Theoretische Physik (Antusch)Head of Research Unit Prof. Dr.Stefan AntuschOverviewMembersPublicationsProjects & CollaborationsProjects & Collaborations OverviewMembersPublicationsProjects & Collaborations Projects & Collaborations 5 foundShow per page10 10 20 50 Effective field theory and open quantum system approach for dark matter dynamics in the early universe Research Project | 1 Project MembersOne of the major challenges in cosmology is to understandthe matter content of our universe. According to General Relativity (GR) there are deep connections between what fills the universe and its geometry, its dynamical expansion and eventually its fate. Notably, visible ordinary matter appears to be only a small fraction of the matter in our universe, whereas the bulk comes in the form of non-luminous and non-baryonic particles, dubbed dark matter (DM). Complementary measurements of large scale structures, galaxy formation, gravitational lensing and of the cosmic microwave background (CMB) strongly suggest that more than 80% of the matter in the universe consists of DM.The most accurate determination for ordinary matter and DM energy density are provided by anisotropies in the CMB and amount to $Omega_{hbox{scriptsize B}} h^2 = 0.02237 pm 0.00015$ and $Omega_{hbox{scriptsize DM}} h^2 = 0.1200 pm 0.0012$.On the contrary, there is almost a total lack of information concerning DM fromthe particle physics point of view. Over the last few decades, a Weakly Interacting Massive Particle (WIMP) has become the most studied candidate for DM. One of its key features is the production mechanism in the early universe via the so-called textit{freeze-out} of a thermal relic. For a DM particle of mass $M$, the freeze-out occurs at a temperature $T sim M/25$, i.e. the DM particles are textit{non-relativistic}. However, the freeze-out mechanism is not limited to WIMPs and even applies to cases where interactions are stronger.The key quantity that governs the evolution of the DM abundance is the thermally averaged annihilation cross section $langle sigma v rangle_{{rm{ann}}}$, encompassed in a Boltzmann equationbegin{equation}(partial_t + 3H) n = -langle sigma v rangle_{{rm{ann}}} (n^2-n^2_{{rm{eq}}}) , ,label{Boltzmann_1}end{equation} where $H$ is the Hubble rate and $n$ is the total number density of DM particles ($n_{{rm{eq}}}$ is that in equilibrium). The value of $langle sigma v rangle_{{rm{ann}}}$ depends on the model under consideration, namely its particle content and interactions. It is extremely important to calculate $langle sigma v rangle_{{rm{ann}}}$ accurately because the predicted present-day DM energy density depends crucially on it through the solution of eq.~(ref{Boltzmann_1}). The DM mass is in turn fixed as function of the other model parameters to reproduce $Omega_{hbox{scriptsize DM}} h^2$ in the first place (e.g.~couplings, mass splitting with other dark species). However, determining $langle sigma v rangle_{{rm{ann}}}$ by including the full features of each model and the thermal environment is not an easy task. In a variety of theories, DM interacts with gauge bosons or scalars that induce long-range interactions because of repeated soft exchanges. Remarkably, the inclusion of bound-state effects for DM annihilation has been recently shown to have a large impact on the textit{overclosure bound} for DM models, namely the largest value of the particle mass compatible with the observed DM energy density. At the same time, it is manifestly subtle and complicated to include bound-state dynamics in a thermal medium due to the intricate interplay between non-relativistic and thermal energy scales. The overall objective of the project is to develop and apply a novel approach for relic density computations in the framework of non-relativistic effective field theories (NREFTs) and open quantum systems (OQSs). Starting from a thermal field theoretic formulation of the problem, the interactions between the DM and the light plasma constituents will systematically be included: textit{bound-state formation and dissociation}, Sommerfeld effect, DM thermal masses and interaction rates, and the role of textit{phase transitions} during the freeze-out process. I will provide the DM annihilation cross sections and overclosure bounds for well-motivated classes of models: DM coannihilating with strongly interacting states (QCD-like), DM embedded in spontaneously broken Abelian and non-Abelian gauge gauge theories, composite DM. To this aim cutting-edge effective field theory (EFT) techniques at finite temperature will be used, in particular NREFTs and potential NREFTs (pNREFTs). Moreover, DM particles in medium will be recast in an open-quantum-system framework for the first time, with a focus on DM bound-state formation and their in-medium evolution. By adopting and exploiting such methods, the corresponding