In the ATLAS detector hadronic calorimeters will cover the region down
to || = 4.9 .
Details on the calorimeter design can be found in
section 4.3. The tag jets will have a
transverse momentum of the order of mW/2 . In
table 8.3 the effect of requiring either one or two
tag jets is shown. The jets are required to have
2.5 < || < 5.0 and
to be in opposite forward regions for the two jet case.
|ET cut||Efficiency 1 tag jet (%)||Efficiency 2 tag jets (%)|
|(GeV)||H W +W -||jj||H W +W -||jj|
|15||85.7 0.7||34.2 0.6||36.7 0.4||0.37 0.02|
|20||82.0 0.7||28.8 0.6||31.5 0.4||0.25 0.02|
|30||71.8 0.6||1.96 0.04||20.6 0.3||0.12 0.01|
|50||49.3 0.5||1.09 0.04||8.2 0.2||0.04 0.01|
The probability p for a single tag jet in the forward or the backward direction of the detector is the same. If the two tag jets in double tag events are uncorrelated the probability for a double tag is p 2 while the probability for a single tag, in either the forward or the backward direction, is 1 - (1 - p)2 and not p as a would be the naïve expectation.
From the tag jet efficiencies for single and double tag jets listed in table 8.3 it is seen that the Higgs events have uncorrelated tag jets while the QCD-jet events show a positive correlation. The Higgs events have uncorrelated tag jets since the quarks emitting the vector bosons are uncorrelated (see fig. 8.6).