Interference and Resonant Phenomena involving Antimatter
Lead Research Organisation:
University College London
Department Name: Physics and Astronomy
Abstract
Whilst the apparent imbalance between matter and antimatter in our universe remains a major puzzle in science, valuable insights into the basic interactions between the two have been gained by studying collisions of positrons and positronium with atoms and molecules. The proposed programme is focussed on advancing this knowledge.
Positrons are the antimatter counterpart to electrons with which they eventually annihilate releasing gamma-rays; positronium (Ps) is the atom-like bound state of a positron and an electron, analogous to hydrogen with the positron replacing the proton. In addition to their importance in the fundamental understanding of nature, studies of their interactions with matter allow us, for example, to investigate material properties and to obtain functional imaging of human organs as it is done in positron emission tomography (PET). Positronium formation is so probable that, for example, 80% of gamma-rays detected in PET and 95% of positron annihilations originating from the centre of the Milky Way are from Ps decays.
Lately, we discovered that positronium scatters in a manner similar to that of a bare electron at the same collision velocity (despite Ps being a neutral atom, twice the electron mass). This finding was entirely unexpected and it is guiding theory and experiment towards an accurate description of the interactions of this matter-antimatter hybrid with matter.
Two recent technical attainments are particularly pertinent to our future plans, namely the realization of a positronium beam now tuneable down to energies five times lower than previously obtained, and the development of a new high-resolution positron-beamline apt for inspecting collision dynamics.
These enhanced experimental capabilities have already started to bear fruit with first glimpses of subtle quantum mechanical effects, such as resonances and interference phenomena, previously beyond established observational power. We will probe the mechanisms giving rise to such effects in positron and positronium scattering and thus aid progress towards of a more profound understanding of matter-antimatter physics in general.
Positrons are the antimatter counterpart to electrons with which they eventually annihilate releasing gamma-rays; positronium (Ps) is the atom-like bound state of a positron and an electron, analogous to hydrogen with the positron replacing the proton. In addition to their importance in the fundamental understanding of nature, studies of their interactions with matter allow us, for example, to investigate material properties and to obtain functional imaging of human organs as it is done in positron emission tomography (PET). Positronium formation is so probable that, for example, 80% of gamma-rays detected in PET and 95% of positron annihilations originating from the centre of the Milky Way are from Ps decays.
Lately, we discovered that positronium scatters in a manner similar to that of a bare electron at the same collision velocity (despite Ps being a neutral atom, twice the electron mass). This finding was entirely unexpected and it is guiding theory and experiment towards an accurate description of the interactions of this matter-antimatter hybrid with matter.
Two recent technical attainments are particularly pertinent to our future plans, namely the realization of a positronium beam now tuneable down to energies five times lower than previously obtained, and the development of a new high-resolution positron-beamline apt for inspecting collision dynamics.
These enhanced experimental capabilities have already started to bear fruit with first glimpses of subtle quantum mechanical effects, such as resonances and interference phenomena, previously beyond established observational power. We will probe the mechanisms giving rise to such effects in positron and positronium scattering and thus aid progress towards of a more profound understanding of matter-antimatter physics in general.
Planned Impact
Positrons and positronium are fundamental to our understanding of the physical universe. They have also become useful in practical applications ranging from material science to engineering and outstandingly powerful in the biomedical industry.
In this respect, there is currently an international drive towards the development of accurate dosimetry for Positron Emission Tomography (PET) and data for positron/Ps interactions with molecules of biological significance are particularly sought after for simulations of positron tracks in biological media. The clear motivation is that an increased understanding will lead to reduced damage of healthy tissue and, potentially, to efficient targeting (e.g. of cancerous growths). We regularly receive requests to provide cross-section data and we will alert scientists working in this field to our new findings as they emerge.
We will disseminate our experimental results by publishing in high-profile journals and by delivering invited talks and seminars. Additionally, research data will be placed online at UCL Discovery where free access to publications will be available. We will engage with key scientists by pro-actively fostering dialogues through exchange visits and focussed workshops.
