Physics at 13 TeV: LHCb - a new data-processing strategy
Originally, the LHCb detector was designed for operation with moderate luminosity and low pile-up. However, in 2010, the collaboration opted for “luminosity levelling”, a novel solution which allows the experiment to adapt automatically to normal variations in luminosity which occur during an LHC run.
In this way, the detector operates optimally at all times. “For the second LHC run, we will have to redefine the luminosity, to adapt to the conditions at the new energy of 13 TeV,” explains Patrick Koppenburg, physics coordinator of the LHCb collaboration. “However, the most important experimental challenge for us will be the new trigger system.”
The trigger rapidly sorts the most interesting data from the data that can be discarded without a significant loss of information. The zero-level (i.e. the first level) trigger system of LHCb “only” lets through one sixteenth of the initial data, but even that is too much to be stored permanently. “During the first run, the data which got through the zero-level trigger was treated using the algorithms Hlt1 and Hlt2, almost in real-time,” says Patrick Koppenburg. “Then we observed that on certain crucial parameters such as lifetime acceptance, differences started appearing between the values of the trigger system and those calculated after analysis. So from January 2015, we will temporarily store to disk all the data filtered by Hlt1. Then, we'll run Hlt2 on the data after having calibrated the detector. This procedure will enable us to eliminate most discrepancies at source, as the reconstruction of the data will be the same in the trigger system as in the final analysis.”
The expectations of the LHCb collaboration for the second LHC run are focused on two topics: “In the first months, running at low luminosity, we'll do cross-section measurements at 13 TeV of the production of charm, the B particle, and the Z and W particles and, more generally, we’ll measure the charged forward multiplicity,” Patrick Koppenburg concludes. “Then we will continue to accumulate statistical data for our precision studies of b and charm physics.”
Check out more of our Physics at 13 TeV series in "ALICE - scratching under the surface" and "TOTEM - a new era of collaboration with CMS". For a theory perspective on the next run, read "Life is Good at 13 TeV".
