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Study of h  ppp Dalitz plot at KLOE. F.Ambrosino Università e Sezione INFN, Napoli for the KLOE collaboration. Motivations h  p + p - p 0 h  p 0 p 0 p 0 Conclusions and outlook. h  3p in chiral theory. The decay h  3 p occours primarily on account of the d-u

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Study of h ppp Dalitz plot at KLOE

F.Ambrosino

Università e Sezione INFN, Napoli

for the KLOE collaboration

  • Motivations

  • h p+p-p0

  • h p0p0p0

  • Conclusions and outlook

Euridice Midterm Meeting

LNF 11/02/05


H 3p in chiral theory
h3p in chiral theory

The decay h  3 poccours primarily on account of the d-u

quark mass differences and the result arising from lowest order

chiral pertubation theory is well known:

And, at l.o.

With:

A good understanding of M(s,t,u) can in principle lead to a very accurate determination of Q:

Euridice Midterm Meeting

LNF 11/02/05


And its open questions
…and its open questions

  • Still there are some intriguing questions for this decay :

  • Why is it experimental width so large (270 eV) w.r.t theoretical calculation ? (Tree level: 66 eV (!!!); 1 loop : 160 eV ) Possible answers:

    • Final state interaction

    • Scalar intermediate states

    • Violation of Dashen theorem

  • Is the dynamics of the decay correctly described by theoretical calculations ?

  • Euridice Midterm Meeting

    LNF 11/02/05


    Dalitz plot expansion
    Dalitz plot expansion

    The usual expansion of square modulus of the decay amplitude about the center of the Dalitz plot is:

    |A(s,t,u)|2 = 1 + aY + bY2 + cX + dX2 + eXY

    Where:

    Euridice Midterm Meeting

    LNF 11/02/05


    Dalitz expansion theory vs experiment
    Dalitz expansion: theory vs experiment

    [1] Gasser,J. and Leutwyler, H., Nucl. Phys. B 250, 539 (1985)

    [2] Kambor, J., Wiesendanger, C. and Wyler, D., Nucl. Phys. B 465, 215 (1996)

    Tabella sperimentale di Bijnens

    Euridice Midterm Meeting

    LNF 11/02/05


    H 3p at kloe
    h 3p at KLOE

    At KLOE h is produced in the process f hg .

    The final state for h p+p-p0is thus +-, and the final state for h p0p0p0 is 7g, both with almost no physical background.

    • Selection:

    • 2 track vertex+3 g candidates

    • Kinematic fit

    Euridice Midterm Meeting

    LNF 11/02/05


    Resolutions and efficiency

    “core”

    sX = 0.018

    Resolutions and efficiency

    “core”

    sY = 0.027

    Efficiency almost flat, and  36%

    Euridice Midterm Meeting

    LNF 11/02/05


    Comparison d ata mc p
    Comparison Data-MC:p+

    Euridice Midterm Meeting

    LNF 11/02/05


    Comparison d ata mc p1
    Comparison Data-MC:p-

    Euridice Midterm Meeting

    LNF 11/02/05


    Signal
    Signal

    B/S  0.8%

    Euridice Midterm Meeting

    LNF 11/02/05


    Fitting function
    Fitting function

    • The analysis has been applied on 450 pb–1 corresponding to:

    • N(+-0) = 1,425,131

    • events in the Dalitz plot, fitted with function:

    • fit is stable…

    • …but the model seems not to fit adeguately data (BAD Pc2).