Additional benefits will arise for the public/industrial sector through the training of scientists in performing world-class science and in developing a variety of skills (e.g. problem-solving, creative, communication, etc), crucial in innovative endeavours in academia and industry. Mentoring and support for career development will be provided to staff involved in the project throughout its duration, also through the provisions of the UCL Doctoral Skills Development Programme. Recent members of the group have gone on to work at prestigious research labs (e.g. CERN, RIKEN, ETH), in the UK Industry (e.g. AWE, Health Protection Agency, BAE Systems Detica, Thermo Fisher Scientific) and in the financial sector.
Antimatter is a powerful vehicle for stimulating interest and promoting understanding in physics and science by the general public and especially by young people. In the framework of the departmental "Science for the Public" initiatives, we shall strive to generate broader awareness through publications of broader reach and on UCL websites (with the support and advice from the UCL Public Engagement Unit), by arranging school visits to our labs and delivering popular lectures/talks at schools or interested societies.
In this respect, there is currently an international drive towards the development of accurate dosimetry for Positron Emission Tomography (PET) and data for positron/Ps interactions with molecules of biological significance are particularly sought after for simulations of positron tracks in biological media. The clear motivation is that an increased understanding will lead to reduced damage of healthy tissue and, potentially, to efficient targeting (e.g. of cancerous growths). We regularly receive requests to provide cross-section data and we will alert scientists working in this field to our new findings as they emerge.
We will disseminate our experimental results by publishing in high-profile journals and by delivering invited talks and seminars. Additionally, research data will be placed online at UCL Discovery where free access to publications will be available. We will engage with key scientists by pro-actively fostering dialogues through exchange visits and focussed workshops.
Additional benefits will arise for the public/industrial sector through the training of scientists in performing world-class science and in developing a variety of skills (e.g. problem-solving, creative, communication, etc), crucial in innovative endeavours in academia and industry. Mentoring and support for career development will be provided to staff involved in the project throughout its duration, also through the provisions of the UCL Doctoral Skills Development Programme. Recent members of the group have gone on to work at prestigious research labs (e.g. CERN, RIKEN, ETH), in the UK Industry (e.g. AWE, Health Protection Agency, BAE Systems Detica, Thermo Fisher Scientific) and in the financial sector.
Antimatter is a powerful vehicle for stimulating interest and promoting understanding in physics and science by the general public and especially by young people. In the framework of the departmental "Science for the Public" initiatives, we shall strive to generate broader awareness through publications of broader reach and on UCL websites (with the support and advice from the UCL Public Engagement Unit), by arranging school visits to our labs and delivering popular lectures/talks at schools or interested societies.
People |
ORCID iD |
| Gaetana Laricchia (Principal Investigator) |
Publications
Fayer S
(2019)
Differential positronium-formation cross sections for Ne, Ar, Kr, and Xe
in Physical Review A
Kadokura R
(2019)
Angle-Resolved Electron Scattering from H_{2}O near 0°.
in Physical review letters
Laricchia G
(2018)
A statistical description of scattering at the quantum level.
in Scientific reports
Loreti A
(2016)
High-Resolution Measurements of e^{+}+H_{2}O Total Cross Section.
