116 research outputs found
Semileptonic form factors - a model-independent approach
We demonstrate that the B->D(*) l nu form factors can be accurately predicted
given the slope parameter rho^2 of the Isgur-Wise function. Only weak
assumptions, consistent with lattice results, on the wavefunction for the light
degrees of freedom are required to establish this result. We observe that the
QCD and 1/m_Q corrections can be systematically represented by an effective
Isgur-Wise function of shifted slope. This greatly simplifies the analysis of
semileptonic B decay. We also investigate what the available semileptonic data
can tell us about lattice QCD and Heavy Quark Effective Theory. A rigorous
identity relating the form factor slope difference rho_D^2-rho_A1^2 to a
combination of form factor intercepts is found. The identity provides a means
of checking theoretically evaluated intercepts with experiment.Comment: 18 pages, Revtex, 4 postscript figures, uses epsfig.st
Evaluating the Knowledge Base Completion Potential of GPT
Structured knowledge bases (KBs) are an asset for search engines and other applications, but are inevitably incomplete. Language models (LMs) have been proposed for unsupervised knowledge base completion (KBC), yet, their ability to do this at scale and with high accuracy remains an open question. Prior experimental studies mostly fall short because they only evaluate on popular subjects, or sample already existing facts from KBs. In this work, we perform a careful evaluation of GPT's potential to complete the largest public KB: Wikidata. We find that, despite their size and capabilities, models like GPT-3, ChatGPT and GPT-4 do not achieve fully convincing results on this task. Nonetheless, they provide solid improvements over earlier approaches with smaller LMs. In particular, we show that, with proper thresholding, GPT-3 enables to extend Wikidata by 27M facts at 90% precision.</p
Distinguishing WH and WBBbar production at the Fermilab Tevatron
The production of a Higgs boson in association with a W-boson is the most
likely process for the discovery of a light Higgs at the Fermilab Tevatron.
Since it decays primarily to b-quark pairs, the principal background for this
associated Higgs production process is WBBbar, where the BBbar pair comes from
the splitting of an off mass shell gluon. In this paper we investigate whether
the spin angular correlations of the final state particles can be used to
separate the Higgs signal from the WBBbar background. We develop a general
numerical technique which allows one to find a spin basis optimized according
to a given criterion, and also give a new algorithm for reconstructing the W
longitudinal momentum which is suitable for the WH and WBBbar processes.Comment: latex, 12 pages, 19 postscript figure
Direct experimental test of scalar confinement
The concept of Lorentz scalar quark confinement has a long history and is
still widely used despite its well-known theoretical faults. We point out here
that the predictions of scalar confinement also conflict directly with
experiment. We investigate the dependence of heavy-light meson mass differences
on the mass of the light quark. In particular, we examine the strange and
non-strange D mesons. We find that the predictions of scalar confinement are in
considerable conflict with measured values.Comment: REVTeX4, 7 pages, 4 EPS figure
Decay constants of P and D-wave heavy-light mesons
We investigate decay constants of P and D-wave heavy-light mesons within the
mock-meson approach. Numerical estimates are obtained using the relativistic
quark model. We also comment on recent calculations of heavy-light
pseudo-scalar and vector decay constants.Comment: REVTeX, 22 pages, uses epsf macro, 8 postscript figures include
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