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Study of h  3 pions Dalitz Plot

Study of h  3 pions Dalitz Plot. Tiziana Capussela Universita’ di Napoli ”Federico II” LNF-Spring-School May 19 th -23 rd ,2003. Physics motivations. The decay h  3 p occours primarily on account of the “d-u” quark mass differences and the results arising from lowest order

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Study of h  3 pions Dalitz Plot

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  1. Study of h  3pions Dalitz Plot Tiziana Capussela Universita’ di Napoli ”Federico II” LNF-Spring-School May 19th-23rd,2003

  2. Physics motivations The decay h  3 p occours primarily on account of the “d-u” quark mass differences and the results arising from lowest order chiral pertubation theory is well known: With: It is clear that a good understanding of M(s,t,u) can lead to a very accurate determination of Q:

  3. There are different valuations of M(s,t,u), corresponding to different approximations, it is therefore very important to confront experimental results with precise theoretical calculations. We expand the decay amplitude about the center of the Dalitz plot as: |A(s,t,u)|2 = 1 + aY + bY2 + cX + dX2 + eXY Where:

  4. Theoretical results for the slope parameters of the various approximations [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) Experimental results for the slope parameters Tabella sperimentale di Bijnens

  5. +-0 We use the following decay chain +-00. The final state is +-. With the full KLOE statistics: N(+-0) = N()·BR(+-0)·sel = 0.217x108x0.23x0.37  1.8x106

  6. Comparison Data-MC  data  MC  data  MC A.U. A.U.  data  MC  data  MC The estimated backgroundis < 1%

  7. Resolutions and efficiency “core” res = 0.018 “core” res = 0.028 Efficiency  37%

  8. Fit procedure The Dalitz plot distribution as been fitted according to |A(X,Y)|2 = 1+aY+ bY2 +cX+ dX2+eXY The fit is done using a binned 2approach • 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.

  9. Tests of the fit procedure on MC

  10. Test of goodness of fit on MC 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)  92%

  11. Preliminary results Results of fitting +-0Dalitz plot density to |A(X, Y)|2 = 1 + aY + bY2 + cX + dX2 + eXY with 100 pb-1 of data corresponding to N(+-0)  352000 events in the Dalitz plot: Systematic corrections and errors are under study.

  12. Tests of the fit procedure on data

  13. Test of goodness of fit on data 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)  68%

  14. Work in progress 000 The final state is 7. The decay amplitude is parametrized as: A(z) 1 + gz N(000) = N()·BR(000)·sel = 0.217x108x0.33x0.16  1.15x106 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 .

  15. Conclusions The study of Dalitz plot density for h  3 p decays can be linked to “u-d” quark mass difference in the context of Chiral theories. KLOE is analysing 1.8x106+-0and 1.1x106000events in the Dalitz plot after all cuts with very small background. The fit procedure has been implemented and tested, showing clear sensitivity to quadratic slopes. Systematic corrections are under study.

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