1. 1 Warsaw Group May 2015 Search for CPV in three-bodies charm baryon decays Outline Selections Mass distributions and reconstructed numbers of candidates Kinematic distributions Binned S CP and unbinned kNN results in CF and sidebands of SCS decays

2. Decay modes 2 DecayTypeStatistics  + c → p K - K + SCSMagUp: 999.5/pb ; MagDown: 991.8/pb  + c → p K - K + SCSRunning on grid Up and Down  + c → p  -  + SCSMagUp: 999.5/pb ; MagDown: 991.8/pb  + c → p K -  + SCSMagUp: 988.22/pb ; MagDown: 990.1/pb  + c → p K -  + CFMagUp: 988.22/pb ; MagDown: 991.3/pb  + c → p K +  - DCSThere is a stripping line 2012 data blue – full available statistics Discussing today: sidebands in SCS:  + c → p K - K +,  + c → p  -  +,  + c → p K -  + CF:  + c → p K -  +

3. 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>0.99995 ; 2 4GeV; P T <16GeV Cuts been selected on the basis of LHCb-ANA-2014-026 (S.Blusk, Precision measurement of the mass and lifetime of the  0 b baryon) also thanks to Yury Shcheglov

4. IP  2 effect 4 Plots restricted to MagUp only SCS:  + c → pK -  + SCS:  + c → pK - K + CF:  + c → pK -  + SCS:  + c → p  -  + Comparison particles (open dots) and antiparticles (red full dots) Tail of  2 IP is very large Large difference (~ few %) between particles and antiparticles are in  + c → p  -  + decays for laaaarge values of  2 IP (pathological events) We choose events with  2 IP < 10 (taken from other analyses)

5. SCS:  + c → p  -  + 5 MagUp (999.5/pb)Down+Up (~2/fb)MagDown (991.8/pb) Double Gauss well describes data Fitted parameters of  1,  2 agree in Down and Up Total ~14.5k candidates of  + c → p  -  + in ~2/fb 2012

6. SCS:  + c → pK - K + 6 2012 Double Gauss well describes data Fitted parameters of  1,  2 agree in Down and Up Total ~2.5k candidates of  + c → pK -  + in ~2/fb (~6 times smaller than  + c → p  -  + ) MagUp (999.5/pb)Down+Up (~2/fb)MagDown (991.8/pb)

7. SCS:  + c → pK -  + 7 To do: check  + c from  0 b decays (ntuples for MagUp are done) 2012 MagUp (988.2/pb)Down+Up (~2/fb)MagDown (990.1/pb) To do Double Gauss well describes data Fitted parameters of  1,  2 agree in Down and Up Total ~2k candidates of  + c → pK -  + in ~2/fb

8. CF:  + c → pK -  + 8 Double Gauss well describes 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)

9. Pseudorapidity (MagDown+MagUp) 9 SCS:  + c → p  -  + SCS:  + c → pK -  + SCS:  + c → pK - K + CF:  + c → pK -  + The differences between decays are seen: differences in means of  differences in shapes

10. Pseudorapidity (MagDown+MagUp) 10 SCS:  + c → p  -  + SCS:  + c → pK -  + SCS:  + c → pK - K + CF:  + c → pK -  + Not to show for public There are no differences between particles and antiparticles larger than ±3 , only statistical fluctuations

11. Momenta (MagDow+MagUp) 11 SCS:  + c → p  -  + SCS:  + c → pK -  + SCS:  + c → pK - K + CF:  + c → pK -  + The differences between decays are seen: differences in means of p

12. Momenta (MagDow+MagUp) 12 SCS:  + c → p  -  + SCS:  + c → pK -  + SCS:  + c → pK - K + CF:  + c → pK -  + Not to show for public There are no differences between particles and antiparticles larger than ±3 , only statistical fluctuations

13. Transverse momenta (MagDown+MagUp) 13 SCS:  + c → p  -  + SCS:  + c → pK -  + SCS:  + c → pK - K + CF:  + c → pK -  + The differences between decays are seen: differences in means of p T shapes are different but the smallest differences are between two similar decays:  + c → p  -  + and  + c → pK - K + There is different kinematics seen in , p, p T between decays. It is caused by different contribution from prompt and secondary decays.

14. Transverse momenta (MagDown+MagUp) 14 SCS:  + c → p  -  + SCS:  + c → pK -  + SCS:  + c → pK - K + CF:  + c → pK -  + Not to show for public There are no differences between particles and antiparticles larger than ±3 , only statistical fluctuations

15. IP distributions (MagDown+MagUp) 15 All events SCS:  + c → p  -  + SCS:  + c → pK -  + SCS:  + c → pK - K + CF:  + c → pK -  + To do The differences in IP are seen between decays Small differences between similar decays (  + c → p  -  + and  + c → pK - K + ): mean of IP is slightly different Large differences between SCS decays and CF decay There are different contributions in channels from prompt and secondary decays ⇒ visible differences in , p, p T distributions

16. IP distributions (MagDown+MagUp) 16 CF:  + c → pK -  + All events Signal of CF events: ± 15 MeV around PDG mass Background events: M<PDG-20MeV or M>PDG+20MeV Differences between particles and antiparticles are seen in signal events In background events there is not asymmetry between particles and antiparticles This is an effect of production asymmetry (discussing in details later) particles (open dots) antiparticles (red full dots)

17. IP distributions (MagDown+MagUp) 17 SCS:  + c → p  -  + Not to show for public All events Signal of CF events: ± 15 MeV around PDG mass Background events: M<PDG-20MeV or M>PDG+20MeV particles (open dots) antiparticles (red full dots) There are no bins with differences larger than ±3 , but in signal events, there is systematic shift between particles and antiparticles which is not visible in background events (production asymmetry effect)

