Dynamics of  →...

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  • F. Ambrosino T. Capussela F. Perfetto

  • OUTLINE KLOE Memo n. 359

    = 0.027 0.004 stat 0.006 syst (blessed 19/07/2007; KLOE preliminary arXiv 0707.4137) Selection scheme & fit procedure & systematics evaluations Introduction of a new selection scheme: NEW approach NEW or OLD approach ?

    KLOE Memo n. 359 + x

    Update on the measurement using different samples Final results

  • Dalitz plot expansion>3 @ KLOEThe decay 3 violates iso-spin invariance and it is induced dominantly by the strong interaction via the ud quark mass difference. The Dalitz plot density corresponding to the intrinsic 0 0 0 decay amplitude is approximately described by |A|2 1 + 2zWith:Z [ 0 , 1 ] Ei = Energy of the i-th pion in the rest frame. = Distance to the center of Dalitz plot. max = Maximun value of .

  • Theory vs Experiment >3 @ KLOECalculations for : J.Kambor et al. (1996): 0.007 or 0.0014 B.Borasoy et al. (2005): 0.031 0.003 J.Bijnens et al. (2007): 0.013 0.032Experimental results for :GAMS-2000 (1984): 0.022 0.023 CBarrel at LEAR (1998): 0.052 0.017 0.010 CBall at AGS (2001): 0.031 0.004 KLOE (prelim.2005): 0.013 0.004 0.005 CELSIUS-WASA (2007): 0.026 0.010 0.010 KLOE (prelim.2007): 0.027 0.004 0.005 CBall at MAMI-B (2009): 0.032 0.002 0.002 CBall at MAMI-C (2009): 0.032 0.003 Experiment: = 0.031 0.004 KLOE, CBall and WASA consistent ChPT LO: = 0 ChPT one and two loop: > 0 Quark masses from 000? [ DeAndrea, Nehme, Talavera PRD78(2008)034032 ]

  • Frascati 19 Luglio 2007Sample selectionThe cuts used to select: 0 0 0 are:

    7 and only 7 prompt neutral clusters with 21 10 MeV Opening angle between each couple of photons > 18 Kinematic Fit with no mass constraint P(2) > 0.01 320 MeV < Erec < 400 MeV (after kin fit)

    The overall common selection efficiency (trigger, reconstruction, EVCL) is = (30.30 0.01)%With these cuts the expected contribution from events other than the signal is < 0.1%

  • Matching to 0 s In order to select the best 0 0 0 pairing, we introduce a pseudo2 variable for each of the 15 possible pairs, cutting on: Minimum 2 value 2 between best and second combinationone can obtain samples with different purity-efficiency22min 2min 2

  • Matching to 0 s In order to select the best 0 0 0 pairing, we introduce a pseudo- 2 variable for each of the 15 possible pairs, cutting on: Minimum 2 value 2 between best and second combinationone can obtain samples with different purity-efficiency2

    After pairing we perform kinematic fit with and 0 mass constraint mass: MMC = 547.30 MeV /c2 MData = 547.822 MeV/c2 2

  • Samples

    LOWMED IMED IIMED IIIHIGHmin 2NO CUT< 10< 5< 3< 2 2NO CUT> 1.2> 3> 4> 7 PUR75.4 %84.5 %92 %94.8 %97.6 %RES0.20030.16630.12870.10990.087130.3 %22 %13.6 %9.2 %4.3 % / 8 %14 %21 %25 %26 %N(Mevts)1.4181.0290.64590.44530.2123

  • ni = recostructed eventsi = for each MC event (according pure phase space): Evaluate its ztrue and its zrec (if any!) Enter an histogram with the value of zrec Weight the entry with 1 + 2 ztrue Weight the event with the fraction of combinatorial background, for the signal (bkg) if it has correct (wrong) pairingWhere:We obtain an extimate by minimizingThe fit is done using a binned likelihood approachThis procedure relies heavily on MC.Fit procedure

  • Test on fit procedure (I)We have tested the fit procedure in different ways: Looking at the result of our fit on MC (MC = 0.)

    LowMed I Med IIMed IIIHigh0.0009 0.00190.0002 0.00210.0008 0.0026 0.0022 0.00300.0029 0.0044

  • Test on fit procedure (II)We have tested the fit procedure in different ways: Looking at the result of our fit on MC (MC = 0.)

    Using hit or miss and our reweighting we have generated samples with different values of and then we have compared the two procedures.

  • Test on fit procedure (III)We have tested the fit procedure in different ways: Looking at the result of our fit on MC pure phase space (MC = 0.) Using hit or miss and the fit procedure we have generated samples with different values of and then we have compared the two procedures.

    Parameter scan:

    Range = 0. = 0.026 = 0.028 = 0.030 = 0.032 = 0.034 = 0.036 = 0.038 0 1 1015 %25%16% 40% 21%12% 13%8 %0 0.9108 %84%75%78%59%41%26%18%0 0.8107% 73% 64% 67% 52% 35% 23% 17%0 0.7106 % 85% 83% 83% 71% 73% 54% 78%0 0.6106 % 94% 93%95% 88% 89% 83% 78%

  • Frascati 19 Luglio 2007Mean 134.2RMS 11.83Mean 134.2RMS 11.99Systematic checks

  • Systematic checkvs

  • Systematic check

  • Systematic checksN2/N1 exp. = 0.7263 0.0002

    N3/N1 exp. = 0.4497 0.0002

    N4/N1 exp. = 0.3048 0.0002

    N5/N1 exp. = 0.1431 0.0001N2/N1 obs = 0.7258 0.0004

    N3/N1 obs. = 0.4556 0.0004

    N4/N1 obs. = 0.3140 0.0004

    N5/N1 obs. = 0.1498 0.0003

  • Systematic check

  • Systematic check

  • Frascati 19 Luglio 2007Systematic check

  • Results2/ndf = 13.72 / 17.

