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We report the measurement of the Cabibbo-Kobayashi-Maskawa CP-violating angle? through a Dalitz plot analysis of neutral D meson decays to K{sub S}°??− and K{sub S}° K+K− produced in the processes B{sup {-+}} → DK{sup {-+}}, B{sup {-+}} → D* K{sup {-+}} with D* → D?°, D?, and B{sup {-+}} → DK*{sup {-+}} with K*{sup {-+}} → K{sub S}°?{sup {-+}}, using 468 million B{bar B} pairs collected by the BABAR detector at the PEP-II asymmetric-energy e+e− collider at SLAC. We measure? = (68 ± 14 ± 4 ± 3){sup o} (modulo 180{sup o}), where the first error is statistical, the second is the experimental systematic uncertainty and the third reflects the uncertainty in the description of the neutral D decay amplitudes. This result is inconsistent with? = 0 (no direct CP violation) with a significance of 3.5 standard deviations.
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.
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 has 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 whimsically 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 theconsistency of the Standard Model. The unitarity of the Kobayashi-Maskawa mixing matrix in
Using the entire sample of 467 million [Upsilon](4S) 2!B{bar B} decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC, we perform a 'GLW' analysis of B{sup ±} 2!D{sup ±} decays, using decay modes in which the neutral D meson decays to either CP-eigenstates or non-CP-eigenstates. We measure the partial decay rate charge asymmetries for CP-even and CP-odd D final states to be A{sub CP+} = 0.25 ± 0.06 ± 0.02 and A{sub CP-} = -0.09 ± 0.07 ± 0.02, respectively, where the first error is the statistical and the second is the systematic uncertainty. The parameter A{sub CP+} is different from zero with a significance of 3.6 standard deviations, constituting evidence for direct CP violation. We also measure the ratios of the charged-averaged B partial decay rates in CP and non-CP decays, R{sub CP+} = 1.18 ± 0.09 ± 0.05 and R{sub CP-} = 1.07 {+-} 0.08 {+-} 0.04. We infer frequentist confidence intervals for the angle [gamma] of the (db) unitarity triangle, for the strong phase difference [delta]{sub B}, and for the amplitude ratio r{sub B}, which are related to the B− 2!D− decay amplitude by r{sub B}e{sup i({delta}{sub b-[gamma]})} = A(B− 2!{bar D}°K−)/A(B− 2!D°K°−). Including statistical and systematic uncertainties, they obtain 0.24
We report recent CDF results on CP violation in B− → DK− modes, where D goes to Cabibbo suppressed (??, KK) or doubly cabibbo suppressed (K?−) modes, which are related to CKM angle gamma. We also describe direct CP violation measurements in charmless two-body decays of B{sub s}° → K? and?{sub b}° → pK, p? modes, which are unique to the CDF experiment. We also report on CP violation measurements in D° → h+h− modes.
This dissertation describes a measurement of the direct CP asymmetry between inclusive b {yields} s{gamma} and {bar b} {yields} {bar s}{gamma} decays. This asymmetry is expected to be less than 0.01 in the Standard Model, but could be enhanced up to the order of 0.10 by non-Standard Model contributions. We use a sample of 89 million B{bar B} pairs recorded with the BABAR detector at PEP-II, from which we reconstruct a set of 12 exclusive b {yields} s{gamma} final states containing one charged or neutral kaon and one to three pions. We measure an asymmetry of A{sub CP} (b {yields} s{gamma}) = 0.025 {+-} 0.050(stat.) {+-} 0.015(syst.), corresponding to an allowed range of -0.06