Project acronym DISKtoHALO
Project From the accretion disk to the cluster halo: the multi-scale physics of black hole feedback
Researcher (PI) Christopher REYNOLDS
Host Institution (HI) THE CHANCELLOR MASTERS AND SCHOLARS OF THE UNIVERSITY OF CAMBRIDGE
Country United Kingdom
Call Details Advanced Grant (AdG), PE9, ERC-2018-ADG
Summary It is firmly established that supermassive black holes (SMBHs) have a profound influence on the evolution of galaxies and galaxy groups/clusters. Yet, almost 20 years after this realization, fundamental questions remain. What determines the efficiency with which an active galactic nucleus (AGN) couples to its surroundings? Why does AGN feedback appear to be ineffective in low-mass galaxies? In maintenance-mode feedback, how does the AGN regulate to closely balance cooling? How does the nature of AGN feedback change as we consider higher redshifts and push back to the epoch of the first galaxies? AGN feedback is a truly multi-scale phenomenon. Observations show that AGN have an energetic impact on galactic-, group-, and cluster-halo scales. Yet the efficiency with which an accreting SMBH releases energy, and the partitioning of that energy into radiation, winds, and relativistic jets, is dictated by complex processes in the accretion disk on AU scales, 10^10 times smaller than the halo. Furthermore, especially in massive systems where feedback proceeds via the heating of a hot circumgalactic or intracluster medium (CGM/ICM), the relevant microphysics of the hot baryons is unclear, requiring an understanding of plasma instabilities on 10^-9pc scales. We propose a set of projects that explore the multiscale physics of AGN feedback. Magnetohydrodynamic models of accretion disks will be constructed to study the AGN radiation/winds/jets and calibrate observable proxies of SMBH mass and accretion rate. We will use the machinery of plasma physics to characterize the CGM/ICM microphysics relevant to the thermalization of AGN-injected energy. Finally, we will produce new galaxy-, group- and cluster-scale models incorporating the new microphysical prescriptions and AGN models. Our new theoretical understanding of AGN feedback as a function of halo mass, environment, and cosmic time is essential for interpreting the torrent of data from current and future observatories
Summary
It is firmly established that supermassive black holes (SMBHs) have a profound influence on the evolution of galaxies and galaxy groups/clusters. Yet, almost 20 years after this realization, fundamental questions remain. What determines the efficiency with which an active galactic nucleus (AGN) couples to its surroundings? Why does AGN feedback appear to be ineffective in low-mass galaxies? In maintenance-mode feedback, how does the AGN regulate to closely balance cooling? How does the nature of AGN feedback change as we consider higher redshifts and push back to the epoch of the first galaxies? AGN feedback is a truly multi-scale phenomenon. Observations show that AGN have an energetic impact on galactic-, group-, and cluster-halo scales. Yet the efficiency with which an accreting SMBH releases energy, and the partitioning of that energy into radiation, winds, and relativistic jets, is dictated by complex processes in the accretion disk on AU scales, 10^10 times smaller than the halo. Furthermore, especially in massive systems where feedback proceeds via the heating of a hot circumgalactic or intracluster medium (CGM/ICM), the relevant microphysics of the hot baryons is unclear, requiring an understanding of plasma instabilities on 10^-9pc scales. We propose a set of projects that explore the multiscale physics of AGN feedback. Magnetohydrodynamic models of accretion disks will be constructed to study the AGN radiation/winds/jets and calibrate observable proxies of SMBH mass and accretion rate. We will use the machinery of plasma physics to characterize the CGM/ICM microphysics relevant to the thermalization of AGN-injected energy. Finally, we will produce new galaxy-, group- and cluster-scale models incorporating the new microphysical prescriptions and AGN models. Our new theoretical understanding of AGN feedback as a function of halo mass, environment, and cosmic time is essential for interpreting the torrent of data from current and future observatories
Max ERC Funding
2 489 918 €
Duration
Start date: 2019-10-01, End date: 2024-09-30
Project acronym GEMS
Project Genetically Evolving Models of Science
Researcher (PI) Fernand Gobet
Host Institution (HI) LONDON SCHOOL OF ECONOMICS AND POLITICAL SCIENCE
Country United Kingdom
Call Details Advanced Grant (AdG), SH4, ERC-2018-ADG
Summary The development of scientific models suffers from two related problems: ever-growing number of experimental results and scientists’ cognitive limitations (including cognitive biases). This multidisciplinary project (psychology, computer modelling, computer science and cognitive neuroscience) addresses these problems by developing a novel methodology for generating scientific models automatically. The methodology is general and can be applied to any science where experimental data are available.
