LHCb EM calorimeter and ?? detection June 23rd 1999 BEAUTY

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LHCb EM calorimeter and ?? detectionJune 23rd
1999 BEAUTY  99Bled,Slovenia

• LHCb collaboration
• presented by
• Agnieszka Jacholkowska
• CERN and LAL-Orsay

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Plan of talk

• LHCb calorimeters
• Identification of photons,electrons and hadrons
• for L0 trigger
• ?? reconstruction
• Bd 0 ? ??-?0 analysis
• Summary

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Horizontal vue
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Preshower (PS) and pad chamber

• AIM
• Identification of electrons and photons.
• Pion rejection with respect to electrons,
• (tests pion rejection factor of ? 10. for
  E ? ? 5 GeV).
• TYPE lead and scintillator (14mm/10mm) - 2.5 X0.
• Geometry matched to ECAL.
• Readout PMs.
• Pad Chamber 1st m chamber or separate
  scintillator matrix.

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Electromagnetic calorimeter (ECAL)

• AIM
• Trigger for electrons and photons by ET
  measurement.
• Electron and photon energy measurement for
  offline reconstruction.
• p0 reconstruction.
• TYPE Shashlik plus WLS fibers read with fast PMs
  .
• Paralepipedic modules of 70 layers (pb 2 mm,
  scintillator 4 mm).
• Variable granularity to keep particle occupancy
  between 5 and 10 ,
• ? around 6000 modules .
• Acceptance 300x250 mrad , beam hole of 30x30
  mrad.
• Dynamic range adapted for different zones (50MeV
  to 200 GeV for the central region ) 12 bits ADC
  used , signal collection time 25 ns.
• Resolution for 25 X0

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ECAL
Preshower
ECAL Geometry Outer section 12.42 cm cells 3008
modules Inner section 4.14cm cells 2624
modules Acceptance 306 x 252 mrad
437 mm
70 layers Pb 2mm Sc 4mm
890 mm
PM
Space for cables
320 mm
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Hadronic calorimeter (HCAL)

• AIM
• Hadron trigger by single cluster ET
  measurement.
• Improvement of the electron-hadron separation at
  high energy.
• Muon identification .
• Pileup rejection by the total energy
  measurement.
• TYPE Scintillator / iron sampling structure with
  scintillating tiles parallel to the beam axis.
• Scintillators coupled to WLS fibres read with
  fast PMs.
• Dynamic range 0.1 - 300. GeV.
• Resolution for 5.6 lI

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Trigger Level 0 Search 2x2 algorithm

• AIM Search for energy deposits in the two
  calorimeters separately.
• Input rate of L0 trigger 40 MHz.
• Rate reduction factor 40.
• To reduce the number of interconnections, a
  search for the highest ET in 2x2 blocks in
• a region of 8x8 will be directly done.
• No more than ?100 maximas possible for
• 6000 channels of Ecal
• No more than ? 25 maximas possible for
• 1500 channels of Hcal
• Only these informations are sent to a validation
  unit where the informations from the pad chamber
  for shower localisation are incorporated with
  those from preshower for electron/hadron
  separation.
• The  highest electron and photon candidates are
  selected and sent to a decision unit.
• For the hadron trigger the two highest candidates
• and possibly the total energy are sent.

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L0 setup and performance
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?0 reconstruction

• ADVANTAGE 12 m lever arm and good granularity
  of EM calorimeter.
• PHOTON candidate electromagnetic cluster from
  neutral.
• algorithm ? search of maximum in a 3x3 cell
  aggregation in EM calorimeter.
• HAD energy not checked.
• No charged track pointing required.
• Position determination done with s-wave
  algorithm.
• Overlapping photons at least 1 cell separation.
• ?0 candidate from 2 resolved photons in
• (use of one cluster ?0 under study)
• E? ? 2 GeV .
  Bd 0 ? ??-?0
• No mass constraint.
• Resolution 5 - 7 MeV
• depending on ? angle.
• S (?0)/B(comb) ? 1 .
• Efficiency 0.25.

? these cuts were used in Bd 0 ? ??-?0
analysis.
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Analyses with ?0 and ?

• Channels with ?0
• Bd0 ? ??-?0
• high energy ?0 .
• BRs of order of 10-5 - 10-6 .
• ? Measurement of ? angle.
• Bd0 ? D0 K where D0 ? K- ??0
• medium energy ?0 .
• BRs of order of 10-7 - 10-8 ..
• ? Measurement of ? angle.
• Radiative Bd0 decays
• Bd0 ? K ?
• high ET ? (trigger threshold set to 4.0
  GeV).
• BRs of order of 10-5 ..
• ? Measurement of New Physics.

? Bd0 ? K ? b inclusive
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Bd0 ? ??-?0 analysis
INTRODUCTION to Bd0 ? 3?
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Bd0 ? ??-?0 analysis
The DALITZ Plot
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Bd0 ? ??-?0 analysis
PARAMETRISATION
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Bd0 ? ??-?0 analysis
Expected Event Yields
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Bd0 ? ??-?0 analysis
EXPERIMENTAL Cuts
? Background suppression factor 10-7 but
acceptance after all cuts and Trigger and Tagging
? 1 ? .
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Bd0 ? ??-?0 analysis
EXPERIMENTAL Cuts (Cont)
Expectation
Expectation
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Bd0 ? ??-?0 analysis
FITTING Method
A likelihood function is minimised on the event
by event basis -logL -?logMi2/M02 norma
lisation M0 for the matrix element is evaluated
with MC integration.One and two parameter fit and
two parameter scan have been performed without
including background.
1 Parameter fit of ? - 2 years data
Accuracy on ? of 3 0 for 1 year data
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Bd0 ? ??-?0 analysis
2 parameter FIT ? vs T00 ? 77.0 0 ? ?
4.10 T00 0.695 ?T00 0.05
2 parameter ? SCAN T- and T00 fitted
Penguins 0. mirror solution
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SUMMARY

• CALORIMETERS constitute important part of LHCb
  spectrometer.
• For electron ,photon and hadron level 0 trigger.
• Energy measurement for electrons and photons.
• ?0 reconstruction for analyses of channels Bd0
  ? 3?
• or Bd0 ? D0 K.
• Single ? reconstruction for radiative Bd decays
• such as Bd ? K ? .
• Bd 0 ? ??-?0 channel
• benchmark channel for ?0 reconstruction.
• Will be used for the determintion of the CKM
  angle ?
• after suppression of the combinatorial background
  from b inclusive events.
• The Dalitz plot analysis requires further
  developments in fitting procedure with inclusion
  of all other contributions providing other
  phases.
• We will make profit of future results produced by
• b-factories (BRs, upper limits , CLs , ).