Add PDG IDs of QBalls / multi-charged particles to the ->isBSM() test.
Hello,
this MR aims to add the PDG IDs of QBalls / multi-charged particles to the ->isBSM() test.
The QBalls and similar very exotic BSM particles which may have large, non-integer charge, are assigned the PDG ID numbering ±100XXXY0, where the charge is XXX.Y. (This was initially discussed in this discourse thread.)
The MadGraph models of the QBalls / multi-charged particles are located here https://gitlab.cern.ch/atlas-generators-team/MadGraphModels/-/tree/main/Charge in the multichargedParticles/ folder.
There aren't any papers describing the exact model, but there are four previous Run-I and Run-II ATLAS searches, which have used this model before:
- http://arxiv.org/abs/1301.5272 (Run-I 7 TeV)
- http://arxiv.org/abs/1504.04188 (Run-I 8 TeV)
- https://arxiv.org/abs/1812.03673 (partial Run-II)
- https://arxiv.org/abs/2303.13613 (full Run-II)
(Additional references for examples of theories motivating the model: QBalls: https://arxiv.org/abs/hep-ph/9709492, AC-leptons: https://arxiv.org/abs/astro-ph/0511789, Technibaryons: https://arxiv.org/abs/hep-ph/0405209)
The implementation adds two updates to AtlasPID.h:
- the first is adding an isQBall() method: it checks the PDG ID and if it is true, isBSM() is also set to true
- the second is updating the charge calculation to be able to handle fractional charges of QBalls: a method fractionalCharge() is introduced to handle cases where the charge is not a multiple of 1/3, and then the charge() is calculated from there for QBalls
The test file AtlasPIDTest.ref is updated as well (with a few reperesentative QBall examples added) and running make test gives successful results.
- Judith