The method treats models as computer programs and evolves a population of models using genetic programming. The extent to which the models fit the empirical data is used as a fitness function. The best models–potentially modified by cross-over and mutation–are selected for the next generation. Pilot simulations have established the validity of the methodology with simple experiments.
To demonstrate that the methodology is sound, can be used with complex datasets and can be generalised across sciences, four related strands of research are planned. First, ‘Building New Tools’ develops the methodology and creates techniques to understand and compare the evolved models. Second, ‘Explaining Human Data’ uses the methodology to explain a wide range of data on human cognition. This will be done in two steps: (a) data without learning (working memory and attention); and (b) data with learning (categorisation, implicit learning and explicit learning). Third, ‘Explaining Animal Data’ develops models to account for various aspects of animal behaviour, focusing on conditioning and categorisation. Finally, ‘Explaining Neuroscience Data’ extends the methodology to account for data combining information about cognitive and brain processes.
This project explores virgin territory and thus opens up a new field of research. It combines insights from experimental psychology, cognitive modelling, cognitive neuroscience and computer science, disciplines in which the PI has strong track record.
Summary
The development of scientific models suffers from two related problems: ever-growing number of experimental results and scientists’ cognitive limitations (including cognitive biases). This multidisciplinary project (psychology, computer modelling, computer science and cognitive neuroscience) addresses these problems by developing a novel methodology for generating scientific models automatically. The methodology is general and can be applied to any science where experimental data are available.
The method treats models as computer programs and evolves a population of models using genetic programming. The extent to which the models fit the empirical data is used as a fitness function. The best models–potentially modified by cross-over and mutation–are selected for the next generation. Pilot simulations have established the validity of the methodology with simple experiments.
To demonstrate that the methodology is sound, can be used with complex datasets and can be generalised across sciences, four related strands of research are planned. First, ‘Building New Tools’ develops the methodology and creates techniques to understand and compare the evolved models. Second, ‘Explaining Human Data’ uses the methodology to explain a wide range of data on human cognition. This will be done in two steps: (a) data without learning (working memory and attention); and (b) data with learning (categorisation, implicit learning and explicit learning). Third, ‘Explaining Animal Data’ develops models to account for various aspects of animal behaviour, focusing on conditioning and categorisation. Finally, ‘Explaining Neuroscience Data’ extends the methodology to account for data combining information about cognitive and brain processes.
This project explores virgin territory and thus opens up a new field of research. It combines insights from experimental psychology, cognitive modelling, cognitive neuroscience and computer science, disciplines in which the PI has strong track record.
Max ERC Funding
2 182 339 €
Duration
Start date: 2019-11-01, End date: 2024-10-31
Project acronym MiniEmbryoBlueprint
Project The mammalian body plan blueprint, an in vitro approach
Researcher (PI) Alfonso MARTINEZ ARIAS
Host Institution (HI) THE CHANCELLOR MASTERS AND SCHOLARS OF THE UNIVERSITY OF CAMBRIDGE
Country United Kingdom
Call Details Advanced Grant (AdG), LS3, ERC-2018-ADG
Summary The development of an embryo requires the spatially structured emergence of tissues and organs. This process relies on the early establishment of a coordinate system in the form of three orthogonal axes that act as a reference for laying down the body plan, a template for the organism. Genetic analysis of this process has revealed an underlying transcriptional blueprint that links the coordinate system and the body plan. However, the way in which the gene products contribute to the emergence of the body plan remains an open question. A reason for this is that this process involves feedbacks and integration between the activity of Gene Regulatory Networks (GRNs) and the mechanics of multicellular ensembles, and that probing this relationship is experimentally challenging. In the case of mammalian embryos, which are particularly important as models for human development, our gaps in knowledge of these events are larger than in other organisms. This is partly due to the challenges associated with uterine development but also, and increasingly, because of the cost of mice and the difficulty of obtaining large numbers of embryos, as required for mechanistic experiments. In this project we shall use gastruloids, a novel and versatile Pluripotent Stem Cells based experimental system that we have developed for the study of mammalian development, to gain insights into the molecular and cellular basis underlying the emergence of the mammalian body plan. Gastruloids lack anterior neural structures and over a period of five days become organized in the fashion of a midgestation mouse embryo. We shall use the experimental versatility of the Gastruloid system to probe into the functional relationships between the mechanical activities of multicellular ensembles and the dynamics of GRNs that underlie the emergence of the mammalian body plan.
