K'Mikhaylov, A'Stavinsky ITEP STAR Meeting, Dubna 11June2008 1

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Status of KK femtoscopy in ALICE (Based on
Alice Week presentation)? Konstantin Mikhaylov
and Alexey Stavinskiy ITEP, Russia
K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
11June2008 1
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Outline

• Physics Motivation of KK femtoscopy
• Experimental results
• Distortions of KK correlation function
• - PID's of Kaons
• - Pair PID
• - Splitting-merging
• - Resonances ( vt source size) K, F
• First results for KK-
• Conclusion

K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
11June2008 2
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Physics motivation

• Measured space-time extent of the particle
  emitting region for KK is pure than for pp.
• Kaon femtoscopy signal is cleaner than pion
  femtoscopy signal since Kaons are less affected
  by resonance decay.
• The mT dependence mT(KK) gt mT(pp).
• The strangeness distillation mechanism could lead
  to strong temporal emission asymmetries between
  kaons and anti-kaons S.Soff et al.,
  J.Phys.G23,2095(1997)D.Ardouin et
  al.,Phys.Lett.B446,191(1999).
• Due to the highest branching ratio of F meson is
  KK
• the FF residual correlations could be seen from
  
• KK correlation function.

K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
11June2008 3
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Experimental results
CERN-SPS PbPb at 158 AGeV/c

PRL,87(2001)112301
RHIC-STAR AuAu sqrt(SNN)200GeV

KK
Phys.Rev.C 74 (2006),054902
K0SK0S
R 4.09 0.46(stat.) 0.31(sys) fm and ?
0.920.23(stat)0.13(sys) at the mean
transversemass ltmTgt 1.07 GeV.
The duration time ?tsqrt(r2out-r2side)/ß 2.2
5.2(stat.) 5.1(sys) fm
K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
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Experimental results II

RHIC-PHENIX AuAu sqrt(SNN)200GeV M. Heffner
J., Phys. G 30 (2004) S1043-S1047,
nucl-ex/0510014
t

• an approximately universal
• mT dependence is usually
• attributed to collective flow
• KK one dimensional radius
• 3-5 fm

K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
11June2008 5
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ALICE Software and input

• Aliroot (with AliFemto) v4-12-Rev-02
• Local analysis of 3K events
• PDC2007 HIJING PbPb 5.5 TeV (dNch/dy6500 )?
• 1D KK correlations
• 0.1 lt PT lt 1.0 GeV/c
• Anti-splitting cut
• Gaussian distr. d3N/d3r exp(-r2/(4r02))?
• KK r0 2 and 5 fm
• Source size for kaons from K decay was corrected
  on vKtK r'0sqrt(r02(vKtK)2)?

K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
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PID

p
K
p
K.Mikhaylov,A.Stavinsky ITEP

Alice Week, CERN
31March2008 7
K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
11June2008 7
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K Mothers

Kdirect 38 KK(892)0 35 KK(892) 19
KF 8, it is two times better than p
(pprim/pall 19)?
K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
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p Mothers

Resonances can play significant role for pp
correlations
K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
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Pair PID

100 events PbPb_at_5.5 TeV HIJING QINVlt0.25GeV/c
KdirKdir 7 7222( 6.95165)? KdirKK0
15298( 14.7253)? KdirKK 7652(
7.36555)? KK0KK 39 8181(
7.87475)? KK KK 2067( 1.98962)? KK0
KK0 8077( 7.77464)? KdirKF 3129(
3.01187)? KFKF 345( 0.332085)?
KK0(KK)KF 5022( 4.83401)? Other
exotic (KdirKD0,...) 1352( 1.30139)? (KK)fake
46896( 45.1405)? Total 103889
(100)?
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K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
11June2008 10
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KKModelExperiment

Splitting cut was applied
K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
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Source expansion due to K

Both K are direct

• KdirKdir source size is
• smaller than KdirKK
• due to K decay length
• Assume K source size the same as KdirKdir (r0)?
• Measured source in second case
• r'0 sqrt(r02(vt)2) KdirKK or
• r'0 sqrt(r02(v1t1)2(v2t2)2)KKKK
• Get v of K from generator (vt2.6 fm)?

K
r0
K
One K is direct and the other one from K decay
K
rmeasured
K
K(ct4fm)?
p
K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
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KK K source expansion(2fm)?
?
Source expansion due to K decay (r02fm, K vt
2.6fm)?

r02fm
r'02.6fm
Non Gaussian shape
K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
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KK K expansion (5fm)?
?
Source expansion due to K decay (r05fm, K vt
2.6fm)?

r05fm
r'05.5fm
K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
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KK- ModelExperiment

F ? KK-
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KK- K expansion(2fm)?

r02fm
r'02.6fm
Non Gaussian shape
K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
11June2008 16
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FF residual CF in KK-

K.Mikhaylov,A.Stavinsky ITEP

STAR Meeting, Dubna
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FF residual CF in KK-

• 3000 PbPb events
• Kaons only from K
• decay only
• Need More statistics
• K0K(/-) is better

K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
11June2008 18
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Conclusion

• 1. There are several sources of the KK
  correlation function distortion
• Single Kaon purity, Pair purity,
  Splitting-merging, Resonances
• 2. K expansion could be important for KK
• 3. Study of correlated background to be
  continued (fake pairs!)?
• 4. K0SK(-) is for FF residual correlations?
• Thank you for your attention!

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Extra Slides

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KKDifferent contribution

K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
11June2008 21
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KK- Different contribution

• With K
• Correlated background!!!

K.Mikhaylov, A.Stavinsky ITEP

STAR Meeting, Dubna
11June2008 22
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Extra Slides

Fake contribution to KK Good KK 57.9429 Fake
KK 42.0571 piK 27.2202 pipi
3.57522 pK 3.3108 eK
4.3075 muK 1.12317 pie
0.999998 ppi 0.71421 others
0.733494