{"action":"created","issue":{"url":"https://api.github.com/repos/XENON1T/pax/issues/433","repository_url":"https://api.github.com/repos/XENON1T/pax","labels_url":"https://api.github.com/repos/XENON1T/pax/issues/433/labels{/name}","comments_url":"https://api.github.com/repos/XENON1T/pax/issues/433/comments","events_url":"https://api.github.com/repos/XENON1T/pax/issues/433/events","html_url":"https://github.com/XENON1T/pax/issues/433","id":182310676,"number":433,"title":"Hitfinder integration bound setting may lead to biased hit areas","user":{"login":"JelleAalbers","id":4354311,"avatar_url":"https://avatars.githubusercontent.com/u/4354311?v=3","gravatar_id":"","url":"https://api.github.com/users/JelleAalbers","html_url":"https://github.com/JelleAalbers","followers_url":"https://api.github.com/users/JelleAalbers/followers","following_url":"https://api.github.com/users/JelleAalbers/following{/other_user}","gists_url":"https://api.github.com/users/JelleAalbers/gists{/gist_id}","starred_url":"https://api.github.com/users/JelleAalbers/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/JelleAalbers/subscriptions","organizations_url":"https://api.github.com/users/JelleAalbers/orgs","repos_url":"https://api.github.com/users/JelleAalbers/repos","events_url":"https://api.github.com/users/JelleAalbers/events{/privacy}","received_events_url":"https://api.github.com/users/JelleAalbers/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":0,"created_at":"2016-10-11T16:24:27Z","updated_at":"2016-10-11T16:57:56Z","closed_at":null,"body":"We currently stop integrating the hit when it reaches the level of 2x the noise. This introduces a bias to smaller hit areas. I introduced this on purpose in https://github.com/XENON1T/pax/pull/369 to avoid the high variance introduced by integrating to 0 or 1x the noise.\r\n\r\nHowever, it seems the bias in area may be larger than I thought. Here's what I got today looking at single electrons in run 3410 (from last Thursday):\r\n\r\n![hit_area_bias](https://cloud.githubusercontent.com/assets/4354311/19278755/cec29eec-8fde-11e6-9324-c0c4f21394de.png)\r\n\r\nSo the average area per hit is 0.85 pe... while there should be several other effects to push it higher than 1 pe:\r\n * Double photoelectron emission\r\n * Photoelectron detection efficiency (self-trigger and hitfinder) is worse for small pulses\r\n * Pile-up of several photons into a single hit (although this is somewhat unlikely given how sparse single electrons are)\r\n\r\nWe shouldn't have such a large bias in the hit areas: it will introduce nonlinearities in our S1 and especially S2 scale. For example, a big and shallow S2 will have most of its photons sitting on top of each other, so the integration length bias is negligible. Not so for a small and deep S2. \r\n\r\nInstead of fiddling around with the 'low threshold' that determines the integration length, we could have a look at changing the integration algorithm altogether, e.g. to use a fixed integration length around excursions above the threshold. Payam made a study of this in this note: https://xecluster.lngs.infn.it/dokuwiki/doku.php?id=xenon:xenon1t:cal:led:integration_length"},"comment":{"url":"https://api.github.com/repos/XENON1T/pax/issues/comments/252977786","html_url":"https://github.com/XENON1T/pax/issues/433#issuecomment-252977786","issue_url":"https://api.github.com/repos/XENON1T/pax/issues/433","id":252977786,"user":{"login":"tunnell","id":2406627,"avatar_url":"https://avatars.githubusercontent.com/u/2406627?v=3","gravatar_id":"","url":"https://api.github.com/users/tunnell","html_url":"https://github.com/tunnell","followers_url":"https://api.github.com/users/tunnell/followers","following_url":"https://api.github.com/users/tunnell/following{/other_user}","gists_url":"https://api.github.com/users/tunnell/gists{/gist_id}","starred_url":"https://api.github.com/users/tunnell/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/tunnell/subscriptions","organizations_url":"https://api.github.com/users/tunnell/orgs","repos_url":"https://api.github.com/users/tunnell/repos","events_url":"https://api.github.com/users/tunnell/events{/privacy}","received_events_url":"https://api.github.com/users/tunnell/received_events","type":"User","site_admin":false},"created_at":"2016-10-11T16:57:55Z","updated_at":"2016-10-11T16:57:55Z","body":"This is similar to what @ershockley has been studying.  @richardsaldanha do you have any thoughts here?  "}}
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