    • We have added the cubic terms:

    |A(X,Y)|2 = 1+aY+bY2+cX+dX2+eXY

    |A(X,Y)|2 = 1+aY+bY2+cX+dX2+eXY+fY3+gX3+hX2Y+lXY2

    Euridice Midterm Meeting

    LNF 11/02/05


    Fit stability
    Fit stability

    Euridice Midterm Meeting

    LNF 11/02/05


    Results
    Results

    |A(X,Y)|2 = 1+aY+bY2+cX+dX2+eXY+fY3

    Euridice Midterm Meeting

    LNF 11/02/05


    Results ii
    Results (II)

    |A(X,Y)|2 = 1-1.072 Y+0.117 Y2+0.047 X2+0.13Y3

    Using preliminary KLOE results shown at ICHEP 04

    B.V. Martemyanov and V.S. Sopov (hep-ph\0502023) have extracted:

    Q = 22.8 ± 0.4 against Qdashen= 24.2

    (as already argued for example in J. Bijnens and J. Prades, Nucl. Phys. B490, 239 (1997)

    Euridice Midterm Meeting

    LNF 11/02/05


    H 3p 0 dalitz plot expansion
    h  3p0 : Dalitz plot expansion

    The dynamics of the h  p0 p0 p0 decay can be studied analysing the Dalitz plot distribution.

    The Dalitz plot density ( |A|2 ) is specified by a single parameter:

    |A|2  1 +2z

    with:

    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 .

    Euridice Midterm Meeting

    LNF 11/02/05


    Dalitz expansion theory vs experiment1
    Dalitz expansion: theory vs experiment

    [1] Gasser,J. and Leutwyler, H., Nucl. Phys. B 250, 539 (1985)

    [2] Kambor, J., Wiesendanger, C. and Wyler, D., Nucl. Phys. B 465, 215 (1996)

    Euridice Midterm Meeting

    LNF 11/02/05


    Photons pairing
    Photons pairing

    Recoil  is the most energetic cluster.

    In order to match every couple of photon to the right 0we build a 2-like variable for each of the 15 combinations:

    With:

    is the invariant mass of i0for j-th combination

    = 134.98 MeV

    is obtained as function of photon energies

    Euridice Midterm Meeting

    LNF 11/02/05


    Combination selection

    Pur  92 % Eff  14 %

    Pur  85 % Eff  22 %

    Pur  98 % Eff  4.5 %

    Combination selection

    • Cutting on:

      • Minimum 2 value

      • 2 between “best” and “second” combination

      • One can obtain samples with different purity-efficiency

      • Purity= Fraction of events with all photons correctly matched to p0 ‘s

    Euridice Midterm Meeting

    LNF 11/02/05


    The problem of resolution
    The problem of resolution

    MC reconstructed

    Phase space

    Resolution

    Efficiency

    Euridice Midterm Meeting

    LNF 11/02/05


    Results on mc
    Results on MC

    Euridice Midterm Meeting

    LNF 11/02/05


    Results on mc1
    Results on MC

    Euridice Midterm Meeting

    LNF 11/02/05


    Results on mc2
    Results on MC

    Euridice Midterm Meeting

    LNF 11/02/05


    Comparison data mc
    Comparison Data - MC

    The agreement is good on all spectra

    Euridice Midterm Meeting

    LNF 11/02/05


    Fitting data

    = -0.0ZZ  0.004

    = -0.0XX  0.002

    = -0.0YY  0.002

    Fitting Data

    Low purity

    High purity

    Medium purity

    Systematics are at the same level of the statistical error

    Euridice Midterm Meeting

    LNF 11/02/05


    Conclusions
    Conclusions

    • KLOE is analyzing an unprecedented statistics of h3p decays with negligible background

    • For p+p-p0 channel the analysis is almost completed and finds evidence for an unexpected large y3 term

    • 3 p0 analysis is much harder, we expect to provide soon a result at the same level of the Crystal Ball one.

    Euridice Midterm Meeting

    LNF 11/02/05


    Spare slides
    SPARE SLIDES

    Euridice Midterm Meeting

    LNF 11/02/05


    Kinematic fit with no mass constrains

    Euridice Midterm Meeting

    LNF 11/02/05


    Tests of the fit procedure on MC

    Generator slopes in

    MC rad-04:

    a = -1.04

    b = 0.14

    c = 0.

    d = 0.06

    e = 0.

    KLOE measure (100 pb-1)

    Euridice Midterm Meeting

    LNF 11/02/05


    Comparison Data-MC

     data

     MC

    A.U.

