SMuK 2023 – scientific programme

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T: Fachverband Teilchenphysik

T 21: Si-Strips/CMS, Pixel/Sensor

T 21.5: Talk

Monday, March 20, 2023, 17:30–17:45, WIL/C307

Study of diffusion in small pixel sensors — •Amala Augusthy¹, Daniel Pitzl², Erika Garutti¹, Jörn Schwandt¹, and Tilman Rohe³ — ¹Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Deutschland — ²Deutsches Elektronen-Synchrotron, Notkestraße 85, 22607 Hamburg, Deutschland — ³Paul Scherrer Institute, 5232 Villigen PSI, Switzerland

Pixel sensors are widely used in the CMS experiment for tracking. From 2025 to 2027, the LHC will undergo the high luminosity upgrade where the beam luminosity will be increased to about 7.5 x 10³⁴ cm ⁻² s⁻¹ . To maintain high tracking efficiencies under such an extreme radiation environment, pixel sensors of smaller pitches will be used for tracking. However, as the pixel pitch is reduced, charge sharing effects like diffusion start to play an important role in determining the resolution of these sensors.

To investigate the effects of diffusion, measurements were performed on non-irradiated pixel sensors of sizes 50 x 50 µ m² , 25 x 100 µ m² and 17 x 150 µ m² using 5.2 GeV electron beam at the DESY test beam facility. These sensors have a thickness of 285 µ m and are bump bonded to low noise read-out chip ROC4SENS. From these measurements, the spatial resolution, cluster size and efficiency as a function of sensor bias and incidence angle of the beam were extracted. These results are then compared to simulation. The simulations were performed using PIXELAV and Synopsys TCAD. In this talk, the results of these measurements will be presented.