The International Particle Physics Outreach Group (IPPOG) has developed an educational activity that brings the excitement of cutting-edge particle physics research into the classroom. The ATLAS group at the University of Oslo has developed the Z-path, a powerful and popular educational tool allowing high-school students to learn about particle physics, master concepts such as 'event' and 'statistics', and search for new phenomena using real LHC proton-proton collision data. By studying collision events students use the invariant mass technique to identify short-lived particles that decay into 2 leptons, whose properties are recorded by the detector. A few properties of some particles, such as mass and lifetime, can be inferred. The students distinguish between the Z boson - one of the mediators of the weak force - and other particles made of quarks. Furthermore, they apply the same technique to search for new particles, such as the Z’ - the mediator of a new hypothetical force. The ambition to bring important LHC discoveries to the “classroom” is realized using the discovery of the Higgs boson in 2012. Approximately 10% of the ATLAS Run 1 discovery data at 8 TeV centre of mass energy are made available for students to search themselves for the Higgs boson. The work has been presented at various international conferences.
New features concern more advanced students and include missing momentum (a key concept closely related to dark matter); Supersymmetry (SUSY); and other exotic phenomena such as extra space dimensions or new fundamental forces. We propose 3 projects where one or two students per project will analyse LHC proton-proton collision data and investigate these topics in detail. A new platform gives access to real data recorded by the ATLAS detector. A set of Monte Carlo simulation samples can be used to compare measurements to theoretical predictions. In addition to a web-based analysis, the framework also allows the students to write their own analysis programs. The goal is to study Standard Model (SM) processes and search for new physics phenomena such as new particles or new fundamental forces.
Several projects are proposed. Each analysis consists of (i) selecting and studying particular final states made of particles measured by the detector, (ii) identifying the underlying proton-proton collision process(es), and (iii) interpreting the results in terms of a SM measurement or within some new theory.
The proposed projects have a wide scope, with significant room for adaptation depending on the interests of the students and supervisors as well as the available time. They have been used for projects spanning approximately 4-7 weeks in the courses FYS3180 and FYS5555, using both the previous open release of ATLAS data at 8 TeV centre-of-mass energy and more recently the newly released 13 TeV data. When more time is available for the work, the students can go further in terms of scope and analysis methods. An example of this is a recent bachelor thesis featuring advanced methods such as functional form fits to the background distributions, a data-driven background estimate based on dedicated control- and validation regions, and a likelihood-based statistical combination of independent search channels.
Projects in FYS5555 acted as a test bed for the 13 TeV open data release before these data were officially made available through the web, which was possible due to the direct involvement in the open data preparation from the ATLAS group at the University of Oslo.
An introduction and short demo/tutorial is always given at the beginning to all students involved in the ATLAS-related projects. Regular contact with one or more expert supervisors is in general necessary/recommended.
What do 4-lepton final states tell us about the Standard Model and the Higgs boson?
(i) Four charged lepton final state. (ii) pp→ ZZ+X → 4l+X or pp→ H+X→ ZZ+X → 4l+X. X indicates particles needed to satisfy the basic conservation rules. (iii) Test of the electroweak theory and study of the Higgs boson.
Do new fundamental forces or extra space dimensions show up at the LHC the way the Z and Higgs bosons did?
(i) Dilepton and diphoton final states. (ii) pp→ γ,Z, Z’,G→ l+l- +X , pp→H,G→γγ + X. (iii) Study of known particle resonances, search for new ones in dilepton and diphoton invariant masses, make use of spin to distinguish various outcomes.
Is the world supersymmetric and/or where is Dark Matter?
(i) Dilepton and missing transverse energy (MET) final state. (ii) pp→~l+~l-+X→ l+l-+MET+X, pp→Z+MET+X→ l+l-+MET+X, pp→W+W-+X→ l+l-+MET+X, pp→Z(→l+l-) Z(→νν)+X→ l+l-+MET+X. (iii) Search for SUSY particles (sleptons) and/or Dark Matter.