968 research outputs found
Role of "Intrinsic Charm" in Semi-Leptonic B-Meson Decays
We discuss the role of so-called "intrinsic-charm" operators in semi-leptonic
B-meson decays, which appear first at order 1/m_b^3 in the heavy quark
expansion. We show by explicit calculation that -- at scales mu <= m_c -- the
contributions from "intrinsic-charm" effects can be absorbed into
short-distance coefficient functions multiplying, for instance, the Darwin
term. Then, the only remnant of "intrinsic charm" are logarithms of the form
ln(m_c^2/m_b^2), which can be resummed by using renormalization-group
techniques. As long as the dynamics at the charm-quark scale is perturbative,
alpha_s(m_c) << 1, this implies that no additional non-perturbative matrix
elements aside from the Darwin and the spin-orbit term have to be introduced at
order 1/m_b^3. Hence, no sources for additional hadronic uncertainties have to
be taken into account. Similar arguments may be made for higher orders in the
1/m_b expansion.Comment: 14 pages, 1 figure, uses slashed.sty, slight modifications to match
published versio
A Survey of Lepton Number Violation Via Effective Operators
We survey 129 lepton number violating effective operators, consistent with
the minimal Standard Model gauge group and particle content, of mass dimension
up to and including eleven. Upon requiring that each one radiatively generates
the observed neutrino masses, we extract an associated characteristic cutoff
energy scale which we use to calculate other observable manifestations of these
operators for a number of current and future experimental probes, concentrating
on lepton number violating phenomena. These include searches for neutrinoless
double-beta decay and rare meson, lepton, and gauge boson decays. We also
consider searches at hadron/lepton collider facilities in anticipation of the
LHC and the future ILC. We find that some operators are already disfavored by
current data, while more are ripe to be probed by next-generation experiments.
We also find that our current understanding of lepton mixing disfavors a subset
of higher dimensional operators. While neutrinoless double-beta decay is the
most promising signature of lepton number violation for the majority of
operators, a handful is best probed by other means. We argue that a combination
of constraints from various independent experimental sources will help to
pinpoint the ``correct'' model of neutrino mass, or at least aid in narrowing
down the set of possibilities.Comment: 34 pages, 10 eps figures, 1 tabl
Students' mental prototypes for functions and graphs
This research study investigates the concept of function developed by students studying English A-level mathematics. It shows that, while students may be able to use functions in their practical mathematics, their grasp of the theoretical nature of the function concept may be tenuous and inconsistent. The hypothesis is that students develop prototypes for the function concept in much the same way as they develop prototypes for concepts in everyday life. The definition of the function concept, though given in the curriculum, is not stressed and proves to be inoperative, with their understanding of the concept reliant on properties of familiar prototype examples: those having regular shaped graphs, such as x2 or sin*, those often encountered (possibly erroneously), such as a circle, those in which y is defined as an explicit formula in x, and so on. Investigations reveal significant misconceptions. For example, threequarters of a sample of students starting a university mathematics course considered that a constant function was not a function in either its graphical or algebraic forms, and threequarters thought that a circle is a function. This reveals a wide gulf between the concepts as perceived to be taught and as actually learned by the students
Peculiarities of the function of cardiomyocytes in patients with ischemic heart disease associated with diabetes mellitus type 2
The functional activity of myocardium in patients with type 2 diabetes mellitus(T2DM) and coronary heart disease (CAD) was studied. The study included patients with CAD with T2DM as representatives of the main group, the comparison group consisted of patients with univariant course of ischemic heart disease without violation of carbohydrate metabolism. Contractile activity of the myocardium was evaluated by the inotroic reaction of isolated trabeculae of patients according to the Protocol tests "Post-rest" and "Ekstrasistoliei test". As a result, it was found that rhythm-inotropic myocardial response in patients with comorbid pathology persists to a greater extent than in the one-dimensional flow of CAD
Research of factors affecting the development of municipalities in Russia: creating a database for econometric modeling
This paper describes the preparatory stage of forming a database for the study of factors affecting the development of municipalities in Russia. The sources of information were identified and the combination of information from various databases was used in order to significantly expand the system of indicators for subsequent research. The created system of indicators is comparable with the systems of indicators used in foreign studies and will allow to identify similarities and differences in the behavior of municipalities of Russia and foreign countries. The generated database is panel data, which is enough for applying modern econometric methods for analyzing panel data, in particular, using regression models with fixed or random effects
Testing the Higgs Mechanism in the Lepton Sector with multi-TeV e+e- Collisions
Multi-TeV e+e- collisions provide with a large enough sample of Higgs bosons
to enable measurements of its suppressed decays. Results of a detailed study of
the determination of the muon Yukawa coupling at 3 TeV, based on full detector
simulation and event reconstruction, are presented. The muon Yukawa coupling
can be determined with a relative accuracy of 0.04 to 0.08 for Higgs bosons
masses from 120 GeV to 150 GeV, with an integrated luminosity of 5 inverse-ab.
The result is not affected by overlapping two-photon background.Comment: 6 pages, 2 figures, submitted to J Phys G.: Nucl. Phy
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