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First data of the L (1405) in the charged ( Sp ) 0 decay channels for p+p reactions

First data of the L (1405) in the charged ( Sp ) 0 decay channels for p+p reactions. Johannes Siebenson Technische Universität München and Excellence Cluster Universe. Outline:. 1. Λ(1405) in the different decay channels. 2. Analysis of the Λ(1405) in the charged channels.

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First data of the L (1405) in the charged ( Sp ) 0 decay channels for p+p reactions

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  1. First data of the L(1405) in the charged (Sp)0 decay channels for p+p reactions Johannes Siebenson Technische Universität München and Excellence Cluster Universe

  2. Outline: 1. Λ(1405) in the different decay channels. 2. Analysis of the Λ(1405) in the charged channels. 3. Analysis of the Σ(1385)+. 4. Summary and Outlook.

  3. Separation of Λ(1405) and S(1385) 33.3% 5.8% 5.8% 33.3% 1.3% 33.3% 87.0% Г≈ 36 Г≈ 50MeV/c2 Г≈ 36 MeV/c2 Page 3 15.3.2010

  4. Different decay channels of the Λ(1405) g + p → L(1405) + K+ : Final states: K+ g S p p Different cross sections: I=0 → L(1405) I=1 Page 4

  5. Interference Effect g + p → L(1405) + K+ →(Sp)0 + K+ : J. C. Nacher et al., Phys. Lett. B455, 55, (1999) K. Moryaet al., arXiv:0911.0925v1 [nucl-ex] 4 Nov 2009 Line shape is different for the different decay channels! Page 5

  6. Analysis of the Λ(1405) Λ(1405) in the charged decay channels: Steps of the Analysis: Page 6

  7. Analysis of the Λ(1405) Λ(1405) in the charged decay channels: Steps of the Analysis: • Identify the four charged particles (p, K+, π+, π- ). Page 6

  8. Analysis of the Λ(1405) Λ(1405) in the charged decay channels: Steps of the Analysis: • Identify the four charged particles (p, K+, π+, π- ). • Cut on the neutron mass and use kinematic refit on the neutron. Page 6

  9. Analysis of the Λ(1405) Λ(1405) in the charged decay channels: Steps of the Analysis: • Identify the four charged particles (p, K+, π+, π- ). • Cut on the neutron mass and use kinematic refit on the neutron. • Cut on the Σ+ or Σ- mass. Page 6

  10. Analysis of the Λ(1405) Λ(1405) in the charged decay channels: Steps of the Analysis: • Identify the four charged particles (p, K+, π+, π- ). • Cut on the neutron mass and use kinematic refit on the neutron. • Cut on the Σ+ or Σ- mass. • Try to understand background and subtract it. Page 6

  11. Particle Identification • Proton, p+, p- are only identified via their energy loss in the MDCs. • Kaons are identified via their energy loss in MDCs and TOF or TOFino. Page 7

  12. Particle Identification • Proton, p+, p- are only identified via their energy loss in the MDCs. • Kaons are identified via their energy loss in MDCs and TOF or TOFino. • And the mass of the kaons is reconstructed. Mass distribution of kaon candidates: • Mass resolution is very poor due to missing start detector. • Extract kaons by cut on the gray shaded mass area. • Misidentification of pions and protons as kaons rather high. counts preliminary Mass [MeV/c2] Page 8

  13. Neutron After mass cut on the K+ (350 MeV/c2 < m K+ < 650 MeV/c2): • Clear neutron peak on top of large background. This is only misidentification of a proton or a pion as a K+. • Cut on the gray shaded area to extract Λ(1405) and apply kinematic refit. counts preliminary MM(p,K+,p+,p-) [MeV/c2] Page 9

  14. First background reduction counts counts preliminary preliminary M(p,p-) [MeV/c2] M(p+,p-) [MeV/c2] These channels are extracted by cutting outside the red shaded area. Page 10

