Author: Curtis William Ward
Publisher:
ISBN:
Category :
Languages : en
Pages : 374

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Author: BELLE
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Category :
Languages : en
Pages : 8

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Author: Tetiana B. Hryn'ova
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ISBN:
Category :
Languages : en
Pages : 165

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B mesons are unique among well-established non-quarkonium mesons in their ability to decay into baryons. Baryonic B decays offer a wide range of interesting areas of study: they can be used to test our theoretical understanding of rare decay processes involving baryons, search for direct CP violation and study low-energy QCD. This thesis presents measurements of branching fractions and a study of the decay dynamics of the charmless three-body decays of B meson into p{bar p}h final states, where h = {pi}{sup +}, K{sup +}, K{sub S}{sup 0}, K*{sup 0} or K*{sup +}. With a sample of 232 million {Upsilon}(4S) {yields} B{bar B} events collected with the BaBar detector, we report the first observation of the B {yields} p{bar p}K*{sup 0} decay, and provide improved measurements of branching fractions of the other modes. The distribution of the three final-state particles is of particular interest since it provides dynamical information on the possible presence of exotic intermediate states such as the hypothetical pentaquark states {Theta}*{sup ++} and {Theta}{sup +}in the m{sub pK{sup +}} and m{sub pK{sub S}{sup 0}} spectra, respectively, or glueball states (such as the tensor glueball f{sub J}(2220)) in the m{sub p{bar p}} spectrum. No evidence for exotic states is found and upper limits on the branching fractions are set. An enhancement at low p{bar p} mass is observed in all the B {yields} p{bar p}h modes, and its shape is compared between the decay modes and with the shape of the time-like proton form factor. A Dalitz plot asymmetry in B {yields} p{bar p}K{sup +} mode suggests dominance of the penguin amplitude in this decay and disfavors the possibility that the low mass p{bar p} enhancement originates from the presence of a resonance below threshold (such as the recently seen baryonium candidate at 1835 MeV/c{sup 2}). We also identify decays of the type B {yields} X{sub c{bar c}}h {yields} p{bar p}h, where h = K{sup +}, K{sub S}{sup 0}, K*{sup 0} or K*{sup +}, and X{sub c{bar c}} = {eta}{sub c} or J/{psi}. In particular, we report on the evidence of the B {yields} {eta}{sub c}K*{sup +} decay and provide a measurement of the width of {eta}{sub c}.

Author: Robert Seddon
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Category :
Languages : en
Pages :

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"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"--

Author: Eric Ashton Eckhart
Publisher:
ISBN:
Category : Mesons
Languages : en
Pages :

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Abstract: We search for the decays of $B$ mesons to charmless final states involving a baryon and an anti-baryon using 9.2 fb -1 of e + e - annihilation data taken on the?(4s) resonance with the CLEO II and CLEO II. V detectors, and 6.2 fb -1 from CLEO III. We perform an extended maximum likelihood analysis of the data to determine signal yields. We report an observation of the decay mode B - -> p anti-p K - and measure its branching fraction to be (5.88 +2.86 -2.21 (stat.) +1.12 -0.19 (syst.)) x 10 -6 . We find no statistically significant signals for our other modes and establish 90% C.L. upper limits of BR(B -> p anti-p) 1.4 x 10 -6, BR(B - anti-p?) 1.5 x 10 -6, BR(B -? anti-?) 1.2 x 10 -6, and BR(B - anti-p?p +)

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 192

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The experimental study of rare decays of hadrons containing the b quark has been a fertile ground for some time, and keeps being one of the most interesting subjects in high energy physics. It has improved our understanding of hadronic processes, and allows investigating various aspects of the Standard Model and searching for hints of physics beyond the Standard Model. Examples are the comparison of branching fractions of charmless modes with predictions of models, the constraints on CKM angles (B0 → [pi]+[pi]-, B → DK, with D in suppressed modes), the observation of purely leptonic modes (B± → [tau]±v), the recently established difference in ACP between B0 → K+[pi]- and B± → K±[pi]0, suspected to be a hint new physics. All of them came from a long and successful experimental activity with e+e- collisions at the Y(4S) resonance. With hadronic colliders now coming into play, the study of rare decays is reaching new heights. Given the high cross section for production of all kinds of B hadrons, the record luminosities now provided by the Tevatron collider, and the LHC program in view for the next years, there is the potential for a rich program of interesting new measurements, including even rarer modes as the Bs0 → [mu]+[mu]-, strongly suppressed in the standard model but very sensitive to many NP scenarios. The complexity of the hadronic collision environment, however, requires detectors with high precision and high quality tracking, and a trigger system capable of complex event selections at high rates. The CDF experiment, thanks to a fast trigger on impact parameter, has been able to reconstruct many rare B decays, including previously unobserved modes Bs0 → K+K- and Bs0 → K-[pi]+, the latter being particularly interesting for its relationship with the puzzling difference in CP asymmetry between neutral and charged modes. In this thesis we go beyond B mesons, and present the first measurements of Branching fractions and CP asymmetries in charmless b-baryon modes. We study two-body [Lambda]b0 decays into final states with a proton and a charged pion or kaon. Their branching fractions can be significantly affected by New Physics contributions; under supersymmetric models with R-parity violation, they can be increased by two orders of magnitude. Their CP-violating asymmetries are also interesting to measure in search for possible further anomalies: then may reach significant size O(30%) in the Standard Model, and are also sensitive to possible new physics sources.

Author: John Joseph O'Neill (Ph. D. in physics)
Publisher:
ISBN:
Category : Mesons
Languages : en
Pages : 143

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Author: Deutsches Elektronen-Synchrotron (Hamburg).
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Category :
Languages : de
Pages :

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Author: Andrei Gritsan
Publisher:
ISBN:
Category : Baryons
Languages : en
Pages : 356

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Author: ARGUS Collaboration
Publisher:
ISBN:
Category :
Languages : en
Pages : 4

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