overclosure bounds on the DM mass will serve as comprehensive and solid benchmarks to interpret and guide experimental analyses for a wide class of DM models. In the contemporary endeavour of testing and possibly falsifying WIMP-like models with present and upcoming experiments, the outcomes of this project are timely and necessary in order to deliver the most reliable relic density constraints on the models parameters, especially on the DM mass. Matter, Forces and the Universe Research Project | 5 Project MembersThe aim of the research project is the development and precision testing of models beyond the Standard Models of particle physics and cosmology, towards a more fundamental theory of Matter, Forces and the Universe. To identify possible building blocks of a more fundamental theory, and to investigate how to probe them with the data of future experiments, my research project focuses on three challenges, associated with three subprojects. Subproject A: One of the great challenges of the present Standard Model (SM) of elementary particle physics is the origin of neutrino masses. In subproject A we plan to contribute towards resolving this open question by investigating systematically how the mechanism of neutrino mass generation can be probed best in future experiments, in particular at possible future electron-positron, proton-proton and electron-proton colliders such as the ILC, FCC-ee, CLIC, CEPC, HL-LHC, FCC-hh/SppC, LHeC and the FCC-eh. Subproject B: Towards the challenge of identifying a more fundamental theory framework behind the SM of elementary particles, subproject B will contribute to the development of (more) predictive Grand Unified Theory (GUT) models, exploring for instance new classes of models in SO(10), as well as to the development of tools for their precision analysis (focusing on GUT predictions for baryon number violating nucleon decays, sparticle masses and neutrino properties). Subproject C: When constructing models for the early universe, one of the great challenges is linking the phase of cosmic inflation to the later phase of the universe where, e.g., the matter-antimatter asymmetry and the dark matter are produced. In subproject C we will contribute to clarifying this link by calculating the intermediate "reheating phase", including the production of gravitational waves and non-perturbative phenomena like "oscillons", after particle physics motivated classes of "hilltop" and "hybrid-like" inflation models. In addition to these individual research directions, also the interplay between solutions to the three challenges will be explored. The results will be relevant for the design of future experiments and the clarification of their physics potential, and will lead to new candidate theories which can then be confronted with the combined data of running and future experiments. Matter Forces and the Universe Research Project | 5 Project MembersThe goal of the proposed research project is to contribute towards the development of a more fundamental theory of matter, forces and the universe, which resolves the open challenges of the Standard Model of elementary particles and the Concordance (LambdaCDM) Model of cosmology. The project will approach this goal from three directions in subproject, corresponding to the following three challenges: (A) origin of neutrino masses, (B) unification of forces and (C) early universe cosmology. Within the subprojects, new ideas for resolving the respective challenges will be developed, and existing ideas will be improved and explored. Based on these ideas, new theoretical models will be built and their predictions for observables at ongoing and future experiments will be derived. The necessary tools for accurate model analysis will be further developed. In addition, new connections between the three research directions (A), (B) and (C) will be explored. Ongoing and future experiments, such as collider experiments, precision neutrino experiments, flavour experiments and cosmological observations will provide new experimental results, which will allow test the validity of the developed theoretical candidate models. The results of the proposed research will contribute to selecting the right way forward towards a more fundamental theory of particle physics and cosmology. Matter, Forces and the Universe Research Project | 7 Project MembersWas ist die fundamentale Theorie der Materie, der Kräfte und des Universums? Diese Frage bildet die Motivation für die Forschung im Gebiet der theoretischen und experimentellen Elementarteilchenphysik und Kosmologie. Der aktuelle Wissensstand wird beschrieben durch das sogenannte "Standardmodell" der Elementarteilchen und das "Concordance Model" in der Kosmologie. Trotz der grossen Erfolge dieser Modelle bleiben viele Fragen unbeantwortet. Beispielsweise werden die beobachteten Neutrinomassen