6,205 research outputs found
CP Violation in Mixing
The existence of mixing at a detectable level requires
new physics, which effectively yields a superweak interaction.
In general this interaction may involve significant CP violation. For small
values of the mixing it may be much easier to detect the CP-violating part of
the mixing than the CP-conserving part.Comment: 3 pages, latex, no figure
Turbulent convection: comparing the moment equations to numerical simulations
The non-local hydrodynamic moment equations for compressible convection are
compared to numerical simulations. Convective and radiative flux typically
deviate less than 20% from the 3D simulations, while mean thermodynamic
quantities are accurate to at least 2% for the cases we have investigated. The
moment equations are solved in minutes rather than days on standard
workstations. We conclude that this convection model has the potential to
considerably improve the modelling of convection zones in stellar envelopes and
cores, in particular of A and F stars.Comment: 10 pages (6 pages of text including figure captions + 4 figures),
Latex 2e with AAS Latex 5.0 macros, accepted for publication in ApJ
CP Violation in \tau ->\nu\pi K_S and D->\pi K_S: The Importance of K_S-K_L Interference
The -factories have measured CP asymmetries in the and
modes. The state is identified by its decay to two pions at
a time that is close to the lifetime. Within the Standard Model and many
of its extensions, the asymmetries in these modes come from CP violation in
mixing. We emphasize that the interference between the
amplitudes of intermediate and is as important as the pure
amplitude. Consequently, the measured asymmetries depend on the times over
which the relevant decay rates are integrated and on features of the
experiment.Comment: 4 pages, 4 figure
Towards granular hydrodynamics in two-dimensions
We study steady-state properties of inelastic gases in two-dimensions in the
presence of an energy source. We generalize previous hydrodynamic treatments to
situations where high and low density regions coexist. The theoretical
predictions compare well with numerical simulations in the nearly elastic
limit. It is also seen that the system can achieve a nonequilibrium
steady-state with asymmetric velocity distributions, and we discuss the
conditions under which such situations occur.Comment: 8 pages, 9 figures, revtex, references added, also available from
http://arnold.uchicago.edu/?ebn
Locally Localized Gravity Models in Higher Dimensions
We explore the possibility of generalizing the locally localized gravity
model in five space-time dimensions to arbitrary higher dimensions. In a
space-time with negative cosmological constant, there are essentially two kinds
of higher-dimensional cousins which not only take an analytic form but also are
free from the naked curvature singularity in a whole bulk space-time. One
cousin is a trivial extension of five-dimensional model, while the other one is
in essence in higher dimensions. One interesting observation is that in the
latter model, only anti-de Sitter () brane is physically meaningful
whereas de Sitter () and Minkowski () branes are dismissed.
Moreover, for brane in the latter model, we study the property of
localization of various bulk fields on a single brane. In particular, it is
shown that the presence of the brane cosmological constant enables bulk gauge
field and massless fermions to confine to the brane only by a gravitational
interaction. We find a novel relation between mass of brane gauge field and the
brane cosmological constant.Comment: 20 pages, LaTex 2e, revised version (to appear in Phys. Rev. D
A consistent picture for large penguins in D -> pi+ pi-, K+ K-
A long-standing puzzle in charm physics is the large difference between the
D0 -> K+ K- and D0 -> pi+ pi- decay rates. Recently, the LHCb and CDF
collaborations reported a surprisingly large difference between the direct CP
asymmetries, Delta A_CP, in these two modes. We show that the two puzzles are
naturally related in the Standard Model via s- and d-quark "penguin
contractions". Their sum gives rise to Delta A_CP, while their difference
contributes to the two branching ratios with opposite sign. Assuming nominal
SU(3) breaking, a U-spin fit to the D0 -> K+ pi-, pi+ K-, pi+ pi-, K+ K- decay
rates yields large penguin contractions that naturally explain Delta A_CP.
Expectations for the individual CP asymmetries are also discussed.Comment: 24 pages, 8 figure
From Stars to Super-planets: the Low-Mass IMF in the Young Cluster IC348
We investigate the low-mass population of the young cluster IC348 down to the
deuterium-burning limit, a fiducial boundary between brown dwarf and planetary
mass objects, using a new and innovative method for the spectral classification
of late-type objects. Using photometric indices, constructed from HST/NICMOS
narrow-band imaging, that measure the strength of the 1.9 micron water band, we
determine the spectral type and reddening for every M-type star in the field,
thereby separating cluster members from the interloper population. Due to the
efficiency of our spectral classification technique, our study is complete from
approx 0.7 Msun to 0.015 Msun. The mass function derived for the cluster in
this interval, dN/dlogM \propto M^{0.5}, is similar to that obtained for the
Pleiades, but appears significantly more abundant in brown dwarfs than the mass
function for companions to nearby sun-like stars. This provides compelling
observational evidence for different formation and evolutionary histories for
substellar objects formed in isolation vs. as companions. Because our
determination of the IMF is complete to very low masses, we can place
interesting constraints on the role of physical processes such as fragmentation
in the star and planet formation process and the fraction of dark matter in the
Galactic halo that resides in substellar objects.Comment: 37 pages, 16 figs, 6 tables (Table 4 is a separate LaTeX file)
Accepted for publication in Astrophysical Journal (Oct 1, 2000 issue
Detection of synchronization from univariate data using wavelet transform
A method is proposed for detecting from univariate data the presence of
synchronization of a self-sustained oscillator by external driving with varying
frequency. The method is based on the analysis of difference between the
oscillator instantaneous phases calculated using continuous wavelet transform
at time moments shifted by a certain constant value relative to each other. We
apply our method to a driven asymmetric van der Pol oscillator, experimental
data from a driven electronic oscillator with delayed feedback and human
heartbeat time series. In the latest case, the analysis of the heart rate
variability data reveals synchronous regimes between the respiration and slow
oscillations in blood pressure.Comment: 10 pages, 9 figure
decays in SUSY models without R-parity
Being strictly forbidden in the standard model, experimental detection of the
lepton flavor violating decays and would constitute an unmistakable indication of new physics. We
study these decays in supersymmetric models without R-parity and without lepton
number. In order to derive order of magnitude predictions for the branching
ratios, we assume a horizontal U(1) symmetry with horizontal charges chosen to
explain the magnitude of fermion masses and quark mixing angles. We find that
the branching ratios for decays with a pair in the final state are
not particularly suppressed with respect to the lepton flavor conserving
channels. In general in these models {\rm B}[b\to\mu^+\mu^-(X)]\lsim {\rm
B}[b(\bar b)\to\tau^+\mu^-(X)] \lsim {\rm B}[b\to\tau^+\tau^-(X)]. While in
some cases the rates for final states can be up to one order of
magnitude larger than the lepton flavor violating channel, due to better
efficiencies for muon detection and to the absence of standard model
contributions, decays into final states appear to be better suited to
reveal this kind of new physics.Comment: 15 pages, LaTeX, 3 ps-figures (uses epsfig.sty) Minor typos
corrected, one normalization factor added to Eq. (3.11). To be published on
Phys. Rev.
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