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L , L, X, X, X 1530 , X 1530 , W, W, p+ , p -, K+,K-,p, p, n. Inclusive production of hyperons, as well as of pions, charged kaons, protons, anti-protons and neutrons in p+p collisions at 158 GeV/c beam momentum. Tome Anticic for the NA49 collaboration. ICHEP, Paris, July 2010.

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tome anticic for the na49 collaboration

L, L,X, X, X1530 ,X1530,W, W,

p+, p-, K+,K-,p, p, n

Inclusive production of hyperons, as well as of pions, charged kaons, protons, anti-protons and neutrons in p+p collisions at 158 GeV/c beam momentum

Tome Anticic

for the NA49 collaboration

  • ICHEP, Paris, July 2010
the na49 detector
The NA49 detector

Hadron spectrometer

Four TPCs; two in the B field and two others outside;

for a precise measurement of p and dE/dx

Large acceptance: ≈50%

High momentum resolution

Good particle identification by dE/dx, decay topology, invariant mass

  • Various evidence points to existence of QGP, and to existence of the onset of deconfinement at energies between
  • However, a good understanding of the underlying p-p and p-A process necessary to support this conclusion or to perhaps give alternative explanations
  • NA49 experiment unique in providing one detector for p-p, p-A, and A-A analysis, by changing targets and incoming beam

√sNN = 6.3 – 17.3 GeV

NA49 covers forward hemisphere; because of the symmetry of p+p this allows extraction of 4p integrated multiplicities

PID by dE/dx

tome.anticic@cern.ch

hyperons
Hyperons
  • Strange particles do not exist in colliding protons, and as such are excellent probes of the underlying physics of the production mechanism
  • Strangeness enhancement an indication of QGP formation
  • Models sensitive to hyperon production at SPS energies
  • 8.2 M p-p events before selection

X

L

Mid rap

Mid rap

  • 77500 L
  • 14200 L
  • 3800 X
  • 1200 X
  • 550 X1530
  • 135 X1530
  • 70 W
  • 10 W

X(1530)

Mid rap

W

W

All

Mid rap

First clear signal at SPS

energies in p-p collisions

tome.anticic@cern.ch

slide4
L, L

“ Temperature”

L

rapidity

rapidity

Transverse momentum

L

Models often do not match data behavior

tome.anticic@cern.ch

slide5
X,X

“ Temperature”

X

rapidity

rapidity

Transverse momentum

X

Models often do not match data behavior

tome.anticic@cern.ch

transverse and long distribution x 1530 only
Transverse and long. distribution: X1530 only

-0.75 < rap < 0.75

rapidity

tome.anticic@cern.ch

transverse and long distributions w only
Transverse and long. distributions: W only

-0.75 < rap < 0.75

rapidity

tome.anticic@cern.ch

anti baryon baryon ratio
Anti baryon/baryon ratio

String

models

Anti baryon to baryon ratio at y=0 as a function of strangeness

X/X = 0.8 -1.2

W/W = 1.6 - 1.9

String models predict:

tome.anticic@cern.ch

strangeness enhancement
Strangeness enhancement

NA49 data.

Filled symbols are

central trigger

Open symbols

STAR

Open symbols

NA57

Compare to STAR

Compare to NA57

tome.anticic@cern.ch

pions kaons protons neutrons
Pions, kaons, protons, neutrons
  • 6.4 M inelastic p-p events (4.8 M after event cuts)
  • Can not use topology for PID, so excellent knowledge of dE/dx required
  • To mimimize systematic errors on this high statistics sample, also bin size corrections employed
  • Results corrected for feeddown from hyperon weak decays
  • Detailed comparison with data from other experiements and energies at ISR, SIS, Serpukhov, RHIC, Fermilab, …
  • Detailed study of particle ratios

C.Alt et al.,EPJC 45 (2006) 343

arXiv:1004.1889v

T.Anticic et al.,EPJC 65 (2010) 9

tome.anticic@cern.ch

slide11
p+ p-
  • 0 to 2 GeV/c in transverse momentum
  • 0 to 0.85 in Feynman x

“temperature” a function of transverse mass

p-

p+

  • Systematic and statistical uncertainties well below 5%
  • Rich substructure of data (also in the kaon and proton data) – indication that particles are produced via intermediate higher mass resonances
    • profound consequences for theunderstanding of particle production in the non-perturbative sector of QCD

tome.anticic@cern.ch

slide12
K+, K-
  • 0 to 1.7 GeV/c in transverse momentum
  • 0 to 0.5 in Feynman x

Integrated data

“temperature” a function of transverse mass

Feynman x

Transverse momentum

based on high precision NA49 results an internally consistent picture of kaon production was established in the energy range 3 < sqrts < 1800 GeV

tome.anticic@cern.ch

protons antiprotons neutrons
Protons, antiprotons, neutrons

p

p

p

p

p

p

Integrated data

n

Feynman x

Transverse momentum

Feynman x

  • 0 to 1.9 GeV/c (0 to 1.5 GeV/c) in transverse momentum
  • -0.05to 0.95 (-0.05 to 0.4) in Feynman x for protons (anti-protons), respectively
  • pT integratedneutron cross sections: 0.1 to 0.9 in Feynman x

tome.anticic@cern.ch

yields per inelastic event
Yields per inelastic event

NA49

VENUS

Fritiof

EPOS

URQMD

HSD

Hijing1.5

Hijing1.7

Stat models A/B

p+

p-

K+

K-

p

p

L

L

X

X

X1530

W

Significant discrepancies for most models/particles

tome.anticic@cern.ch

conclusions future
Conclusions/Future
  • High quality double differential data for hyperons, pions, kaons, protons
  • basis for interpretation of particle production mechanisms in pp as well as their implication for pA and AA reactions
  • important new constraint for string models
  • detailed study of hyperon production in pA underway
  • In the near future will study an order of magnitude more data at NA61, the upgrade of NA49
    • study of the onset of deconfinement and search for the critical point of strongly interacting matter 

tome.anticic@cern.ch