The April Global Run (AGR), the first commissioning run in 2014, took place 7-11 April. After a couple of weeks of chewing on the data (and the Easter holidays), a “Data Analysis Jamboree” was held on 29 April (https://indico.cern.ch/event/315825/) where detailed analyses were presented by the Strips, ECAL, HCAL, DT, RPC, and CSC, highlighting the lessons learned in the AGR.

The Strips uncovered a bug that occurred during the transition from 32-bit to 64-bit libraries in the online computers that resulted in incorrect calibration constants being loaded to the online database. In a short run following the AGR, they were able to confirm that the signal-to-noise ratio when running at –15°C is as good as when running at +4°C. They also exercised the Prompt Calibration Loop to define dead channels. The ECAL collected transparency data over the full detector for the first time since the Global Run In November. The HCAL showed initial efficiency measurements for MIPs from the HO SiPMs, qualified their new QPLLs for operation with the clock scan, and demonstrated that their HPDs show no unusual noise.

For the muon systems, the response of the detector to cosmic rays was demonstrated to be nearly identical to the 2015 detector in several aspects. In short, after the huge amount of work by all subsystems, cosmic rays still look like cosmic rays! With all of the new equipment, one of the toughest tasks for the muon detectors was understanding the timing—a task which is not easy given that cosmic rays are neither synchronous nor come from the interaction region. A detailed comparison of the timing between DT and RPC indicates that there are shifts on the order of a few nanoseconds compared to 2012 data, a good starting point to perform the fine timing scan with collisions in 2015. The timing between the GMT and the RPC link boards was measured, allowing initial studies of the new RE4 chambers. Going beyond expectations, the CSCs managed to run with their new ME4/2 chambers on both endcaps, and uncovered some issues with the offline timing which are under investigation.

By Greg Rakness