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Kinematics of p + n  w p p 0 g p reaction

Kinematics of p + n  w p p 0 g p reaction. Susumu Oda 2007/04/10-19. Motivation. TAPS, PRL 94, 192303 (2005) g A  w X p 0 g X. Condition of kinematics in vacuum. p + beam is assumed. Neutron is target. Beam momentum range is 1087(threshold) – 1800(?) MeV/c. J-PARC K1.8 beam line.

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Kinematics of p + n  w p p 0 g p reaction

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  1. Kinematics of p+nwpp0gp reaction Susumu Oda 2007/04/10-19

  2. Motivation • TAPS, PRL 94, 192303 (2005) • gAwXp0gX

  3. Condition of kinematics in vacuum • p+ beam is assumed. • Neutron is target. • Beam momentum range is 1087(threshold) – 1800(?) MeV/c. • J-PARC K1.8 beam line. • Isotropic production (p+nwp) and decays (wp0g, p02g) are assumed. g p0 g backward forward p More omega mesons might be produced at forward direction (high momentum in lab. frame). g w p+ n

  4. Plabp+=1100MeV/c Polar angle (rad) red: proton green: omega blue: pizero Momentum of omega (MeV/c) Gamma energy (MeV) black: from omega blue and red: from pizero green: lowest energy gamma Polar angle (rad) black: from omega blue and red: from pizero purple: most backward gamma Forward Backward X: Momentum of omega (MeV/c) Y: Energy of lowest energy gamma (MeV) X: Momentum of omega (MeV/c) Y: Polar angle of proton (rad) X: Momentum of omega (MeV/c) Y: Polar angle of most backward gamma (rad)

  5. Most interested region Plabp+=1200MeV/c

  6. Most interested region Plabp+=1400MeV/c

  7. Most interested region Plabp+=1600MeV/c

  8. Most interested region Plabp+=1800MeV/c

  9. Most interested region Plabp+=2000MeV/c

  10. Summary • To detect all three photons from omega, calorimeter with large solid angle (0<q<~120deg) is necessary. • FOREST?? • http://www.lns.tohoku.ac.jp/~hadron/ • To detect recoil protons for background rejection, magnetic spectrometer with large solid angle and good momentum resolution is necessary. • SKS? (aperture?) • 2D position detector is a substitute. • 2MeV/c 1 mrad  300 mm/30cm • GEM? • Final state interaction of proton in nucleus. • Fermi motion of neutron target (LD2, Nb, etc.). • Vertex determination. • Mass resolution? • Production cross section vs beam momentum? • Final state interaction? • s2p04g measurement at the same time??

  11. Background and trigger • There is huge p+np0p background. • 3 gamma coincidence is necessary. • >=3 gamma background. • 2p04g(D+p0p2p0, s2p0, no g partner for p0 mass in the acceptance?) • h3p06g(low mass in offline analysis, many hits online rejection?). • etc. • 1 charged track online (offline?) coincidence (+vertex extrapolation from XY-XY measurement?) • Multi charged track veto? • Interaction rate? • Accidental coincidence rate? • With large acceptance for final state interaction

  12. Reference • Eur. Phys. J. A 11, 95-103 (2001) • Studying the omega mass in-medium in gamma+Api0gamma+X reactions • PRL 94, 192303 (2005) • Observation of In-Medium Modifications of the omega Meson

  13. JAM simulation • http://quark.phy.bnl.gov/~ynara/jam/ • Projectile : pi+ • Target : neutron • Impact parameter : b=0-1.5fm, b2 type • Number of events : 1 million • Other parameters • mstc(8)=0 • mstc(156)=1 • Events which have particles from omega mesons are recorded. • omegapi0gamma decay mode was very tiny fraction. (bug??)

