1. ->K+K- Productions at 62.4GeV Au+Au Collisions
Outlines:
1.Dataset, cuts and methods
2.Phi signals centroid and width with different normalization methods
3.Raw Yields
4.Conclusions
Shengli Huang
Vanderbilt University
H/L Meeting Aug03
Shengli Huang

2. The dataset, cuts and methods
DataSet: 62.4GeV Au+Au:
full field: --
Centrality:0~83.7%
|VertexZ|<30cm
The total events~ 34M
Kaon selections:
Quality 31&63
To get more phi signals
~ EMCal: isK<2,mom<2.5GeV/c
~ TOFw: isK<2, mom<4.0GeV/c
Ghost and intruder tracks are kicked out
Mixing event methods:
8 centrality bins
6 VertexZ bins
10 mixing events
Normalization methods:
1)Akiba:Nevents/Nmixevents
2)Hemmick:2*sqrt(N++N--)
3)Integral yield(m0>1.10GeV)
Fit Function: Breit-wigner
with Gaussian mass resolution
of 1.4MeV
H/L Meeting Aug03
Shengli Huang

3. The Phi signal Centroid & Width
3.Integral:4.03 ± 0.44MeV
1.Akiba: 4.61±0.46MeV
Min-Bias
Width:
4.61 ± 0.46(sta) ±0.58(sys)MeV
Centroid:
1.020±0.0002(sta) ±0.0009(sys)GeV
Consistent with PDG value
2.Hemmick:4.93 ± 0.47MeV
H/L Meeting Aug03
Shengli Huang

4. The Centrality Dependence
(Integral)
(Akiba)
(Hemmick)
Three methods results do not
indicate that phi’s centroid & width
have centrality dependence
No significant variance with
PDG value is observed in systematic
errors.
H/L Meeting Aug03
Shengli Huang

5. Yield(I):Simple Count
Yield is extracted by counting within a mass window of ±5MeV
about the measured φ mass centroid.
Normalization Method
Yield
1)Akiba
5606±213
2)Hemmick
5751±213
3)Integral
5312±213
Normalization factor difference is ~0.9%
While yields difference is ~8%
H/L Meeting Aug03
Shengli Huang

6. Yield(II):Fit 1)Akiba 3)Integral Yield is extracted by fitting with
average yield is 7668
2)Hemmick
Normalization factor difference<1%
While yields difference ~9%
H/L Meeting Aug03
Shengli Huang

7. Yield(III):Fit 3)Integral 1)Akiba Yield extracted by fitting with
2)Hemmick
Average yield is 9073
Three methods’ difference
is about 0.8%
H/L Meeting Aug03
Shengli Huang

8. Conclusions
1.The centriod and width of phi meson have been studied during
K+K- channel reconstruction at 62.4GeV Au+Au collisions. No
clear evidence indicates that there is centrality dependence or
variance with PDG.
2. The raw yield is extracted by three difference methods. The
method of fitting by “Breit-Wigner + constant” is found
unsensitive to the normalization methods.
H/L Meeting Aug03
Shengli Huang