M. Pimenta

Basics of Particle Physics

This chapter introduces the basic techniques for the study of the intimate structure of matter, described in a historical context. After reading this chapter, you should understand the fundamental tools which led to the investigation and the description of the subatomic structure, and you should be able to compute the probability of occurrence of simple interaction and decay processes. A short reminder of the concepts of quantum mechanics and of special relativity needed to understand astroparticle physics is also provided.

LATTES: a novel detector concept for a gamma-ray experiment in the Southern hemisphere

The Large Array Telescope for Tracking Energetic Sources (LATTES), is a novel concept for an array of hybrid EAS array detectors, composed of a Resistive Plate Counter array coupled to a Water Cherenkov Detector, planned to cover gamma rays from less than 100 GeV up to 100 TeVs. This experiment, to be installed at high altitude in South America, could cover the existing gap in sensitivity between satellite and ground arrays. The low energy threshold, large duty cycle and wide field of view of LATTES makes it a powerful tool to detect transient phenomena and perform long term observations of variable sources. Moreover, given its characteristics, it would be fully complementary to the planned Cherenkov Telescope Array (CTA) as it would be able to issue alerts. In this talk, a description of its main features and capabilities, as well as results on its expected performance, and sensitivity, will be presented.

The study on the potential of muon measurements on the determination of the cosmic ray composition using a new fast simulation technique

In this work we study the energy evolution of the number of muons in air showers. Motivated by future plans for UHECR experiments, the analysis developed here focuses on how the evolution of the moments of the distributions of two shower observables, the depth of the shower maximum Xmax and the number of muons on the ground (Nm ), can be used to assess the validity of a mass composition scenario, surpassing the current uncertainties on the shower description. The cosmic ray composition is an essential ingredient for an astrophysical interpretation of the data. However, the inference of composition from air shower measurements is limited by the theoretical uncertainties on the high energy hadronic interactions. Statistical analyses using the energy evolution of different observables, like the moments of the Xmax and of the moments of the Nm distributions, can provide an efficient method to overcome these limitations providing more reliable information about the cosmic ray abundance. A new technique is presented here to generate a large set of simulated shower observables minimizing computer processing time. Fast algorithms to simulate the longitudinal development of the shower (i.e. CONEX) have longbeen available. However, the Nm is measured along the lateral development of the shower, which implies that three-dimensional simulations are needed (i.e. CORSIKA). This paper presents a parameterization of the main shower characteristics that can be used to simulate the number of muons on the ground using fast simulation algorithms. The parametrization was used to predict the evolution of log 10 Nm moments by possible hypothetic mass composition scenarios.

Messengers of the High Energy Universe

By combining observations of a single phenomenon using different particles, it is possible to achieve a more complete understanding of the properties of the sources; this approach is known as multi-messenger astrophysics. Multi-messenger astrophysics uses mostly information coming from charged particles and from photons at different wavelengths; in the recent years it has been dominated by the discoveries due to high-energy gamma rays, and it might soon incorporate new information from neutrinos and gravitational radiation.

The Properties of Neutrinos

This chapter is dedicated to the physics of neutrinos, which are neutral particles, partners of the charged leptons in SU(2) multiplets, subject to the weak interaction only—besides the negligible gravitational interaction. Due to their low probability of interaction, they are very difficult to detect and as a consequence the neutrino sector is the less known in the standard model of particle physics. In the late 1990s it has been discovered that neutrinos of different flavors (electron, muon, or tau) “oscillate”: neutrinos created with well-defined leptonic flavor may be detected in another flavor eigenstate. This phenomenon implies that neutrinos have a nonzero—although tiny even for the standards of particle physics—mass.

The Standard Model of Cosmology and the Dark Universe

This chapter introduces the observational data on the structure, composition, and evolution of the Universe, within the framework of the theory of general relativity, and describes the model currently providing the best quantitative description. In particular, we will illustrate the experimental evidence suggesting the existence of new forms of matter of energy, and describe the expansion, the chemical evolution, and the formation of structures, from the beginning of time—that, we believe, started with a phase transition from a singularity: the “big bang”.

The Birth and the Basics of Particle Physics

This chapter introduces the basics of the techniques for the study of the intimate structure of matter, described in a historical context. After reading this chapter, you should understand the basic tools which lead to the investigation and the description of the subatomic structure, and you should be able to compute the interaction probabilities of particles. A short reminder of the concepts of special relativity needed to understand astroparticle physics is also provided.

Cosmic Rays and the Development of Particle Physics

This chapter illustrates the path which led to the discovery that particles of extremely high energy, up to a few joule, come from extraterrestrial sources and collide with Earth’s atmosphere. The history of this discovery started in the beginning of the twentieth century, but many of the techniques then introduced are still in use. A relevant part of the progress happened in recent years and has a large impact on the physics of elementary particles and fundamental interactions.

The Higgs Mechanism and the Standard Model of Particle Physics

The basic interactions affecting matter at the particle physics level are electromagnetism, strong interaction, and weak interaction. They can be unified by a Lagrangian displaying gauge invariance with respect to the SU(3)\(\otimes \) SU(2) \(\otimes \) U(1) local symmetry group; this unification is called the standard model of particle physics. Within the standard model, an elegant mechanism, called the Higgs mechanism, accounts for the appearance of masses of particles and of some of the gauge bosons. The standard model is very successful, since it brilliantly passed extremely accurate precision tests and several predictions have been confirmed—in particular, the Higgs particle has been recently discovered in the predicted mass range. However, it can hardly be thought as the final theory of nature: some physics beyond the standard model must be discovered to account for gravitation and to explain the energy budget of the Universe.

Particles and Symmetries

Symmetry simplifies the description of physical phenomena, in such a way that humans can understand them: the Latin word for “understanding,” capere, also means “to contain”; and as we are a part of it we cannot contain the full Universe, unless we find a way to reduce its complexity–this is the meaning of symmetry. Symmetry plays a particularly important role in particle physics, as it does in astrophysics and in cosmology. The key mathematical framework for symmetry is group theory: symmetry transformations form groups. Although the symmetries of a physical system are not sufficient to fully describe its behavior—for this purpose, one needs a complete dynamical theory—it is possible to use symmetry to discover fundamental properties of a system. Examples of symmetries include space–time symmetries, internal symmetries of particles, and the so-called gauge symmetries of field theories.