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B s signal selection. Donatella Lucchesi University and INFN Padova for B s Mixing group. CDF Collaboration Meeting June 7, 2006. The Blessed Selections: hadronic decays. Signal B s D s  D s . B s D s  D s  KK D s K *0 K K *0 K D s 3 B s D s 3

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B s signal selection

Bs signal selection

Donatella Lucchesi

University and INFN Padova


Bs Mixing group

CDF Collaboration Meeting

June 7, 2006

The blessed selections hadronic decays
The Blessed Selections: hadronic decays

Signal BsDs Ds 


Ds  KK

Ds K*0K K*0 K

Ds 3


Ds 

Ds K*0K



B mesons


Combinatorial background

Donatella Lucchesi

Hadronic b s decays summary
Hadronic Bs decays summary

B+D0 ~ 26,000

B0D- ~ 22,000

Donatella Lucchesi

Blessed selection b s semileptonic decays
Blessed selection Bs semileptonic Decays


Ds  KK

Ds K*0K K*0 K

Ds 3

Total yield:

Dsl ~37,000 events

Donatella Lucchesi

What can we do to improve it
What can we do to improve it?

  • Include PID in the selection

  • Use NN to discriminate signal from background

  • Add new decay modes

Donatella Lucchesi

Including pid in the selections
Including PID in the selections

BsDs Ds K*0K K*0 K has reflection from

B0D D Kpp when you give K mass to p

Standard analysis use

D+ veto:

|MKpp – MD+|>24 MeV

A. Heijboer

Donatella Lucchesi

Including pid in the selections1
Including PID in the selections

Aart proposal:

|MKpp – MD+|>18 MeV OR CCL0


Give this to NN

A. Heijboer

J. Mulmestadt

Johannes idea:

LR cut event by event

increases Ds 1640

In progress the Bs

significance evaluation

Donatella Lucchesi

Neural network selections
Neural Network selections

B. Casal, K. Anikeev


  • Train NN to separate signal from bckg (side bands)

  • Optimize to maximize

  • Fit mass distribution using the actual mixing fitter

Rectangular cuts

NN cuts

Increase 33% like adding 78% of more data

Donatella Lucchesi

Neural network selections summary
Neural Network selections summary

B. Casal, K. Anikeev

57.78/43.30=1.3 improvement A

Use wrong charge events as background in the future?

Donatella Lucchesi

Partially reconstructed b
Partially Reconstructed B

Jeff Miles

BD, D*p ++0 , D*Dg/p0 treated as hadronic?

  • Large yields (same order of fully reconstructed)

  • High k-factor, lose soft g/p0

  • Lower S/B

Depend on


Different K def. investigated

finally use the standard one

Donatella Lucchesi

Partially reconstructed b1
Partially Reconstructed B

Amanda Deisher

B0D* -[D0 -] +

5.00<mass<5.35 GeV/c2

Low combinatorial


ct2= 464.6 +14.2–13.5 mm

Above 5.17 GeV

D*p and D*K

Donatella Lucchesi

New decay modes
New Decay Modes

Simone Pagan Griso

BsDs Ds KsK Ks has reflection from

B0D D 3p as for Ds K*0K K*0 K

Different topology easy to separate

~270 events 1fb-1

Using PID

16% increase

Donatella Lucchesi

Semileptonic decay modes
Semileptonic decay modes

V. Tiwari, G. Gomez-Ceballos

  • Improve event selection including PID BsDslx:

    • Dsfp combinatorial bck reduce by factor 2

    • Ds K*K yield increased by factor ~2.5 and

      combinatorial bck reduced by factor 2

  • Include l+SVT dataset

  • Remove the ct* cut

Noticeable gain

Donatella Lucchesi


  • The number of events can be increased by including

  • new decay modes, partially reconstructed events

  • and by optimizing cuts.

  • Plan for the summer:

  • Include partially reconstructed modes and optimize cuts.

  • The actual gain on Dms significance will be the

  • combination of all the effect.

  • Expected improvements on sA:

  • 1.3 for the hadronic decay modes cuts optimization

  • “Something” for semileptonic decays

  • Under evaluation for adding partially reconstructed

  • hadronic decay

Donatella Lucchesi