Kalanand Mishra February 23, Branching Ratio Measurements of Decays D 0  π - π + π 0, D 0  K - K + π 0 Relative to D 0  K - π + π 0 decay Giampiero Mancinelli, Brian T. Meadows, Kalanand Mishra, Michael D. Sokoloff University of Cincinnati We present measurements of the relative branching ratios from a sample of 232 fb -1 data. We find that B(D 0  π - π + π 0 )/ B(D 0  K - π + π 0 ) = (1.073   syst)  and B(D 0  K - K + π 0 )/ B(D 0  K - π + π 0 ) = (2.39   syst)  These can be compared to PDG 2004 current world average B(D 0  π - π + π 0 )/ B(D 0  K - π + π 0 ) = (8.40  3.11)  and B(D 0  K - K + π 0 )/ B(D 0  K - π + π 0 ) = (0.95  0.26) 

Kalanand Mishra February 23, Track Selection è Kaon & pion tracks  GoodTracksLoose, ≥ 20 DCH hits  ≥ 2 SVT r-phi (z) hits with at least 1 hit on inner 3 r-phi (z) layers  ≥ 6 total SVT hits è  0 Reconstruction   Candidates with  Single calorimeter bumps not matched with any track  Energy > 100 MeV   0 Energy > GeV  GeV/c 2 < M  < GeV/c 2 We search for decays of type D* +  D 0  s + D 0  -  +  0, D 0  K - K +  0, D 0  K -  +  0  0   Integrated Luminosity ~ 232 fb -1 (ON + OFF Resonance) For Bkgd studies and cut optimization: ccbar Continuum ~ 138 fb -1 For detection efficiency: Signal MC with uniform phase space: ~ 1.4 million K - K +  0 ~ 4.5 million  -  +  0 ~ 4.5 million K -  +  0 Data Sample è PID : LH Tight for both π and K

Kalanand Mishra February 23,  h - and h + tracks are fit to a vertex  Mass of  0 candidate is constrained to m  0 at h - h + vertex  1.70 < m( h - h +  0 ) < 2.0 GeV/c 2  P CM ( D 0 ) > 2.77 GeV/c D* Reconstruction  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.  |m D* - m D | < 0.6 MeV/c 2  vertex  2 < 20.0  Chose a single best candidate with smallest vtx  2 for the whole decay chain.  Charged track combinatoric, mis- constructed  0  Real D 0, fake  s  K  0 reflection in  0 and KK  0 modes D 0  h - h +  0 Reconstruction Background Sources

Kalanand Mishra February 23, π - π + π 0 in generic MC Zoomed in GeV/c 2 Events/ (1.25 MeV/c 2 ) Events/ (2.5 MeV/c 2 )

Kalanand Mishra February 23, K - K + π 0 in generic MC Zoomed in GeV/c 2 Events/ (5 MeV/c 2 ) Events/ (2.5 MeV/c 2 )

Kalanand Mishra February 23, K -  +  0 reflection in  -  +  0 (top) and K - K +  0 (bottom) samples. I get the shape of the reflection from Monte Carlo (left) and the number of reflection events from data (right). π-π+π0 π-π+π0 Reflection Study (using truth-matching) Monte Carlo: Shape data: number Monte Carlo: Shape data: number K-K+π0 K-K+π0

Kalanand Mishra February 23, Signal fit with sum of 3 Gaussians Linear background K -  +  0 signal yield from data Log Scale

Kalanand Mishra February 23, Signal fit with sum of 3 Gaussians Linear background K -  +  0 reflection peak in the sideband  -  +  0 and K - K +  0 signal yields from data

Kalanand Mishra February 23, Efficiency: K -  +  0 observed fit pull m 2 (K - π 0 ) m 2 (π + π 0 ) m 2 (K - π + )

Kalanand Mishra February 23, Efficiency:  -  +  0 observed fit pull m 2 (π - π 0 ) m 2 (π + π 0 ) m 2 (π - π + )

Kalanand Mishra February 23, Efficiency: K - K +  0 observed fit pull m 2 (K - π 0 ) m 2 (K + π 0 ) m 2 (K - K + )

Kalanand Mishra February 23, Since the reconstruction efficiency is not uniform across phase space, each event is weighted according to its efficiency ( weight = 1/ efficiency ). Efficiency for each mode is calculated using signal Monte Carlo events generated uniformly across Dalitz plot. Parameterize efficiency by a 3 rd order polynomial : E( x, y ) = c 0 + c 1.x + c 2.y + c 3.x 2 + c 4.y 2 + c 5.x.y + c 6.x 3 + c 7.y 3 + c 8.x 2.y + c 9.x.y 2 where x = m 2 (h -  0 ), y = m 2 (h +  0 ) Efficiency function includes PID correction ( i.e., product of  data /  MC of the two charged tracks in each event ). Since in some parts of phase space fitted and observed efficiencies differ slightly ( though they are close), we decided to obtain ratio of BRs using each of them separately and quote the result obtained with observed efficiency. Efficiency Calculation

Kalanand Mishra February 23, Compares well ! Data-MC sideband background comparison for π - π + π 0 data MC 2D pull pull Sideband 1.93 < m π - π + π 0 < 1.99 GeV/c 2

Kalanand Mishra February 23, MC signal-sideband background comparison for π - π + π 0 signal sideband 2D pull pull Sideband 1.93 < m π - π + π 0 < 1.99 GeV/c 2 Compares well !

