Discovery of Matter Anti-matter Asymmerty in the Charm Sector
Lead Research Organisation:
University of Manchester
Department Name: Physics and Astronomy
Abstract
Symmetries play an essential role in our understanding of the universe. Nature exhibits a stunning level of symmetry across all scales, from the bilateral symmetry of many animal's bodies to the mathematical symmetry of the fundamental physical laws. But only the imperfections of symmetries reveal the full picture. In astrophysics for example, the anisotropy of the cosmic microwave background radiation has given insight into the structure of the universe roughly 300,000 years after the big bang.
At the Large Hadron Collider (LHC) we study the type of physics which governed the processes just a fraction of a second after the big bang. The LHC, located 100m underground just outside Geneva, collides protons at energies that have never previously been reached in a laboratory on earth. The smallest of the four large experiments at the LHC is known as LHCb, and is specifically designed to discover asymmetries in the behaviour of matter and antimatter.
In our current understanding, matter consists of twelve fundamental particles: the six quarks (u, d, s, c, b, t ordered by increasing mass), and an electron with its heavier partners muon and tau and their three associated neutrinos. These interact by the exchange of so-called bosons, which are fundamental force carrying particles. The standard model of particle physics (SM) explains these matter interactions and has so far held up to all experimental tests. However, it fails to give explanations to basic questions like the reason why the t-quark is over 50,000 times heavier than the u-quark. Another is the puzzle that perfect symmetry would lead to equal amounts of matter and antimatter and the annihilation of the universe shortly after the big-bang. Questions like these tell us that the SM does not cover all aspects of fundamental interactions and therefore has to be extended.
Nature has given us three special laboratories to study matter and antimatter interaction: neutral mesons (called K, B and D-meson), particles consisting of one quark (matter) and one antiquark (antimatter). These mesons periodically change into their antiparticle and back, a process called mixing. The studies of two of these systems (K and B mesons) have led to Nobel-prize winning breakthroughs. I will study the mixing phenomenon in the third system, known as the D-meson system. Particularly, I will be looking for a tiny asymmetry in this process, an asymmetry between the behaviour of matter and antimatter. Such an asymmetry has been observed in the K and B-meson systems but remains to be detected in D-mesons.
The LHCb experiment is the best apparatus for measuring D-mesons for at least the next decade. The asymmetry in D-mesons I am looking for is predicted to be tiny in the SM. The precision we can achieve allows the observation of this effect if it is enhanced beyond the SM level. Detailed analyses of several processes involving D-mesons cannot only give evidence for new physics phenomena but also allow to identify the type of new physics by comparison with existing models.
Particle physics research continues to lead to technological benefits to society, from the World Wide Web to medical imaging, but its true purpose will always be the search for fundamental understanding of our universe. My goal is to further this understanding, using the matter-antimatter asymmetry to reveal nature's beauty. And true beauty lies in imperfections.
At the Large Hadron Collider (LHC) we study the type of physics which governed the processes just a fraction of a second after the big bang. The LHC, located 100m underground just outside Geneva, collides protons at energies that have never previously been reached in a laboratory on earth. The smallest of the four large experiments at the LHC is known as LHCb, and is specifically designed to discover asymmetries in the behaviour of matter and antimatter.
In our current understanding, matter consists of twelve fundamental particles: the six quarks (u, d, s, c, b, t ordered by increasing mass), and an electron with its heavier partners muon and tau and their three associated neutrinos. These interact by the exchange of so-called bosons, which are fundamental force carrying particles. The standard model of particle physics (SM) explains these matter interactions and has so far held up to all experimental tests. However, it fails to give explanations to basic questions like the reason why the t-quark is over 50,000 times heavier than the u-quark. Another is the puzzle that perfect symmetry would lead to equal amounts of matter and antimatter and the annihilation of the universe shortly after the big-bang. Questions like these tell us that the SM does not cover all aspects of fundamental interactions and therefore has to be extended.
Nature has given us three special laboratories to study matter and antimatter interaction: neutral mesons (called K, B and D-meson), particles consisting of one quark (matter) and one antiquark (antimatter). These mesons periodically change into their antiparticle and back, a process called mixing. The studies of two of these systems (K and B mesons) have led to Nobel-prize winning breakthroughs. I will study the mixing phenomenon in the third system, known as the D-meson system. Particularly, I will be looking for a tiny asymmetry in this process, an asymmetry between the behaviour of matter and antimatter. Such an asymmetry has been observed in the K and B-meson systems but remains to be detected in D-mesons.
The LHCb experiment is the best apparatus for measuring D-mesons for at least the next decade. The asymmetry in D-mesons I am looking for is predicted to be tiny in the SM. The precision we can achieve allows the observation of this effect if it is enhanced beyond the SM level. Detailed analyses of several processes involving D-mesons cannot only give evidence for new physics phenomena but also allow to identify the type of new physics by comparison with existing models.
Particle physics research continues to lead to technological benefits to society, from the World Wide Web to medical imaging, but its true purpose will always be the search for fundamental understanding of our universe. My goal is to further this understanding, using the matter-antimatter asymmetry to reveal nature's beauty. And true beauty lies in imperfections.
