<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;" class="">Hi Everyone -<div class=""><br class=""></div><div class=""> I just wanted to comment that there has been spectacular progress on all fronts in</div><div class="">understanding the degree of linear polarization. Everyone involved has done a </div><div class="">fantastic job in getting preliminary results out as quickly as possible, and the entire </div><div class="">collaboration is thrilled to see that within errors, all the methods that we have report</div><div class="">consistent (preliminary) results. We now know that our diamonds are producing </div><div class="">coherent bremsstrahlung and appear quite consistent with our predictions. This</div><div class="">work is something we should all be very proud of.</div><div class=""><br class=""></div><div class=""> We also fully understand that none of these results are final. But the fact that people</div><div class="">are able to get us preliminary results is crucial to our moving forward. I also feel that</div><div class="">without the apparent redundancy that we have, most of us would not be nearly as </div><div class="">comfortable as we are now.</div><div class=""><br class=""></div><div class=""> Curtis</div><div class=""><div class="">
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div class=""><div class="">---------</div><div class="">Curtis A. Meyer<span class="Apple-tab-span" style="white-space: pre; "> </span>MCS Associate Dean for Faculty and Graduate Affairs</div><div class="">Wean: (412) 268-2745<span class="Apple-tab-span" style="white-space: pre; "> </span>Professor of Physics</div><div class="">Doherty: (412) 268-3090<span class="Apple-tab-span" style="white-space: pre; "> </span>Carnegie Mellon University</div><div class="">Fax: (412) 681-0648<span class="Apple-tab-span" style="white-space: pre; "> </span>Pittsburgh, PA 15213</div><div class=""><a href="mailto:curtis.meyer@cmu.edu" class="">curtis.meyer@cmu.edu</a><span class="Apple-tab-span" style="white-space: pre; "> </span>http://www.curtismeyer.com/</div></div><div class=""><br class=""></div></span><br class="Apple-interchange-newline">
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<br class=""><div><blockquote type="cite" class=""><div class="">On Mar 14, 2016, at 8:17 AM, Nathan Sparks <<a href="mailto:nsparks@jlab.org" class="">nsparks@jlab.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">The reported degree of polarization from the TPOL is a rough estimate, based on the information I had available at the time.<br class="">I have no reason to believe it is not in the right ballpark, and it was not presented as a final result.<br class=""><br class="">-Nathan<br class=""><blockquote type="cite" class="">On Mar 14, 2016, at 7:48 AM, <a href="mailto:dugger@jlab.org" class="">dugger@jlab.org</a> wrote:<br class=""><br class="">Hi,<br class=""><br class="">The reported polarizations for the polarimeter are not correct. It was too<br class="">early for the degree of polarization to have been reported.<br class=""><br class="">Take care,<br class="">Michael<br class=""><br class=""><blockquote type="cite" class="">Message from Ken regarding comparison between different methods for beam<br class="">polarization estimation.<br class="">-forwarded by Richard Jones<br class=""><br class="">---------- Forwarded message ----------<br class="">From: Ken Livingston <<a href="mailto:Kenneth.Livingston@glasgow.ac.uk" class="">Kenneth.Livingston@glasgow.ac.uk</a>><br class="">Date: Mon, Mar 14, 2016 at 6:35 AM<br class="">Subject: Re: polarization update<br class="">To: Justin Stevens <<a href="mailto:jrsteven@jlab.org" class="">jrsteven@jlab.org</a>>, Nathan Sparks <<a href="mailto:nsparks@jlab.org" class="">nsparks@jlab.org</a>>,<br class="">Richard Jones <<a href="mailto:richard.t.jones@uconn.edu" class="">richard.t.jones@uconn.edu</a>><br class=""><br class=""><br class="">Hi Justin,<br class="">That a very nice study. It's exactly what's needed. If we believe the<br class="">photon asymmetry for the rho in this energy range is really 1, and are<br class="">convinced that it's very cleanly extracted signal, that's the best<br class="">polarimiter we can have. It has an event rate that's better than the<br class="">triple<br class="">polarimiter and doesn't need an analysing power, and it does not need all<br class="">the vaguely known parameters that are required to match the enhancement<br class="">with a coherent brem calculation.<br class=""><br class="">For the 20 um radiator it's also good to see that, as we'd expect, the<br class="">shape of the enhancement (and hence polarization) is much better with<br class="">collimated data rather than raw scalers. The similarity between the<br class="">polarization for the 20um and 50um is borne out by Nathan's studies<br class="">although the energy range is different (8-9GeV).<br class=""><br class="">It looks like both your studies are assuming that Ppara = Pperp.<br class="">I got the impression from the raw spectra that this might not be true for<br class="">the 20um diamond. It would be good to check this out.<br class="">A quick and check would come from using the more complicated fit function<br class="">I<br class="">sent you earlier, where the flux ratio and pol ratio are free parameters.<br class=""><blockquote type="cite" class="">From this, you could plot the pol ratio as a function of E_gammma, as you<br class=""></blockquote>have for Sigma.<br class=""><br class="">My "phenomenological fit" is clearly not as phenomenal as I'd hoped. It<br class="">doesn't cope with the ~200MeV spread in the coherent edge for the 20um<br class="">diamond. I believed it would. It can fit almost any enhancement, but is<br class="">not<br class="">much use if it doesn't get the corresponsing polarization correct. Either<br class="">I've made a silly assumption somewhere, screwed up the algebra or screwed<br class="">up the code. Maybe all three together - although it generally gives good<br class="">agreement when used to extract asymmetries and compare with previous<br class="">measurements.<br class=""><br class="">I'll need to scrutinise it as soon as I get time.<br class=""><br class=""><br class="">Regards,<br class="">Ken<br class=""><br class=""><br class=""><br class=""><br class=""><br class=""><br class=""><br class="">On 11/03/16 17:06, Justin Stevens wrote:<br class=""><br class=""><blockquote type="cite" class="">FYI, from this mornings meeting: rho and TPOL asymmetries comparing 20<br class="">and<br class="">50 um diamonds.<br class=""><br class=""><a href="https://logbooks.jlab.org/entry/3390212" class="">https://logbooks.jlab.org/entry/3390212</a><br class="">https://logbooks.jlab.org/entry/3390218<br class=""><br class=""></blockquote><br class=""><br class="">--<br class="">=======================================================<br class="">Ken Livingston<br class=""><br class="">Dept. of Physics & Astronomy, Tel: +44 141 330 6428<br class="">University of Glasgow, Fax: +44 141 330 5889<br class="">Glasgow G12 8QQ.<br class="">Scotland. UK.<br class="">=======================================================<br class="">_______________________________________________<br class="">Halld-tagger mailing list<br class=""><a href="mailto:Halld-tagger@jlab.org" class="">Halld-tagger@jlab.org</a><br class="">https://mailman.jlab.org/mailman/listinfo/halld-tagger<br class=""></blockquote><br class=""><br class="">_______________________________________________<br class="">Halld-tagger mailing list<br class=""><a href="mailto:Halld-tagger@jlab.org" class="">Halld-tagger@jlab.org</a><br class="">https://mailman.jlab.org/mailman/listinfo/halld-tagger<br class=""></blockquote><br class=""><br class="">_______________________________________________<br class="">Halld-tagger mailing list<br class=""><a href="mailto:Halld-tagger@jlab.org" class="">Halld-tagger@jlab.org</a><br class="">https://mailman.jlab.org/mailman/listinfo/halld-tagger<br class=""></div></div></blockquote></div><br class=""></div></body></html>