984 research outputs found
Violations of Local Duality in the Heavy Quark Sector
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
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 , 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
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
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
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
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
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
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
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
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
The - 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 ps.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
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