Status%20of%20PEP%20II%20and%20BABAR

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Status of PEP II and BABAR

• Luca Lista
• INFN Sezione di Napoli

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PEP-II

• is the SLAC asymmetric high luminosisty B
  factory running at the Y(4S) resonance.
• Toghether with the

BABAR experiment
is designed to perform a sytematic study of
CP violation in B meson decays and to study a
wide range of B, charm, t, and gg physics.
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PEP-II

• The design luminosity is 3x1033cm-2s-1
  (ultimately will reach 1034cm-2s-1) which allows
  to obtain 30 fb-1/year (3x107 B0 mesons
  pairs/year)
• The electron and positron beams have energies of
  9 and 3.1 GeV respectively.

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PEP-II

• The Y(4S) is boosted in the laboratory frame to
  achieve a measurable separation of the decay
  vertices. This feature of PEP-II, toghether with
  a precise vertex detector, provides a measure of
  t2 - t1, the decay times difference of the two
  B.
• ?z increases to 250 mm in average from 30 mm in
  the case of no boost

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Interaction region
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PEP-II parameters
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Status of the machine

• May-June 1997 e- injection into HER
  (completed)
• Sep.-Nov. 1997 e injection in the LER
• Dec.97-Jan.98 1A stored in the HER
• Jan.-Mar. 98 Install IR and finish LER
• Apr. 1998 Commissioning LER with full IR
• May 98 Start IR and collision tests
• Beginning 99 BaBar installed on the IR
• Early 99 Start BaBar physics program

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BABAR detector
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BABAR collaborators
Italy INFN - Frascati INFN - Genova,
Dipt. di Fisica INFN - Milan INFN -
Naples / Universita' "Federico II", Naples
INFN - Padova INFN - Pavia INFN -
Pisa INFN - Roma / Universita di Roma "La
Sapienza" INFN - Torino INFN -
Trieste Norway University of Bergen
Russia Novosibirsk Institute of Nuclear
Physics Taiwan Institute of Physics,
Academia Sinica United Kingdom UK BABAR
Community University of Bristol
University of Edinburgh Imperial College
(London) The University of Liverpool
Manchester University Queen Mary and
Westfield College, University of London
United States California Institute of
Technology (Caltech) University of
California, Irvine (UCI) University of
California, Santa Barbara (UCSB) University
of California, Santa Cruz (UCSC) Colorado
State University (CSU) University of
Colorado, Boulder Iowa State University
(ISU) University of Louisville, Kentucky
Lawrence Berkeley National Laboratory (LBNL)
Lawrence Livermore National Laboratory (LLNL)
HEP group University of Maryland
University of Mississippi University of
Notre Dame Prairie View A M University
Rutgers University Stanford Linear
Accelerator Center (SLAC) Stanford
University University of Texas, Dallas
University of Wisconsin, Madison
Canada University of British Columbia,
Vancouver McGill University TRIUMF,
Vancouver, BC University of Victoria,
Victoria China Institute of High Energy
Physics France Ecole Polytechnique
(Palaiseau) L.A.P.P. (Annecy) LPNHE
Univ. Paris VI VII LAL (Orsay) CEA
(Saclay) Particle Physics Germany Ruhr
University, Bochum Dresden Nuclear and
Particle Physics Institute
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Physics Program

• CP violation studies, with measurements of sin2a
  and sin2b
• CKM matrix determination (Vcb, Vub)
• Rare B decays
• Other non-CP B physics
• Charm, t and two photon physics

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Typical CP event
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CP asymmetry measurement
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Requirements for CP sensitivity

• Reconstruct B0 decays in a wide range of
  exclusive final states with high efficiency and
  low background
• Tag the flavour of the non-CP B meson with high
  efficiency and purity
• Measure the relative decay time of the two B
  mesons to determine time-dependent CP asymmetries

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Silicon Vertex Detector

• The average separation of the two B vertices is
  250 mm
• The Svt provides 80 mm resolution_ less than 10
  loss in the precision of the asymmetry
  measurement
• Tracking for ptlt100 MeV/c

• 5 layers of Si double-sided microstrip detector
• sz, xy 50mm/pt Å 15 mm
• sj, q 1.6 mrad/pt

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Silicon Vertex Detector
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Silicon Vertex Detector
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Drift Chamber

• Many CP final states require precise and
  efficient tracking measurements(B0pp-, B0yK0S
  with K0S pp-, etc.)

• 40 stereo layers
• low multiple scattering He-Isobutane mixture
• spt/pt 0.21 Å 0.14 pt

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Drift Chamber
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• End plates and wiring robot complete

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DIRC
Detector of Internally Reflected Cerenkov light

• 156 quartz bars and 13000 photomultipliers
• ³ 4s p/K separation up to 4 GeV/c

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Particle Identification with DIRC

• Fundamental for kaon tagging B flavour(bcs
  chain)
• Provides a reduction of the B0pK- background to
  B0pp-
• Study of exclusive channels
• ...

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Electromagnetic calorimeter

• Electron identification foundamental for leptonic
  tagging
• Good p0 mass resolution and efficiency (B0yK0S
  with K0S p0p0, ...)

• 7000 CsI crystals
• sE/E 1 / Å 1.2

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Electromagnetic Calorimeter
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Electromagnetic Calorimeter
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Instrumented Flux Return

• Muon identification is foundamental for lepton
  tagging
• K0L identification allow the study of the channel
  B0J/yK0L

• Fine iron segmentation with 18/19 planes of
  Resistive Plate Counters (RPC) plus a cylindrical
  RPC inside the solenoid
• muon detection down to 500 MeV/c
• neutral hadron detection
• RPC installation has begun

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IFR
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m and K0L efficiency
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RPC performances
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Computing and Software

• 109 events/year, 100 Tbytes/year of tape storage
• Software has being developping world-wide
• Non traditional OO approach using C and
  commercial tools (Objectivity, Rogue Wave
  Tools.h,)

• Mock Data Challange-I successfully completed
  50000 events fully simulated and reconstructed
  (108 next year, MDC-II)

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BABAR CP reach
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Physics Workshops

• A series of four workshops on BaBar physics with
  theorists and experimentalists will produce the
  BaBar physics book.The last workshop will take
  place at the end of september.
• Updated results will follow

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Physics Groups

• 12. CP-violation in Neutral B Meson Decays
• 3. Extraction of Gamma
• 4. Extraction of Vub, Vcb from B decays
• 5. Rare Decays, and Beyond the Standard Model
• 6. B decay Models
• 7. Other Non-CP B Physics
• 8. Tau, Charm, QCD and Two-photon Physics
• 9. Overall Unitarity Triangle Sensitivity

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Conclusions

• PEP-II schedule is well advanced
• The construction of BaBar has started, on track
  for the schedule
• Physics will start early in 1999
• BaBar will provide the opportunity to make
  systematic studies of CP violation (and more)