Studies of CGEMboss665b performance with physics channels

Transcription

1 Studies of CGEMboss665b performance with physics channels Cui Li, Cristina Morales, Andreas Pitka, Martin Ripka, Peter Weidenkaff for the CGEM software group /31

2 2.396 and 2.9 GeV All these channels are reconstructed and analyzed using boss665p01 with full MDC and CGEMBoss665b (CGEM+MDC). 2/311

3 Reconstruction of ee ppbar between Ecm 1.95 and 2.64 GeV with boss665p01 and Cgemboss665b Cristina Morales (Helmholtz-Institut Mainz) Selection criteria and efficiencies after selection Comparison of variables Momentum and invariant mass resolutions Tracking efficiencies Summary 2

4 Selection criteria Selection criteria optimized for analysis of ee--> ppbar from 2015 scan data: Two good charged tracks of opposite charge: Rxy, Rz and good Kalman tracks required Vertex fit to improve resolution of the track's momenta If tracks leave a TOF signal then the difference between them < 4ns. For Ecm >2.3 both should leave a signal in TOF cut limits addapted to the ECMS Back to back signature between tracks after boost to CMS: 160,160, 170, 175 at Ecm = 1.95, 1.975, 2.0, 2.38 and 2.64 GeV Momentum window cut: pexpected -4σmeasured < pp,pbar < pexpected + 3σmeasured sigma=0.0036,0.004,0.0046,0.008,0.009 for Ecm = 1.95, 1.975, 2.0, 2.38 and 2.64 GeV pexpected is obtained from momentum conservation Particle identification using - dedx in MDC: normph > (7,4,3) for Ecm = (1.95,1.975, 2.0) GeV - pid probabilities for Ecm= 2.38, 2.64 GeV: prob(p,pbar) > prob(pi, e, k) with TOF and dedx info and E/p_proton < 0.5 Cristina Morales, /11 3

5 Sel. efficiencies at Ecm = 2.0 and Ecm= 2.64 GeV Data samples of 50K generated with Phokhara v9.1 and NLO ISR and reconstructed under Boss665p01 and Cgemboss665b. Shown are thenumber of events after each cut and the total selection eff: Ecm = 2.0 GeV 2 good tracks Chi2vtx Angle between tracks TOF dedx Boss Cgemboss Ecm= good GeV tracks Chi2vtx Angle between tracks TOF Boss Cgemboss dedx PID Moment TOTAL um selection window eficiency PID Moment TOTAL um selection window eficiency The full DCH is used in Boss665p01 and CGEM+outer DCH used in Cgemboss. Kalman tracks are used for tracking reconstruction. Selection efficiencies very similar in boss and cgemboss Cristina Morales, /11 4

6 Sel. efficiencies at Ecm = 2.0 and Ecm= 2.64 GeV Selection efficiencies vs the polar angle of the proton at cms: Efficiency at Ecm =2.0 GeV Boss665p01 Cgemboss665b costheta_p Efficiency at Ecm =2.64 GeV Boss665p01 Cgemboss665b costheta_p Selection efficiencies very similar: At Ecm = 2.0 GeV efficiency with cgemboss slightly lower At Ecm = 2.64 GeV Cgemboss is clearly lower at large and small polar angles Cristina Morales, /11 5

7 POAxy of the Ecm =2.0,2.64 GeV: The data samples have beed reconstructed using kalman or recmdc tracks in Cgemboss and using inner + outer DCH or only outer DCH in boss665p01. Only two tracks with opposite charge required: Ecm = 2.0 GeV Boss (kalman tracks) Boss (outer MDC + kalman) Cgemboss (kalman tracks) Cgemboss (recmdctracks) POAxy_aproton (cm) Ecm = 2.64 GeV POAxy_proton (cm) CGEMBoss resolution is similar to BOSS' when Kalman tracks used CGEMBoss: Mean is a bit shifted and charge dependent. Also for BOSS with only outer MDC At GeV, only CGEMBoss using recmdc tracks shifted Positive//negative kalman tracks have similar resolutions POAxy_proton (cm) Cristina Morales, POAxy_aproton (cm) 6

