Level 3 Missing Transverse Energy Tool
Contact: Vesna Cuplov (Purdue University Calumet)Vesna Cuplov
Missing Transverse Energy Definition
Protons and anti-protons colliding at the Tevatron have equal and opposite momenta. Therefore, the total vecor momentum sum in an event should be zero.
But, the hard-scatter interactions occur between the partons of the proton and anti-proton. These partons share the total momentum of the proton or anti-proton and are not constrained to any particular momentum value. Partons tend to carry very little momentum in the plane transverse to the beam path. To a good approximation, the Transverse Momentum can be considered as a conserved quantity.
Missing Transverse Energy without ICD cells
The Inter Cryostat Detector (ICD) in D0 is located between the Central Calorimeter and the End-Cap Calorimeter. The ICD coverage is 1.1 < |η| < 1.4.
The new Level 3 MET tool has been implemented (M. Verzocchi). The new tool posseses a parameter UseMEt_noICD, which you can use in your trigger list. The following table gives the correspondance between the UseMEt_noICD parameter and the Level3 Missing Et calculation:
| UseMEt_noICD =
|
|---|
| 0 | 1
|
|---|
| MET calculated using: | All cells | No ICD cells
|
|---|
Comparison study between Level3 and Offline MEt
The Offline MEt was calculated following the method used by the Wmass group (/d0dist/dist/packages/wmass_analysis/devel/src/MetSelector.cpp). This is the latest version that might differ slightely with what was done at the time of this comparison study. Energies are measured from Electro-magnetic layers (1-7), Massless gap layers (8 and 10) and Fine Hadronic layers (11-14). Electro-magnetic corrections are applied on Electro-magnetic clusters.
The following piece of code shows what was used at the time of these studies (may 2007).
What sample was used?
A SAM Definition name was created on 05.08.07 EMinclusive_and_run_starting_231960
sam create definition --dim ="(((APPL_NAME tmb_analyze and (VERSION csg-p21.05.00 or VERSION csg-p21.05.00a)) and DATA_TIER root-tree-bygroup) and SKIM.NAME eminclusive) and RUN_NUMBER >=231960)
Which trigger was principally used for this study? E1_SHT25
L1 requires Calorimeter EM objects with ET>12 GeV and Veto on cal_unsuppressed condition
L2 requires the sum of the two highest EM towers to be >= 15 GeV
L3 trigger bit set to true if an electron is found satisfying tight shower shape requirements with ET>25 GeV
Which cuts were applied on the sample?
The sample obtained after these cuts is made of ~ 20 000 "W-like events".
The following table shows the behaviour of the MET no ICD cells cut on our sample of "W-like events" after an offline cut on the MET of 25 GeV:
Efficiency plots |
Vesna Cuplov
Last modified: Wed Dec 5 17:15:22 CDT 2007