351 research outputs found

    Two-loop light fermion contribution to Higgs production and decays

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    We compute the electroweak corrections due to the light fermions to the production cross section σ(gg→H)\sigma(g g \to H) and to the partial decay widths Γ(H→γγ)\Gamma (H \to \gamma \gamma) and Γ(H→gg)\Gamma (H \to g g). We present analytic results for these corrections that are expressed in terms of Generalized Harmonic Polylogarithms. We find that for the gluon fusion production cross section and for the decay width Γ(H→gg)\Gamma (H \to g g) the corrections are large in the Higgs mass region below 160 GeV where they reach up to 9% of the lowest order term. For the decay width Γ(H→γγ)\Gamma (H \to \gamma \gamma) the corrections for Higgs mass above 160 GeV can reach −-10% of the lowest order term.Comment: 12 pages, 4 figure

    The dissociation of the J/psi by light mesons and chiral symmetry

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    The implication of chiral symmetry for the pion-induced dissociation of the J/psi is examined in detail. It is shown how the low-energy dynamics of pions, constrained by chiral symmetry, affect the dissociation cross-section. The derived soft-pion theorem is then integrated into a Lagrangian model which includes also abnormal parity content and chiral-symmetric form factors. Dissociation by the rho meson is also considered.Comment: 31 pages, 6 figures. Minor revision

    RG-improved single-particle inclusive cross sections and forward-backward asymmetry in ttˉt\bar t production at hadron colliders

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    We use techniques from soft-collinear effective theory (SCET) to derive renormalization-group improved predictions for single-particle inclusive (1PI) observables in top-quark pair production at hadron colliders. In particular, we study the top-quark transverse-momentum and rapidity distributions, the forward-backward asymmetry at the Tevatron, and the total cross section at NLO+NNLL order in resummed perturbation theory and at approximate NNLO in fixed order. We also perform a detailed analysis of power corrections to the leading terms in the threshold expansion of the partonic hard-scattering kernels. We conclude that, although the threshold expansion in 1PI kinematics is susceptible to numerically significant power corrections, its predictions for the total cross section are in good agreement with those obtained by integrating the top-pair invariant-mass distribution in pair invariant-mass kinematics, as long as a certain set of subleading terms appearing naturally within the SCET formalism is included.Comment: 55 pages, 14 figures, 6 table

    Charged lepton Flavor Violation in Supersymmetry with Bilinear R-Parity Violation

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    The simplest unified extension of the Minimal Supersymmetric Standard Model with bi-linear R-parity violation naturally predicts a hierarchical neutrino mass spectrum, suitable to explain atmospheric and solar neutrino fluxes. We study whether the individual violation of the lepton numbers L_{e,mu,tau} in the charged sector can lead to measurable rates for BR(mu->e gamma)and $BR(tau-> mu gamma). We find that some of the R-parity violating terms that are compatible with the observed atmospheric neutrino oscillations could lead to rates for mu->e gamma measurable in projected experiments. However, the Delta m^2_{12} obtained for those parameters is too high to be compatible with the solar neutrino data, excluding therefore the possibility of having measurable rates for mu->e gamma in the model.Comment: 29 pages, 8 figures. Constraint from solar neutrino data included, conclusions changed respect v

    Ward Identities, B-> \rho Form Factors and |V_ub|

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    The exclusive FCNC beauty semileptonic decay B-> \rho is studied using Ward identities in a general vector meson dominance framework, predicting vector meson couplings involved. The long distance contributions are discussed which results to obtain form factors and |V_ub|. A detailed comparison is given with other approaches.Comment: 30 pages+four postscript figures, an Appendix adde

    Identification of four families of yCCR4- and Mg(2+)-dependent endonuclease-related proteins in higher eukaryotes, and characterization of orthologs of yCCR4 with a conserved leucine-rich repeat essential for hCAF1/hPOP2 binding