  15. Effect of the kinematic refit The refit reduces the width of the Σ+ and Σ- , and thus the signal to background ratio is increased. Σ+ resonance Σ- resonance counts counts preliminary preliminary MM(p,K+,p-) [MeV/c2] MM(p,K+,p+) [MeV/c2] Page 11

  16. Λ(1405) in Σ+ and Σ- channel Σ+ channel Σ- channel counts counts MM(p,K+) [MeV/c2] MM(p,K+) [MeV/c2] preliminary preliminary A peak near 1405 MeV/c2 is clearly visible, but to extract the pure Λ(1405), the background has to be understood and must be subtracted. Page 12

  17. Understanding the background counts Mass [MeV/c2] preliminary Page 13

  18. Understanding the background counts counts 0.5 1 Mass [MeV/c2] MM(p,K+, p+,p-) [MeV/c2] Describe background with a sideband analysis on the kaon mass distribution: preliminary preliminary Page 13

  19. Understanding the background counts counts 0.5 1 Mass [MeV/c2] MM(p,K+, p+,p-) [MeV/c2] Describe background with a sideband analysis on the kaon mass distribution: counts • Red area includes almost only pions, `misidentified` as kaons. • Blue area includes almost only protons, `misidentified` as kaons preliminary preliminary preliminary Mass2 [MeV/c2]2 Page 13

  20. Understanding the background But momentum distribution of kaon candidates is different for the different mass areas. counts 0.5 1 MM(p,K+,p+,p-) [MeV/c2] counts preliminary preliminary Mass2 [MeV/c2]2 Page 14

  21. Understanding the background But momentum distribution of kaon candidates is different for the different mass areas. counts 0.5 1 1 MM(p,K+,p+,p-) [MeV/c2] counts counts preliminary preliminary preliminary Momentum [MeV/c] Mass2 [MeV/c2]2 Page 14

  22. Understanding the background But momentum distribution of kaon candidates is different for the different mass areas. Imitate the black momentum distribution with the red and the blue distributions: a respects, that the relative contribution of pions and protons is not known. counts preliminary Momentum [MeV/c] Page 14

  23. Understanding the background But momentum distribution of kaon candidates is different for the different mass areas. Imitate the black momentum distribution with the red and the blue distributions: a respects, that the relative contribution of pions and protons is not known. counts counts preliminary preliminary Momentum [MeV/c] Momentum [MeV/c] Page 14

  24. Understanding the background Scale green distribution down to the black one by multiplying with a momentum dependent scale factor: Imitate the black momentum distribution with the red and the blue distributions. a respects, that the relative contribution of pions and protons is not known. counts preliminary Momentum [MeV/c] Page 14

  25. Understanding the background Scale green distribution down to the black one by multiplying with a momentum dependent scale factor: Imitate the black momentum distribution with the red and the blue distributions. a respects, that the relative contribution of pions and protons is not known. counts counts preliminary preliminary Momentum [MeV/c] Momentum [MeV/c] Page 14

  26. Understanding the background • Vary a and scale sideband data with: • a and g(p) for the pions • g(p) for the protons until the missing mass distribution fits best to the left figure. counts 0.5 1 MM(p,K+,p+,p-) [MeV/c2] preliminary Page 15

  27. Understanding the background • Vary a and scale sideband data with: • a and g(p) for the pions • g(p) for the protons until the missing mass distribution fits best to the left figure. • The different contributions of pions and protons are resolved. • Analyze the scaled sideband sample in the same way, described before. counts counts preliminary MM(p,K+,p+,p-) [MeV/c2] Page 15

  28. S+ and S- Understand the different contributions to the signals. Σ+ resonance Σ- resonance counts counts preliminary preliminary MM(p,K+, p+) [MeV/c2] MM(p,K+, p-) [MeV/c2] Page 16

  29. S+ and S- Σ+ resonance Σ- resonance counts counts preliminary preliminary MM(p,K+, p+) [MeV/c2] MM(p,K+, p-) [MeV/c2] Page 16

  30. S+ and S- Σ+ resonance Σ- resonance counts counts preliminary preliminary MM(p,K+, p+) [MeV/c2] MM(p,K+, p-) [MeV/c2] Page 16

