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Introduction Fritiof String interactions ANGANTYR Leif Lnnblad Department of Astronomy and Theoretical Physics Lund University Lund 2019-02-25 Angantyr 1 Leif Lnnblad Lund University Introduction Fritiof String interactions a

  1. Introduction Fritiof String interactionsˇ ANGANTYR Leif Lönnblad Department of Astronomy and Theoretical Physics Lund University Lund 2019-02-25 Angantyr 1 Leif Lönnblad Lund University

  2. Introduction Fritiof String interactionsˇ a nga nt i r A N G A N T Y R Leif Lönnblad Department of Astronomy and Theoretical Physics Lund University Lund 2019-02-25 Angantyr 1 Leif Lönnblad Lund University

  3. Introduction Fritiof String interactionsˇ What if . . . ◮ . . . there is no QGP? ◮ . . . it’s just a bunch of overlayed NN events? ◮ . . . we can just use P YTHIA 8? ◮ . . . we can build up collective effect from the bottom up? Angantyr 2 Leif Lönnblad Lund University

  4. Introduction Fritiof String interactionsˇ What if . . . ◮ . . . there is no QGP? ◮ . . . it’s just a bunch of overlayed NN events? ◮ . . . we can just use P YTHIA 8? ◮ . . . we can build up collective effect from the bottom up? Angantyr 2 Leif Lönnblad Lund University

  5. Introduction Fritiof String interactionsˇ What if . . . ◮ . . . there is no QGP? ◮ . . . it’s just a bunch of overlayed NN events? ◮ . . . we can just use P YTHIA 8? ◮ . . . we can build up collective effect from the bottom up? Angantyr 2 Leif Lönnblad Lund University

  6. Introduction Fritiof String interactionsˇ What if . . . ◮ . . . there is no QGP? ◮ . . . it’s just a bunch of overlayed NN events? ◮ . . . we can just use P YTHIA 8? ◮ . . . we can build up collective effect from the bottom up? Angantyr 2 Leif Lönnblad Lund University

  7. Introduction Fritiof String interactionsˇ Outline ◮ Fritiof ◮ String interactions ◮ Multiple interactions in p A & AA ◮ New Glauber models ◮ Angantyr vs. LHC ◮ Summary Angantyr 3 Leif Lönnblad Lund University

  8. Introduction Fritiof String interactionsˇ The Wounded Nucleon model and Fritiof A simple model by Białas and Czy˙ z, implemented in Fritiof Each wounded nucleon contributes with hadrons according to a function F ( η ) . Fitted to data, and approximately looks like dN / d η ✻ ✲ η dN d η = F ( η ) (single wounded nucleon) [Nucl.Phys.B111(1976)461, J.Phys.G35(2008)044053, Nucl.Phys.B281(1987)289.] Angantyr 4 Leif Lönnblad Lund University

  9. Introduction Fritiof String interactionsˇ The Wounded Nucleon model and Fritiof A simple model by Białas and Czy˙ z, implemented in Fritiof Each wounded nucleon contributes with hadrons according to a function F ( η ) . Fitted to data, and approximately looks like dN / d η ✻ ✲ η dN d η = F ( η ) + F ( − η ) ( pp ) [Nucl.Phys.B111(1976)461, J.Phys.G35(2008)044053, Nucl.Phys.B281(1987)289.] Angantyr 4 Leif Lönnblad Lund University

  10. Introduction Fritiof String interactionsˇ The Wounded Nucleon model and Fritiof A simple model by Białas and Czy˙ z, implemented in Fritiof Each wounded nucleon contributes with hadrons according to a function F ( η ) . Fitted to data, and approximately looks like dN / d η ✻ ✲ η dN d η = w t F ( η ) + F ( − η ) ( p A ) [Nucl.Phys.B111(1976)461, J.Phys.G35(2008)044053, Nucl.Phys.B281(1987)289.] Angantyr 4 Leif Lönnblad Lund University

  11. Introduction Fritiof String interactionsˇ The Wounded Nucleon model and Fritiof A simple model by Białas and Czy˙ z, implemented in Fritiof Each wounded nucleon contributes with hadrons according to a function F ( η ) . Fitted to data, and approximately looks like dN / d η ✻ ✲ η dN d η = w t F ( η ) + w p F ( − η ) ( AA ) [Nucl.Phys.B111(1976)461, J.Phys.G35(2008)044053, Nucl.Phys.B281(1987)289.] Angantyr 4 Leif Lönnblad Lund University

  12. Introduction Fritiof String interactionsˇ In Fritiof this was modelled by stretching out a string from each wounded nucleon with an invariant mass distributed as dm X / m X . Each string gives a flat rapidity distribution, so This gives F ( η ) ∼ η − η 0 . Note that there are no collective effects here. But nevertheless Fritiof reproduced most data: No conclusive evidence for QGP until the late nineties. Angantyr 5 Leif Lönnblad Lund University

  13. Introduction Fritiof String interactionsˇ What’s missing in Fritiof? ◮ QGP? ◮ Jets ◮ Multiple interactions ◮ Initial state fluctuations ◮ Interactions between strings Angantyr 6 Leif Lönnblad Lund University

  14. Introduction Fritiof String interactionsˇ What’s missing in Fritiof? ◮ QGP? ◮ Jets ◮ Multiple interactions ◮ Initial state fluctuations ◮ Interactions between strings Angantyr 6 Leif Lönnblad Lund University

  15. Fritiofˆ String interactions Multiple interactions in p A & AA ˇ Interacting Strings The Lund Model π m 2 π m 2 π p 2 q ⊥ q ⊥ ◮ The tunnelling mechanism: P ∝ e − ≡ e − κ e − κ κ ◮ The fragmentation function: p ( z ) = N ( 1 − z ) a e − bm 2 ⊥ / z z ◮ Many parameters depends (implicitly) on κ . Angantyr 7 Leif Lönnblad Lund University

