1. Cincinnati, May 09- 2005 Kalanand Mishra Kalanand Mishra University of Cincinnati Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K -  +  0 decay

2. Cincinnati, May 09- 2005 Kalanand Mishra Initial Goal for this Analysis : Measuring the Relative Branching Fractions for the Cabibbo-suppressed modes (D 0  -  +  0 & D 0  K - K +  0 ) relative to the Cabibbo-favored mode D 0  K -  +  0 : D 0  π - π + π 0 D 0  K - π + π 0 (a) BR( D 0  π - π + π 0 ) / BR( D 0  K - π + π 0 ) D 0  K - K + π 0 D 0  K - π + π 0 (b) BR( D 0  K - K + π 0 ) / BR( D 0  K - π + π 0 ) using 230 fb -1 data collected by the BaBar detector at the PEP-II B Factory at SLAC during runs 1,2,3,4 (May 1999 - August 2004).

3. Cincinnati, May 09- 2005 Kalanand Mishra The Decay Chain We search for decays of type D* +  D 0  s + D 0  -  +  0, D 0  K - K +  0, D 0  K -  +  0  0    The D* + is produced at interaction point from the ccbar continuum, and they have a negligible life-time.  “  s ” is a “slow pion”, produced with very low momentum.  D 0  -  +  0, D 0  K - K +  0 are Cabibbo-suppressed decay modes.  D 0  K -  +  0 is the Cabibbo-favored decay mode. We use this mode as normalization channel for the ratio of BRs measurement.  As usual (!), the CP conjugate mode is implied.

4. Cincinnati, May 09- 2005 Kalanand Mishra B-Factory at SLAC PEP-II accelerator schematic and tunnel view 9 GeV e - 3.1 GeV e + Record: L=9.2x10 33 cm -2 s -1 I LER =2450 mA, I HER =1550 mA, 1588 bunches (1x10 33 cm -2 s -1 ~ 1 B pair/s) 232M B pairs

5. Cincinnati, May 09- 2005 Kalanand Mishra BaBar Detector BaBar Detector Cerenkov Detector(DIRC)   c = 2.5 mrad 1.5 T solenoid Electromagnetic Calorimeter  E /E = 3.0%,  ,  = 4 mrad Drift Chamber  pt /p = 0.5% Instrumented Flux Return muon and K L detector Silicon Vertex Tracker  z =65  m,  d0 =55  m e + (3.1 GeV) e - (9 GeV)

6. Cincinnati, May 09- 2005 Kalanand Mishra Data Samples èMost ( ~ 90% ) data is taken at  (4S) resonance èIntegrated Luminosity ~ 230 fb -1 (ON + OFF Resonance) èWe use both on-resonance and off-resonance data for this analysis èFor Background studies and cut optimization : Continuum Monte Carlo : ccbar ~ 179 million  For detection efficiency: Signal Monte Carlo : ~ 1.4 million for K - K +  0 ~ 3.5 million for  -  +  0 ~ 4.5 million for K -  +  0

7. Cincinnati, May 09- 2005 Kalanand Mishra Track Selection è Kaon & pion tracks è Transverse momentum of the track > 0.10 GeV/c è Number of drift chamber hits ≥ 12 è ≥ 2 SVT r-phi (z) hits with at least 1 hit on inner 3 r-phi (z) layers è ≥ 6 total SVT hits è  soft track è No requirement on drift chamber hits è ≥ 2 SVT r-phi (z) hits with at least 1 hit on inner 3 r-phi (z) layers è ≥ 6 total SVT hits è  0 Reconstruction   Candidates with  Single calorimeter bumps not matched with any track  Energy of each photon > 100 MeV   0 Energy > 0.350 GeV  0.115 GeV/c 2 < M  < 0.160 GeV/c 2

8. Cincinnati, May 09- 2005 Kalanand Mishra Particle Identification Charged particle Candidates are identified by means of measured energy-loss (dE/ dx) in drift chamber together with information from particle identification system (DIRC).For each particle hypothesis ( , K, p, , e ) a likelihood is calculated based on these informations. We use a strict likelihood for kaon and pion charged tracks.  Pion PID  Kaon PID

