Transcript Beams and Bubble Chambers: The World of Baryon Physics

Saxon Fest:A Celebration
Beams and Bubble Chambers
The World of Baryon Physics
R.J.Cashmore
Brasenose College and Dept of Physics
Oxford
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A Brief CV
Born
27 Oct 1945
Education
Manchester Grammar School 1956 - 63
Balliol College Oxford
1963 - 68
Employment
JRF Jesus College
1968 - 70
RA Columbia University
1970 - 73
SO,PSO RAL
1973 - 90
Kelvin Prof at Glasgow Univ. 1990 - 2008
Honours
FRSE
1993
FRAS
2005
OBE
2005
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Manchester Grammar School
Very able and conscientious
 No games player,secretary of
Philosophical Society,trombonist
 Apart from a scholar .. Very sound
commoner
 Paid 30 shillings to enter and …….


Awarded a Brackenbury Open Scholarship
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Balliol College
Took Prelims in March 63 … cost 5 pounds
 Thereby avoiding exams for 3 years
 Jenkyns Prize 1965
 Scott Prize 1966
 Travelling Scholarship to NERC Canada
Where he was ‘most impressed by the
vastness’,studied laser interferometry,and
found ‘the Canadians most friendly’

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Research
Thesis Oct 1969
‘A Study of Elementary Particle Interactions using the Bubble
Chamber Technique’
Pi- Proton -> Pi Pi Nucleon at 456/505/552 Mev/c
Thesis Adviser John Mulvey ( & Willie Chinowsky)
Acknowledges
DHW for pleasure of working in NPL
Balliol for occasional support
and Scanning Girls for their support
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Why the Topic ?
Kirz anomaly ….. pi pi mass bump that
changed with incident beam energy
(In fact Norman Booth had also been
implicated in this debate)
 Was it an I=J=0 pipi resonance?
An S wave resonance?
 Was it due to a baryon resonance?
A P11 nucleon resonance?

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The BUBBLE CHAMBER and
the BEAMS
Beams 456/505/552 MeV/c
400/590/660/740 MeV/c
Needed clever design to get rid of electrons
Saclay 80cms hydrogen chamber
used at RAL
(NIMROD)
and SACLAY (SATURNE)
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Computers
PDP 8 to record all the measurements
and produce mountains of paper tape
 KDF 9 to read the tapes and reconstruct
and kinematically fit the reactions

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Graduate Students Activities
Designed and tuned the beams
 Scanned and measured the film
 Processed all the results
 Developed New Analyses
 Wrote the paper

All chasing the energy dependence of
phase of the pipi s-wave interaction
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Baryon Resonances
Only the ground state multiplets and a
few beyond were known
In fact piN,pipiN final states were to pave
the way for the spectrum we now know
SU(3) and SU(6) structures existed
Baryons qqq and Mesons q-anti q
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The Baryon Octet
p
n

-


0

+

0
-

0
+
The Baryon Decuplet

-


-

+
0
++


0

+
-



-
0
+
The u,d and s quarks
u 2/3
d -1/3
+
s -1/3
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u,d,s quark structures
n
p
udd
uud

-

uds
dss

0
+
dds
0


uus
-

0
uss
+
u,d,s quark structures
-

ddd
udd


-

+
0
++

uuu
uud

0

uss
uus
uds
+
-


uss
dss
sss

-
0
+
Baryon Resonances
Only the ground state multiplets and a
few beyond were known
In fact piN,pipiN final states were to pave
the way for the spectrum we now know
SU(3) and SU(6) structures existed
Baryons qqq and Mesons q-anti q
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OXFORD at that TIME
Dick Dalitz ,the father of ‘real’ quarks, was
the ‘great man’
The language was quarks
and no one else in the world believed in them
until DIS(1969) and PSI’s(1974)
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e


~0.0 MeV 0 e
0.5 MeV -1 e
~0.0 MeV 0 e
0.1 GeV -1 e
~0.0 MeV 0 e
1.8 GeV -1 e
e


uuu
ccc
ttt
5.0 MeV +2/3 e
10.5 MeV -1/3 e
1.3 GeV +2/3 e
0.2 GeV -1/3 e
0.175 TeV +2/3 e
4.3 GeV -1/3 e
ddd
sss
bbb
( )( )( )
Quarks
Leptons
The Particles of the Standard Model
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In Conclusion
It has been great having you and Margaret
as friends
It has been great working with you over
these many years
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