direct photon production from heavy ion collisionsbaeuchle/downloads/19_photons...direct photon...

Direct Photon Production from Heavy Ion

Collisions

Bjørn BauchleThe UrQMD Group (http://urqmd.org)

based on PRC 81 (2010) 044904and ongoing work

FIAS Frankfurt

Institutt for fysikk og teknologi, Universitetet i Bergen28/04-2010

Collaborators

The UrQMD-Group

Marcus Bleicher, Horst Stocker, Michael Mitrovski, Elvira Santini,Bjørn Bauchle, Thomas Lang, Jan Steinheimer-Froschauer,Gunnar Graf

Sponsors

HGS-HIReHelmholtz Graduate School for Hadron and Ion Research

Introduction

Model

Photon Spectra at SPS

Results for FAIR

Results for RHIC

Summary & Outlook

Introduction Model Photon Spectra at SPS Results for FAIR Results for RHIC Summary & Outlook

Why Heavy Ion Collisions?

History of the Universe

Hot nuclear matter present until ≈ 1 µs after Big Bang

Direct observation of Big Bangonly until ≈ 300ka after BB

Bjørn Bauchle, FIAS Direct Photon Production from Heavy Ion Collisions Bergen, 28/04-10 4 / 43



History of the Universe

Hot nuclear matter present until ≈ 1 µs after Big Bang

No Problem:Recreate parts of Big Bang inthe lab!

Direct observation of Big Bangonly until ≈ 300ka after BB




T

µB922 MeVHadron Gas

Quark Gluon Plasma

ColorSuper

Conductor

Liquid/Gas

?◮ Collective behaviour of

QCD-Matter

◮ Explore Phase Diagram




T

µB922 MeVHadron Gas

Quark Gluon Plasma

ColorSuper

Conductor

Liquid/Gas

µB = 0, T ≈ 170 MeV: Cross-over

µB =?, T =?:

Critical End Point?

high µB

1st Order PT?

◮ Collective behaviour ofQCD-Matter

◮ Explore Phase Diagram:◮ Critical Point◮ Deconfinement◮ Chiral Restauration

◮ Get thereby smashing nuclei!



Why direct photons?

◮ Interesting scattering infireball



Why direct photons?


◮ Hadronic decayproducts. . .



Why direct photons?



◮ . . . rescatter. Informationlost.



Why direct photons?




◮ Photons do not rescatter→ keep information!



Why direct photons?




◮ Photons do not rescatter→ keep information!

◮ Plenty uninterestingphoton sources



Photon Sources in A+A



Direct Photon Experiments◮ Helios, WA 80, CERES (SPS) 1 — upper limits

◮ WA 93 (SPS) and STAR (RHIC) — no results (yet)

◮ WA 982 — first measurements at SPS

◮ PHENIX3 (RHIC) — various results

1Helios: Z. Phys. C 46, 369 (1990); WA 80: Z. Phys. C 51, 1 (1991); PRL 76, 3506 (1996);CERES: Z. Phys. C 71, 571 (1996)

2PRL 85, 3595 (2000)3e.g. PRL 94, 232301 (2005)



Direct Photon Experiments◮ Helios, WA 80, CERES (SPS) 1 — upper limits

◮ WA 93 (SPS) and STAR (RHIC) — no results (yet)

◮ WA 982 — first measurements at SPS

◮ PHENIX3 (RHIC) — various results

◮ Photons from hadronic decays make ∼ 97 % of all photons

◮ Uncertainties in hadron yield significantly changedirect photon yield

◮ EM-Calorimeters expensive, coverage therefore usually small

1Helios: Z. Phys. C 46, 369 (1990); WA 80: Z. Phys. C 51, 1 (1991); PRL 76, 3506 (1996);CERES: Z. Phys. C 71, 571 (1996)

2PRL 85, 3595 (2000)3e.g. PRL 94, 232301 (2005)



Theory: Underlying Models

pQCD Good for high p⊥, good for pp. In AA, nucleareffects can be parametrized4. Important at RHIC-and LHC-energies, what about SPS?

Hydro Good for thermalized systems, phase transitions.Input: Parametrized Rates E dN

d3pd4x(p,T , µ)

Application: numerical challenge5!