9. Cincinnati, May 09- 2005 Kalanand Mishra D 0  h - h +  0 Reconstruction  Multi-hadron events with at least three charged tracks  h - and h + tracks are fit to a vertex  Mass of  0 candidate is constrained to m  0 at h - h + vertex  Unconverged fits are rejected  1.70 GeV/c 2 < M ( h - h +  0 ) < 2.0 GeV/c 2  P CM ( D 0 ) > 2.77 GeV/c D* Reconstruction : è D* + candidate is made by fitting the D 0 and the  s + to a vertex constrained in x and y to the measured beam-spot for the run. è |m D* - m D0 - 0.1455| < 0.001 GeV/c 2 è D* + vertex  2 < 20.0 è Unconverged fits are rejected

10. Cincinnati, May 09- 2005 Kalanand Mishra  -  +  0 mass plot  -  +  0 mass plot from real data showing the signal (yellow color) and side band (red color) regions.

11. Cincinnati, May 09- 2005 Kalanand Mishra Multiple Candidates èWe observed multiple D 0  h - h +  0 candidates per event with multiplicity ~ 7 - 8 % (ie, average 1.07 - 1.08 candidates/event). èWith tighter (< 1 MeV) m D* - m D0 cut, the multiple candidates decrease to ~ 3% level. èMultiplicity due to following reasons : nRight D 0 combined with a fake  soft + to make a D* +. nCharged track combinatorics. nMore than one  0 candidates with or without a shared photon. nFake / mis-constructed  0 èSelect the D 0 candidate which has the smallest  2 at D* vertex. èBy looking at Monte Carlo we see that ~ 60 % of the time we choose the correct candidate.

12. Cincinnati, May 09- 2005 Kalanand Mishra Mass plots for the three modes K -  +  0  -  +  0 K - K +  0 Data Ccbar Signal MC

13. Cincinnati, May 09- 2005 Kalanand Mishra K -  +  0 yield K -  +  0 mass distribution (dots) and the result of the fit (blue line) with three Gaussians for the signal and a second order polynomial term for the background (broken red line).

14. Cincinnati, May 09- 2005 Kalanand Mishra  -  +  0 mass distribution (dots) and the result of the fit (blue line) with two Gaussians for the signal and an exponential term for the background (red broken line). No specific fit for the reflection peak in the plot on left. I take the yield from the fit on right. I am still trying to understand and include in fit the reflection peak in the lower side band.  -  +  0 yield

15. Cincinnati, May 09- 2005 Kalanand Mishra Reflection Study K -  +  0 reflection in  -  +  0 sample. We get the shape of the reflection from Monte Carlo (left) and the number of reflection events from data (right).

16. Cincinnati, May 09- 2005 Kalanand Mishra K - K +  0 mass distribution (dots) and the result of the fit (blue line) with two Gaussians for the signal and an exponential term for the background (yellow color/ broken red line). No specific fit for the reflection peak in the plot on left. I take the yield from the fit on right. I am still trying to understand and include in fit the reflection peak in the upper side band. K - K +  0 yield

17. Cincinnati, May 09- 2005 Kalanand Mishra Left: K -  +  0 mass distribution (dots) and the result of the fit (blue line) with three Gaussians for the signal and a second order polynomial term for the background (yellow color). 282068 signals selected out of 4672000 generated. Efficiency ~ 6.0% Middle:  -  +  0 mass distribution (dots) and the result of the fit (blue line) with two Gaussians for the signal and an exponential term for the background (red broken line). 234435 signals selected out of 3466000 generated. Efficiency ~ 6.8% Right: K - K +  0 mass distribution (dots) and the result of the fit (blue line) with two Gaussians for the signal and an exponential term for the background (yellow color). 66235 signals selected out of 1362000 generated. Efficiency ~ 4.9% Efficiency Calculation

18. Cincinnati, May 09- 2005 Kalanand Mishra Dalitz plot for  -  +  0 (Monte Carlo)

19. Cincinnati, May 09- 2005 Kalanand Mishra I plan to: è Separate analysis in different momentum bins. è Separate analysis by charge (ie, D* + and D* - ) Systematic Studies èSystematic checks fall into two categories: è “sanity” checks èsystematic variations which include lack of knowledge/ understanding and biases in the fit model èFirst class demonstrates reasonableness of result èLatter class determines quantitative estimation of the systematic error Reasonableness Checks Systematic Errors  I have studied difference in yield due to different fits  I plan to calculate efficiency as function of position on Dalitz plot.  PID corrections for efficiencies.