Kalanand Mishra February 23, Compares well ! Data-MC sideband background comparison for K - K + π 0 Sideband 1.75 < m K - K + π 0 < 1.80 GeV/c 2 data MC 2D pull pull

Kalanand Mishra February 23, MC signal-sideband background comparison for K - K + π 0 Sideband 1.75 < m K - K + π 0 < 1.80 GeV/c 2 signalsideband 2D pull pull Compares well !

Kalanand Mishra February 23, Efficiency-corrected Dalitz plot: K -  +  0 Log Scale Linear Scale m 2 (K - π 0 ) m 2 (π + π 0 ) m 2 (K - π + ) ~ 0.5 % bkg

Kalanand Mishra February 23, Efficiency-corrected Dalitz plot:  -  +  0 Log Scale Linear Scale m 2 (π - π 0 ) m 2 (π + π 0 ) m 2 (π - π + ) ~ 2 % bkg

Kalanand Mishra February 23, Efficiency-corrected Dalitz plot: K - K +  0 Log Scale Linear Scale m 2 (K - π 0 ) m 2 (K + π 0 ) m 2 (K - K + ) ~ 5 % bkg

Kalanand Mishra February 23, The average weight of reconstructed signal events in signal region is obtained after doing a background subtraction from sideband. The number of observed signal events was obtained directly from the mass histogram fits for each mode. The total number of signal events produced in the experiment is the product of average signal reconstruction weight and number of observed signal events for each mode. The ratio of branching ratios is obtained as the ratio of number of events produced for respective modes in the experiment. The statistical and systematic errors associated with the measurement are determined. Calculation of ratio of BRs

Kalanand Mishra February 23, èSystematic checks fall into two categories: è “sanity” checks èsystematic variations which include lack of understanding and biases in the fit model èFirst class demonstrates reasonableness of result èLatter class determines quantitative estimation of the systematic error Reasonableness Checks Separate analysis in different momentum ranges. Separate analysis by charge ( i.e., separately for D* + and D* - ). Systematic Errors The two obvious sources of systematic error are: systematic error in efficiency calculation error from Monte Carlo statistics Other sources systematic errors : error from estimation of background events in signal region PID systematics To gain confidence with error calculation and overall analysis, we calculated our results using bin by bin efficiency as well ( in addition to the one with parameterized efficiency ). Study of Systematics Yet to be estimated

Kalanand Mishra February 23, Consistency check with MC As an additional sanity check, we applied this analysis procedure to obtain ratio of BRs for SP6 generic ccbar events ( where we ‘know’ the correct ratios ). The two results agree within errors. D 0 decay modeGenerated B(π  π  π 0 )/B(K    π 0 ) B(K    π 0 )/B(K    π 0 ) My ResultsMy Results - D   (fit)   (fit)   (fit)   (fit) My Results - D 0 bar   (fit)   (fit)  The systematic errors quoted here are only due to efficiency calculation.  The results are also consistent in measurements of disjoint samples ( 5 different lab momentum bins ).

Kalanand Mishra February 23, Consistency check in data We repeated exactly the same analysis procedure to obtain ratio of BRs for D 0 and D 0 bar events separately and in five different lab momentum bins. All results are consistent within errors. D 0 decay mode B(π  π  π 0 )/B(K    π 0 ) B(K    π 0 )/B(K    π 0 ) Full Data Sample D 0 only   (fit)   (fit)   (fit)   (fit) D 0 bar only   (fit)   (fit) The systematic errors quoted here are only due to efficiency calculation. We expect final systematic error to be slightly higher.

Kalanand Mishra February 23, Consistency check in data: disjoint samples Result for π - π + π 0 relative BR in five different lab momentum ranges.

Kalanand Mishra February 23, èFinish this analysis and accompanying BAD.  Focus on the Dalitz plot analysis of the decay mode D 0  -  +  0 to include these results in the study of B -  D 0 K - with D 0  -  +  0, for  analysis ( already under progress, see Jinlong Zhang’s talk given in Breco-2 parallel session ). D 0 decay modeOur Current Results(%) B(π  π  π 0 )/B(K    π 0 )10.73  0.06  0.08 B(K    π 0 )/B(K    π 0 )2.39  0.03  0.06 Sunil’s Results(%) PDG Results(%) 9.78  0.08    0.04   0.26 The present results are preliminary. Preliminary Results and Plans