    Euridice Midterm Meeting

    LNF 11/02/05


    NA48: 547.843  0.030st  0.041sys

    Physica ScriptaT99 140-142, 2002

    Shift  0.03 MeV

    Comparison Data-MC: Ych – Y0

    Shift  1.33 MeV

    Euridice Midterm Meeting

    LNF 11/02/05


    Fit procedure

    The fit is done using a binned 2 approach

    • i is for each bin: the efficiency as a function of Dalitz-plot.

    • Ni is for each bin: the number of events of Dalitz-plot.

    • i is the statistical error on the ratio Ni /i

    • All the bins are included in the fit apart from the bins crossed by the Dalitz plot contour.

    Euridice Midterm Meeting

    LNF 11/02/05


    Comparison Data-MC: X & Y

    Euridice Midterm Meeting

    LNF 11/02/05


    Goodness of fit
    Goodness of fit

    Comparison between efficiency corrected data and

    fitted function as function of the bin number.

    The structure observed is due to the Y distribution for X slices

    P(2 02)  60%

    Euridice Midterm Meeting

    LNF 11/02/05


    Asymmetries

    2

    1

    63876

    64082

    196264

    196104

    304930

    304455

    577741

    577849

    209043

    209204

    381585

    381637

    3

    4

    Asymmetries

    -

    +

    As = (0.07  0.09)  10-2

    A = (-0.009  0.093)  10-2

    Aq = (-0.02  0.09)  10-2

    Euridice Midterm Meeting

    LNF 11/02/05


    H p p p 0 g
    h p+p-p0(g)

    We have tested the effect of radiative corrections to the Dalitz plot density.

    The ratio of the two plots has been fitted with the usual expansion: corrections to parameters are compatible with zero

    Euridice Midterm Meeting

    LNF 11/02/05


    H p p p 0 time stability
    h p+p-p0 : time stability

    To check stability wrt data taking conditions we fit the integrated Dalitz plot in samples of 4 pb-1 each

    Euridice Midterm Meeting

    LNF 11/02/05


    eReal (X,Y)

    eReal (X,Y)

    1+aY+bX2

    |A(X,Y)|2

    eMC(X,Y)

    eMC(X,Y)

    Check on cubic term

    Fitted function is actually :

    Assume:

    No cubic dependence in |A(X,Y)|2

    |A(X,Y)|2 = 1 + aY + bY2 + dX2 with a  -1.

    Can evaluate a such as to mimic the cubic term.

    Euridice Midterm Meeting

    LNF 11/02/05


    MC

    MC weighted

    p+

    MC

    MC weighted

    p-

    Euridice Midterm Meeting

    LNF 11/02/05


    Sample selection
    Sample selection

    • The cuts used to select: h  p0 p0 p0 are :

    • 7 and only 7 prompt neutral clusters with 21° < < 159°

    • and E> 10 MeV

    • opening angle between each couple of photons > 18°

    • Kinematic Fit with no mass constraint

    • 320 MeV < Erad < 400 MeV

    • P(2) > 0.01

    Euridice Midterm Meeting

    LNF 11/02/05



    Second kinematic fit
    Second kinematic fit

    Once a combination has been selected, one can do a second kinematic fit imposing 0 mass for each couple of photons.

    Euridice Midterm Meeting

    LNF 11/02/05


    Doing it the hard way
    Doing it the hard way..

    Still we minimize:

    But now:

    ni = recostructed events

    i= fromeach single MC recostructed event weighted

    with the theoretical function

    Euridice Midterm Meeting

    LNF 11/02/05


    Comparison data mc ii
    Comparison Data – MC (II)

    The center of Dalitz plot correspond to 3 pions with the same energy (Ei = M/3 = 182.4 MeV). A good check of the MC performance in evaluating the energy resolution of 0 comes from the distribution of E0 - Ei for z = 0

    Euridice Midterm Meeting

    LNF 11/02/05


    Comparison data mc ii1
    Comparison Data – MC (II)

    E*g1 - E*g2

    Vs.

    Ep

    Euridice Midterm Meeting

    LNF 11/02/05


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