nicht durch das "Standardmodell" der Elementarteilchen beschrieben. In der Kosmologie sind viele offene Fragen mit der Frühphase der Entwicklung des Universums verknüpft. In dieser Frühphase werden die Grundvoraussetzungen für das heutige Universum gelegt, wie beispielsweise die Materie-Antimaterie Asymmetrie und die relative Flachheit des Universums. Eine Lösung der Herausforderungen in der Kosmologie erfordert eine Weiterentwicklung der Theorie der Elementarteilchen und der Kräfte zwischen ihnen. Ein Schwerpunkt des aktuellen Projekts ist es, teilchenphysikalische Theorien des Universums zu entwickeln und die Gültigkeit dieser Modelle mit den kosmologischen Beobachtungen zu überprüfen. Ausgangspunkt ist hierfür die Beschreibung der sogenannten inflationären Phase des Universums, in der es sich in einem winzigen Bruchteil einer Sekunde explosionsartig ausgedehnt hat. Diese explosionsartige Ausdehnung des Universums findet bei Energien statt, bei denen die drei Standardmodell-Kräfte zwischen den Elementarteilchen im Rahmen einer fundamentaleren "Vereinigten Theorie" beschrieben werden können. Es ist ein weiterer Schwerpunkt des Projekts, solche "Vereinigte Elementarteilchentheorien" weiterzuentwickeln, sodass sie mit den aktuellen experimentellen Daten in Einklang sind (einschliesslich der beobachteten Neutrinoeigenschaften) und zudem überprüfbare Vorhersagen für zukünftige Experimente machen. In den nächsten Jahren werden neue experimentelle Ergebnisse aus teilchenphysikalischen Experimenten und kosmologischen Beobachtungen dabei helfen, die richtigen Weiterentwicklungen der bestehenden Modelle zu selektieren. Basierend auf dem Zusammenspiel zwischen Theorie und Experiment ist das langfristige Ziel die Zusammenführung der Modelle der Elementarteilchenphysik und Kosmologie. Ziel des Projekts "Matter, Forces and the Universe" ist es, einen Beitrag zur Entwicklung einer solchen fundamentaleren Theorie der Elementarteilchen und Kosmologie zu leisten. Experimental and theoretical study of neutrino oscillations: exploring new physics beyond the Standard Model of Elementary Particles. Research Project | 1 Project MembersThe field of neutrino physics is very active in particle physics. Indeed, a number of observed phenomena in high-energy physics and cosmology lack their resolution within the Standard Model of particle physics (SM). These puzzles include the origin of neutrino masses, CP-violation in the leptonic sector, baryon asymmetry of the Universe, and the elementary particle composition of Dark Matter. It is therefore normal that the CHIPP Roadmap places neutrino physics as one of the three pillars of particle physics. With the support of this SINERGIA, we propose to strengthen and formalize the Swiss neutrino group (CH-NUS) composed of the theoretical group in EPFL and the three experimental groups in ETHZ, UniBe and UniGe involved in the T2K experiment, and sharing common interest for future common neutrino physics programmes. The main goal of this request is to enhance the visibility of Switzerland in neutrino physics in the worldwide scenario through a coherent and coordinated action among researchers in the assembly and the physics exploitation of the T2K experiment and in a common definition of the future direction of neutrino physics in Switzerland with a concerted plan from experimental and theoretical groups involved. 1 1 OverviewMembersPublicationsProjects & Collaborations
Projects & Collaborations 5 foundShow per page10 10 20 50 Effective field theory and open quantum system approach for dark matter dynamics in the early universe Research Project | 1 Project MembersOne of the major challenges in cosmology is to understandthe matter content of our universe. According to General Relativity (GR) there are deep connections between what fills the universe and its geometry, its dynamical expansion and eventually its fate. Notably, visible ordinary matter appears to be only a small fraction of the matter in our universe, whereas the bulk comes in the form of non-luminous and non-baryonic particles, dubbed dark matter (DM). Complementary measurements of large scale structures, galaxy formation, gravitational lensing and of the cosmic microwave background (CMB) strongly suggest that more than 80% of the matter in the universe consists of DM.The most accurate determination for ordinary matter and DM energy density are provided by anisotropies in the CMB and amount to $Omega_{hbox{scriptsize B}} h^2 = 0.02237 pm 0.00015$ and $Omega_{hbox{scriptsize DM}} h^2 = 0.1200 pm 0.0012$.On the contrary, there is almost a total lack of information concerning DM fromthe particle physics point of view. Over the last few decades, a Weakly Interacting Massive Particle (WIMP) has become the most studied candidate for DM. One of its key features is the production mechanism in the early universe via the