1 Marek Szczekowski, Artur Ukleja Warsaw Group 3 June 2015 Model-independent search for CPV in three-bodies charm baryon decays Outline Selections for SCS  + c → p K - K +, SCS  + c → p  -  +, SCS  + c → p K -  +, CF  + c → p K -  + Mass distributions and reconstructed numbers of candidates Results of the binned S CP and the unbinned kNN methods in CF and sidebands of SCS decays Comparison of MagDown and MagUp Summary and future plans

Decay modes 2 DecayTypeStatistics  + c → p K - K + SCSMagUp: 999.5/pb ; MagDown: 991.8/pb  + c → p K - K + SCSplanning  + c → p  -  + SCSMagUp: 999.5/pb ; MagDown: 991.8/pb  + c → p K -  + SCSMagUp: /pb ; MagDown: 990.1/pb  + c → p K -  + CFMagUp: /pb ; MagDown: 991.3/pb  + c → p K +  - DCSplanning 2012 data blue – full available statistics Discussing today: sidebands in SCS:  + c → p K - K +,  + c → p  -  +,  + c → p K -  + CF:  + c → p K -  +

Selection criteria 3 We reconstruct decays of: Charm baryon → p h h ( h = K or  ) Implemented cuts: p: PIDp>10 ; ProbNNp>0.5 ; IP  2 >9 ; Track_GhostProb<0.4 P>10GeV ; P<100GeV  : PIDK 0.1 ; IP  2 >9 ; Track_GhostProb<0.4 P>3GeV ; P<150GeV K: PIDK>-10 ; ProbNNk>0.1 ; IP  2 >9 ; Track_GhostProb<0.4 P>3GeV ; P<150GeV  c,  c :  >0.5ps ;  <1.5ps ; IP  2 <10 ;  2 (Separation from related PV)>20 ; Vtx  2 /ndof<8 ; DIRA> ; 2 4GeV; P T <16GeV Cuts have been selected on the basis of LHCb-ANA (S.Blusk, Precision measurement of the mass and lifetime of the  0 b baryon) also thanks to Yury Shcheglov

SCS:  + c → p  -  + 4 MagUp (999.5/pb)Down+Up (~2/fb)MagDown (991.8/pb) Double Gauss describes well the data Fitted parameters of  1,  2 agree in Down and Up Total ~14.5k candidates of  + c → p  -  + in ~2/fb We define:  Signal of SCS events: ± 15 MeV around PDG mass  Background events: M PDG + 20 MeV 2012 S/B ~ 5

SCS:  + c → pK - K Double Gauss describes well the data Fitted parameters of  1,  2 agree in Down and Up Total ~2.5k candidates of  + c → pK - K + (~6 times smaller than  + c → p  -  + ) We define:  Signal of SCS events: ± 15 MeV around PDG mass  Background events: M PDG + 20 MeV MagUp (999.5/pb)Down+Up (~2/fb)MagDown (991.8/pb) S/B ~ 7

SCS:  + c → pK -  MagUp (988.2/pb)Down+Up (~2/fb)MagDown (990.1/pb) Double Gauss describes well the data Fitted parameters of  1,  2 agree in Down and Up Total ~2k candidates of  + c → pK -  + in ~2/fb To do: check  + c from  0 b decays to improve S/B We define:  Signal of SCS events: ± 15 MeV around PDG mass  Background events: M PDG + 20 MeV S/B ~ 2

CF:  + c → pK -  + 7 Double Gauss describes well the data, background is very small Fitted parameters of  1,  2 agree in Down and Up  1 ~ 5 MeV consistent in all analysed decays Total ~440k candidates of  + c → pK -  + in ~2/fb We define:  Signal of CF events: ± 15 MeV around PDG mass  Background events: M PDG + 20 MeV 2012 MagUp (988.2/pb)Down+Up (~2/fb)MagDown (991.3/pb) S/B ~ 70

Methods for searches for CPV 8 Binned method In each bin we calculate a significance of a difference between particles and antiparticles To cancel global asymmetries (production asymmetry, etc.) we normalize Dalitz plots If no CPV (only statistical fluctuations) then S CP is Gauss distributed (  =0,  =1) We calculate  2 =  S i CP 2 to obtain p-value for the null hypothesis to test if D + and D - distributions are statistically compatible p-value ≪ 1 in case of CPV PLB 728 (2014) 585 if asymmetry Monte Carlo Bediaga et al. Phys.Rev.D80(2009)096006

Methods for searches for CPV 9 Unbinned k-nearest neighbour method (kNN) To compare “+ ” and “-” we define a test statistic T which is based on the counting particles with the same sign to each event for a given number of the nearest neighbour events I(i,k) = 1 if i th event and its k th nearest neighbor have the same charge (“+ ” —”+ ”, “- ” —”- ” ) I(i,k) = 0 if pair has opposite charge (“+ ” —”  ” ) T is the mean fraction of like pairs in the pooled sample of the two datasets We calculate p-value for case of no CPV by comparing T with expected mean  T and variance  T x y “- ” “+ ” query event n k =10 PLB 728 (2014) 585

