<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><br><div><br><div>Begin forwarded message:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;"><span style="font-family:'Helvetica'; color:rgba(0, 0, 0, 1.0);"><b>From: </b></span><span style="font-family:'Helvetica';">Alexander Kiselev <<a href="mailto:kisselev@mail.desy.de">kisselev@mail.desy.de</a>><br></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;"><span style="font-family:'Helvetica'; color:rgba(0, 0, 0, 1.0);"><b>Subject: </b></span><span style="font-family:'Helvetica';"><b>BPMs, magnetic field, MIE, etc</b><br></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;"><span style="font-family:'Helvetica'; color:rgba(0, 0, 0, 1.0);"><b>Date: </b></span><span style="font-family:'Helvetica';">August 30, 2016 at 17:25:56 EDT<br></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;"><span style="font-family:'Helvetica'; color:rgba(0, 0, 0, 1.0);"><b>To: </b></span><span style="font-family:'Helvetica';"><<a href="mailto:schmidta@mit.edu">schmidta@mit.edu</a>><br></span></div><br><div> Hi Axel,<br><br> first, congratulations with your defence. Second (being myself a 12 degree monitor person), let me challenge your 0.27% MIE method systematic<br>uncertainty estimate. Starting with a simple question: was BPM data<br>"corrected" in some sort for the non-vanishing magnetic field along the beam line between BPM#1 and BPM#2?<br><br> I mean ~10-20um match between e+ and e- data sounds a bit of a stretch to me, far beyond the capability of a rather simplistic detector we had in hands. With ~1mT residual fields (perhaps not precisely accounted), ~1.5m BPM#1->BPM#2 distance and 2 GeV/c energy you can easily get far off beyond<br>that when comparing electron and positron *beams*. Which IMHO happens *before* the situation you considered in section 6.4 (fig.6-15).<br><br> By the way, MIE method itself with all the machinery you developed looks fine to me. I just doubt the absolute luminosity ratio normalization<br>accuracy one can get from it.<br><br> Unrelated, concerning fig.8-9: does it mean, that you had to waste ~1/4 or so of the raw data (or do I misinterpret the plot)?<br><br> Cheers,<br> Alexander.<br><br></div></blockquote></div><br></body></html>