<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">What follows is an email from Jin explaining some things about BigBite, its optics, its classes, etc, as well as Transversity's general approach to the BigBite optics. I think it's of fairly general interest. Enjoy!<br><div apple-content-edited="true"> <span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: 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><br></div><div>Best,</div><div>Diana</div></span> </div><div><br><div>Begin forwarded message:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" color="#000000" style="font: 12.0px Helvetica; color: #000000"><b>From: </b></font><font face="Helvetica" size="3" style="font: 12.0px Helvetica">"Jin Huang" <<a href="mailto:jinhuang@jlab.org">jinhuang@jlab.org</a>></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" color="#000000" style="font: 12.0px Helvetica; color: #000000"><b>Date: </b></font><font face="Helvetica" size="3" style="font: 12.0px Helvetica">September 2, 2010 12:51:45 PM PDT</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" color="#000000" style="font: 12.0px Helvetica; color: #000000"><b>To: </b></font><font face="Helvetica" size="3" style="font: 12.0px Helvetica">"'Diana Parno'" <<a href="mailto:dparno@cmu.edu">dparno@cmu.edu</a>></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" color="#000000" style="font: 12.0px Helvetica; color: #000000"><b>Subject: </b></font><font face="Helvetica" size="3" style="font: 12.0px Helvetica"><b>RE: Couple of BigBite questions</b></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" color="#000000" style="font: 12.0px Helvetica; color: #000000"><b>Reply-To: </b></font><font face="Helvetica" size="3" style="font: 12.0px Helvetica"><<a href="mailto:jinhuang@jlab.org">jinhuang@jlab.org</a>></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div> </div><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: 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; font-size: medium; "><div lang="ZH-CN" link="blue" vlink="purple"><div class="WordSection1" style="page: WordSection1; "><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">Hi, Diana,<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">There is no convention on definition of central ray on Bigbite. Therefore, each people are free to define his/her own version. But, once defined, the replay code and its interpretation have to follow it.<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">THaGoldenTrack is an obsolete code which select the first track of a general spectrometer. Therefore, it will work with both Bigbite (no matter which optics module mounted) and HRS. It's only useful for online analysis to simplify multitrack drawing. However, in sense of off line analysis, just forget about it, otherwise analysis could be biased to first track.<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">BTW, THaOpticsE06010 database is fit at 30Degree Transversity setting. You might want to recalibrate/make sure it works for d2n too.<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">Similar thing for THaPrimaryKine. It usually take track information from THaGoldenTrack. Then it only process the first track. During Transversity analysis, we built a code to work on replayed root file and calculate kinematics based on raw spectrometer output, ex, BB.tr.px[]. Then the kinematics variables, which are calculated for each track, are merged back into root files. I do suggest you do same for d2n. You can cross check the calculation code by comparing first track kinematics to those generated by THaPrimaryKine.<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">Spectrometer angle are supposed to be read into THaBigbite through run database file, ie, db_run.dat. The code trace back to<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><a href="http://hallaweb.jlab.org/root/doc/html_v15/src/THaSpectrometer.cxx.html#gcCzfE" style="color: blue; text-decoration: underline; ">http://hallaweb.jlab.org/root/doc/html_v15/src/THaSpectrometer.cxx.html#gcCzfE</a><o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">However THaOpticsE06010 is special. It is not designed by Xin for general purpose Hall A spectrometer but for Transversity setup only. It overloaded the spectrometer angle through sieve_angle variable in db_BB.optics.dat. As I understand, the 3<sup>rd</sup><span class="Apple-converted-space"> </span>variable is the angle in rad. You might want talk to Xin for details. He used some of his own definition in the code, for ex. th_tg and ph_tg is inversed relative to HRS convension. But, again, since we interpreted the variables accordingly, THaOpticsE06010 worked well for Transversity.<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">Glad to know you</span><span lang="EN-US" style="font-family: 'Courier New'; ">’</span><span lang="EN-US">ve settled down at Seattle. As you can see, I have been traveled a lot this summer. But I enjoyed it too :-P<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">Cheers,<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">Jin<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">-----Original Message-----<br>From: Diana Parno [<a href="mailto:dparno@cmu.edu" style="color: blue; text-decoration: underline; ">mailto:dparno@cmu.edu</a>]<span class="Apple-converted-space"> </span><br>Sent: Tuesday, August 31, 2010 2:40 PM<br>To:<span class="Apple-converted-space"> </span><a href="mailto:jinhuang@jlab.org" style="color: blue; text-decoration: underline; ">jinhuang@jlab.org</a><br>Subject: Couple of BigBite questions<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">Hi Jin,<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">I'm working through the BigBite kinematics and wondering if you can help me understand a few things. I've attached a copy of a replay file in case it's a help. Here are my questions:<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">- Do you know how the BigBite central ray is defined? That is, is it the angle between the center of the magnet; the center of the first chamber; or what?<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">- In the attached file, I mount the THaOpticsE06010 class. Do you know if the THaGoldenTrack class uses this class, since it's the mounted optics? Matt is under the impression the THaGoldenTrack variables use some outdated optics class, but I'm not sure how that could happen unless I'm missing something obvious in the code. If THaGoldenTrack does use some other class, how can it be induced to use THaOpticsE06010?<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">- The THaPrimaryKine class seems to generate one number per entry in the tree. Which track does it choose when there is more than one track? I am under the impression, from some comments in the code, that it uses the golden track, but I want to double check.<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">- Do you know where the spectrometer angle is encoded for BigBite? <o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">(This is the angle of the central ray; it was 30 degrees during Transversity and 45 degrees during d2n.) Somewhere in the optics or spectrometer classes, this must come into play so that the momentum vectors can be transformed into Hall A coordinates. I found some (probably outdated) documentation implying that it's in db_run.dat; I found a few lines about the chamber position in the db_BB.optics.dat file, from which a spectrometer angle could be extracted.<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">Other than that, I've moved to Seattle and am mostly settled in, although there are still way too many boxes! Today's the first real rainy day in a while. I hope you're settled in back in Boston and doing well there.<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US"><o:p> </o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">Best,<o:p></o:p></span></div><div style="margin-top: 0cm; margin-right: 0cm; margin-bottom: 0.0001pt; margin-left: 0cm; font-size: 10.5pt; font-family: Calibri, sans-serif; "><span lang="EN-US">Diana<o:p></o:p></span></div></div></div></span></blockquote></div><br></body></html>