in Physical review letters
Newson D
(2023)
Statistical nature of secondary electron emission
in Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Newson D
(2023)
Low-energy positronium scattering from O 2
in Physical Review A
Newson D
(2022)
Detection of low-energy charged particles by channel electron multipliers
in Journal of Instrumentation
Newson DM
(2023)
Low-energy positronium scattering from O2
in Physical Review A
Schippers S
(2019)
Roadmap on photonic, electronic and atomic collision physics: II. Electron and antimatter interactions
in Journal of Physics B: Atomic, Molecular and Optical Physics
Shipman M
(2017)
Resonant scattering of positronium as a quasifree electron
in Physical Review A
| Description | (I) Using an electrostatic positron beam, the total cross section of positrons scattering from H2O has been measured for the first time with a high angular discrimination (similar or equal to 1 degrees) against forward scattered projectiles. Results have been obtained in the energy range (10-300) eV. Significant deviations from previous measurements are found which are, if ascribed entirely to the angular acceptances of various experimental systems, in quantitative accord with ab initio theoretical predictions of the differential elastic scattering cross section. (II) In order to clarify the physics underlying the observations of the electronlike behavior of positronium (Ps) and its resonant scattering from CO2, we have measured the Ps + N-2 total cross section and found it also to exhibit significant structure. Analysis of the resonances reveals that Ps is distorted in the collisions and classical trajectory Monte Carlo calculations indicate that the electron is on average closer to the target than the positron, which may in turn bind resonantly to the ensuing temporary negative ion. This description of the nature of Ps resonances agrees with long-standing theoretical predictions. (III) Quantum physics is undoubtedly the most successful theory of the microscopic world, yet the complexities which arise in applying it even to simple atomic and molecular systems render the description of basic collision probabilities a formidable task. For this reason, approximations are often employed, the validity of which may be restricted to given energy regimes and/or targets and/or projectiles. Now we have found that the lognormal function, widely used for the probability distribution of macroscopic stochastic events (as diverse as periods of incubation of and recovery from diseases, size of grains, abundance of species, fluctuations in economic quantities, etc.) may also be employed to describe the energy dependence of inelastic collisions at the quantum level (including ionization, electron capture and excitation by electrons, positrons, protons, antiprotons, etc.), by allowing for the relevant threshold energy. A physical interpretation is discussed in this article by analogy with the heat capacity of few-level systems in solid state physics. We find the generality of the analysis to extend also to nuclear reactions. As well as aiding the description of collision probabilities for quantum systems, this finding is expected to impact also on the fundamental understanding of the interface between the classical and quantum domains. (IV) An electron beam, characterized by a high-angular discrimination (?0.7°), has been used to measure the total (elastic plus inelastic) cross section of H2O in the energy range 3-100 eV. Broad coincidence is found with recent experiments, including a pronounced shoulder in the 6-12 eV region. However, at energies ? 6eV, the present cross sections are ?30% higher. Furthermore, forward scattering has been probed in the angular range 0°-3.5° and measures of the average (rotationally and vibrationally summed) differential elastic cross sections for incident energies =12eV are obtained at a scattering angle ?1°. The measurements, which provide the first test of theoretical predictions in an angular region experimentally unexplored until now, are found to be within 1 standard deviation of corresponding ab initio R-matrix calculations. (V) Experimental determinations of the absolute differential positronium-formation cross sections near 0? for Ne, Ar, Kr, and Xe have been obtained and compared with theory. The degree of forward collimation, expressed by the ratios of the differential-to-integral positronium-formation cross sections, is also computed and compared with theories and other targets. Trends among targets and structures at low energies emerge when considered as a function of the reduced total energy. |
