Cincinnati, May 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

Cincinnati, May 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 August 2004).

Cincinnati, May 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.

Cincinnati, May Kalanand Mishra B-Factory at SLAC PEP-II accelerator schematic and tunnel view 9 GeV e 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

Cincinnati, May 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)

Cincinnati, May 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

Cincinnati, May 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 > GeV  GeV/c 2 < M  < GeV/c 2

Cincinnati, May 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

Cincinnati, May 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 D | < GeV/c 2 è D* + vertex  2 < 20.0 è Unconverged fits are rejected

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

Cincinnati, May Kalanand Mishra Multiple Candidates èWe observed multiple D 0  h - h +  0 candidates per event with multiplicity ~ % (ie, average 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.

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

Cincinnati, May 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).

Cincinnati, May 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

Cincinnati, May 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).

Cincinnati, May 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

Cincinnati, May 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) signals selected out of 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) signals selected out of 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) signals selected out of generated. Efficiency ~ 4.9% Efficiency Calculation

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

Cincinnati, May 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.

Cincinnati, May Kalanand Mishra BR(D 0       )/BR(D 0       ) = (6.51 ± 0.04) X BR(D 0  K - K +   )/BR(D 0       ) = (2.31 ± 0.03) X 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 ).

Cincinnati, May 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

Cincinnati, May Kalanand Mishra Backup slides

Cincinnati, May 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.

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

Cincinnati, May 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:

Cincinnati, May 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

Cincinnati, May 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

Cincinnati, May 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 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

Cincinnati, May 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