Summary
The development of an embryo requires the spatially structured emergence of tissues and organs. This process relies on the early establishment of a coordinate system in the form of three orthogonal axes that act as a reference for laying down the body plan, a template for the organism. Genetic analysis of this process has revealed an underlying transcriptional blueprint that links the coordinate system and the body plan. However, the way in which the gene products contribute to the emergence of the body plan remains an open question. A reason for this is that this process involves feedbacks and integration between the activity of Gene Regulatory Networks (GRNs) and the mechanics of multicellular ensembles, and that probing this relationship is experimentally challenging. In the case of mammalian embryos, which are particularly important as models for human development, our gaps in knowledge of these events are larger than in other organisms. This is partly due to the challenges associated with uterine development but also, and increasingly, because of the cost of mice and the difficulty of obtaining large numbers of embryos, as required for mechanistic experiments. In this project we shall use gastruloids, a novel and versatile Pluripotent Stem Cells based experimental system that we have developed for the study of mammalian development, to gain insights into the molecular and cellular basis underlying the emergence of the mammalian body plan. Gastruloids lack anterior neural structures and over a period of five days become organized in the fashion of a midgestation mouse embryo. We shall use the experimental versatility of the Gastruloid system to probe into the functional relationships between the mechanical activities of multicellular ensembles and the dynamics of GRNs that underlie the emergence of the mammalian body plan.
Max ERC Funding
2 480 300 €
Duration
Start date: 2019-10-01, End date: 2024-09-30
Project acronym NOQIA
Project NOvel Quantum simulators – connectIng Areas
Researcher (PI) Maciej Lewenstein
Host Institution (HI) FUNDACIO INSTITUT DE CIENCIES FOTONIQUES
Country Spain
Call Details Advanced Grant (AdG), PE2, ERC-2018-ADG
Summary Quantum simulators (QS) are experimental systems that allow mimic hard to simulate models of condensed matter, high energy physics and beyond. QS have various platforms: from ultracold atoms and ions to superconducting qubits. They constitute the important pillar of quantum technologies (QT), and promise future applications in chemistry, material science and optimization problems. Over the last decade, QS were particularly successful in mimicking topological effects in physics (TEP) and in developing accurate quantum validation/certification (QVC) methods. NOQIA is a theory project, aimed at introducing the established field of QS+TEP+QVC into two novel areas: physics of ultrafast phenomena and attoscience (AS) on one side, and quantum machine learning (ML) and neural networks (NN) on the other. This will open up new horizons/opportunities for research both in AS and in ML/NN. For instance, in AS we will address the question if intense laser physics may serve as a tool to detect topological effects in solid state and strongly correlated systems. We will study response of matter to laser pulses carrying topological signatures, to determine if they can induce topological effects in targets. We will design/analyze QS using trapped atoms to understand and detect TEP in the AS. On the ML/NN side, we will apply classical ML to analyze, design and control QS for topological systems, in order to understand and optimize them. Conversely, we will transfer many-body techniques to ML in order to analyze and possibly improve performance of classical machine learning. We will design and analyze quantum neural network devices that will employ topology in order to achieve robust quantum memory or information processing. We will design/study attractor neural networks with topological stationary states, or feed-forward networks with topological Floquet and time-crystal states. Both in AS and ML/NN, NOQIA will rely on quantum validation and certification protocols and techniques.
