Precision measurements of tau lepton decays
| dc.contributor.author | Nugent, Ian Michael | |
| dc.contributor.supervisor | Roney, J. Michael | |
| dc.date.accessioned | 2008-12-30T19:55:46Z | |
| dc.date.available | 2008-12-30T19:55:46Z | |
| dc.date.copyright | 2008 | en_US |
| dc.date.issued | 2008-12-30T19:55:46Z | |
| dc.degree.department | Department of Physics and Astronomy | |
| dc.degree.level | Doctor of Philosophy Ph.D. | en_US |
| dc.description.abstract | Using data collected with the BABAR detector at the SLAC PEP-II electron-positron storage ring operating at a centre-of-mass energy near 10.58 GeV, the branching fractions $B(\tau^- \to \pi^-\pi^-\pi^+\nu_\tau) =(8.83\pm0.01\pm0.13)\%$, $B(\tau^- \to K^-\pi^-\pi^+\nu_\tau) =(0.273\pm0.002 \pm 0.009)\%$, $B(\tau^- \to K^-\pi^-K^+\nu_\tau) =(0.1346 \pm 0.0010 \pm 0.0036)\%$, and $B(\tau^- \to K^-K^-K^+\nu_\tau) =(1.58 \pm 0.13 \pm 0.12)\times10^{-5}$ are measured where the uncertainties are statistical and systematic, respectively. The invariant mass distribution for the $\tau^- \to \pi^-\pi^-\pi^+\nu_\tau$, $\tau^- \to K^-\pi^-\pi^+\nu_\tau$, $\tau^- \to K^-\pi^-K^+\nu_\tau$, and $\tau^- \to K^-K^-K^+\nu_\tau$ decays are unfolded to correct for detector effects. A measurement of $B(\tau^- \to \phi\pi^-\nu_\tau)=(3.42\pm0.55\pm0.25)\times10^{−5}$, a measurement of $B(\tau^- \to \phi^-K^-\nu_\tau) =(3.39\pm0.20\pm0.28)\times10^{−5}$ and an upper limit on $B(\tau^- \to K^-K^-K^+\nu_\tau [ex.\phi]) < =2.5\times10^{−6}$@90\%CL are determined from a binned maximum likelihood fit of the $\tau^- \to K^-\pi^-K^+\nu_\tau$ and $\tau^- \to K^-K^-K^+\nu_\tau$ $K^+K^−$ invariant mass distributions. The branching ratio $B(\tau^- \to K^-\nu_\tau)/B(\tau^- \to\pi^-\nu_\tau)$ is measured to be $(6.531\pm0.056\pm0.093)\times10^{−2}$ from which $|V_{us}|$ is determined to be $0.2255 \pm 0.0023$. The branching ratio $B(\tau^- \to \mu^-\nu_\tau\bar{\nu}_\mu)/B(\tau^- \to e^-\nu_\tau\bar{\nu}_e) =(9.796 \pm 0.016 \pm 0.035)\times10^{−1}$ is measured enabling a precision test of the Standard Model assumption of charged current lepton universality, $g_{\mu}/g_{e}=1.0036 \pm 0.0020$. The branching ratios $B(\tau^- \to K^-\nu_\tau)/B(\tau^- \to e^-\nu_\tau\bar{\nu}_e)=(3.882 \pm 0.032 \pm 0.056)\times10^{−2}$, and $B(\tau^- \to\pi^-\nu_\tau)/B(\tau^- \to e^-\nu_\tau\bar{\nu}_e)=(5.945 \pm 0.014 \pm 0.061)\times10^{−1}$ are measured which provide additional tests of charged current lepton universality, $(g_{\tau}/g_{\mu})_{\pi}= 0.9856 \pm 0.0057$ and $(g_{\tau}/g_{\mu})_{K}= 0.9827 \pm 0.0086$ which can be combined to give $(g_{\tau}/g_{\mu})_{\pi/K}= 0.9850 \pm 0.0054$. Any deviation of these measurements from the expected Standard Model values would be an indication of new physics. | en_US |
| dc.identifier.uri | http://hdl.handle.net/1828/1317 | |
| dc.language | English | eng |
| dc.language.iso | en | en_US |
| dc.rights | Available to the World Wide Web | en_US |
| dc.subject | High Energy Physics | en_US |
| dc.subject | BaBar | en_US |
| dc.subject | tau | en_US |
| dc.subject | lepton universality | en_US |
| dc.subject | particle physics | en_US |
| dc.subject | CKM Matrix | en_US |
| dc.subject.lcsh | UVic Subject Index::Sciences and Engineering::Physics | en_US |
| dc.title | Precision measurements of tau lepton decays | en_US |
| dc.type | Thesis | en_US |