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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 - 

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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 -  - PowerPoint PPT Presentation


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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
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
D0Ks K+ K- Dalitz plot
  • Detached sample, no tagging
  • 2900 runs

(Each point is doubly entered)

f(1020)

Amir Rahimi/FOCUS

slide3
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
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
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
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
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
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
Likelihood profiles for the combined low and side bandsD+ 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
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
D+ 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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