Performance of electron and photon triggers in ATLAS during LHC Run 2
G. Aad, B. Abbott, D. C. Abbott, A. Abed Abud, K. Abeling, D. K. Abhayasinghe, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, Y. Abulaiti, B. S. Acharya, B. Achkar, S. Adachi, L. Adámek, C. Adam Bourdarios, L. Adamczyk, L. Adámek, J. Adelman, M. Adersberger, A. Adıgüzel, S. Adorni, T. Adye, A. A. Affolder, Y. Afik, C. Agapopoulou, M. N. Agaras, A. Aggarwal, C. Agheorghiesei, J. A. Aguilar–Saavedra, F. Ahmadov, W. S. Ahmed, X. Ai, G. Aielli, S. Akatsuka, T. P. A. Åkesson, E. Akilli, A. V. Akimov, K. Al Khoury, G. L. Alberghi, J. Albert, M. J. Alconada Verzini, S. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, T. Alexopoulos, A. Alfonsi, F. Alfonsi, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, S. P. Alkire, C. Allaire, B. M. M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, A. Alonso, F. Alonso, C. Alpigiani, A. A. Alshehri, M. Alvarez Estevez, D. Álvarez Piqueras, M. G. Alviggi, Y. Amaral Coutinho, A. Ambler, L. Ambroz, C. Amelung, D. Amidei, S. P. Amor Dos Santos, S. Amoroso, C. S. Amrouche, F. F. An, C. Anastopoulos, N. Andari, T. Andeen, C. F. Anders, J. K. Anders, A. Andreazza, V. Andrei, C. R. Anelli, S. Angelidakis, A. Angerami, A. V. Anisenkov, A. Annovi, C. Antel, M. T. Anthony, E. Antipov, M. Antonelli, D. J. A. Antrim, F. Anulli, M. Aoki, J. A. Aparisi Pozo, L. Aperio Bella, J. P. Araque, V. Araujo Ferraz, R. Araujo Pereira
Abstract
Abstract Electron and photon triggers covering transverse energies from 5 $$\text {GeV }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>GeV</mml:mtext><mml:mspace/></mml:mrow></mml:math> to several $$\text {TeV }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>TeV</mml:mtext><mml:mspace/></mml:mrow></mml:math> are essential for the ATLAS experiment to record signals for a wide variety of physics: from Standard Model processes to searches for new phenomena in both proton–proton and heavy-ion collisions. To cope with a fourfold increase of peak LHC luminosity from 2015 to 2018 (Run 2), to $$2.1 \times 10^{34}\,\hbox {cm}^{-2}\hbox { s}^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>2.1</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mn>34</mml:mn></mml:msup><mml:mspace/><mml:msup><mml:mtext>cm</mml:mtext><mml:mrow><mml:mo>-</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mspace/><mml:msup><mml:mtext>s</mml:mtext><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math> , and a similar increase in the number of interactions per beam-crossing to about 60, trigger algorithms and selections were optimised to control the rates while retaining a high efficiency for physics analyses. For proton–proton collisions, the single-electron trigger efficiency relative to a single-electron offline selection is at least 75% for an offline electron of 31 $$\text {GeV }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>GeV</mml:mtext><mml:mspace/></mml:mrow></mml:math> , and rises to 96% at 60 $$\text {GeV }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>GeV</mml:mtext><mml:mspace/></mml:mrow></mml:math> ; the trigger efficiency of a 25 $$\text {GeV }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>GeV</mml:mtext><mml:mspace/></mml:mrow></mml:math> leg of the primary diphoton trigger relative to a tight offline photon selection is more than 96% for an offline photon of 30 $$\text {GeV }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>GeV</mml:mtext><mml:mspace/></mml:mrow></mml:math> . For heavy-ion collisions, the primary electron and photon trigger efficiencies relative to the corresponding standard offline selections are at least 84% and 95%, respectively, at 5 $$\text {GeV }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>GeV</mml:mtext><mml:mspace/></mml:mrow></mml:math> above the corresponding trigger threshold.