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A Study of the Decay Properties
of the Charmed Baryo!l. At
C.E.K. Charlesworth
:\ Th<•sis submitted in conformity with the requirements
for the Degree of Doctor of Philosophy in the
University of Toronto
Department 0f Physics
University of Toronto
@C.E.K. Charlesworth 1992
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Abstract
The charmed baryon:\;!" has been observed usin.~ the :\RGt·s detector in the DORIS II
f+,:- storage rin11; at DESY. The ARGCS experiment is a -l;r magnetic solenoidal de
t.t·ct.or 11sed to observe e+F.- annihilations at center-of-mass energies around 10.4 GeV.
V'·ie have studied .') decays modes of the A;. The decay mode .\; - pK-;r+
was used to mca:rnre the ,\t fragmentation properties. A value of 0.24 ± 0.04 was
found for the Pett•rson et al. parameter E. and the u(.\n · BR(.\: - pK-r.+) was
rnt>asurf'd to lw ( 1·2.0±l.l±1.:3) pb. The decay modes ,\: - ;\;r+ and A; - ~o;r+
wt·rt· .tlso studied. ln the former the asymmetry parameter oA, was measured to
lw -1.U ± O.:>. indicating that parity is maximally violated in this decay. The two
prrnhwtion cross section times branching ratios were measured to be (2.2±0.3±0.3) pb
and (~.0±0.7±0.:3) pb respectively. Finally, a search was made for evidence of W
Pxd1ange in the decay A: ___. =:- K+rr+. This final state can arise through a simple
spt•ctator decay or via the more exotic W-exchange decay into =:·° K+. where the :=:·0
subst•qtwntly decays into =:-1!"+. The two body rate was measured to be (35±17)3 of
tlw thn•e body rate. indicating that a significant portion of the :=:- K+rr+ final state
may occur \"ia. \V-t•xchange.
A Study nf the Decay Properties of the charmed Baryon /\., Ph.D. l992 Department of Physics University of Toronto C~1tri.Lrna El iz:>l:>eth Kaye Charlcsworth
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Acknowledgements
:\one of this \\·ork would have bee!'. possible without the work of my co-authors whost•
names are listed on the next µage. In particular. I would like to thank my ft>llow
graduate students. Richard Van de Water. John Swain and .John Parson and Roh
Kutschke for their help and considerate or inconsiderate advice throu~hout tlw yt>ars.
Peter Krieger deserves particular thanks for showing me. among otht·r thin~s. how
to get to Insbeth. For being a fonrth in bridge and for acting as a lab animal fur
hot wax testing, I would like to thank David Britton. I would also likl' to t.ha.nk l~1>r
Gorelcv fnr lightim: all those candles for me. and for teaching me tht> polit.t• way t.n
drink vodka. I would like to thank my supervisor .. Jim PrPntice, for his ;ulvin· ;rncl
enthusiasm.
I owe a great deal to Ya.sushi Takahashi, for his fricn<lship during my yt>ars at
university, and for telling me to print my thesis single sided so that at least half of it.
would always be right.
I would like to thank my family for their constant support. low ancl c·rwo11ra~P
ment. Their faith in me never waivered. Finally, [ would like to thank Dav"< ;ilkinsou
who has stuck by me in one form or another. through all of this work.
ll
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The A RC CS Collaboration
fl. r\Hm·d1t. IL I. Cronstrom 1• H. Ehrli<:hmann. T. Hamacher. R. P. Hofmann.
T. Kirchlwff. :\.:\au. S. :\owak2• :\I. Reidenbach. R. Reiner. H. Schroder.
H. D. Schulz. :\.L Walter2• R. Wurth
DESY. Hamburg, Germany
IL D.:\ppuhn. C. Hast. H. Kolanoski. A. Lange. A. Lindner. R. :\.fankel.
>.I. Schieber. T. Siegmund. 8. Spaan. H. Thurn. D. Topfer. A. \\hither.
