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<p class="MsoNormal">Hello all, </p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">As you may remember, we saw that GEM layers 1 and 3 in BigBite exhibited significantly wider timing distributions during GMN (and GEN), even for the good signals. Recently, for the first time, I tried to get a closer look at the uniformity
(or lack thereof) of the signal timing for the GEMs, with some interesting findings. I wanted to solicit the opinions of the GEM hardware experts to see if this is something that has been seen before, and if the pattern has a simple explanation, what the physical
mechanism might be, and whether it could be mitigated in the future.</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The first picture shows the average signal timing (U+V)/2 on the x axis for the five BigBite GEM layers versus global “x” position of the hit on the y axis. As we can see, in UV layers 0 and 2, the timing is relatively uniform as a function
of vertical hit position, whereas for layers 1 and 3, there is a significant correlation that follows a similar x dependence. Layer 4 also exhibits an x dependence qualitatively similar to layers 1 and 3 but the magnitude is smaller compared to the resolution.
Also, in all cases the width of the good timing peak for layers 1 and 3 is wider (~10 ns) compared to layers 0, 2, and 4 (~6-7 ns), even after accounting for the non-uniformity versus position. The second attachment shows the correlation with the y-coordinate.
Here layers 1 and 3 still show a fairly significant correlation while layers 0, 2, and 4 show almost no correlation.
</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">While this is something we can in principle measure and correct for if we want to apply tighter timing cuts in the analysis, I would love to hear people’s ideas for what is happening here. Thoughts?</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Best regards,</p>
<p class="MsoNormal">Andrew</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="mso-ligatures:none"><img width="2113" height="1207" style="width:22.0104in;height:12.5729in" id="Picture_x0020_1" src="cid:image001.png@01D97925.2DE4CAE0"></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none"><img width="2113" height="1207" style="width:22.0104in;height:12.5729in" id="Picture_x0020_2" src="cid:image002.png@01D97926.17335AE0"></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Century",serif;color:black;mso-ligatures:none">Andrew Puckett<br>
Associate Professor, Physics Department<br>
University of Connecticut<br>
196 Auditorium Road, Unit 3046<br>
Storrs, CT 06269-3046<br>
Office phone: (860) 486-7137<br>
</span><a href="https://puckett.physics.uconn.edu" title="https://puckett.physics.uconn.edu"><span style="font-size:12.0pt;font-family:"Century",serif;mso-ligatures:none">https://puckett.physics.uconn.edu</span></a><span style="font-size:12.0pt;font-family:"Century",serif;color:black;mso-ligatures:none"><br>
</span><a href="mailto:andrew.puckett@uconn.edu"><span style="font-size:12.0pt;font-family:"Century",serif;mso-ligatures:none">puckett@jlab.org</span></a></p>
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