so-called textit{freeze-out} of a thermal relic. For a DM particle of mass $M$, the freeze-out occurs at a temperature $T sim M/25$, i.e. the DM particles are textit{non-relativistic}. However, the freeze-out mechanism is not limited to WIMPs and even applies to cases where interactions are stronger.The key quantity that governs the evolution of the DM abundance is the thermally averaged annihilation cross section $langle sigma v rangle_{{rm{ann}}}$, encompassed in a Boltzmann equationbegin{equation}(partial_t + 3H) n = -langle sigma v rangle_{{rm{ann}}} (n^2-n^2_{{rm{eq}}}) , ,label{Boltzmann_1}end{equation} where $H$ is the Hubble rate and $n$ is the total number density of DM particles ($n_{{rm{eq}}}$ is that in equilibrium). The value of $langle sigma v rangle_{{rm{ann}}}$ depends on the model under consideration, namely its particle content and interactions. It is extremely important to calculate $langle sigma v rangle_{{rm{ann}}}$ accurately because the predicted present-day DM energy density depends crucially on it through the solution of eq.~(ref{Boltzmann_1}). The DM mass is in turn fixed as function of the other model parameters to reproduce $Omega_{hbox{scriptsize DM}} h^2$ in the first place (e.g.~couplings, mass splitting with other dark species). However, determining $langle sigma v rangle_{{rm{ann}}}$ by including the full features of each model and the thermal environment is not an easy task. In a variety of theories, DM interacts with gauge bosons or scalars that induce long-range interactions because of repeated soft exchanges. Remarkably, the inclusion of bound-state effects for DM annihilation has been recently shown to have a large impact on the textit{overclosure bound} for DM models, namely the largest value of the particle mass compatible with the observed DM energy density. At the same time, it is manifestly subtle and complicated to include bound-state dynamics in a thermal medium due to the intricate interplay between non-relativistic and thermal energy scales. The overall objective of the project is to develop and apply a novel approach for relic density computations in the framework of non-relativistic effective field theories (NREFTs) and open quantum systems (OQSs). Starting from a thermal field theoretic formulation of the problem, the interactions between the DM and the light plasma constituents will systematically be included: textit{bound-state formation and dissociation}, Sommerfeld effect, DM thermal masses and interaction rates, and the role of textit{phase transitions} during the freeze-out process. I will provide the DM annihilation cross sections and overclosure bounds for well-motivated classes of models: DM coannihilating with strongly interacting states (QCD-like), DM embedded in spontaneously broken Abelian and non-Abelian gauge gauge theories, composite DM. To this aim cutting-edge effective field theory (EFT) techniques at finite temperature will be used, in particular NREFTs and potential NREFTs (pNREFTs). Moreover, DM particles in medium will be recast in an open-quantum-system framework for the first time, with a focus on DM bound-state formation and their in-medium evolution. By adopting and exploiting such methods, the corresponding overclosure bounds on the DM mass will serve as comprehensive and solid benchmarks to interpret and guide experimental analyses for a wide class of DM models. In the contemporary endeavour of testing and possibly falsifying WIMP-like models with present and upcoming experiments, the outcomes of this project are timely and necessary in order to deliver the most reliable relic density constraints on the models parameters, especially on the DM mass. Matter, Forces and the Universe Research Project | 5 Project MembersThe aim of the research project is the development and precision testing of models beyond the Standard Models of particle physics and cosmology, towards a more fundamental theory of Matter, Forces and the Universe. To identify possible building blocks of a more fundamental theory, and to investigate how to probe them with the data of future experiments, my research project focuses on three challenges, associated with three subprojects. Subproject A: One of the great challenges of the present Standard Model (SM) of elementary particle physics is the origin of neutrino masses. In subproject A we plan to contribute towards resolving this open question by investigating systematically how the mechanism of neutrino mass generation can be probed best in future experiments, in particular at possible future electron-positron, proton-proton and electron-proton colliders such as the ILC, FCC-ee, CLIC, CEPC, HL-LHC, FCC-hh/SppC, LHeC and the FCC-eh. Subproject B: Towards the challenge of identifying a more fundamental theory framework behind the SM of elementary particles, subproject B will contribute to the