Transcript Review of E760/E835 - Illinois Institute of Technology

Review of E760/E835
Keith Gollwitzer
Antiproton Source Department
Accelerator Division
Fermi National Accelerator Laboratory
Project X 2nd Physics Workshop
January 25, 2008
Charmonium Masses and Widths
11
E760/E835 main purposes
were to do precision
measurements of the
Charmonium spectrum as
well as the
discovery/confirmation of
1P and η /
1
c
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Thi ck sol i l di nes
Technique
The Accumulator is the Spectrometer
Annihilation of pbar p to form each state
All quantum numbers can be formed
Detector is a big scalar
Scan beam energy to map out resonance
Precision Measurements
“Clean” electron/positron Signals
/  J/ X  e+e- X
/  e+e-
Threshold Cernekov
Shower shape
--
1 State Scans (1990-1)
Beam Scan of ψ(2S)
Breit-Wigner line shape
Convolution results in the observed cross section
Beam Profiles
Most precise measurement of the
ψ(2S) width despite much
smaller statistics than e+e-
1 & 2 Scans
0 Scan
Could be more precise with
more integrated luminosity
Interference will be shown later
Two Photon Final States
Takes work to
understand the feeddown from multi-photon
final states
CCAL threshold of
5/20MeV
pbarp 
0 0
0 

These data are from
the c peak
The precision of the mass and width
of the c needs to be improved
E760 & E835 only reported pbarp 
Need to observe c in more channels
Interference next slide
pbarp  0 & 2  
Interference can be your friend
The continuum “amplifies” the
resonance
E835 example in 4 photons
pbarp c0  0 0 ,  , /
Should expand interference
analyses to more channels;
in particular pbarp at 90o in the
center of mass system
Confirmations?
Searches?
Discoveries?
1P
1
or hc JPC = 1+-
The hc mass is important to
understanding hyperfine
splitting.
The hc width has not been
measured
pbarp  hc   c   ()
E760: pbarp  hc  J/ 0  (e+e-) ()
Search for pbarp  ηc/  
PDG
M = 3637 ± 4 MeV
Г = 14 ± 7 MeV
Maximum Accumulator Energy
Favorite Theorist Point
of the moment
c/ search for possible hindered
M1 transition to J/
Search using inclusive J/
The States
J PC
--
1
++
2
1 ++
? ??
c
hc c/

0 12
/
Other Physics Measurements
pbarp   + 
pbarp  two neutral mesons
 0 0
 0
Scaling Rule?
pbarp  two neutral particles
Proton Magnetic Form Factor
pbarp  6
Summary
• Direct formation of any Charmonium state (of
any quantum numbers) is a unique advantage to
making precision measurements of the mass
and width
• E760/E835 utilized “clean” J/ inclusive and two
photon final states to “count” the number of
events at each beam energy setting against the
very large hadronic interaction background
• It is hard to discover narrow states scanning a
large energy range
– Precision measurements possible once mass is
nearly known
• Like ILC precision measurements will be possible once
hadron machine(s) make discoveries