D. \Vegener
lnstitut fiir Physik3. Cniversitat Dortmund. Germany
:\I. Paulini. K. Reim. H. \Vegener
Phys1kali.-;chts lristitut 4• l"niursitat Erlangen-Niirnf.erg, Germany
R. :\Jundt. T. Oest. W. Schmidt-Parzefall
II. fn.-;t1tut fiir Experimentalphysik. Universitat Hamburg, Germany
W. Funk . .J. Stiewe, S. Werner
lristitut fiir Hochenc:rgiephysik5. Universitizt Heidelberg, Germany
K. Ehn·t. A. Hobcher. \V. Hofmann. A. Hupper, S. Khan. K. T. Knopfle .
.J. Spen~ler
Jfor-Planck-lnstitut fiir Kernphysik, Heidelberg, Germany
D. l. Britton6• C. E. K. Charlesworth7
• K. W. Edwards8, E. R. F. Hyatt6
,
H. Kapitza11• P. Krieger9 7
• D. B. :\.1acFarlane6, P. ~I. Patel6
• J. D. Prentice\
P.R. B. Saull6• S. C. Seidel7
• K. Tzamariudaki6, R. G. Van de \Vater7
•
T.-S. Yoon7
Institute of Particle Physics 1ry, Canada
D. Reiling. :\I. Schmidtler. M. Schneider. K. R. Schubert. K. Strahl. R. Waldi.
1 Support"d in pMt hy th" lnstitut" or Physics. Uruv.,nity or Lund. Sw"d"n
.: DESY. Inl z.,uth""
:l Support"d hy th" G.,rman BunJ.,sminist<!rium riir Fonchung und Technologi.,. und"r contract numb"r 0540051 P. 4
Support .. d by th" G .. rman Bundemin.ist.,rium Ciir Fonchung und T.,dino!ogi.,, und<!r contract numb"r 054ER12P. 5
Support""! by th" l~-rman Bundeminist.,rium riir Fonchung und Technologi.,. und<!r contract numb"r 055H02tP.
,; :l.kliill l "ruv.,nity. Montr<!al, Qu<!bK. Canada.
7' l '.ruv.,nity or Toronto. Toronto. Ontarin. Canada.
~Carleton llruv<!nity. Ottawa. Ontario. Canada.
~l Support.,.! in part by th<! Walt<!r C. Sumn<!r Foundation. 10 Support<!d by th<! Natural Scirnce and En~inttring R<!!!l<!arch Council, Canada.
lll
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S. \Veseler
lnstitut fiir Experimer.telle l\t"rnphysik 11• l"nirt'rsitiit l\ar/:;ruhe. Gt'T-mcny
G. Kernel. P. Kri:Zan. E. Krifoic. T. Podobnik. T. Zivko
/nstitut J. Stefan and Oddelek :a fi:iko 1z. l"nirer:a r ljubljani. Ljubljana.
Slot·enia
L. Jonsson
Institute of Physics 13, Cnit•ersity of l und . .'iu•f'drn
V. Balagura. I. Belyaev. :\I. Danilov. :\. Droutskoy. :\. Golutvin. l. t:'-1rdov.
G. Kostina. V. Lubimov. P. '.\lurat. P. Pakhlov. F. Ratnikov. S. St·nwnov.
V. Shibaev. V. Soloshenko. I. Tichomirov. Yu. Zaitst•v
Institute of Theoretical and Experimf'ntal Physic..- 14 •• \lo..-mw. Ru.->srn
11 Supported by the German Bundesministerium fiir ForschunK und T "dmoloKie, under r:ontrat:t number 054 KA 171'. 12 Supported by the Department of Science and Tedmoloio- of the Republic of Slav .. rua viii the lnter?14Uon"1r.s fiiir"
KfA. Jillich. 13 Supported by the Swedish Research Co•Jncil. 14 Supported in part by the lntemationa.1 Technol~y c.,nter BINITEC. !\.lov.ow. R1L,11ia.
IV
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