<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class=""><br class="">The uncertainty in the energy of the photon is 0.001* E_beam (per NIM and Eugene P.) </div></blockquote><div><br class=""></div><div><br class=""></div><div>I copy and pasted from the 2007 tagger energy calibration NIM paper ():</div><div><br class=""></div><div>"In this report, we present the energy calibration of the Hall B
bremsstrahlung tagging system at the Thomas Jefferson National
Accelerator Facility. The calibration was performed using a magnetic
pair spectrometer. The tagged photon energy spectrum was measured in
coincidence with <span id="mmlsi26" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathurl="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0168900206024181&_mathId=si26.gif&_user=111111111&_pii=S0168900206024181&_rdoc=1&_issn=01689002&md5=46f56770caf09816b67f89ab1ca0c0bf" title="Click to view the MathML source">e<sup class="">+</sup>e<sup class="">-<font face="Latin Modern Math, MathJax_Main, STIXGeneral, STIXSizeOneSym, DejaVu Sans, DejaVu Serif, Cambria, Cambria Math, Lucida Sans Unicode, Arial Unicode MS, Lucida Grande, OpenSymbol, Standard Symbols L, Times, serif" class=""> </font></sup></span></span>pairs as a function of the pair spectrometer magnetic field. Taking
advantage of the internal linearity of the pair spectrometer, the energy
of the tagging system was calibrated at the level of <span id="mmlsi27" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathurl="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0168900206024181&_mathId=si27.gif&_user=111111111&_pii=S0168900206024181&_rdoc=1&_issn=01689002&md5=c14ffee7cb0a9548823d340c81e49380" title="Click to view the MathML source">±0.1%E<sub class="">γ <font face="Latin Modern Math, MathJax_Main, STIXGeneral, STIXSizeOneSym, DejaVu Sans, DejaVu Serif, Cambria, Cambria Math, Lucida Sans Unicode, Arial Unicode MS, Lucida Grande, OpenSymbol, Standard Symbols L, Times, serif" class="">. </font></sub></span></span>The absolute energy scale was determined using the <span id="mmlsi28" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathurl="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0168900206024181&_mathId=si28.gif&_user=111111111&_pii=S0168900206024181&_rdoc=1&_issn=01689002&md5=3e148de1c1eb2670d85314a754e39663" title="Click to view the MathML source">e<sup class="">+</sup>e<sup class="">-</sup></span><span class="mathContainer hidden"><span class="mathCode"><math altimg="si28.gif" overflow="scroll"><msup><mrow><mi mathvariant="normal">e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi mathvariant="normal">e</mi></mrow><mrow><mo>-</mo></mrow></msup></math></span></span></span>
rate measurements close to the end-point of the photon spectrum. The
energy variations across the full tagging range were found to be < 3MeV”</div><div><br class=""></div><div><br class=""></div><div><br class=""></div><br class=""><blockquote type="cite" class=""><div class="">The hodos were built such that this is true (different widths)<br class=""><br class="">Then consider a counter of width (energy) "a" where the (assume) energy distribution is flat: then Variance = sigma^2 = 1/a* int^a_0 E^2 dE = a^2/3<br class=""><br class="">Therefore if we distribute the uncertainty over a counter (energy bin) the variance is : sigma^2 = (0.001*E_beam)**2/3<br class=""><br class="">=Carlos<br class="">_______________________________________________<br class="">G12 mailing list<br class=""><a href="mailto:G12@jlab.org" class="">G12@jlab.org</a><br class="">https://mailman.jlab.org/mailman/listinfo/g12<br class=""></div></blockquote></div><br class=""></body></html>