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Progress in D 0 K s K + K - and Dº  K s K analysis Results from an exercise Dalitz fit for D +  K + K -  + D 0 K s K + K - Dalitz plot Detached sample, no tagging 2900 runs (Each point is doubly entered) f(1020) D 0 K s K + K - Dalitz plot, tagged sample

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Slide1 l.jpg

  • Progress in D0Ks K+ K- and Dº Ks K analysis

  • Results from an exercise Dalitz fit for D+ K+K- +

Amir Rahimi/FOCUS


Slide2 l.jpg

D0Ks K+ K- Dalitz plot

  • Detached sample, no tagging

  • 2900 runs

(Each point is doubly entered)

f(1020)

Amir Rahimi/FOCUS


Slide3 l.jpg

D0Ks K+ K- Dalitz plot, tagged sample

D*++D0  K0barK+ K-

Look for resonances in either K+ K- or K0bar K+ and vice versa.

Detached sample with the D* tagging.

Determine the strangeness of the Ks by tagging the charm of the D0

Decay trees for this D0 decay mode, showing some possible resonances which couple u and d quarks to s quarks:

a0(980)

a0(980)?

f0(980)?

f0(980)

f(1020)?

f(1020)

Amir Rahimi/FOCUS


Slide4 l.jpg

f0(980) simulation from Rodney Green’s thesis. y axis is M2(K-pi+) and x axis is M2(K- K+).

How is a0+ (980) simulated in MCFocus?

  • Simulated the following decay and its c.c.

  • D*+ D0p+

  • a0+ (980) K-

  •  Ks K+

  •  p+ p -

  • The Dalitz plot is populated according to a0+ (980) decay.

Amir Rahimi/FOCUS


Slide5 l.jpg

Revisit DºKs K with higher statistics

Recall we fit four signal yields to a function of 3 variables

+

+

  • N = total yield

  •  = Charm-anti-Charm asymmetry (fragmentation dynamics)

+

The ² of this fit of 3 parameters with 4 dof is a test of hypothesis that CP is conserved which model is based on.

Amir Rahimi/FOCUS


Slide6 l.jpg

Example of the fit with higher statistics

obs

pred

N

21.1

25.4

D*+K+

N

61.0

56.5

D*+K-

N

35.1

40.1

D*-K+

N

26.7

18.0

D*-K-

D0K+

D0K-

obs

pred

N

136

136

D*+K+

N

330

330

D*+K-

D0BarK-

N

320

320

D0BarK+

D*-K+

² =0.0011 for 1 dof CL=99%

N

132

132

D*-K-

Detached sample (no out of target cut):

N=140

=0.17

fK+=.31 (too Low!)

  • This was in October

² =3.13 for 1 dof CL=7.71%

What’s up with the widths?!

N=919

=0.015

fK+=.292 (lower!)

  • This is NOW

Amir Rahimi/FOCUS


Slide7 l.jpg

Summary

  • We have looked at D0Ks K+ K- Dalitz plot with 2900 runs

    • D* tagging virtually eliminates the background

    • There is a clear indication of f(1020) resonance as well as some indications of both f0(980) and a0(980) resonances.

    • It appears that MCFocus simulates a0(980) with the correct matrix element

    • We are in the process of learning how to fit for a0(980)

  • We repeated our CPV studies of DºKs K with higher statistics

    • A significant improvement in ²

    • The charm anti-charm asymmetry is around =0.015; more reasonable compared to =0.17

    • We are seeing fK+=0.292 (+/- 0.023), the PDG value is fK+= 0.439 (+/- 0.1)

  • Amir Rahimi/FOCUS


    A practice dalitz fit with d k k l.jpg

    D+ K+K- + sample (provided by JEW):

    • We pick a “dirty” sample for this study

    • First we do do a log likelihood fit to the combined sample from low and high side bands; this is our background fit

    • Then we do a log likelihood fit to the signal region

    • The asymmetry in K*(890) lobes in signal suggests interference with K*(1430)

    A practice Dalitz fit with D+ K+K- +

    f(1020) No Zemach nodes

    K*(1430)

    f(1020)

    K*(890)

    high s.b.

    Low s.b.

    signal

    K*(890) No Zemach nodes

    Amir Rahimi/FOCUS


    D k k background fit l.jpg

    Likelihood profiles for the combined low and side bands

    D+ K+K- +background fit

    • For the background fit intensity function we pick two Breit-Wigners for f and K*(890) and a flat background

    • We fit for f and K*(890) amplitudes, fixing the flat background at unity

    f

    K*(890)

    Low side band overlays of data and the background intensity function(the fit quality with the high side band is similar to this):

    K*(890)

    f

    K+  +

    K-  +

    K-K+

    Amir Rahimi/FOCUS


    D k k signal fit l.jpg

    • We fix the parameters in the background probability density function to the values we obtained from our fit to the background.

    • For the signal region we pick

      • three Breit-Wigners for f, K*(890) and K*(1430)

      • Zemach factors for f and K*(890)

      • two complex phases and two amplitudes.

    • Do a log likelihood fit to the signal probability density function

    Clean sample

    D+ K+K- +signal fit

    f

    K*(1430)

    Log likelihood profiles:

    phase

    The results match the likelihood profiles that we obtain using a clean D+ K+K- + sample in which we do not fit for the background (the arrows indicate the clean sample minimums)

    Amp.

    Amir Rahimi/FOCUS


    D k k dalitz projections l.jpg
    D function to the values we obtained from our fit to the background.+ K+K- + Dalitz projections

    • Putting it all together, we overlay the Dalitz squared mass projections of the combined probability density function and the data

    • The overlays match reasonably well

    f lobes

    K*(890)

    f lobes

    f

    K*(890) lobes

    K-  +

    K-K+

    K+  +

    Amir Rahimi/FOCUS


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