  • Dalitz plot expansionOLD approach:

    7 and only 7 pnc with 21 < < 159 and E > 10 MeV > 18 Kin Fit with no mass constraint

    P(2) > 0.01 320 MeV < Erad < 400 MeV

    AFTER PHOTONS PAIRING

    Kinematic Fit with and 0 mass constraints (on DATA M = 547.822 MeV/c2 )

  • NEW vs OLD

    Pur %NewPur %OldRmsNewRmsOld %New %OldData/McwpfNewData/McwpfOldLow82.2 75.4.1864.200312.481.111.07MedI89.484.5.1465.166315.8141.221.07MedII95.192.1.1141.128721.9211.531.12Med III97.194.8.097.109927.6251.971.15High99.097.6.080.087126.726Not converge1.35

  • Results OLD vs NEW

    RangeLow 103Medium I 103Medium II 103Medium III 103High 103(0, 1) 30 2 31 2 31 3 25 3 26 4(0, 0.8) 26 2 28 2 28 3 22 4 22 5(0, 0.7) 26 3 28 3 27 4 21 4 23 5(0, 0.6) 30 4 31 4 31 4 24 5 20 6

    (0, 1) 36 2 37 2 37 2 35 3(0, 0.8) 36 2 37 2 34 3 32 3 (0, 0.7) 38 2 40 3 36 3 33 3(0, 0.6) 44 3 48 4 42 4 37 4

  • NEW APPROACHOLD APPROACHNEW or OLD ?OLD APPROACH !!

  • II Part MEMO 359 + x

  • Dalitz plot expansionNow we have updated the measurement of a using:

    Before the kinematic fit : qgg > 9

    In the kinematic fit on data : Mh = 547.874 0.007 0.031 MeV/c2

    MC sample generated according to a = -0.027

    New samples with different purity - efficiency

    A correction of about 2% to the photon energies in the p0 rest frame.

  • qgg > 9

  • qgg > 9

  • qgg > 9 Low

    Med

    High

    g >18 > 15 > 12 > 9 > 6 = 0

    PUR %9190.790.690.590.490.3 De %18.415.612.410.79.99.6 PUR %95.495.395.295.19595De %221812.610.3108.8 PUR %97.697.597.497.397.297.1De %161312109.68

  • qgg > 9 Low

    Med

    High

    g >18 > 15 > 12 > 9 > 6 = 0

    PUR %9190.790.690.590.490.3 De %18.415.612.410.79.99.6 PUR %95.495.395.295.19595De %221812.610.3108.8 PUR %97.697.597.497.397.197.1De %1613121088

  • Ponza 05 June 2008Status report on analysisWell use MC generated with: = - 0.027.

    On this MC sample:a = - 0.027 0.002

    New MC sample We have generated MC samples with different a values in input and we have fitted a on data:

    a input MC a fit on data0-0.028 0.004-0.026-0.026 0.004-0.028-0.028 0.004-0.030-0.027 0.004-0.032-0.027 0.004-0.034-0.027 0.004-0.036-0.027 0.004-0.038-0.027 0.004-0.040-0.027 0.004-0.042-0.027 0.004-0.044-0.027 0.004-0.046-0.027 0.004-0.048-0.027 0.004

  • LOWDc2 > 2.5Pur 90.4%e 21%De / e 11%Res 0.1335N = 948471MEDIUMDc2 > 5Pur 95%e 14%De / e 10%Res 0.1108N = 614663

    HIGHDc2 > 9Pur 97.3%e 7%De / e 10%Res 0.096N = 333493

    3 new samplesWe have fix the cut on min c2< 5 obtaining:

  • Status report on analysisResolution & efficiency

  • CorrectionWe have corrected the Data / MC discrepancy (at level of 1.5 %) with a smearing of the photon energies, obtaining:

  • CorrectionWe have recovered the residual discrepancy (Low: h = 0.; Med: h= 0.6%; High: h =0.9%), obtaining

    RangeLow 104Medium 104High 104(0, 1) 288 22 281 26 289 34(0, 0.8) 313 26 288 31 295 42(0, 0.7) 319 29 301 35 308 47(0, 0.6) 348 31 330 44 343 60

  • Residuals in [0 0.7] = 0.0301 0.0035stat

  • Systematic checks: Resolution

  • Systematic checks: Resolution

  • Systematic checks: Resolution

  • Systematic checks: ResolutionThe systematic uncertainty due to the resolution is obtained considering the fluctuation in the RMSdata / RMS MC

    EffectLOW 104MEDIUM 104HIGH 104Res-4 +4-4 +4 -2 +2

  • Systematic checks: EfficiencyDATANHigh / Nlow = 0.3516 0.0007NMedium / Nlow = 0.6481 0.0011MCNHigh / Nlow = 0.3511 0.0003NMedium / Nlow = 0.6461 0.0005

  • Systematic checks: EfficiencyCorrection to the photon efficiency is applied weighting the Montecarloevents with a Fermi Dirac function obtained fitting the photon energy spectrum Data/MC discrepancy

  • Systematic checks: EfficiencyHighMediumLow

    EffectLOW 104MEDIUM 104HIGH 104Low E-5-3-5

  • On DATA:Wrong pair fraction (MC) = 5 %Wrong pair fraction (DATA) = (5.51 0.68) %

    Wrong pair fraction (MC) = 2.7 %Wrong pair fract