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Φ(1020) Photoproduction in Neutral Decay Channel

Φ(1020) Photoproduction in Neutral Decay Channel. Heghine Seraydaryan. June 12, 2009. Outline. Theory Motivation Data and Selection of Events for p  p  K S K L p’ Preliminary Results Summary. . . , . p. p’. Φ(1020) Meson. Theory. Decay channels:

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Φ(1020) Photoproduction in Neutral Decay Channel

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  1. Φ(1020) Photoproduction in Neutral Decay Channel Heghine Seraydaryan June 12, 2009

  2. Outline • Theory • Motivation • Data and Selection of Events for p  p  KSKLp’ • Preliminary Results • Summary

  3.  ,  p p’ Φ(1020) Meson. Theory Decay channels: K+ K- (49.2%) KS KL (34%)  0,+ - 0 (15.3%)   (1.3%) Production mechanisms: Kinematics and observables: Θ - helicity angle Φ - azimuthal angle

  4. MotivationandObservations for the Charged Channel Previous results for  p  pΦ(1020)  p K+ K- : • The peak at about 2 GeV with width 0.2 GeV • Theoretical curves fail to describe the data • Note: • The cross sections were obtained without cut on (1520) Charged Channel Motivation • No photo-production data for Neutral Channel • We can check the cross-section behavior and • slope behavior D.Tedeschi

  5. Events cleaning for  p  Φ(1020) p  KS KL p The particle identification was done by using DC and SC information Three particle events were selected (p, +,-) The invariant mass of (+,-) was taken to be mass of KS Missing mass of ( p->p +-)X was taken to be mass of KL Also cuts on momenta of the particles: P + > 0.1 (GeV/c), P - > 0.1 (GeV/c) Pp > 0.35 (GeV/c)

  6. α=3.4 Gen GSIM RECSIS Generator The generator for  meson was created using several iterations method The generator is based on data. Cross section is generated as: As initial energy distribution the K+K- energy distribution was taken (using Tedeschi results). f(E) and ρ00parameters were varied tomake Monte Carlo fit the data. The same thing was done for t distribution. Gen, GSIM, RECSIS were used several times to obtain generator-data agreement.

  7. E = 1.6 E = 1.65 E = 1.7 E = 1.75 E = 1.8 E = 1.85 E = 1.9 E = 1.95 E = 2.0 E = 2.05 E = 2.1 E = 2.15 E = 2.2 E = 2.25 E = 2.3 E = 2.35 E = 2.4 E = 2.45 E = 2.5 E = 2.55 Acceptance t- tmin Acceptances E = 1.6  1.6 GeV  E  1.65 GeV

  8. Efficiency calculations for - missing - detected - To obtain the efficiency for - ,two reactions were used: (γp->p +) - (γp->p -+ +) - Four momentum slices (0.1-0.15),(0.15-0.2),(0.2-0.3), (> 0.3) 180 θ bins 360 φ bins (1 degree each) p = 0.125 GeV/c p = 0.175 GeV/c p = 0.25 GeV/c To obtain the efficiency for +, were used: (γp->p -) + (γp->p -+ -) + and to obtain the efficiency for p ,were used: (γp-> +-)p (γp-> +-+ -)p p  0.3 GeV/c

  9. Cuts and Corrections We used: Cuts On momenta of the particles: P + > 0.1 (GeV/c), P - > 0.1 (GeV/c) Pp > 0.35 (GeV/c) To select K : |M(KS)-0.49765| < 0.008 (GeV/c2) |M(KL)-0.49765| < 0.015 (GeV/c2) To select  : M(φ) = 1.02 ± 0.02 (GeV/c2) To select background: M(φ) = 1/2*N(1.06 ± 0.02 (GeV/c2) ) • Corrections • Standard g11 momentum corrections • Standard g11 photon energy corrections • Energy loss corrections for +, - and p • Photon timing : 1 photon in 2 ns interval • Acceptance corrections • Efficiency corrections

  10. CLAS PRELIMINARY Preliminary Results A. Thomas et al For the φ cross section in the Neutral decay mode we observe a peak , which is shifted to 1.9 GeV and is slightly smaller, compared to the peak at about 2 GeV in the Charged channel. We also observe some difference for the slope values of the two channels. For the Neutral channel they are much smaller in photon energy region (1.6:2.4) GeV. The Neutral channel cross section is multiplied by branching ratio (1.447)

  11. Preliminary Results : Angular Distribution Function CLAS PRELIMINARY CLAS PRELIMINARY Helicity Frame

  12. Preliminary Results : Angular Distribution Function + C cos CLAS PRELIMINARY CLAS PRELIMINARY Gottfried-Jackson Frame The fit function had to be modified with an addition of a linear term cos, to be able to fit the data correctly.

  13. Preliminary Results : Spin-Density Matrix Elements CLAS PRELIMINARY CLAS PRELIMINARY Helicity Frame GJ Frame

  14. Preliminary Results : Angular Distribution Function CLAS PRELIMINARY GJ Frame

  15. Summary We analyzed φ(1020) production in Neutral decay channel from g11 data. We measured the cross section, the slope and the angular dependences of the cross section. We extracted spin-density matrix elements in GJ and Helicity frames. Conclusions The slope of the φproduction in Neutral channel is much smaller than the Charged channel slope for the photon energy interval (1.6:2.4) GeV. The cross section peak at 2 GeV in Charged decay mode is slightly larger than the one observed in Neutral decay mode. Comparison of the W between the Neutral and Charged channels shows agreement for two energy bins in the Helicity frame. For the Charged Channel data is used T. Mibe’s measurements from Spring-8 . The difference between the two channels must be investigated further.

  16. 1/b*

  17. Efficiency calculations for + missing+ detected + • To obtain the efficiency for + ,two reactions were used: • (γp->p -) + • (γp->p -+ -) + • Four momentum slices • (0.1-0.15),(0.15-0.2),(0.2-0.3), • (>0.3) • 180 θ bins • 360 φ bins(1 degree each) • The ratio of two is the efficiency

  18. Efficiency calculations for protons missing P detected P • To obtain the efficiency for p ,two reactions were used: • (γp-> +-)p • (γp-> +-+ -)p • Four momentum slices • (0.1-0.15),(0.15-0.2),(0.2-0.3), • (>0.3) • 180 θ bins • 360 φ bins(1 degree each) • The ratio of two is the efficiency Large angle efficiency (1) comes from the events with two detected protons (are mostly background)

  19. + Data Corrections with Efficiencies

  20. - Data Corrections with Efficiencies

  21. ProtonData Corrections with Efficiencies

  22. Acceptance Calculation Events •  events were generated in 4 (figure a) • GSIM was used to simulate the detector • RECSIS was used to reconstruct the • events as in the experiment (figure b) • The acceptance was calculated as the • ratio of reconstructed simulated data, • presented on figure b, over the simulated • data, presented on figure a. • It was done for different energy regions • and different t bins. generated events a) Events reconstructed events b) Acceptance c) t - t min

  23. Generator and Data Agreement E = 1.65 E = 1.75 E = 1.85 E = 1.65  1.6 GeV  E  1.7 GeV E = 1.95 E = 2.05 E = 2.15 Data events Generated events E = 2.25 E = 2.35 E = 2.45

  24. Generator and Data Agreement Data events Generated events

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