Showing papers by "Sudarshan Paramesvaran published in 2010"

Search forB+→ℓ+νℓrecoiling againstB−→D0ℓ−ν¯X

Abstract: We present a search for the decay ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{+}{\ensuremath{ u}}_{\ensuremath{\ell}}(\ensuremath{\ell}=\ensuremath{\tau},\ensuremath{\mu},\text{ }\mathrm{\text{or}}\text{ }e)$ in $(458.9\ifmmode\pm\else\textpm\fi{}5.1)\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs recorded with the BABAR detector at the PEP-II $B$-factory. We search for these $B$ decays in a sample of ${B}^{+}{B}^{\ensuremath{-}}$ events where one $B$-meson is reconstructed as ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{0}{\ensuremath{\ell}}^{\ensuremath{-}}\overline{\ensuremath{ u}}X$. Using the method of Feldman and Cousins, we obtain $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{ u}}_{\ensuremath{\tau}})=(1.7\ifmmode\pm\else\textpm\fi{}0.8\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, which excludes zero at $2.3\ensuremath{\sigma}$. We interpret the central value in the context of the standard model and find the $B$ meson decay constant to be ${f}_{B}^{2}=(62\ifmmode\pm\else\textpm\fi{}31)\ifmmode\times\else\texttimes\fi{}{10}^{3}\text{ }\text{ }{\mathrm{MeV}}^{2}$. We find no evidence for ${B}^{+}\ensuremath{\rightarrow}{e}^{+}{\ensuremath{ u}}_{e}$ and ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{ u}}_{\ensuremath{\mu}}$ and set upper limits at the 90% C.L. $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{e}^{+}{\ensuremath{ u}}_{e})l0.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ and $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{ u}}_{\ensuremath{\mu}})l1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$.

Measurement of the gamma gamma* -> eta c transition form factor

Abstract: We thank V. L. Chernyak for useful discussions. We are grateful for the extraordinary contributions of our PEP-II colleagues in achieving the excellent luminosity and machine conditions that have made this work possible. The success of this project also relies critically on the expertise and dedication of the computing organizations that support BABAR. The collaborating institutions wish to thank SLAC for its support and the kind hospitality extended to them. This work is supported by the US Department of Energy and National Science Foundation, the Natural Sciences and Engineering Research Council (Canada), the Commissariat a l'Energie Atomique and Institut National de Physique Nucleaire et de Physique des Particules (France), the Bundesministerium fur Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), the Foundation for Fundamental Research on Matter (The Netherlands), the Research Council of Norway, the Ministry of Science and Technology of the Russian Federation, Ministerio de Educacion y Ciencia (Spain), and the Science and Technology Facilities Council (United Kingdom). Individuals have received support from the Marie-Curie IEF program (European Union) and the A. P. Sloan Foundation.

Study ofB→Xγdecays and determination of|Vtd/Vts|

Abstract: Using a sample of $471\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ events collected with the BABAR detector, we study the sum of seven exclusive final states $B\ensuremath{\rightarrow}{X}_{s(d)}\ensuremath{\gamma}$, where ${X}_{s(d)}$ is a strange (nonstrange) hadronic system with a mass of up to $2.0\text{ }\text{ }\mathrm{GeV}/{c}^{2}$. After correcting for unobserved decay modes, we obtain a branching fraction for $b\ensuremath{\rightarrow}d\ensuremath{\gamma}$ of $(9.2\ifmmode\pm\else\textpm\fi{}2.0(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}2.3(\mathrm{syst}))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ in this mass range, and a branching fraction for $b\ensuremath{\rightarrow}s\ensuremath{\gamma}$ of $(23.0\ifmmode\pm\else\textpm\fi{}0.8(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}3.0(\mathrm{syst}))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ in the same mass range. We find $\frac{\mathcal{B}(b\ensuremath{\rightarrow}d\ensuremath{\gamma})}{\mathcal{B}(b\ensuremath{\rightarrow}s\ensuremath{\gamma})}=0.040\ifmmode\pm\else\textpm\fi{}0.009(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.010(\mathrm{syst})$, from which we determine $|{V}_{td}/{V}_{ts}|=0.199\ifmmode\pm\else\textpm\fi{}0.022(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.024(\mathrm{syst})\ifmmode\pm\else\textpm\fi{}0.002(\mathrm{th})$.

