984 research outputs found

    Violations of Local Duality in the Heavy Quark Sector

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    We examine the origin of possible failures of the quark-hadron local duality. In particular, we consider a correlator of two currents comprising heavy quark operators, and compare the evaluation by the Operator Product Expansion with the result obtained inserting an infinite set of hadronic states, in the N_c to infinity limit. Whereas the smeared spectral functions agree with each other, their local behaviour is different. The difference manifests itself in the form of a term O(Lambda/epsilon) (epsilon being the residual energy) that is not present in the expansion in powers of Lambda/epsilon predicted by the OPE.Comment: Latex, 14 pages, 1 figur

    QCD sum rules and thermal properties of Charmonium in the vector channel

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    The thermal evolution of the hadronic parameters of charmonium in the vector channel, i.e. the J/psi resonance mass, coupling (leptonic decay constant), total width, and continuum threshold is analyzed in the framework of thermal Hilbert moment QCD sum rules. The continuum threshold s0s_0, as in other hadronic channels, decreases with increasing temperature until the PQCD threshold s_0 = 4, m_Q^2 is reached at T \simeq 1.22T_c (m_Q is the charm quark mass) and the J/psi mass is essentially constant in a wide range of temperatures. The other hadronic parameters behave in a very different way from those of light-light and heavy-light quark systems. The total width grows with temperature up to T \simeq 1.04T_c beyond which it decreases sharply with increasing T. The resonance coupling is also initially constant beginning to increase monotonically around T \simeq T_c. This behavior strongly suggests that the J/psi resonance might survive beyond the critical temperature for deconfinement, in agreement with lattice QCD results.Comment: 4 pages, two figures, contribution to QCD 10, Montpellier 28th June-2nd July 201

    Nuclear Astrophysics in Storage Rings

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    Nuclear reaction cross sections are usually very small in typical astrophysical environments. It has been one of the major challenges of experimental nuclear astrophysics to assess the magnitude of these cross sections in the laboratory. For a successful experiment high luminosity beams are needed. Increasing the target width, one also increases the reaction yields. But, this is of limited use due to multiple scattering in the target. Storage rings are a very good way to overcome these difficulties. In principle, they can be tuned to large luminosities, and have the advantage of crossing the interaction region many times per second (typically one million/s), compensating low density internal gas targets, or low reaction rates in beam-beam collisions. Storage rings are also ideal tools for precise measurements of masses and beta-decay lifetimes of nuclei of relevance for astrophysics.Comment: 14 pages, LaTeX, figures available upon reques

    Christianity, paranormal belief and personality: a study among 13- to 16-year-old pupils in England and Wales

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    Studies concerning the changing landscapes of religiosity and spirituality in the lives of young people in England and Wales draw attention to decline in traditional religiosity and to growth in alternative spiritualities. The present study examined whether such alternative spiritualities occupy the same personality space as traditional religiosity. A sample of 2,950 13- to 16-year-old pupils attending 11 secondary schools in England and Wales completed the Francis Scale of Attitude toward Christianity and an index of paranormal belief, alongside the abbreviated-form Junior Eysenck Personality Questionnaire Revised. The data demonstrated that these two forms of belief were related in different ways to Eysenck's dimensional model of personality space. While attitude toward Christianity occupied the space defined by low psychoticism scores (tendermindedness) and high lie scale scores (social conformity), paranormal belief was related to high psychoticism scores (toughmindedness) and was independent of lie scale scores. These findings support the view that alternative spiritualities may be associated with different personalities

    Implications of unitarity and analyticity for the D\pi form factors

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    We consider the vector and scalar form factors of the charm-changing current responsible for the semileptonic decay D\rightarrow \pi l \nu. Using as input dispersion relations and unitarity for the moments of suitable heavy-light correlators evaluated with Operator Product Expansions, including O(\alpha_s^2) terms in perturbative QCD, we constrain the shape parameters of the form factors and find exclusion regions for zeros on the real axis and in the complex plane. For the scalar form factor, a low energy theorem and phase information on the unitarity cut are also implemented to further constrain the shape parameters. We finally propose new analytic expressions for the DπD\pi form factors, derive constraints on the relevant coefficients from unitarity and analyticity, and briefly discuss the usefulness of the new parametrizations for describing semileptonic data.Comment: 10 pages, 7 figures, uses EPJ style files: expanded version of v1 with extended discussion, additional analysis, explanation, figure and references; corresponds to EPJA versio

