Frontemare di Trieste
Istituto Nazionale di Fisica Nucleare
Sezione di Trieste

Systematics Uncertainties

The investigated systematic uncertainties are listed below together with their maximum value. Table 1 shows a summary of the systematic uncertainties.

EM_Sys_Table.png

Table 1: Sources of systematic uncertainties and their relative contribution (minimum and maximum values as a function of pt) to the yields and to the spectrum fit parameters.

Tracks. From other analysis, an uncertainty of 3% has been taken for the π .

Topological selections. Each selection cut (DCA Λ to PV, DCA π to PV, DCA Λ daughters, Λ Cosine of Pointing Angle, mΛ) has been varied by ±10% around the standard value. The overall uncertainty ranges from 2 to 7%.

TPC dE / dx selection for PID. The cut has been varied from the default 3 to 2.5 or 4.5 and the maximum seen deviation was taken to be the systematic uncertainty due to this selection. Up to 6%.

Signal extraction. Contributions to the systematic errors from the signal extraction procedure

  • Event mixing normalization region. Several regions chosen. Less than 5%.
  • Range of the polynomial fit to the MC residual background. Varied by ±10%. Less than 3%.
  • Fit to real data of the residual background extracted from MC data. Up to 10%.\
  • Fit of the Λ contamination peak from MC data to real data. The Gaussian peak from MC data was used either to set the mean and the width of the combined (Gaussian + Breit-Wigner) fit or to fix them. The difference accounted for as systematic uncertainty. Up to 10%.

Material Budget. From previous analysis the material budget uncertanties are conservatively estimated at 4% constant throughout pt. Uncertainty due to the Geant3 / Fluka correction. From the Λ analysis an uncertainty due to the Geant3 / Fluka correction of 1% is taken.

Normalization Uncertanties. The uncertainty on the normalization is provided internally by the collaboration and is estimated to be asymmetrical, + 7% and −3.5% acting on all yield values.

Spectrum fit function. The extrapolated part of the spectrum has been fitted using different fitting functions and an uncertainty of 15% was found.

Summary of the Uncertainties. Figure 1 summarizes all the uncertainties considered for the preliminary spectra except the normalization uncertainty, taken to be asymmetrical.

EM_Sys.png

Figure 1: Statistical and systematic uncertainties in the yields for the Σ∗+. Note that the normalization uncertainty, being asymmetric, was not included in these plots.

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