Trigger - Miscellaneous Information
LHC beam information:
- ring circumference: 26.66 km
- proton beams energy: 7 TeV
- number of buckets: 3564
- number of filled buckets: 2808
- number of crossings with both buckets filled with protons: 2622 (depends on the structure of the filled/empty buckets)
- bucket crossing rate (frequency): 3564 x c / 26.66 km = 40.08 MHz
- (average) instantaneous luminosity at the LHCb interaction point:
L = 2 x 1032cm-2s-1
- luminosity's time evolution: exponential decrease with
- lifetime τ = 10 hours
- duration of machine fills T = 7 hours
- maximal L @ start of fills:
L(0) = L δ / (1-e-δ) = 2.8 x 1032cm-2s-1
(δ = T / τ)
- annual integrated luminosity: Lintyear = 2 fb-1, assuming 1 nominal year = 107 seconds of data-taking running
pp cross sections (from Pythia 6.205):
Results at a centre-of-mass energy of 14 TeV.
- total: σtot = 102.4 mb
- inelastic: σinel = 80 mb
- elastic: σel ~ 22.2 mb
- diffractive: σdiff ~ 24 mb
- hard QCD: σhard ~ 56 mb
- bb-production:
σbb = 500 μb
Calculation of trigger rates:
- rate of filled bunches crossing:
Rfilled = (40.08 MHz) x (2622/3564) = 29.49 MHz
- average number of interactions in Rfilled MHz:
<Nint> = L x σtot / Rfilled = 0.695
- probability of at least 1 interaction:
P>0 = 1 - exp(-<Nint>) = 0.5
- rate with at least 1 interaction:
R>0 = P>0 x Rfilled = 14.745 MHz
- fraction of L0-accepted events to achieve a L0 output rate of 1 MHz:
(1 MHz) / R>0 x 100 = 6.78%