    Branch-and-lift algorithm for deterministic global optimization in nonlinear optimal control

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    This paper presents a branch-and-lift algorithm for solving optimal control problems with smooth nonlinear dynamics and potentially nonconvex objective and constraint functionals to guaranteed global optimality. This algorithm features a direct sequential method and builds upon a generic, spatial branch-and-bound algorithm. A new operation, called lifting, is introduced, which refines the control parameterization via a Gram-Schmidt orthogonalization process, while simultaneously eliminating control subregions that are either infeasible or that provably cannot contain any global optima. Conditions are given under which the image of the control parameterization error in the state space contracts exponentially as the parameterization order is increased, thereby making the lifting operation efficient. A computational technique based on ellipsoidal calculus is also developed that satisfies these conditions. The practical applicability of branch-and-lift is illustrated in a numerical example. © 2013 Springer Science+Business Media New York

    Low-Energy Direct Capture in the 8Li(n,gamma)9Li and 8B(p,gamma)9C Reactions

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    The cross sections of the 8Li(n,gamma)9Li and 8B(p,gamma)9C capture reactions have been analyzed using the direct capture model. At low energies which is the astrophysically relevant region the capture process is dominated by E1 transitions from incoming s-waves to bound p-states. The cross sections of both mirror reactions can be described simultaneously with consistent potential parameters, whereas previous calculations have overestimated the capture cross sections significantly. However, the parameters of the potential have to be chosen very carefully because the calculated cross section of the 8Li(n,gamma)9Li reaction depends sensitively on the potential strength.Comment: 6 pages, 5 figures, Phys. Rev. C, accepte

    Improved Holographic QCD

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    We provide a review to holographic models based on Einstein-dilaton gravity with a potential in 5 dimensions. Such theories, for a judicious choice of potential are very close to the physics of large-N YM theory both at zero and finite temperature. The zero temperature glueball spectra as well as their finite temperature thermodynamic functions compare well with lattice data. The model can be used to calculate transport coefficients, like bulk viscosity, the drag force and jet quenching parameters, relevant for the physics of the Quark-Gluon Plasma.Comment: LatEX, 65 pages, 28 figures, 9 Tables. Based on lectures given at several Schools. To appear in the proceedinds of the 5th Aegean School (Milos, Greece

    Probing exotic phenomena at the interface of nuclear and particle physics with the electric dipole moments of diamagnetic atoms: A unique window to hadronic and semi-leptonic CP violation

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    The current status of electric dipole moments of diamagnetic atoms which involves the synergy between atomic experiments and three different theoretical areas -- particle, nuclear and atomic is reviewed. Various models of particle physics that predict CP violation, which is necessary for the existence of such electric dipole moments, are presented. These include the standard model of particle physics and various extensions of it. Effective hadron level combined charge conjugation (C) and parity (P) symmetry violating interactions are derived taking into consideration different ways in which a nucleon interacts with other nucleons as well as with electrons. Nuclear structure calculations of the CP-odd nuclear Schiff moment are discussed using the shell model and other theoretical approaches. Results of the calculations of atomic electric dipole moments due to the interaction of the nuclear Schiff moment with the electrons and the P and time-reversal (T) symmetry violating tensor-pseudotensor electron-nucleus are elucidated using different relativistic many-body theories. The principles of the measurement of the electric dipole moments of diamagnetic atoms are outlined. Upper limits for the nuclear Schiff moment and tensor-pseudotensor coupling constant are obtained combining the results of atomic experiments and relativistic many-body theories. The coefficients for the different sources of CP violation have been estimated at the elementary particle level for all the diamagnetic atoms of current experimental interest and their implications for physics beyond the standard model is discussed. Possible improvements of the current results of the measurements as well as quantum chromodynamics, nuclear and atomic calculations are suggested.Comment: 46 pages, 19 tables and 16 figures. A review article accepted for EPJ

    Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events

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    The B0B^0-Bˉ0\bar B^0 oscillation frequency has been measured with a sample of 23 million \B\bar B pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we select events in which both B mesons decay semileptonically and use the charge of the leptons to identify the flavor of each B meson. A simultaneous fit to the decay time difference distributions for opposite- and same-sign dilepton events gives Δmd=0.493±0.012(stat)±0.009(syst)\Delta m_d = 0.493 \pm 0.012{(stat)}\pm 0.009{(syst)} ps−1^{-1}.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
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