Project acronym collectiveQCD
Project Collectivity in small, srongly interacting systems
Researcher (PI) Korinna ZAPP
Host Institution (HI) LUNDS UNIVERSITET
Call Details Starting Grant (StG), PE2, ERC-2018-STG
Summary In collisions of heavy nuclei at collider energies, for instance at the Large Hadron Collider (LHC) at CERN, the energy density is so high that an equilibrated Quark-Gluon Plasma (QGP), an exotic state of matter consisting of deconfined quarks and gluons, is formed. In proton-proton (p+p) collisions, on the other hand, the density of produced particles is low. The traditional view on such reactions is that final state particles are free and do not rescatter. This picture is challenged by recent LHC data, which found features in p+p collisions that are indicative of collective behaviour and/or the formation of a hot and dense system. These findings have been taken as signs of QGP formation in p+p reactions. Such an interpretation is complicated by the fact that jets, which are the manifestation of very energetic quarks and gluons, are quenched in heavy ion collisions, but appear to be unmodified in p+p reactions. This is puzzling because collectivity and jet quenching are caused by the same processes. So far there is no consensus about the interpretation of these results, which is also due to a lack of suitable tools.
It is the objective of this proposal to address the question whether there are collective effects in p+p collisions. To this end two models capable of describing all relevant aspects of p+p and heavy ion collisions will be developed. They will be obtained by extending a successful description of p+p to heavy ion reactions and vice versa.
The answer to these questions will either clarify the long-standing problem how collectivity emerges from fundamental interactions, or it will necessitate qualitative changes to our interpretation of collective phenomena in p+p and/or heavy ion collisions.
The PI is in a unique position to accomplish this goal, as she has spent her entire career working on different aspects of p+p and heavy ion collisions. The group in Lund is the ideal host, as it is very active in developing alternative interpretations of the data.
Summary
In collisions of heavy nuclei at collider energies, for instance at the Large Hadron Collider (LHC) at CERN, the energy density is so high that an equilibrated Quark-Gluon Plasma (QGP), an exotic state of matter consisting of deconfined quarks and gluons, is formed. In proton-proton (p+p) collisions, on the other hand, the density of produced particles is low. The traditional view on such reactions is that final state particles are free and do not rescatter. This picture is challenged by recent LHC data, which found features in p+p collisions that are indicative of collective behaviour and/or the formation of a hot and dense system. These findings have been taken as signs of QGP formation in p+p reactions. Such an interpretation is complicated by the fact that jets, which are the manifestation of very energetic quarks and gluons, are quenched in heavy ion collisions, but appear to be unmodified in p+p reactions. This is puzzling because collectivity and jet quenching are caused by the same processes. So far there is no consensus about the interpretation of these results, which is also due to a lack of suitable tools.
It is the objective of this proposal to address the question whether there are collective effects in p+p collisions. To this end two models capable of describing all relevant aspects of p+p and heavy ion collisions will be developed. They will be obtained by extending a successful description of p+p to heavy ion reactions and vice versa.
The answer to these questions will either clarify the long-standing problem how collectivity emerges from fundamental interactions, or it will necessitate qualitative changes to our interpretation of collective phenomena in p+p and/or heavy ion collisions.
The PI is in a unique position to accomplish this goal, as she has spent her entire career working on different aspects of p+p and heavy ion collisions. The group in Lund is the ideal host, as it is very active in developing alternative interpretations of the data.
Max ERC Funding
1 500 000 €
Duration
Start date: 2019-02-01, End date: 2024-01-31
Project acronym UNISCAMP
Project The unity of scattering amplitudes: gauge theory, gravity, strings and number theory
Researcher (PI) Oliver Schlotterer
Host Institution (HI) UPPSALA UNIVERSITET
Call Details Starting Grant (StG), PE2, ERC-2018-STG
Summary Scattering amplitudes are central observables in quantum field theory and provide essential information about the quantum consistency of perturbative gravity. Precise control of the physical and mathematical properties of scattering amplitudes holds the key to long-standing questions on fundamental interactions and the structure of space and time. As a concrete leap in this direction, UNISCAMP addresses predictions in gauge theories, gravity and effective theories through
- the efficient computation and compact representation of scattering amplitudes and,
- decoding their hidden structures & symmetries and their rich web of connections.
String-theory methods will complement conventional approaches to scattering amplitudes, and I will combine the insights from
- the point-particle limit of superstrings & heterotic strings and,
- the recent ambitwistor strings which directly compute field-theory amplitudes.
Both of them naturally incorporate the double-copy relation between gauge-theory & gravity amplitudes and extend the framework to effective field theories describing pions and other low-energy states. It is a primary goal of UNISCAMP to pinpoint the unifying principles connecting a wide range of field and string theories. My expertise in both flavours of string theories will allow to optimally exploit their fruitful synergies and to depart from mainstream approaches.
Moreover, field- and string-theory amplitudes exhibit an intriguing mathematical structure: Their Feynman- and moduli-space integrals yield special functions such as polylogarithms which became a vibrant common theme of high-energy physics and number theory. As an interdisciplinary goal of UNISCAMP, I will
- investigate the low-energy expansion of multiloop string amplitudes and,
- extract an organizing scheme for iterated integrals on higher-genus Riemann surfaces.
These research objectives should benefit from my experience in collaborations with mathematicians.
Summary
Scattering amplitudes are central observables in quantum field theory and provide essential information about the quantum consistency of perturbative gravity. Precise control of the physical and mathematical properties of scattering amplitudes holds the key to long-standing questions on fundamental interactions and the structure of space and time. As a concrete leap in this direction, UNISCAMP addresses predictions in gauge theories, gravity and effective theories through
- the efficient computation and compact representation of scattering amplitudes and,
- decoding their hidden structures & symmetries and their rich web of connections.
String-theory methods will complement conventional approaches to scattering amplitudes, and I will combine the insights from
- the point-particle limit of superstrings & heterotic strings and,
- the recent ambitwistor strings which directly compute field-theory amplitudes.
Both of them naturally incorporate the double-copy relation between gauge-theory & gravity amplitudes and extend the framework to effective field theories describing pions and other low-energy states. It is a primary goal of UNISCAMP to pinpoint the unifying principles connecting a wide range of field and string theories. My expertise in both flavours of string theories will allow to optimally exploit their fruitful synergies and to depart from mainstream approaches.
Moreover, field- and string-theory amplitudes exhibit an intriguing mathematical structure: Their Feynman- and moduli-space integrals yield special functions such as polylogarithms which became a vibrant common theme of high-energy physics and number theory. As an interdisciplinary goal of UNISCAMP, I will
- investigate the low-energy expansion of multiloop string amplitudes and,
- extract an organizing scheme for iterated integrals on higher-genus Riemann surfaces.
These research objectives should benefit from my experience in collaborations with mathematicians.
Max ERC Funding
1 425 000 €
Duration
Start date: 2019-01-01, End date: 2023-12-31
