Photon Production in a Hadronic Transport Approach

Transcription

1 Photon Production in a Hadronic Transport Approach Niklas Ehlert in collaboration with: Juan Torres-Rincon, Janus Weil and Hannah Petersen Transport Meeting, July 12, 2016

2 Outline Introduction and motivation Photon production: a simple mesonic system Direct photons in SMASH Photon production in equilibrium Summary Outlook July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 2

3 Probing the QCD phase diagram (Copyright: GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt/Germany) July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 3

4 by: S.A. Bass photons background direct photons decay photons prompt photons thermal photons bremsstrahlung July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 4

5 Direct photons - theoretical predictions undershoot measured spectrum and flow - maybe not dominated by early hot QGP? A. Adare et al. [PHENIX Collaboration], arxiv: [nucl-ex]. July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 5

6 Photons from a hadron gas - simple hadron resonance gas - only pi-, rho- and eta-mesons - evaluated via Scalar Field Theory [KAP91] July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 6

7 example: Deriving cross sections from scalar field theory July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 7

8 Total cross section comparison July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 8

9 Mass dependence of initial rho cross sections July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 9

10 Width dependence of final rho cross sections [WEIL16], [BAU10] July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 10

11 SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) In the following: box simulations with pions, rhos and etas thermal and chemical equilibrium box sizes: 10³ to 40³ fm³ temperature: 100 to 200 MeV July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 11

12 Perturbative photon production 1. check for collisions: 2. determine s and p cm 3. sample outgoing mass, find limits for Mandelstam t from effective masses 4. sample t according to dσ (s, t) and calculate θ dt 5. get φ from uniform distribution 6. include weighting factor: 7. boost to initial frame July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 12

13 Basic tests July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 13

14 Time (in)dependence July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 14

15 Volume (in)dependence July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 15

16 Average photon energy vs. s July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 16

17 Thermal photon rates [KAP91], [TUR13] July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 17

18 Suppression of: July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 18

19 Suppression of: July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 19

20 Temperature scaling July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 20

21 Conclusion thermal direct photon production from a simple mesonic system has been implemented successfully in SMASH Outlook add several other production channels calculate p T -spectra for very low p T merge with hybrid-hydro model calculate flow and other observables compare to experimental data July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 21

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23 Sources [BAU10]: Björn Bäuchle, Direct Photons in Heavy-Ion Collisions, PHD Thesis, Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany, September 2010 [KAP91]: J. I. Kapusta, P. Lichard and D. Seibert, High-energy photons from quark gluon plasma versus hot hadronic gas, Nucl. Phys. A 544, 485C (1992). doi: / (92)90603-h [NAD92]: H. Nadeau, J. I. Kapusta and P. Lichard, Parametrization of thermal photon emission rates from mesonic matter, Phys. Rev. C 45, 3034 (1992). doi: /physrevc [TUR13]: S. Turbide, R. Rapp and C. Gale, Hadronic production of thermal photons, Phys. Rev. C 69, (2004) doi: /physrevc [hep-ph/ ]. [WEIL16]: J.Weil et al., Particle production and equilibrium properties within a new hadron transport approach for heavy-ion collisions, arxiv: [nucl-th]. July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 23

24 Backup slides July 12, 2016 Photon Production in a Hadronic Transport Approach (Niklas Ehlert) 24

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