Difference between the events with vertex cuts and that of without them

-event ID missing study-




Introduction

It appears that (only) the 2nd cycle data of E570 doesn't have a consistency about the strong interaction shift of KHeX La line. The events selected by the conditions for vertex reconstructions and the fiducial volume cuts (the ntuple was provided by Takatoshi-san) shows the shift is about -2 eV, on the other hand, the events not applied the conditions (means selected by only kaons stopping in the helium target) shows about -8 eV. These two results just barely overlaps with each other within their 1 sigma errors. This fact was veryfied by Okada-san also. In order to fix or cofirm this, the events of them must be compared with from the ntuple level.

It is expected that the difference between the events with vertex cuts and that of without them is only thier statistics. Futhermore the events with vertex cuts must be included in that of without them.
The statistical difference is roughly 40% of no vertex cut events in the region of interesting (KHeX La).

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Fit results with figures

The fit results of final histograms are shown in following figures. There are three types of histograms, 1) without vertex cut, 2) with vertex cut and 3) difference of them. The shift of KHeX La line obtained by fitting the differece histogram in 2nd cycle is about -15 eV. From this result, we may be able to say the difference of the shift is caused by their statistics simply. But furthermore study must be needed.
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