The average b-hadron lifetime has been measured using a high statistics sample of B → J/?X decays recorded with the Collider Detector at Fermilab. The decay vertices of J/? →??− candidates have been reconstructed using information from a silicon vertex-detector. The measured B lifetime, which is the average over all b-hadrons produced in p{bar p} collisions at √s = 1.8 TeV, weighted by their branching ratios into J/? is:?B = 1.46 ± 0.06(stat.) ± 0.06(sys.)ps (preliminary); In addition we used the fully reconstructed final states B{sup ±} → J/?K{sup ±} and B° → J/?K°* to measure the exclusive lifetime of charged and neutral B-mesons. We measure:?{sub B}{sup ±} = 1.59 ± 0.27(stat.) ± 0.17(sys.) ps (preliminary);?{sub B}° = 1. 34 ± 0.31 (stat.) {plus_minus} 0.17 (sys.) ps (preliminary); From this we obtain the following result for the lifetime ratio:?{sub B}{sup {plus_minus}}/? {sub B}° = 1.19 {plus_minus} 0.35(stat.) {plus_minus} 0.12(sys.) (preliminary); This represents the first measurements of the b-lifetime at a hadron collider.
Lifetime measurements for B0 and B+ are presented using semileptonic decays of B mesons from 360 pb-1 of data collected by CDF's lepton plus displaced track trigger. The decays B 2!l[nu]DX, where D is either D +, D0, or D* +, are partially reconstructed from a muon or electron, a displaced track, and a fully reconstructed charm meson. The B 0 and B+ lifetimes are obtained from an unbinned maximum-likelihood fit to the proper decay length distributions. The measured lifetimes are [tau]B 0 = 1.527 ± 0.012(stat.) ± 0.023(syst.)ps and [tau]B + = 1.629 ± 0.013(stat.) ± 0.025(syst.)ps.
This 2nd edition is an extensive update of "B Decays?. The revisions are necessary because of the extensive amount of new data and new theoretical ideas. This book reviews what is known about b-quark decays and also looks at what can be learned in the future.The importance of this research area is increasing, as evidenced by the approval of the luminosity upgrade for CESR and the asymmetric B factories at SLAC and KEK, and the possibility of experiments at hadron colliders.The key experimental observations made thus far, measurement of the lifetimes of the different B species, B0-B0 mixing, the discovery of ?Penguin? mediated decays, and the extraction of the CKM matrix elements Vub and Vcb from semileptonic decays, as well as more mundane results, are described in great detail by the experimentalists who have been closely involved with making the measurements. Theoretical progress in understanding b-quark decays using HQET and lattice gauge techniques are described by theorists who have developed and used these techniques.Synthesizing the experimental and theoretical information, several articles discuss the implications for the ?Standard Model? and how further tests can be done using measurements of CP violation in the B system.
Two measurements of the lifetime of neutral and charged B mesons in p{bar p} collisions at √s = 1.8 TeV by the CDF experiment are presented. The first relies on the study of exclusive decays of the type B → [psi] K, the second on semileptonic decays of a B meson into a D° or a D. The combined results are [tau](B+) = 1.62 ± 0.09 ps, [tau](B0) = 1.60 ± 0.09 ps and [tau](B+)/[tau](B°) = 1.00 ± 0.07.
Two measurements of the lifetime of neutral and charged B mesons in p[bar p] collisions at[radical]s= 1.8 TeV by the CDF experiment are presented. The first relies on the study of exclusive decays of the type B[yields][psi] K, the second on semileptonic decays of a B meson into a D[degrees] or a D. The combined results are[tau](B[sup+])= 1.62[+-] 0.09 ps, [tau](B[sub 0])= 1.60[+-] 0.09 ps and[tau](B[sup+])/[tau](B[sup 0])= 1.00[+-] 0.07.
For the eighth Advanced Study Institute (ASI) on Techniques and Concepts of High-Energy Physics we returned once again to the Hotel on the Cay on that speck of land in the harbor of Christiansted, St. Croix, U. S. Virgin Islands. This time, the ASI brought together a total of 73 participants, from 21 countries. The primary support for the meeting was provided, as usual, by the Scientific Affairs Division of the North Atlantic Treaty Organization (NATO). The ASI was cosponsored by the U. S. Department of Energy, by the Fermi National Accelerator Laboratory (Fermilab), by the U. S. National Science Foundation, and by the University of Rochester. A special contribution from the Oliver S. and Jennie R. Donaldson Charitable Trust provided an important degree of flexibility, as well as support for worthy students from developing countries. In addition, the International Science Foundation contributed very generously to the support of a participant from Russia. As in the case of the previous ASls, the scientific program was designed for advanced graduate students and recent PhD recipients in experimental particle physics. The present volume of lectures, although, unfortunately, short of three contributions, should complement the material published in the first seven ASIs, and prove to be of value to a wider audience of physicists. It is a pleasure to acknowledge the encouragement and support that I have continued to receive from colleagues and friends in organizing this meeting.
CP violation is one of the most subtle effects in the Standard Model of particle physics and may be the first clue to the physics that lies beyond. Charge conjugation, C, and parity, P, are symmetries of particle interactions. C corresponds to the operation of replacing a particle by its antiparticle, while P is the operation of mirror reflection. Before 1956, it was believed that these were also symmetries of the interactions of elementary particles. In 1956, C S Wu found evidence for P violation in the weak interaction. Theorists proposed that the combination of CP would be a symmetry of the weak interaction. In 1964, Christenson, Cronin, Fitch and Turlay found the first evidence for the violation of CP symmetry in the decays of kaons.Although Kobayashi and Maskawa then showed how the Standard Model can accommodate the observed CP violation, Wolfenstein pointed out that it is also possible that there is a new interaction in addition to the usual four, called the superweak interaction, which is responsible for the asymmetry. To test this idea, the observation of a different type of asymmetry, called direct CP violation, is required; in the kaon sector, very precise measurements of the ratio of kaon decay rates are necessary. In B decay modes where a second order weak process whimisically named “penguin” interferes with another suppressed, first order “tree” amplitude, it may also be possible to observe these direct CP-violating effects.B physics and CP violation is now one of the major growth areas in high energy physics. Nearly every major high energy physics laboratory now has a project underway to observe the large CP asymmetries expected in the B sector and to test the consistency of the Standard Model. The unitarity of the Kobayashi-Maskawa mixing matrix in the Standard Model implies the existence of three phases, called alpha, beta and gamma, which can be determined by the measurements of CP asymmetries in B decays. About 200 participants gathered in Hawaii in March 1997 to discuss the progress in the field, and this important book constitutes the proceedings of that conference.
