94465 - Theoretical Astroparticle Physics

Learning outcomes

At the end of the course the student will acquire a deep understanding of the connection between particle physics and cosmology. They will master i) the theory and phenomenology of neutrinos; ii) the theoretical aspects of dark matter; iii) the origin of the baryon asymmetry in the early Universe; iv) key aspects of the evolution of Universe including Big Bang Nucleosynthesis, the Cosmic Microwave Background radiation and large scale structure formation from a particle physics perspective; and will have a basic knowledge of the theory of gravitational waves and of cosmic rays. They will be able to present these concepts, inscribing them in the context of the Standard Model and beyond, and of the evolution of the Universe, and to apply the theoretical formalism to compute observables in experimentally relevant situations.

Course contents

1. Overview of the course. The big five in astroparticle physics: neutrino masses and neutrino role in the Early Universe, the dark matter identity, the origin of the baryon asymmetry, high energy cosmic rays, gravitational waves.

2. Background knowledge. i) Basics of cosmology: cosmological principle; Friedmann-Lemaitre-Robertson-Walker metric; Friedmann equations; Big bang and cosmological horizon; current Universe. ii) Recap of the Standard Model of particle physics: gauge theory and SM gauge group; particle content; spontaneous symmetry breaking; problems of the SM.

3. Gravitational waves. General relativity and gravitational waves: review of basic principles, the transverse-traceless gauge and the gravitational wave equation, physical and mathematical description in linearised theory, GW polarisation. GW generation and sources. GW interactions with matter and their detection.

4. The interplay between particles and interactions in the Universe. Recap of thermodynamics for astroparticle physics. Brief thermal history of the Universe: thermal bath and particle decoupling, neutrino decoupling, Big Bang nucleosynthesis, recombination, equality of matter and radiation.

5. Neutrino physics. Neutrinos in the Standard Model and beyond; Neutrino sources on Earth and in the Universe; Neutrino oscillations: Theory, brief overview of experiments, present knowledge of neutrinos and questions for the future; Nature of neutrinos: Majorana versus Dirac particles, Neutrinoless double beta decay; Brief discussion of the origin of neutrino masses beyond the Standard Model.

6. Dark Matter. Observational evidence: Rotation curves of galaxies, Virial Theorem in Galaxy Clusters, Cosmology; Dark matter production in the Early Universe: thermal equilibrium and freeze out, relic density, hot and cold dark matter, the WIMP paradigm, non-thermal production mechanisms; Dark Matter Identity: candidates in extensions of the Standard Model, WIMPs, axions, sterile neutrinos and other warm dark matter candidates, other options; Dark Matter Searches at different mass scales.

7. The matter-antimatter asymmetry. Baryogenesis in extensions of the Standard Model: Sakharov conditions, basic properties of models; Leptogenesis and neutrino mass models; Electroweak baryogenesis.

8. High energy cosmic rays. A basic review of cosmic ray physics and astrophysics, including their sources, propagation and detection. Multi-messenger astronomy connecting GW with HE cosmic rays and neutrinos.

 

For all the topics above, the focus will be first on the theoretical aspects (with emphasis on the physics concepts and the mathematical formalism), and then the observables relevant for experiments will be considered with basic computations (e.g. decay rates, cross sections, decoupling temperatures, relic densities).

Readings/Bibliography

Comprehensive notes on the course material will be made available to the students and will be provided on Virtuale at the start of the course.

Additional reading:

Astroparticle physics and cosmology:

E.W. Kolb and M.S. Turner 

The Early Universe

Westview Press, 1994

Note: Only Chpts 2, 3 and 5. The discussion on decoupling (Chpt 5) is particularly clear.

Neutrino physics: 

C. Giunti and C. W. Kim,

Fundamentals of Neutrino Physics and Astrophysics

Oxford University Press, USA, 2007

Note: Only Chpts 4, 5, 7, and 9. This is a very comprehensive and detailed presentation of the mathematical formalism of neutrinos.

