results from na49 at the cern sps

P.Seyboth: Results from NA49 at the CERN SPS 23rd Winter Worshop on Nuclear Dynamics - Big Sky, February 12-17, 2007

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Results from NA49 at the CERN SPS

• NA49 experiment• Recent results on inclusive production

– Baryon stopping (E.Kornas, C.Blume)– He3, tritium production (V.Kolesnikov)– Intermediate pT results (A.Laszlo, T.Schuster)– Elliptic flow (G.Stefanek)

• Status of fluctuation measurements (K.Grebieszkow, M.Rybczynski, B.Lungwitz, C.+G.Roland)

• Future plans

P.Seyboth, Max-Planck-Institut für Physik, Munich for the NA49 collaboration

Results on pion source imaging → talk by R.Lacey


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C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Białkowska, C. Blume, B. Boimska, M. Botje, J. Bracinik, R. Bramm, P. Bunčić, V. Cerny,

P. Christakoglou, P. Chung, O. Chvala, J.G. Cramer, P. Csató, P. Dinkelaker, V. Eckhardt, D. Flierl, Z. Fodor, P. Foka, V. Friese, J. Gál, M. Gaździcki, V. Genchev, G. Georgopoulos, E. Gładysz, K. Grebieszkow, S. Hegyi,

C. Höhne, K. Kadija, A. Karev, D. Kikola, M. Kliemant, S. Kniege, V.I. Kolesnikov, E. Kornas, R. Korus, M. Kowalski, I. Kraus, M. Kreps, A. Laszlo, R. Lacey, M. van Leeuwen, P. Lévai, L. Litov, B. Lungwitz, M. Makariev, A.I. Malakhov, M. Mateev, G.L. Melkumov, A. Mischke,

M. Mitrovski, J. Molnár, S. Mrówczyński, V. Nicolic, G. Pálla, A.D. Panagiotou, D. Panayotov, A. Petridis, W. Peryt, M. Pikna, J. Pluta, D. Prindle, F. Pühlhofer, R. Renfordt, C. Roland, G. Roland, M. Rybczyński, A. Rybicki, A. Sandoval,

N. Schmitz, T. Schuster, P. Seyboth, F. Siklér, B. Sitar, E. Skrzypczak, M. Slodkowski, G. Stefanek, R. Stock, C. Strabel, H. Ströbele, T. Susa,

I. Szentpétery, J. Sziklai, M. Szuba, P. Szymanski, V. Trubnikov, D. Varga, M. Vassiliou, G.I. Veres, G. Vesztergombi, D. Vranić, A. Wetzler,

Z. Włodarczyk, A. Wojtaszek, I.K. Yoo, and J. Zimányi

The NA49 Collaboration


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The NA49 Detector

Target: Pb foil, 20cm liquid H2 VCAL detects projectile spectatorsΔp/p2 = 7 (0.3) • 10-4 (GeV/c)-1 (VTPC-1, VTPC+MTPC)Particle identification: dE/dx (3 – 6 %), TOF (~ 60 ps) decay topology (K0, Λ, Ξ, Ω)

p > 7 GeV/cdE/dx

forward rapidity

2.5 < p < 10 GeV/c TOF + dE/dxat midrapidity


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Baryon stopping (1) Proton and antiproton rapidity spectra in central Pb+Pb collisions

• new results from dE/dx analysis at forward rapidities• published results from TOF analysis at midrapidity (PRC73(2006)044910)

NA49 preliminary NA49 preliminary

pp

evolution of shape, decrease of yield Gaussian shape, increase of yield


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Baryon stopping (2)net-baryon distributions in central 7% Pb+Pb collisions

construction of net-baryon distributions:

scaling factors taken from statistical model fits F.Becattini et al., PRC73 (2006) 044905

0( ) ( ) ( ) ( )nN B B S p p S S

NA49 preliminary

20A GeV 30A GeV 40A GeV 80A GeV


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Baryon stopping (3)

