Observation And Study of B Meson Decays with Lambda(C) Baryons with the BaBar Detector
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Page : 6 pages
File Size : 12,12 MB
Release : 2013
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Study of B-Meson Decays to Final States with a Single Charm Baryon
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Page : 208 pages
File Size : 48,5 MB
Release : 2007
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A study of B-meson decays to final states with a single charm baryon is presented based on data recorded by the BABAR detector at the Stanford Linear Accelerator Center. Although the B meson is the lightest bottom-flavored meson, it is heavy enough to decay to a baryon made of three quarks and an antibaryon made of three antiquarks. By studying the baryonic weak decays of the B meson, we can investigate baryon production mechanisms in heavy meson decays. In particular, we measure the rates of the decays B- → [Lambda]+c$\bar{p}$[pi]- and $\bar{B}$0 → [Lambda]+c$\bar{p}$. Comparing these rates, we confirm an observed trend in baryonic B decays that the decay with the lower energy release, B- → [Lambda]+c$\bar{p}$[pi]-, is favored over $\bar{B}$0 → [Lambda]+c$\bar{p}$. The dynamics of the baryon-antibaryon ([Lambda]+c$\bar{p}$) system in the three-body decay also provide insight into baryon-antibaryon production mechanisms. The B- → [Lambda]+c$\bar{p}$[pi]- system is a laboratory for searches for excited #c baryon states; we observe the resonant decays B- → [Sigma]c(2455) 0$\bar{p}$ and B- → [Sigma]c(2800) 0$\bar{p}$. This is the first observation of the decay B- → [Sigma]c(2800) 0$\bar{p}$; however, the mass of the observed #c(2800)0 state is inconsistent with previous measurements. Finally, we examine the angular distribution of the B- → [Sigma]c(2455) 0$\bar{p}$ decays and measure the spin of the B- → [Sigma]c(2455) 0$\bar{p}$ baryon to be J = 1/2, as predicted by the quark model.
A Measurement of the Lambda-c Baryon Decays to Proton Kaon( - ) Pion(+) Absolute Branching Fraction with the BaBar Detector
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Page : pages
File Size : 34,27 MB
Release : 2004
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A measurement of [Beta]([Lambda][sub c][sup +] [yields] pK[sup -] [pi][sup +]) is presented based on data collected with the BaBar detector at the Stanford Linear Accelerator Center. Branching fraction measurements represent a large portion of what is known about short-lived particles, the strong force that binds them, and the weak force that causes them to decay. While the majority of branching fraction measurements are done as ratios between two decay modes, it is the absolute measurements of a few particular decay modes that set the scale for these relative measurements. The [Lambda][sub c][sup +] particle is one of the four weakly decaying hadrons into which more than 90% of the known heavy quark hadrons will eventually decay. Thus, an absolute measurement of the branching fraction for [Lambda][sub c][sup +] [yields] pK[sup -][pi][sup +] is important for many studies of the heavy quark sector, from spectroscopy to B meson decays. The number of produced [Lambda][sub c][sup +]'s is inferred from the number of events reconstructed with an antiproton and an accompanying D meson. The final result of [Beta]([Lambda][sub c][sup +] [yields] pK[sup -] [pi][sup +]) = [6.12 [+-] 0.31(stat.) [+-] 0.42(syst.)]% represents more than a two-fold improvement in precision over the world average. The dominant source of systematic uncertainty is the irreducible background of [Xi][sub c] baryons.
Search for Semileptonic Decays in the B Meson Into the [Lambda]+[subscript C] Baryon
Author : Tomohiko Tanabe
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Page : 248 pages
File Size : 11,94 MB
Release : 2009
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Observation and Study of the Baryonic B-meson Decays B to D(*) P Pbar??