development of (more) predictive Grand Unified Theory (GUT) models, exploring for instance new classes of models in SO(10), as well as to the development of tools for their precision analysis (focusing on GUT predictions for baryon number violating nucleon decays, sparticle masses and neutrino properties). Subproject C: When constructing models for the early universe, one of the great challenges is linking the phase of cosmic inflation to the later phase of the universe where, e.g., the matter-antimatter asymmetry and the dark matter are produced. In subproject C we will contribute to clarifying this link by calculating the intermediate "reheating phase", including the production of gravitational waves and non-perturbative phenomena like "oscillons", after particle physics motivated classes of "hilltop" and "hybrid-like" inflation models. In addition to these individual research directions, also the interplay between solutions to the three challenges will be explored. The results will be relevant for the design of future experiments and the clarification of their physics potential, and will lead to new candidate theories which can then be confronted with the combined data of running and future experiments. Matter Forces and the Universe Research Project | 5 Project MembersThe goal of the proposed research project is to contribute towards the development of a more fundamental theory of matter, forces and the universe, which resolves the open challenges of the Standard Model of elementary particles and the Concordance (LambdaCDM) Model of cosmology. The project will approach this goal from three directions in subproject, corresponding to the following three challenges: (A) origin of neutrino masses, (B) unification of forces and (C) early universe cosmology. Within the subprojects, new ideas for resolving the respective challenges will be developed, and existing ideas will be improved and explored. Based on these ideas, new theoretical models will be built and their predictions for observables at ongoing and future experiments will be derived. The necessary tools for accurate model analysis will be further developed. In addition, new connections between the three research directions (A), (B) and (C) will be explored. Ongoing and future experiments, such as collider experiments, precision neutrino experiments, flavour experiments and cosmological observations will provide new experimental results, which will allow test the validity of the developed theoretical candidate models. The results of the proposed research will contribute to selecting the right way forward towards a more fundamental theory of particle physics and cosmology. Matter, Forces and the Universe Research Project | 7 Project MembersWas ist die fundamentale Theorie der Materie, der Kräfte und des Universums? Diese Frage bildet die Motivation für die Forschung im Gebiet der theoretischen und experimentellen Elementarteilchenphysik und Kosmologie. Der aktuelle Wissensstand wird beschrieben durch das sogenannte "Standardmodell" der Elementarteilchen und das "Concordance Model" in der Kosmologie. Trotz der grossen Erfolge dieser Modelle bleiben viele Fragen unbeantwortet. Beispielsweise werden die beobachteten Neutrinomassen nicht durch das "Standardmodell" der Elementarteilchen beschrieben. In der Kosmologie sind viele offene Fragen mit der Frühphase der Entwicklung des Universums verknüpft. In dieser Frühphase werden die Grundvoraussetzungen für das heutige Universum gelegt, wie beispielsweise die Materie-Antimaterie Asymmetrie und die relative Flachheit des Universums. Eine Lösung der Herausforderungen in der Kosmologie erfordert eine Weiterentwicklung der Theorie der Elementarteilchen und der Kräfte zwischen ihnen. Ein Schwerpunkt des aktuellen Projekts ist es, teilchenphysikalische Theorien des Universums zu entwickeln und die Gültigkeit dieser Modelle mit den kosmologischen Beobachtungen zu überprüfen. Ausgangspunkt ist hierfür die Beschreibung der sogenannten inflationären Phase des Universums, in der es sich in einem winzigen Bruchteil einer Sekunde explosionsartig ausgedehnt hat. Diese explosionsartige Ausdehnung des Universums findet bei Energien statt, bei denen die drei Standardmodell-Kräfte zwischen den Elementarteilchen im Rahmen einer fundamentaleren "Vereinigten Theorie" beschrieben werden können. Es ist ein weiterer Schwerpunkt des Projekts, solche "Vereinigte Elementarteilchentheorien" weiterzuentwickeln, sodass sie mit den aktuellen experimentellen Daten in Einklang sind (einschliesslich der beobachteten Neutrinoeigenschaften) und zudem überprüfbare Vorhersagen für zukünftige Experimente machen. In den nächsten Jahren werden neue experimentelle Ergebnisse aus teilchenphysikalischen Experimenten und kosmologischen Beobachtungen dabei helfen, die richtigen Weiterentwicklungen der bestehenden Modelle zu selektieren. Basierend