547 research outputs found
Proposing "b-Parity" - a New Approximate Quantum Number in Inclusive b-jet Production - as an Efficient Probe of New Flavor Physics
We consider the inclusive reaction \ell^+ \ell^- -> nb +X (n = number of
b-jets) in lepton colliders for which we propose a useful approximately
conserved quantum number b_P=(-1)^n that we call b-Parity (b_P). We make the
observation that the Standard Model (SM) is essentially b_P-even since SM
b_P-violating signals are necessarily CKM suppressed. In contrast new flavor
physics can produce b_P=-1 signals whose only significant SM background is due
to b-jet misidentification. Thus, we show that b-jet counting, which relies
primarily on b-tagging, becomes a very simple and sensitive probe of new flavor
physics (i.e., of b_P-violation).Comment: 5 pages using revtex, 2 figures embadded in the text using epsfig. As
will appear in Phys.Rev.Lett.. Considerable improvement was made in the
background calculation as compared to version 1, by including purity
parameters, QCD effects and 4-jets processe
Efficiency at optimal work from finite reservoirs: a probabilistic perspective
We revisit the classic thermodynamic problem of maximum work extraction from
two arbitrary sized hot and cold reservoirs, modelled as perfect gases.
Assuming ignorance about the extent to which the process has advanced, which
implies an ignorance about the final temperatures, we quantify the prior
information about the process and assign a prior distribution to the unknown
temperature(s). This requires that we also take into account the temperature
values which are regarded to be unphysical in the standard theory, as they lead
to a contradiction with the physical laws. Instead in our formulation, such
values appear to be consistent with the given prior information and hence are
included in the inference. We derive estimates of the efficiency at optimal
work from the expected values of the final temperatures, and show that these
values match with the exact expressions in the limit when any one of the
reservoirs is very large compared to the other. For other relative sizes of the
reservoirs, we suggest a weighting procedure over the estimates from two valid
inference procedures, that generalizes the procedure suggested earlier in [J.
Phys. A: Math. Theor. {\bf 46}, 365002 (2013)]. Thus a mean estimate for
efficiency is obtained which agrees with the optimal performance to a high
accuracy.Comment: 14 pages, 6 figure
Tracking the Tracker from its Passive Sonar ML-PDA Estimates
Target motion analysis with wideband passive sonar has received much
attention. Maximum likelihood probabilistic data-association (ML-PDA)
represents an asymptotically efficient estimator for deterministic target
motion, and is especially well-suited for low-observable targets; the results
presented here apply to situations with higher signal to noise ratio as well,
including of course the situation of a deterministic target observed via clean
measurements without false alarms or missed detections. Here we study the
inverse problem, namely, how to identify the observing platform (following a
two-leg motion model) from the results of the target estimation process, i.e.
the estimated target state and the Fisher information matrix, quantities we
assume an eavesdropper might intercept. We tackle the problem and we present
observability properties, with supporting simulation results.Comment: To appear in IEEE Transactions on Aerospace and Electronic System
New scalar resonances from sneutrino-Higgs mixing in supersymmetry with small lepton number (R-parity) violation
We consider new s-channel scalar exchanges in top quark and massive
gauge-bosons pair production in e+e- collisions, in supersymmetry with a small
lepton number violation. We show that a soft bilinear lepton number violating
term in the scalar potential which mixes the Higgs and the slepton fields can
give rise to a significant scalar resonance enhancement in e+e- -> ZZ, W+W- and
in e+e- -> t t(bar). The sneutrino-Higgs mixed state couples to the incoming
light leptons through its sneutrino component and to either the top quark or
the massive gauge bosons through its Higgs component. Such a scalar resonance
in these specific production channels cannot result from trilinear Yukawa-like
R-parity violation alone, and may, therefore, stand as strong evidence for the
existence of R-parity violating bilinears in the supersymmetric scalar
potential. We use the LEP2 measurements of the WW and ZZ cross-sections to
place useful constrains on this scenario, and investigate the expectations for
the sensitivity of a future linear collider to these signals. We find that
signals of these scalar resonances, in particular in top-pair production, are
well within the reach of linear colliders in the small lepton number violation
scenario.Comment: 22 pages in revtex, 10 figures embadded in the text using epsfi
Extraction of Airways with Probabilistic State-space Models and Bayesian Smoothing
Segmenting tree structures is common in several image processing
applications. In medical image analysis, reliable segmentations of airways,
vessels, neurons and other tree structures can enable important clinical
applications. We present a framework for tracking tree structures comprising of
elongated branches using probabilistic state-space models and Bayesian
smoothing. Unlike most existing methods that proceed with sequential tracking
of branches, we present an exploratory method, that is less sensitive to local
anomalies in the data due to acquisition noise and/or interfering structures.