Methods for searches for CPV 10 The kNN method allows to find differences between two samples if they come from: normalization, if n + ≠ n - then  T ≠  TR shape, if f + ≠ f - then T ≠  T we calculate the two p-values CP asymmetry can be manifested by different normalization and shape For shape the p-value is the area under the expected curve from measured T to 1. in case of CPV, p-value ≪ 1 Expected distribution generated using Eqs.  T,  T Measured T p-value

CF:  + c → pK -  + 11 Down+Up: Dalitz plots Signal of CF events: ± 15 MeV around PDG mass Background events: M PDG+20MeV K*  ++  1520

CF:  + c → pK -  + 12 Down+Up: the binned S CP method results Signal of CF events: ± 15 MeV around PDG mass Background events: M PDG+20MeV The raw asymmetry is not observed with the S CP method (with 169 bins) in signal and background of CF decays, but raw asymmetry in signal of CF decays is different from zero (consistent with small production asymmetry) N bins = 169 p-value = A RAW = ± (5.3  ) N bins = 211 p-value = 0.55 A RAW = ± (2.9  ) Global asymmetries are not cancelled (no  )

CF:  + c → pK -  + 13 Down+UpSignal of CF events: ± 15 MeV around PDG mass particles (open dots) antiparticles (red full dots) Differences between particles and antiparticles varies within ±3  Small shift in one direction is observed (i.e. small production asymmetry is expected in the signal of CF decays)

CF:  + c → pK -  + 14 Down+Up: the unbinned kNN method results Signal of CF events: ± 15 MeV around PDG mass To increase the sensitivity of the method we choose regions defined around resonances There are six regions: R1 = X<0.7 R2 = X>=0.7 and X<0.9 R3 = X>=0.7 and X<0.9 and Y<3.2 R4 = X>=0.7 and X =3.2 R5 = X>=0.9 and Y>=2.8 R6 = X>=0.9 and Y<2.8 Some regions are overlaped: R2 = R3 + R4 X = Y = R1 R2 R3 R4 R6 R5

CF:  + c → pK -  + 15 Down+Up: the unbinned kNN method results Signal of CF events: ± 15 MeV around PDG mass normalization shape R2 = R3+R4 A RAW = ± (5.3  ) Raw asymmetry is the same within errors in all regions – it is consistent with production asym. The asymmetry is observed with the kNN method

CF:  + c → pK -  + 16 Down+Up: the unbinned kNN method results: MagDown vs MagUp MagUp normalization shape MagDown normalization shape A RAW = ± (5.6  ) A RAW = ± (2  ) Difference between MagDown and MagUp:  A RAW = ± (2.6  ) With the present errors the measured raw asymmetries are consistent in MagDown and MagUp

SCS  + c → p  -  + 17 Down+Up: Dalitz plots Signal of CF events: ± 15 MeV around PDG mass Background events: M PDG+20MeV  770 f 0 (980)  770

Background of SCS  + c → p  -  + 18 Down+Up: the binned S CP method results Background events: M PDG+20MeV N bins = 225 p-value = 0.20 A RAW = ± The unbinned kNN method results normalizationshape #Events ## p-value ## Down+Up Down Up No asymmetry is observed with the S CP and kNN methods No production asymmetry is observed Global asymmetries are not cancelled (no  )

SCS  + c → pK - K + 19 Down+Up: Dalitz plots Signal of CF events: ± 15 MeV around PDG mass Background events: M PDG+20MeV  

Background of SCS  + c → pK - K + 20 Down+Up: the binned S CP method results Background events: M PDG+20MeV N bins = 78 p-value = 0.92 A RAW = ± The unbinned kNN method results normalizationshape #Events ## p-value ## Down+Up Down Up No asymmetry is observed with the S CP and kNN methods No production asymmetry is observed Global asymmetries are not cancelled (no  )

SCS  + c → pK -  + 21 Down+Up: Dalitz plots Signal of CF events: ± 15 MeV around PDG mass Background events: M PDG+20MeV K* K* 0 (1430)

Background of SCS  + c → pK -  + 22 Background events: M PDG+20MeV The unbinned kNN method results normalizationshape #Events ## p-value ## Down+Up Down Up No asymmetry is observed with the S CP and the kNN methods N bins = 110 p-value = 0.99 A RAW = ± No production asymmetry is observed Global asymmetries are not cancelled (no  )

Summary 23 In the signal of CF  + c → pK -  + decays non zero raw asymmetry is measured A RAW = ± (5.3  )  It is consistent with the small production asymmetry In the background of CF  + c → pK -  + decays no raw asymmetry is measured A RAW = ± (2.9  )  No asymmetry is observed with the both S CP and kNN methods. In the sidebands of SCS decays no asymmetries are observed with the S CP and the kNN methods Next plans: Extend to  + c → p K - K + and  + c → p K +  - Extend to 2011 data (+1/fb)