3,817 research outputs found
Improving Extractions of |Vcb| and the b Quark Mass from Semileptonic Inclusive B Decay
Recent advances in improving extractions of |Vcb| and m_b from spectra of
semileptonic inclusive B decay are reported. Results of a general moment
analysis of the lepton energy spectrum and the hadronic invariant mass spectrum
are summarized. The calculation of the general O(\alpha_s) structure functions
for semileptonic B decay is reported, which has allowed the calculation of the
O(\alpha_s Lambda_{QCD} /m_b) terms for the hadronic invariant mass moments to
be carried out. Recent theoretical advances and improvements in experimental
data has allowed extractions of the CKM element |Vcb| to improve to the 2%
level.Comment: 8 pages, 2 figures. Talk given at MRST2004, May 12-14, Concordia,
Montrea
Radiative transitions of and
We study radiative decays of and using
light-cone QCD sum rules. In particular, we consider the decay modes
and and evaluate the hadronic parameters in the transition
amplitudes analyzing correlation functions of scalar, pseudoscalar, vector and
axial-vector quark currents. In the case of
we also consider determinations based on two different correlation functions in
HQET. The decay widths turn out to be different than previous estimates
obtained by other methods; the results favour the interpretation of
and as ordinary mesons.Comment: RevTex, 23 pages, 9 eps figure
Microstructure and chemical composition of Roman orichalcum coins emitted after the monetary reform of Augustus (23 B.C.)
A collection of ancient Roman orichalcum coins, i.e., a copper-zinc alloy, minted under the reigns from Caesar to Domitianus, have been characterised using scanning electron microscopy (SEM-EDS) and electron microprobe analysis (EMPA). We studied, for the first time, coins emitted by Romans after the reforms of Augustus (23 B.C.) and Nero (63-64 A.D). These coins, consisting of asses, sestertii, dupondii and semisses, were analysed using non- and invasive analyses, aiming to explore microstructure, corrosive process and to acquire quantitative chemical analysis. The results revealed that the coins are characterized by porous external layers, which are affected by dezincification and decuprification processes. As pictured by the X-ray maps, the elemental distribution of Cu and Zn shows patterns of depletion that in some cases penetrate in deep up to 1 mm. The composition of the un-corroded nucleus is a Cu-Zn alloy containing up to 30% of Zn, typical of coins produced via cementation process
Review of Heavy Quark Physics - theory
Recent progress in the theory of B-meson decays is reviewed with emphasis on
the aspects related to the B-factory data.Comment: 15 pages; Invited Plenary Talk at the 32nd International Conference
on High Energy Physics (ICHEP'04), Beijing, China, Aug. 16-22, 200
Semileptonic and Rare -meson transitions in a QCD relativistic potential model
Using a QCD relativistic potential model, previously applied to the
calculation of the heavy meson leptonic constants, we evaluate the form factors
governing the exclusive decays , and . In our approach the heavy meson is described as a
bound state, whose wave function is solution of the relativistic Salpeter
equation, with an instantaneous potential displaying Coulombic behaviour at
small distances and linear behaviour at large distances. The light vector meson
is described by using a vector current interpolating field, according to the
Vector Meson Dominance assumption. A Pauli-Villars regularized propagator is
assumed for the quarks not constituting the heavy meson. Our procedure allows
to avoid the description of the light meson in terms of wave function and
constituent quarks, and consequently the problem of boosting the light meson
wave function.
Assuming as an input the experimental results on , we
evaluate all the form factors describing the semileptonic and
rare transitions. The overall comparison with the data, whenever available, is
satisfactory.Comment: Latex, 19 pages, 3 figure
Log-Sobolev inequalities and hypercontractivity for Ornstein-Uhlenbeck evolution operators in infinite dimensions
In an infinite dimensional separable Hilbert space , we study the
realizations of Ornstein-Uhlenbeck evolution operators \pst in the spaces
L^p(X,\g_t), \{\g_t\}_{t\in\R} being the unique evolution system of
measures for \pst in . We prove hyperconctractivity results, relying on
suitable Log-Sobolev estimates. Among the examples we consider the transition
evolution operator of a non autonomous stochastic parabolic PDE
SCET sum rules for B->P and B->V transition form factors
We investigate sum rules for heavy-to-light transition form factors at large
recoil derived from correlation functions with interpolating currents for light
pseudoscalar or vector fields in soft-collinear effective theory (SCET). We
consider both, factorizable and non-factorizable contributions at leading power
in the Lambda/m_b expansion and to first order in the strong coupling constant
alpha_s, neglecting contributions from 3-particle distribution amplitudes in
the B-meson. We pay particular attention to various sources of parametric and
systematic uncertainties. We also discuss certain form factor ratios where part
of the hadronic uncertainties related to the B-meson distribution amplitude and
to logarithmically enhanced alpha_s corrections cancel.Comment: 27 pages, 19 figures, minor corrections, matches journal versio
New meson spectroscopy with open charm and beauty
All the available experimental information on open charm and beauty mesons is
used to classify the observed states in heavy quark doublets. The masses of
some of the still unobserved states are predicted, in particular in the beauty
sector.
Adopting an effective Lagrangian approach based on the heavy quark and chiral
symmetry, individual decay rates and ratios of branching fractions are
computed, with results useful to assign the quantum numbers to recently
observed charmed states which still need to be properly classified.
Implications and predictions for the corresponding beauty mesons are provided.
The experimental results are already copious, and are expected to grow up
thanks to the experiments at the LHC and to the future high-luminosity flavour
and facilities.Comment: RevTex, 15 pages, 1 figure. Corrected Equations (8) and (9
Adiabatic quantum dynamics of a random Ising chain across its quantum critical point
We present here our study of the adiabatic quantum dynamics of a random Ising
chain across its quantum critical point. The model investigated is an Ising
chain in a transverse field with disorder present both in the exchange coupling
and in the transverse field. The transverse field term is proportional to a
function which, as in the Kibble-Zurek mechanism, is linearly
reduced to zero in time with a rate , , starting
at from the quantum disordered phase () and ending
at in the classical ferromagnetic phase (). We first analyze
the distribution of the gaps -- occurring at the critical point --
which are relevant for breaking the adiabaticity of the dynamics. We then
present extensive numerical simulations for the residual energy
and density of defects at the end of the annealing, as a function of
the annealing inverse rate . %for different lenghts of the chain. Both
the average and are found to behave
logarithmically for large , but with different exponents, with , and
. We propose a mechanism for
-behavior of based on the Landau-Zener
tunneling theory and on a Fisher's type real-space renormalization group
analysis of the relevant gaps. The model proposed shows therefore a
paradigmatic example of how an adiabatic quantum computation can become very
slow when disorder is at play, even in absence of any source of frustration.Comment: 10 pages, 11 figures; v2: added references, published versio
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