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

Supersymmetry

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."

Supersymmetry (“SUSY”)

Cancellation of quadratic terms (divergences) source: http://arxiv.org/abs/hep-ph/0012288v2 to avoid quadratic divergences in Higgs mass, “fine-tuning” is needed

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)

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) = 0.118 ± 0.003. Parameters of the Standard Model source: http://physics.stackexchange.com/questions/65149/is-the-fine-structure-constant-a-parameter-of-the-standard-model

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

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

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)

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, …)