

 07 Aug 1995

UCSB-HEP-95-08 Stanford-HEP-95-01

Leptonic and Semileptonic Decays of Charm and Bottom Hadrons

Jeffrey D. Richman Department of Physics, University of California, Santa Barbara, CA 93106 richman@charm.physics.ucsb.edu

Patricia R. Burchat Department of Physics, Stanford University, Stanford, CA 94305 pat@slac.stanford.edu

Abstract We review the experimental measurements and theoretical descriptions of leptonic and semileptonic decays of particles containing a single heavy quark, either charm or bottom. Measurements of bottom semileptonic decays are used to determine the magnitudes of two fundamental parameters of the standard model, the Cabibbo-Kobayashi-Maskawa matrix elements Vcb and Vub. These parameters are connected with the physics of quark flavor and mass, and they have important implications for the breakdown of CP symmetry. To extract precise values of jVcbj and jVubj from measurements, however, requires a good understanding of the decay dynamics. Measurements of both charm and bottom decay distributions provide information on the interactions governing these processes. The underlying weak transition in each case is relatively simple, but the strong interactions that bind the quarks into hadrons introduce complications. We also discuss new theoretical approaches, especially heavy-quark effective theory and lattice QCD, which are providing insights and predictions now being tested by experiment. An international effort at many laboratories will rapidly advance knowledge of this physics during the next decade. This file contains only the abstract and the table of contents. The full document is at the URL http://charm.physics.ucsb.edu/papers/slrevtex.ps and contains 168 pages and 47 figures.

To be published in Reviews of Modern Physics.

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CONTENTS

I. Introduction and Overview 4

A. Semileptonic Decays and the Cabibbo-Kobayashi-Maskawa (CKM) Matrix 6 B. Decay Dynamics and Heavy Quark Effective Theory 8 C. Plan of the Review 10 II. Theory of Leptonic and Semileptonic Decays 11

A. Matrix Elements for Leptonic and Semileptonic Decays 11 B. The Cabibbo-Kobayashi-Maskawa Matrix 12 C. Dynamics of Semileptonic Decays 17 III. General Remarks on Experimental Techniques 27

A. Charm Hadron Experiments 27 B. Bottom Hadron Experiments 30 C. Lepton Identification 33 D. Assumed Branching Fractions 34 IV. Leptonic Decays 34

A. Theory of Leptonic Decays 34 B. Experimental Results on Leptonic Decays 37

1. D+ and Ds Leptonic Decays 37 2. B\Gamma Leptonic Decays 42 V. Inclusive Semileptonic Decays 42

A. Introduction 42 B. Theoretical Predictions for Semileptonic Decays 44 C. Inclusive Charm Semileptonic Decays 50 D. Inclusive Bottom Semileptonic Decays and jVcbj 54

1. Measurement of BSL Using the Inclusive Lepton Spectrum 55 2. Measurement of BSL Using Charge and Angular Correlations in Dilepton Events 59 3. Measurement of BSL for B0 and B\Gamma with Tagging 61 4. Determination of jVcbj from Inclusive Measurements 63 E. Lepton Endpoint Region in Semileptonic B Decays and Determination of jVubj 64 F. B ! Xo/ \Gamma *o/ and Other Inclusive Modes 69 VI. Exclusive Semileptonic Decays 70

A. Theory of Exclusive Semileptonic Decays of Mesons 72

1. Structure of Hadronic Currents 73 2. Quark Models 74 3. Heavy Quark Effective Theory 77 4. Predictions for the Slope of the Isgur-Wise Function 82 5. Decay Distributions for P ! P 0`* 83 6. Decay Distributions for P ! V `* 84 B. Cabibbo-Favored Semileptonic Decays of Charm Mesons 89

1. D ! K`+* 89 2. D ! K

\Lambda `+* 93

3. Ratio of \Gamma (D ! K

\Lambda `+*) to \Gamma (D ! K`+*) 100

4. D decays to other Cabibbo-favored states 102 5. Ds ! OE`+* 102 6. Ds ! j`+* and Ds ! j0`+* 103 C. Cabibbo-Suppressed Semileptonic Decays of Charm Mesons 105 D. Summary of Exclusive Charm Decays 106 E. Exclusive b ! c Semileptonic Decays of B Mesons and jVcbj 106

1. Overview and Experimental Techniques 106 2. Branching Fraction for B ! D`\Gamma * 110 3. Branching Fractions for B ! D\Lambda `\Gamma * and B ! D\Lambda \Lambda `\Gamma * 113 4. The Determination of jVcbj with Exclusive Decays 121 5. Measurement of the B ! D\Lambda `\Gamma * Form Factors 128 F. Exclusive b ! u Semileptonic Decays of Bottom Mesons and jVubj 133 G. Semileptonic Decays of Charm and Bottom Baryons 144

1. Decay Distributions for \Lambda c ! \Lambda `+* 144 2. Charm Baryon Decays 146 3. Bottom Baryon Decays 148 VII. Conclusions 149

A. CKM Measurements 149 B. Summary of Leptonic and Semileptonic Charm Decays 153

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C. B Semileptonic Branching Fractions 155 D. Form Factors for B Semileptonic Decays 157 Acknowledgments 158 References 158

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