Search for Direct CP Violation in 3-body Cabibbo Suppressed D 0 Decays Kalanand Mishra, G. Mancinelli, B. T. Meadows, M. D. Sokoloff University of Cincinnati Motivation Strategy Summary and outlook Charm AWG 08/17/2006

Kalanand MishraUniversity of Cincinnati2 CP Violation in D 0 Decay Look for particle  anti-particle rate differences  Where f is:  +  -  0 [  π, …] and K + K -  0 [K*K,  π 0, … ]. Decays to these final states are Cabibbo-suppressed, enhancing the possibility that interference with non-SM amplitudes could produce direct CP violation. CPV expected to be small in the charm sector SM predictions O(0.1%) CPV > 1% will be a strong evidence for non-SM processes 

Kalanand MishraUniversity of Cincinnati3 Why 3-body CS modes ? The best hope for SM predicted CP violation in Charm decays is in CS modes. The prediction for CF decays are too small. 3-body decays permit the measurement of phase differences which are required to create direct CP violation in the interference between SM and non- SM processes. These are relatively high statistics modes (45000 D 0 /D 0 bar  πππ 0 & 6800 D 0 /D 0 bar  KKπ 0 events). Since we can normalize measurements relative to the whole phase space (Dalitz plot), the dependence on π s tagging efficiency is negligible.

Kalanand MishraUniversity of Cincinnati4 Strategy need interference between diagrams with different strong (  i ) and weak phases (  i ) : Perform separate Dalitz plot analyses of D 0  π - π + π 0 (K - K + π 0 ) and D 0 bar  π + π - π 0 (K + K - π 0 ). Models have already been established in both cases that provide good description of data. direct CPV

Kalanand MishraUniversity of Cincinnati5 What is Known ? CLEO measure A CP in D 0  π - π + π 0 mode A CP = No A CP measurements available for D 0  K - K + π 0 Other analysis are under way to measure CP asymmetry in D 0  K - K +, π - π + modes A CP (K + K - ) = ± A CP (π + π - ) = ± A CP (π 0 π 0 ) = 0.00 ± 0.05 A CP (K + K - π + π - ) = ± 0.07 PDG 2006  Measure the difference between the integral of the coherent sum of all amplitudes across the DP for D 0 and D 0 bar, divided by the area of the DP.

Kalanand MishraUniversity of Cincinnati6 Dalitz Plot Fit Results: π - π + π 0 BAD 1174

Kalanand MishraUniversity of Cincinnati7 Dalitz Plot Fit Results: K - K + π 0 BAD 1502

Kalanand MishraUniversity of Cincinnati8 What we have looked at ? Our sensitivity to observe CP asymmetry is higher in the D 0  π - π + π 0 decay because of the higher statistics in this mode. However, I have started with D 0  K - K + π 0 mode since recently I have been working on this Dalitz plot analysis. Start by looking at the distribution of moments of the cosine of the helicity angle in data for both D 0 and D 0 bar events. Then perform separate Dalitz plot fit for CP conjugate events.

Kalanand MishraUniversity of Cincinnati9 Moments of cos  H [K + π 0 ] D 0 __ D 0

Kalanand MishraUniversity of Cincinnati10 Moments of cos  H [K - π 0 ] D 0 __ D 0

Kalanand MishraUniversity of Cincinnati11 Moments of cos  H [K - K + ] D 0 __ D 0

Kalanand MishraUniversity of Cincinnati12 Separate DP Fits f 0 (980) 0.65 ± ± ± ± f2’(1525) 1.12 ± ± ± ±  (1020) 0.74 ± ± ± ± K* - (892) 0.64 ± ± ± ± K* + (1410) 0.64 ± ± ± ± K* - (1410) 2.91 ± ± ± ± K + π 0 SW 4.50 ± ± ± ± K - π 0 SW 4.92 ± ± ± ± AmplitudePhase D0D0 D 0 bar D0D0 # SD

Kalanand MishraUniversity of Cincinnati13 Separate DP Fits K* - (892) 0.63 ± ± ± ± K* + (1410) 0.30 ± ± ± ± K* - (1410) 2.80 ± ± ± ± K + π 0 SW 4.85 ± ± ± ± K - π 0 SW 4.78 ± ± ± ± AmplitudePhase D0D0 D 0 bar D0D0 # SD Parameters for CP eigen states are fixed to the ones obtained from the combined fit.

Kalanand MishraUniversity of Cincinnati14 Summary After performing D 0  π - π + π 0, K - K + π 0 Dalitz plot analysis, we have started looking into CP asymmetries in the conjugate decays. We will keep documenting (BAD 1531) as we move along. We aim for a preliminary result for DPF 2006.