Summary
Quantum simulators (QS) are experimental systems that allow mimic hard to simulate models of condensed matter, high energy physics and beyond. QS have various platforms: from ultracold atoms and ions to superconducting qubits. They constitute the important pillar of quantum technologies (QT), and promise future applications in chemistry, material science and optimization problems. Over the last decade, QS were particularly successful in mimicking topological effects in physics (TEP) and in developing accurate quantum validation/certification (QVC) methods. NOQIA is a theory project, aimed at introducing the established field of QS+TEP+QVC into two novel areas: physics of ultrafast phenomena and attoscience (AS) on one side, and quantum machine learning (ML) and neural networks (NN) on the other. This will open up new horizons/opportunities for research both in AS and in ML/NN. For instance, in AS we will address the question if intense laser physics may serve as a tool to detect topological effects in solid state and strongly correlated systems. We will study response of matter to laser pulses carrying topological signatures, to determine if they can induce topological effects in targets. We will design/analyze QS using trapped atoms to understand and detect TEP in the AS. On the ML/NN side, we will apply classical ML to analyze, design and control QS for topological systems, in order to understand and optimize them. Conversely, we will transfer many-body techniques to ML in order to analyze and possibly improve performance of classical machine learning. We will design and analyze quantum neural network devices that will employ topology in order to achieve robust quantum memory or information processing. We will design/study attractor neural networks with topological stationary states, or feed-forward networks with topological Floquet and time-crystal states. Both in AS and ML/NN, NOQIA will rely on quantum validation and certification protocols and techniques.
Max ERC Funding
2 164 244 €
Duration
Start date: 2019-07-01, End date: 2024-06-30
Project acronym PLASTINET
Project Plasticity of the Pluripotency Network
Researcher (PI) Austin SMITH
Host Institution (HI) THE UNIVERSITY OF EXETER
Country United Kingdom
Call Details Advanced Grant (AdG), LS3, ERC-2018-ADG
Summary A few days after fertilisation mammalian embryos form a blastocyst comprised of three tissues; trophoblast and hypoblast are the forebears of extraembryonic structures, while naive epiblast cell are the pluripotent source of the embryo proper. Classical mouse embryological studies indicate that lineage potencies are determined concomitant with segregation of the three founder tissues. Textbook definitions of pluripotency thus exclude extraembryonic potential. Consistent with this paradigm, mouse embryonic stem cells are generally ineffective in producing trophoblast or hypoblast derivatives. However, we have discovered that human naïve pluripotent cells have high intrinsic competence for trophoblast formation. Furthermore, unlike in mouse, extraembryonic transcription factors are present in human epiblast in vivo. These findings challenge the dogma of early lineage restriction but may be compatible with the ancestral origin of pluripotency. We hypothesise that extraembryonic plasticity underlaid by entwined regulatory networks is the evolutionary template of pluripotency. Consequently, signal modulation to suppress extraembryonic specification may be crucial for capture of stem cells representative of naïve epiblast in most mammals. We will examine human and non-human primates, farm animals in which embryos undergo extended development before implantation, and a marsupial in which pluripotent cells are generated from the trophoblast. In a cross-disciplinary approach we will employ transcriptomics, embryo and stem cell experimentation, and formal computational modelling to uncover the core biological program moulded by evolution into different forms. We aim to establish hitherto elusive chimaera-competent embryonic stem cells from species of importance for research, biomedical applications and livestock improvement. We will obtain fresh insight into the molecular logic governing early development, lineage plasticity, pluripotent identity, and stem cell self-renewal.