Transport Good for not-too-dense systems.Input: Cross-sections dσ

dt(s, t, ρ)

Application: straight-forward6

4E.g. Aurenche, Fontannaz et. al, PRD 73, 094007 (2006)5Turbide et al., PRC 69, 014903 (2004); Turbide et al., PRC 72, 014906 (2005); Liu et al., arXiv:0712.3612

[hep-ph]; Vitev et al. arXiv:0804.3805 [hep-ph]; Haglin, PRC 50, 1688 (1994); Haglin, JPG 30, L27 (2004), BB et

al., PRC 81 (2010) 0449046Dumitru et al., PRC 57, 3271 (1998); Huovinen et al., PRC 66, 014903 (2002); Li et al.

arXiv:nucl-th/9712048; BB et al., PRC 81 (2010) 044904



Theory: Unknown processes

◮ Branching ratios of many processes not known, e.g. a1 → γπ.PDG says ”seen”.What of it? Data from Zielinski7 show odd behaviour;this work: take calculations from Xiong8. Difference ∼ factor2.5 — may make a big difference!

7Zielinski et al., PRL 52, 1195 (1984)8Xiong, Shuryak and Brown, PRD 46, 3798 (1992)





◮ Which channels are implemented? Bremsstrahlung?Hadronic decays?






◮ Which channels are implemented? Bremsstrahlung?Hadronic decays?

◮ Hadronic decays are not in data! But: Do we believe that?




UrQMD

UrQMD

Ultra-Relativistic QuantumMolecular Dynamics

◮ Classical propagation of hadrons

◮ QM scattering cross-sections

◮ Cross-sections fitted to data orcalculated via detailed balance orparametrized via additive quark model

◮ All hadrons from PDG up to m = 2.2 GeV

◮ Full microscopic collision history availavble

◮ Version 3.3 out now! Go to http://urqmd.org/



UrQMD+Hydro (new in u3.3)

◮ High-density part of evolution optionally substituted byideal hydrodynamics

◮ Macroscopic description

◮ Microscopic initial state from transport (UrQMD)mapped to densities and flow velocities

◮ Hydro propagation with variable Equation of State

◮ Back to transport when ǫ < 5ǫ0 in all cells. . .◮ . . . seperately for all z (gradual)◮ . . . in complete system (isochronous)

◮ Rescatterings and decays with UrQMD

◮ See also Petersen et al. Phys. Rev. C 78 (2008) 044901



Equations of State

Hadron Gas

◮ Includes all particles from UrQMD

◮ no phase transition

Bag Model

◮ MIT Bag Model

◮ First Order Phase Transition at TC = 170 MeV

Chiral Model

◮ Chirally restored phase

◮ First Order PT, Cross-over and CEP



Photons from the modelBoth models

π + π → γ + ρ, π + ρ → γ + π

Only Cascade

Cross-sections from Kapusta, Lichard & Seibert (PRD 44 (1991) 2774)

π + π → γ + η, π + η → γ + π, π + π → γ + γCross-sections known, applied to every scattering

Only Hydro

Parametrizations from Turbide, Rapp & Gale (PRC 69 (2004) 014903)

π + K ∗ → γ + K , π + K → γ + K ∗,ρ + K → γ + K , K + K ∗ → γ + π

Thermal rates known, applied to every cell



Photons from the modelCascade

◮ Emitted photons may be only a fraction of a photon

◮ Each collision and channel: 100 photons produced withdifferent mandelstam t-values and appropiate weightN =

dσγ

dt∆t/σtot ⇒ less events calculated, better statistics

Hydro

◮ Take care of proper Lorentz-Transformation(mind Cooper-Frye):

◮ Generate random pµuµ according to thermal rate, thengenerate ~p so that it yields desired pµuµ.

◮ For all cells, every implemented rate: one photon-information

(with weight N =∫ d3p

E∆V ∆t E dR

d3p) is created.



Check: Rates from Transport

10−12

10−10

10−8

10−6

10−4

0.01

0 0.5 1 1.5 2 2.5 3

1 2π

1 EdR

dE

[GeV

−2

fm−

4]

E [GeV]

T = 150 MeVBox: V = (20 fm)3,

π/ρ/a1-gas

Box-calculations (UrQMD)Hydro-rates (Turbide et al.)

