Heavy ion physics at nica simulations g musulmanbekov v toneev and the physics group on nica
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Heavy Ion Physics at NICA Simulations G.Musulmanbekov, V. Toneev and the Physics Group on NICA PowerPoint PPT Presentation


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Heavy Ion Physics at NICA Simulations G.Musulmanbekov, V. Toneev and the Physics Group on NICA. Search for signals of Phase Transition in Au + Au collisions at √s NN = 3 – 9 GeV Motivation

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Heavy Ion Physics at NICA Simulations G.Musulmanbekov, V. Toneev and the Physics Group on NICA

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Heavy Ion Physics at NICASimulationsG.Musulmanbekov, V. Toneevand the Physics Group on NICA


  • Search for signals of Phase Transition in Au + Au collisions at √sNN = 3 – 9 GeV

  • Motivation

  • The main goal of the NICA experiment is to study the behaviour of nuclear matter in vicinity of the QCD critical endpoint.

  • To extract information on the equation-of-state of baryonic matter at high densities.

  • Search for signals of Phase Transition in Au + Au collisions

  • at √sNN = 3 – 9 GeV


  • Search for signals of Phase Transition in Au + Au collisions at √sNN = 3 – 9 GeV

  • Signatures of Possibile Phase Transition :

    • Strange particle enhancement

    • Hard spectrum of strange mesons

    • Charmonium suppression

    • Dielectron mass spectrum enhancement at the range 0.2 – 0.6 GeV/c


  • Search for signals of Phase Transition in Au + Au collisions at √sNN = 3 – 9 GeV

  • Observables :

  • Global characteristics of identified hadrons, including strange baryons

  • Strange to non-strange particles ratio

  • Transverse momentum spectra

  • Fluctuations in multiplicity and transverse momenta

  • Directed and elliptic flows

  • Particle correlations (femtoscopy, HBT correlations)

  • Dilepton spectra


  • Search for signals of Phase Transition in Au + Au collisions at √sNN = 3 – 9 GeV

  • Simulation Tools :

  • UrQMD 1.3, UrQMD 2.2

    • 104 central events at 3, 3.8, 5, 7, 9 GeV

    • 105 min bias events at 3, 3.8, 5, 7, 9 GeV

  • FastMC

    • 104 central events at 3, 5, 7, 9 GeV

  • PLUTO

    • 106 central events at 3, 5, 7, 9 GeV


Mean multiplicities in Au-Au collisions Simulated by UrQMD min.bias events 


Mean multiplicities in Au-Au collisions Simulated by UrQMD central collisions (b ≤ 3 fm) 


Mean multiplicities in Au-Au collisions Simulated by UrQMD central collisions (b ≤ 3 fm) 


Mean multiplicities in Au-Au collisions Simulated by UrQMD central collisions (b ≤ 3 fm) 


Simulated charged multiplicity distributionsin central collisions (b < 3fm)


Simulated charged pseudorapidity distributions in central collisions (b < 3fm)


Simulated charged pseudorapidity distributions in central collisions (b < 3fm)

MPD

-2 < η < 2


Simulated charged pseudorapidity distributions in central collisions (b < 3fm)

MPD

-1 < η < 1


Strange Baryons Yield

Table: Marked hyperons are accessible through their decays into charged hadrons


Accessible Hyperons


Accessible Hyperons

Λ → pπ-

Ξ- → Λπ- → pπ- π-

Ω- → ΛK- → pK- π-


Strange to non-Strange ratios in central collisions“Horn” Effect

<π- >/<π+>

Au+Au/Pb+Pb, central

<K+ >/<π+>

Au+Au/Pb+Pb, central


Strange to non-Strange ratios in central collisions“Horn” Effect


Strange to nonStrange ratios in central collisions


Strange to nonStrange ratios in central collisions


Strange to nonStrange ratios in central collisions


Transverse Mass Spectra of Mesonsin central collisions

T – inverse slope


Transverse Mass Spectra of Mesonsin central collisions


Transverse Mass Spectra of Mesonsin central collisions


Scaled multiplicity variances

ω (h+)

ω (h-)

ω (hch)


Scaled multiplicity variancesNA49 results

NA49 result:

Measured scaled variances are close to the Poisson one – close to 1!

No sign of increased fluctuations as expected for a freezeout

near the critical point of strongly interacting matter was observed.


Transverse momentum fluctuations

To exclude trivial fluctuations from consideration the following variable is used:

For the system of independently emitted particles (no inter-particle

correlations) Фpt goes to zero.


Directed flow v1 & elliptic flow v2

z

x

Non-central Au+Au collisions:

Interactions between constituents leads to a pressure gradients => spartial asymmetry is converted in asymmetry in momentum space => collective flows

- directed flow

V2>0 indicates in-plane emission of particles

V2<0 corresponds to out-of-plane emission (squeeze-out perpendicular to the reaction plane)

- elliptic flow


Direct flowAu + Au collisions at √sNN = 7GeV, b = 5 – 9 fm


Direct flow slopeCollision Energy Dependence Au + Au, b = 5 – 9 fm


Elliptic flowAu + Au collisions at √sNN = 7GeV, b = 5 fm


Elliptic flowCollision Energy Dependence Au+Au/Pb+Pb, b = 5 – 9 fm


HBT interferometry

Rlong

p1

x1

p2

qside

Rside

x2

qout

qlong

Rout

  • HBT: Quantum interference between identical particles

2

C (q)

Gaussian model (3-d):

1

  • Final-state effects (Coulomb, strong) also can cause correlations, need to be accounted for

q (GeV/c)

  • Two-particle interferometry: p-space separation  space-time separation

Sergey Panitkin


HBT interferometry


HBT interferometry


HBT interferometry


Dilepton Spectra


Dilepton Spectra


Dilepton Spectra


Dilepton Spectra


Dilepton Spectra


Conclusions

New simulation codes which take into accountphase transitions of deconfinement and/or chiral symmetry restoration are needed.


Thank you!


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