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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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