5,597 research outputs found

    Measurement of CP Violation at the ΄(4S)\Upsilon(4S) without Time Ordering or Δt\Delta t

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    I derive the expressions for the CP-violating asymmetry arising from interference between mixed and direct decays in the Upsilon(4S) system, for the case in which only one of the B decay times is observed, integrating over the decay time of the other B. I observe that neither the difference of the decay times Delta t, nor even their time-ordering, need be detected. A technique for measurement of the CP-violating weak decay parameter sin(2beta) is described which exploits this observation.Comment: 9 pages postscript, also available through http://w4.lns.cornell.edu/public/CLN

    Operator Product Expansion for Exclusive Decays: B^+ ->Ds^+ e+e- and B^+ -> Ds^{*+} e+e-

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    The decays B+→Ds,d+e+e−B^+\to D_{s,d}^+e^+e^- and B+→Ds,d∗+e+e−B^+\to D_{s,d}^{*+}e^+e^- proceed through a weak and an electromagnetic interaction. This is a typical ``long distance'' process, usually difficult to compute systematically. We propose that over a large fraction of phase space a combination of an operator product and heavy quark expansions effectively turns this process into one in which the weak and electromagnetic interactions occur through a local operator. Moreover, we use heavy quark spin symmetry to relate all the local operators that appear in leading order of the operator expansion to two basic ones. We use this operator expansion to estimate the decay rates for B+→Ds,d(∗)+e+e−B^+\to D_{s,d}^{(*)+}e^+e^-.Comment: 4 pages, 1 figure, Latex, published version in PR

    N-Acetylcysteine Serves as Substrate of 3-Mercaptopyruvate Sulfurtransferase and Stimulates Sulfide Metabolism in Colon Cancer Cells

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    Hydrogen sulfide (H2S) is an endogenously produced signaling molecule. The enzymes 3-mercaptopyruvate sulfurtransferase (MST), partly localized in mitochondria, and the inner mitochondrial membrane-associated sulfide:quinone oxidoreductase (SQR), besides being respectively involved in the synthesis and catabolism of H2S, generate sulfane sulfur species such as persulfides and polysulfides, currently recognized as mediating some of the H2S biological effects. Reprogramming of H2S metabolism was reported to support cellular proliferation and energy metabolism in cancer cells. As oxidative stress is a cancer hallmark and N-acetylcysteine (NAC) was recently suggested to act as an antioxidant by increasing intracellular levels of sulfane sulfur species, here we evaluated the effect of prolonged exposure to NAC on the H2S metabolism of SW480 colon cancer cells. Cells exposed to NAC for 24 h displayed increased expression and activity of MST and SQR. Furthermore, NAC was shown to: (i) persist at detectable levels inside the cells exposed to the drug for up to 24 h and (ii) sustain H2S synthesis by human MST more effectively than cysteine, as shown working on the isolated recombinant enzyme. We conclude that prolonged exposure of colon cancer cells to NAC stimulates H2S metabolism and that NAC can serve as a substrate for human MST

    B Physics at the Tevatron: Run II and Beyond

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    This report provides a comprehensive overview of the prospects for B physics at the Tevatron. The work was carried out during a series of workshops starting in September 1999. There were four working groups: 1) CP Violation, 2) Rare and Semileptonic Decays, 3) Mixing and Lifetimes, 4) Production, Fragmentation and Spectroscopy. The report also includes introductory chapters on theoretical and experimental tools emphasizing aspects of B physics specific to hadron colliders, as well as overviews of the CDF, D0, and BTeV detectors, and a Summary.Comment: 583 pages. Further information on the workshops, including transparencies, can be found at the workshop's homepage: http://www-theory.lbl.gov/Brun2/. The report is also available in 2-up http://www-theory.lbl.gov/Brun2/report/report2.ps.gz or chapter-by-chapter http://www-theory.lbl.gov/Brun2/report

    The Semileptonic Decays D→π(ρ)eÎœD\to \pi(\rho) e \nu and B→π(ρ)eÎœB\to \pi (\rho) e \nu from QCD Sum Rules

