Heavy-Quark Physics and Cp Violation

COURSE HEAVYQUARK PHYSICS AND CP VIOLATION Jerey D Richman University of California y Santa Barbara California USA y Email richmancharmphysicsucsbedu c Elsevier Science BV Al l rights reserved Photograph of Lecturer Contents Intro duction Roadmap and Overview of Bottom and Charm Physics Intro duction to the Cabibb oKobayashiMaskawa Matrix and a First Lo ok at CP Violation Exp erimental Challenges and Approaches in HeavyQuark Physics Historical Persp ective Bumps in the Road and Lessons in Data Analysis Avery short history of heavyquark physics Bumps in the road case studies Some rules for data analysis Leptonic Decays Intro duction to leptonic decays Measurements of leptonic decays Lattice calculations of leptonic decay constants Semileptonic Decays Intro duction to semileptonic decays Dynamics of semileptonic decay Heavy quark eective theory and semileptonic decays Inclusive semileptonic decay and jV j cb Leptonendp oint region in semileptonic B deca y and jV j ub Form factors and kinematic distributions for exclusive semileptonic decay HQET predictions and the IsgurWise function Exclusive semileptonic decay jV j and jV j cb ub Hadronic Decays Lifetimes and Rare Decays Hadronic Decays Lifetimes Rare decays CP Violation and Oscillations Intro duction to CP violation CP violation and cosmology CP violation in decay direct CP violation CP violation in mixing indirect CP violation Phenomenology of mixing CP violation due to interference b etween mixing and decay Acknowledgements App endix Remarks on Hadronic Currents Form Factors and Decay Constants App endix Remarks on CP Conjugate Amplitudes References Intro duction I am delighted to present these lectures on the physics of charm and b ottom hadrons to this enthusiastic group of graduate students and p ostdo cs here in Les Houches Whyisheavyquark physics interesting I hop e to show you that we can now address an extraordinarily broad range of issues ranging from the mysteries of the Cabibb oKobayashi Maskawa CKM quark mixing matrix to the dynamics of the strong and weak interactions to fascinating rare pro cesses that are sensitive to physics beyond the standard mo del In the near future several new and ongoing exp eriments will address the driving question of this eld what is the origin of CP violation So far CP violation has b een observed only as a tiny partinathousand eect in kaon decays There is as yet very little empirical evidence to establish that physics within the framework of the standard mo delnamely the phase structure of the CKM matrixis resp onsible If the CKM matrix is indeed the source then we will observe large CP violating asymmetries in b oth B and B meson decays If the exp ected pattern of CP violation is s not observed then these investigations will provide a windowinto new physics beyond the standard mo del I was more than a little surprised to discov er that nearly all of the memb ers of this audience are theorists This fact is b oth intriguing and a little daunting I have the opp ortunity to explain the challenges and excitement of building exp eriments and p erforming new measurements At the same time there is a risk that I will bore you with to o many exp erimental details or fail to motivate them suciently For some of you learning how measurements are p erformed may b e something like learning how your sausages are madeyou would rather not know I hop e that by the end of these lectures you will at least conclude that the sausages we make are kosher between theory and exp eriment in heavyquark The interaction physics has been extremely pro ductive and I will devote a signi cant part of these lectures to a review of theoretical progress from the perspective of an exp erimentalist I will discuss theory at a fairly simple level mainly to obtain insights into the key physical ideas and J D Richman to help explain the phenomenology that app ears in exp erimental mea surements For discussions of the more technical theoretical issues I refer you to the lectures of other sp eakers at this scho ol for example Buras Manohar Martinelli and Wise Exp erimentalists need to know ab out theory for several reasons First in planning an incisive and coherent set of measurements it helps greatly to understand the theoretical issues It is also imp ortant to have a sense of how reliable the predictions are and to know the key assumptions that are really being tested In p erforming a mea surement one m ust understand all of the kinematic distributions that describ e the pro cesses under study since both the detection eciency and the ability to reject backgrounds dep end on knowledge of such distributions Similarly theorists should have some knowledge of the strengths and weaknesses of dierent exp eriments as well