Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 1 Zbigniew Chajęcki Ohio State University Collectivity in p+p Collectivity in p+p collisions? collisions? Z. Ch. & M. Lisa, PRC 78 064903 (2008) Z. Ch. & M. Lisa, PRC 79 034908 (2009) Z. Ch., Acta Phys.Polon.B 40 1119 (2009) Z. Ch. & M. Lisa, to be published
Z. Ch. & M. Lisa, PRC 78 064903 (2008) Z. Ch. & M. Lisa, PRC 79 034908 (2009) Z. Ch., Acta Phys.Polon.B 40 1119 (2009) Z. Ch. & M. Lisa, to be published. Collectivity in p+p collisions?. Zbigniew Chaj ę cki Ohio State University. Outline & Motivation. - PowerPoint PPT Presentation
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Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 1
Zbigniew ChajęckiOhio State University
Collectivity in p+p Collectivity in p+p collisions?collisions?
Z. Ch. & M. Lisa, PRC 78 064903 (2008)Z. Ch. & M. Lisa, PRC 79 034908 (2009)Z. Ch., Acta Phys.Polon.B 40 1119 (2009) Z. Ch. & M. Lisa, to be published
Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 2
Outline & MotivationOutline & Motivation common understanding of heavy ion collisions [soft sector]
p+p as a reference to heavy ion collisions
Effect of the phase-space constraints due to energy and momentum conservation
Results from 2-pion correlations in HIC and p+p Femtoscopic correlations
Re-examining multiplicity-evolution of pT spectra, considering evolution of available phase space postulate of unchanging parent distribution
Consistent treatment of the phase-space constraints and bulk in femtoscopy and spectra
Summary
Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 3
Heavy-ion collisions - A Heavy-ion collisions - A systemsystem
A+A a system
Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 4
STAR PRL 91 262301 (2003)
R (fm
)
mT (GeV/c2)
Spectra v2
Femtoscopy€
mT ≈ T + mβ flow2
Spectrav2
fast
Femtoscopy : two-pion correlations
slow
Femtoscopy : identical particle correlations
R (fm
)
mT (GeV/c2)
Femtoscopy : non-id particle correlations
K
STAR PRL 91 262301 (2003)
Heavy Ion Collisions : Explosive flow Heavy Ion Collisions : Explosive flow revealed through revealed through specific fingerprints specific fingerprints on soft-sector observableson soft-sector observables
Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 5
Importance of referenceImportance of reference
?=
Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 6
p+p as a reference: p+p as a reference: hard hard sectorsector
=
STAR, PRL93 (2004) 252301
Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 7
p+p as a reference: p+p as a reference: soft sectorsoft sector
= “flow”?
STAR PRL 92 112301 (2004)
p+p
Au+Au
eliptic flow
radial flow
Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 8
Phase-Space varies with Phase-Space varies with multiplicitymultiplicity
Phase-space constraintsExtreme case, N=3, easily calculable with Dalitz plot
What about the effect for higher number of particles?
Dalitz plot for a three-body final state. (p at 3 GeV), PDG 2008Pn ∝ SnRn
Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 16
femtoscopy in p+p @ STAR
DELPHI
Z0 decay @ LEP
m, mT (GeV)
R (fm
)R
Z(fm
)
hep-ph/0108194
π
K
p Λ
1. Heisenberg uncertainty?• e.g. G. Alexander• “plausible” in z-direction• unlikely in transvrse• inconsistent with mult-dep
2. String fragmentation? (Lund)• essentially no quantitative
predictions• pT dependence maybe (??)• mass dependence no
[Andersson, Moriond 2000]
3. Resonance effects?• e.g. Wiedemann & Heinz ‘97• maybe, but will be significantly
different effect than for Au+Au
p+p and A+A measured in same experiment, same acceptance, same techniques
•unique opportunity to compare physics•what causes pT-dependence in p+p?•same cause as in A+A?
4. Flow???• Increasingly suggested in HEP
experiments
HBT+ “conservation”
HBT
Z. Ch., Acta Phys.Polon.B 40 1119 (2009)
mmTT dep. of HBT radii - World Systematcs dep. of HBT radii - World Systematcs
Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 17
E735 Collaboration, PRD48 1931 (1993)also PLB 2002consistent with an expanding shell model.
NA22 Collaboration Z. Phys. C 71, 405–414 (1996)(hadron-hadron collisions)[based on shape of C(q)…]Our data do not confirm the expectation from the string type model… A good description of our data is, however, achieved in the framework of the hydrodynamical expanding source model.
W. Kittel Acta Phys.Polon. B32 (2001) 3927 [Review article]… and suggests the existence of an important “collective flow”, even in the system of particles produced in e+e− annihilation!
A 1/√m T scaling first observed in heavy-ion collisions is now also observed in Z fragmentation and may suggest a “transverse flow” even there!
R2tside , R2tout and, less markedly, R2long decrease with increasing kt . The presence of correlations between the particle production points and their momenta is an indication that the pion source is not static, but rather expands during the particle emission process.
PS effects fixed by correlationsJoint spectra/HBT BW fit
PS effects free adjustedto spectra & fit to spectra
PS effects fixed by correlationsJoint spectra/HBT BW fit
p+p collisions show same radial flow signals as A+A collisions
Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 29
STAR PRL 91 262301 (2003)
R (fm
)
mT (GeV/c2)
Spectra v2
Femtoscopy
Heavy Ion Collisions vs p+pHeavy Ion Collisions vs p+p
Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 30
Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 31
SummarySummary Energy and momentum conservation induces phase-space
constraint that has explicit multiplicity dependence– should not be ignored in (crucial!) N-dependent comparisons– significant effect on 2- (and 3-) particle correlations [c.f. Ollitrault, Borghini, Voloshin…]
– …and single-particle spectra (often neglected because no “red flags”)
Femtoscopy & Spectra– in H.I.C., well understood, detailed fingerprint of flow– RHIC – first opportunity for direct comparison with p+p
– accounting for finite phase-space effects identical flow signals in p+p
?
HBT
exp CF
HBT+ “conservation”
STAR PRL 92 112301 (2004)
STAR Preliminary
Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 32