos) • These vary in mass, electric charge, and color charge. • Three pairs of quarks • (up, down, strange, charm, bottom, top) • Quarks make up the proton and neutron, so together with the electron, they make up all visible matter in the universe!

  5. The Standard Model

  6. Bosons: Force carrier particles • Four Gauge Bosons: • γ (photon) – electromagnetic force • g (gluon) – strong force • Z – weak force • W± - weak force • H0 Higgs Boson – responsible for Higgs fieldWhen particles interact with Higgs field, they acquire mass.Existance needs to be confirmed. • Note: The gravitron is purely hypothetical and could be a gauge boson. It is not currently incorporated.

  7. A couple of background concepts • Lagrangian– summarizes the dynamics of a system • L = T – V (kinetic energy – minus potential energy) • Leads to conservation laws • Not taught in high school because 3D calculus is used • Usually the time integral is used: • S = ∫L dt

  8. Gauge Symmetry • Results from conservation of a quantity • Gauge transformation = transformation of a field from one configuration to another • Observable quantities (mass, charge, energy, velocity etc.) do not change even when the field they are derived form does change (invariance)

  9. Back to Bosons and LHC

  10. The problem • If a gauge boson mass term is added to the Lagrangian, the invariance is broken. • Somehow, the weak gauge boson must have mass without breaking the gauge symmetry of the Lagrangian. • Note: Everything here (As well as in the “solution”) is proven mathematically, and no simple way to explain here.

  11. The Solution • Higgs Mechanism of spontaneous symmetry breaking provides the answer by giving mass through a “back door” • The math demonstrates that Higgs Boson (responsible for the mechanism) has mass. • This leads to a minimal supersymmetric extension of the Standard Model (MSSM)

  12. Solution continued • Spontaneous symmetry breaking – symmetry broken at ground state of a system, but otherwise kept by Lagrangian. • Two Higgs doublets give mass to the upper and lower fermions

  13. But. . . • The Higgs Boson can also interact with other particles, which produces divergences. (Other interactions “work” that should not.) • Supersymmetry (symmetry between fermions and bosons) causes these unwanted effects to cancel out.

  14. Fermions have bosionicsuper partners and vice versa. • Quark-squark, lepton-slepton, photino, gluino, wino, zino, Higgsino • I am not making this up, honestly! The Large Hadron collider will allow us to investigate this.

  15. What is Dark Matter? • Dark matter is a type of matter that scientists believe to make up a large part of the total mass (84 %) in the universe. • Dark matter does not emit or absorb Electromagnetic radiation (including light). So it cannot be “seen”. • We believe it exists because of its gravitational effects on visible matter and radiation.

  16. What dark matter is NOT: • Antimatter • Dark Energy • Dark Fluid • Dark Flow • Negative matter • These are all completely different things.

  17. Possible explanation for Dark Matter • The lightest Superparticle (LSP) is stable and an admixture of photino and zino. • LSP is the leading candidate for cosmic matter • (Better referred to as invisible matter) • The large Hadron Collider would help us to find these particles.

  18. Some Universe History • When the universe formed, super particles decayed into LSP’s until the dark matter density reached a critical level. • Hubble expansion caused them to not collide - the freeze-out point • Dark Matter content of the universe has remain frozen since this point. • Dark Matter particles started clumping due to gravity, (EM had no effect on them) – protogalaxies • After separating from EM radiation, “ordinary” matter was attracted to these.

  19. In Conclusion • The Large Hadron Collider will allow us to search for the Higgs Boson and superparticles by producing collisions of 2 -3 Tev. • They will either be discovered or we will have clues for an alternative model. (There are some other models out there, and their predicted particles could also be found by the LHC) • The discovery of superparticles, and therefore SUSY, will help us understand dark matter better.