The sPHENIX Data Acquisition System - the Experiment's first Run in 2023

By the time of this workshop, the sPHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) will have completed its first data taking run, which has started in the second half of May. The experiment saw its very first collisions on May 18, 2023. sPHENIX is the first major upgrade to a Nuclear Physics experiment in the US in 2 decades, and will take data until the RHIC era ends with the start of the construction of the Electron-Ion Colllider.

The Data Acquisition System of sPHENIX is designed for event rates of 15 KHz. The largest data volume is produced by the tracking system, consisting of a Monolithic-active-pixel Vertex Detector (MVTX), an Intermediate Tracker (INTT), and the Time Projection Chamber (TPC). In order to achieve the design event rate, the entire tracking system will be read out in continuous, or streaming mode. The resulting continuously sampled signals from the tracking system must then be processed and correlated with the actually triggered data from the calorimeter system. Due to budget constraints, it was not possible to upgrade the entire readout, including the calorimeter systems, to a streaming-based one. However, by operating the entire tracking system in streaming mode, it will be possible to acquire tracking data without the calorimeters at a faster rate, which will benefit our heavy-flavor physics program under most running conditions.

At the time of this writing, we have commissioned the major parts of the data acquisition system, such as most readout systems for the various detector components, the Timing System, and most of the hardware of the Local-Level-1 Trigger system, and are now commissioning the detectors with beam. During the current commissioning phase we already routinely use physics-type signals, such as π⁰ invariant mass spectra and detector correlation plots, to evaluate the detector performance and calibrations.

We will give an overview of the sPHENIX experiment, its detector systems and their readout, and present the performance during data taking, the achieved statistics, and especially the state of combining the streaming readout of the tracking detectors with the triggered readout of the calorimeters and the Minimum-Bias Detector.