| Exploitation Route | The main beneficiaries of the outcomes of our research will be primarily other scientists, especially theorists who will use our experimental data to test their hypotheses , modellers of astrophysical events, plasma diagnostics and radiobiological processes who input cross-section data in their computations. In this respect, there is currently an international drive towards the development of accurate dosimetry for Positron Emission Tomography (PET), data for molecules of biological significance being particularly sought after for simulations of positron tracks in biological media. The clear motivation is that an increased understanding will lead to reduced damage of healthy tissue and, potentially, to efficient targeting (e.g. of cancerous growths). We regularly receive requests to provide cross-section data and we will alert scientists working in this field to our new findings as they emerge. |
| Sectors | Chemicals,Environment,Healthcare |
| URL | http://www.ucl.ac.uk/positron-physics/title.html |
| Description | The main beneficiaries of the outcomes of our research will be primarily other scientists, especially theorists who will use our experimental data to test their hypotheses, modellers of astrophysical events, plasma diagnostics and radiobiological processes who input cross-section data in their computations. In this respect, there is currently an international drive towards the development of accurate dosimetry for Positron Emission Tomography (PET), data for molecules of biological significance being particularly sought after for simulations of positron tracks in biological media. The clear motivation is that an increased understanding will lead to reduced damage of healthy tissue and, potentially, to efficient targeting (e.g. of cancerous growths). We regularly receive requests to provide cross-section data and we will alert scientists working in this field to our new findings as they emerge. |
| First Year Of Impact | 2016 |
| Sector | Chemicals,Healthcare |
| Impact Types | Cultural,Societal |
| Description | EPSRC DTP 2018-22 |
| Amount | £800,000 (GBP) |
| Funding ID | EP/R513143/1 |
| Organisation | University College London |
| Sector | Academic/University |
| Country | United Kingdom |
| Start | 10/2018 |
| End | 09/2022 |
| Description | UCL RCIF Capital Equipment Fund |
| Amount | £30,000 (GBP) |
| Funding ID | - |
| Organisation | University College London |
| Sector | Academic/University |
| Country | United Kingdom |
| Start | 08/2018 |
| End | 07/2019 |
| Title | A statistical description of scattering at the quantum level |
| Description | Quantum physics is undoubtedly the most successful theory of the microscopic world, yet the complexities which arise in applying it even to simple atomic and molecular systems render the description of basic collision probabilities a formidable task. For this reason, approximations are often employed, the validity of which may be restricted to given energy regimes and/or targets and/or projectiles. Now we have found that the lognormal function, widely used for the probability distribution of macroscopic stochastic events (as diverse as periods of incubation of and recovery from diseases, size of grains, abundance of species, fluctuations in economic quantities, etc.) may also be employed to describe the energy dependence of inelastic collisions at the quantum level (including ionization, electron capture and excitation by electrons, positrons, protons, antiprotons, etc.), by allowing for the relevant threshold energy. A physical interpretation is discussed in this article by analogy with the heat capacity of few-level systems in solid state physics. We find the generality of the analysis to extend also to nuclear reactions. As well as aiding the description of collision probabilities for quantum systems, this finding is expected to impact also on the fundamental understanding of the interface between the classical and quantum domains. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2018 |
| Provided To Others? | Yes |
| Impact | External downloads; Application and extension of method to other systems. |
| URL | http://discovery.ucl.ac.uk/10057312/ |
| Title | Angle-resolved electron scattering from H2O near 0o |
| Description | An electron beam, characterized by a high-angular discrimination (?0.7°), has been used to measure the total (elastic plus inelastic) cross section of H2O in the energy range 3-100 eV. Broad coincidence is found with recent experiments, including a pronounced shoulder in the 6-12 eV region. However, at energies ?6eV, the present cross sections are ?30% higher. Furthermore, forward scattering has been probed in the angular range 0°-3.5° and measures of the average (rotationally and vibrationally summed) differential elastic cross sections for incident energies =12 eV are obtained at a scattering angle ?1°. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2019 |
