PhD Thesis -- Systematics -RPM 06.10.30 CHAPTER COMMENTS: This chapter should probably be confined to studies of the "systematic uncertainties" themselves. Details of things like the match between data and MC or the methods of measuring alignment etc don't belong here. Keep this chapter simple, with lots of back references. Organize the chapter according to "categories" of systematics. Start each category with a table listing the contents, and the quadrature sum. (This category table should be fairly short, and is a rare candidate for "here" table placement! In fact, I might not even want it in a "table" environment -- if I don't want it to float at all, why wrap it in a floating body? OTOH, "htp" might work best, as it gives LaTeX at least a little flexibility.) Include a section reference for each systematic. Have a subsection, however short, for each actual systematic. For each systematic, give details of what it is and where it comes from. Is it worth mentioning here what the equivalent systematics were for previous rounds? Or do I get into too much trouble when the definitions of the systematics change (or I have to hand-wave my way through the previous measurements because they were never adequately described!)? In any case, it's certainly worth mentioning the previous rounds' total systematic uncertainties for comparison. - Listing the corresponding systematics for previous rounds is probably going to be expected. I should at least list the systematics for each category... I should pay attention to which lines have been removed from previous tables, and make sure I can justify their removal to the committee -- sounds like an awfully good defense question... CHAPTER OUTLINE: Introduction - Summary List (floating table) - Just each category, plus Grand Total. - Overview of the systematics measurement philosophy. - I don't think this gets mentioned previously, nor should it. - Identify sources of systematic uncertainty. - Measure uncertainty. - Measure impact on Michel parameters by comparison of exaggerating the source of the uncertainty, and scaling it back to what we measure. - Comments on general sources of improvement over previous rounds. - Shouldn't go into great details here. If there are improvements worth describing in detail, I should do so in the TWIST sections. - Should directly address the leading sources of error in the previous measurements. - Probably just an overview similar to my CAP 2007 slide, describing in brief the major improvements to each systematics category. Better systematics measurements (improved methodology, greater statistics) help across the board, of course. Highlights of other improvements to the TWIST experiment since the previous rho and delta measurements include: - Positron interactions: precision target geometry - Stopping target thickness: precision target geometry - Momentum calibration: new calibration techniques - Spectrometer alignment: improved alignment testing - Chamber response: Online monitoring, increased instrumentation Positron Interactions - How exactly I lay out this will depend on the "basis set" I ultimately settle on. Momentum Calibration - End point fits - Energy Loss Dependence - This might change or disappear, depending on how the ecal understanding shakes out. - Field Map - Mention here our knowledge of the overall scale of the magnetic field strength, and the effect on the energy scale; point out that the uncertainty is small enough that it is not in itself a source of systematic error. - Need to find out the uncertainty of the NMR probes measuring the field in the detector. - The real uncertainty is not the NMR probe precision, but the uncertainty in matching the NMR against the field map, which is about 1G. This is actually a potentially important systematic, but it's supposed to be corrected by the energy calibration. So really this is the "energy calibration" systematic. As a result I probably don't really need to go into detail about the online field measurement. - How many working NMR probes did we have in 2004? - There was only one probe typically in use in 2004. The other was activated from time to time to confirm relative measurements. - NMR probe locations: DS: u=-62.0 mm; v=+165.8 mm; z=+127. mm US: u=+164.9 mm; v=-61.6 mm; z=-121. mm from RobertO's numbers https://twist.phys.ualberta.ca/forum/view.php?site=twist&bn=twist_mechanical&key=1020305978 which Glen translated into TWIST coordinates https://twist.phys.ualberta.ca/forum/view.php?site=twist&bn=twist_software&key=1085772387 and which I should probably consider converting to (x,y,z) coordinates for the thesis. - Field map systematic posting: https://twist.phys.ualberta.ca/forum/view.php?site=twist&bn=twist_physics&key=1161715256 Spectrometer Alignment (no subsections, but its own table with two lines) - Translation - Rotation Spectrometer Length Scales - (Moved length scales here from Alignment Systematic because these aren't really alignment issues. They don't get aligned, for one thing. Length scales are defined by construction, and measured directly.) - Z - U/V Chamber Response - Dead zone - Foil bulges - Cell asymmetry - US-DS Efficiency Asymmetry - This will focus on _reconstruction_ efficiency, I think. - Need to show some sample events of US Stops positron tracks that got reconstructed in one half of the detector but not in the other. - t0 variations/biases Muon Beam Stability - Stopping location - Beam intensity Theoretical Uncertainties - Radiative corrections - Uncertainty in eta Negligibly Small Systematics - Hard scattering - Stopping distribution - ...see Systematics Spreadsheet - ...compare my list with previous rounds, and include anything I've dropped