1. Particle Physics: Status and Perspectives Part 9: Energy Frontier and Open Questions
Manfred Jeitler
SS 2015

2. Supersymmetry

3. Supersymmetry
Every fundamental matter particle should have a massive "shadow" force carrier particle, and every force carrier should have a massive "shadow" matter particle.
This relationship between matter particles and force carriers is called supersymmetry.
For example, for every type of quark there may be a type of particle called a "squark."

4. Supersymmetry (“SUSY”)

5. Cancellation of quadratic terms (divergences)
source:
to avoid quadratic divergences in Higgs mass, “fine-tuning” is needed

6. Running Coupling constants: Grand Unification
U(1) (hypercharge) SU(2) (left) SU(3) (color)
coupling constants get almost equal at high energies
but not quite, in Standard Model (left)
perfect match in Supersymmetry (right)

7. Parameters of the Standard Model
α1 = (5/3)g′2 /(4π) = 5α/(3 cos2 θW )
α2 = g2/(4π) = α/ sin2 θW
α3 = gs2/(4π)
α1(MZ) = 0.017
α2(MZ) = 0.034
α3(MZ) = ±
Parameters of the Standard Model
source:

8. dark matter: MACHOS vs WIMPS
massive astrophysical cosmic halo objects?
weakly interacting massive particles?
questions of cosmology to particle physics:
Why is there more matter than anti-matter in the universe?
What is the universe made of? What is dark matter?
What is dark energy?
answers to these questions concerning the largest scales might come from the physics of the smallest scales - elementary particle physics
matter/antimatter asymmetry:
seen in cosmological observations
fundamental for our existence
CP-violation indispensable
but the CP-violating effects known so far are much too weak
there must be other effects! (“strong CP-violation”)
dark matter and dark energy:
the mass of the universe (measured/observed from gravitational effects) is much higher than all the stars, dust, black holes and other known matter
therefore scientists are looking for this “dark matter”
MACHOS (Massive Astrophysical Compact Halo Objects) seem unlikely
WIMPS (Weakly Interacting Massive Particles) are what particle physicists are looking for
on top of this, there seems to be some extra unknown (“dark”) energy that makes the universe expand faster than it should, considering the amount of matter in it

10. How to see SUSY decays
SUSY particles may show very clear signatures due to cascade decays

11. LIGO (Laser Interferometer Gravitational Wave Observatory, USA)
measurement of gravitational waves
The gravitational interaction is so weak that the “graviton” which is supposed to mediate it has not been found yet. It is hoped to find gravitons and gravitational waves arriving from outer space (for instance from supernova explosions). The expected effects are very small and demand very accurate detectors and an extremely good compensation of interfering environmental effects.
LIGO (Laser Interferometer Gravitational Wave Observatory, USA)

12. important questions of today’s particle physics
(ongoing experiments)
• Why are particle masses so different?
• Is there an overall (hidden) symmetry such as Supersymmetry (SUSY)  “mirror world” of all known particles?.
What is the nature of “Dark Matter” and “Dark Energy” in the universe?
• Why is there more matter than anti-matter?
• Why have neutrinos such small mass?
• Is there a Grand Unification which combines all interactions, including gravitation?
• Are there extra dimensions, D > 4 ? ( string theory, …)