Rare Exclusive Dileptonic And Radiative Decays Of Lambdasubscript B Baryons In A Quark Model PDF Download
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| Author | : Lonnie James Mott |
| Publisher | : |
| Total Pages | : 95 |
| Release | : 2011 |
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| ISBN | : |
Download Rare Exclusive Dileptonic and Radiative Decays of [Lambda][subscript B] Baryons in a Quark Model Book in PDF, ePub and Kindle
ABSTRACT: Hadronic form factors for the rare weak transitions [Lambda][subscript b] [rightarrow] [Lambda][superscript (*)] are calculated using a nonrelativistic quark model. The form factors are extracted in two ways. An analytic extraction using single component wave functions (SCA) with the quark current being reduced to its nonrelativistic Pauli form is employed in the first method. In the second method, the form factors are extracted numerically using the full quark model wave function (MCN) with the full relativistic form of the quark current. Both sets of form factors are found to satisfy the relationships expecetd from the heavy quark effective theory (HQET). Differential decay rates, branching ratios and forward-backward asymmetries (FBAs) are calculated for the dileptonic decays [Lambda][subscript b][rightarrow] [Lambda][superscript (*)][ell]+[ell]-, for transitions to both ground state and excited daughter baryons. Inclusion of the long distance contributions from charmonium resonances significantly enhances the decay rates. It is found that in the MCN model the [Lambda](1600) mode is the dominant mode in the [mu] channel when charmonium resonances are considered; the [Lambda](1520) mode is also found to have a comparable branching ratio to that of the ground state in the [mu] channel. It has been found that the FBAs for decays to [Lambda](1115), [Lambda](1600) and [Lambda](1405) are less sensitive to the form of the form factors in certain kinematic regions.
| Author | : William Alfredo Loinaz |
| Publisher | : |
| Total Pages | : 230 |
| Release | : 1995 |
| Genre | : |
| ISBN | : |
Download Exclusive Semileptonic and Radiative Decays of B-baryons to Light Baryons Book in PDF, ePub and Kindle
| Author | : |
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| Total Pages | : |
| Release | : 2005 |
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| ISBN | : |
Download Semileptonic Decays of Heavy Lambda Baryons in a Quark Model Book in PDF, ePub and Kindle
The semileptonic decays of [Lambda]{sub c} and [Lambda]{sub b} are treated in the framework of a constituent quark model. Both nonrelativistic and semirelativistic Hamiltonians are used to obtain the baryon wave functions from a fit to the spectra, and the wave functions are expanded in both the harmonic oscillator and Sturmian bases. The latter basis leads to form factors in which the kinematic dependence on q2 is in the form of multipoles, and the resulting form factors fall faster as a function of q2 in the available kinematic ranges. As a result, decay rates obtained in the two models using the Sturmian basis are significantly smaller than those obtained using the harmonic oscillator basis. In the case of the [Lambda]{sub c}, decay rates calculated using the Sturmian basis are closer to the experimentally reported rates. However, we find a semileptonic branching fraction for the [Lambda]{sub c} to decay to excited [Lambda]* states of 11% to 19%, in contradiction with what is assumed in available experimental analyses. Our prediction for the [Lambda]{sub b} semileptonic decays is that decays to the ground state [Lambda]{sub c} provide a little less than 70% of the total semileptonic decay rate. For the decays [Lambda]{sub b} → [Lambda]{sub c}, the analytic form factors we obtain satisfy the relations expected from heavy-quark effective theory at the non-recoil point, at leading and next-to-leading orders in the heavy-quark expansion. In addition, some features of the heavy-quark limit are shown to naturally persist as the mass of the heavy quark in the daughter baryon is decreased.
| Author | : Robert Seddon |
| Publisher | : |
| Total Pages | : |
| Release | : 2019 |
| Genre | : |
| ISBN | : |
Download Search for the Rare Decay of a B Meson Into a Lambda Baryon, Proton and Neutrino-antineutrino Pair at the BABAR and Belle II Experiments Book in PDF, ePub and Kindle
"We present two analyses of the rare B- -> Lambda pbar nu nubar decay. Within the Standard Model, the process B- -> Lambda pbar nu nubar is permitted but highly suppressed, with an expected branching fraction of (7.9 +/- 1.9) x 10^-7. This rarity makes it a sensitive probe for the existence of new physics, which may be discoverable in the form of a higher than predicted branching fraction.The first analysis is conducted on data collected at the BABAR experiment, which ran from 1999-2008. BABAR collected 433 fb^-1 of integrated luminosity at the Upsilon(4S) resonance; Upsilon(4S) decays almost exclusively into B-Bbar pairs, and this analysis uses hadronic tag reconstruction to fully reconstruct one of the B-mesons in this pair. The search for B- -> Lambda pbar nu nubar is then conducted among the decay products of the second, unreconstructed B-meson. Using both real data and Monte Carlo simulations, we develop and implement a signal selection that selects candidates conforming to the expected characteristics of B- -> Lambda pbar nu nubar decays. The result of the analysis is an upper limit on the branching fraction at the 90% confidence level of 3.02 x 10^-5. This is the world's first experimental result in the search for B- -> Lambda pbar nu nubar decays.The second analysis is conducted on Monte Carlo simulations of data that will be collected at Belle II, the world's only next-generation B-meson facility. Over its lifetime Belle II will collect 50 ab^-1 of data, approximately 100 times that of BABAR. This increase in data, along with more capable hardware and software, should allow Belle II to search for B- -> Lambda pbar nu nubar decays with greater sensitivity than BABAR. Using a simulated dataset equivalent in size to that used in our BABAR study, we employ Full Event Interpretation to fully reconstruct the decay of one B-meson in each B-Bbar pair, and conduct our signal selection in the remainder of the data. The result of the analysis is a predicted upper limit on the branching fraction at the 90% confidence level of 1.2 x 10^-4. A comparison of the Belle II and BABAR results highlights several areas where Belle II will need to improve in order to make best use of its projected dataset"--
