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# Non Baryonic Dark Matter with a Concentration on Cold Dark Matter from Supersymmetry

Ever since astronomers have been studying galaxies and their mass/luminosity relationship, there is clearly something wrong. There is a missing luminosity problem - there is a lot of non-luminous (about $$90 \%$$) matter in a galaxy. Possible dark matter candidates come from cold dark matter, warm dark matter, hot dark matter, and axions. After years of research, astronomers and physicists can rule out warm and hot dark matter, but cold dark matter and axions are both extremely probable candidates of dark matter. In this report, I will explain about all the different candidates of dark matter and their implications.

# Introduction

By studying the mass/luminosity of galaxies and planetary systems, it is clear that there is some mass missing. About $$10 \%$$ of the mass is composed of luminous material, such as stars, and there is about $$90 \%$$ of a galaxies mass unaccounted for. This non-luminous mass is called dark matter because it does not contribute to the total galaxies luminosity. Possible candidates for dark matter would be black holes, dwarf stars, different types of non-luminous gas, and planets. But, even after adding all of that mass together, there is still a huge portion of mass unaccounted for. We also know that dark matter must not interact via the electromagnetic force or we would have detected it by now. Also, we know it must interact with the gravitation force because we can see the gravitational effects of dark matter throughout the Universe. In this report, I will be studying possible dark matter candidates with a focus on cold dark matter.

# The Standard Model

## Intro to the Standard Model

In order to understand the rest of this report, it is important to understand the standard model of physics that unifies the weak, strong, and electromagnetic forces. The standard model was devised in 1970 as a way to describe particles and how they interact. As you can see in Figure 1, there are many types of fermion matter. Quarks are the smallest particle found and are what matter (protons, neutrons, and therefore atoms) are composed of. There are six different types of quarks - up, down, charmed, strange, bottom, and top. Another fundamental force is the lepton, which like Quarks, has six different flavors. All of our ordinary matter is composed of Quarks and Leptons. (7)

Another aspect of the standard model is that for each particle composed of ordinary matter, there is another particle called an anti-matter particle. For example, the electron’s anti-particle is the positron. It looks identical to an electron, except the charge is positive rather than negative. Same thing for the protons and Quarks. When a particle interacts with its anti-particle, they annihilate each other. In labs, we have been able to crate antimatter, so we are absolutely sure that antimatter exists. (7)

## Standard Model Particles

As seen in Figure 1, there are three different types of particles in the standard model: the Fermions, Gauge Bosons, and the Higgs Boson. The Fermions are the matter particles that are composed of Quarks and Leptons such as electrons, protons, neutrons, and have 1/2 integer spins. The Gauge Bosons are the force carriers and therefore carry the fundamental forces of nature - except gravity (explained below). They are Bosons and therefore have integer spins such as 0. Finally, the Higgs Boson is the mass carrier and was recently found in the Large Hadron Collider (LHC). This particle had been theorized to exist for decades, but no one could find it. Finally, after using the LHC, astronomers were able to detect the Higgs. This detection is a strong indication that the standard model is correct. (7)

## Problems with the Standard Model

As I stated above, the standard model unifies the strong, weak, and electromagnetic forces, but it does not unify gravity. This is a problem because physicists are constantly looking for a unified theory, and right now, the standard model can not provide that. So, there is a possibility that the standard model is incorrect. But for now, the standard model perfectly describes and models everything we observe and create in labs. (7)