Search forb→utransitions inB−→DK−andD*K−decays

Abstract: We report results from an updated study of the suppressed decays ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}D{K}^{\ensuremath{-}}$ and ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{*}{K}^{\ensuremath{-}}$ followed by $D\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, where ${D}^{(*)}$ indicates a ${D}^{(*)0}$ or a ${\overline{D}}^{(*)0}$ meson, and ${D}^{*}\ensuremath{\rightarrow}D{\ensuremath{\pi}}^{0}$ or ${D}^{*}\ensuremath{\rightarrow}D\ensuremath{\gamma}$. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity triangle angle $\ensuremath{\gamma}$ due to interference between the $b\ensuremath{\rightarrow}c$ transition ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{(*)0}{K}^{\ensuremath{-}}$ followed by the doubly Cabibbo-suppressed decay ${D}^{0}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, and the $b\ensuremath{\rightarrow}u$ transition ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{\overline{D}}^{(*)0}{K}^{\ensuremath{-}}$ followed by the Cabibbo-favored decay ${\overline{D}}^{0}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$. We also report an analysis of the decay ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{(*)}{\ensuremath{\pi}}^{\ensuremath{-}}$ with the $D$ decaying into the doubly Cabibbo-suppressed mode $D\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$. Our results are based on $467\ifmmode\times\else\texttimes\fi{}\phantom{\rule{0ex}{0ex}}{10}^{6}$ $\ensuremath{\Upsilon}(4S)\ensuremath{\rightarrow}B\overline{B}$ decays collected with the BABAR detector at SLAC. We measure the ratios ${\mathcal{R}}^{(*)}$ of the suppressed ($[{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{]}_{D}{K}^{\ensuremath{-}}/{\ensuremath{\pi}}^{\ensuremath{-}}$) to favored ($[{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{]}_{D}{K}^{\ensuremath{-}}/{\ensuremath{\pi}}^{\ensuremath{-}}$) branching fractions as well as the $CP$ asymmetries ${\mathcal{A}}^{(*)}$ of those modes. We see indications of signals for the ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}D{K}^{\ensuremath{-}}$ and ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}_{D{\ensuremath{\pi}}^{0}}^{*}{K}^{\ensuremath{-}}$ suppressed modes, with statistical significances of 2.1 and $2.2\ensuremath{\sigma}$, respectively, and we measure: ${\mathcal{R}}_{DK}=(1.1\ifmmode\pm\else\textpm\fi{}0.6\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2},\phantom{\rule{2em}{0ex}}{\mathcal{A}}_{DK}=\ensuremath{-}0.86\ifmmode\pm\else\textpm\fi{}{0.47}_{\ensuremath{-}0.16}^{+0.12}$, ${\mathcal{R}}_{(D{\ensuremath{\pi}}^{0})K}^{*}=(1.8\ifmmode\pm\else\textpm\fi{}0.9\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0ex}{0ex}}0.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2},\phantom{\rule{2em}{0ex}}{\mathcal{A}}_{(D{\ensuremath{\pi}}^{0})K}^{*}=+0.77\ifmmode\pm\else\textpm\fi{}0.35\ifmmode\pm\else\textpm\fi{}0.12,\phantom{\rule{2em}{0ex}}{\mathcal{R}}_{(D\ensuremath{\gamma})K}^{*}=(1.3\ifmmode\pm\else\textpm\fi{}1.4\ifmmode\pm\else\textpm\fi{}0.8)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2},{\mathcal{A}}_{(D\ensuremath{\gamma})K}^{*}=+0.36\phantom{\rule{0ex}{0ex}}\ifmmode\pm\else\textpm\fi{}{0.94}_{\ensuremath{-}0.41}^{+0.25}$, where the first uncertainty is statistical and the second is systematic. We use a frequentist approach to obtain the magnitude of the ratio ${r}_{B}\ensuremath{\equiv}|A({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{\overline{D}}^{0}{K}^{\ensuremath{-}})/A({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{0}{K}^{\ensuremath{-}})|=({9.5}_{\ensuremath{-}4.1}^{+5.1})%$, with ${r}_{B}l16.7%$ at 90% confidence level. In the case of ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{*}{K}^{\ensuremath{-}}$ we find ${r}_{B}^{*}\ensuremath{\equiv}|A({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{\overline{D}}^{*0}{K}^{\ensuremath{-}})/A({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{*0}{K}^{\ensuremath{-}})|=({9.6}_{\ensuremath{-}5.1}^{+3.5})%$, with ${r}_{B}^{*}l15.0%$ at 90% confidence level.

