strangeness from 20 to 158 agev
DESCRIPTION
Strangeness from 20 to 158 AGeV. V. Friese Gesellschaft f ür Schwerionenforschung Darmstadt, Germany [email protected]. for the collaboration. Outline. NA49 results on particle spectra and yields at SPS energies (30 – 158 AGeV) :. Kaon and pion spectra at 30 AGeV - PowerPoint PPT PresentationTRANSCRIPT
Strangenessfrom 20 to 158 AGeV
V. FrieseGesellschaft für Schwerionenforschung
Darmstadt, [email protected]
for the collaboration
2 SQM03 Atlantic Beach V. Friese, March 2003
Outline
Kaon and pion spectra at 30 AGeV
Energy Dependence of K/ ratio
spectra at 40 and 80 AGeV
Energy dependence of yield and slope parameter
at 158 AGeV: Dielectron channel
Outlook on in 40 AGeV and in 30 and 40 AGeV
Particle yields : Chemical freeze-out
Transverse spectra : Kinetic freeze-out
NA49 results on particle spectra and yieldsat SPS energies (30 – 158 AGeV) :
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Experimental Setup
Large acceptance hadron spectrometer
Tracking and dE/dx PID in TPCs
TOF for PID at mid-rapidity
Magnetic field scaled with beam energy
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Particle ID in NA49
p < 2.5 GeV :TOF
at midrapidity
2,5 < p < 10 GeV :TOF + dE/dxat midrapidity
p > 7 GeVdE/dx
forward rapidity
TOF resolution : ~ 60 psdE/dx resolution : ~ 4 %
for resonances : + invariant massfor weak decays : + topology
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The NA49 Energy Scan Program
Beam Energy Centrality Event Statistics Taken in
158 AGeV 10 % 800 k 1996
158 AGeV 20 % 3,000 k 2000
80 AGeV 7 % 300 k 2000
40 AGeV 7 % 700 k 1999
30 AGeV 7 % 400 k 2002
20 AGeV 7 % 300 k 2002
Central Pb+Pb Data Taking :
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The NA49 Energy Scan Program
Central Pb+Pb Data Analysis of Single Particle Spectra & Yields :
Energy K+ K- - + - +
158 AGeV publ. publ. publ. publ. final final publ. publ. prel. prel.
80 AGeV publ. publ. publ. prel. final final
40 AGeV publ. publ. publ. prel. final final prel. prel. prel. prel.
30 AGeV prel. prel. prel. prel. prel.
: Phys. Lett. B491 (2000) 59: Phys. Lett. B538 (2002) 275K, : Phys. Rev. C66 (2002) 054902
20 AGeV : not yet analysed
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Energy Dependence of Kaon Production
Status at QM2002 :
Monotonic rise in K-/-
Maximum in K+/+ between AGS and low SPS energiesSharp maximum in ES predicted by Stat. Model of the Early Stage
?
??
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Kaons at 30 AGeV : Transverse Spectra
at mid-rapidity
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Energy Dependence : Kaon Slope Parameters
No dependence of kaon slope parameters on energy at SPS
Modification of EOS in phase transition region ? see hep-ph/0303041
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Kaons at 30 AGeV : Rapidity Distributions
No increase in midrapidity kaon yield from 30 to 40 AGeV
p r
e l i
m i
n a
r y
p r
e l i
m i
n a
r y
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Energy Dependence : Mid-Rapidity K-/K+
30 GeV point follows smooth evolution from AGS over SPS
to RHIC
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Energy Dependence : Mid-Rapidity K/
K-/- : in 30 AGeV similar to 40 AGeV K+/+ : significant increase from 40 to 30 AGeV
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Energy Dependence : Total K/ Ratios
Indication for kink structure also for K-/- ?Sharp maximum for K+/+ !
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Energy Dependence : Strangeness to Entropy
)(2 KK
ES
8.0/)( K
where not published :
Data at 30 AGeV supportphase transition scenario
(Statistical Model of the Early Stage)
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at 40 and 80 AGeV
= ss : more sensitive to strangeness enhancement than kaons ?
n.b. : small deviation from PDG massseen at all three Pb+Pb data sets, but not in pp.