ππ → γρπρ → γπ

r b

r

b

r

r

r

r

rr

rr

rr

rr

rr

rr

rr

rr

rr

rr

rr

b

b

b

bb b b b

bb

bb

bb

bb

bb

bb

bb

bb

bb

bb

b



Stages: HG-EoS

Only using common channels:ππ → γρπρ → γπ (incl. a1)

Pb+Pb @ Elab = 158A GeVb < 4.5 fm, |ycm| < 0.5

preliminary

10−8

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p(G

eV−

2)

p⊥ (GeV)

All γ from hybridPure UrQMD ×

××××××××××××××××××××××××××××××××××××××××××××××

◮ Hard photons only from before hydro-evolution

◮ Similar yield in hybrid and cascade mode!



Stages: HG-EoS



preliminary

10−8

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p(G

eV−

2)

p⊥ (GeV)

Transport-γ before hydro

Pure UrQMD ×

××××××××××××××××××××××××××××××××××××××××××××××





Stages: HG-EoS



preliminary

10−8

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p(G

eV−

2)

p⊥ (GeV)

Transport-γ before hydroHydro-γ

Pure UrQMD ×

××××××××××××××××××××××××××××××××××××××××××××××





Stages: HG-EoS



preliminary

10−8

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p(G

eV−

2)

p⊥ (GeV)


Transport-γ after hydro

Pure UrQMD ×

××××××××××××××××××××××××××××××××××××××××××××××





Stages: HG-EoS



preliminary

10−8

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p(G

eV−

2)

p⊥ (GeV)


Transport-γ after hydroAll γ from hybrid

Pure UrQMD ×

××××××××××××××××××××××××××××××××××××××××××××××





Stages: Cascade

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p

[GeV

−2]

p⊥ [GeV]

complete cascadeinitial stage

intermediate stagefinal stage

UrQMDPb+Pb 158 AGeV

b < 4.5 fm, |yc.m.| < 0.5

◮ Split by time



Stages: BM-EoS

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p

[GeV

−2]

p⊥ [GeV]

complete hybridinitial stage

intermediate stagefinal stage

Hybrid, Bagmodel EoSPb+Pb 158 AGeV

b < 4.5 fm, |yc.m.| < 0.5

◮ Hydro enhanced!



Different EoS vs. data

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p

[GeV

−2]

p⊥ [GeV]

WA98 Pb+Pb 158 AGeV rs

rs

rs rs rs rsrs rs rs

rsrs rs

rsrs rs

rs rs

rsrs rs rs rs

rs

rs

rs

rs

rs

rs

rs

Pure UrQMD ××××××××××××××××××××××××××××××××××××××××××××××

Hybrid, Hadron gas EoSHybrid, Bag Model EoS

Pb+Pb 158 AGeVb < 4.5 fm

|yc.m.| < 0.5

◮ All models undershoot data, but no pQCD here!Bjørn Bauchle, FIAS Direct Photon Production from Heavy Ion Collisions Bergen, 28/04-10 20 / 43


Diff. EoS, pQCD vs. data

10−7

10−6

10−5

10−4

0.001

0.01

1.5 2 2.5 3 3.5 4 4.5

EdN

d3p

[GeV

−2]

p⊥ [GeV]

WA98 Pb+Pb 158 AGeV rsrsrs rs

rsrsrsrsrs

rsrs

rsrs

rs

rs rs rsrs

rs

rs

rs

rs

rs

rs

rs

UrQMD + pQCD ×××××××××××××××××××××××××××××××

Hybrid + pQCD, HG EoSHybrid + pQCD, BM EoS

pQCD: Turbide et al.Pb+Pb 158 AGeV

b < 4.5 fm|yc.m.| < 0.5

◮ Very good agreement for all three models



Photon Sources: Cascade

b < 4.5 fm, |ycm| < 0.5UrQMD

preliminary

10−8

10−7

10−6

10−5

10−4

10−3

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p(G

eV−

2)

p⊥ (GeV)

WA98 Pb+Pb 158 AGeV

rs

rs rs rs rsrs rs rs

rsrs rs

rsrs rs

rs rs

rsrs rs rs rs

rs

rs

rsrs

rs

rs

rs

rs

Processes with ηππ → γγ




b < 4.5 fm, |ycm| < 0.5UrQMD

preliminary

10−8

10−7

10−6

10−5

10−4

10−3

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p(G

eV−

2)

p⊥ (GeV)

