Physics After Alignment

Physics applications of the ID alignment

CSC Analysis

Analysis with our own ntuple

Test on Z-->mu+mu- events

Using iPatRec as Tracker and plots from our own ntuple:

• Ideal Case + No Error Scaling (350 events - 10445 total tracks - 107428 total hits):
  • Summary plots:
• Nominal Case + Error Scaling (350 events - 10667 total tracks - 100965 total hits):
  • Summary plots:

Tests with our Alignment Constants (without using Vertex Refit) (01.03.2007)

An example of physics analysis with our alignment constants obtained starting from the nominal setup and 4 iterations of the GlobalX2 with its builtin vertex constraint.

Test on Z-->mu+mu- events

The alignment constats have been applied to reconstruct CSC Z-->mu+mu+ samples (5145) . Disclaimer as the alignment it only performed for the DoubleCone geometry then the two mouns candidates must lay within its acceptance (basically within |eta|<1.1).

The analysis is based on PIX+SCT only tracks. The selection of candidates is rather basic and at this stage of the analysis is not fine tunned at all. The following requirementes are applied:

• A Z candidate is formed from two oposite signed tracks.
• Each of the tracks must have a mimimum Pt of 10 GeV/c.
• The collinearity of the tracks must be > 60 deg.
• The Z candidate must have a Pt < 45 GeV/c

The distributions of these variables for the selected Z candidates and its muons is presented in here: . Plots are normalized to 1 pb-1 of integrated luminosity. Other distributions are:

• Residuals:
  • PIX Phi residuals:
  • PIX Eta residuals:
  • SCT residuals:

Test on minimum bias events

Again the alignment constants have been applied on a sample of CSC MinBias events (5001). Below one may find some distributions of basic observables.

• Track parameters:
• PIX Phi residuals:
• PIX Eta residuals:
• SCT residuals:

Test on ttbar events

Q/Pt plots can help to spot some problems in the momentum reconstrution. In particular non uniformities of the Pt due to sagitta or clocking effects. This is illustrated in the following pictures of Q/Pt vs phi0. In principle is easier to see this sagitta effect in the multimuon events as there is an explicit cut in generated Pt of 50 GeV/c. The spectrum in physics events is continuous. It has not a sharp cut, so seeing the sagitta effect is more difficult but possible. Check plots to convince yourself.

• 100K CSC multimuons, nominal setup, iPatRec, barrel tracks only:
• 9.9K CSC ttbar events, nominal setup, iPatrec, barrel tracks only:

Test on Higgs (130 GeV) -> ZZ -> 4l events

The data is stored here:

/lustre/ific.uv.es/grid/atlas/dq2/misal1_csc11/RDO/misal1_csc11.005300.PythiaH130zz4l.digit.RDO.v12003103_tid004087/

-- CarlosEscobar - 22 Mar 2007