This is the wiki for the W and Z analyses using the Barrel Electromagnetic Calorimter (BEMC) at STAR.
The goal of the analyses is to measure a cross section and single helicity asymmetry, A_L.
Introduction
Single spin asymmetries in W and Z production can be used to probe the spin structure of the proton.
Detector
STAR detector at RHIC is used to reconstruct charge and neutral EM particles from pp collisions at sqrt of 500 GeV.
Signal
Wiki Markup
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event
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generator
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is
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used
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to
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produce
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pp
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events
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yielding
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.
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An
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example
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of
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W-event
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which
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decay
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to
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electron
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and
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neutrino
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is
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shown
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on
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the
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plot
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below.
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Requirement
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has
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been
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imposed
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on
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this
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event
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to
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deposit
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at
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least
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20
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GeV
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of
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ET
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in
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EMC
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in
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single
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cluster
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located
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at
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phi
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[80,100
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]
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deg
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and
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pseudo-rapidity
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[-0.8,+0.8
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]
Backgrounds
Most common type of result of collision of 2 protons is a pair of jets. Below you can see and example of such QCD background event passing the same criterium of depositing at least 20 GeV ET in localized cluster.
Below are example of STAR response to W-event (left) and QCD-event (right)
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