WA98 Pb+Pb 158 AGeV

rs

rs rs rs rsrs rs rs

rsrs rs

rsrs rs

rs rs

rsrs rs rs rs

rs

rs

rsrs

rs

rs

rs

rs

ππ → γρProcesses with η

ππ → γγ




b < 4.5 fm, |ycm| < 0.5UrQMD

preliminary

10−8

10−7

10−6

10−5

10−4

10−3

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p(G

eV−

2)

p⊥ (GeV)

WA98 Pb+Pb 158 AGeV

rs

rs rs rs rsrs rs rs

rsrs rs

rsrs rs

rs rs

rsrs rs rs rs

rs

rs

rsrs

rs

rs

rs

rs

allπρ → a1 → γπ

πρ → γπππ → γρ

Processes with ηππ → γγ

◮ Dominant contribution from π + ρ → γ + π (incl. a1)

◮ Hard π + π-scatterings make power-law tail at high p⊥



Photon Sources: Hybrid

b < 4.5 fm, |ycm| < 0.5UrQMD+Hydro

preliminary

10−8

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p(G

eV−

2)

p⊥ (GeV)

WA98 Pb+Pb 158 AGeV

rs

rs rs rs rsrs rs rs

rsrs rs

rsrs rs

rs rs

rsrs rs rs rs

rs

rs

rs

rs

rs

rs

rs

rs

Processes with ηProcesses with K or K ∗

ππ → γγ





preliminary

10−8

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p(G

eV−

2)

p⊥ (GeV)

WA98 Pb+Pb 158 AGeV

rs

rs rs rs rsrs rs rs

rsrs rs

rsrs rs

rs rs

rsrs rs rs rs

rs

rs

rs

rs

rs

rs

rs

rs

ππ → γρProcesses with η

Processes with K or K ∗ππ → γγ





preliminary

10−8

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p(G

eV−

2)

p⊥ (GeV)

WA98 Pb+Pb 158 AGeV

rs

rs rs rs rsrs rs rs

rsrs rs

rsrs rs

rs rs

rsrs rs rs rs

rs

rs

rs

rs

rs

rs

rs

rs

allπρ → γπππ → γρ

Processes with ηProcesses with K or K ∗

ππ → γγ

◮ Also, dominant contribution from π + ρ → γ + π

◮ Very similar yield as in cascade mode!



Treatment of Strings

◮ High energies: UrQMD excites strings

◮ String ends (Quarks or Diquarks) have lower ×-sect

◮ What if they are excluded from γ-production?

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Pb+Pb 158 AGeVb < 4.5 fm, |yc.m.| < 0.5

EdN

d3p

[GeV

−2]

p⊥ [GeV]

UrQMD w/o string endsUrQMD with string ends

pQCD-photons (Gale)pQCD-photons (Turbide et al.)



ρ on mass peak

◮ Scattering withincoming ρ:m2

ρ= pµpµ

from UrQMD

◮ Scattering→ γρ: mρ =770 MeV?

◮ Maybe mρ

distributed acc.toBreit-Wigner

0.01

0.1

1

10

100

103 0 0.2 0.4 0.6 0.8 1

EdN

d3p

[GeV

−2]

p⊥ [GeV]

UrQMDPb+Pb 158 AGeV

b < 4.5 fm|yc.m.| < 0.5

mρ fixedmρ Breit-Wigner

π±π0 → γρ±

π±π∓ → γρ0 × 10

0

0.2

0 0.2 0.4 0.6 0.8 1(on-o

ff)/

off

p⊥ [GeV]

π±π0 → γρ±π±π∓ → γρ0



Flattening at high p⊥

10−6

10−5

10−4

10−3

0.01

0.1

10.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p

[GeV

−2]

p⊥ [GeV] sumπρ → γπππ → γρ

Processes inv. η

0

4

8

12

16

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

〈t em

issio

n〉[

fm]

p⊥ [GeV]

Pb+Pb @ 158 AGeVb < 4.5 fm|ycm| < 0.5

UrQMD

◮ Flattening at high p⊥ corresponds to earlier emission timesBjørn Bauchle, FIAS Direct Photon Production from Heavy Ion Collisions Bergen, 28/04-10 26 / 43


