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First observation of the inclusive decay B → Xη′ with the Belle detector

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Item Summary

Title: First observation of the inclusive decay B → Xη′ with the Belle detector
Authors: Nishimura, Kurtis Alan
Keywords: B meson
Belle detector
Issue Date: Dec 2010
Publisher: [Honolulu] : [University of Hawaii at Manoa], [December 2010]
Abstract: The decay of a B meson into an η′ meson and an inclusive charmless state with unit strangeness, B → Xsη′, has stimulated significant theoretical interest since it was first observed in 1998. A number of models were proposed to explain the unexpectedly large branching fraction and the spectrum of Xs mass, which peaks above 2.0 GeV/c2. One of the most initially appealing explanations was the QCD anomaly model, in which the η′ couples strongly to two gluons. However, despite a number of theoretical calculations and improved measurements of the decay, no explanation has been universally accepted as accounting for available experimental data. The unique relationship between the η′ and the η suggest that the complimentary decay, B → Xsη, could elucidate the nature of the Xsη′ process.
We report the first measurement of inclusive B → Xsη decays, based on a pseudoinclusive reconstruction technique using a sample of 657×106 B ¯B pairs accumulated with the Belle detector at the KEKB e+e− collider. ForMXs < 2.6 GeV/c2, we measure a branching fraction of (26.1±3.0(stat)+1.9−2.1(syst)+4.0−7.1(model))×10−5 and a direct CP asymmetry of ACP = −0.13 ± 0.04+0.02−0.03. Over half of the signal occurs in the range MXs > 1.8 GeV/c2, above all currently known exclusive contributions to B → Xsη.
The lack of significant suppression of this decay relative to its η′ counterpart indicates that explanations for the B → Xsη′ signal that invoke mechanisms specific to the η′ are disfavored.
Description: Ph.D. University of Hawaii at Manoa 2010.
Includes bibliographical references.
URI/DOI: http://hdl.handle.net/10125/101927
Appears in Collections:Ph.D. - Physics



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