This document presents results of the search for B + → etaXK+ in which etaX → etapi+pi - or etaX → K0S K+pi-, and etaX is a potentially exotic state with a resonant mass within (1.2-1.8) GeV. We use the BABAR data of 382.9 million BB pairs and report the first observation of B+ → eta(1295) K+ and B+ → eta(1475)K+, and set upper limits for the modes listed below. We also consider an alternative signal model in the etaX → K0S K+/-pi∓ mode with an extra resonance, to better describe the meson mass spectrum. We provide the central values where possible. Hermitian conjugation is implied throughout the document unless stated otherwise. BB+/- →h1295 K+/- xBh 1295→h pp=2.93+0.77+0.22 -0.73-0.21 ˙10-6, BB+/- →h1475 K+/- xBh 1475→ KK&d1;p =13.79+1.83+1.00-1.65-0.56 ˙10-6. The following upper limits assume 90% C.L: BB+/- →f11285 K+/-xB f11285 →hpp

This thesis describes the analyses of the rare charmless hadronic B meson decays B[sup 0] [yields] [phi]K[sup 0] and B[sup 0] [yields] K*[sup +][pi][sup -], using 20.58 fb[sup -1] of e[sup +]e[sup -] data taken at the [Upsilon](4S) resonance. The data were taken with the BABAR detector during its first run at the PEP-II asymmetric e[sup +]e[sup -] collider. Measurements of these modes using a counting technique are presented with the branching fractions [Beta](B[sup 0] [yields] [phi]K[sup 0]) = (9.3 [+-] 3.4(stat.) [+-] 1.1(syst.)) x 10[sup -6] with a significance of 4.9[sigma], and [Beta](B[sup 0] [yields] K*[sup +][pi][sup -]) = (20.8 [+-] 9.3(stat.) [+-] 2.1(syst.)) x 10[sup -6] with a significance of 3.0[sigma]. For the latter, an upper limit of [Beta](B[sup 0] [yields] K*[sup +][pi][sup -])

Rare charmless hadronic B decays are particularly interesting because of their importance in understanding the CP violation, which is essential to explain the matter-antimatter asymmetry in our universe, and of their roles in testing the ''effective'' theory of B physics. The study has been done with the BABAR experiment, which is mainly designed for the study of CP violation in the decays of neutral B mesons, and secondarily for rare processes that become accessible with the high luminosity of the PEP-II B Factory. In a sample of 89 million produced B{bar B} pairs on the BABAR experiment, we observed the decays B{sup 0} {yields} {omega}K{sup 0} and B{sup +} {yields} {omega}{rho}{sup +} for the first time, made more precise measurements for B{sup +} {yields} {omega}h{sup +} and reported tighter upper limits for B {yields} {omega}K* and B{sup 0} {yields} {omega}{rho}{sup 0}.

The authors present a search for B decays to charmless final states involving charged or neutral a[sub 0] mesons. The data sample corresponds to 89 million B[bar B] pairs collected with the BABAR detector operating at the PEP-II asymmetric-energy B Factory at SLAC. They find no significant signals and determine the following 90% C.L. upper limits: [Beta](B[sup 0] [yields] a[sub 0][sup -] [pi][sup +])

We present several searches for charmless hadronic two-body and three-body decays of B mesons from electron-positron annihilation data collected by the BABAR detector near the[Upsilon](4S) resonance. We report the preliminary branching fractions[Beta](B[sup 0][yields][pi][sup+][pi][sup -])= (4.1[+-] 1.0[+-] 0.7) x 10[sup -6], [Beta](B[sup 0][yields] K[sup+][pi][sup -])= (16.7[+-] 1.6[+-] 1.3) x 10[sup -6], [Beta](B[sup 0][yields][rho][sup -+][pi][sup -+])= (49[+-] 13[sub -5][sup+6]) x 10[sup -6], [Beta](B[sup+][yields][eta]' K[sup+])= (62[+-] 18[+-] 8) x 10[sup -6], and present upper limits for nine other decays.