EHS/NA22 Collaboration Na Li Institute of Particle Physics
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高高高高高高高高高高高 高高 高高高高高高高高高高高 高高 Boost Invariance Boost Invariance and and Multiplicity Depe Multiplicity Depe ndence ndence of the of the charge balance function charge balance function in pi+p and K+p collisions at in pi+p and K+p collisions at √ √ s s NN NN = 22 = 22 GeV GeV 1. Introduction 1. Introduction ● ● why BF why BF ● current status current status ● motivation motivation ● data data 2. Main Results and Discussions 2. Main Results and Discussions 3. Summary 3. Summary EHS/NA22 Collaboration EHS/NA22 Collaboration Na Li Na Li Institute of Particle Physics Institute of Particle Physics Phys. Lett. B 6 37(2006)
description
Boost Invariance and Multiplicity Dependence of the charge balance function in pi+p and K+p collisions at √ s NN = 22 GeV. Phys. Lett. B 637(2006). EHS/NA22 Collaboration Na Li Institute of Particle Physics. 1. Introduction ● why BF ● current status ● motivation ● data - PowerPoint PPT Presentation
Transcript of EHS/NA22 Collaboration Na Li Institute of Particle Physics
高能物理学会第七届年会 李娜高能物理学会第七届年会 李娜
Boost InvarianceBoost Invariance andand Multiplicity DependenceMultiplicity Dependence oof thef the charge balance functioncharge balance function
in pi+p and K+p collisions at in pi+p and K+p collisions at √√ssNNNN = 22 GeV = 22 GeV
1. Introduction1. Introduction ● ● why BF why BF ●● current status current status ●● motivation motivation ●● data data
2. Main Results and Discussions2. Main Results and Discussions3. Summary3. Summary
1. Introduction1. Introduction ● ● why BF why BF ●● current status current status ●● motivation motivation ●● data data
2. Main Results and Discussions2. Main Results and Discussions3. Summary3. Summary
EHS/NA22 CollaborationEHS/NA22 CollaborationNa Li Na Li
Institute of Particle PhysicsInstitute of Particle Physics
Phys. Lett. B 637(2006)
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Introduction: Introduction: Why Balance Function☞ Why Balance Function☞
)},|,(),|,(),|,(),|,({2
1)|( 1212121212 pbpbpbpapapapapbppB
D. Drijard et al., Nucl. Phys. B155, 269(1979); B166, 233(1980);
H. Aihara etal., Phys. Rev. Lett. 53, 2199(1984);
P. D. Acton et al., Phys. Lett. B305, 415(1993).
Charge compensation in hadronization in eCharge compensation in hadronization in e++ee- - ,, l-h,l-h, h-h!h-h!
old interest:old interest:
),|,( 12 papb is the conditional probability
BF measures how the conserved electric charges compensate in the phase space, i.e., how the surrounding net charges are rearranged if the charges of selected point change from negative to positive due to the charge conservation.
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If QGP is formed in the early stage of the collision, oppositely charged pairs are expected to be created later and correlate more tightly in
momentum space, i.e., a significant narrowing of BF is expected in A-A.
new new interestinterest : : S. A. Bass, P. Danielewicz, and S. Pratt, PRL 85, 2689(2000).
Clocking hadronization in A-A!
})()()()(
{2
1)|(
n
ynyn
n
ynynYyB W
21 yyy Relative rapidity
)( yn counting the pairs that satisfy the criteria in the rapidity window
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Narrowing of the Balance Function with centrality in Au+Au ColliNarrowing of the Balance Function with centrality in Au+Au Collisions at sions at √s√sNNNN=130GeV=130GeV
Current status:
Introduction: Introduction: ☞☞ Current statusCurrent status
J. Adams et al., (STAR Coll.), PRL90, 172301(2003);J. Adams et al., (STAR Coll.), PRL90, 172301(2003);
k
ii
k
iii
B
yBy
1
1
)(
Width of BFWidth of BF
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System size and centrality dependence of the balance function in ASystem size and centrality dependence of the balance function in A+A Collisions at+A Collisions at√s√sNNNN=17.2 GeV=17.2 GeV
Current status:
Introduction: Introduction: ☞☞ Current statusCurrent status
C.Alt et al., (NA49 Coll.), PRC71, 034903(2005);C.Alt et al., (NA49 Coll.), PRC71, 034903(2005);
Narrowing of BF with Narrowing of BF with increasing system size increasing system size and multiplicityand multiplicity
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Central collision and heavy nuclear Narrowing of BF QGP
Some Important QuestionSome Important Question
How BF behaves in h-h collision? How the limited detector acceptance influences the wid
th of BF? Are the results form different heavy ion experiments c
omparable?
Introduction: Introduction: ☞☞ MotivationsMotivations
)1)(|()|(W
W Y
yyBYyB
A useful formula
[S. Jeon and Scott Pratt, PRC (2002) ]
Boost invariance of BF?
? ?
