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Thesis De La Thèse Soumise Au Submitted for Microfilming National Library Bibliothèque nationale 1+1 of Canada du Canada Acquisitions and Direction des acquisilion~ et Bibliographie services Branch des services bibliographiques 395 Wellington $treel 395. rue Wellington Ottawa. Onlano Ottawa (Onlario) K1AON4 K1AON4 NOTICE AVIS The quality of this microform is La qualité de cette microforme heavily dependent upon the dépend grandement de la qL'alité quality of the original thesis de la thèse soumise au submitted for microfilming. microfilmage. Nous avons tout Every effort has been made to fait pour assurer une qualité ensure the highest quality of supérieure de reproduction. reproduction possible. If pages are missing, contact the S'il manque des pages, veuillez university which granted the communiquer avec l'université degree. qui a conféré le grade. Sorne pages may have indistinct La qualité d'impression de print especially if the original certaines pages peut laisser à pages were typed with a poor désirer, surtout si les pages typewriter ribbon or if the originales ont été university sent us an inferior dactylographiées à l'aide d'un photocopy. ruban usé ou si l'université nous a fait parvenir une photocopie de qualité inférieure. Reproduction in full or in part of La reproduction, même partielle, this microform is governed by de cette microforme est soumise the Canadian Copyright Act, à la Loi canadienne sur le droit R.S.C. 1970, c. C·30, and d'auteur, SRC 1970, c. C·30, et subsequent amendments. ses amendements subséquents. Canada • Hard Diffractive Scattering in Photoproduction at HERA Laurel E. Sinclair Dcpart.mellt. of Physics McGill Universit.y, Montreal Novclllber, 1995 A t.hesi" slll>llIit.t.ed t.o !.he Fil,,"I!.y of Gradua!.,' St.lIdi,," alld Hl'"'al',,h in par!.ial fulfilmcn!. of !.he requirclllen!." of t.he dcgl'"e of Doc!.or of Philosophy @Lllurcl E. Sinclair 1995 • National Library Bibliothèque nationale .+. olCanada du Canada Acquisitions and Direction des acquisitions et Bibliographie Services Branch des services bibliographiques 395 Wellington Street 395. rue Wellington Ottawa. Ontario Onawa (Onlario) K1AON4 K1AON4 The author has granted an L'auteur a accordé une licence irrevocable non-exclusive licence irrévocable et non exclusive allowing the National Library of permettant à la Bibliothèque Canada to reproduce, loan, nationale du Canada de distribute or sell copies of reproduire, prêter, distribuer ou his/her thesis by any means and vendre des copies de sa thèse in any form or format, making de quelque manière et sous this thesis available to interested quelque forme que ce soit pour persons. mettre des exemplaires de cette thèse à la disposition des personnes intéressées. The author retains ownership of L'auteur conserve la propriété du the copyright in his/her thesis. droit d'auteur qui protège sa Neither the thesis nor substantial thèse. Ni la thèse ni des extraits extracts from it may be printed or substantiels de celle-ci ne otherwise reproduced without doivent être imprimés ou his/her permission. autrement reproduits sans son autorisation. ISBN 0-612-12486-X Canada '" Abstract • 1'!aot(Jprodlid iOIl (~vcnt.s which have: l.wo or Inor.;! jets have becn studied in the W.". l'alll\'' 1:1" C;"V <' W.Il, < 280 G"V with the ZEUS dctcclol' at I-IERA. Il c1iL" of ''l'''"ls is obs"l'\'ed with lil.ll" hadrollic activity betweeh the jet.s. Th" jds a'" ",.parat.erl by ps,,"dorapidity illt.cl'vals (t.'Il of up ta four unit.s alld haVI> Il'aIlS\'''l'se CIl"l'gi"s gl'''ill.''l' t.han 6 GeV. A gap is defined as t.he ahsclI<:e hdw""" t.he jds of part.icl"s wit.h tmnsvcrse energy greater than :!OO McV. 'l'he fractioll of ev,,"t.s cOlltailling a gap is measuœd as a function of t.,/. Il rleel'CiL,eS eXl'ollclltially as expect.ed fol' processes in which colour is cxehallgl>d hct,wccli I.he jets, IIp to a valuc of t.,/ - 3, t.hclI reachcs il constallt. val III' or aholll. 0.1. Tlw ('Xn'ss ahove Il)(' (·XIH.)Ilellt.iiti fall-ofr C(\.!I lU' ill1.('rIH·d,(~d il:-- t'\'id(~IIC(~ for !Ii1rd St·ilU.I.·l'ill~ via il sl.rollgly illl,(·racl.ill~ ('oJulil sillp,ld ohjerl. Résumé Des événc""'"ts de photoprodnct,ion ayant deux jets ou plus ont été étudiés dalls l'illtervalle de la variable W~p, 135 GeV < W~p < 280 GeV, avec le détect.eur ZI;;US à I-IER.A. On observe une classe d'événements ayant peu d'activit.