NA49 preliminary

evolution of net-baryon rapidity distributions

• pronounced change of shape at SPS energies peak -> dip structure

• net-baryon density decreases rapidly at mid-rapidity


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Baryon stopping (4) energy dependence of projectile rapidity loss <δy>/yp

Central Pb+Pb/Au+Au

preliminary

p

p

yB-B

p 0part

y = y - <y>

dN2 = y - y dyN dy

• at AGS, SPS constant ≈ 0.6 decrease at RHIC energies• reproduced by UrQMD <xF>≈ 0.38

(UrQMD: M.Bleicher, Florence Workshop)


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Baryon stopping (5)

BBNN

inel Es

E 2

energy dependence of inelasticity K

Inelasticity:

pNN

inel

msEK

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central A+A collisionsNA49 preliminary

Total inel. energy per net-baryon:

1 cosh ( ) p

p

yB B

TB B yyB B

dNE m y dy

N dy

Energy of single net-baryon:

Inelasticity saturates at K = 0.7-0.8 above SPS


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light fragments (1)

3He

td

3He identification: dE/dx + TOF

NA49 preliminary

t

Central Pb+Pb|y | < 1.0

NA49 preliminary3He

Central Pb+Pb

|y | < 1.0


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light fragments (2)

1const~ A-pdy

Adn

coalescence paramater

from p spectra:

NA49 preliminary

penalty factor

agrees with statistical hadron gas prediction

mid-rapidity yields

p d He3

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3 3 , A

pAA A p A p

A p

d Nd NE B E P A PdP dP

gradual decrease with energy


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light fragments (3)

NA49 preliminary

3HeCentral Pb+Pb

total yields estimated from parabolic fits up to |ybeam| (motivated by RQMD)

3HeCentral Pb+Pb4 yields

NA49 preliminary

yields show surprising agreement with statistical hadron gas model

F.Becattini et al., PRC73 (2006) 044905


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light fragments (4) coalescence model blast wave model

20A GeV

NA49 preliminary

Central Pb+Pb|y | < 1.0

larger T, smaller <βT> required for d,3He

constant density, v(r) = vf (r/Rf)α

→ <mT> - m ~ A1-α (A.Pollieri et al., PLB419 (1998) 19)

linear velocity increase ok


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Intermediate pT results (1)

baryon/meson ratio

• deviates from blast-wave (hydro) for pT > 1.2 GeV/c as at RHIC

• SPS data reach coalescence range but end below pQCD region


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Intermediate pT results (2)Baryon/meson ratio at SPS vs RHIC

SPS: central Pb+Pb at √s= 17.3 GeVRHIC: central Au+Au at √s= 200 GeV • same relative increase with pT

at SPS and RHIC


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Intermediate pT results (3)nuclear suppression factor of pions at SPS and RHIC

2

2coll AA t

AA tpA tcoll

N pA d N dp dyR p

d N dp dyN AA

2

2

1 AB tAB t

pp tcoll

d N dp dyR p

d N dp dyN AB

SPS NA49 preliminary

RHIC Phenix

similar increase of ratio at SPS in pPb and PbPb (Cronin effect)

approaches binary scaling at SPS in accessible pT range

PbPb/pp

NA49 preliminary

pPb/pp

Cronin


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elliptic flow v2 in Pb+Pb collisions at 158AGeV

• blast wave fits ok• overprediction by pure hydro model• preliminary K0 unexpectedly low

KET = mT – m (A.Adare et al.,nucl-ex/0608033)