| Provided To Others? | Yes |
| Impact | The measurements, which provide the first test of theoretical predictions in an angular region experimentally unexplored until now, are found to be within 1 standard deviation of corresponding ab initio R-matrix calculations. |
| URL | https://discovery.ucl.ac.uk/id/eprint/10074515/ |
| Title | Detection of low-energy charged particles by channel electron multipliers |
| Description | The data supporting the findings of D.M. Newson et al 2022 JINST 17 P11026 |
| Type Of Material | Database/Collection of data |
| Year Produced | 2022 |
| Provided To Others? | Yes |
| Impact | Channel electron multipliers are important tools in the detection of particles in a variety of environments on Earth and in space. The detection efficiencies of such devices, from the impact of ions, atoms and molecules, have been studied extensively and predictive relationships, with energy, velocity or mass of the incident projectiles. |
| URL | https://discovery.ucl.ac.uk/id/eprint/10158097/ |
| Title | Differential positronium-formation cross sections for Ne, Ar, Kr, and Xe |
| Description | Experimental determinations of the absolute differential positronium-formation cross sections near 0? for Ne, Ar, Kr, and Xe are presented and compared with theory. The degree of forward collimation, expressed by the ratios of the differential-to-integral positronium-formation cross sections, is also computed and compared with theories and other targets. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2019 |
| Provided To Others? | Yes |
| Impact | Trends among targets and structures at low energies emerge when considered as a function of the reduced total energy. |
| URL | https://discovery.ucl.ac.uk/id/eprint/10088167/ |
| Title | Low-Energy Positronium Scattering from O2 |
| Description | The data that support the findings of Newson et al PHYSICAL REVIEW A 107, 022809 (2023) |
| Type Of Material | Database/Collection of data |
| Year Produced | 2023 |
| Provided To Others? | Yes |
| Impact | The purely leptonic nature of Ps makes it an ideal subject for testing predictions of quantum electrodynamics, and its light mass and neutrality render it an interesting projectile, especially when compared with e+, e-, ions, and other atoms. It is expected that the present results will stimulate in the future experimental investigations with higher-energy resolution and precision accompanied by further refinements in concomitant theoretical descriptions. |
| URL | https://discovery.ucl.ac.uk/id/eprint/10164844/ |
| Title | Positron + H2O scattering |
| Description | Using a purely electrostatic positron beam, the total cross section of positrons scattering from H2O has been measured for the first time with a high angular discrimination (' 1 ) against forward scattered projectiles. Results are presented in the energy range (10-300) eV. Significant deviations from previous measurements are found which are, if ascribed entirely to the angular acceptances of various experimental systems, in quantitative accord with ab-initio theoretical predictions of the differential elastic scattering cross section. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2016 |
| Provided To Others? | Yes |
| Impact | External downloads; application and extension of method to electron + H2O scattering. |
| URL | http://discovery.ucl.ac.uk/1529854/ |
| Title | Statistical nature of secondary electron emission |
| Description | The data supporting the findings of Newson, D., Kadokura, R., Brawley, S., Shipman, M., & Laricchia, G. (2023). Statistical nature of secondary electron emission. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. doi:10.1016/j.nimb.2023.01.008 |
| Type Of Material | Database/Collection of data |
| Year Produced | 2023 |
| Provided To Others? | Yes |
| Impact | Secondary electron (SE) emission is the excitation of a valence or core electron by an incident (primary) particle such that the excited electron is ejected from the surface of the material, typically associated with a kinetic energy = 50 eV. The SE yield or coefficient is the number of SEs produced per incident projectile as a function of the primary kinetic energy and is relevant to a wide- range of applications including scanning electron microscopes, particle accelerators [2,3], fusion apparatus [4], satellite systems [5] and extreme ultraviolet lithography. |
| URL | https://discovery.ucl.ac.uk/id/eprint/10163263/ |
| Description | ATOMKI |
| Organisation | Hungarian Academy of Sciences (MTA) |