8 POAz of the Ecm =2,0,2.64 GeV: Only two tracks with opposite charge required: Ecm = 2.0 GeV Boss (kalman tracks) Boss (outer MDC + kalman) Cgemboss (kalman tracks) Cgemboss (recmdctracks) POAz_proton (cm) CGEMBoss resolution is comparable with BOSS' POAz_aproton (cm) BOSS with only outer MDC worse resolution Ecm = 2.64 GeV CGEMBoss: Resolution is the same using kalman tracks or recmdc tracks Positive//negative kalman tracks have similar resolutions POAz_proton (cm) Cristina Morales, POAz_aproton (cm) 5/11 7

9 De/dx of the Ecm =2.0, 2.64 GeV Boss (kalman tracks) Boss (outer MDC + kalman) Cgemboss (kalman tracks) Cgemboss (recmdctracks) Cgemboss response shifted to the left. Boss gives similar results for dedx with or without inner DCH nomph_proton normph_aproton nomph_proton normph_aproton At GeV boss and Cgemboss Agree very well Ecm = 2.64 GeV Ecm = 2.0 GeV Only two tracks with opposite charge required (shift remains also after all other cuts): Cristina Morales, /11 8

10 Pt and Pz of the Ecm= 2.0, 2.64 GeV Boss (kalman tracks) Boss (outer MDC + kalman) Cgemboss (kalman tracks) Cgemboss (recmdctracks) Similar distributions for boss and CGEMBoss pt_proton (GeV/c) pz_proton (GeV/c) pt_proton (GeV/c) pz_proton (GeV/c) Ecm = 2.64 GeV Ecm = 2.0 GeV After vertex fit: Cristina Morales, Similar distributions for positive and negative tracks 7/11 9

11 Momentum and Invariant mass resolution Resolutions after all selection cuts: Proton Boss665p01 Pbar Boss665p01 Proton Cgemboss Pbar Cgemboss Invariant mass resolution Resolution (MeV) Resolution (MeV/c) Momentum resolution Boss665p01 Cgemboss665b p (GeV/c) E_cm (GeV) At low momenta CGEMBoss provides better momentum and inv mass resolutions Similar momentum resolutions for particle and antiparticle Cristina Morales, /11 10

12 Proton and aproton tracking efficiencies Since only one track can be identified, a new, harder signal selection is needed: Ask for 1 or 2 good tracks. For the proton eff we need to have at least an antiproton. The track has to fulfill: POAxy < 0.1 cm and POAz < 1; Prob(pbar)> Prob(mu, K, pi) Prob(pbar) > 10 Prob(e-) costheta_pbar <0.8 tracking efficiency Proton efficiencies higher than antiproton efficiencies Proton Boss665p01 Proton Cgemboss Pbar Boss665p01 Pbar Cgemboss Efficiencies decrease for lower track momenta At larger momenta tracking efficiencies very similar or larger for Cgemboss than Boss At lower momenta Cgemboss has lower tracking efficiencies P (GeV/c) P (GeV/c) Cristina Morales, /11 11

13 Proton tracking efficiencies vs theta_p tracking efficiency 2.38 GeV Boss665p GeV Cgemboss 2.0 GeV Boss665p GeV Cgemboss 1.95 GeV Boss665p GeV Cgemboss The effiicency is quite flat but seems to gets lower at large or small polar angles (need more statistics at low Ecm) costheta_p Cristina Morales, /11 12

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15 in the future (with full MDC) and Cgemboss665b (with CGEM and MDC) true and recons. tracks Kalman tracks are used for the track reconstruction 14

16 + MDC boss665p01 CGEMBoss665b Boss665p01: CGEMBoss665b: Boss665p01 and CGEMBoss665b CGEMBoss665b shows a bit larger shift 15

17 CGEMBoss665b boss665p01 mu+,mu- CGEMBoss665b boss665p01 mu+,mu- CGEMBoss665b: tracking efficiency is higher, except for small momenta CGEMBoss665b: tracking efficiency is higher, except at large/small polar angles 16

18 CGEMBoss665b boss665p01 boss665p01 CGEMBoss665b mu+,mu- mu+,mu- Good agreement between Boss665p01 and CGEMBoss665b for p < 1.7 GeV Disagreement at larger pt (investigations ongoing) 17