20. Cincinnati, May 09- 2005 Kalanand Mishra BR(D 0       )/BR(D 0       ) = (6.51 ± 0.04) X 10 -2 BR(D 0  K - K +   )/BR(D 0       ) = (2.31 ± 0.03) X 10 -2 Very Preliminary Result è Investigate systematics associated with the analysis. Uniform efficiency across Dalitz plot is an approximation. I need to calculate efficiency as function of position on Dalitz plot and correctly account for contributions from other side of charm decay in Signal Monte Carlo when calculating the efficiencies. è Finish this analysis (new version of Babar Analysis Document 841) without delay.  Extension of present analysis to a full Dalitz plot analysis of Cabibbo-suppressed decays D 0  h - h +  0 to include these results in the study of B -  D (*)0 K - with the same D 0 decay as this analysis, which will be useful to constrain the third angle of unitarity triangle  è Final analysis with double the present data size ~ 450 fb -1 (which we hope to accumulate by summer 2006 ).

21. Cincinnati, May 09- 2005 Kalanand Mishra What is Next ? Dalitz analysis for CP phase  BB b u u u c s KK D0D0 BB b u c u s u D0D0 KK bubu bcbc   Final production amplitude

22. Cincinnati, May 09- 2005 Kalanand Mishra Backup slides

23. Cincinnati, May 09- 2005 Kalanand Mishra Service Work èAs our commitment towards smooth running of BaBar detector, we are required to undertake service works in the area of our expertise. èUniversity of Cincinnati group has always been very active in BaBar collaboration - providing leadership role in DIRC, Particle ID, and and Data Quality groups. èAt present I am BaBar DIRC operations manager (March - December, ‘05). I was earlier a DIRC commissioner ( December ‘04 - March ‘05). èI am one of the members of BaBar Particle ID team and very recently completed a major project for the group.

24. Cincinnati, May 09- 2005 Kalanand Mishra DIRC is Fine TM ! DIRC is Fine TM ! DRC-mon migrated to new version of EPICS Breaking News! Nicolas & Kalanand Nicolas & Kalanand

25. Cincinnati, May 09- 2005 Kalanand Mishra BaBar PID: Automated fast PID-table production (ROOT-based ) è New BaBar Particle ID tables successfully made entirely using ROOT - based procedure (major part of code written by me). èOne unified procedure to make PID tables, manage the PID-tables inventory, produce efficiency plots for each selector within a few hours for each run of a release. èThis major project has been characterized as “The Hall Of Fame - Successfully completed Project” by BaBar PID group on their web page: http://www.slac.stanford.edu/BFROOT/www/Physics/Tools/Pid/tasks.html

26. Cincinnati, May 09- 2005 Kalanand Mishra Fit Strategy We perform an extended maximum likelihood fit on the data to determine the number of signal and background events. From the selected events in the m D0 -  m window, determine signal and background levels in mass plots by fitting with the following distribution:  Fitted with three gaussians signal & a 2 nd order polynomial background  The mean’s and the σ 's of the three gaussians are allowed to be different

27. Cincinnati, May 09- 2005 Kalanand Mishra èCombinatoric èReal D 0, fake  s èFake / mis-constructed p0 èKpp0 reflection in ppp0 and KKp0 modes Background Sources Bottom line: Our analysis is dominated by systematics and NOT by Statistics

28. Cincinnati, May 09- 2005 Kalanand Mishra BaBar Detector èThe B A B A R detector is located at Stanford Linear Accelerator Center (SLAC) èTaking data since May 1999 èWe use 228.8 fb -1 of data taken till now for this analysis èPEPII is an asymmetric collider èElectron beam is 9.0 GeV (High Energy Ring), positron beam is 3.1 GeV (Low Energy Ring ) èMost data is taken at  (4S) resonance èWe use both on-resonance and off-resonance data

29. Cincinnati, May 09- 2005 Kalanand Mishra Detectors used in this analysis The Silicon Vertex Tracker (SVT) provides vertexing information and stand-alone tracking for low momentum particles. The Drift Chamber provides momentum information and dE/dx information to identify particles with transverse momentum < 0.7 GeV/c. The Particle Identification System (DIRC) uses Cerenkov Radiation to identify particles with transverse momentum > 0.7 GeV/c