auf dem Zusammenspiel zwischen Theorie und Experiment ist das langfristige Ziel die Zusammenführung der Modelle der Elementarteilchenphysik und Kosmologie. Ziel des Projekts "Matter, Forces and the Universe" ist es, einen Beitrag zur Entwicklung einer solchen fundamentaleren Theorie der Elementarteilchen und Kosmologie zu leisten. Experimental and theoretical study of neutrino oscillations: exploring new physics beyond the Standard Model of Elementary Particles. Research Project | 1 Project MembersThe field of neutrino physics is very active in particle physics. Indeed, a number of observed phenomena in high-energy physics and cosmology lack their resolution within the Standard Model of particle physics (SM). These puzzles include the origin of neutrino masses, CP-violation in the leptonic sector, baryon asymmetry of the Universe, and the elementary particle composition of Dark Matter. It is therefore normal that the CHIPP Roadmap places neutrino physics as one of the three pillars of particle physics. With the support of this SINERGIA, we propose to strengthen and formalize the Swiss neutrino group (CH-NUS) composed of the theoretical group in EPFL and the three experimental groups in ETHZ, UniBe and UniGe involved in the T2K experiment, and sharing common interest for future common neutrino physics programmes. The main goal of this request is to enhance the visibility of Switzerland in neutrino physics in the worldwide scenario through a coherent and coordinated action among researchers in the assembly and the physics exploitation of the T2K experiment and in a common definition of the future direction of neutrino physics in Switzerland with a concerted plan from experimental and theoretical groups involved. 1 1
Effective field theory and open quantum system approach for dark matter dynamics in the early universe Research Project | 1 Project MembersOne of the major challenges in cosmology is to understandthe matter content of our universe. According to General Relativity (GR) there are deep connections between what fills the universe and its geometry, its dynamical expansion and eventually its fate. Notably, visible ordinary matter appears to be only a small fraction of the matter in our universe, whereas the bulk comes in the form of non-luminous and non-baryonic particles, dubbed dark matter (DM). Complementary measurements of large scale structures, galaxy formation, gravitational lensing and of the cosmic microwave background (CMB) strongly suggest that more than 80% of the matter in the universe consists of DM.The most accurate determination for ordinary matter and DM energy density are provided by anisotropies in the CMB and amount to $Omega_{hbox{scriptsize B}} h^2 = 0.02237 pm 0.00015$ and $Omega_{hbox{scriptsize DM}} h^2 = 0.1200 pm 0.0012$.On the contrary, there is almost a total lack of information concerning DM fromthe particle physics point of view. Over the last few decades, a Weakly Interacting Massive Particle (WIMP) has become the most studied candidate for DM. One of its key features is the production mechanism in the early universe via the so-called textit{freeze-out} of a thermal relic. For a DM particle of mass $M$, the freeze-out occurs at a temperature $T sim M/25$, i.e. the DM particles are textit{non-relativistic}. However, the freeze-out mechanism is not limited to WIMPs and even applies to cases where interactions are stronger.The key quantity that governs the evolution of the DM abundance is the thermally averaged annihilation cross section $langle sigma v rangle_{{rm{ann}}}$, encompassed in a Boltzmann equationbegin{equation}(partial_t + 3H) n = -langle sigma v rangle_{{rm{ann}}} (n^2-n^2_{{rm{eq}}}) , ,label{Boltzmann_1}end{equation} where $H$ is the Hubble rate and $n$ is the total number density of DM particles ($n_{{rm{eq}}}$ is that in equilibrium). The value of $langle sigma v rangle_{{rm{ann}}}$ depends on the model under consideration, namely its particle content and interactions. It is extremely important to calculate $langle sigma v rangle_{{rm{ann}}}$ accurately because the predicted present-day DM energy density depends crucially on it through the solution of eq.~(ref{Boltzmann_1}). The DM mass is in turn fixed as function of the other model parameters to reproduce $Omega_{hbox{scriptsize DM}} h^2$ in the first place (e.g.