Summary
A few days after fertilisation mammalian embryos form a blastocyst comprised of three tissues; trophoblast and hypoblast are the forebears of extraembryonic structures, while naive epiblast cell are the pluripotent source of the embryo proper. Classical mouse embryological studies indicate that lineage potencies are determined concomitant with segregation of the three founder tissues. Textbook definitions of pluripotency thus exclude extraembryonic potential. Consistent with this paradigm, mouse embryonic stem cells are generally ineffective in producing trophoblast or hypoblast derivatives. However, we have discovered that human naïve pluripotent cells have high intrinsic competence for trophoblast formation. Furthermore, unlike in mouse, extraembryonic transcription factors are present in human epiblast in vivo. These findings challenge the dogma of early lineage restriction but may be compatible with the ancestral origin of pluripotency. We hypothesise that extraembryonic plasticity underlaid by entwined regulatory networks is the evolutionary template of pluripotency. Consequently, signal modulation to suppress extraembryonic specification may be crucial for capture of stem cells representative of naïve epiblast in most mammals. We will examine human and non-human primates, farm animals in which embryos undergo extended development before implantation, and a marsupial in which pluripotent cells are generated from the trophoblast. In a cross-disciplinary approach we will employ transcriptomics, embryo and stem cell experimentation, and formal computational modelling to uncover the core biological program moulded by evolution into different forms. We aim to establish hitherto elusive chimaera-competent embryonic stem cells from species of importance for research, biomedical applications and livestock improvement. We will obtain fresh insight into the molecular logic governing early development, lineage plasticity, pluripotent identity, and stem cell self-renewal.
Max ERC Funding
2 499 970 €
Duration
Start date: 2020-01-01, End date: 2024-12-31
Project acronym Somnostat
Project The Homeostatic Regulation and Biological Function of Sleep
Researcher (PI) Gero Andreas MIESENBoeCK
Host Institution (HI) THE CHANCELLOR, MASTERS AND SCHOLARS OF THE UNIVERSITY OF OXFORD
Country United Kingdom
Call Details Advanced Grant (AdG), LS5, ERC-2018-ADG
Summary Sleep is vital and universal, but its biological function remains unknown. This project will seek to understand why we need to sleep by studying how the brain responds to sleep loss. My previous work in Drosophila showed that rising sleep pressure activates two dozen sleep-inducing neurons in the dorsal fan-shaped body (dFB) of the central complex. Sleep need is encoded in the electrical excitability of these neurons, which fluctuates because two potassium conductances, voltage-gated Shaker and the leak channel Sandman, are modulated antagonistically. As a consequence, dFB neurons are electrically silent during waking and persistently active during sleep. The key open question addressed in this project is the nature of the molecular changes that drive dFB neurons into the electrically active state. My preliminary data point to two dFB-intrinsic transducers of sleep pressure. First, the Shaker β subunit Hyperkinetic responds via a bound nicotinamide cofactor to oxidative by-products of mitochondrial electron transport, revealing a potential connection between energy metabolism, oxidative stress, and sleep, three processes implicated independently in lifespan, aging, and disease. To strengthen this connection, we will monitor sleep and the biophysics of dFB neurons after perturbing mitochondrial respiration or cellular redox chemistry and vice versa. Second, Rho GTPases relay currently unknown signals to the machinery responsible for the regulated endocytosis of Sandman, whose extraction from the plasma membrane is a prerequisite for switching the sleep-promoting activity of dFB neurons on. To identify these signals, we will investigate cell-autonomous, synaptic, and non-synaptic mechanisms of GTPase control. Because clear parallels exist between dFB neurons and sleep-active neurons in the mammalian hypothalamus, mechanistic insights that can currently be gained only in Drosophila are expected to have broad validity for understanding sleep and its disruptions.