| Country | Hungary |
| Sector | Academic/University |
| PI Contribution | Positron physics expertize |
| Collaborator Contribution | Ion collision physics expertize |
| Impact | Record 1 of 4 Title: Low-energy positronium scattering from O2 Author(s): D. M. Newson , R. Kadokura, H. Allen , S. E. Fayer, S. J. Brawley , M. Shipman , and G. Laricchia *; R. S. Wilde, I. Fabrikant, L. Sarkadi Source: PHYSICAL REVIEW A 107, 022809 (2023); https://journals.aps.org/pra/pdf/10.1103/PhysRevA.107.022809 Addresses: [D. M. Newson , R. Kadokura, H. Allen , S. E. Fayer, S. J. Brawley , M. Shipman , and G. Laricchia], Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom; [R. S. Wilde] Department of Natural Sciences, Oregon Institute of Technology, Klamath Falls, Oregon 97601, USA [I. Fabrikant] Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588-0299, USA [L. Sarkadi] ATOMKI, Institute for Nuclear Research, H-4026 Debrecen, Bem ter 18/c, Hungary Title: Angle-Resolved Electron Scattering from H2O near 0 degrees Author(s): Kadokura, R (Kadokura, R.); Loreti, A (Loreti, A.); Kover, A (Kover, A.); Faure, A (Faure, A.); Tennyson, J (Tennyson, J.); Laricchia, G (Laricchia, G.) Source: PHYSICAL REVIEW LETTERS Volume: 123 Issue: 3 Article Number: 033401 DOI: 10.1103/PhysRevLett.123.033401 Published: JUL 16 2019 Addresses: [Kadokura, R.; Loreti, A.; Tennyson, J.; Laricchia, G.] UCL, UCL Dept Phys & Astron, Gower St, London WC1E 6BT, England. [Kover, A.] MTA Inst Nucl Res Atomki, Bem Ter 18-c, H-4026 Debrecen, Hungary. [Faure, A.] Univ Grenoble Alpes, 621 Ave Cent, F-38400 St Martin Dheres, France. Reprint Address: Kadokura, R (reprint author), UCL, UCL Dept Phys & Astron, Gower St, London WC1E 6BT, England Experiment & Theory Title: Resonant scattering of positronium as a quasifree electron Author(s): Shipman, M (Shipman, M.); Brawley, SJ (Brawley, S. J.); Sarkadi, L (Sarkadi, L.); Laricchia, G (Laricchia, G.) Source: PHYSICAL REVIEW A Volume: 95 Issue: 3 Article Number: 032704 DOI: 10.1103/PhysRevA.95.032704 Published: MAR 21 2017 Addresses: [Shipman, M.; Brawley, S. J.; Laricchia, G.] UCL, Dept Phys & Astron, Gower St, London WC1E 6BT, England. [Sarkadi, L.] Hungarian Acad Sci ATOMKI, Inst Nucl Res, Pf 51, H-4001 Debrecen, Hungary. Experiment & Theory Title: High-Resolution Measurements of e(+) + H2O Total Cross Section Author(s): Loreti, A (Loreti, A.); Kadokura, R (Kadokura, R.); Fayer, SE (Fayer, S. E.); Kover, A (Kover, A.); Laricchia, G (Laricchia, G.) Source: PHYSICAL REVIEW LETTERS Volume: 117 Issue: 25 Article Number: 253401 DOI: 10.1103/PhysRevLett.117.253401 Published: DEC 16 2016 Addresses: [Loreti, A.; Kadokura, R.; Fayer, S. E.; Laricchia, G.] UCL, UCL Dept Phys & Astron, Gower St, London WC1E 6BT, England. [Kover, A.] Hungarian Acad Sci, Inst Nucl Res, POB 51, H-4001 Debrecen, Hungary. Reprint Address: Laricchia, G (reprint author), UCL, UCL Dept Phys & Astron, Gower St, London WC1E 6BT, England. Title: Magnetic field-free measurements of the total cross section for positrons scattering from helium and krypton Author(s): Fayer, SE (Fayer, S. E.); Loreti, A (Loreti, A.); Andersen, SL (Andersen, S. L.); Kover, A (Koever, A.); Laricchia, G (Laricchia, G.) Source: JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS Volume: 49 Issue: 7 Article Number: 075202 DOI: 10.1088/0953-4075/49/7/075202 Published: APR 14 2016 Addresses: [Fayer, S. E.; Loreti, A.; Laricchia, G.] UCL, UCL Dept Phys & Astron, Gower St, London WC1E 6BT, England. [Andersen, S. L.] Aarhus Univ, Dept Phys & Astron, DK-8000 Aarhus C, Denmark. [Koever, A.] Hungarian Acad Sci, Inst Nucl Res, POB 51, H-4001 Debrecen, Hungary. |
| Start Year | 2016 |
| Description | Curtin University, GPO Box U1987, Perth, WA 6845, Australia |
| Organisation | Curtin University |
| Country | Australia |
| Sector | Academic/University |
| PI Contribution | Experimental positron and positronium scattering expertise. |
| Collaborator Contribution | Theoretical positron and positronium scattering expertise. |
| Impact | Interference effects in positronium formation from molecules, in preparation 2021 |
| Start Year | 2020 |
| Description | Oregon Institute of Technology, USA |
| Organisation | Oregon Institute of Technology |
| Country | United States |
| Sector | Academic/University |
| PI Contribution | Experimental Positronium Scattering expertise |
| Collaborator Contribution | Theoretical Positronium Scattering expertise |
| Impact | Low-energy positronium scattering from O2, PHYSICAL REVIEW A 107, 022809 (2023) |
| Start Year | 2020 |
| Description | University of Nebraska |
| Organisation | University of Nebraska-Lincoln |
| Country | United States |