The evolution of individual branches is modelled using a process model and the
observed data is incorporated into the update step of the Bayesian smoother
using a measurement model that is based on a multi-scale blob detector.
Bayesian smoothing is performed using the RTS (Rauch-Tung-Striebel) smoother,
which provides Gaussian density estimates of branch states at each tracking
step. We select likely branch seed points automatically based on the response
of the blob detection and track from all such seed points using the RTS
smoother. We use covariance of the marginal posterior density estimated for
each branch to discriminate false positive and true positive branches. The
method is evaluated on 3D chest CT scans to track airways. We show that the
presented method results in additional branches compared to a baseline method
based on region growing on probability images.Comment: 10 pages. Pre-print of the paper accepted at Workshop on Graphs in
Biomedical Image Analysis. MICCAI 2017. Quebec Cit
Production and decay of the neutral top-pion in high energy colliders
We study the production and decay of the neutral top-pion
predicted by topcolor-assisted technicolor(TC2) theory. Our results show that,
except the dominant decay modes , and , the
can also decay into and modes. It can
be significantly produced at high energy collider(LC) experiments
via the processes and . We further calculate the production cross sections of the
processes and . We find that the signatures of the neutral top-pion
can be detected via these processes.Comment: Latex file, 13 Pages, 6 eps figures. to be published in Phys.Rev.
The flavor changing top decay t-->c+sneutrino or sneutrino-->t+c(bar) in the MSSM without R-parity
Widths for the new flavor changing top quark decay t-->c+sneutrino or for the
reversed sneutrino decay sneutrino-->t+c(bar) are calculated in the MSSM
without R-parity conservation. For large \tan\beta, e.g., \tan\beta ~ m_t/m_b ~
40, Br(t-->c+sneutrino) > 10^{-5} or Br(sneutrino-->t+c(bar)) > 10^{-6} in a
relatively wide range of the supersymmetric parameter space as long as there is
more than one non-zero R-parity violating coupling. In the best cases, with a
typical squark mass around 100 GeV, we find that Br(t-->c+sneutrino) ~ 10^{-4}
- 10^{-3} or Br(sneutrino-->t+c(bar)) ~ 10^{-5} - 10^{-4}. For \tan\beta ~ O(1)
the corresponding branching ratios for both top or sneutrino decays are too
small to be measured at the LHC. Therefore, the decays t-->c+sneutrino or
sneutrino-->t+c(bar) appear to be sensitive to \tan\beta and may be detected at
the LHC. The branching ratios of the corresponding decays to an up quark
instead of a charm quark, e.g., t-->u+sneutrino or sneutrino-->t+u(bar), may
also be similar.Comment: 23 pages, plain latex, 8 figures embadded in the text using epsfi
CP Nonconservation in at the Tevatron
The reaction is found to be rather rich in exhibiting
several different types of CP asymmetries. The spin of the top quark plays an
important role. Asymmetries are related to form factors arising from radiative
corrections of the production vertex due to non-standard physics. As
illustrations, effects are studied in two Higgs Doublet Models and in
Supersymmetric Models; asymmetries up to a few percent may be possible.Comment: 14 pages, 3 figures. Note: replaced due to minor problems that
appeared on some postscript previewers. No change in conten
Determining the top-antitop and Couplings of a Neutral Higgs Boson of Arbitrary CP Nature at the NLC
The optimal procedure for extracting the coefficients of different components
of a cross section which takes the form of unknown coefficients times functions
of known kinematical form is developed. When applied to \epem\to t\anti
t+Higgs production at \rts=1\tev and integrated luminosity of 200\fbi, we
find that the t\anti t\toHiggs CP-even and CP-odd couplings and, to a lesser
extent, the Higgs (CP-even) coupling can be extracted with reasonable
errors, assuming the Higgs sector parameter choices yield a significant
production rate. Indeed, the composition of a mixed-CP Higgs eigenstate can be
determined with sufficient accuracy that a SM-like CP-even Higgs boson can be
distinguished from a purely CP-odd Higgs boson at a high level of statistical
significance, and vice versa.Comment: 8 pages, full postscript file also available via anonymous ftp at
ftp://ucdhep.ucdavis.edu/gunion/eetottbh.p
- …