Summary
Sleep is vital and universal, but its biological function remains unknown. This project will seek to understand why we need to sleep by studying how the brain responds to sleep loss. My previous work in Drosophila showed that rising sleep pressure activates two dozen sleep-inducing neurons in the dorsal fan-shaped body (dFB) of the central complex. Sleep need is encoded in the electrical excitability of these neurons, which fluctuates because two potassium conductances, voltage-gated Shaker and the leak channel Sandman, are modulated antagonistically. As a consequence, dFB neurons are electrically silent during waking and persistently active during sleep. The key open question addressed in this project is the nature of the molecular changes that drive dFB neurons into the electrically active state. My preliminary data point to two dFB-intrinsic transducers of sleep pressure. First, the Shaker β subunit Hyperkinetic responds via a bound nicotinamide cofactor to oxidative by-products of mitochondrial electron transport, revealing a potential connection between energy metabolism, oxidative stress, and sleep, three processes implicated independently in lifespan, aging, and disease. To strengthen this connection, we will monitor sleep and the biophysics of dFB neurons after perturbing mitochondrial respiration or cellular redox chemistry and vice versa. Second, Rho GTPases relay currently unknown signals to the machinery responsible for the regulated endocytosis of Sandman, whose extraction from the plasma membrane is a prerequisite for switching the sleep-promoting activity of dFB neurons on. To identify these signals, we will investigate cell-autonomous, synaptic, and non-synaptic mechanisms of GTPase control. Because clear parallels exist between dFB neurons and sleep-active neurons in the mammalian hypothalamus, mechanistic insights that can currently be gained only in Drosophila are expected to have broad validity for understanding sleep and its disruptions.
Max ERC Funding
2 374 999 €
Duration
Start date: 2019-10-01, End date: 2024-09-30
Project acronym SPRINT
Project Speech Prosody in Interaction: The form and function of intonation in human communication
Researcher (PI) Amalia ARVANITI
Host Institution (HI) UNIVERSITY OF KENT
Country United Kingdom
Call Details Advanced Grant (AdG), SH4, ERC-2018-ADG
Summary Intonation, the modulation of voice pitch, is essential for communication as it conveys information that helps listeners make inferences about the pragmatic intent of the speaker. Despite increased understanding of intonation’s importance, there is little agreement even about essential aspects of its structure and meaning. This is in large part because research has focused either on the form of intonation, often taking a reductive approach to meaning, or has concentrated on meaning but without full scrutiny of form. Crucially, most research has eschewed the study of intonational variability, seeing it as a problem, rather than a natural facet of speech production that needs to be understood and accounted for. Examining all three aspects in tandem is critical for understanding how intonation is structured and functions in communication: considering meaning in the study of intonational form (i.e. phonetics and phonology) can help delimit intonational categories and uncover the limits of within-category variability; in turn, a robust understanding of form will lead to insights into intonational pragmatics. The present proposal will take exactly this integrative approach, based on the PI’s recent research, to examine intonational phenomena attested in English and Greek that have vexed researchers for some time (uptalk, high accents, question tunes). Two varieties per language will be studied, Standard Southern British, Bristol English, Standard Athenian, and Corfiot Greek. Their systematic differences with respect to the phenomena under investigation will allow me to examine cross-linguistic differences, and dialectal variation and its role in communication. The investigation will involve phonetic and pragmatic analysis and modelling, followed by series of behavioural and neurophysiological experiments. Together, these methods will shed light onto the realization, structure and function of intonation, and lead to a robust model of intonational phonology and pragmatics.
Summary
Intonation, the modulation of voice pitch, is essential for communication as it conveys information that helps listeners make inferences about the pragmatic intent of the speaker. Despite increased understanding of intonation’s importance, there is little agreement even about essential aspects of its structure and meaning. This is in large part because research has focused either on the form of intonation, often taking a reductive approach to meaning, or has concentrated on meaning but without full scrutiny of form. Crucially, most research has eschewed the study of intonational variability, seeing it as a problem, rather than a natural facet of speech production that needs to be understood and accounted for. Examining all three aspects in tandem is critical for understanding how intonation is structured and functions in communication: considering meaning in the study of intonational form (i.e. phonetics and phonology) can help delimit intonational categories and uncover the limits of within-category variability; in turn, a robust understanding of form will lead to insights into intonational pragmatics. The present proposal will take exactly this integrative approach, based on the PI’s recent research, to examine intonational phenomena attested in English and Greek that have vexed researchers for some time (uptalk, high accents, question tunes). Two varieties per language will be studied, Standard Southern British, Bristol English, Standard Athenian, and Corfiot Greek. Their systematic differences with respect to the phenomena under investigation will allow me to examine cross-linguistic differences, and dialectal variation and its role in communication. The investigation will involve phonetic and pragmatic analysis and modelling, followed by series of behavioural and neurophysiological experiments. Together, these methods will shed light onto the realization, structure and function of intonation, and lead to a robust model of intonational phonology and pragmatics.