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π+ p and π+ p and + p Collisions + p Collisions
at 22GeVat 22GeV
A total of 44 524 NSD events 0.001GeV/c < pt < 10 GeV/c 0.001GeV/c < pt < 10 GeV/c full 4π acceptance full 4π acceptance
Introduction: Introduction: ☞☞ DataData
M. Adamus, et al., (NA22 Coll.), Z. Phys. C32, (1986)475;M. Adamus, et al., (NA22 Coll.), Z. Phys. C32, (1986)475;
M. Adamus, et al., (NA22 Coll.), Eur. Phys. J. C21, (2001)271;M. Adamus, et al., (NA22 Coll.), Eur. Phys. J. C21, (2001)271;
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Results and discussion: Results and discussion: ☞ ☞ A direct checking of boost invariance ofA direct checking of boost invariance of balance function in full phase spacebalance function in full phase space
☞ Boost invariance of BF is valid over the whole rapidity space, in contrast to the strong dependence of the particle density on rapidity;
☞ Charge correlation is essentially the same in any longitudinally-Lorentz-transformed frame!
☞ Boost invariance of BF is valid over the whole rapidity space, in contrast to the strong dependence of the particle density on rapidity;
☞ Charge correlation is essentially the same in any longitudinally-Lorentz-transformed frame!
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Results and discussion: Results and discussion: ☞ ☞ BF for different widths of rapidity windowsBF for different widths of rapidity windows
☞ BF becomes narrower with decreasing size of rapidity window
☞ BF becomes narrower with decreasing size of rapidity window
☞ holds approximately, thus BF for whole phase space can be obtained, therefore, different experimental results are comparable.
☞ holds approximately, thus BF for whole phase space can be obtained, therefore, different experimental results are comparable.
)1)(|()|(W
W Y
yyBYyB
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☞ The hadronization scheme with string fragmentation implemented in PYTHIA qualitatively reproduces the multiplicity dependence of the data.
☞ The hadronization scheme with string fragmentation implemented in PYTHIA qualitatively reproduces the multiplicity dependence of the data.
☞ BF becomes narrower with increasing multiplicity in h-h collisions.
☞This multiplicity effect should be properly accounted if the narrowing of BF is used as a QGP signal.
☞ BF becomes narrower with increasing multiplicity in h-h collisions.
☞This multiplicity effect should be properly accounted if the narrowing of BF is used as a QGP signal.
Results and discussion: Results and discussion: ☞ ☞ BF for different multiplicity intervalsBF for different multiplicity intervals in full phase spacein full phase space
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Results and discussion: Results and discussion: BF and charge fluctuations☞ BF and charge fluctuations☞
ch
Y
W n
Qyd
Y
yyB
QD W 0
)1)(|(14
)(
S. Jeon and Scott Pratt, PRC65,044902 (2002)
☞ D(Q) is independent of the position of the rapidity window , same as BF.
☞ D(Q) is independent of the position of the rapidity window , same as BF.☞ Limited acceptances
will destroy the boost-invariance
☞ Limited acceptances will destroy the boost-invariance
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SummarySummary It is the first time to find that BF is invariant under a longit
udinal boost over the whole rapidity region, in contrast to the strong dependence of the particle density on rapidity;
BF in a limited rapidity window is boost-invariantly related to that in the full rapidity range and the results from different collaborations are comparable;
BF becomes narrower for increasing multiplicity in h-h collision, therefore, this influence should be properly accounted for before using narrowing of BF as a QGP signal;
The charge fluctuations are boost invariant but depend on the size of the rapidity window.
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Appendix IAppendix I
● ● on the measure of charge balance functionon the measure of charge balance function
)(
),()|(
,
,
s
Q
s
s
y
yyyy
s
s
s
)|()|(),|( ,,
s
Q
s
Q
ssyyyyyQyq ss
)|()|()|()|(
),|(),|()|(
ssss
sss
yyyyyyyy
yyqyyqyyq
Associated particle densityAssociated particle density::
the density of particles of charge Q at rapidity ythe density of particles of charge Q at rapidity y under the condition that under the condition that
a particle of charge Qa particle of charge Qss is detected at the rapidity y is detected at the rapidity ys.s.
Associated net charge densityAssociated net charge density::
the net charge density at rapidity ythe net charge density at rapidity y under the condition that there existsunder the condition that there exists
a particle of charge Qa particle of charge Qss at the rapidity y at the rapidity ys.s.
Associated charge density Associated charge density balancebalance::
A measure of the change of the associated net charge density, A measure of the change of the associated net charge density, when the when the
charge of the selected particle(s) is changed from negative to positive.charge of the selected particle(s) is changed from negative to positive.D. Drijard, et al., (ACCDHW Coll.) , Nucl. Phys. B166(1980)233-242;
D. Drijard, et al., (CCHK Coll.) , Nucl. Phys. B155(1979)269.
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Monte Carlo: Monte Carlo: PYTHIA☞ PYTHIA☞
☞ The hadronization scheme with string fragmentation implemented in PYTHIA qualitatively reproduces the trend of the data
☞ The hadronization scheme with string fragmentation implemented in PYTHIA qualitatively reproduces the trend of the data
