abhilash nair star collaboration university of illinois at chicago 1 star
DESCRIPTION
Time Projection Chamber (TPC) The TPC is a barrel shaped detector consisting of a gas-filled chamber, magnet providing a strong uniform magnetic field, and an electric field between the center and endplates We use measurements of the ionization energy loss (dE/dx) and momentum to identify particles 3TRANSCRIPT
Abhilash NairSTAR Collaboration
University of Illinois at Chicago
1STARSTAR
Beam Energy Scan at RHIC
STAR has collected data from the following collision energies (in decreasing energy order) :
200, 130, 62.4, 39, 19.6, 11.5, 9, 7.7 GeV
This presentation aims to show the work-in-progress analysis of the 39 GeV data sample
Spectra shapes and particle ratios help connect collected data to observables that are expected to change in such a phase transition 2
Properties of matter created at 200 GeV are consistent with an expected2nd order phase transition
Beam Energy Scan (BES) at RHIC looks to experimentally find the critical point of 1st order phase transition predicted to exist at lower energies
Simply a cartoon, does not represent actual experiential data
Time Projection Chamber (TPC)The TPC is a barrel shaped detector consisting of a gas-
filled chamber, magnet providing a strong uniform magnetic field, and an electric field between the center and endplates
We use measurements of the ionization energy loss (dE/dx) and momentum to identify particles
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Event SelectionFrom Min-Bias Trigger |Vz| < 30 cm |Vr| < 2 cm10 M events pass cuts
Track-Quality Cuts |Dca| < 3 cmNHitFits > 25NHitFits/NHitPoss > 0.51
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GeV39NNAu Au s
Vertex X [cm]
Vertex Z
2-D Particle-Centered Histograms
π K p
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Where superscript BB represents the expectation of dE/dx for a given particle i = ( π, K, p )
GeV39NNAu Au s
p (GeV/c)
Zπ Zk Zp
Gaussian Peak Fitting & Electron Contamination
π+
e+K+p
π-
e-K-
pbar
e-/e+ peak overlaps with nearby peaks in certain pT ranges
During crossover, e-/e+ peak is not reliable without further constraints
Without constraints, e-/e+ peak positions will jump sharply over a relatively small pT range
GeV39NNAu Au s
Zk Zk
Zk
Estimate of E-/E+ Contamination For overlap areas we rely on
extrapolated centroid positions and yields
This is done independently in each particle-centered histogram, and across different rapidity bins
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GeV39NNAu Au s
π
K p
e
pT (GeV/c) pT (GeV/c)
[-0.1 < y < 0.1)[-0.1 < y < 0.1)
e+ Centroids e+ Yields
STAR Preliminary STAR Preliminary
p (Gev/c)
Uncorrected Yields vs. mT-m0
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STAR Preliminary STAR Preliminary
STAR Preliminary
STAR Preliminary STAR Preliminary
STAR Preliminary
GeV39NNAu Au s
[-0.1 < y < 0.1)
[-0.1 < y < 0.1)
[-0.1 < y < 0.1)
[-0.1 < y < 0.1)[-0.1 < y < 0.1)
[-0.1 < y < 0.1)
mT-m0 (GeV) mT-m0 (GeV) mT-m0 (GeV)
mT-m0 (GeV) mT-m0 (GeV) mT-m0 (GeV)
π+
π-
K+
K-
p
pbar
Uncorrected Antiparticle to Particle Ratios Cannot make a physics conclusions without corrections, which
include: Single Particle Efficiency Energy Loss Correction Acceptance Proton Background
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STAR PreliminarySTAR Preliminary STAR Preliminary
GeV39NNAu Au s
mT-m0 (GeV) mT-m0 (GeV) mT-m0 (GeV)
π- / π+ K- / K+ pbar / p
[-0.1 < y < 0.1) [-0.1 < y < 0.1) [-0.1 < y < 0.1)
Efficiency, absorption, &background uncorrected
Efficiency, absorption, &background uncorrected
Efficiency, absorption, &background uncorrected
Proton Background: DCA Plots
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200 MeV < pT < 300 MeV
Phys. Rev. C 79 (2009) 34909
Phys. Rev. C 79 (2009) 34909
DCA plot courtesy of Alex Brown (UIC)
Dca [cm]
STAR Preliminary
Future OutlookOur work-in-progress min-bias
π+/π- ratio at 39 GeV is similar to results from 19 GeV & 200 GeV
Plans for the future include: Efficiency Corrections Proton Background Energy Loss Corrections Investigate Rapidity
Dependence K/Pi, p/Pi Integrated Yields & Ratios
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STAR Preliminary
mT-m0 (GeV)
π+ / π-
[-0.1 < y < 0.1)
Efficiency, absorption, &background uncorrected