320 research outputs found

    Semileptonic Bq→Dq∗lνB_{q}\to D^{\ast}_{q}l\nu (q=s,d,u)(q=s, d, u) transitions in QCD

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    The form factors relevant to Bq→Dq∗(JP=1−)ℓνB_{q}\to D^{\ast}_{q}(J^{P}=1^{-})\ell\nu (q=s,d,u)(q=s, d, u) decays are calculated in the framework of the three point QCD sum rules approach. The heavy quark effective theory prediction of the form factors are obtained. The total decay width and branching ratio for these decays are also evaluated using the q2q^2 dependencies of these form factors.Comment: 4 pages, 4 figures and 3 tables. To be published in the proceedings of the 14th International QCD Conference (QCD 08), Montpellier, France, 7-12 July 200

    Double-Lepton Polarization Asymmetries and Polarized Forward Backward Asymmetries in the Rare b \to s \ell^+ \ell^- Decays in a Single Universal Extra Dimension Scenario

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    We study the double-lepton polarization asymmetries and single and double-lepton polarization forward backward asymmetries of the rare b \to s \ell^+ \ell^- mode within the Standard Model and in the Appelquist-Cheng-Dobrescu model, which is a new physics scenario with a single universal extra dimension. In particular, we examine the sensitivity of the observables to the radius R of the compactified extra-dimension, which is the new parameter in this new physics model.Comment: 20 Pages, 15 Figures and 1 Tabl

    Semileptonic Bq→Dq∗lνB_{q}\to D^{\ast}_{q}l\nu (q=s,d,u)(q=s, d, u) Decays in QCD Sum Rules

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    The form factors relevant to Bq→Dq∗(JP=1−)ellνB_{q}\to D^{\ast}_{q}(J^{P}=1^{-}) ell\nu (q=s,d,u)(q=s, d, u) decays are calculated in the framework of the three point QCD sum rules approach. The heavy quark effective theory prediction of the form factors as well as 1/mb1/m_{b} corrections to those form factors are obtained. A comparison of the results for the ratio of form factors at zero recoil limit and other values of q2q^{2} with the predictions of the subleading Isgur-Wise form factor application for B→D∗ℓνB\to D^{\ast}\ell\nu is presented. The total decay width and branching ratio for these decays are also evaluated using the q2q^2 dependencies of these form factors. The results are in good agreement with the constituent quark meson model and existing experimental data. The q=sq=s case can also be detected at LHC in the near future.Comment: 28 Pages, 6 Figures and 9 Table

    Flavor Changing Neutral Currents Transition of the ΣQ\Sigma_{Q} to Nucleon in Full QCD and Heavy Quark Effective Theory

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    The loop level flavor changing neutral currents transitions of the Σb→nl+l−\Sigma_{b}\to n l^+l^- and Σc→pl+l−\Sigma_{c}\to p l^+l^- are investigated in full QCD and heavy quark effective theory in the light cone QCD sum rules approach. Using the most general form of the interpolating current for ΣQ\Sigma_{Q}, Q=bQ=b or cc, as members of the recently discovered sextet heavy baryons with spin 1/2 and containing one heavy quark, the transition form factors are calculated using two sets of input parameters entering the nucleon distribution amplitudes, namely, QCD sum rules and lattice QCD inputs. The obtained results are used to estimate the decay rates of the corresponding transitions. Since such type transitions occurred at loop level in the standard model, they can be considered as good candidates to search for the new physics effects beyond the SM.Comment: 18 Pages and 13 Table

    Determinants of private consumption

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    This paper looks at the evolution of consumption theory over time and critically examines the widely accepted permanent income / life cycle hypotheses concerning consumer behaviour in terms of the empirical evidence. Attention is also devoted to the role of time horizon, time preference and capital market imperfections in determining the consumption / savings split of individual consumers. The paper points out the forecasting inadequacies of an essentially Keynesian framework due to its insufficient attention to expectations and forward looking behaviour. The likely key influences on consumption trends in the Community over the medium to long run are examined including the reaction of consumption to both ongoing budgetary consolidation and financial liberalisation, the impact of taxation and social welfare reforms and finally the effect of demographic changes.consumption, consumers

    Semileptonic Λb,c\Lambda_{b,c} to Nucleon Transitions in Full QCD at Light Cone

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    The tree level semileptonic Λb→plν\Lambda_{b}\to pl\nu and Λc→nlν\Lambda_{c}\to nl\nu transitions are investigated using the light cone QCD sum rules approach in full theory. The spin--1/2, ΛQ\Lambda_{Q} baryon with Q=bQ=b or cc, is considered by the most general form of its interpolating current. The time ordering product of the initial and transition currents is expanded in terms of the nucleon distribution amplitudes with different twists. Considering two sets of independent input parameters entering to the nucleon wave functions, namely, QCD sum rules and Lattice QCD parameters, the related form factors and their heavy quark effective theory limits are calculated and compared with the existing predictions of other approaches. It is shown that our results satisfy the heavy quark symmetry relations for lattice input parameters and b case exactly and the maximum violation is for charm case and QCD sum rules input parameters. The obtained form factors are used to compute the transition rates both in full theory and heavy quark effective theory. A comparison of the results on decay rate of Λb→plν\Lambda_{b}\to pl\nu with those predicted by other phenomenological methods or the same method in heavy quark effective theory with different interpolating current and distribution amplitudes of the Λb\Lambda_{b} is also presented.Comment: 18 Pages and 16 Table

    Performance Evaluation of Homogeneous Charge Compression Ignition Combustion Engine â A Review

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    The development of HCCI combustion technology has been drawing a great deal of attention from researchers. This survey explains ongoing research methodologies and results. HCCI combustion, other than conventional combustion, is purely based on chemical kinetics. At present the automobile sector faces the problem of emissions and needs to develop clean technologies. However, HCCI operation still has issues such as ignition control, combustion phasing control, operating range control, cold start, and UHC (unburned hydrocarbon) and CO (carbon monoxide) emissions. The challenge is to overcome these problems without compromising other engine parameters and performance. For HCCI, the mixture preparation is especially important, while the compression ratio, IVC (inlet valve closure) timing, inlet pressure, inlet temperature and EGR play a very prominent role in controlling it. This paper will go through a detailed discussion of all the above conditions

    g_phi-pion-gamma coupling constant in light cone QCD sum rules

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    The coupling constant of g_phi-pion-gamma decay is calculated using light cone QCD sum rules. A comparison of our result with the ones existing in the literature is presented.Comment: 9 pages, 2 figure

    Scalar Quarkonia at Finite Temperature

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    Masses and decay constants of the scalar quarkonia, χQ0(Q=b,c)\chi_{Q0} (Q=b,c) with quantum numbers IG(JPC)=0+(0++)I^G(J^{PC})=0^{+}(0^{++}) are calculated in the framework of the QCD sum rules approach both in vacuum and finite temperature. The masses and decay constants remain unchanged up to T≃100 MeVT\simeq100~MeV but they start to diminish with increasing the temperature after this point. At near the critic or deconfinement temperature, the decay constants reach approximately to 25% of their values in vacuum, while the masses are decreased about 6% and 23% for bottom and charm cases, respectively. The results at zero temperature are in a good consistency with the existing experimental values and predictions of the other nonperturbative approaches. Our predictions on the decay constants in vacuum as well as the behavior of the masses and decay constants with respect to the temperature can be checked in the future experiments.Comment: 12 Pages, 9 Figures and 2 Table
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