Measurements of beam backgrounds in SuperKEKB Phase 2

Zachary J. Liptak , Antonio Paladino , Luka Santelj , Jeffery Schueler , Slavomira Stefkova , Hikaru Tanigawa , Noritsugu Tsuzuki , Alberto Aloisio , Patrick Ahlburg , Philip Bambade (1) , Giovanni Bassi , Matthew Barrett , Jerome Baudot (2) , Thomas Browder , Giulia Casarosa , Giuseppe Cautero , David Cinabro , Gilles Claus (2) , Daniel Cuesta (2) , Francesco Di Capua , Salvatore Di Carlo (1) , John Flanagan , Ariane Frey , Bryan Fulsom , Yoshihiro Funakoshi , Miroslav Gabriel , Raffaele Girodano , Dario Giuressi , Mathieu Goffe (2) , Koji Hara , Oskar Hartbrich , Michael Hedges , Daniel Heuchel , Naoko Iida , Takuya Ishibashi , Kimmo Jaaskelainen (2) , Didier Jehanno (1) , Samuel de Johng , Thomas Kraetzschmar , Chiara La Licata , Livio Lanceri , Philipp Leitl , Peter Lewis , Carlos Marinas , Caleb Miller , Katsuro Nakamura , Hiroyuki Nakayama , Carsten Niebuhr , Yoshiyuki Onuki , Chengguo Pang (1) , Botho Paschen , Isabelle Ripp-Baudot (2) , Giuliana Rizzo , J. Michael Roney , Harrison Schreeck , Benjamin Schwenker , Frank Simon , Matthieu Specht (2) , Bjoern Spruck , Yuri Soloviev , Michal Szelezniak (2) , Shuji Tanaka , Shinji Terui , Gennaro Tortone , Tohru Tsuboyama , Yuma Uematsu , Sven Einar Vahsen , Lorenzo Vitale , Hendrik Windel

1 IJCLab - Laboratoire de Physique des 2 Infinis Irène Joliot-Curie
2 IPHC - Institut Pluridisciplinaire Hubert Curien

The high design luminosity of the SuperKEKB electron–positron collider will result in challenging levels of beam-induced backgrounds in the interaction region. Understanding and mitigating these backgrounds is critical to the success of the Belle II experiment. We report on the first background measurements performed after roll-in of the Belle II detector, a period known as SuperKEKB Phase 2, utilizing both the BEAST II system of dedicated background detectors and the Belle II detector itself. We also report on first revisions to the background simulation made in response to our findings. Backgrounds measured include contributions from synchrotron radiation, beam-gas, Touschek, and injection backgrounds. At the end of Phase 2, single-beam backgrounds originating from the 4 GeV positron Low Energy Ring (LER) agree reasonably well with simulation, while backgrounds from the 7 GeV electron High Energy Ring (HER) are approximately one order of magnitude higher than simulation. We extrapolate these backgrounds forward and conclude it is safe to install the Belle II vertex detector.

Mots clés: Beam background; Accelerator background; Belle II; SuperKEKB; activity report; beam: background; BELLE; synchrotron radiation; vertex detector; numerical calculations

Domaines: Instrumentations et Détecteurs [physics.ins-det]; Physique des Hautes Energies - Expérience [hep-ex]

Zachary J. Liptak, Antonio Paladino, Luka Santelj, Jeffery Schueler, Slavomira Stefkova, et al.. Measurements of beam backgrounds in SuperKEKB Phase 2. Nucl.Instrum.Meth.A, 2022, 1040, pp.167168. ⟨10.1016/j.nima.2022.167168⟩. ⟨hal-03524122⟩