B 0 0 from the calorimeter software point of view
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B 0  +  -  0 from the Calorimeter Software point of view PowerPoint PPT Presentation


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B 0  +  -  0 from the Calorimeter Software point of view. J. Lefrançois F. Machefert P. Robbe M-H Schune. Dalitz Plot Technical framework Some results. 2 regions in the Dalitz Plot : Fast  0 + fast  + + slow  - Slow  0 + fast  + + fast  -. M 2 (  -  0 ).

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B 0  +  -  0 from the Calorimeter Software point of view

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B 0 0 from the calorimeter software point of view

B0+-0 from the Calorimeter Software point of view

J. Lefrançois F. Machefert P. Robbe M-H Schune

  • Dalitz Plot

  • Technical framework

  • Some results

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 20031


B 0 0 from the calorimeter software point of view

2 regions in the Dalitz Plot :

Fast 0 + fast + + slow -

Slow 0 + fast + + fast -

M2(- 0)

+ or - is at rest in the B center of mass frame

M2(+ 0)

0 at rest in the B center of mass frame

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 20032


B 0 0 from the calorimeter software point of view

At truth level on B0+-0 events:

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 20033


B 0 0 from the calorimeter software point of view

Truth level lower zone of the Dalitz plot:

about 82% of the p0have separated clusters.

merged p0

For comparison : upper zone of the Dalitz plot:

pT(p0)

about 35% of the p0have separated clusters

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 20034


Framework

Framework

  • DaVinci v7r3 :

    • 103.5k signal events

    • 870.3k bb events

  • Use the event with only one Primary Vertex (PrimVtxFinder)

  • p0  g g (no merged p0 yet)

    • ET(g) > 200 MeV

    • use both converted and non converted g

TDR production

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 20035


Preselection cuts

Preselection cuts

  • Use the event with only one Primary Vertex (VtxFinder)

  • p0  g g (no merged p0 yet)

    • ET(g) > 200 MeV

    • use both converted and non converted g

  • p : pT > 150 MeV . 2(vtx) < 5 (zVtx –zPV)> 500 mm

  • ImpP(p )/sImpP > 2

  • Combine the  with the p0 (4-vector addition)

slowest p

fastest p

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 20036


B 0 0 from the calorimeter software point of view

p0 mass

M=140 0.3 MeV

=11.8 0.4 MeV

DaVinci v7r3

DaVinci v6r2

same g selection : both converted and non converted

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 20037


B 0 0 from the calorimeter software point of view

p0 efficiency

all p0in ECAL

p0in ECAL with p< 20 GeV

zoom

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 20038


B 0 0 from the calorimeter software point of view

Cuts optimized for this region

M(p+ p-) < 1200 MeV or M(p+p0) < 1200 MeV or M(p-p0) < 1200 MeV

2 regions M(p+p0)2 + M(p-p0) 2 < 10 GeV2

M(p+p0)2 + M(p-p0) 2 > 10 GeV2

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 20039


B 0 0 from the calorimeter software point of view

D [p] : defined by the p momentum and the first pointOnTrack

D [B] : defined by the B momentum and the PV

Use of the B0 direction

Rec. B

pmax

d(D[pmax], D[B])

d(D[pmin], D[B])

pmin

B line of flight

p0

PV

q

q angle between the B momentum and the B line of flight

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 200310


B 0 0 from the calorimeter software point of view

q : angle between the B momentum and the B line of flight

signal

bb

all plots normalized to the same area

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 200311


B 0 0 from the calorimeter software point of view

ImpP(p )/sImpP slowest p

dmax fastest p

bb

signal

overflow

a lot of bckgd for the slowest track, use only the detached ones

the fastest track is well measured, d should be close to 0

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 200312


B 0 0 from the calorimeter software point of view

pT(B0)

cos(q)p0

signal

bb

bb

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 200313


B 0 0 from the calorimeter software point of view

Double counting :

- 1 double counting on generic bb (2 entries)

- on signal : 242 entries : 171 after choice

always due to the p0

 choose the best p0 according to the p0 mass

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 200314


B 0 0 from the calorimeter software point of view

s=267 MeV

m=52904 MeV

the « signal cross-feed » background

bb

 200 MeV region is too wide

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 200315


B 0 0 from the calorimeter software point of view

Numbers for the lower region of the Dalitz plot

Several cand./event

Not always selecting the right one

Soft neutral matching ? (75% cut on cluster E)

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 200316


Conclusions

Conclusions

  • p0mass shifted by about 5 MeV

  • In the lower zone of the Dalitz plot M(p+p0)2 + M(p-p0) 2 < 10 GeV2 : better S/B

    .5 10-2  15. 10-2

  • Define the signal region within 100 MeV region S/B * 2

  • Use of the self cross-feed background

  • Specific background to be studied :

    • B0+- , K*g …

  • Merged p0 : still to be tried

B00 calorimeter Software Marie-Hélène Schune, LHCb Software week March 200317


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