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FCC-FS EPOL group meeting 48
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Europe/Zurich
6/R-012 - conference room (CERN)
Description
The FCC technical and financial feasibility study comprises a work package (EPOL) on precision determination of the centre of mass energy at FCCee. using resonant depolarisation of the beams, in conjunction with precise measurement of the energy spread and other parameters using physics events in the detectors, and other beam diagnostics in particular to control the collision parameters. Specific equipment involves polarimeters for both beams, polarisation wigglers, and depolarising RF kickers. The possible mono-chromatization of the beams in view of a measurement of the e+ e- —> H (125) process will also be studied and special requirements investigated.
Short group meetings are foreseen at 15:00 on Friday.
FCC-FS EPOL group meeting
Zoom Meeting ID
63437787216
Host
Alain Blondel
Alternative host
Jacqueline Keintzel
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G. Wilkinson presents that the plan for deliverables and milestones for the next 2 years have been developed with various colleagues. From the PED side he presents the relevant deliverables and milestones and also until when they should be achievable. A more presentation is aimed being prepared by the next EPOL meeting by G. Wilkinson, J. Keintzel and E. Torrence.
J. Eysermann presents on Ecm related quantities. He stresses that the sequence should be from lower to higher energies. J. Keintzel adds that energies which are not yet included in the baseline are not straight forward to run at and would require equally detailed studies. J. Bendavid suggests to understand clearly the ptp uncertainties. J. Keintzel adds that Y. Wu has started to study this and more work is needed. Center-of-mass energy must be known precisely until 345 GeV, not neccessarily up to 365 GeV. Correlation of uncertainties at energies around the ttbar threshold should be studied. On slide 16 a table on the requirements on the Ecm is given. G. Wilkinson adds that at 125 GeV the energy should be known in real time up to a a few keV. J. Keintzel suggests to also add the requirements on the Ecm spread. G. Wilkinson clarifies that LEP only did RDP until about 60 GeV. J. Eysermann stresses that the Ecm uncertainties must be developed. Main question at 240 GeV is how well the Ecm can be tracked and corrected around which value (compared to the beam energy spread)?
J. Bendavid presents news on the µµ as complementary measurement of the beam energy. One of the key questions is what is the vacuum pressure in the machine? It is assumed to only measure µ-minus. J. Keintzel raises the question if this would have impact on CE. J. Bandavid answers no. Following another question by J. Keintzel, J. Bendavid answers that depending on the impact on the beam this could or not be in parallel to physics operation, but performed on non colliding bunches but full intensity - tbd.
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