as a sense of which kinds of measurements are practical and which are not It is also imp ortantfor theorists to b e aware of assumptions that exp erimentalists make and to understand the dep endence of the measurements on these assumptions A measured branching fraction for example may well dep end either on a mo del for the decay distributions for the signal or on a mo del de scribing the background comp osition For phenomenologists esp ecially it is imp ortant to b e able to communicate with exp erimentalists since predictions that are not clearly stated may simply b e ignored These lectures are unashamedly p edagogical so I will not aim for the level of impartiality that is customary in a review talk or article I hav e made some recent attempts at such reviews My own work in heavyquark physics has b een mainly on the CLEO exp eriment al though more recently I have b een involved in the construction of the BaBar detector Many of my examples are from CLEO analyses b oth b ecause I am most familiar with them and b ecause CLEO results are often as good as those from other exp eriments When other measure ments are b etter than those of CLEO however I will fo cus on them esp ecially to show the advantages of dierent metho ds My goal then is to present a balanced and coheren t picture of b oth exp eriment and theory The p edagogical approachgives me more free dom to be selective to sp end more time than usual on simple physics arguments and to present some of myown opinions ab out the strengths and weaknesses of various measurements In the pro cess I hop e b oth to giveyou a picture of howheavyavor physics is done and to convey my enthusiasm for this eld I am happy to say that these lectures are destined to become out HeavyQuark Physics and CP Violation ofdate in the relatively near future as exp eriments provide us with a vast amount of new data We can therefore exp ect ma jor advances in nearly all areas of bottom and charm quark physics and we need young p eople likeyou to help explore this new territory Roadmap and Overview of Bottom and Charm Physics The physics of b ottom and charm hadrons is a broad sub ject and it is useful to begin with a roadmap of the main topics and physics issues Here is an outline of the lectures Intro duction to the CKM matrix Exp erimental c hallenges of b and c physics Historical p ersp ective bumps in the road and lessons in data anal ysis Leptonic decays of pseudoscalar mesons Semileptonic decays and measurements of CKM elements Hadronic decays lifetimes and rare decays CP violation and oscillations All of the physical pro cesses that I discuss involve underlying weak pro cesses mediated by the W b oson but strong and even electromag netic interactions play a crucial role as well The thread that runs through these lectures ties all of these sub jects to the quest to under stand CP violation Although this list is rather long it is far from complete For exam ple I will say very little ab out baryons apart from lifetime measure ments or ab out sp ectroscopy The physics of heavyquark pro duction including Z bb and other related electroweak phenomena such as the b forwardbackward asymmetry is entirely absent these topics could easily b e the sub ject of another series of lectures I b egin in Section with a short intro duction to the CKM matrix and a review of its present status Because m m the b quark must b t decay into quarks outside its own generation As a consequence even b c decay mo des are suppressed by jV j the dominant cb resulting in the long lifetimes of b hadrons of order ps In some exp eriments these long lifetimes have made distinguishing b hadrons from backgrounds much easier since separated decay vertices are ev ident if the b hadron is moving rapidly B decays provide various ern the strengths of b c ways to measure jV j and jV j which gov cb ub and b u transitions Furthermore the app earance of the t quark in virtual intermediate states of B and B mixing and p enguin decay s J D Richman pro cesses allows one to extract jV j and jV j We will also see that td ts phases of the CKM elements not just their magnitudes are exp eri mentally accessible and are asso ciated with CP violating asymmetries For reasons that I will discuss the determination of CKM elements is less imp ortant in charm physics Although jV j and jV j can be de cs cd termined from charm semileptonic decays the main fo cus has been to infer these quantities from unitarity of the CKM matrix and then to use measured branching fractions to test theoretical predictions for the absolute scale of the decay rates Section describ es the main challenges confronting exp eriments that study b ottom and charmquark physics I compare the strengths and weaknesses

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