Flattening at high p⊥

10−6

10−5

10−4

10−3

0.01

0.1

10.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p

[GeV

−2]

p⊥ [GeV] sumπρ → γπππ → γρ

Processes inv. η

0

4

8

12

16

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

〈t em

issio

n〉[

fm]

p⊥ [GeV]

Pb+Pb @ 158 AGeVb < 4.5 fm|ycm| < 0.5

UrQMD 10−9

10−7

10−5

10−3

0.1

0 2 4 6

EdN

d3p

[GeV

−2]

pγ

⊥ [GeV]

◮ Flattening at high p⊥ corresponds to earlier emission timesBjørn Bauchle, FIAS Direct Photon Production from Heavy Ion Collisions Bergen, 28/04-10 26 / 43


A closer look at high p⊥-photons

√scoll

10−8

10−6

10−4

0.01

0 2 4 6 8 10 12 14dN

d√

s(G

eV−

1)

√s (GeV)

All photons

pγ

⊥10−9

10−7

10−5

10−3

0.1

0 1 2 3 4 5 6 7

EdN

d3p

(GeV

−2)

p⊥ (GeV)

All photons

pure UrQMD



A closer look at high p⊥-photons

√scoll

10−8

10−6

10−4

0.01

0 2 4 6 8 10 12 14dN

d√

s(G

eV−

1)

√s (GeV)

All photonsγ with p⊥ > 3 GeV

pγ

⊥10−9

10−7

10−5

10−3

0.1

0 1 2 3 4 5 6 7

EdN

d3p

(GeV

−2)

p⊥ (GeV)

All photonsγ from collisions with

√s > 4 GeV

pure UrQMD

◮ Most photons at high p⊥ come from high-√

s-collisions

◮ Hadronic treatment questionable



Emission times

02

468

1012

14161820

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

〈t em

issio

n〉[

fm]

p⊥ [GeV]

Pb+Pb @ 158 AGeVb < 4.5 fm

|yc.m.| < 0.5UrQMD

allπρ → γπππ → γρ

Processes with η and ππ → γγ

◮ Initial flash

◮ bulk emissionlater

◮ very long tail atintermediate p⊥

〈t1〉, 〈t2〉〈t3〉

0

1

2

3

4

0 5 10 15 20

dN dt

[10−

3fm

−1]

t [fm]

p⊥ = 1 − 1.5 GeVp⊥ = 2 − 2.5 GeVp⊥ = 3 − 3.5 GeV

Only πρ → γπ

×10 ×100



Future: FAIR

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3

EdN

d3p

[GeV

−2]

p⊥ [GeV]

Pure UrQMD ×××

×××××××××××××××××××××××××××××

Hybrid, Hadron gas EoSHybrid, Bag Model EoS

Hybrid, Chiral EoS

U+U @ 45 AGeVmin. bias

|ycm| < 0.5

preliminary

Same picture at FAIR:Hadronic models similar, Bag Model enhanced.Chiral EoS shows higher Temperatur



Contributions @ FAIR

10−7

10−6

10−5

10−4

10−3

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3

EdN

d3p

[GeV

−2]

p⊥ [GeV]

sumπρ → γπ

ππ → γXπη → γπ

U+U @ 45 AGeVmin. bias

|ycm| < 0.5

UrQMD preliminary

No surprises from channel-differential investigation



10−22

10−20

10−18

10−16

10−14

10−12

10−10

10−8

10−6

10−4

10−2

100

102

0 2 4 6 8 10 12

EdN

d3p

[GeV

−2]

p⊥ [GeV]

Comparison PHENIX @ RHIC vs. UrQMDPHENIX-Data

UrQMD-calculations

rs

rs

rs

rs rs rs rs rs rs rs rs rs rs rs rs Min. Bias ×103

rs

rs

rsrs rs

rs rs rsrs rs

rs rs rs rsrs rs 0-10% ×100

rs

rs

rsrs rs

rs rs rsrs rs rs rs rs rs rs rs 10-20% ×10−2

rsrs

rs rs

rs

rs rs rsrs rs rs rs rs rs rs rs 20-30% ×10−4

rs rs

rs

rs rs rsrs rs rs

rs rsrs rs rs

rs rs 30-40% ×10−6rs

rs rsrs rs rs

rsrs rs

rsrs

rs 40-50% ×10−8rsrs rs

rs rs rs

rs rs rs 50-60% ×10−10

rs

rsrs

rs

rs rs rsrs 60-92% ×10−12



PHENIX w/ HG-EoS

1 2 3 4 5 610−6

10−5

10−4

10−3

10−2

10−1

100

101

102

103

EdN

d3p

[GeV

−2]

p⊥ [GeV]

