Final Report Summary - MASSTEV (Mass hierarchy and particle physics at the TeV scale)
The research goal of the project was the investigation of the most fundamental aspects of particle physics models and gravity at high energies, and establishing the connection between these findings and experiments. The main fundamental questions addressed were at the very frontier of knowledge of theoretical particle physics and phenomenology and their intersection with gravity and string theory. The research team was formed by participants of two institutes: CERN and Ecole Polytechnique (EP). Besides the PI, there were two key senior members at CERN (Gia Dvali and Christophe Grojean), and one at EP (Emilian Dudas).
Our project focus on four research objectives: 1. Various approaches to the hierarchy problem ie the question of the stability of the electroweak scale after quantum corrections, 2. Parametrizing the effects of new physics, 3. String phenomenology, 4. Modifications of gravity at short and long distances and their phenomenological implications. In particular, eleven milestones were identified: 1. Uncovering the Higgs particle, 2. Analysis of collider signatures, 3. Spin determination, 4. Flavor structure, 5. Dark matter, 6. High temperature expansion, 7. Supersymmetry breaking, 8. String phenomenology, 9. String cosmology, 10. Confrontation with astrophysical and cosmological data, 11. Microgravity experiments.
One important result obtained by our team concerns the behavior of gravity in the presence of many particles that collectively strengthen the dynamics of gravitational interactions and thus result in the emergence of strong gravitational effects at the LHC. Naturally our researches also concern string cosmology where one of the most acute open problems concerns the initial phase of the universe and, in particular, the resolution of the initial Big-Bang singularity. The hope is that, by taking correctly the effects of quantum gravity into account, the unphysical singularities will be resolved in the framework of the underlying theory. We have also made progress in string model building with particular emphasis in reconciling unification of gauge forces with a braneworld picture of our universe.
We have also reconsidered the reductionism dogma at work since Rutherford that commonly accepts that arbitrarily short distances can be physically probed at higher and higher energies. On the contrary a novel setup proposed by our team suggests that certain quantum theories could incorporate the concept of minimal length, which prevents probing shorter distances. In such theories, an attempt to perform a measurement at shorter scale results into formation of a classical object that grows with the increasing energy of the probe. As a result, attempt to probe short scales in reality bounces back to longer distances.
Our team also contributes to establishing the Higgs boson discovery in July 2012. In particular, we provided an effective field theory description to analyze the possible deviations of the Higgs couplings and to fit the experimental data. These works had a large impact and influenced the way the Higgs data are reported by the experimental collaborations. We have also identified some phenomenological signatures that will help deciphering the true nature of the Higgs boson. We have also explained how to reconcile the measured value of the Higgs boson mass with a symmetry between boson and fermions thanks to the addition of new interactions beyond the minimal structure.
The ERC team during the whole period of the grant has produced 217 publications, 28 of which involved collaborations of senior members with researchers employed by the grant. The impact of the results of our research team is manifest also on the number of international conferences, schools and workshops where team members were invited (291 such events).
Obviously, this project was strongly correlated with LHC physics confronting theoretical predictions with observations and using experimental data for building new theories and correcting existing models. In such an intense dynamical process, participation of doctoral students and postdoctoral researchers was absolutely crucial and their active involvement was an essential component of the project. In total, we hired 10 students (at CERN) for a total of 184 person-months, about 10% more than what was expected in Annex I of the Grant agreement. Out of the 10 students, all of them have defended their PhD or are about to do it and 6 have obtained competitive postdoc positions in renowned institutions (UC Davis, Université libre de Bruxelles, Munich University, SISSA, University Autonoma de Barcelona, Weizmann Institute). Moreover, we hired 12 postdocs (2 at CERN and 10 at Ecole Polytechnique) for a total of 168 person-months, exactly as expected from Annex I of the Grant agreement (with a slightly different distribution between the two institutes). Two of these postdocs have obtained a permanent position with CNRS in France, another one has a tenured track position in Sao Paulo in Brazil and the other ones have found a subsequent postdoc position in another institute.
Our project focus on four research objectives: 1. Various approaches to the hierarchy problem ie the question of the stability of the electroweak scale after quantum corrections, 2. Parametrizing the effects of new physics, 3. String phenomenology, 4. Modifications of gravity at short and long distances and their phenomenological implications. In particular, eleven milestones were identified: 1. Uncovering the Higgs particle, 2. Analysis of collider signatures, 3. Spin determination, 4. Flavor structure, 5. Dark matter, 6. High temperature expansion, 7. Supersymmetry breaking, 8. String phenomenology, 9. String cosmology, 10. Confrontation with astrophysical and cosmological data, 11. Microgravity experiments.
One important result obtained by our team concerns the behavior of gravity in the presence of many particles that collectively strengthen the dynamics of gravitational interactions and thus result in the emergence of strong gravitational effects at the LHC. Naturally our researches also concern string cosmology where one of the most acute open problems concerns the initial phase of the universe and, in particular, the resolution of the initial Big-Bang singularity. The hope is that, by taking correctly the effects of quantum gravity into account, the unphysical singularities will be resolved in the framework of the underlying theory. We have also made progress in string model building with particular emphasis in reconciling unification of gauge forces with a braneworld picture of our universe.
We have also reconsidered the reductionism dogma at work since Rutherford that commonly accepts that arbitrarily short distances can be physically probed at higher and higher energies. On the contrary a novel setup proposed by our team suggests that certain quantum theories could incorporate the concept of minimal length, which prevents probing shorter distances. In such theories, an attempt to perform a measurement at shorter scale results into formation of a classical object that grows with the increasing energy of the probe. As a result, attempt to probe short scales in reality bounces back to longer distances.
Our team also contributes to establishing the Higgs boson discovery in July 2012. In particular, we provided an effective field theory description to analyze the possible deviations of the Higgs couplings and to fit the experimental data. These works had a large impact and influenced the way the Higgs data are reported by the experimental collaborations. We have also identified some phenomenological signatures that will help deciphering the true nature of the Higgs boson. We have also explained how to reconcile the measured value of the Higgs boson mass with a symmetry between boson and fermions thanks to the addition of new interactions beyond the minimal structure.
The ERC team during the whole period of the grant has produced 217 publications, 28 of which involved collaborations of senior members with researchers employed by the grant. The impact of the results of our research team is manifest also on the number of international conferences, schools and workshops where team members were invited (291 such events).
Obviously, this project was strongly correlated with LHC physics confronting theoretical predictions with observations and using experimental data for building new theories and correcting existing models. In such an intense dynamical process, participation of doctoral students and postdoctoral researchers was absolutely crucial and their active involvement was an essential component of the project. In total, we hired 10 students (at CERN) for a total of 184 person-months, about 10% more than what was expected in Annex I of the Grant agreement. Out of the 10 students, all of them have defended their PhD or are about to do it and 6 have obtained competitive postdoc positions in renowned institutions (UC Davis, Université libre de Bruxelles, Munich University, SISSA, University Autonoma de Barcelona, Weizmann Institute). Moreover, we hired 12 postdocs (2 at CERN and 10 at Ecole Polytechnique) for a total of 168 person-months, exactly as expected from Annex I of the Grant agreement (with a slightly different distribution between the two institutes). Two of these postdocs have obtained a permanent position with CNRS in France, another one has a tenured track position in Sao Paulo in Brazil and the other ones have found a subsequent postdoc position in another institute.