Charge Symmetric Background
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This page is considered done. It been reviewed by Caro. There may be missing elements, but they are all flagged and the text has no errors. |
Intro
This is a correction done in many analyses that corrects for the case when the lepton detected and used as the DIS lepton is not in fact the beam lepton but is from another source. Those charge symmetric processes are meson Dalitz decays or photon conversion into Fehler beim Parsen (MathML mit SVG- oder PNG-Rückgriff (empfohlen für moderne Browser und Barrierefreiheitswerkzeuge): Ungültige Antwort („Math extension cannot connect to Restbase.“) von Server „https://wikimedia.org/api/rest_v1/“:): {\displaystyle e^+e^-} pairs. Since these and Fehler beim Parsen (MathML mit SVG- oder PNG-Rückgriff (empfohlen für moderne Browser und Barrierefreiheitswerkzeuge): Ungültige Antwort („Math extension cannot connect to Restbase.“) von Server „https://wikimedia.org/api/rest_v1/“:): {\displaystyle e^-} originate from secondary processes, they typically have lower momenta and are thus concentrated at higher Fehler beim Parsen (MathML mit SVG- oder PNG-Rückgriff (empfohlen für moderne Browser und Barrierefreiheitswerkzeuge): Ungültige Antwort („Math extension cannot connect to Restbase.“) von Server „https://wikimedia.org/api/rest_v1/“:): {\displaystyle y} .
Essentials
The trick is that the sources of non-beam leptons are symmetric in lepton charge, so for every time you find a lepton that is not from the beam you should also have a corresponding event where the lepton is oppositely charged - that is, not matching the charge of the beam.
To do this correction people chose DIS events based on the highest momentum lepton in the event. Often people make a cut on the minimum lepton energy of something like 4GeV. The charge of the lepton (the sign of the momentum) is not checked initially, but events with the wrong lepton charge are given a negative weight. This is done so that these events can effectively "subtract" the events where the non-DIS lepton was of the correct charge:
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I.e. in each bin Fehler beim Parsen (MathML mit SVG- oder PNG-Rückgriff (empfohlen für moderne Browser und Barrierefreiheitswerkzeuge): Ungültige Antwort („Math extension cannot connect to Restbase.“) von Server „https://wikimedia.org/api/rest_v1/“:): {\displaystyle i}
, the number of collected charge symmetric events (leptons with charge opposite to the beam charge), Fehler beim Parsen (Konvertierungsfehler. Der Server („https://wikimedia.org/api/rest_“) hat berichtet: „Cannot get mml. Server problem.“): {\displaystyle N_{\mathrm {cs} }(i)}
, is subtracted from the collected events with leptons with the correct charge (candidates), Fehler beim Parsen (MathML mit SVG- oder PNG-Rückgriff (empfohlen für moderne Browser und Barrierefreiheitswerkzeuge): Ungültige Antwort („Math extension cannot connect to Restbase.“) von Server „https://wikimedia.org/api/rest_v1/“:): {\displaystyle N_{\mathrm{cand}}(i)}
, and the real DIS counts are obtained: Fehler beim Parsen (MathML mit SVG- oder PNG-Rückgriff (empfohlen für moderne Browser und Barrierefreiheitswerkzeuge): Ungültige Antwort („Math extension cannot connect to Restbase.“) von Server „https://wikimedia.org/api/rest_v1/“:): {\displaystyle N(i)}
.