PHENIX-datapure UrQMD-calculations

hybrid-calculations〈Ncoll〉-scaled NLO pQCDAu+Au,

√sNN = 200 GeV

rs

×rs

rs

rsrs

rsrs

×××

×× × × × ×

Min. Bias×104

rs

rs

rs

rs rs

rs rsrs

×××

×× × × × ×

0-10%


Summary

◮ UrQMD and UrQMD+Hydro ideal for investigating photons

◮ Fit data at SPS, pQCD needed

◮ pQCD negligible at FAIR

◮ Hadronic Sources not sufficient at RHIC

◮ Hydro stage with QGP: largely enhanced emission

◮ πρ dominant (hadronic) contribution at intermediate p⊥◮ Exponential slope from non-thermalized system possible!

◮ High-p⊥ from high-√

s

Outlook

◮ Bag Model, Chiral EoS for RHIC

◮ Investigate Parameter thydrostart, εcrit

◮ Investigate transition scenario (gradual vs. isochronous)

◮ Different systems: Au+Au, Cu+Cu @√sNN = 130, 62.4, (200) GeV, U+U @ Elab = 11, 30 GeV

Backup-Slides

Photon emission ×-sections

10−4

10−3

0.01

0.1

1

10

100

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

2mπ mη+mπ

mρ+mπ

ma1

σ[m

b]

√s [GeV]

π±π∓ → γρ0

π±π0 → γρ±

π±π∓ → γηπ±η → γπ±

π±π∓ → γγ

mρ Breit-Wigner

mρ fixed

10−4

10−3

0.01

0.1

1

10

100

0.8 1 1.2 1.4 1.6 1.8 2

mρ + mπ ma1

σ[m

b]

√s [GeV]

π±ρ0 → γπ±

π±ρ∓ → γπ0

π0ρ± → γπ±

πρ → a1 → γπ


Photon emission rates

10−20

10−15

10−10

10−5

1

0 0.5 1 1.5 2 2.5 3

EdR

d3p

[GeV

−2fm

−4]

E [GeV]

T = 170 MeV

ππ → γρ (×1000)

πρ → γπ (×1000)

πK → γK∗

πK∗ → γK

ρK → γK (×10−6)

K∗K → γπ (×10−6)


Previous Work with UrQMD

10−6

10−5

10−4

10−3

0.01

0.1

1 1.5 2 2.5 3

EdN

d3p

[GeV

−2]

p⊥ [GeV]

Dumitru et al. (UrQMD v1.0)UrQMD v1.3, this workUrQMD v2.3, this work


Initial Temperature ProfileBM-EoS HG-EoS

250

200

150

10050

-10 -5 0 5 10 12x [fm]

-10

-5

0

5

10

12

y[fm

]


Total cross-section in UrQMD

05

10152025303540

1 10

σ[m

barn

]

√s [GeV]

σ(π+π− → strings )σ(π+π− → resonance )

σ(π+π− → hard scattering)


Inclusion of PYTHIA

10−7

10−6

10−5

10−4

10−3

0.01

0.1

1 1.5 2 2.5 3 3.5 4 4.5 5

EdN

d3p

[GeV

−2]

p⊥ [GeV]

with PYTHIAwithout PYTHIAUrQMD p + p 158 GeV

all charged particles


Why not PYTHIA for pQCD

10−7

10−6

10−5

10−4

0.001

0.01

0.1

1

10

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

EdN

d3p

[GeV

−2]

p⊥ [GeV]

WA98 Pb+Pb 158 AGeV

rs

rs rsrs rs

rs rs rsrsrsrsrsrs rs

rs rs

rsrs rs rs rs

rs

rs

rs

rs

rs

rs

rs

rs

UrQMD w PYTHIAPYTHIA

UrQMD w/o PYTHIA


Total cross-section

05

10152025303540

1 10

σ[m

barn

]

√s [GeV]




direct photon production from heavy ion collisionsbaeuchle/downloads/19_photons...direct photon...

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