  31. S+ and S- Σ+ resonance Σ- resonance counts counts preliminary preliminary MM(p,K+, p+) [MeV/c2] MM(p,K+, p-) [MeV/c2] Page 16

  32. misidentification of p or π+ as K+ S+ and S- Σ+ resonance Σ- resonance counts counts preliminary preliminary MM(p,K+, p+) [MeV/c2] MM(p,K+, p-) [MeV/c2] Page 16

  33. misidentification of p or π+ as K+ S+ and S- Σ+ resonance Σ- resonance counts counts preliminary preliminary MM(p,K+, p+) [MeV/c2] MM(p,K+, p-) [MeV/c2] Page 16

  34. Λ(1405) in Σ+ and Σ- channel Σ+ channel Σ- channel counts counts MM(p,K+) [MeV/c2] MM(p,K+) [MeV/c2] • Besides the fit to the S+ and S- resonances, also the mass range above the vertical dashed line is simultaneously fitted with the different contributions. • The different contributions can be subtracted in order to obtain a pure Λ(1405). For that purpose, further systematic studies of the background have to be carried out. preliminary preliminary Page 17

  35. Analysis of the S(1385)+ S(1385)+ : Steps of the Analysis: • Identify the four charged particles (p, K+, π+, π- ) • Cut on the intermediate L and on the neutron. • Use kinematic refit on the neutron • Reconstruct S(1385)+ via invariant mass of L and p+ and subtract background. Page 18

  36. Analysis of the S(1385)+ S(1385)+ : Steps of the Analysis: • Identify the four charged particles (p, K+, π+, π- ) • Cut on the intermediate L and on the neutron. • Use kinematic refit on the neutron • Reconstruct S(1385)+ via invariant mass of L and p+ and subtract background. Page 18

  37. Analysis of the S(1385)+ S(1385)+ : Steps of the Analysis: • Identify the four charged particles (p, K+, π+, π- ) • Cut on the intermediate L and on the neutron. • Use kinematic refit on the neutron • Reconstruct S(1385)+ via invariant mass of L and p+ and subtract background. Page 18

  38. Analysis of the S(1385)+ S(1385)+ : Steps of the Analysis: • Identify the four charged particles (p, K+, π+, π- ) • Cut on the intermediate L and on the neutron. • Use kinematic refit on the neutron • Reconstruct S(1385)+ via invariant mass of L and p+ and subtract background. Page 18

  39. Intermediate L • Comparison between pure spectrum and spectrum with track quality cuts (distance between primary vertex and L decay vertex etc.). • Cuts reduce background essentially without decreasing the L signal too much. counts MM(p,p-) [MeV/c2] preliminary Cut on gray shaded area to separate the S(1385)+ events. Page 19

  40. Neutron • Clear neutron peak on top of misidentification background. • This background (gray histogram) is again described with the momentum scaled sideband analysis. counts MM(p,K+ ,p- ,p+) [MeV/c2] preliminary Cut between vertical dashed lines further separates the S(1385)+ events. All the events are kinematically refitted. Page 20

  41. misidentification of p or π+ as K+ S(1385)+ Background due to:. and due to: counts M(L,p+) [MeV/c2] preliminary Subtract gray histogram in order to obtain a pure S(1385)+ . Page 21

  42. pure S(1385)+ S(1385)+ is a P13 state, therefore it should be described by a p-wave relativistic Breit –Wigner function: counts M(L,p+) [MeV/c2] preliminary Page 22

  43. Comparison to other spectra S(1385)+ not corrected for efficiency and acceptance. S(1385)+ of HADES (with a total yield of ≈ 1500 entries) fits quite well into other spectra, which were used to determine the nominal quantities of this resonance. counts M(L,p+) [MeV/c2] preliminary PDG Entries - M. Baubillier et al., Z. Phy. C23 213 (1984) - S.R. Borenstein et al., Phys. Rev. D 9 3006 (1974) Page 23

