4,215 research outputs found
Approximate Minimum Diameter
We study the minimum diameter problem for a set of inexact points. By
inexact, we mean that the precise location of the points is not known. Instead,
the location of each point is restricted to a contineus region (\impre model)
or a finite set of points (\indec model). Given a set of inexact points in
one of \impre or \indec models, we wish to provide a lower-bound on the
diameter of the real points.
In the first part of the paper, we focus on \indec model. We present an
time
approximation algorithm of factor for finding minimum diameter
of a set of points in dimensions. This improves the previously proposed
algorithms for this problem substantially.
Next, we consider the problem in \impre model. In -dimensional space, we
propose a polynomial time -approximation algorithm. In addition, for
, we define the notion of -separability and use our algorithm for
\indec model to obtain -approximation algorithm for a set of
-separable regions in time
Using B_s^0 Decays to Determine the CP Angles \alpha and \gamma
Dighe, Gronau and Rosner have shown that, by assuming SU(3) flavor symmetry
and first-order SU(3) breaking, it is possible to extract the CP angles \alpha
and \gamma from measurements of the decay rates of B_d^0(t) --> \pi^+\pi^-,
B_d^0 --> \pi^- K^+ and B^+ --> \pi^+ K^0, along with their charge-conjugate
processes. We extend their analysis to include the SU(3)-related decays B_s^0
--> \pi^+ K^-, B_s^0(t) --> K^+ K^- and B_s^0 --> K^0 {\bar K^0}. There are
several advantages to this extension: discrete ambiguities are removed, fewer
assumptions are necessary, and the method works even if all strong phases
vanish. In addition, we show that \gamma can be obtained cleanly, with no
penguin contamination, by using the two decays B_s^0(t) --> K^+ K^- and B_s^0
--> K^0 {\bar K^0}.Comment: 28 pages, LaTe
Detection of the Mass of Airborne Particles in an online Optical Sensor System by Correlation of Geometric and Inertial Filtering
AbstractWe present a method combining inertial and geometric filtering to approximate the mass of particles for optical particle detection systems. The method consists of three measurement steps and is based on the difference of the filtering behavior of geometric and inertial filters based on particle size and particle density respectively. Our measurements show the feasibility using polystyrene latex particles with sizes 300/500/900nm and silica particles with diameters 500nm and 1000nm
In Pursuit of New Physics with B_s Decays
The presence of a sizeable CP-violating phase in B_s^0-B_s^0-bar mixing would
be an unambiguous signal of physics beyond the Standard Model. We analyse
various possibilities to detect such a new phase considering both tagged and
untagged decays. The effects of a sizeable width difference Delta Gamma between
the B_s mass eigenstates, on which the untagged analyses rely, are included in
all formulae. A novel method to find this phase from simple measurements of
lifetimes and branching ratios in untagged decays is proposed. This method does
not involve two-exponential fits, which require much larger statistics. For the
tagged decays, an outstanding role is played by the observables of the
time-dependent angular distribution of the B_s -> J/psi [-> l^+ l^-] \phi [->
K^+K^-] decay products. We list the formulae needed for the angular analysis in
the presence of both a new CP-violating phase and a sizeable Delta Gamma, and
propose methods to remove a remaining discrete ambiguity in the new phase. This
phase can therefore be determined in an unambiguous way.Comment: minor changes, lattice prediction of Delta Gamma updated, appears in
PR
Towards new frontiers in the exploration of charmless non-leptonic B decays
Non-leptonic decays into charmless final states offer an important
laboratory to study CP violation and the dynamics of strong interactions.
Particularly interesting are and decays,
which are related by the -spin symmetry of strong interactions, and allow
for the extraction of CP-violating phases and tests of the Standard Model. The
theoretical precision is limited by -spin-breaking corrections and
innovative methods are needed in view of the impressive future experimental
precision expected in the era of Belle II and the LHCb upgrade. We have
recently proposed a novel method to determine the - mixing
phase from the , system, where
semileptonic ,
decays are a new ingredient and the theoretical situation is very favourable.