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: Transverse Spectra
NA49 preliminary
Inverse slope increases with energyIn contrast to K+ and K-, but similar to
NA49 preliminary
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: Rapidity Distributions
40 AGeV 80 AGeV 158 AGeV
p r e l i m i n a r y
statistical errors only
Rapidity width increases with energysimilar to kaons and pions
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Energy Dependence : Yields
Monotonic increase in /
/ K- constant with beam energy up to RHIC
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at 158 AGeV : The Puzzle
Strong differences in slope and yield between hadronic channel (NA49) and dimuon channel (NA50)
Rescattering of kaons in microscopic models accounts for ~30 % in total yield and ~ 20 MeV in slope only
Measurement of e+e- in NA49
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at 158 AGeV : The Dielectron Channel
e+e- 158 AGeV Pb+Pb 20 % central 3 M events
e+e- inv. mass spectrum background subtracted
No signal observedUpper limit estimate : <> <~ 40
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Cascades at 40 AGeV
- and + seen and analysed in 40 AGeV (central + minimum bias)
see Talk by C. Meurertoday 15:10
par. session # 1
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at 30 and 40 AGeV
First rapidity distribution of in Pb+Pb at 158 AGeV
measured by NA49(see QM2002)
see talk by M. MitrovskiFriday 15:10
Signals now observed in 30 and 40 AGeV :
40 AGeV
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Particle Yields at 40 and 80 AGeV
courtesy of F. Beccatini
Particle yields at all three energies can be fitted by the Hadron Gas Model with partial strangeness saturation
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Energy Dependence : Chemical Freeze-Out
Chemical freeze-out occurs on a smooth curve in T-B
At SPS : close to phase boundary
cross-over : Fodor / Katz, hep-lat 0204029
C.R. Allton et.al., hep-lat 0204010
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Kinetic Freeze-Out : mid-rapidity mt spectra
pions and deuterons not included in fit
158 AGeV
radial flow fit(blast wave)
also describes heavy hyperons
common freeze-out behaviour for all
measured particles
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Kinetic Freeze-Out at 40 AGeV
40 AGeV
good description also at 40 AGeV
and 80 AGeV (not shown)
Parameters T and T similar for all three energies
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The NA49 program on system size dependence
Enhancement in strange particle production observed in Pb+Pb compared to pp collisionsCan this be observed already in smaller systems (Onset) ?
Study strange particle production in peripheral Pb+Pb
but : peripheral Pb+Pb has different geometry than central collisions of light nuclei at same Npart
Study in addition strangeness production in light ion collisions
Data sets available : Pb+Pb, 158 AGeV, min. bias.Pb+Pb, 40 AGeV, min biasC+C, Si+Si, 158 AGeV
see Talk by I. Kraus, in C+C and Si+Si
Sunday 17:00par. session #4
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Summary
New data from NA49 on kaon production in Pb+Pb at 30 AGeV:K+/+ shows a sharp maximum around 30 AGeVK-/ - similar to 40 AGeVKaon inverse slope parameters stay constant at SPS energiesData support the phase transition scenario of SMES
production in 40 and 80 AGeV: / increases monotonically with beam energy inverse slope parameters also increase from AGS over SPS to RHICDisagreement of yields in hadronic and muonic channels at 158 AGeV
still unresolvedNo signal seen by NA49 in the dielectron channel
First results on cascades and at lower SPS energies
Analysis of light systems is ongoing
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Outlook
Data taking for energy scan completed
K/ excitation function will be completed with 20 AGeV data
and in 20 and 30 AGeV to be analysed
Spectra and yields for cascades at 20, 30 and 80 AGeV
/ ratios at 20 (?), 30, 40 and 80 (?) AGeV
Analysis of K* at all available beam energies
System size dependence of strangeness production to be finalised
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Energy Dependence of Pion Multiplicity