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Page : 24 pages
File Size : 36,90 MB
Release : 2012
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We present results for B-meson decay modes involving a charm meson, protons, and pions using 455 x 106 B{bar B} pairs recorded by the BABAR detector at the SLAC PEP-II asymmetric-energy ee− collider. The branching fractions are measured for the following ten decays: {bar B}° → D°p{bar p}, {bar B}° → D*°p{bar p}, {bar B}° → D+p{bar p}?−, {bar B}° → D*+p{bar p}?−, B− → D°p{bar p}?−, B− → D*°pp?−, {bar B}° → D°p{bar p}?−?+, {bar B}° → D*°p{bar p}?−?+, B− → D+p{bar p}?−?−, and B− → D*+p{bar p}?−?−. The four B− and the two five-body B° modes are observed for the first time. The four-body modes are enhanced compared to the three- and the five-body modes. In the three-body modes, the M(p{bar p}) and M(D{sup (*)0}p) invariant mass distributions show enhancements near threshold values. In the four-body mode {bar B}° → D+p{bar p}?−, the M(p?−) distribution shows a narrow structure of unknown origin near 1.5GeV/c2. The distributions for the five-body modes, in contrast to the others, are similar to the expectations from uniform phase-space predictions.
Study of B Meson Decays to Ppbarh Final States
Author : Tetiana B. Hryn'ova
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Page : 165 pages
File Size : 50,65 MB
Release : 2006
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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}.
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
Author : Robert Seddon
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Page : pages
File Size : 32,92 MB
Release : 2019
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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"--
Measurements of {\cal B}(\overline{B}0̂ \to \Lambda_{c}{̂+} \overline{p}) and {\cal B}(B-̂ \to \Lambda_{c}{̂+} \overline{p} \pi-̂) and Studies of \Lambda_{c}{̂+}\pi-̂ Resonances
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Page : 20 pages
File Size : 17,79 MB
Release : 2008
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The authors present an investigation of the decays {bar B}° →?{sub c}{bar p} and B− →?{sub c}+{bar p}?− based on 383 x 106?(4S) → B{bar B} decays recorded with the BABAR detector. They measure the branching fractions of these decays; their ratio is?(B− →?{sub c}+{bar p}?−)/?({bar B}° →?{sub c}+{bar p}) = 15.4 ± 1.8 ± 0.3. The B− →?{sub c}+{bar p}?− process exhibits an enhancement at the?{sub c}+{bar p} threshold and is a laboratory for searches for excited charm baryon states. They observe the resonant decays B− →?{sub c}(2455)°{bar p} and B−?{sub c}(2800)°{bar p} but see no evidence for B− →?{sub c}(2520)°{bar p}. This is the first observation of the decay B− →?{sub c}(2800)°{bar p}; however, the mass of the observed excited?{sub c}° state is (2846 ± 8 ± 10) MeV/c2, which is somewhat inconsistent with previous measurements. Finally, they examine the angular distribution of the B− →?{sub c}(2455)°{bar p} decays and measure the spin of the?{sub c}(2455)° baryon to be 1/2, as predicted by the quark model.
Observation of Inclusive B Meson Decays Into [lambda]+c̳ Baryons
Author : ARGUS Collaboration
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Page : 5 pages
File Size : 15,41 MB
Release : 1988
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Observation of the Baryonic B Decay B0bar to Lambda_c^+ Anti-Lambda K-
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Page : 7 pages
File Size : 22,37 MB
Release : 2011
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The authors report the observation of the baryonic B decay {bar B}° 2![Lambda]{sub c} {bar [Lambda]}K− with a significance larger than 7 standard deviations based on 471 x 106 B{bar B} pairs collected with the BABAR detector at the PEP-II storage ring at SLAC. They measure the branching fraction for the decay {bar B}° 2![Lambda]{sub c}+ {bar [Lambda]}K− to be (3.8 ± 0.8{sub stat} ± 0.2{sub sys} ± 1.0 {sub {Lambda}{sub c}+}) x 10−5. The uncertainties are statistical, systematic, and due to the uncertainty in the {Lambda}{sub c}+ branching fraction. They find that the {Lambda}{sub c}+ K− invariant mass distribution shows an enhancement above 3.5 GeV/c2.
