Generators for e + e   wp 0  p 0 p 0 g Study of the f  hg  p 0 p 0 p 0 g background

1. Status Report on f  p0p0g analysis S. Giovannella, S.Miscetti • Generators for e+e wp0 p0p0g • Study of the f  hg  p0p0p0g background • Standard analysis vs s • Dalitz plot

2. Comparison of e+e wp0 p0p0ggenerators BLUE (GEN1) = 2000 MC production weighted according to PRD 63 (2001) RED (GEN2) = Eg spectrum from PRD 63 (2001) + corrected angular distr. BLACK (GEN3)= 3 body phase space from NPB 569 (2000), 158 + GEN2 angular distributions

3. Comparison of e+e wp0 p0p0ggenerators GEN2 GEN3 GEN1 30k events of GEN2 and GEN3 compared with data for s = 1019.6 MeV

4. Comparison of newgenerators with data: GEN2 vs GEN3 • s(e+e wp0 p0p0g) stable using both generators • Background dominated by f0 (green): few % total in 3sM window • BR(f  p0p0g) varies of 1.6% + some differences on Mpp shape for Mpp < 650 MeV

5. Comparison of newgenerators with data: GEN2 vs GEN3

6. Comparison of newgenerators with data: GEN2 vs GEN3

7. Check of f  hg  p0p0p0g background The discrepancy on the evaluation of this background between the old and new MC has been investigated. We have checked the efficiency as a function of different analysis cuts and different cluster efficiency evaluation Old MC – No ECL NevOld = 285,000 Old MC – New ECL Old cluster efficiency NevNew = 1,055,000 Old MC – New ECL New cluster efficiency NevNew = 1,055,000

8. Check of f  hg  p0p0p0g background The suspect to have used a wrong normalization came up in our minds! We start looking at the log files and found that in the last round of our MC reconstruction we lost 1 out of 3 files of this sample Old MC – No ECL NevOld = 285,000 190,000 Old MC – New ECL Old cluster efficiency NevNew = 1,055,000 Old MC – New ECL New cluster efficiency NevNew = 1,055,000

9. 1017.0 MeV 1019.3 MeV 1019.4 MeV 1019.6 MeV 1019.9 MeV 1022.1 MeV f  p0p0ganalysis vs  s • 2001+2002 data divided in 100 keV • bin of  s • Only bins with Lint > 1 pb–1 analyzed • Whole all_phys MC production used in • each  s bin + GEN3 (no machine bckg.) • f  hg, f a0g background • subtracted using f line shape •  p0p0g and e+e wp0 p0p0g events obtained with the usual iterative procedure for each  s • Since the MC Mpp spectrum does not • follow completely the data, it has been • re-shaped using data @ 1019.6 MeV • and then used for all  s bins. • All others p0p0g kinematical variables • shaped with the same weights • Data – MC

10. 1017.0 MeV 1017.0 MeV 1019.3 MeV 1019.6 MeV 1019.4 MeV 1019.6 MeV 1022.1 MeV 1019.9 MeV 1022.1 MeV e+e wp0 p0p0ganalysis vs  s

11. Visible x-sec vs  s •  p0p0g : line shape from fhg overimposed e+e wp0 p0p0g : behaviour vs  s is [JETP 90 (2000), 1067] svis = s0(s) (1+d) |1–ZMfGf / Df|2 s0(s) = BRwpg ( s0 + A ( s–Mf) ) KLOE data fitted by fixing s0 and A to the value obtained from SND using p+pp0p0 final state, d not applied c2/ndf = 1.24 • BR(w  p0g) = 0.076 ± 0.002 • Re(Z) = 0.04 ± 0.01 • Im(Z) = – 0.117 ± 0.01 • To be compared with SND [hep-ex/9907026] • BR(w  p0g) = 0.078 ± 0.010 • Re(Z) = 0.036 ± 0.052 • Im(Z) = – 0.186 ± 0.063 f  p0p0g e+e wp0 p0p0g Stat. + bckg. errors only! • s0 = 8.2 ± 0.2 ± 0.9 nb A = 0.088 ± 0.009 ± 0.011 nb/MeV

12. Dalitz plot analysis: kinematic fit results • Same sample selection of previous analysis • (5 prompt neutral clusters with cos q > 23°) • First kinematic fit with ToF + 4-momentum • Process independent pairing procedure, • which parametrizes p0 mass resolution as a • function of the g’s energy resolution after • kinematic fit • Second kinematic fit with Mp constraint added • Analysis cuts: • 1. c2/ndf < 3 • 2. |DMp| < 5 s • 3. Dc2sel > 1 (?) • Analysis performed @ 1019.6 MeV • Visible x-sec for e+e wp0 p0p0g and •  p0p0g fixed to value obtained with previous analisys. f rp0 p0p0g neglected • Background considered: f  hg  3g/7g, • f  hp0g, f  p0g Sample selection Cuts 1, 2 Cuts 1, 2, 3

13. Dalitz plot analysis: photon pairing First and second best c2 photon pairing will be used to measure the quantity of wrong pairing p0 masses from best c2 pairing

14. Dalitz plot shape for data (bckg subtracted)

15. Dalitz plot: mass projections Achasov model with fixed parameters Backgroud rejection to be improved Efficiency in bin of Mpp and Mpg under evaluation Theoretical shape with all interferences in writing

16. Prospects for e+e wp0 p0p0p+p A. De Santis, S. Giovannella, L.Ingrosso, S.Miscetti Motivations: The analysis of this channel started since it is the most relevant background to the KSKL interference scheme with p0p0p+p final state in the DT0 region Moreover, the study of the x-sec vs s of this process gives the BR of f  wp0 [PDG03: BRfwp = ( 5.5 ± 1.5 ± 0.3 )  105 ]

17. Analysis scheme • Sample selection: 1 charged wertex with 2 tracks close to IP & 4 prompt neutral • clusters with cos q > 23° • 2. Kinematic fit with 4-momentum & g’s ToF constraints • 3. Photon pairing usin p0 masses • All all_phys MC + 2001 & 2002 scan data analyzed Normalized to number of entries – Data – MC – Before fit – After fit Mpg (MeV)

18. Before fit After fit • Data –MC signal – MC bckg • Data –MC sig + bckg MC bckg Background evaluation Background contamination obtained by fitting data with expected MC distributions Background contamination: around 10% Test of background shape will be done using the c2/ndf > 3 sample

19. First tentative fit to Mpp @  s =1019.6 MeV Mpp spectrum fitted with old functions Old analysis efficiency vs Mpp Systematic errors not included As for 2000 data, f0g + rp0 not enough to reproduce the shape Fit results using f0g + sg : 2000 fit results: Mf0 = (973 ± 1) MeV g2KK / 4p = (2.79 ± 0.12) GeV2 g2KK / g2pp = 4.00 ± 0.14 Asig= 0.93 ± 0.13 Fit 2000 This fit • Raw spectrum – Fit result