Search for the Rare Decay B to pi l+l- in the BaBar Experiment

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The rare decay B {yields} {pi}{ell}{sup +}{ell}{sup -} is the simplest manifestation of a b {yields} d{ell}{sup +}{ell}{sup -} flavor-changing neutral current (FCNC) process. This type of process only proceeds through penguin loop or box diagrams and is sensitive to physics at the electroweak scale. It can be used to constrain parameters of the Standard Model and its extensions. B {yields} {pi}{ell}{sup +}{ell}{sup -} events have not yet been observed; the branching fraction is expected to be an order of magnitude smaller than the measured branching fraction for the similar B {yields} K{ell}{sup +}{ell}{sup -} decay. Using 230 million B{bar ... continued below

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167 pages

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Ofte, Ingrid & U., /Bergen July 17, 2007.

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The rare decay B {yields} {pi}{ell}{sup +}{ell}{sup -} is the simplest manifestation of a b {yields} d{ell}{sup +}{ell}{sup -} flavor-changing neutral current (FCNC) process. This type of process only proceeds through penguin loop or box diagrams and is sensitive to physics at the electroweak scale. It can be used to constrain parameters of the Standard Model and its extensions. B {yields} {pi}{ell}{sup +}{ell}{sup -} events have not yet been observed; the branching fraction is expected to be an order of magnitude smaller than the measured branching fraction for the similar B {yields} K{ell}{sup +}{ell}{sup -} decay. Using 230 million B{bar B} meson pairs collected with the BABAR detector, we have done a search for the rare decay B {yields} {pi}{ell}{sup +}{ell}{sup -}. The data was produced in e+e? collision at the {Upsilon}(4S) resonance in the PEP-II collider between 1999 and 2004. Four exclusive B-meson decay modes have been reconstructed: B{sup +} {yields} {pi}{sup +}{ell}{sup +}{ell}{sup -} and B{sup 0} {yields} {pi}{sup 0}{ell}{sup +}{ell}{sup -}, where {ell}{sup +}{ell}{sup -} is either an electron pair (e{sup +}e{sup -}) or a muon pair ({mu}{sup +}{mu}{sup -}). We find no evidence for a signal, and we obtain upper limits on the branching fractions {Beta}. Assuming the isospin relation {Beta}(B{sup +} {yields} {pi}{sup +}{ell}{sup +}{ell}{sup -}) 2 x {sup {tau}}B{sup +}/{sup {tau}}B{sup 0} {Beta}(B{sup 0} {yields} {pi}{sup 0}{ell}{sup +}{ell}{sup -}), we obtain an upper limit at 90% confidence level on the lepton-flavor-averaged branching fraction of B {yields} {pi}{ell}{sup +}{ell}{sup -} to be {Beta}(B {yields} {pi}e{mu}) < 9.2 x 10{sup -8} at 90% C.L. We have also reconstructed two control modes B{sup +} {yields} {pi}{sup +}e{sup {+-}}{mu}{sup {-+}} and B{sup 0} {yields} {pi}{sup 0}e{sup {+-}}{mu}{sup {-+}} and we also obtain an upper limit at 90% confidence level on the lepton-flavor-violating decay B {yields} {pi}e{mu} of {Beta}(B {yields} {pi}e{mu}) < 9.2 x 10{sup -8} at 90% C.L. This is the first search for these rare decays at the current B-Factory experiments. This limit is an improvement by four orders of magnitude with respect to the previous experimental limit, and about a factor three above Standard Model predictions.

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167 pages

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  • Report No.: SLAC-R-859
  • Grant Number: AC02-76SF00515
  • Office of Scientific & Technical Information Report Number: 922606
  • Archival Resource Key: ark:/67531/metadc893181

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • July 17, 2007

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  • Sept. 27, 2016, 1:39 a.m.

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  • Dec. 1, 2016, 7:08 p.m.

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Ofte, Ingrid & U., /Bergen. Search for the Rare Decay B to pi l+l- in the BaBar Experiment, thesis or dissertation, July 17, 2007; [Menlo Park, California]. (digital.library.unt.edu/ark:/67531/metadc893181/: accessed January 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.