<i hildl'Onique entre les jds. Les jets sont, séparés par des intervalles jnsqn'à quat.res unités de pseudorapidité (t.'Il ct ont des énergies transverses de plus de fi GeV. Un gap est. défini comme une absence de l'articles ayant des énergics t.mnsverses supérieures a 300 MeV entre les jets. La fraction d'événement.s possèdant un gap est, mesurée en fonction de /::"'1. Elle décroit de façon exponentielle t.e1le que prévue l'OUI' les processus où à lieu l'échange de coul"UI' ""1,1''' les jets, jusqu'it nlll, valenr de t.1/ - :l, pOUl' ensnit.e prcndn' Ulle valeuI" const.a.nt.e d'ellviron 0,1. L'cxc<~s f.tu-dclil. dc la. chute expollellt.idl,· pcut. ôt.re illl,"rprélé comnle IIne illdicill.ioll d'ull prOCl'$SIlS d'échallge dirrnll:lir dur de singuld dc couleur. • • • • Preface My expericllœs over t.h" past. five years of beiug a member of the ZEUS collaborat.ioll have been t.relllendously rewarding. 1have had the opportunity t.o work wit.h talellted and illt.eresting people and 1 have learned many things. This dissert"tioll deals with work which was performed almost entirely during 1!l!J5. How"v"r my work and experiellces during the preceding four years can uot. 1", uegleded. During t.hal. tillle 1 lea.rned about the ZEUS deteetor, about. high ellergy physics analysis, abont photoproduetion and jet physics, and abont. how 1.0 work in collaboration with over '100 other people. Contribut.ions 1.0 the ZEUS Experiment 1 first. l.ravdl"d 1.0 Hambmg t.o work wit.h the ZI~US experim('lIt ill li... rail of WHO. My snpervisol' had ,1ITaliged t.lmt. 1 shonld st.udy t.he clfecl or 1.1 ... magnct.ic field 011 t.he l'esponse or the phot.olllult.iplier t.ubes used to l'eadOllt l.he calorim"ter. Thel'e was a small prototype calorimeter set up in one of t.he t.esl. !>cam al'eas on the DESY site which couId be inserted into the magnetic field of either a dipole or a solenoidal magnet. Stefan 'Bruehl had been working on this project under the guidance of Francois Corriveau for several mon\.hs already and was of great assistance in the data acquisition. 1 analyzed l.he data. at McGill wil.h the advice of Francois Corriveau. This information is now used in the calibration of the calorimeter readout. 1 moved 1.0 Hambl1l'g in the l'ail of 1991. Thl'ough the advice of my super­ visor 1 became involved with the main ZEUS calorimeter group by writing v • \'\ l'III'TII '/.' SOIlle sOrt,\\'iHt' code for h(\lIdlill~ t.llt' l·tTOr~ l'l'. lll"llt'd dl1rill~ t hl' cahHoilllt,­ ter calihratioll, Maria Hoco had writ.lell t\l(' !'\llli il"" which IIl1packl'd 1h,' • calibration '-°on:üa.nts, dtlIl1IWd tilt' l'lTor rode:-; illto Cl Iih· ilnd rallt'd t1\Y n)\l­ tine. She Wêl~ of great a~sist.al:Ct' t.u IlH' ill. t.hal. tinlt'. 1 ëll:-oo clHlt.rihll1.t'd ttl the c"lori\lll'1l'r grolll' by .loi IIg roll t. iIll' sh ifts t.o 111011 itOI' t.ll(' '111,,1 it.y of t. h,' calorimeter data duri\lg Iml! allli Iml2, During the \·IER.A rtI\llling periods III 1992 alld 1993 1 was ail "onlilh' expert.". This meant that for four days of every month 1 actual1y gol. 1.0 click the but.l.ons that tell ZEUS 1.0 take data, or not, and with what trigger algorithm, c\;cctera. Thal. was greal. fun. II. was Sampa Bhadra who suggested 1 should bccomc an online expert. Of comse l,he ,.",,[ online experts were t.ll(' people like I\al.sllo Tokushllkll. Chris YoulIgmall and Viviell O'Dell who klll'w ail of t.he illl.ricacies of the sYSI."1I1 aI\(l were dist.Ilr1ll'd hy illY pholll' cal1s ill t.he llIiddle 01' t.he lIighl. wh,," I.h,· IlIlllillosity was high, alld t.hillgs \V<'I'(' !',Oill,1!, terribly wrollg. Also in 199:3 1 began to I,hillk more about the dat" that wc Wère takill!', with ZEUS. 1 had been "dvised by my supervisol' 1.0 become a membel' of th" hard photopl'Oduction wOI'king group. 1 took on the responsibility of writing and maiul.aillillg the thinl level t,rigger filter code fol' this group. 1 Il1ld 1.0 evaluate the efliciencies of the first, second and third levels of triggerinlZ; and 1.0 ensure that the output rate l'rom the third level trigger through the hard photoproduction filter code was not 1.00 high. R.osario Nania was the leader of this group and gave me helpful advice. In fact the main ideas fol' each of the algorithms we used Came l'rom people who had been actively involved in physics analysis in the previous years, in particular ,Juan Terron, Claudia G1asman, Klaus Desch, Uri Karshon and Leonid Gladilin.
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