Possible Topics for Real Data Analysis 2010

These are example areas where real data can be used to either directly prepare for our physics analysis in Bs->JpsiPhi/PhiPhi or test analysis methods such as angular acceptance correction and background subtraction. Some of these studies may have already been pursued in dedicated detector groups for the purpose of data quality checking. We have good reasons to include them as part of our physics projects with a differnet focus, as explained below.

Jpsi study


  • muon id calibration
  • momentum calibration
  • time resolution monitoring
  • Jpsi polarization measurement


Preparation based on MC

  • Prepare selection code using 3.5TeV minimum-bias MC data
    • No muon ID
  • Prepare sWeight-method for muon ID
    • Usinrg PVz weight to subtract beam gas
  • Prepare code for momentum scale with Jpsi
    • Adding muon id cut
  • Prepare code for time resolution with Jpsi
    • Using mass weight to subtract non-Jpsi background
  • Prepare code for jpsi polarization with Jpsi
    • Getting muon efficiency from MC data
    • Using time weight to subtract non-promp Jpsi
    • Using per event method to match momentum spectrum
    • Comparing unfolding method and fit method

Real data analysis

  • Keep looking for jpsi and optimizing selection criteria
  • Check muon id when having xxx events
  • Calibate momentum when having xxx events
  • Check time resolution after velo is closed
  • Measure Jpsi polarization when having xxx events

Check of kaon identification efficiency using phi->KK

The analysis of Bs->JpsiPhi/PhiPhi needs to monitor kaon identification efficiency for data collected at different times in order to optimize event selection. We cannot solely rely on the RICH group to do this for us.

Idea for using 2009 data: applying PID cuts on one kaon and check the efficiency of the other. A possible reason no result has been reported from the RICH group yet is becasue of the reletively high background level even after applying PID cuts on both kaons. Efforts to make: optimize event selection using PID cuts on one kaon; when the phi signal is visible, obtain kaon PID efficiency using a background subtraction method that has already been tested in Ks->pipi and Lambda->ppi using MC09 data.

Update on 13 March:

Prelinimary work has been done and reported to RICH meeting, Physics performance meeting. Results are used for LHCb week. Method has been adopted by the RICH group for all PID checks. A note will be prepared.

Measurement of track efficiency functions using Ks->pipi

Our method developed for angular acceptance correction allows us to obtain pion recontruction efficiency functions. A first test can be done with 2009 data in Ks->pipi.

Calibration of track parameters and covariance matrix using Ks ->pipi

Momentum scale calibration is an important issue for time-dependent analsyis. The tracking group has a baseline method. We have preliminary study which shows this can be improved and made automatic so that the physics groups can check the momentum scale as well as covariance matrix more carefully.

Measurement of Lambda polarization

This is a hot topic for using 2009 data. Our advantage is that we have a MC-free method to correct for the angular acceptance, which has a huge effect in this channel due to the different masses of proton and pion in the decay products.

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Topic revision: r5 - 2010-03-13 - YuehongXie
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