D0 Analysis in cucu200GeV using Micro Vertex Code

22
Analysis Meeting @ BNL September 24, 2008 J.Bouchet, J.Joseph, S.Margetis Kent State University 1

description

D0 Analysis in cucu200GeV using Micro Vertex Code. Analysis Meeting @ BNL September 24, 2008 J.Bouchet, J.Joseph, S.Margetis Kent State University. Cuts Used in MuKpi macro. pure D 0 : 950 MuDst files (400 possible D 0s per file) - |Zvertex| < 20 cm - NTpcHits > 15 - PowerPoint PPT Presentation

Transcript of D0 Analysis in cucu200GeV using Micro Vertex Code

Page 1: D0 Analysis in cucu200GeV using Micro Vertex Code

Analysis Meeting @ BNL September 24, 2008

J.Bouchet, J.Joseph, S.MargetisKent State University

1

Page 2: D0 Analysis in cucu200GeV using Micro Vertex Code

Cuts Used in MuKpi macropure D0 : 950 MuDst files (400 possible D0s per file) - |Zvertex| < 20 cm - NTpcHits > 15 - |η| in SSD acceptance, ie |η| <1.2 - pT > 0.1 GeV/c - decay length < 700μm D0Mix: 1 D0 embedded in Cu+Cu Hijing event, 290

files with 400 events. - same cuts as aboveReal Data: Cu+Cu@200GeV MinBias (P07ic) : - ran over 20,000 files - dEdx cuts + same cuts as in pureD0

2

The macro associates positive and negative tracks to reconstruct the invariant mass

Page 3: D0 Analysis in cucu200GeV using Micro Vertex Code

Pure D0 Sample

3

No CutsResolution:0.589%

• The Reconstruction Microvertex Code[MuKpi.C ] reconstructs D0 parameters pretty well in pure D0 sample. • Cuts on TpcHits(>20) and SiHits (SvtHits>0&SsdHits>0 )for pos and neg daughter tracks removes almost every bad associations in pure sample.

Resolution 0.589%

Page 4: D0 Analysis in cucu200GeV using Micro Vertex Code

D0Mix(No Cuts)

4

Real-all associationsFake-rotation of pion

Seems to be working with a cut on the Number of Tracks.

RealFake

We see a small correlation for mass =1.86 and the low multiplicity

Page 5: D0 Analysis in cucu200GeV using Micro Vertex Code

Background Subtraction

5

A Gaussian is fitted to the signal and a zero degree polynomial to the background.

Page 6: D0 Analysis in cucu200GeV using Micro Vertex Code

Looking at some attempted cuts in MuKpi.C with pure D0 and D0Mix sample

6

In order to remove fake association we can do a cut on dca, |DCApos – DCAneg|< 0.1With the help of silicon detectors there is more precision in DCAs and hence a more fine tuned cut in the analysis.

DCA of the Tracks

D0 MixPure D0

Page 7: D0 Analysis in cucu200GeV using Micro Vertex Code

D0 Mass with cut on Dca

7

Dca cut is applied in both longitudinal and transverse directions.

Page 8: D0 Analysis in cucu200GeV using Micro Vertex Code

Angle(made by Kaon in the CM frame) analysis in pure and D0Mix (For Ntracks<50)

8

A cut (|angle|< 0.8 ) can possibly remove some background .

Pure D0

Angle made by K- in the CM Frame

D0 Mix

Page 9: D0 Analysis in cucu200GeV using Micro Vertex Code

D0Mass(with a cut on the opening angle of Kaon)

9

With a cut on the opening angle of Kaon(in the CM frame) we possibly can improve the signal. But removing the cut on NTracks leads to disappearance of the D0signal in all cases!

Page 10: D0 Analysis in cucu200GeV using Micro Vertex Code

D0Mix: Combining cuts on Ntracks, Dca, opening angle of Kaon, momenta of daughter tracks etc.

10

• SsdHits(pos&neg) > 0• SvtHits( pos&neg) > 0• TpcHits(pos&neg) >20• NoTracks<50

•NoTracks <50•|Kaon opening angle| < 0.8•|pPos|>0.6, |pNeg|>0.6•ChargePosTrack >0, ChargeNegTrack <0•|dcaXY_pos – dcaXY_neg| < 0.1•|dcaZ_pos – dcaZ_neg| < 0.1

Here we tried two sets of cuts to see how well it reconstructs the D0Mass from the mix sample

Page 11: D0 Analysis in cucu200GeV using Micro Vertex Code

D0 Mix: Mass plot and background

11

The shape of the Background (for each association, rotation of the pion track through π) differs from the actual mass distribution and hence the subtraction can lead to over-estimation of D0.

• Mass plot with all the cuts mentioned in the previous slide• Background

Page 12: D0 Analysis in cucu200GeV using Micro Vertex Code

Recalculation of BackgroundTried random rotation in 2π for both daughters :

same resultsWe tried to rotate the track around the primary

vertex by rotating the pion track before doing the association.

In the following slides we look at three cuts: No of Tpc Hits, No of Si Hits and No of Tracks

12

Page 13: D0 Analysis in cucu200GeV using Micro Vertex Code

Fixed Rotation

13

All associationsBackground

Page 14: D0 Analysis in cucu200GeV using Micro Vertex Code

Real Data

14

Red = PiRed = Pi++Blue = K-Blue = K-

dEdx of Real Data

With the help of analyzed cuts in pure and mix D0 sample, we can now proceed to the Real Data and apply similar cuts with appropriate values.

Page 15: D0 Analysis in cucu200GeV using Micro Vertex Code

Real Data Mass plots

15

TrueFake

Page 16: D0 Analysis in cucu200GeV using Micro Vertex Code

OutlinesAnalysis of D0 reconstruction based on micro

vertex code (using SSD and SVT hits) to find and optimize proper cuts.

We looked at Pure and D0Mix sample.Applied different cuts in Pure and D0Mix to

enhance the signal.Investigation of background calculation(Like

sign & Mix Events)We plan to apply the same cuts but tuned for

the real data (looked at real data, but no signal so far)

We can utilize the SiliconHits to have more tight cuts on DCA 16

Page 17: D0 Analysis in cucu200GeV using Micro Vertex Code

BackUp slides

17

Page 18: D0 Analysis in cucu200GeV using Micro Vertex Code

Mass Resolution with Si and TpcHits (pure D0)

18

no cutσD0M

=0.01087

TPC > 30(*)σD0M =0.01054eff =81.5%

Si > 1(*)σD0M

=0.01068eff=44.5%

TPC>30 &&Si > 1(*)σD0M =0.01030eff=35.2%

Page 19: D0 Analysis in cucu200GeV using Micro Vertex Code

Daughter momenta(D0Mix)

19

Page 20: D0 Analysis in cucu200GeV using Micro Vertex Code

Daughter Characteristics

20

Page 21: D0 Analysis in cucu200GeV using Micro Vertex Code

Random Rotation(D0Mix)

21

Page 22: D0 Analysis in cucu200GeV using Micro Vertex Code

SigmaDca(D0Mix)

22

SigmaXY_pos – SigmaXY_neg

D0MixPure D0