Comparing Vertex from Z μμ to the Remaining Tracks

SEDWG April 22, 2023 R. Kelley

Comparing Vertex from Z μμ to the Remaining

Tracks

April 22, 2023

Ryan Kelley

SEDWG April 22, 2023 R. Kelley2

Introduction

• Compare vertex of the Z μμ • Idea is to take the μ’s from the Z

μ from primary interaction point used two μ tracks to form a vertex

using KalmanVertexFitter

used remaining tracks with pT > (1.0, 0.5, 0) or |p| > (0.5,1.0, 2.0) to form another vertex

using KalmanVertexFitter using TrimmedVertexFitter using AdaptiveVertexFitter

compare the difference in X,Y,Z positions


Selection• Used SEDWG PAT configuration 2_2_10• Datasets:

– /Zmumu/Summer08_IDEAL_V11_redigi_v2/GEN-SIM-RECO

• 20K Events• Selection

– μ's• pT > 10.0 GeV• GlobalMuonPromptTight (recommended by μ I.D. note)

– χ2/dof < 10

– |d0| < 2 mm (designed to reject decays in flight and punch through)

– nHits from track ≥ 11

– Z Candidates• Created Z’s from μ+μ- (from above mu’s)

• mZ – 4ΓZ < mμ+μ- < mZ + 4ΓZ

3


Several Fitting Option oob

• The fitters now available are – The KalmanVertexFitter: the simple least-squares algorithm (uses all the tracks

with a weight of 1)– The AdaptiveVertexFitter: iterative re-weighted KalmanFitter? which down-

weights tracks according to their distance to the vertex– The TrimmedVertexFitter: conventional robust version of the Kalman fitter, which

removes tracks incompatible with the vertex– The GaussianSumFitter: fitter using the non-Gaussian distributions of

measurement errors– The AdaptiveGsfVertexFitter: a combination of the adaptive fitter and the

Gaussian-sum fitter

• The GSF fitters are designed for objects that use GSF error calculations (e.g. Electrons)

– wouldn’t work for tracker Tracks (from the μ’s and general tracks)

• https://twiki.cern.ch/twiki/bin/view/CMS/SWGuideVertexFitting

4


Vertex formed from Tracks

• Used all tracks not from the Z candidates’ μ’s with– pT > 1.0 GeV

– pT > 500 MeV

– |p| > 500 MeV– |p| > 1.0 GeV– |p| > 2.0 MeV

– no pT cut

5


Convergence of the Fits

• Only looked at the first three types– GSF fitting primarily for electrons

– KVF and AVF w.r.t BeamSpot (TVF not implemented in CMSSW)

• Log scale• The TVF rejects tracks when

they’re killing the fit more invalid.

6


Validity of the Fits

7


χ2/dof of the Fits

8


χ2/dof of the Fits (zoom)

9


# d.o.f of Fits

10


χ2 prob of Fits

11


# Tracks Used

12


Track Weights Used

13


# Tracks Used vs # d.o.f

14



15



16



17



18



19


Vertex formed from Z’s

• Used the two tracks not from the Z candidates’ μ’s with– Used KalmanVertexFitter since only two

tracks and we want the weight always =1

20


Validity and # d.o.f of vertex from Z candidates

21


χ2/dof and χ2 prob. of vertex from Z candidates

22


Delta = Track - Z

• Used attribute (vx, vy, vz) to calculate

– Δvx = vxtracks – vx

z

– Δvy = vytracks – vy

z

– Δvz = vztracks – vz

z

• Showing AVF results

23


Δvx

24

• Δvx = vxtracks – vx

z

• no pT on Tracks


Δvx

25


z

• pT > 500 MeV on Tracks


Δvx

26


z

• pT > 1.0 GeV on Tracks


Δvx

27


z


Δvx

28


z


Δvx

29


z


Δvy

30

• Δvy = vytracks – vy

z

• no pT on Tracks


Δvy

31


z



Δvy

32


z



Δvy

33


z


Δvy

34


z


Δvy

35


z


Δvz

36

• Δvz = vztracks - vz

z

• no pT on Tracks


Δvz

37


z



Δvz

38


z



Δvz

39

• Δvz = vztracks – vz

z


Δvz

40


z



Δvz

41


z

• no pT on Tracks


Resolution = Track - Gen


– Res vx = vxtracks – vx

gen

– Res vy = vytracks – vy

gen

– Res vz = vztracks – vz

gen


42


Resolution vxTracks

43

• Res vx = vxtracks - vx

gen

• no pT on Tracks


Resolution vxTracks

44


gen



Resolution vxTracks

45


gen

• pT > 1 GeV on Tracks


Resolution vxTracks

46

• Res vx = vxtracks – vx

gen


Resolution vxTracks

47


gen


Resolution vxTracks

48


gen


Resolution vytracks

49

• Res vy = vytracks - vy

gen

• no pT on Tracks


Resolution vytracks

50


gen



Resolution vytracks

51


gen



Resolution vytracks

52

• Res vy = vytracks – vy

gen


Resolution vytracks

53


gen


Resolution vytracks

54


gen


Resolution vztracks

55

• Res vz = vztracks - vz

gen

• no pT on Tracks


Resolution vztracks

56


gen



Resolution vztracks

57


gen



Resolution vztracks

58

• Res vz = vztracks – vz

gen


Resolution vztracks

59


gen


Resolution vztracks

60


gen


Resolution = Z - Gen


– Res vx = vxZ – vx

gen

– Res vy = vyZ – vy

gen

– Res vz = vzZ – vz

gen


61


Resolution vxZ

62

• Res vx = vxZ – vx

gen


Resolution vyZ

63

• Res vy = vyZ - vy

gen

• μ = 0.06 μm, σ = 12 μm


Resolution vzZ

64

• Res vz = vzZ – vz

gen


Back Up

65


Definitions

• PCA– Point of Closest

approach (x0,y0,z0)

66


vx


vy


vz


vxz and vy

z

70


vzz

71


Calculation of Weights

• Used sum of two Gaussians (core + wide)

72

• Mean

• Standard Deviation• √variance


μ Variables: pT

73


μ Variables: η

74

What causes this bump?


μ Variables: Φ

75


μ Variables: x0 and y0

76


μ Variables: z0

77


μ Variables: d0

78


μ Variables: # hits and χ2

79


Number of Z’s per Event

80

Documents

Comparing Vertex from Z μμ to the Remaining Tracks