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Exploring Invariant Mass in Special Relativity: A Masterclass with Régis Lefèvre

Join us for an insightful masterclass led by Régis Lefèvre on March 27th, 2014, focusing on invariant mass within the context of special relativity. We will explore concepts like energy and momentum conservation, and how invariant mass remains constant during particle decay processes. Participants will utilize software to calculate the invariant mass of various particle pairs, including e+e-, μ+μ-, and γγ. We will also delve into histogram representation of occurrence distributions, along with specific cuts used in event analysis based on ATLAS data.

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Exploring Invariant Mass in Special Relativity: A Masterclass with Régis Lefèvre

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Presentation Transcript

  1. End now? Régis Lefèvre Masterclass– Thursday, March 27th 2014

  2. What we will look for

  3. Invariant mass • In special relativity (you certainly know E=mc2), using energy and momentum conservation, a relativistic invariant, called the invariant mass appears. • If a particle decays, the invariant mass of the decay products (calculated in any referential) is the mass of the initial particle. • We will calculate (the software will do it in fact) the e+e-, 𝜇+𝜇-, 𝛾𝛾, e+e-e+e-, e+e-𝜇+𝜇- or 𝜇+𝜇-𝜇+𝜇- invariant mass of our different candidates.

  4. Beyond E = mc2

  5. In the case of Z → e+e-

  6. About histograms • Numbers between 0 and 10 • Distribution of occurrences

  7. About histograms The table can be represented as a graph: Each bar represents the number of occurrences of a given value. This one tells you that the value 7 appeared 16 times. This type of graph is an histogram.

  8. Examples from ATLAS

  9. Cuts we will use • We will only considered tracks with sufficient transverse momentum: pT≥ 5 GeV/c • Selected tracks should come from the same primary vertex (same proton-proton interaction): check it zooming in on the side-view window • If you have difficulties on a given event, you may use Pixel Hits ≥ 2 (tracks more likely to come from a primary vertex)and/or SCT Hits ≥ 7 (good quality tracks); do no forget to remove those cuts moving to the next event

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