Strangeness from 20 to 158 AGeV

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) :


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


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


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 :


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


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

?

??


Kaons at 30 AGeV : Transverse Spectra

at mid-rapidity


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


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


Energy Dependence : Mid-Rapidity K-/K+

30 GeV point follows smooth evolution from AGS over SPS

to RHIC


Energy Dependence : Mid-Rapidity K/

K-/- : in 30 AGeV similar to 40 AGeV K+/+ : significant increase from 40 to 30 AGeV


Energy Dependence : Total K/ Ratios

Indication for kink structure also for K-/- ?Sharp maximum for K+/+ !


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)


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.


: Transverse Spectra

NA49 preliminary

Inverse slope increases with energyIn contrast to K+ and K-, but similar to

NA49 preliminary


: 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


Energy Dependence : Yields

Monotonic increase in /

/ K- constant with beam energy up to RHIC


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


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


Cascades at 40 AGeV

- and + seen and analysed in 40 AGeV (central + minimum bias)

see Talk by C. Meurertoday 15:10

par. session # 1


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


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


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


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


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


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


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


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


Energy Dependence of Pion Multiplicity

Documents

Strangeness from 20 to 158 AGeV