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Cumulative proton production in nuclei-nuclei collisions

Cumulative proton production in nuclei-nuclei collisions. Elena Litvinenko Anatoly Litvinenko. VBLHEP, JINR, DUBNA. litvin@moonhe.jinr.ru. Outline. Introduction Cumulative particles: a few word about Why they can be interesting for nuclei-nuclei collisions? A few estimations

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Cumulative proton production in nuclei-nuclei collisions

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  1. Cumulative proton production in nuclei-nuclei collisions Elena Litvinenko Anatoly Litvinenko VBLHEP, JINR, DUBNA litvin@moonhe.jinr.ru

  2. Outline. • Introduction • Cumulative particles: a few word about • Why they can be interesting for nuclei-nuclei collisions? • A few estimations • Conclusions

  3. Cumulative particles - definition 1. Subthreshold 2a. Target fragmentation region 2b. Beam fragmentation region

  4. Independence spectra shape from initial energy L.S.Schreder et al.,. Phys.Rev.Lett., 43(24), 1787, (1979). A.M.Baldin, Yad. Fiz.(Rus) ,v 20, 1201, (1979).

  5. Protons. Cumulative and evaporated evaporated cumulative R.Ammar et al, Pisma v JETF (Rus), V.49(4),189, 1989 R.Ammar et al, Preprint FIAN (Rus), 48(4),1989

  6. Independence spectra shape from atomic mass number O.P.Gavrishchuk et al., Nuclear Physics , A(523), 589, (1991).

  7. Some specifics of cumulative particle production Independence spectra from initial energy Clear separation between evaporated and cumulatve nucleons Spectra shape independence from atomic mass number Spectra shape independence from beam particle (hadrons, leptons, light nuclei) Deuteron fragmetation into cumulatve particle

  8. Models of cumulative particle production Hot FLUCTON Cold FLUCTON NO YES C C A.V.Efremov, PEPAN. V13(3), 613, 1982 D.I.Blokhintsev, JETF (Rus.) V.33,1295, (1957)

  9. Models with Cold FLUCTON : High momentum component in target nucleus (different nature for different models) Cumulative proton

  10. Models with Cold FLUCTON Flucton(s) is in the initial state of the colliding nuclei Cumulative particles are produced at the initial stage of collision Can we use cumulative particles to obtain information about the initial stage of the collision? Can they be used as the probe for the density of the exited hadronic matter?

  11. In heavy ion collisions more exited (hot and dense) hadronic matter should appear at the initial stage of collision . The probes, which give information about the property this hadronic matter, have to be connected with this stage . • But at low energy (say ) such probes • are difficult (or impossible) for the use. For example: • the cross section for the jet production is extremely small for low energy • the spectra of direct photon production have big admixture from the resonances decay at low photon momentum and small value of cross section for high momentum. . It means, that it is especially important to find the probes which are connected to the initial state of collision at the small initial energies.

  12. Why it can be interesting in nuclei-nuclei collisions? The possible mark for the initial state of the target nucleus Cumulative protons spectra can not be explained as thermal spectra of the protons emitted from the fireball with the reasonable temperature. So, if you detect the proton with the momentum 0.3 GeV/c or more in the backward semi sphere, you can conclude that you have collision with the flucton in the initial state of target nucleus.

  13. Thermal and cumulative spectra RHIC condition for fireball Blue line – cumulative protons Red line – protons from fireball

  14. Why it can be interesting in nuclei-nuclei collisions? Analogy with high PT hadrons production at RHIC. Jet Quenching. 1.Backward protons are produced during the first stage of collision 2. Spectrum have to be sensitive to the density of the compressed fireball.

  15. The model for spectra shape modification (two stage) 1. Fireball formation 2. Passing cumulative particle through fireball • 1. Fireball formation • Nuclei without diffuse layer • Target nucleon is frozen during collision • No formation length • The cross section approximation is taken from: • V.S.Barashenkov and N.V.Slavin, PEPAN, V.15(5),p.997,(1984) • 2. Passing cumulative particle through fireball • Uniform distribution of fluctons over target volume • Particle in fireball (i.e. particle with momentum less than 0.5 GeV/c) is frozen • Cross section is taken the same as for fireball formation

  16. Spectra shape modification (angular dependence) pA(blue)AuAu(red) b = 0 fm b = 7 fm

  17. Spectra shape modification (angular dependence) pA(blue)AuAu(red) b = 0 fm b = 7 fm

  18. Spectra shape modification (momentum dependence) pA(blue)AuAu(red) b = 0 fm b = 7 fm

  19. Spectra shape modification (momentum dependence) pA(blue)AuAu(red) b = 7 fm b = 0 fm

  20. The possible set upfor fix. targ. Scintillation counters 0.5 cm 1 m (ToF) 20 cm 0.5 cm 0.5 cm Hadron spectrometer without a magnet

  21. Wall of hadron spectrometers without a magnet beam target

  22. Conclusion. • It seems that cumulative particle can give interesting • information about space-time structure of nuclear- collision. • The numbers of detected deuterons are expected • to be three times smaller that numbers of protons.

  23. Backup slides

  24. Have we observables for estimation hadronic matters properties at the first stage for not so big initial energy? High Energy - Bjorken equation But it have to be Under suggestion if

  25. Energy density and Bjorken equation Historically energy density was estimated using final for

  26. Some experimental features of backward proton production in nucleon-nuclei collisions : 1.The spectra show a weak beam energy dependence starting from momentum 4 CeV/c. 2.The spectrum shape is independent from target mass number 3.There is also a weak spectrum shape dependence from the type of beam particle (for the lepton, proton and lights nuclei (A < 12)). 4.The cross section has a strong atomic mass dependence ~ An , n>1. - A.Baldin, Part. And Nucl., V.8(3), p.429 (1977) - V.Lukyanov, A.Titov, Part. And Nucl., V.10(4), p.815 (1979) - V.Stavinsky, Part. And Nucl., V.10(5), p.979 (1979) - L.Frankfurt and M.Strikman, Phys.Rep.,V.76,p.215,(1981) - A.Efremov, Part. And Nucl., V.13(5), p.613 (1982)

  27. The possible set up . Scintillation counters 1 m (ToF) E Hadron spectrometer without a magnet Hadron spectrometer without a magnet

  28. First data from the first RHIC RUN Jet Quenching

  29. STAR Preliminry 20-60% 20-60% Jet tomography Out-plane Back-to-back suppression depends on the reaction plane orientation In-plane energy loss dependence on the path length!

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