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First Events from BELLE

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					                   Results from BELLE
                    IVth Rencontres du Vietnam
                          Hanoi, Vietnam



               Daniel Marlow
                   BELLE
            Princeton University
                July 22, 2000

July 2000       Results from BELLE               1
                      Initial Physics Goal
                       
Our principal
physics goal is to
                                    , 
test the KM picture          
                           V                      Vtd
                                       2
of CP violation by          ub
measuring the              A  3
                                                  A3
angle 1 (aka  )
of the unitarity
triangle.                    3                  1
                                                                    
In phase II, we will
seek to measure  2
                                        Vcb             1,0
and  3 ( &  ).                       A3
   July 2000                Results from BELLE                  2
                  Existing Constraints

                                            Existing measurements
    F. Parodi et al.
                                            of B 0 B 0 mixing and
                                             Vub limit the
                                            allowed region in the
                                              ,  plane.



July 2000              Results from BELLE                     3
                     The Measurement
                                           
                               tag
                                                    D0
                                                         Need to:
                     0
e      e       B
                                                         •Measure momenta
             0
                     z                                  •ID leptons & K’s
         B
                 J /                                    •Measure vertices
                           
     K0
                        CP

 July 2000                     Results from BELLE                            4
                           The Measurement
The time-dependent
asymmetry appears
mainly as a mean shift
in the z distribution
between events tagged
         0
as   B        decays and
                           0
events tagged as B
decays.




  July 2000                    Results from BELLE   5
                                     
 The KEK-B Asymmetric e e Collider

                             KEK-B is similar to PEP-
                             II in many ways, although
                             there is a (potentially)
                             important difference in the
                     ee
                             way in which the beams
                             are brought into collision.




July 2000     Results from BELLE                       6
                    Recent Run Snapshot

Snapshot
chosen at
randomly
selected
time.




Lpeak  1.8 1033 cm-2s -1




    July 2000                Results from BELLE   7
 pb-1/day          Daily Luminosity History


                                                80 pb-1/day
                                                (recently
                                                down a bit)
pb-1




                                                6.2 fb-1 total



                          date
       July 2000           Results from BELLE             8
            The Magnet




July 2000    Results from BELLE   9
             The BELLE Collaboration




            About 10 Countries, 50 Institutes, & 250 People

July 2000                    Results from BELLE               10
       The Silicon Vertex Detector (SVD)




   Sensors: HPK DS640 (DSSD’s)
   Readout: VA1 chip from IDEAS
July 2000             Results from BELLE   11
                SVD Performance

CDC/SVD Track
Matching:

    97%




  July 2000         Results from BELLE   12
        CDC Performance (Cosmic Rays)




July 2000         Results from BELLE    13
              K S    
                0

    CDC
               eff  4.6 MeV/ c 2
Performance




                               M      (GeV/ c 2 )
  July 2000        Results from BELLE                   14
        Particle ID (dE/dx, ToF, & Aerogel)




        D  D 0   
              K 


July 2000                  Results from BELLE   15
            CsI EM Calorimeter Performance
                0 Reconstruction
                   E  50 MeV




                                 Reconstruction



July 2000                  Results from BELLE         16
 Muon
Detection
B   J / K 
plus tag - side 
Note that there
are no missing
hits in the layers
of the muon
system, except at
the sector edges,
where there is
support structure.

   July 2000         Results from BELLE   17
                                 0
                        K        L   Detection

Pmiss  P4 S        P          i
                   i  , h 

            PK L

                        Pm iss
        




July 2000                            Results from BELLE   18
            Inclusive Electron Spectrum




                       *
                     p e    GeV/ c
July 2000            Results from BELLE   19
            D Beam Constrained Mass




July 2000           Results from BELLE   20
                                    D0 Mass Plot

To warm up our
analysis machinery,
we have studied
charm lifetimes.




                      1.80             1.84               1.86     1.90
                                            M K   (GeV/ c 2 )
July 2000              Results from BELLE                          21
                                 D0 Lifetime




  -3000         -1000     1000   3000                  -3000   -1000     1000   3000
                tproper   (fs)                                 tproper   (fs)

       D  (414.8  3.8  3.4) fs
            0                            cf. PDG '00 D0  (412.6  2.8) fs

July 2000                         Results from BELLE                             22
                                DS Lifetimes




            
                  (479   17  6
                          16 8    ) fs       cf. PDG '00      
                                                                      (496 10 ) fs
                                                                            9
            DS                                                  DS

July 2000                                  Results from BELLE                          23
            Dilepton Mass Spectra


                                       5.5 fb-1




July 2000         Results from BELLE         24
            Exclusive Mode Reconstruction




                                            4.3 fb-1



                        
            B  J / K


July 2000             Results from BELLE      25
            Exclusive Mode Reconstruction




                                            4.3 fb-1




       B  J / K
            0         0
                      S




July 2000             Results from BELLE       26
               Exclusive Mode Reconstruction


We can also detect
  B 0  J / K L
events by detecting the
direction of the KL. This
mode complements the
                                                 KL
  B0  J / K S
mode, but has more
background.
                KL hits

   July 2000                Results from BELLE        27
                 Exclusive Mode Reconstruction



B  J / K
 0                    0
                      L
                                                  MC: histogram
                                                  Data: points


     5.2 fb-1




                                                 *
     July 2000             Results from BELLE   pB (GeV/ c)       28
              B   D 0  Reconstruction


The B  D 
              0   

mode represents a
background to the more
interesting Cabbibo
suppressed mode
     B   D0 K 




  July 2000              Results from BELLE   29
               B   D 0 K  Reconstruction




                              Kaon probability
Particle ID is an
effective tool in
pulling the B   D 0 K 
signal out from                                      B   D0 K 
underneath the B   D 0 
background.




                                                     E   (GeV)

   July 2000                    Results from BELLE           30
               B   D 0 K  Reconstruction


Particle ID is an
effective tool in
pulling the B   D 0 K 
signal out from
underneath the B   D 0 
background.




   July 2000                  Results from BELLE   31
 Neutral B
Mixing from
 Dileptons




 July 2000    Results from BELLE   32
                B Mixing from Dileptons

            md  0.467  .009 (stat)  .030 (sys) ps-1



                                                          Preliminary




July 2000                     Results from BELLE                 33
            Summary and Conclusions
• BELLE has accumulated ~6.2 fb-1of luminosity in
  its first ~year of operation.
• The detector is working well and the analysis
  machinery is beginning to produce results that are
  competitive with previous measurements.
• One can hope for further increases in luminosity in
  the months to come.
• Look for more results at Osaka.



July 2000            Results from BELLE            34

				
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