The Mysteries of Particle Physics and how we are trying to solve them Owen Long, UC Riverside July 27, 2017 QuarkNet Workshop

Our "Standard Model" of Particles

Our "Standard Model" of Particles We are made of these… … and held together by these

Our "Standard Model" of Particles We are made of these… … and held together by these This allows some unstable nuclei to decay (radioactivity).

Our "Standard Model" of Particles We are made of these… … and held together by these This allows some unstable nuclei to decay (radioactivity). These are like ghosts. They weigh almost nothing and hardly interact at all.

Our "Standard Model" of Particles These are extra copies of the matter particles. We don't know why they are there. We are made of these… … and held together by these This allows some unstable nuclei to decay (radioactivity). These are like ghosts. They weigh almost nothing and hardly interact at all.

Our "Standard Model" of Particles These are extra copies of the matter particles. We don't know why they are there. The Higgs field gives particles what we call mass. We are made of these… … and held together by these This allows some unstable nuclei to decay (radioactivity). These are like ghosts. They weigh almost nothing and hardly interact at all.

The "Standard Model" of particles No Standard Model particles left to look for. Are we done? No!

The "Standard Model" of particles No Standard Model particles left to look for. Are we done? No! Some Mysteries of Particle Physics What is Dark Matter? Where did the antimatter go (or why are we here)? Is there a Grand Unified Theory? Are there more than three space dimensions? Why is the Higgs boson so light?

Extra Dimensions? Might explain why gravity is so weak.

Extra Dimensions? Might explain why gravity is so weak.

Why is the Higgs boson light? We found the Higgs Boson and measured it's mass: 125 GeV. If the Standard Model is all there is, we know how to calculate radiative corrections to its mass.

Why is the Higgs boson light? We found the Higgs Boson and measured it's mass: 125 GeV. If the Standard Model is all there is, we know how to calculate radiative corrections to its mass. Problem: size of corrections are much larger (~1018) than the mass we found

Why is the Higgs boson light? We found the Higgs Boson and measured it's mass: 125 GeV. If the Standard Model is all there is, we know how to calculate radiative corrections to its mass. Problem: size of corrections are much larger (~1018) than the mass we found Huge uncorrected mass Small observed mass Equally huge correction

Why is the Higgs boson light? We found the Higgs Boson and measured it's mass: 125 GeV. If the Standard Model is all there is, we know how to calculate radiative corrections to its mass. Problem: size of corrections are much larger (~1018) than the mass we found Several ideas on what New Physics would give a more natural explanation. One is Supersymmetry. Huge uncorrected mass Small observed mass Equally huge correction

Supersymmetry : 3 birds with 1 stone "The systematic cancellation of [dangerously large radiative corrections to the Higgs mass] can only be brought about by the type of conspiracy that is better known to physicists as a symmetry." Steve Martin (the physicist, not comedian) Every Standard Model particle gets a supersymmetric partner.

Supersymmetry : 3 birds with 1 stone "The systematic cancellation of [dangerously large radiative corrections to the Higgs mass] can only be brought about by the type of conspiracy that is better known to physicists as a symmetry." Steve Martin (the physicist, not comedian) Every Standard Model particle gets a supersymmetric partner. Potentially solves 3 mysteries: Cancellation of huge Higgs mass corrections. Could be Dark Matter Consistent with grand unification of the strong, electromagnetic, and weak forces (unlike the Standard Model).

Searching for Supersymmetry The lightest SUSY particle is stable and weakly interacting. It could be what Dark Matter is made of. Carries away momentum without leaving a trace in the detector.

Summary Our job in particle physics is far from complete. The Large Hadron Collider is at the frontier of fundamental physics. The CMS experiment is our microscope, probing the shortest distance scales ever examined in a laboratory.