KoreaCmsWiki> HeavyIon Web>DongHosLog>DongHoNewLog>MDH0000>AnalysisTips (2015-09-18, DongHoMoon)

## Useful Analysis Tips

### usage of git hub

• git clone "https://github.com/CMS-HIN-dilepton/Dimuons"

### Way to copy the sample from different site

```voms-proxy-init
xrdcp root://cmseos.fnal.gov//store/user/benwu/CMSDAS/DoubleMu/crab_CMSDAS_Data_analysis_test0/141126_235113/0000/slimMiniAOD_data_MuEle_1.root .
```

### Error bar estimation of Two efficiency multiply

```   y = f * g (f : Eff1, g : Eff2)
dy = (@y/@f)df + (@y/@g)dg

Relative error
dy/y = [(@y/@f)df + (@y/@g)dg]/fg
here, y = f*g, so (@y/@f) = g, (@y/@g) = f
dy/y = df/f + dg/g

|dy| = sqrt( (df/f)^2 + (dg/g)^2 )
final value is y + | dy | = y + sqrt( (df/f)^2 + (dg/g)^2 )*y

Therefore
the error bar of multiplied two variables
is sum of the each error of those.

Dividing error:
y = f/g >> dy = (f/g)' = f'/g - g'/g^2
dy/y = (f/g)'/(f/g) = f'/f -g'/g
| dy | = sqrt( (df/f)^2 + (dg/g)^2 )
final value is y + | dy | = y + sqrt( (df/f)^2 + (dg/g)^2 )*y

```

### efficiency of pair

```The factor 2 comes from the from the fact that the two single muon efficiencies that make the pair efficiency are fully correlated.
In that case the uncertainty on pair is just the sum of the uncertainties on the single efficiency. You can also simply derive it like this:

for eff_pair = eff_single^2

-> err_pair = sqrt( (deff_pair/deff_single)^2 err_single^2 )
= sqrt( (2*eff_single)^2*err_single^2)
= 2*eff_single*err_single

that's the expression for the absolute uncertainty, to get the relative uncertainty, we just divide by eff_pair

-> err_pair/eff_pair = 2*eff_single*err_single/(eff_single^2)
= 2*err_single/eff_single

sqrt((eA/A)^2 + (eA/A)^2 + 2 (eA/A)^2) = sqrt( 4*(eA/A)^2 ) = 2 * eA/A

So, total uncertainty = sqrt( (2*eA_1/A_1)^2 + (2*eA_2/A_2)^2 + (2*eA_2/A_2)^2 ) // for the cases of three efficiencies.
```

### R_AA

• yield of Z / normalized Z yield in pp collisons
```   R_AA = [(d^2_N)/(d_pt * d_eta)]/[<T_NN>(d^2_crX/d_pt*d_eta)]
T_NN : nuclear overlap function
= N_coll/crX_pp
```
• 1/(2pi*pT) : invariant factor

### R_cp

• (yield of Z in the central collisions)/(yield of Z in the peripheral collisions)
```   R_cp =[<1/N_coll>|0<cent<5| * (d^2_N)/(d_pt * d_eta)]/[<1/N_coll>|40<cent<60| * (d^2_N)/(d_pt * d_eta)]\
```

### Python Tip

• 255 arguments error
``` readFiles = cms.untracked.vstring()
'/store/data/BeamCommissioning08/BeamHalo/RECO/CRUZET4_V4P_CSCSkim_trial_v3/0000/00BEE8CD-1181-DD11-8F58-001A4BA82F4C.root'
] );

process.source = cms.Source("PoolSource",
)
```

### pPb collision energy calculation

```sqrt(sNN) = 2*sqrt(E_p * E_pPb) = 2*sqrt(4 * 4 * 82 / 208) = 5.02 TeV
```

-- DongHoMoon - 03 Dec 2010

Topic revision: r14 - 2015-09-18 - DongHoMoon

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