| Sector | Academic/University |
| PI Contribution | Experimental Positronium Scattering expertise |
| Collaborator Contribution | Theoretical Positronium Scattering expertise |
| Impact | Low-energy positronium scattering from O2, PHYSICAL REVIEW A 107, 022809 (2023) |
| Start Year | 2020 |
| Description | "Maths formula links clouds, marriages and atoms" UCL MAPS Website |
| Form Of Engagement Activity | Engagement focused website, blog or social media channel |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Public/other audiences |
| Results and Impact | Maths formula links clouds, marriages and atoms: UCL scientists have made a new discovery that will help describe and predict how collision probabilities involving subatomic particles vary with energy. The same mathematical formula which describes the probability distribution of phenomena such as periods of incubation of diseases, size of clouds, abundance of species, age of marriage, fluctuations in economic variables, etc, also applies at the quantum level, UCL scientists find. The discovery, published today in Scientific Reports, will help in describing and predicting how collision probabilities involving subatomic particles vary with energy. It is expected to impact on a fundamental issue in physics, that of the boundary between the classical and quantum domains. Professor Gaetana Laricchia (UCL Physics & Astronomy) who led the work, said: "The question of where the classical world ends and the quantum one begins is a major concern in physics. Our finding is particularly exciting because of its breadth and simplicity, and because it links systems normally described by quantum theories to those in the classical regime." "Our initial investigation arose in the context of atomic collisions with positrons", the positron being the antimatter counterpart to the electron, that is the same mass but opposite charge. "At first, we noticed similarities among different atoms. So we searched for a common mathematical expression and found that a formula - the "lognormal distribution" - widely used for large scale phenomena, unexpectedly worked well not only for different atomic targets but also different projectiles and processes."". The prediction and measurement of collision probabilities at the quantum level engage theorists and experimentalists worldwide, quantum theoretical approaches requiring complex calculations and being currently restricted to given physical systems, processes or energy regimes. In the present statistical description, observed to be valid over a broad energy range, the only quantum input is the minimum energy required for the process under consideration. In analogy with studies of clouds and marriages, the authors conjecture that the behaviour arises if the outcome of the collision is the product of many independent random effects. The generality of the analysis, namely its independence from the details of the forces at play, is reinforced by their finding that the formula also applies to solid state and nuclear physics problems. |
| Year(s) Of Engagement Activity | 2018 |
| URL | https://www.ucl.ac.uk/mathematical-physical-sciences/news/2018/oct/maths-formula-links-clouds-marria... |
| Description | IOP Conference of Physics and Astronomy Students |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Undergraduate students |
| Results and Impact | Every year a university in the UK hosts the Conference of Physics and Astronomy Students, an Institute of Physics event. The stated aims are that "undergraduate students learn about the exciting cutting edge research undertaken by both distinguished professors from around the country and fellow physics colleagues alike; all the being able to network and get to know the other attendees through the various planned social events". I was invited by the Student Organizing Committee to deliver a 1-hr lecture on my research interests entitled "Collision involving antimatter". |
| Year(s) Of Engagement Activity | 2017 |
| URL | http://www.ucl.iopcaps.co.uk/#theconference |
| Description | Winter Research Symposium (Donovan Newson) |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Study participants or study members |
| Results and Impact | Opportunity for postgraduate students and early career researchers to present their results to a broader research group. |
| Year(s) Of Engagement Activity | 2021 |
| Description | Women's day seminar invitation |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Postgraduate students |
| Results and Impact | Spectroscopy and Dynamics 'Supergroup' seminars for several chemistry department research groups to an audience of approx. 30 people. |
| Year(s) Of Engagement Activity | 2019 |