Max ERC Funding
2 481 196 €
Duration
Start date: 2019-10-01, End date: 2024-09-30
Project acronym YoctoLHC
Project Yoctosecond imaging of QCD collectivity using jet observables
Researcher (PI) Carlos SALGADO
Host Institution (HI) UNIVERSIDAD DE SANTIAGO DE COMPOSTELA
Country Spain
Call Details Advanced Grant (AdG), PE2, ERC-2018-ADG
Summary QCD is the only sector of the Standard Model where the exploration of the first levels of complexity, built from fundamental interactions at the quantum level, is experimentally feasible. An outstanding example is the thermalised state of QCD matter formed when heavy atomic nuclei are smashed in particle colliders. Systematic experimental studies, carried out in the last two decades, overwhelmingly support the picture of a deconfined state of matter, which behaves as a nearly perfect fluid, formed in a very short time, less than 5 yoctoseconds. The mechanism that so efficiently brings the initial out-of-equilibrium state into a thermalised system is, however, largely unknown. Most surprisingly, LHC experiments have found that collisions of small systems, i.e. proton-proton or proton-lead, seem to indicate the presence of a tiny drop of this fluid in events with a large number of produced particles. These systems have sizes of 1 fm or less, or time-scales of less than 3 ys. To add to the puzzle, jet quenching, the modifications of jet properties due to interactions with the medium, has not been observed in these small systems, while jet quenching and thermalisation are expected to be controlled by the same dynamics. Present experimental tools have limited sensitivity to the actual process of thermalisation. To solve these long-standing questions we propose, as a completely novel strategy, using jet observables to directly access the first yoctoseconds of the collision. This strategy needs developments well beyond the state-of-the-art in three subjects: i) novel theoretical descriptions of the initial stages of the collision — the first 5 ys; ii) jet quenching theory for yoctosecond precision, with new techniques to couple the jet to the surrounding matter and novel parton shower evolution; and iii) jet quenching tools for the 2020’s, where completely novel jet observables will be devised with a focus on determining the initial stages of the collision.
Summary
QCD is the only sector of the Standard Model where the exploration of the first levels of complexity, built from fundamental interactions at the quantum level, is experimentally feasible. An outstanding example is the thermalised state of QCD matter formed when heavy atomic nuclei are smashed in particle colliders. Systematic experimental studies, carried out in the last two decades, overwhelmingly support the picture of a deconfined state of matter, which behaves as a nearly perfect fluid, formed in a very short time, less than 5 yoctoseconds. The mechanism that so efficiently brings the initial out-of-equilibrium state into a thermalised system is, however, largely unknown. Most surprisingly, LHC experiments have found that collisions of small systems, i.e. proton-proton or proton-lead, seem to indicate the presence of a tiny drop of this fluid in events with a large number of produced particles. These systems have sizes of 1 fm or less, or time-scales of less than 3 ys. To add to the puzzle, jet quenching, the modifications of jet properties due to interactions with the medium, has not been observed in these small systems, while jet quenching and thermalisation are expected to be controlled by the same dynamics. Present experimental tools have limited sensitivity to the actual process of thermalisation. To solve these long-standing questions we propose, as a completely novel strategy, using jet observables to directly access the first yoctoseconds of the collision. This strategy needs developments well beyond the state-of-the-art in three subjects: i) novel theoretical descriptions of the initial stages of the collision — the first 5 ys; ii) jet quenching theory for yoctosecond precision, with new techniques to couple the jet to the surrounding matter and novel parton shower evolution; and iii) jet quenching tools for the 2020’s, where completely novel jet observables will be devised with a focus on determining the initial stages of the collision.
Max ERC Funding
2 497 750 €
Duration
Start date: 2019-10-01, End date: 2024-09-30