Observation of theΥ(13DJ)bottomonium state through decays toπ+π−Υ(1S)

Abstract: Based on $122\ifmmode\times\else\texttimes\fi{}{10}^{6}\mathit{\ensuremath{\Upsilon}}(3S)$ events collected with the BABAR detector, we have observed the $\mathit{\ensuremath{\Upsilon}}({1}^{3}{D}_{J})$ bottomonium state through the $\mathit{\ensuremath{\Upsilon}}(3S)\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}\mathit{\ensuremath{\Upsilon}}({1}^{3}{D}_{J})\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\mathit{\ensuremath{\Upsilon}}(1S)$ decay chain. The significance for the $J=2$ member of the $\mathit{\ensuremath{\Upsilon}}({1}^{3}{D}_{J})$ triplet is 5.8 standard deviations including systematic uncertainties. The mass of the $J=2$ state is determined to be $10\text{ }164.5\ifmmode\pm\else\textpm\fi{}0.8(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.5(\mathrm{syst})\text{ }\text{ }\mathrm{MeV}/{c}^{2}$. We use the ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ invariant mass distribution to confirm the consistency of the observed state with the orbital angular momentum assignment of the $\mathit{\ensuremath{\Upsilon}}({1}^{3}{D}_{J})$.

Study of B→Xγ decays and determination of |V_{td}/V_{ts}|

Abstract: Using a sample of 471×10^6 BB[overbar] events collected with the BABAR detector, we study the sum of seven exclusive final states B→X_(s(d))γ, where X_(s(d)) is a strange (nonstrange) hadronic system with a mass of up to 2.0 GeV/c^2. After correcting for unobserved decay modes, we obtain a branching fraction for b→dγ of (9.2±2.0(stat)±2.3(syst))×10^(-6) in this mass range, and a branching fraction for b→sγ of (23.0±0.8(stat)±3.0(syst))×10^(-5) in the same mass range. We find B[script](b→dγ)/B[script](b→sγ)=0.040±0.009(stat)±0.010(syst), from which we determine |V_(td)/V_(ts)|=0.199±0.022(stat)±0.024(syst)±0.002(th).

Search forfJ(2220)in RadiativeJ/ψDecays

Abstract: We present a search for ${f}_{J}(2220)$ production in radiative $J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\gamma}{f}_{J}(2220)$ decays using $460\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected with the BABAR detector at the SLAC PEP-II ${e}^{+}{e}^{\ensuremath{-}}$ collider. The ${f}_{J}(2220)$ is searched for in the decays to ${K}^{+}{K}^{\ensuremath{-}}$ and ${K}_{S}^{0}{K}_{S}^{0}$. No evidence of this resonance is observed, and 90% confidence level upper limits on the product of the branching fractions for $J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\gamma}{f}_{J}(2220)$ and ${f}_{J}(2220)\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}({K}_{S}^{0}{K}_{S}^{0})$ as a function of spin and helicity are set at the level of ${10}^{\ensuremath{-}5}$, below the central values reported by the Mark III experiment.

Observation of the Rare Decay B+ -> K+ pi0 pi0

Abstract: We report an analysis of charmless hadronic decays of charged B mesons to the final state K+ pi0 pi0, using a data sample of 470.9 +/- 2.8 million BBbar events collected with the BaBar detector at the Upsilon(4S) resonance. We observe an excess of signal events with a significance above 10 standard deviations including systematic uncertainties and measure the branching fraction to be BF(B+ -> K+ pi0 pi0) = (15.5 +/- 1.1 +/- 1.6) x 10^(-6), where the uncertainties are statistical and systematic, respectively.

Evidence for B+ -> tau+ nu_tau decays using hadronic B tags

Abstract: We present a search for the decay B+ --> tau+ nu_tau using 467.8 x 10^6 B B-bar pairs collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC PEP-II B-Factory. We select a sample of events with one completely reconstructed B- in an hadronic decay mode (B- --> D{(*)0}X- and B- --> J/psi X-). We examine the rest of the event to search for a B+ --> tau+ nu_tau decay. We identify the tau+ lepton in the following modes: tau+ --> e+ nu nu, tau+ --> mu+ nu nu, tau+ --> pi+ nu and tau+ --> rho nu. We find an excess of events with respect to expected background, which excludes the null signal hypothesis at the level of 3.3 sigma and can be converted to a branching fraction central value of B( B+ --> tau+ nu_tau )=( 1.80 +0.57 -0.54 (stat.) +-0.26 (syst.)) x 10^{-4}.

Measurement of branching fractions of B decays to K [subscript 1] (1270) pi and K [subscript 1] (1400) pi and determination of the CKM angle Alpha from B [superscript 0]--> a [subscript 1] (1260) (+/-) pi (-/+)

Abstract: Citation Aubert, B. et al. " Measurement of branching fractions of B Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.