arXiv subjects
Publications and source records attributed to Giorgi Piranishvili.
Rare B decays allow to investigate fundamental interactions regarding their flavor, chiral, Dirac and CP properties. In anticipation of the large data samples of exclusive B decays into muons from the forthcoming LHC experiments, in particular LHCb, as well as possible super flavor factories, we review the theoretical status and outline future opportunities to explore the borders of the Standard Model and beyond.
The decay bar B -> bar K* (-> bar K pi) l+ l- offers great opportunities to explore the physics at and above the electroweak scale by means of an angular analysis. We investigate the physics potential of the seven CP asymmetries plus the asymmetry in the rate, working at low dilepton mass using QCD factorization at next-to leading order (NLO). The b ->s CP asymmetries are doubly Cabibbo-suppressed \lesssim 1 % in the Standard Model and its extensions where the CKM matrix is the only source of CP violation. Three CP asymmetries are T-odd, and can be O(1) in the presence of non-standard CP violation. The T-even asymmetries can reach O(0.1), limited by the small strong phases in the large recoil region. We furthermore point out an easy way to measure CP phases from time-integrated, untagged bar B_d, B_d -> K* (-> K0 pi0) l+ l- and bar B_s,B_s -> phi (-> K+ K-) l+ l- decays. Analyses of these CP asymmetries can rule out, or further support the minimal description of CP violation through the CKM mechanism. Experimental studies are promising for (super) flavor factories and at hadron colliders.
We model-independently analyze the angular distributions of B -> K ll decays, l = e, mu, for low dilepton mass using QCD factorization. Besides the decay rate, we study the forward-backward asymmetry A_FB^l and a further observable, F_H^l, which gives rise to a flat term in the angular distribution. We find that in the Standard Model F_H^l ~ m_l^2, hence vanishing F_H^e and F_H^mu of around 2% (exact value depends on cuts) with a very small theoretical uncertainty of a few percent. We also give predictions for R_K, the ratio of B -> K mu mu to B -> K ee decay rates. We analytically show using large recoil symmetry relations that in the Standard Model R_K equals one up to lepton mass corrections of the order 10^(-4). The New Physics reach of the observables from the B -> K ll angular analysis is explored together with R_K and the B_s -> ll and B -> X_s ll branching ratios for both l = e and l = mu. We find substantial room for signals from (pseudo-) scalar and tensor interactions beyond the Standard Model. Experimental investigations of the B -> K mu mu angular distributions are suitable for the LHC environment and high luminosity B factories, where also studies of the electron modes are promising.
The article contains new results for spin-3/2 and -1/2 resonances. It specializes to the second resonance region, which includes the $P_{11}(1440)$, $D_{13}(1520)$ and $S_{11}(1535)$ resonances. New data on electroproduction enable us to determine the vector form factors accurately. Estimates for the axial couplings are obtained from decay rates of the resonances with the help of the partially conserved axial current (PCAC) hypothesis. We present cross sections to be compared with the running and future experiments. The article is self--contained and allows the reader to write simple programs for reproducing the cross sections and for obtaining additional differential cross sections.