18. IP distributions (MagDown+MagUp) 18 SCS:  + c → pK - K + Not to show for public All events Signal of CF events: ± 15 MeV around PDG mass Background events: M<PDG-20MeV or M>PDG+20MeV particles (open dots) antiparticles (red full dots) No significant differences between signal and background events No asymmetry between particles and antiparticles (no production asymmetry effect) as in cinematically identical  + c → p  -  +  + c → pK - K + decays are ~6 times less than  + c → p  -  +

19. Methods for searches for CPV 19 Binned method In each bin we calculate a significance of a difference between D + and D - 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

20. Methods for searches for CPV 20 Unbinned k-nearest neighbour method (kNN) To compare D + and D - 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 (D + —D +, D - —D - ) I(i,k) = 0 if pair has opposite charge (D + —D  ) 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 D-D- D+D+ query event n k =10 PLB 728 (2014) 585

21. Methods for searches for CPV 21 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

22. CF:  + c → pK -  + 22 Down+Up: Dalitz plots Signal of CF events: ± 15 MeV around PDG mass Background events: M PDG+20MeV K*

23. CF:  + c → pK -  + 23 Down+Up: the binned S CP method results Signal of CF events: ± 15 MeV around PDG mass Background events: M PDG+20MeV Binned method does not see asymmetry in signal and background of CF decays But raw asymmetry in signal of CF decays is different from zero (production asymmetry is expected here) N bins = 169 p-value = 0.086 A RAW = -0.0080 ± 0.0015 (5.3  ) N bins = 211 p-value = 0.55 A RAW = -0.0100 ± 0.0034 (2.9  )

24. CF:  + c → pK -  + 24 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  But shift in one direction is visible (i.e. production asymmetry is expected in the signal of CF decays)

25. CF:  + c → pK -  + 25 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

26. CF:  + c → pK -  + 26 Down+Up: the unbinned kNN method results Signal of CF events: ± 15 MeV around PDG mass normalization shape R2 = R3+R4 A RAW = -0.0080 ± 0.0015 (5.3  ) Since raw asymmetry is the same within errors in all regions – it is production asymmetry The kNN method sees an asymmetry (the S CP does not see)

27. CF:  + c → pK -  + 27 Down+Up: the unbinned kNN method results: MagDown vs MagUp MagUp normalization shape MagDown normalization shape A RAW = -0.0118 ± 0.0021 (5.6  ) A RAW = -0.0041 ± 0.0021 (2  ) Non zero raw asymmetry in MagDown is seen by the kNN method If there is no raw asymmetry in MagUp, the kNN does not generate asymmetry

28. SCS  + c → p  -  + 28 Down+Up: Dalitz plots Signal of CF events: ± 15 MeV around PDG mass Background events: M PDG+20MeV

29. Background of SCS  + c → p  -  + 29 Down+Up: the binned S CP method results Background events: M PDG+20MeV N bins = 225 p-value = 0.20 A RAW = -0.0008 ± 0.0056 The unbinned kNN method results normalizationshape #Events ## p-value ## Down+Up31 3890.120.452.60.0045 Down15 8431.40.0780.540.29 Up15 5461.30.100.410.34 No asymmetry is seen using SCP and kNN methods (No production asymmetry)

30. Background of SCS  + c → p  -  + 30 Down+Up Background events: M PDG+20MeV No differences between particles and antiparticles in background events

31. SCS  + c → p  -  + 31 Not to show for public Down+Up: the binned S CP method results N bins = 190 p-value = 0.024 A RAW = -0.0364 ± 0.0071 Signal of CF events: ± 15 MeV around PDG mass

32. SCS  + c → p  -  + 32 Not to show for public Down+Up Signal of CF events: n± 15 MeV around PDG mass Differences between particles and antiparticles varies within ±3  But shift in one direction is visible (i.e. production asymmetry is expected)

33. SCS  + c → pK - K + 33 Down+Up: Dalitz plots Signal of CF events: ± 15 MeV around PDG mass Background events: M PDG+20MeV  

34. Background of SCS  + c → pK - K + 34 Down+Up: the binned S CP method results Background events: M PDG+20MeV N bins = 78 p-value = 0.92 A RAW = -0.007 ± 0.013 The unbinned kNN method results normalizationshape #Events ## p-value ## Down+Up5 9830.450.320.930.18 Down2 9391.50.0680.520.30 Up3 0440.830.20-1.10.86 No asymmetry is seen using SCP and kNN methods (No production asymmetry)

35. Background of SCS  + c → pK - K + 35 Down+Up Background events: M PDG+20MeV No differences between particles and antiparticles in background events

36. SCS  + c → pK - K + 36 Not to show for public Down+Up: the binned S CP method results N bins = 43 p-value = 0.57 A RAW = -0.006 ± 0.016 Signal of CF events: ± 15 MeV around PDG mass

37. SCS  + c → pK - K + 37 Not to show for public Down+Up Signal of CF events: n± 15 MeV around PDG mass Differences between particles and antiparticles varies within ±3 

38. Background of SCS  + c → pK -  + 38 Background events: M PDG+20MeV The unbinned kNN method results normalizationshape #Events ## p-value ## Down+Up Down6 1440.370.35-0.780.78 Up5 8440.600.27-0.210.58 No asymmetry is seen using kNN method

39. Summary 39 In signal of CF  + c → pK -  + decays the kNN method sees expected production asymmetry (the S CP method does not see it); A RAW = -0.0080 ± 0.0015 (5.3  ) In background of of CF  + c → pK -  + decays both methods do not see the asymmetry; A RAW = -0.0100 ± 0.0034 (2.9  ) In the sidebands of SCS decays the methods do not see the asymmetries Next step: Check the method sensitivities in MC decays with and without CP asymmetry to check the power of the methods