Systematic studies

• In order to check if a given cut variation has a systematic effect, used Barlow method.
  • σ =√(YieidErr (var)^2 - YieldErr (sta)^2)
  • Judgement if observed RMS is systmatic or not ystematic is done based on (Yeild(var)-Yield(sta))/σ = 2.
  • Errorbars in ratio plots do not consider uncorelated errors.
• Consider the pT dependence of systematic.
• Note that inclusive eletrons spectra are used for systematic studies. (excluding systematic from photonic electrons)
• Error source
  • Tracking
    • Number of TPC clusters
    • Number of CrossedRows
    • Number of ITS clusters
  • PID
    • TPC nsigma
    • shower shape
    • E/p
  • Photonic electrons
    • minimum pT of associate tracks
    • invariant mass
  • Hadron contamination
  • Trigger rejection factor

Systematic from tracking

Number of TPC clusters

• cut variations : 80 (default), 70, 90, 100

• No systematic effect.

Number of CrossedRows

• cut variations : 100 (default), 90, 110, 120

• No systematic effect.

Number of ITS clusters

• cut variations : 3 (default), 2, 4

• Larger systematic is observed at low pT.
• RMS is fitted with landau function and applied pT dependent systematic uncertainty.
  • Values of systematic in each pT bin is obtained by fit->Eval().

Systematic from PID

TPC n_{sigma} (lower limit)

• cut variations : -1(default),-1.5 , -1.25, -0.75, -0.5

• Clear pT dependence is not observed from both Barlow test and RMS.
  • RMS is fitted with pol0 and constant systematic is applied (~ 3.5 %).

shower shape (upper limit)

• cut variations : 0.3(default),0.25 , 0.35, 0.4

• Barlow check says that fluctuations at low pT (< 5 GeV /c) are from systematic effects.
• Fluctuations at high pT are larger than low pT, but they are mostly come from statistical uncertainty.
  • Value of systematic is determined by using RMS to 5 GeV /c.
  • 1 % is applied for all pT bin.

E/p (lower limit)

• cut variations : 0.8(default),0.76 , 0.78, 0.82, 0.84

• low pT (< 5 GeV /c) has systematic fluctuation, and also has pT dependence.
  • RMS at pT < 5 GeV /c are fitted with exp, and systematic uncertainty in each pT bin is obtained by Eval() function.
• Fluctuations at high pT are not significant systematic effect.
  • In pT > 5 GeV /c, 1 % is applied.

E/p (upper limit)

• cut variations : 1.2(default),1.15 , 1.25, 1.3

• There is systematic effect from low pT to high pT.
• Systematic fluctuations are linear increasing with pT.
  • Fitted with pol1 function and systematic uncertainty in each pT bin is obtained by Eval() function.

Systematic from photonic electrons

minimum pT of associate tracks

• cut variations : 0.1 GeV /c (default), 0, 0.05, 0.15, 0.2

• Consider larger systematic at first pT bin .
  • 7 % is applied to first pT bin.
  • 1 % systematic is applied to others.

invariant mass of photonic electrons

• cut variations : 0.14 GeV /c^2 (default),0.10, 0.12, 0.16, 0.18

• Consider larger systematic at first pT bin .
  • 4 % is applied to first pT bin.
  • 1 % systematic is applied to others.

Systematic from hadron contamination

• Hadron E/p distribution is normalized to match the distribution of the electron candidate small E/p region than unity where hadron contribution is dominant.
• For estimating systematic, E/p range for calculating scale factor is changed.
  • Slide scale range between -0.1 and 0.1.

• RMS is calculated at inclusive electrons level.
• 10 < pT < 12 GeV /c and 20 < pT < 26 GeV /c have larger RMS due to larger hadron contamination.
  • 5 % is applied to 10 < pT < 12 GeV /c and 20 < pT < 26 GeV /c.
  • 1 % for other pT bins.

Systematic from trigger normalization

• Trigger normalization is determined the ratio of cluster energy per-event in MB and trigger.
• Trigger turn-on curve s fitted with Fermi function.
• For estimating the uncertainty, RMS of the data/fit is calculated.
  • 3 % in GA2, 8 % in GA1 is assigned as systematic uncertainty from trigger rejection factor.

Summary of systematic

-- DaichiKawana - 2018-04-12