We discuss this strategy in detail, with a focus on penguin contributions as
well as exchange and penguin-annihilation topologies which can be probed by a
variety of non-leptonic decays into charmless final states. We show that a
theoretical precision as high as for can be
attained in the future, thereby offering unprecedented prospects for the search
for new sources of CP violation.Comment: 50 pages, 25 figure
Effects of R-parity violation on direct CP violation in B decays and extraction of
In the standard model, direct CP-violating asymmetries for are roughly 2% based on perturbative calculation. Rescattering effects might
enhance it to at most (20-25)%. We show that lepton-number-violating couplings
in supersymmetric models without R-parity are capable of inducing as large as
100% CP asymmetry in this channel. Such effects drastically modify the allowed
range of the CKM parameter arising from the combinations of the
observed charged and neutral B decays in the modes. With a multichannel
analysis in B decays, one can either discover this exciting new physics, or
significantly improve the existing constraints on it.Comment: Latex, 5 pages; minor changes, to appear in Phys Rev Let
Long-range two-body final-state interactions and direct CP asymmetry in {B}^{+}\to{\pi}^{+} {K}^{0} decay
We present a calculation of the direct CP asymmetry, , for the
process including the effects of long-range inelastic
final-state interactions (FSI). We admit three channels in our calculation:
, and . The strong
scattering is described in terms of Pomeron and Regge exchanges. We find that
the direct CP asymmetry is enhanced by a factor of as a result of FSI,
but remains well short of the claims of (10 - 20)% in recent literature. A
critical assessment of papers claiming large CP asymmetries is also presented.Comment: 21 pages, latex, no figures. Added the charge-exchange channel
{B}^{+}\to {\pi}^{0} {K}^{+}. Expanded the discussion section. To be
published in Phys. Rev.
Exploring CP Violation with Decays
We point out that the pure ``tree'' decays are
particularly well suited to extract the CKM angle through amplitude
relations. In contrast to conceptually similar strategies using or decays, the advantage of the approach is that
the corresponding triangles have three sides of comparable length and do not
involve small amplitudes. Decays of the type -- the
-spin counterparts of -- can be added to the
analysis, as well as channels, where the - and -mesons are
replaced by higher resonances.Comment: 9 pages, LaTeX, 3 figures, reference adde
Taming the Penguin in the B0(t) -> Pi+Pi- CP-asymmetry: Observables and Minimal Theoretical Input
Penguin contributions, being not negligible in general, can hide the
information on the CKM angle alpha coming from the measurement of the
time-dependent B0(t) -> pi+pi- CP-asymmetry. Nevertheless, we show that this
information can be summarized in a set of simple equations, expressing alpha as
a multi-valued function of a single theoretically unknown parameter, which
conveniently can be chosen as a well-defined ratio of penguin to tree
amplitudes. Using these exact analytic expressions, free of any assumption
besides the Standard Model, and some reasonable hypotheses to constrain the
modulus of the penguin amplitude, we derive several new upper bounds on the
penguin-induced shift |2alpha-2alpha_eff|, generalizing the recent result of
Grossman and Quinn. These bounds depend on the averaged branching ratios of
some decays (pi0pi0, K0K0bar, K+-pi-+) particularly sensitive to the penguin.
On the other hand, with further and less conservative approximations, we show
that the knowledge of the B+- -> Kpi+- branching ratio alone gives sufficient
information to extract the free parameter without the need of other
measurements, and without knowing |V_td| or |V_ub|. More generally, knowing the
modulus of the penguin amplitude with an accuracy of ~30% might result in an
extraction of alpha competitive with the experimentally more difficult isospin
analysis. We also show that our framework allows to recover most of the
previous approaches in a transparent and simple way, and in some cases to
improve them. In addition we discuss in detail the problem of the various kinds
of discrete ambiguities.Comment: LaTeX2e, 44 pages, 9 figures (from 18 postscript files) included with
epsf. Minor changes, references updated. New CLEO results from ICHEP'98 are
taken into account. To appear in Phys. Rev.
Charming penguins in B => K* pi, K (rho,omega,phi) decays
We evaluate the decays B => K* pi, K (rho,omega,phi) adding the long distance
charming penguin contributions to the short distance: Tree+Penguin amplitudes.
We estimate the imaginary part of the charming penguin by an effective field
theory inspired by the Heavy Quark Effective Theory and parameterize its real
part. The final results for branching ratios depend on only two real parameters
and show a significant role of the charming penguins. The overall agreement
with the available experimental data is satisfactory.Comment: 13 pages, 1 figur
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