  16. Fritiofˆ String interactions Multiple interactions in p A & AA ˇ Interacting Strings The Lund Model π m 2 π m 2 π p 2 q ⊥ q ⊥ ◮ The tunnelling mechanism: P ∝ e − ≡ e − κ e − κ κ ◮ The fragmentation function: p ( z ) = N ( 1 − z ) a e − bm 2 ⊥ / z z ◮ Many parameters depends (implicitly) on κ . Angantyr 7 Leif Lönnblad Lund University

  17. Fritiofˆ String interactions Multiple interactions in p A & AA ˇ Interacting Strings The Lund Model π m 2 π m 2 π p 2 q ⊥ q ⊥ ◮ The tunnelling mechanism: P ∝ e − ≡ e − κ e − κ κ ◮ The fragmentation function: p ( z ) = N ( 1 − z ) a e − bm 2 ⊥ / z z ◮ Many parameters depends (implicitly) on κ . Angantyr 7 Leif Lönnblad Lund University

  18. Fritiofˆ String interactions Multiple interactions in p A & AA ˇ Interacting Strings The Lund Model π m 2 π m 2 π p 2 q ⊥ q ⊥ ◮ The tunnelling mechanism: P ∝ e − ≡ e − κ e − κ κ ◮ The fragmentation function: p ( z ) = N ( 1 − z ) a e − bm 2 ⊥ / z z ◮ Many parameters depends (implicitly) on κ . Angantyr 7 Leif Lönnblad Lund University

  19. Fritiofˆ String interactions Multiple interactions in p A & AA ˇ Overlapping strings ◮ How do we treat strings that overlap in space–time? Angantyr 8 Leif Lönnblad Lund University

  20. Fritiofˆ String interactions Multiple interactions in p A & AA ˇ Take the simplest case of two simple, un-correlated, completely overlapping strings, with opposite colour flow. q 1 ¯ q 3 ✛ ✲ • ✛ • ✛ ✲ • ✲ • q 4 ¯ q 2 ◮ 1/9: A colour-singlet (no string) ◮ 8/9: A colour-octet The string tension affects all details in the Lund string fragmentation. It is proportional to the Casimir operator C ( 8 ) 4 C ( 3 ) = 9 2 . 2 Angantyr 9 Leif Lönnblad Lund University

  21. Fritiofˆ String interactions Multiple interactions in p A & AA ˇ Take the simplest case of two simple, un-correlated, completely overlapping strings, with opposite colour flow. q 1 ¯ q 3 ✛ ✲ • ✛ • ✛ ✲ • ✲ • q 4 ¯ q 2 ◮ 1/9: A colour-singlet (no string) ◮ 8/9: A colour-octet The string tension affects all details in the Lund string fragmentation. It is proportional to the Casimir operator C ( 8 ) 4 C ( 3 ) = 9 2 . 2 Angantyr 9 Leif Lönnblad Lund University

  22. Fritiofˆ String interactions Multiple interactions in p A & AA ˇ Take the simplest case of two simple, un-correlated, completely overlapping strings, with opposite colour flow. q 1 ¯ q 3 ✛ ✲ • ✛ • ✛ ✲ • ✲ • q 4 ¯ q 2 ◮ 1/9: A colour-singlet (no string) ◮ 8/9: A colour-octet The string tension affects all details in the Lund string fragmentation. It is proportional to the Casimir operator C ( 8 ) 4 C ( 3 ) = 9 2 . 2 Angantyr 9 Leif Lönnblad Lund University

  23. Fritiofˆ String interactions Multiple interactions in p A & AA ˇ And for parallel colour flows:. ¯ q 1 q 3 ✛ ✲ • • ✲ ✛ ✲ • • ✲ q 4 ¯ q 2 ◮ 1/3: An anti-triplet ◮ 2/3: A sextet C ( 6 ) 2 C ( 3 ) = 5 2 2 The anti-triplet case is related to string junctions and baryon production (popcorn mechanism). Angantyr 10 Leif Lönnblad Lund University

  24. Fritiofˆ String interactions Multiple interactions in p A & AA ˇ And for parallel colour flows:. ¯ q 1 q 3 ✛ ✲ • • ✲ ✛ ✲ • • ✲ q 4 ¯ q 2 ◮ 1/3: An anti-triplet ◮ 2/3: A sextet C ( 6 ) 2 C ( 3 ) = 5 2 2 The anti-triplet case is related to string junctions and baryon production (popcorn mechanism). Angantyr 10 Leif Lönnblad Lund University

  25. Fritiofˆ String interactions Multiple interactions in p A & AA ˇ A random walk in colour-space 10 6 8 3 8 ¯ 3 1 [Nucl.Phys.B254(1984)449] Angantyr 11 Leif Lönnblad Lund University

  26. Fritiofˆ String interactions Multiple interactions in p A & AA ˇ The Rope Model ◮ Partially overlapping string pieces in impact parameter and rapidity. ◮ Reconnect to get colour singlets. ◮ Random walk for the rest to get higher colour multiplets (ropes). ◮ The rope will break one string at the time. ◮ Calculate an effective string tension of a break-up, e.g. ◮ the first string to break in a sextet has an effective κ eff ∝ C 6 2 − C 3 2 = 3 2 C 3 2 ◮ The second breakup has standard κ ∝ C 3 2 ◮ Rescale the P YTHIA 8 parameters accordingly. Angantyr 12 Leif Lönnblad Lund University

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