~couplings, mass splitting with other dark species). However, determining $langle sigma v rangle_{{rm{ann}}}$ by including the full features of each model and the thermal environment is not an easy task. In a variety of theories, DM interacts with gauge bosons or scalars that induce long-range interactions because of repeated soft exchanges. Remarkably, the inclusion of bound-state effects for DM annihilation has been recently shown to have a large impact on the textit{overclosure bound} for DM models, namely the largest value of the particle mass compatible with the observed DM energy density. At the same time, it is manifestly subtle and complicated to include bound-state dynamics in a thermal medium due to the intricate interplay between non-relativistic and thermal energy scales. The overall objective of the project is to develop and apply a novel approach for relic density computations in the framework of non-relativistic effective field theories (NREFTs) and open quantum systems (OQSs). Starting from a thermal field theoretic formulation of the problem, the interactions between the DM and the light plasma constituents will systematically be included: textit{bound-state formation and dissociation}, Sommerfeld effect, DM thermal masses and interaction rates, and the role of textit{phase transitions} during the freeze-out process. I will provide the DM annihilation cross sections and overclosure bounds for well-motivated classes of models: DM coannihilating with strongly interacting states (QCD-like), DM embedded in spontaneously broken Abelian and non-Abelian gauge gauge theories, composite DM. To this aim cutting-edge effective field theory (EFT) techniques at finite temperature will be used, in particular NREFTs and potential NREFTs (pNREFTs). Moreover, DM particles in medium will be recast in an open-quantum-system framework for the first time, with a focus on DM bound-state formation and their in-medium evolution. By adopting and exploiting such methods, the corresponding overclosure bounds on the DM mass will serve as comprehensive and solid benchmarks to interpret and guide experimental analyses for a wide class of DM models. In the contemporary endeavour of testing and possibly falsifying WIMP-like models with present and upcoming experiments, the outcomes of this project are timely and necessary in order to deliver the most reliable relic density constraints on the models parameters, especially on the DM mass.
Matter, Forces and the Universe Research Project | 5 Project MembersThe aim of the research project is the development and precision testing of models beyond the Standard Models of particle physics and cosmology, towards a more fundamental theory of Matter, Forces and the Universe. To identify possible building blocks of a more fundamental theory, and to investigate how to probe them with the data of future experiments, my research project focuses on three challenges, associated with three subprojects. Subproject A: One of the great challenges of the present Standard Model (SM) of elementary particle physics is the origin of neutrino masses. In subproject A we plan to contribute towards resolving this open question by investigating systematically how the mechanism of neutrino mass generation can be probed best in future experiments, in particular at possible future electron-positron, proton-proton and electron-proton colliders such as the ILC, FCC-ee, CLIC, CEPC, HL-LHC, FCC-hh/SppC, LHeC and the FCC-eh. Subproject B: Towards the challenge of identifying a more fundamental theory framework behind the SM of elementary particles, subproject B will contribute to the development of (more) predictive Grand Unified Theory (GUT) models, exploring for instance new classes of models in SO(10), as well as to the development of tools for their precision analysis (focusing on GUT predictions for baryon number violating nucleon decays, sparticle masses and neutrino properties). Subproject C: When constructing models for the early universe, one of the great challenges is linking the phase of cosmic inflation to the later phase of the universe where, e.g., the matter-antimatter asymmetry and the dark matter are produced. In subproject C we will contribute to clarifying this link by calculating the intermediate "reheating phase", including the production of gravitational waves and non-perturbative phenomena like "oscillons", after particle physics motivated classes of "hilltop" and "hybrid-like" inflation models. In addition to these individual research directions, also the interplay between solutions to the three challenges will be explored. The results will be relevant for the design of future experiments and the clarification of their physics potential, and will lead to new candidate theories which can then be confronted with the combined data of running and future experiments.