Dark Matter:

M. Cirelli, A. Strumia, J. Zupan

Dark Matter

Available on the arXiv with eprint 2406.01705 [hep-ph].

Note: Very detailed and broad discussion of the current status of dark matter physics, from evidence to theory and experiments.

High Energy Cosmic Rays:

M. Spurio

Probes of multimessenger astrophysics: Charged cosmic rays, neutrinos, γ-rays and gravitational waves

[ https://www.springer.com/la/book/9783319968537 ]-

Springer DOI: 10.1007/978-3-319-96854-4

Note: Only Chpts 2, 6, 8, 10. Chpt 13 focuses on GW.

 

Alessandro De Angelis, Mário Pimenta

Introduction to Particle and Astroparticle Physics

Springer (2018)

Note: Mainly Chpt 10. Moreover, this book offers a very nice introduction to all the relevant background knowledge (e.g. QFT, cross sections, the SM, cosmology) for those who have not followed dedicated courses. 

 

Gravitational waves:

M. Maggiore

Gravitational Waves: Volume 1: Theory and Experiments

Oxford University Press, 2008

Notes: Only Chpts 1, 3 and 4.

Teaching methods

Lectures at the blackboard/online (in presence and/or remote for special circumstances), complemented by tutorials and topical seminars.

First theoretical aspects will be considered with emphasis on the physics concepts and the mathematical formalism. The observables relevant for experiments will be studies and basic computations (e.g. decay rates, cross sections, decoupling temperatures, relic densities) will be carried out.

 

Students with learning disabilities or temporary or permanent disabilities: please contact the relevant University office promptly (https://site.unibo.it/studenti-con-disabilita-e-dsa/it ). The office will advise students of possible adjustments, that will be submitted to the professor for approval 15 days in advance. He/she will evaluate their suitability also in relation to the academic objectives of the course.

Assessment methods

Oral examination is in two parts: i) a presentation of an advanced topic (typically including a brief review of the topic of the course and a more advanced part based on a recent research article) with slides (8' of duration). You should read the article understanding the basic science (what is the problem the article is trying to address? What are the key results?) and making your own critical assessment of it (are the results general? are they interesting? and if so, why? It is useful to read carefully the introduction and the conclusions for this purpose). You are not required to reproduce the results obtained in the article (for example formulas or plots). ii) Questions on two other topics of the course.

The exam lasts approximately 30 minutes.

The purpose of the oral exam is to assess the student's ability to apply their knowledge and make the necessary logical-deductive connections. Final grade:

• Presentation on material discussed in class with limited evidence of understanding of the topic. Very limited preparation on a few topics covered in the course, and analytical skills that emerge only with the instructor's assistance; overall correct language → 18-22;
• Presentation primarily on material discussed in class (and possibly further study) with good evidence of understanding of the topic. Limited preparation on various topics covered in the course, and independent analysis skills only on purely executive questions; overall correct language → 22-24;
• Presentation on material discussed in class and its more advanced study with very good/excellent evidence of understanding. Very good/excellent preparation on various topics covered in the course, ability to make independent critical analysis choices, and mastery of specific terminology → 25-29;
• Presentation on material discussed in class and its more advanced study, demonstrating excellent understanding of the topic. Excellent preparation on the topics covered in the course, ability to independently make critical analysis and connections to solve previously unseen problems, full command of specific terminology, and ability to argue and self-reflect. → 30-30L.

Students with learning disabilities or temporary or permanent disabilities: please contact the relevant University office promptly (https://site.unibo.it/studenti-con-disabilita-e-dsa/it ). The office will advise students of possible adjustments, that will be submitted to the professor for approval 15 days in advance. He/she will evaluate their suitability also in relation to the academic objectives of the course.

Teaching tools

The course will avail itself of various tools:

• lecturing on blackboard;

• slides with the material presented on the blackboard;

• web resources for further reading.

Office hours

See the website of Silvia Pascoli