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    BACKGROUND: The yeast yCCR4 factor belongs to the CCR4-NOT transcriptional regulatory complex, in which it interacts, through its leucine-rich repeat (LRR) motif with yPOP2. Recently, yCCR4 was shown to be a component of the major cytoplasmic mRNA deadenylase complex, and to contain a fold related to the Mg(2+)-dependent endonuclease core. RESULTS: Here, we report the identification of nineteen yCCR4-related proteins in eukaryotes (including yeast, plants and animals), which all contain the yCCR4 endonuclease-like fold, with highly conserved CCR4-specific residues. Phylogenetic and genomic analyses show that they form four distinct families, one of which contains the yCCR4 orthologs. The orthologs in animals possess a leucine-rich repeat domain. We show, using two-hybrid and far-Western assays, that the human member binds to the human yPOP2 homologs, i.e. hCAF1 and hPOP2, in a LRR-dependent manner. CONCLUSIONS: We have identified the mammalian orthologs of yCCR4 and have shown that the human member binds to the human yPOP2 homologs, thus strongly suggesting conservation of the CCR4-NOT complex from yeast to human. All members of the four identified yCCR4-related protein families show stricking conservation of the endonuclease-like catalytic motifs of the yCCR4 C-terminal domain and therefore constitute a new family of potential deadenylases in mammals

    The clinical global impression scale and the influence of patient or staff perspective on outcome

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    <p>Abstract</p> <p>Background</p> <p>Since its first publication, the Clinical Global Impression Scale (CGI) has become one of the most widely used assessment instruments in psychiatry. Although some conflicting data has been presented, studies investigating the CGI's validity have only rarely been conducted so far. It is unclear whether the improvement index CGI-I or a difference score of the severity index CGI-S<sub> dif </sub>is more valid in depicting clinical change. The current study examined the validity of these two measures and investigated whether therapists' CGI ratings correspond to the view the patients themselves have on their condition.</p> <p>Methods</p> <p>Thirty-one inpatients of a German psychotherapeutic hospital suffering from a major depressive disorder (age M = 45.3, SD = 17.2; 58.1% women) participated. Patients filled in the Beck Depression Inventory (BDI). CGI-S and CGI-I were rated from three perspectives: the treating therapist (THER), the team of therapists involved in the patient's treatment (TEAM), and the patient (PAT). BDI and CGI-S were filled in at admission and discharge, CGI-I at discharge only. Data was analysed using effect sizes, Spearman's <it>ρ </it>and intra-class correlations (ICC).</p> <p>Results</p> <p>Effect sizes between CGI-I and CGI-S <sub>dif </sub>ratings were large for all three perspectives with substantially higher change scores on CGI-I than on CGI-S <sub>dif</sub>. BDI<sub> dif </sub>correlated moderately with PAT ratings, but did not correlate significantly with TEAM or THER ratings. Congruence between CGI-ratings from the three perspectives was low for CGI-S <sub>dif </sub>(ICC = .37; Confidence Interval [CI] .15 to .59; <it>F</it><sub>30,60 </sub>= 2.77, <it>p </it>< .001; mean <it>ρ </it>= 0.36) and moderate for CGI-I (ICC = .65 (CI .47 to .80; <it>F</it><sub>30,60 </sub>= 6.61, <it>p </it>< .001; mean <it>ρ </it>= 0.59).</p> <p>Conclusions</p> <p>Results do not suggest a definite recommendation for whether CGI-I or CGI-S <sub>dif </sub>should be used since no strong evidence for the validity of neither of them could be found. As congruence between CGI ratings from patients' and staff's perspective was not convincing it cannot be assumed that CGI THER or TEAM ratings fully represent the view of the patient on the severity of his impairment. Thus, we advocate for the incorporation of multiple self- and clinician-reported scales into the design of clinical trials in addition to CGI in order to gain further insight into CGI's relation to the patients' perspective.</p

    Bioethical and medico-legal implications of withdrawing artificial nutrition and hydration from adults in critical care

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    The withdrawal of artificial nutrition and hydration or other life-sustaining treatments is a clinical decision, made in ICUs or in other settings, involving patients suffering from serious and irreversible diseases or impaired consciousness. Such clinical decisions must be made in the best interests of the patient, and must respect the wishes previously expressed by patients, laid down in their wills, in advance directives or in information passed on by relatives or legally appointed health-care agents, and in observance of common bioethical and legal rules in individual nations. Intensivists who are expert in the management of lifesustaining treatments are also involved in deciding when to withdraw futile therapies and instigate end-of-life care procedures for dying patients, with the sole aim of providing comfort and ensuring that suffering is not prolonged unnecessaril
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