6,268 research outputs found
Is it possible to Measure the Weak Phase of a Penguin Diagram?
The penguin amplitude receives contributions from internal ,
and -quarks. We show that it is impossible to measure the weak phase of any
of these penguin contributions without theoretical input. However, a single
assumption involving the hadronic parameters makes it possible to obtain the
weak phase and test for the presence of new physics in the
flavour-changing neutral current.Comment: 4 pages, latex, no figures, talk given by R. Sinha at the 3rd
International Conference on B Physics and CP Violation, Taipei, Taiwan,
December 3-7, 1999, to appear in the Proceeding
Probing New Physics via an Angular Analysis of B --> V1 V2 decays
We show that an angular analysis of B --> V1 V2 decays yields numerous tests
for new physics in the decay amplitudes. Unlike direct CP asymmetries, many of
these new-physics observables are nonzero even if the strong phase differences
vanish. For certain observables, neither time-dependent measurements nor
tagging is necessary. Should a signal for new physics be found, one can place a
lower limit on the size of the new-physics parameters, as well as on their
effect on the measurement of the phase of B0--Bbar0 mixing.Comment: 9 pages, plain latex, no figures. Title modified slightly. Paragraph
added about viability of method. Conclusions unchanged. To be published in
Europhysics Letter
Mission Capabilities of Ion Engines Using SNAP-8 Power Supplies
Mission performance capabilities of ion engines powered by the 30 kw and 60 kw SNAP-8 power supplies are compared for the following missions: a 24-hr equatorial satellite, a 100 n mi lunar satellite, a 500 n mi Mars satellite, a Mercury probe, and an out-of-the-ecliptic probe. The capabilities of arc- jet engines and chemical engines for the same missions are compared with those of the ion engines. The majority of the comparisons are for 8500-lb spacecraft which are boosted into a 300 n mi orbit by the Atlas-Centaur. Variations in initial orbit altitude, the use of actual launch dates rather than dates based on simplifying assumptions, and the combined use of chemical and electrical propulsion systems were also evaluated in terms of their effect on mission performance
Extreme precision in rhythmic interaction is enabled by role-optimized sensorimotor coupling: Analysis and modelling of West African drum ensemble music
Human social interactions often involve carefully synchronized behaviours. Musical performance in particular features precise timing and depends on the differentiation and coordination of musical/social roles. Here, we study the influence of musical/social roles, individual musicians and different ensembles on rhythmic synchronization in Malian drum ensemble music, which features synchronization accuracy near the limits of human performance. We analysed 72 recordings of the same piece performed by four trios, in which two drummers in each trio systematically switched roles (lead versus accompaniment). Musical role, rather than individual or group differences, is the main factor influencing synchronization accuracy. Using linear causal modelling, we found a consistent pattern of bi-directional couplings between players, in which the direction and strength of rhythmic adaptation is asymmetrically distributed across musical roles. This differs from notions of musical leadership, which assume that ensemble synchronization relies predominantly on a single dominant personality and/or musical role. We then ran simulations that varied the direction and strength of sensorimotor coupling and found that the coupling pattern used by the Malian musicians affords nearly optimal synchronization. More broadly, our study showcases the importance of ecologically valid and culturally diverse studies of human behaviour
Hall Coefficient of Equilibrium Supercurrents Flowing inside Superconductors
We study augmented quasiclassical equations of superconductivity with the
Lorentz force, which is missing from the standard Ginzburg-Landau and
Eilenberger equations. It is shown that the magnetic Lorentz force on
equilibrium supercurrents induces finite charge distribution and the resulting
electric field to balance the Lorentz force. An analytic expression is obtained
for the corresponding Hall coefficient of clean type-II superconductors with
simultaneously incorporating the Fermi-surface and gap anisotropies. It has the
same sign and magnitude at zero temperature as the normal state for an
arbitrary pairing, having no temperature dependence specifically for the s-wave
pairing. The gap anisotropy may bring a considerable temperature dependence in
the Hall coefficient and can lead to its sign change as a function of
temperature, as exemplified for a model d-wave pairing with a two-dimensional
Fermi surface. The sign change may be observed in some high-
superconductors.Comment: 7 pages, 3 figure
Production of qqQQ final states in ee collisions in the left-right symmetric model
We consider the reaction ee ->qqQQ as a test of lepton number
non-conservation in the framework of the left-right-symmetric electroweak
model. The main contributions to this process are due to Majorana neutrino
exchange in t-channel and doubly charged Higgs (Delta{--}) exchange in
s-channel with a pair of right-handed weak bosons (WR) as intermediate state.
We show that in a linear ee collider with the collision energy of 1 TeV (1.5
TeV) the cross section of this process is 0.01 fb (1 fb), and it will, for the
anticipated luminosity of 10**{35} cm**{-2}, be detectable below the WR
threshold. We study the sensitivity of the reaction on the masses of the heavy
neutrino, WR and Delta{--}.Comment: 24 pages, 9 eps figures, uses axodraw.st
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