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Status Report on f p 0 p 0 g analysis. S. Giovannella, S.Miscetti. Generators for e + e wp 0 p 0 p 0 g Study of the f hg p 0 p 0 p 0 g background Standard analysis vs s Dalitz plot. Comparison of e + e wp 0 p 0 p 0 g generators.
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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
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
Comparison of e+e wp0 p0p0ggenerators GEN2 GEN3 GEN1 30k events of GEN2 and GEN3 compared with data for s = 1019.6 MeV
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
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
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
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
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
Visible x-sec vs s • p0p0g : line shape from fhg 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+pp0p0 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
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
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
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
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 DT0 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 ) 105 ]
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)
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
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