FAQ @ Public Meetings

This page summarise the main questions received during talks:

MATHUSLA seminar @ Fermilab – 26 September 2023 (talk). Speaker David Curtin

• Q: why 6 layers in the top?
  A: since the orientations of the tracking planes alternate with each layer, 6 layers means that in each x and y coordinate, we get ideally 3 data points with cm resolution, which is a fairly minimal number for robust tracking.

LLP12 Workshop – 19-23 June 2023 (talk). Speaker Emma Torró

• Q: why did we select scintillators over RPCs?
  A they are easier to operate (no gas, no high voltage, more stable with temperature) and the resolution is still good
• Q: what are we using for cooling?
  A: we don’t plan to cool in the sense of going to, say, 0 C or any specific temperature. There will be cooling in the sense of removing heat so things do not get (much) hotter than ambient. Air flow as well as conduction through whatever it is connected to should be adequate
• Q: are the sensitivity plots taking into account whether the LLP decay products went through any of the tracking layers?
  A: yes they do
• Q: MATHUSLA is big, what would happen if we make it smaller to reduce costs?
  A: it will reduce physics sensitivity if the detector is smaller. The magnitude of the impact depends on how much smaller we are talking about.
• Q: has the usage of the land near CMS be approved?
  A: the land around CMS that could host MATHUSLA is already property of CERN, so if the experiment is approved CERN will reserve that space for MATHUSLA.

LHCP – 22-26 May 2023 (talk). Speaker Mason Proffitt

• Q: how MATHUSLA position in eta compares to where LLPs would be expected?
  A: the proposed location is essentially designed to cover as much solid angle as possible and that it is still fairly transverse compared to forward experiments like FASER. The geometric LLP decay acceptance for the position has been studied
• Q: what is the potential impact on physics other than LLPs (e.g., cosmic rays)?
  A: the potential for cosmic ray physics has been studied by cosmic ray experts in the collaboration. MATHUSLA could allow to make cosmic ray measurements not possible or not easy to do with other experiments
• Q: what’s the estimated cost?
  A: around 100M CHF
• Q: why scintillators instead of RPCs?
  A: the choice was mainly driven by cost and simplicity (e.g., ease of mass production and no need for gas/HV). Tests performed indicate that the scintillators/SiPMs can reach the needed performance for LLP physics targets (and that this choice can have somewhat more impact on cosmic ray physics).
• Q: are the test stand results public?
  A: yes, they are: https://doi.org/10.1016/j.nima.2020.164661