Osaka University RCNP Toshinao Tsunemi New Results on 　from E787 Osaka University RCNP Toshinao Tsunemi 15 June 2005 KAON 2005

Outline 1) Introduction 2) BNL-E787 detector 3) Kinematic fit 4) Data reduction and background estimation 5) Spectrum Fitting 6) Systematic error 7) Summary 15 June 2005 KAON 2005

DE and IB component IB (Internal Bremsstrahlung) DE (Direct Emission) (about 98%) (about 2%) IB (Internal Bremsstrahlung) DE (Direct Emission) BR(IB)=2.61*10-4 predicted by QED (radiative correction) 15 June 2005 KAON 2005

W definition （K+ rest frame） Opening angle between p+ and photon radiated photon energy p+ energy kaon mass p+ mass p+ momentum 15 June 2005 KAON 2005

W spectra DE 逆はreverce IB 15 June 2005 KAON 2005

History (55 < Tp+ < 90 MeV) Theoretical prediction　O(p6) Theoretical prediction O(p4) theory: Chiral Perturbation Theory 15 June 2005 KAON 2005

The data was taken in the year of 1995. Number of kaons was 2.83×1011 About the published paper from BNL-E787 in the year of 2000. (S.Adler et al. Phys.Rev.Lett. 85,4856(2000)) The data was taken in the year of 1995. Number of kaons was　2.83×1011 The result of DE branching ratio This presentation（data taken in 1998） １）more events than data in 1995 ２）The trigger was modified to accept lower p+ momentum 15 June 2005 KAON 2005

BNL-E787 detector ) 12 cm K+ Kaon stopping Target Main fibers K+ Edge fibers Kaon stopping Target 5 mm square 41３ scintillation fibers ) Energy Range in the Target charged track side view of the cylindrical detector 15 June 2005 KAON 2005

BNL-E787 detector K+ Drift Chamber (UTC) 3 active layers Momentum of charged track side view of the cylindrical detector 15 June 2005 KAON 2005

BNL-E787 detector ) K+ Range Stack 21 layers of plastic scintilators Upper half of the cylindrical detector Range Stack 21 layers of plastic scintilators ) Energy Range Charged track side view of the cylindrical detector 15 June 2005 KAON 2005

BNL-E787 detector ) K+ Barrel photon detector Upper half of the cylindrical detector K+ Barrel photon detector Plastic & lead sandwich detector 4 layers 192 modules ) Energy position photons side view of the cylindrical detector 15 June 2005 KAON 2005

Charged track spectrum 15 June 2005 KAON 2005

trigger for K+→p+p0g Condition for Photon： Three or more clusters Stopped in Layer4-6 ＊ p+ condition in 1995： Stopped in Layer7-10 Number of Kaon 　　　　　 　3.48×1011 （1995　2.83×1011） 15 June 2005 KAON 2005

Kinematic fit (most important cut) 6 constraints Momentum conservation (x, y, z 3 constraints) Energy conservation mass p+ mass p0 13 variables p+ p0 g 1 3 4 p + momentum p + energy Energy of photons Azimuthal angle Dip angle p+ g g g 1 pion and 3 photons 15 June 2005 KAON 2005

How to select two photons from π0 There are three combinations to select two photons from p0 p+ p0 g p+ g g g 3 photons Select the combination with the most c2 probability (Prob) and the second most c2 probability calculated by Kinematic fit. Prob (Kinematic fit) ×matrix element(IB)2　is calculated for the above combinations. The combination with the larger value is assumed to be the correct combination. The percentage of correct combination is estimated by M.C. to be 97.2% and 83.4% for IB and DE, respectively. 15 June 2005 KAON 2005

Chi-square probability accept Chi-square probability 15 June 2005 KAON 2005

The power of kinetic fit photon energy before after MeV MeV M.C. M.C. MeV MeV Resolution 1.5 sqrt(E MeV) から0.50 sqrt(E MeV) about about 15 June 2005 KAON 2005