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    We investigate the semileptonic decays of B and D mesons into π\pi and ρ\rho mesons, respectively, by means of QCD sum rules. We find that for the vector formfactors involved the pole dominance hypothesis is valid to good accuracy with pole masses in the expected range. Pole dominance, however, does not apply to the axial formfactors which results in specific predictions for the predominant polarization of the ρ\rho meson and the shape of the lepton spectrum. For the total decay rates we find Γ(Bˉ0→π+e−Μˉ)=(5.1±1.1) ∣Vub∣2 1012 s−1\Gamma (\bar B^0 \to \pi^+ e^- \bar\nu) = (5.1\pm 1.1)\,|V_{ub}|^2\, 10^{12}\,{\rm s^{-1}}, Γ(D0→π−e+Îœ)=(8.0±1.7) ∣Vcd∣2 1010 s−1\Gamma ( D^0 \to \pi^- e^+ \nu) = (8.0\pm 1.7)\,|V_{cd}|^2\, 10^{10}\,{\rm s^{-1}}, Γ(Bˉ0→ρ+e−Μˉ)=(1.2±0.4 ) ∣Vub∣2 1013 s−1\Gamma (\bar B^0 \to \rho^+ e^- \bar\nu) = (1.2\pm 0.4\,)\,|V_{ub}|^2\, 10^{13}\,{\rm s^{-1}} and Γ(D0→ρ−e+Îœ)=(2.4±0.7) ∣Vcd∣2 109 s−1\Gamma (D^0 \to \rho^- e^+\nu) = (2.4\pm 0.7)\,|V_{cd}|^2\, 10^{9}\,{\rm s^{-1}}.Comment: 23 pages, 12 figures included as uu-encoded file, needs REVTEX, TUM--T31--39/9

    Determination of the Jet Energy Scale at the Collider Detector at Fermilab

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    A precise determination of the energy scale of jets at the Collider Detector at Fermilab at the Tevatron ppˉp\bar{p} collider is described. Jets are used in many analyses to estimate the energies of partons resulting from the underlying physics process. Several correction factors are developed to estimate the original parton energy from the observed jet energy in the calorimeter. The jet energy response is compared between data and Monte Carlo simulation for various physics processes, and systematic uncertainties on the jet energy scale are determined. For jets with transverse momenta above 50 GeV the jet energy scale is determined with a 3% systematic uncertainty

    A mild alkali treated jute fibre controlling the hydration behaviour of greener cement paste

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    To reduce the antagonistic effect of jute fibre on the setting and hydration of jute reinforced cement, modified jute fibre reinforcement would be a unique approach. The present investigation deals with the effectiveness of mild alkali treated (0.5%) jute fibre on the setting and hydration behaviour of cement. Setting time measurement, hydration test and analytical characterizations of the hardened samples (viz., FTIR, XRD, DSC, TGA and free lime estimation) were used to evaluate the effect of alkali treated jute fibre. From the hydration test, the time (t) required to reach maximum temperature for the hydration of control cement sample is estimated to be 860 min, whilst the time (t) is measured to be 1040 min for the hydration of a raw jute reinforced cement sample. However, the time (t) is estimated to be 1020 min for the hydration of an alkali treated jute reinforced cement sample. Additionally, from the analytical characterizations, it is determined that fibre-cement compatibility is increased and hydration delaying effect is minimized by using alkali treated jute fibre as fibre reinforcement. Based on the analyses, a model has been proposed to explain the setting and hydration behaviour of alkali treated jute fibre reinforced cement composite

    The Rare Decay B→K∗γB\to K^{\ast}\gamma: A More Precise Calculation

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    Efforts to predict the rare exclusive decay B→K∗γB\to K^{\ast}\gamma from the well known inclusive decay b→sÎłb\to s\gamma are frustrated by the effect of the large recoil momentum. We show how to reduce the large uncertainty in calculating this decay by relating B→K∗γB\to K^{\ast}\gamma to the semileptonic process B→ρeΜˉB\to\rho e\bar{\nu} using the heavy-quark symmetry in B decays and SU(3) flavor symmetry. A direct measurement of the q2q^{2}-spectrum for the semileptonic decay can provide accurate information for the exclusive rare decay.Comment: 15 pages, UTPT-93-02, in REVTEX with one figure in ep

    A search for resonant production of ttˉt\bar{t} pairs in $4.8\ \rm{fb}^{-1}ofintegratedluminosityof of integrated luminosity of p\bar{p}collisionsat collisions at \sqrt{s}=1.96\ \rm{TeV}$

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    We search for resonant production of tt pairs in 4.8 fb^{-1} integrated luminosity of ppbar collision data at sqrt{s}=1.96 TeV in the lepton+jets decay channel, where one top quark decays leptonically and the other hadronically. A matrix element reconstruction technique is used; for each event a probability density function (pdf) of the ttbar candidate invariant mass is sampled. These pdfs are used to construct a likelihood function, whereby the cross section for resonant ttbar production is estimated, given a hypothetical resonance mass and width. The data indicate no evidence of resonant production of ttbar pairs. A benchmark model of leptophobic Z \rightarrow ttbar is excluded with m_{Z'} < 900 GeV at 95% confidence level.Comment: accepted for publication in Physical Review D Sep 21, 201
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