Publications
Aaij R
(2017)
Measurement of B s 0 and D s - Meson Lifetimes
in Physical Review Letters
Aaij R
(2017)
Measurement of B0, B s 0 , B+ and ? b 0 production asymmetries in 7 and 8 TeV proton-proton collisions
in Physics Letters B
Aaij R
(2015)
Measurement of Bc+ Production in Proton-Proton Collisions at v[s]=8 TeV.
in Physical review letters
Aaij R
(2018)
Measurement of branching fractions of charmless four-body ? b 0 and ? b 0 decays
in Journal of High Energy Physics
Aaij R
(2018)
Measurement of C P asymmetries in two-body B ( s ) 0 -meson decays to charged pions and kaons
in Physical Review D
Aaij R
(2013)
Measurement of C P violation and the B s 0 meson decay width difference with B s 0 ? J / ? K + K - and B s 0 ? J / ? p + p - decays
in Physical Review D
Aaij R
(2014)
Measurement of C P violation in B s 0 ? ? ? decays
in Physical Review D
Aaij R
(2014)
Measurement of C P violation parameters in B 0 ? D K * 0 decays
in Physical Review D
Aaij R
(2019)
Measurement of Charged Hadron Production in Z-Tagged Jets in Proton-Proton Collisions at sqrt[s]=8 TeV.
in Physical review letters
LHCb Collaboration
(2014)
Measurement of charged particle multiplicities and densities in [Formula: see text] collisions at [Formula: see text]TeV in the forward region.
in The European physical journal. C, Particles and fields
Description | The key objective of the project is the discovery of differences of matter to antimatter particle decays of particles involving charm quarks. The research is conducted based on data collected by the LHCb experiment at the LHC at CERN. This discovery has been realised in March 2019. This groundbreaking result opens the door to further detailed investigations of the phenomenon, in particular as there are two types of matter-antimatter asymmetries (CP violation) and only one has been discovered in particles involving charm quarks to date. This project had major involvements in investigations into both types of CP violation. Laying the groundwork for the future of LHCb and its upgrade programme is an important part of this project. In this context work has been undertaken to develop new trigger selection algorithms and on the development of the readout electronics of the next-generation vertex detector. |
Exploitation Route | This research provides lasting insight into matter-antimatter differences of particles containing charm quarks. In this field the world's knowledge will be shaped for the foreseeable future by results of the LHCb experiment. The novel methods developed in this project will be applicable in a wide range of physics analyses. Concretely, several analyses are being carried out by my team that build on work from this grant and that are being undertaken as a result of previous outcomes. |
Sectors | Education,Other |
URL | http://lhcb-public.web.cern.ch/lhcb-public/ |
Description | The direct use of our findings is restricted to dissemination by the PI and other team members. The findings have obviously been published in open access journals and these publications have allowed other members of the community to use our input to extract underlying theory parameters and to constrain models for possible extensions of our current understanding of particle physics. These findings also feed into presentations to the general public. This included a presentation at the Bluedot festival to an audience of more than 500 people. This has been done e.g. through educational visits of school and university groups to CERN. In addition, several dedicated events at science festivals and school visits have been held. The discovery was also covered in an article in The Conversation, which attracted over 100,000 readers. |
First Year Of Impact | 2012 |
Sector | Education,Other |
Impact Types | Societal |
Description | IPPP Associateship |
Amount | £4,000 (GBP) |
Organisation | Durham University |
Department | Institute for Particle Physics Phenomenology (IPPP) |
Sector | Academic/University |
Country | United Kingdom |
Start | 10/2012 |
End | 09/2013 |
Description | IPPP Associateship |
Amount | £3,000 (GBP) |
Organisation | Durham University |
Department | Institute for Particle Physics Phenomenology (IPPP) |
Sector | Academic/University |
Country | United Kingdom |
Start | 09/2016 |
End | 08/2017 |
Description | LHCb collaboration |
Organisation | European Organization for Nuclear Research (CERN) |
Department | CERN LHC LHCb |
Country | Switzerland |
Sector | Public |
PI Contribution | Data analysis, mainly in charm physics, CP violation, rare decays. Vertex detector operation, R&D for upgrade. Simulation development. Various leadership roles. |
Collaborator Contribution | M&O of the experiment, collaboration on analyses. |
Impact | As submitted by LHCb-UK. |
Start Year | 2012 |
Description | Mu2e collaboration |
Organisation | Fermilab - Fermi National Accelerator Laboratory |
Department | Mu2e |
Country | United States |
Sector | Public |
PI Contribution | Design of a collimator system for stopping target monitoring system. |
Collaborator Contribution | Data analyses, detector R&D and construction. |
Impact | None yet. |
Start Year | 2017 |
Description | Antimatter matters exhibition at Royal Society Summer Science Exhibition (London) |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | The centrepiece of this grant, a coupled double pendulum, was on of the main exhibits used to describe antimatter. The stand was visited by approximately 10,000 visitors. |
Year(s) Of Engagement Activity | 2016 |
URL | https://royalsociety.org/science-events-and-lectures/summer-science-exhibition/exhibits/antimatter-m... |
Description | Guide for visits to LHCb |
Form Of Engagement Activity | Participation in an open day or visit at my research institution |
Part Of Official Scheme? | No |
Type Of Presentation | Keynote/Invited Speaker |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | Several guided tours each year of the LHCb experimental underground area including an introductory presentation. This includes CERN Open Days with several tens of thousands of visitors. Returning visit groups from several international universities. Introduction of public tours for people living in the area around CERN. |
Year(s) Of Engagement Activity | Pre-2006,2006,2007,2008,2009,2010,2011,2012,2013,2014 |
Description | School visit Islay |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | The Science Hand exhibit was given to a local school on Ilsay as part of an outreach event linked to a physics workshop held on the island. |
Year(s) Of Engagement Activity | 2016 |
Description | School visit to university (Manchester) |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | The Science Hands team hosted a class of 20 secondary school children who followed the activity as part of a visit to the University of Manchester. |
Year(s) Of Engagement Activity | 2016 |
URL | http://sciencehands.hep.manchester.ac.uk/Welcome.html |