• reasonable scaling also at SPS• coalescence region not reached


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Changes of hadron production properties in central Pb+Pb collisions at the CERN SPS energies are not reproduced by models without onset of deconfinement at low SPS energies

stra

ngen

ess/

pion

slop

e of

pT sp

ectr

a

AGS SPS AGS SPS RHIC

1/4NN s


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Freeze-out parameters determined from hadron yields for central Pb+Pb collisions at the CERN SPS are close to

the predicted phase boundary between hadron gas and quark-gluon plasma

A critical point of stronglyinteracting matter is predicted by QCD. It may be discoveredas a maximum of fluctuations in a comprehensive energy

and system size scan at the CERN SPS

and low energy RHIC

baryochemical potential

tem

pera

ture

hadron gas analysis: F.Becattini et al., PRC73(2006)044905

lattice QCD results: Z.Fodor and S.Katz, JHEP 04(2004)050


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Event-by-event fluctuations of negative hadron multiplicity

• fluctuations measured at forward rapidity (1.1 < yπ < 2.6) where azimuthal acceptance is best

• number of projectile participants fixed by projectile spectator energy cut; no restriction on target participants • central collisions: fluctuations nearly Poissonian (independent emission)

• peripheral collisions: fluctuations exceed Poissonian

Pb+Pb at 158AGeV, 1.1 < yπ < 2.6

measure: ω = Var(n)/<n>


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Event-by-event fluctuations of negative hadron multiplicity

• rise due to effect of fluctuating target participants ?• reproduced by string models with string fusion (QGSM+fusion)

158AGeV

1.1 < yπ < 2.6

• fluctuations in central Pb+Pb small and nearly energy independent• trend in statistical models due to conservation laws

1.1 (1.0) < yπ < 2.6 (ybeam)

NA49 preliminary

centrality energy

L.Cunqueiro et al.,PRC69(2005)024907


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Event-by-event fluctuations of <pT> (negative hadrons)

• distributions of <pT> similar for real and mixed events

• no evidence for distinct event classes

• non-statistical (dynamical) fluctuations are small, < few %

1.1 < yπ < 2.6

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T

Ni

T T T Ti 1

Zp - <z

z p - <p > Z (p - <p > )

N

measure: ΦpT


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Event-by-event fluctuations of <pT> (negative hadrons)

increase for peripheral collisions effect of string fusion ?

NA49 preliminary

1.1 < yπ < 2.6

STAR158A GeV1.1 < yπ < 2.6

no significant change with energy for central Pb+Pb collisions

1.1 < yπ < 2.6

centrality energy


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The Event-by-Event K/π ratioB

eam

Ene

rgy

σ2dyn = σ2

data – σ2mixed

maximum likelihood fit for each event

NA49 preliminary

STAR

Fluctuations increase at lower energy effect of onset of deconfinement ?

M.Gorenstein et al.,PLB585(2004)237


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The Event-by-Event (p + p)/π ratioB

eam

Ene

rgy

The distribution of the E-by-E p/π ratiois narrower for data than mixed events. Effect of baryon resonance decay ?

NA49 preliminary


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Future PlansSearch for the QCD critical point in fluctuations → scan lower SPS energies and smaller size nuclei

Proposal CERN-SPSC-2006-034/P-330: under consideration at SPSC( upgraded NA49 detector )


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Backup Slides


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Pb+Pb collisions at top SPS energy

• Initial energy density exceeds the critical value predicted by lattice QCD ( ≈ 1 GeV / fm3 )

• Strong collective behavior– anisotropic and radial flow– transverse expansion of the matter droplet by factor 2

• Proposed signatures for deconfinement observed – strangeness enhancement– J/Ψ,Ψ’ yield suppression– di-lepton enhancement, ρ0 modification(circumstantial evidence for a new state of matter (2000)

Validate by a search for a threshold in the largest collision system (central Pb+Pb reactions)

SPS energy scan: 20, 30, 40, 80, 158 GeV/nucleon (√sNN = 6.3, 7.6, 8.7, 12.3, 17.3 GeV)

results from na49 at the cern sps

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na49 collaborationresults

na49 detectortarget

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winter worshop

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netbaryon distributions

baryon rapidity distributions

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