  14. Plabp+=1.8GeV/c omega momentum in lab frame (GeV) omega mass (GeV) p0+p+p- cutoff ?  Red region is p+nwp reaction X: omega momentum in lab frame (GeV) Y: omega polar angle in lab frame (rad) omega polar angle in lab frame (rad)

  15. Plabp+=1.1GeV/c Reaction in this region is possible with the beam energy. Bug??

  16. Plabp+=1.2GeV/c Reaction in this region is possible with the beam energy. Bug??

  17. Plabp+=1.3GeV/c Reaction in this region is possible with the beam energy. Bug??

  18. Plabp+=1.4GeV/c Reaction in this region is possible with the beam energy. Bug??

  19. Plabp+=1.45GeV/c Reaction in this region is possible with the beam energy. Bug??

  20. Plabp+=1.5GeV/c Reaction in this region is possible with the beam energy. Bug??

  21. Plabp+=1.55GeV/c Reaction in this region is possible with the beam energy. Bug??

  22. Plabp+=1.6GeV/c Reaction in this region is possible with the beam energy. Bug??

  23. Plabp+=1.65GeV/c

  24. Plabp+=1.7GeV/c

  25. Plabp+=1.75GeV/c

  26. Plabp+=1.8GeV/c p+nwp+n channel is opened.

  27. Plabp+=1.85GeV/c

  28. Plabp+=1.9GeV/c

  29. Plabp+=2GeV/c

  30. Plabp+=2.5GeV/c

  31. Plabp+=3GeV/c

  32. Plabp+=5GeV/c

  33. Problem of angular distribution from JAM • The behavior of the following resonance around plab=1.4-1.7GeV/c is strange. • KF=32124 N(1720)+ • KF=12128 N(1990)+ • Plab=1.5GeV/c is sqrt(s)=1.932GeV • Plab=1.55GeV/c is sqrt(s)=1.956GeV • Plab=1.642GeV/c is sqrt(s)=2.0GeV • parc(51) : (D=2.0GeV/c2) minimum mass of string for non-strange baryons. • parc(65) : (D=0.7GeV/c2) minimum value for the invariant mass of the excited meson-like string system in a hadron-hadron interaction.

  34. Neutron targetProton momentum (GeV/c) Black: all Red: 92, string Green: 2214, Delta+ 3/2+ Blue: 12128, N(1990)+ 7/2+ Yellow: 12212, N(1440)+ 1/2+ Magenta: 32124, N(1720) 3/2+ Plabp+=1.4GeV/c Plabp+=1.7GeV/c Plabp+=1.6GeV/c

  35. Proton 2D plots

  36. n target Plabp+=1.7GeV/c Proton momentum (GeV/c) Proton polar angle (rad)

  37. 2H target Plabp+=1.7GeV/c Proton momentum (GeV/c) Proton polar angle (rad)

  38. 2H target Plabp+=1.7GeV/cK4(i).EQ.0 (original proton) rejection Proton momentum (GeV/c) Proton polar angle (rad)

  39. 12C target Plabp+=1.7GeV/c Proton momentum (GeV/c) Proton polar angle (rad)

  40. 12C target Plabp+=1.7GeV/cK4(i).EQ.0 (original proton) rejection Proton momentum (GeV/c) Proton polar angle (rad)

  41. High pT proton tag • Plabp+=1.7GeV/c • omega event • pT>1.5GeV/c && theta<0.1rad is used. • pT>1.3GeV/c && theta<0.5rad is better?? • Done by SKS??

  42. n 12C Red : high pT proton tagged event pT>1.5GeV/c && theta<0.1rad 92Nb 2H

  43. n 12C Red : high pT proton tagged event pT>1.3GeV/c && theta<0.5rad 92Nb 2H

  44. Issue • How to separate beam pions and recoil protons? • 2pizero event rate?? • Cross section by other simulation codes. • Mass resolution of calorimeter??

  45. RQMD • http://tonic.physics.sunysb.edu/program/rqmd.html • Target and projectile must be nuclei. • For the UrQMD, target and projectile must also be nuclei.

  46. Isospin symmetry • Since isospins of p+nwp reaction and p-pwn reaction are symmetric, the cross sections should be almost the same. • A reference of p-pwn reaction is PRD14, 28 (1975). • The angular distribution was isotropic in CM.

  47. Calorimeter?? • TAPS/CB ELSA? • Tohoku-LNS FOREST? • KEK E246, 768CsI, 75% of 4pi • Nucl.Instrum.Meth. A494 (2002) 318-325

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