  44. Summary Reconstruction of the Λ(1405) in the charged decay channel was shown. • The kinematic refit is essential for an optimized background suppression. • New sideband analysis can describe the misidentification quite well. • The total background below the Λ(1405) understood and could be subtracted. Reconstruction of the S(1385)+ supplies a total yield of about 1500 entries. • The resonance can be described by a p- wave relativistic Breit-Wigner unction. • The results are in very good agreement with other experiments. Page 24

  45. Outlook – Forward Wall FW Taking also into account the FW- data will increase our statistics essentially: Page 25 15.3.2010

  46. HADES Collaboration G. Agakishiev8, C. Agodi1, A. Balanda3,e, G. Bellia1,a, D. Belver15, A. Belyaev6, A. Blanco2, M. Böhmer11, J. L. Boyard13, P. Braun-Munzinger4, P. Cabanelas15, E. Castro15, S. Chernenko6, T. Christ11, M. Destefanis8, J. Díaz16, F. Dohrmann5, A. Dybczak3, T. Eberl11, E. Epple11, L. Fabbietti11, O. Fateev6, P. Finocchiaro1, P. Fonte2,b, J. Friese11, I. Fröhlich7, T. Galatyuk4, J. A. Garzón15, R. Gernhäuser11, C. Gilardi8, M. Golubeva10, D. González-Díaz4, E. Grosse5,c, F. Guber10, M. Heilmann7, T. Hennino13, R. Holzmann4, A. Ierusalimov6, I. Iori9,d, A. Ivashkin10, M. Jurkovic11, B. Kämpfer5, K. Kanaki5, T. Karavicheva10, D. Kirschner8, I. Koenig4, W. Koenig4, B. W. Kolb4, R. Kotte5, A. Kozuch3,e, F. Krizek14, R. Krücken11, W. Kühn8, A. Kugler14, A. Kurepin10, J. Lamas-Valverde15, S. Lang4, J. S. Lange8,K. Lapidus10, L. Lopes2, M. Lorenz4, L. Maier11, A. Mangiarotti2, J. Marín15, J. Markert7, V. Metag8, B. Michalska3, D. Mishra8, E. Morinière13, J. Mousa12, C. Müntz7, L. Naumann5, R. Novotny8, J. Otwinowski3, Y. C. Pachmayer7, M. Palka4, Y. Parpottas12, V. Pechenov8, O. Pechenova8, T. Pérez Cavalcanti8, J. Pietraszko4, W. Przygoda3,e, B. Ramstein13, A. Reshetin10, M. Roy-Stephan13, A. Rustamov4, A. Sadovsky10, B. Sailer11, P. Salabura3, A. Schmah4, J. Siebenson11, R. Simon4, S. Spataro8, B. Spruck8, H. Ströbele7, J. Stroth7,4, C. Sturm7, M. Sudol4, A. Tarantola7, K. Teilab7, P. Tlusty14, M. Traxler4, R. Trebacz3, H. Tsertos12, I. Veretenkin10, V. Wagner14, H. Wen8, M. Wisniowski3, T. Wojcik3, J. Wüstenfeld5, S. Yurevich4, Y. Zanevsky6, P. Zumbruch4 Page 16 15.3.2010

  47. Thank you for your attention!

  48. Λ(1405) in Σ+ and Σ- channel To separate the Λ(1405) into the two different decay channels, the following method is used: • Two more kinematic refits are applied: • one with the constraint on the neutron and the Σ+ B) one with the constraint on the neutron and the Σ- • If the missing mass of proton, K+ and π- (MM(p, K+,π-)) lies in the appropriate mass region around the Σ+and the quality for the refit A) is higher than for the refit B), the event is identified as a Σ+-event. And the appropriate condition for the Σ--case.

  49. Λ(1405) in simulations Σ+ channel Σ- channel counts counts MM(p,K+) [MeV/c2] MM(p,K+) [MeV/c2] Black distribution very similar to the experimental spectra.

  50. Λ(1405) in simulations Σ+ channel Σ- channel counts counts MM(p,K+) [MeV/c2] MM(p,K+) [MeV/c2]

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