19 boss665p01 CGEM Boss665b Good agreement between Boss665p01 and CGEMBoss665b, a bit lower efficiency for CGEMBoss (plot Mmumu and Pt correlation) 18

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24 Boss665p01 CGEMBoss MC true 23

25 Boss665p01 CGEMBoss MC true large CGEMBoss 24

26 Boss665p01 CGEMBoss CGEMBoss and Boss for soft pions Boss in 25

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28 Boss CGEMBoss Fit Boss CGEMBoss Boss CGEMBoss in z-direction 27

29 Boss CGEMBoss Boss CGEMBoss Boss CGEMBoss Boss 28

30 Boss CGEMBoss 29

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33 Boss CGEMBoss Boss CGEMBoss 32

34 Boss CGEMBoss CCGEMBoss 33

35 Boss CGEMBoss 34

36 Boss CGEMBoss 35

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39 This selection makes big use of the track's momenta 38

40 More events lost after each cut in CGEMBoss 39

41 Main difference in the first cut 40

42 Low momenta lost in CGEMBoss 41

43 for GeV More tracks with large and low polar angle lost in CGEMBoss 42

44 for GeV Charge-dependent shift observed in Rxy using CGEMBoss Perhaps also small shift in Rz using CGEMBoss for the pions 43

45 for GeV Inv. Mass distributions and resolutions comparable More tracks with low momenta at CGEMBoss compared to Boss (need to check in MC truth what the expected behavior is) 44

46 for GeV Decay length from CGEMBoss slightly shifted to lower values 45

47 Low momenta lost in CGEMBoss 46

48 for 2.9 GeV More tracks with large and low polar angle lost in CGEMBoss 47

49 for 2.9 GeV Charge-dependent shift in Rxy observed in CGEMBoss reduced in comparison to Ecm = 2.39 GeV 48

50 for 2.9 GeV Inv. Mass distributions and resolutions comparable Shift to low momenta at CGEMBoss compared to Boss ( Need to compare momentum distributions wrt MC truth ) 49

51 for 2.9 GeV Decay length from CGEMBoss slightly shifted to lower values 50

52 Final remarks Excellent work has been done in the CGEM software There is quite good agreement between CGEMBoss and Boss There is room for improvement for tracks with low momentum but this is ongoing work and this was just the first CGEMBoss version!! Thank you! 51

53 Spares 59

54 Summary e+e- ppbar Similar selection efficiencies for Cgemboss665b and boss665p01. At low Ecm 2% lower using Cgemboss At intermediate to high Ecm (high p), CGEMBoss and Boss agree very well At low Ecm: POAxy shows a shift in the mean position using CGEMBoss, the shift is charge dependent POAz agrees very well for both CGEMBoss and Boss There is a not negligible shift in dedx Momentum and inv. mass resolution similar for Boss and CGEMBoss and higher for CgemBoss at low momenta Tracking efficiencies: Better for proton than antiproton. At large momenta Cgemboss tracking efficiencies similar or higher than for Boss, but lower at lower momenta Effiiciencies decrease at high and low polar angles Cristina Morales, /11 13

55 Summary e+e- mu+mu-g Similar invariant mass resolutions by CGEMBoss and Boss. Little 1 MeV shift. Tracking efficienciencies higher for CGEMBoss except at low pt Similar selection efficiencies. At larger pt investigations ongoing Differences in the reconstructed track momentum for p> 1.7 GeV need to be understood 20

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57 Boss full MDC Boss outermdc CCGEMBoss 42

58 left corner (low p) (slightly) 58

59 boss665p01 CGEM Boss665b mu+,mu- boss665p01 CGEMBoss665b mu+,mu- (investigations ongoing) 20

60 Boss665p01 CCGEMBoss MC true

61 Boss665p01 CGEMBoss CGEMBoss and Boss for soft pions. Larger efficiencies for Boss

62 Boss CGEMBoss Boss CGEMBoss Boss CGEMBoss Boss 33

63 CGEMBoss and Boss

64 for GeV Charge-dependent shift observed in Rxy using CGEMBoss 51

65 for 2.9 GeV Charge-dependent shift observed in CGEMBoss reduced in comparison to Ecm = 2.39 GeV 48