Abstract
The LHCb experiment will record an unprecedented dataset of beauty and charm hadron decays during Run II of the LHC, set to take place between 2015 and 2018. A key computing challenge is to store and process this data, which limits the maximum output rate of the LHCb trigger. So far, LHCb has written out a few kHz of events containing the full raw sub-detector data, which are passed through a full offline event reconstruction before being considered for physics analysis. Charm physics in particular is limited by trigger output rate constraints. A new streaming strategy includes the possibility to perform the physics analysis with candidates reconstructed in the trigger, thus bypassing the offline reconstruction. In the Turbo stream the trigger will write out a compact summary of physics objects containing all information necessary for analyses. This will allow an increased output rate and thus higher average efficiencies and smaller selection biases. This idea will be commissioned and developed during 2015 with a selection of physics analyses. It is anticipated that the turbo stream will be adopted by an increasing number of analyses during the remainder of LHC Run II (2015–2018) and ultimately in Run III (starting in 2020) with the upgraded LHCb detector.
Highlights
The LHCb detector [1, 2] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks
The online event selection is performed by a trigger [3] consisting of a hardware stage, the L0, which reduces the event rate to 1 MHz from the input collision rate of at most 30 MHz based on information from the calorimeter and muon systems, followed by a software stage, the HLT, that runs in the LHCb Event Filter Farm (EFF) and gave a final rate of 5 kHz in Run I
To increase CPU efficiency, in 2012 each EFF node was equipped with 1 TB of local storage space, and during data taking 20 % of the L0 output was buffered in order to run the software stage during LHC downtime
Summary
The LHCb detector [1, 2] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks. The online event selection is performed by a trigger [3] consisting of a hardware stage, the L0, which reduces the event rate to 1 MHz from the input collision rate of at most 30 MHz based on information from the calorimeter and muon systems, followed by a software stage, the HLT, that runs in the LHCb Event Filter Farm (EFF) and gave a final rate of 5 kHz in Run I. This software trigger is divided into two steps, HLT1 and HLT2, that perform a partial and full event reconstruction, respectively.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