Matter Forces and the Universe Research Project | 5 Project MembersThe goal of the proposed research project is to contribute towards the development of a more fundamental theory of matter, forces and the universe, which resolves the open challenges of the Standard Model of elementary particles and the Concordance (LambdaCDM) Model of cosmology. The project will approach this goal from three directions in subproject, corresponding to the following three challenges: (A) origin of neutrino masses, (B) unification of forces and (C) early universe cosmology. Within the subprojects, new ideas for resolving the respective challenges will be developed, and existing ideas will be improved and explored. Based on these ideas, new theoretical models will be built and their predictions for observables at ongoing and future experiments will be derived. The necessary tools for accurate model analysis will be further developed. In addition, new connections between the three research directions (A), (B) and (C) will be explored. Ongoing and future experiments, such as collider experiments, precision neutrino experiments, flavour experiments and cosmological observations will provide new experimental results, which will allow test the validity of the developed theoretical candidate models. The results of the proposed research will contribute to selecting the right way forward towards a more fundamental theory of particle physics and cosmology.
Matter, Forces and the Universe Research Project | 7 Project MembersWas ist die fundamentale Theorie der Materie, der Kräfte und des Universums? Diese Frage bildet die Motivation für die Forschung im Gebiet der theoretischen und experimentellen Elementarteilchenphysik und Kosmologie. Der aktuelle Wissensstand wird beschrieben durch das sogenannte "Standardmodell" der Elementarteilchen und das "Concordance Model" in der Kosmologie. Trotz der grossen Erfolge dieser Modelle bleiben viele Fragen unbeantwortet. Beispielsweise werden die beobachteten Neutrinomassen nicht durch das "Standardmodell" der Elementarteilchen beschrieben. In der Kosmologie sind viele offene Fragen mit der Frühphase der Entwicklung des Universums verknüpft. In dieser Frühphase werden die Grundvoraussetzungen für das heutige Universum gelegt, wie beispielsweise die Materie-Antimaterie Asymmetrie und die relative Flachheit des Universums. Eine Lösung der Herausforderungen in der Kosmologie erfordert eine Weiterentwicklung der Theorie der Elementarteilchen und der Kräfte zwischen ihnen. Ein Schwerpunkt des aktuellen Projekts ist es, teilchenphysikalische Theorien des Universums zu entwickeln und die Gültigkeit dieser Modelle mit den kosmologischen Beobachtungen zu überprüfen. Ausgangspunkt ist hierfür die Beschreibung der sogenannten inflationären Phase des Universums, in der es sich in einem winzigen Bruchteil einer Sekunde explosionsartig ausgedehnt hat. Diese explosionsartige Ausdehnung des Universums findet bei Energien statt, bei denen die drei Standardmodell-Kräfte zwischen den Elementarteilchen im Rahmen einer fundamentaleren "Vereinigten Theorie" beschrieben werden können. Es ist ein weiterer Schwerpunkt des Projekts, solche "Vereinigte Elementarteilchentheorien" weiterzuentwickeln, sodass sie mit den aktuellen experimentellen Daten in Einklang sind (einschliesslich der beobachteten Neutrinoeigenschaften) und zudem überprüfbare Vorhersagen für zukünftige Experimente machen. In den nächsten Jahren werden neue experimentelle Ergebnisse aus teilchenphysikalischen Experimenten und kosmologischen Beobachtungen dabei helfen, die richtigen Weiterentwicklungen der bestehenden Modelle zu selektieren. Basierend auf dem Zusammenspiel zwischen Theorie und Experiment ist das langfristige Ziel die Zusammenführung der Modelle der Elementarteilchenphysik und Kosmologie. Ziel des Projekts "Matter, Forces and the Universe" ist es, einen Beitrag zur Entwicklung einer solchen fundamentaleren Theorie der Elementarteilchen und Kosmologie zu leisten.
Experimental and theoretical study of neutrino oscillations: exploring new physics beyond the Standard Model of Elementary Particles. Research Project | 1 Project MembersThe field of neutrino physics is very active in particle physics. Indeed, a number of observed phenomena in high-energy physics and cosmology lack their resolution within the Standard Model of particle physics (SM). These puzzles include the origin of neutrino masses, CP-violation in the leptonic sector, baryon asymmetry of the Universe, and the elementary particle composition of Dark Matter. It is therefore normal that the CHIPP Roadmap places neutrino physics as one of the three pillars of particle physics. With the support of this SINERGIA, we propose to strengthen and formalize the Swiss neutrino group (CH-NUS) composed of the theoretical group in EPFL and the three experimental groups in ETHZ, UniBe and UniGe involved in the T2K experiment, and sharing common interest for future common neutrino physics programmes. The main goal of this request is to enhance the visibility of Switzerland in neutrino physics in the worldwide scenario through a coherent and coordinated action among researchers in the assembly and the physics exploitation of the T2K experiment and in a common definition of the future direction of neutrino physics in Switzerland with a concerted plan from experimental and theoretical groups involved.
