Measurements and searches for rare B decays have been performed with the BaBar detector at the PEP-II ee− asymmetric B Factory, operating at the [Upsilon](4S) resonance. The authors report some recent branching fraction measurements on hadronic and radiative B decays, occurring from b --> s/d and b --> u transitions. Most of the results presented here are based on a data sample corresponding to a luminosity of 81.9 fb−1.

We present the results of searches for rare B meson decays. The measurements use all or part of a data sample of about 88 million[Upsilon](4S)[yields] B[bar B] decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric energy B Factory at the Stanford Linear Accelerator Center. We study a variety of decays dominated by electromagnetic, electroweak and gluonic penguin transitions, and report measurements of branching fractions.

Measurements and searches for rare B decays have been performed with the BaBar detector at the PEP-II e[sup +]e[sup -] asymmetric B Factory, operating at the [Upsilon](4S) resonance. The authors report some recent branching fraction measurements on hadronic and radiative B decays, occurring from b --> s/d and b --> u transitions. Most of the results presented here are based on a data sample corresponding to a luminosity of 81.9 fb[sup -1].

The search for rare B decays and direct CF violation at BABAR is described. The following measurements (based on integrated luminosities ranging from 56.4 to 81.9 fb[sup -1]) are summarized: the inclusive branching fractions and direct CF asymmetries of B[sup+][yields] h[sup+]h[sup -]H[sup+] (h=[pi], K), the exclusive branching fractions of B[sup+][yields] K[sup+][pi][sup -][pi][sup+] (where significant signals are observed in the B[sup+][yields] K*[sup 0](892)[pi][sup+], B[sup+][yields] f[sub 0](98)K[sup+], B[sup+][yields][chi][sub c0]K[sup+], B[sup+][yields][bar D][sup 0][pi][sup+] and B[sup+][yields] higher K*[sup 0][pi][sup+] channels), the branching fractions of B[sup+][yields][rho][sup 0][rho][sup+] and B[sup+][yields][rho][sup 0] K*[sup+], and finally, the branching fractions, the longitudinal components, and the direct CF asymmetries in B[yields][phi]K*.

We present results from BaBar experiment for the measurement of inclusive and exclusive branching fractions of B mesons into final states containing J/[psi], [psi](2S) and[chi]c. The contributions of CP even and odd amplitudes in the decay B[sup 0][yields] J/[psi]K*[sup 0] are determined from an angular analysis. We report the measurements of the branching ratios B[sup 0][yields] D*[sup+] D*[sup -] and D*[sup+] D*[sup -] K[sub S][sup 0], and the study of exclusive two-body and quasi-two-body charmless decays. The branching fraction of the decay B[sup 0][yields] K*[sup 0][gamma] has been determined and the corresponding CP asymmetry has been measured.

The PEP-II and KEK asymmetric B factories are providing the BaBar and BELLE collaborations large samples of B mesons, enabling high-statistics searches for rare B decays. The rates for some of these decays can be enhanced by contributions from new physics, while others can provide constraints on the Unitarity Triangle. The author reviews a variety of recent results on rare B decays from these two experiments.

We report recent measurements of rare charmless B decays performed by BaBar. The results are based on the final BaBar dataset of 424 fb−1 collected at the PEP-II B-factory based at the SLAC National Accelerator Laboratory. The study of rare B decays is a key ingredient to meet two of the main goals of the B-factories: assessing the validity of the Cabibbo-Kobayashi-Maskawa (CKM) picture of CP-violation by precisely measuring the elements of the Unitarity Triangle (UT), and searching for hints of New Physics (NP), or otherwise constraining NP scenarios, in processes which are suppressed in the Standard Model (SM). In loop processes, in particular, NP at some higher energy scale may manifest itself in the low energy effective theory as new couplings, such as those introduced by new very massive virtual particles in the loop. In NP searches hadronic uncertainties can play a major role, expecially for branching fraction measurements. Many theoretical uncertainties cancel in ratios of amplitudes, and most NP probes are therefore of this kind. In the following sections we report recent measurements, performed by the BaBar Collaboration, that are relevant to NP searches in charmless hadronic B decays.