Hadronic Decay of η and η

Transcription

1 Hadronic Decay of η and η CHANDRA S. NEPALI August 5, 212 Light Meson Decays Workshop August 5, 212, Jefferson Lab Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

2 Contents Introduction 1 Introduction 2 Experiment 3 Dalitz Plots 4 Simulation Acceptance correction Phasespace correction 5 Very Preliminary Results Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

3 Introduction Introduction Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

4 Introduction Introduction Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

5 Introduction Introduction About 2M η and 43K η events on tape. Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

6 Contents Experiment 1 Introduction 2 Experiment 3 Dalitz Plots 4 Simulation Acceptance correction Phasespace correction 5 Very Preliminary Results Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

7 Experiment Experiment Photo-production experiment on a liquid hydrogen target with bremsstrahlung photon beam. E electron 4., 5. GeV Target cell was 4 cm long placed 1 cm upstream of the CLAS center. Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

8 Contents 1 Introduction 2 Experiment 3 Dalitz Plots 4 Simulation Acceptance correction Phasespace correction 5 Very Preliminary Results Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

9 η (547) and η (958) production via following channels are used: γ + P P + η P + π + + π + π (22.7%) γ + P P + η P + π + + π + η (44.5%) Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

10 ) 2 MM(P) (GeV/c ω η ω η MM(Pπ + π ) (GeV/c ) ω π + π π (89.1%) η π + π π (22.7%) η π + π γ (4.6%) ω π + π (1.5%) Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

11 ) 2 MM(P) (GeV/c ω η ω η MM(Pπ + π ) (GeV/c ) ω π + π π (89.1%) η π + π π (22.7%) η π + π γ (4.6%) ω π + π (1.5%) ) 2 MM(P) (GeV/c φ η f 1 (1285) MM(Pπ + π ) (GeV/c ) f 1 ππη (52%) η π + π η (44.5%) φ K S K L (34%) a ωππ (seen) a (145) Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

12 peak =.1361 σ = MM(Pπ + π - ) (GeV/c 2 ) peak =.5491 σ = MM(P) (GeV/c 2 ) Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

13 peak =.1361 σ = MM(Pπ + π - ) (GeV/c 2 ) peak =.5464 σ = MM(Pπ + π - ) (GeV/c 2 ) peak =.5491 σ = MM(P) (GeV/c 2 ) peak =.9581 σ = MM(P) (GeV/c 2 ) Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

14 peak =.1361 σ = MM(Pπ + π - ) (GeV/c 2 ) peak =.5464 σ = MM(Pπ + π - ) (GeV/c 2 ) peak =.5491 σ = MM(P) (GeV/c 2 ) peak =.9581 σ = MM(P) (GeV/c 2 ) About 2M η and 43K η events (after background subtraction) on tape. Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

15 Dalitz Plots Dalitz Plots DALITZ VARIABLES: For η π + π π : x = 3 Q (T π + T π ); y = m π + 2m π m π T π Q 1 (1) where Q = T π + + T π + T π and Ts are the kinetic energies in rest frame of η. Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

16 Dalitz Plots Dalitz Plots DALITZ VARIABLES: For η π + π π : x = 3 Q (T π + T π ); y = m π + 2m π m π T π Q 1 (1) where Q = T π + + T π + T π and Ts are the kinetic energies in rest frame of η. For η π + π η: x = 3 Q (T π + T π ); y = m η + 2m π m π T η Q 1 (2) where Q = T π + + T π + T η and Ts are the kinetic energies in rest frame of η. Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

17 Dalitz Plots η π + π π η π + π η Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

18 Dalitz Plots The decay amplitude expanded around the center of the Dalitz plot is parameterized as M 2 = A(1 + ay + by 2 + cx + dx 2 ) phase space (3) where a, b, c and d are real parameters and A is a normalization factor. Odd term in X are forbidden in charged channel due to charge conjugation and c = for neutral channel due to symmetry of the wave function. Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

19 Dalitz Plots The decay amplitude expanded around the center of the Dalitz plot is parameterized as M 2 = A(1 + ay + by 2 + cx + dx 2 ) phase space (3) where a, b, c and d are real parameters and A is a normalization factor. Odd term in X are forbidden in charged channel due to charge conjugation and c = for neutral channel due to symmetry of the wave function. Second parametrization used is M 2 = A( 1 + αy 2 + cx + dx 2 ) phase space (4) where α is a complex parameter. a = 2Re(α); b = Re 2 (α) + Im 2 (α) (5) Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

20 Contents Simulation 1 Introduction 2 Experiment 3 Dalitz Plots 4 Simulation Acceptance correction Phasespace correction 5 Very Preliminary Results Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

21 Simulation Simulation Acceptance correction Acceptance correction: MC events are generated based on only phasespace and simulated through the CLAS detectors. A(x, y) = N rec(x, y) N gen (x, y) Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

22 Simulation Acceptance correction For η π + π π : generated MC events simulated MC events Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

23 Simulation Acceptance correction For η π + π π : generated MC events simulated MC events Acceptance Acceptance X Y Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

24 For η ηπ + π : Simulation Acceptance correction generated MC events simulated MC events Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

25 For η ηπ + π : Simulation Acceptance correction generated MC events simulated MC events Acceptance Acceptance X Y Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

26 Simulation Acceptance correction Resolution of Dalitz variables X and Y from MC: X, Y = X rec, Y rec X gen, Y gen center = -.31 σ = center =.22 σ = X Y center = -.51 σ = center =.31 σ = X Y Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

27 Simulation Phasespace correction Phasespace correction: The generated MC events is used for phasespace correction. Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

28 Simulation Phasespace correction Phasespace correction: The generated MC events is used for phasespace correction. Exp. data weighted by (production cross section) 1 = Acceptance correction = Divide by phasespace = Results Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

29 Contents Very Preliminary Results 1 Introduction 2 Experiment 3 Dalitz Plots 4 Simulation Acceptance correction Phasespace correction 5 Very Preliminary Results Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

30 Very Preliminary Results Very Preliminary Results General parameterization: M(X, Y) 2 = N(1+aY + by 2 + cx + dx 2 + exy + fy 3 + gx 3 + hx 2 Y + lxy 2 ) From 2D fit: a = ±.39 b =.2395 ±.293 c =.225 ±.316 d =.428 ±.283 Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

31 Very Preliminary Results a = ±.39 b =.2395 ±.293 c =.225 ±.316 d =.428 ±.283 Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

32 Very Preliminary Results Backup slides Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23

33 Very Preliminary Results 35 3 π + π π+ π p (GeV/c) η p (GeV/c) η Chandra S. Nepali (ODU) Hadronic Decay of η and η August 5, / 23