CERN Accelerating science

A successful year for the LHCb collaboration

by Patrick Robbe

After the Long Shutdown of 2013 and 2014, LHCb started to take data this year and collected during this year 320 pb-1 of proton-proton collisions at the center of mass energy of 13 TeV. The detector was almost identical to the one used during Run 1, apart from maintenance and consolidation work and from the addition of a new sub-detector to extend the physics capabilities of the experiment. Namely scintillator planes were installed far from the interaction point in order to increase the angular coverage for the experiment and to study central exclusive production mechanisms in proton collisions. This new sub-detector, HERSCHEL, was successfully used and included in data taking in 2015. 

The very first collisions delivered in June by the LHC provided events to calibrate and align the detector which was quickly ready to record good data for physics analysis. The main improvement for the data acquisition prior to the start of Run 2 was the implementation of a significantly more sophisticated trigger system: the data filtered by a first level of trigger is stored on disk for few hours before being processed by the second level of trigger and sent offline for data analysis. This time is used to perform a very precise calibration of the detector, quasi simultaneous to the data taking. The result of this calibration is immediately available for the second trigger level and the data is then directly usable for physics analysis. During the summer 2015 and the intensity ramp of the LHC with 50ns spaced bunches, this technique was successfully employed for the first time, and allowed the experiment to quickly measure and publish measurements of the production cross-section of J/ψ or charm meson at the new LHC energy, in the record time of about one month after data collection.

The second part of the year helped commissioning completely these calibration and alignment procedures, which are now completely automatic. The LHCb experiment is then the first large particle physics experiment being calibrated and aligned online. The amount of data recorded in 2015 is still modest, but thanks to this achievement, and to important improvements of the software trigger algorithms, the experiment is well prepared to collect efficiently the large amount of data that will be delivered in Run 2. The operation of the detectors was extremely smooth and stable, and no major intervention is foreseen during the winter stop. 

In addition to the standard proton-proton data taking, new configurations were explored this year with the LHCb detector. For the first time, the experiment recorded heavy ion collisions, also with a very efficient detector operation. For the first time also, the detector collected beam-gas collisions for the proton or lead LHC beam with a gas injected directly in the interaction point. This setup was prepared with the help of the LHC vacuum group and Neon, Helium and Argon gases were successively injected. The data collected will help studying a variety of interesting effects: production of anti-protons, cold nuclear effects or formation of quark-gluon plasma.  

at the center of mass energy of 13 TeV. The detector was almost identical to the one used during Run 1, apart from maintenance and consolidation work and from the addition of a new sub-detector to extend the physics capabilities of the experiment. Namely scintillator planes were installed far from the interaction point in order to increase the angular coverage for the experiment and to study central exclusive production mechanisms in proton collisions. This new sub-detector, HERSCHEL, was successfully used and included in data taking in 2015. 

The very first collisions delivered in June by the LHC provided events to calibrate and align the detector which was quickly ready to record good data for physics analysis. The main improvement for the data acquisition prior to the start of Run 2 was the implementation of a significantly more sophisticated trigger system: the data filtered by a first level of trigger is stored on disk for few hours before being processed by the second level of trigger and sent offline for data analysis. This time is used to perform a very precise calibration of the detector, quasi simultaneous to the data taking. The result of this calibration is immediately available for the second trigger level and the data is then directly usable for physics analysis. During the summer 2015 and the intensity ramp of the LHC with 50ns spaced bunches, this technique was successfully employed for the first time, and allowed the experiment to quickly measure and publish measurements of the production cross-section of J/ψ or charm meson at the new LHC energy, in the record time of about one month after data collection.

The second part of the year helped commissioning completely these calibration and alignment procedures, which are now completely automatic. The LHCb experiment is then the first large particle physics experiment being calibrated and aligned online. The amount of data recorded in 2015 is still modest, but thanks to this achievement, and to important improvements of the software trigger algorithms, the experiment is well prepared to collect efficiently the large amount of data that will be delivered in Run 2. The operation of the detectors was extremely smooth and stable, and no major intervention is foreseen during the winter stop. 

In addition to the standard proton-proton data taking, new configurations were explored this year with the LHCb detector. For the first time, the experiment recorded heavy ion collisions, also with a very efficient detector operation. For the first time also, the detector collected beam-gas collisions for the proton or lead LHC beam with a gas injected directly in the interaction point. This setup was prepared with the help of the LHC vacuum group and Neon, Helium and Argon gases were successively injected. The data collected will help studying a variety of interesting effects: production of anti-protons, cold nuclear effects or formation of quark-gluon plasma.  

 
 
 
 
 
 
 
 
 
 
 
 
 
 

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