LHCb top asymmetry

Lead Research Organisation: University of Liverpool
Department Name: Physics

Abstract

The Large Hadron Collider is the most powerful particle accelerator ever constructed. LHCb, one of its four major experiments, provides unique detector coverage of proton beam collisions. Specialised for particle identification, utilising advanced tracking and mass determination; the full detector is layered perpendicular to the beams in one 'forward' direction from the interaction point, where the incoming beams define the forward-backward axis. As a result, LHCb can contribute to unprecedented forward region studies.
Matter and antimatter are frequently produced together from the energies accessible in accelerator experiments. Quarks, the building blocks of subatomic matter making up protons, are produced alongside anti-quarks in high energy interactions. The expected angular distributions of the particles being emitted differs between matter and anti-matter; quarks tend to fall closer to the beam-line by comparison. Measuring the direction of these pairs allows us to quantify the differences, or asymmetry, between matter and antimatter.
The top quark has a very short lifetime, so any measurable asymmetry would rely on charge reconstruction through its decay products. Only accessible through quantum mechanical interference, the mechanism for the asymmetry, predicted to be largest in the forward region, is sensitive to new physics. Top quarks are the heaviest known fundamental particle, making them, too, particularly sensitive. As a result, they are anticipated to play a key role in physics beyond the Standard Model.
LHCb observed top production through decays to a bottom quark and a muon using Run I data, becoming the fifth experiment to observe top production and the first in the forward region. In performing angular differential cross section measurements for top and anti-top, this analysis will probe the production asymmetry in this same channel using Run II data. The resultant fourfold increase in statistics and improved to signal to background ratio may determine if first signs of new physics appear.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
ST/N504142/1 01/10/2015 31/03/2021
1796908 Studentship ST/N504142/1 01/10/2016 30/09/2020 James Mead
 
Title Deep neural network jet heavy flavour classifier for Run II jets at LHCb 
Description A machine learning repository providing deep learning models to apply to jet flavour identification 
Type Of Material Data analysis technique 
Year Produced 2018 
Provided To Others? Yes  
Impact Improved and stabilised MVA response to jets in Run II of particular use for differential measurements and impacting up to 12 ongoing publications with more in the future 
 
Title Jet configuration for Run II conditions at LHCb 
Description Optimised input selection for clustering algorithms, subsequent identification and jet energy corrections 
Type Of Material Data handling & control 
Year Produced 2018 
Provided To Others? Yes  
Impact Higher efficiency and better reconstruction resolution for jets in Run II impacting up to 12 ongoing publications with more in the future 
 
Description LHCb Starterkit 
Organisation European Organization for Nuclear Research (CERN)
Department CERN LHC LHCb
Country Switzerland 
Sector Public 
PI Contribution Teaching, demonstrating and developing
Collaborator Contribution Teaching, demonstrating and developing Tremendous number of man hours from volunteers has knock on repercussions for a great deal of new researchers moving foward
Impact Development of open source teaching tools, cloud based analysis outreach exercises and python resources for sixth form to early postgrad
Start Year 2017
 
Title LHCb outreach cloud analysis 
Description Cloud based in browser python notebook analysis tools for teaching and outreach 
IP Reference  
Protection Protection not required
Year Protection Granted 2019
Licensed No
Impact Unknown
 
Description CERN-Liverpool Summer School 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Providing the opportunity to visit CERN and attend seminars from staff and postgraduate researchers, get exposure to areas of particle physics not taught until undergrad and get experience in analysis methods, coding and experimental design from first principles
Year(s) Of Engagement Activity 2014,2015,2016,2017,2018,2019
URL https://hep.ph.liv.ac.uk/indico//conferenceDisplay.py?confId=768
 
Description Open days, applicant discovery days 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Students, teachers, parents visit and learn about physics, the department and get presentations and hands on demonstrations of concepts and facilities
Year(s) Of Engagement Activity 2016,2017,2018,2019