Resolution improvement on W M.C. M.C. RMS 0.０25 RMS 0.05 15 June 2005 KAON 2005

Bgd rejection due to Kinematic fit before after before after p+p0p0 accept p+p0g m+p0g p+p0g 念のため　for comfirmation π+ momentum Charged track consistency Measured - expected 15 June 2005 KAON 2005

Data reduction table π+ identification in the UTC & RS π+ identification in the Target Reject e+ Photon cluster is 3 Extra photon veto Missing momentum Photon clustering confirm π+ mass Photons are on time Photon is in the fiducial region Confirmation of trigger condition W>0.1 Kinematic fit Combination improve 140 MeV/c < Pπ+ <180 MeV/c 15 June 2005 KAON 2005

Background estimation by BNL-E787 standard method All W W>0.5 15 June 2005 KAON 2005

spectra fitting Number of events after all cut is 20571. 1) W spectra 2) Consistency between real and M.C. in W 3) Consistency in other spectra 4) Fitting result 15 June 2005 KAON 2005

W spectra Real IB(M.C.) DE(M.C.) 15 June 2005 KAON 2005

Consistency between real and UMC M.C. reproduces the real data in the region of W<0.4 where IB is dominant. Real data IB (M.C.) 2 /n.d.f=11.2/14 15 June 2005 KAON 2005

Consistency between Real & UMC Real data IB (M.C.) Real and M.C data is compared In the region of W<0.4 15 June 2005 KAON 2005

Spectrum fitting Real data is fitted by M.C.(IB+DE) *fitted by only IB IB (M.C.) IB+DE (M.C.) observed/IB Real data IB+DE (M.C.) Number of Event 統計エラーをしゃべること。 *fitted by only IB 2 /n.d.f=49.0/7 2 /n.d.f=7.6/6 result The DE ratio to IB is RDE=0.070±0.011 15 June 2005 KAON 2005

Systematic error Total systematic error on RDE +18 % -23 % Added in quadrature 15 June 2005 KAON 2005

Branching ratio of p+p0g preliminary data in 1998 Previously published data from 1995 Combined value (preliminary) 15 June 2005 KAON 2005

Summary 1) BNL-E787 have data taken in 1995 and 1998. 2) Lower p+ momentum region is used in 1998, compared to the 1995 data. preliminary Consistent with theoretical prediction by Chiral Perturbation at O(p4) . 15 June 2005 KAON 2005

backup Back up slides 15 June 2005 KAON 2005

p+p0g spectra ? IB INT DE 1) Reducible O(p4) M: magnetic amplitude ２) VMD O(p6) ３) other O(p6) 15 June 2005 KAON 2005

Trigger acceptance DE component (M.C.) ’98 DE events ’95 DE events arbitrary unit accept 15 June 2005 KAON 2005

W Spectra W W IB DE 15 June 2005 KAON 2005

Kinematic fit (stretch function) Ideally, the distribution must be a normal Gaussian. (i.e the mean and sigma is 0 and 1.) i=1~13 The resolutions are tuned for si to be from a normal Gaussian. The measured value for M.C data is smeared to reproduce real date. ：random numbers to be formed to a normal Gaussian example 15 June 2005 KAON 2005

Stretch functions π+ photon Azimuthal angle Dip angle energy momentum 15 June 2005 KAON 2005

How to calculate branching ratio of p+p0g Number of M.C. DE Events for fitting number of M.C. IB Events for fitting Ratio from fitting IB acceptance calculated by M.C. QED prediction for the IB branching ratio DE acceptance calculated by M.C. 15 June 2005 KAON 2005

Summary 1) BNL-E787 have data taken in 1995 and 1998. 2) Lower p+ momentum region is used in 1998, compared to the 1995 data. This experiment consistent Theory（only reducible term） 15 June 2005 KAON 2005

M　(no dimension)(1/2) G.Ecker, H.Neufeld and A. Pich, Phys.Lett B278,337 (1992) ＊ f is a parameter of CｈPT at O(p2). f=93 MeV 15 June 2005 KAON 2005

M (no dimension)(2/2) 15 June 2005 KAON 2005