15,901 research outputs found
Hadron Physics at KLOE and KLOE-2
The KLOE Collaboration completed the full data taking on March 2006,
acquiring 2.5 fb ^ -1 at the peak of the \phi and other 240 pb ^ -1 off-peak. A
new Collaboration is working on a new project, called KLOE-2, to refine and
extend the KLOE physics program. We present here some preliminary and published
results from the KLOE Collaboration on the pseudoscalar \eta meson and the
study of \gamma \gamma processes, that are among the main points of the KLOE-2
physics program.Comment: Presented at Hadron 201
eta - eta prime Mixing -From electromagnetic transitions to weak decays of charm and beauty hadrons
It has been realized for a long time that knowing the eta and eta^prime wave
functions in terms of quark and gluon components probes our understanding of
non-perturbative QCD dynamics. Great effort has been given to this challenge --
yet no clear picture has emerged even with the most recent KLOE data. We point
out which measurements would be most helpful in arriving at a more definite
conclusion. A better knowledge of these wave functions will significantly help
to disentangle the weight of different decay subprocesses in semi-leptonic
decays of D+, Ds^+ and B+ mesons. The resulting insights will be instrumental
in treating even non-leptonic B transitions involving eta and eta^prime and
their CP asymmetries; thus they can sharpen the case for or against New Physics
intervening there.Comment: 22 pages, 4 figures; it matches published versio
Prescriptions on antiproton cross section data for precise theoretical antiproton flux predictions
After the breakthrough from the satellite-borne PAMELA detector, the flux of
cosmic-ray (CR) antiprotons has been provided with unprecedented accuracy by
AMS-02 on the International Space Station. Its data spans an energy range from
below 1 GeV up to 400 GeV and most of the data points contain errors below the
amazing level of 5%. The bulk of the antiproton flux is expected to be produced
by the scatterings of CR protons and helium off interstellar hydrogen and
helium atoms at rest. The modeling of these interactions, which requires the
relevant production cross sections, induces an uncertainty in the determination
of the antiproton source term that can even exceed the uncertainties in the CR
data itself. The aim of the present analysis is to determine the
uncertainty required for cross section
measurements such that the induced uncertainties on the flux are at
the same level. Our results are discussed both in the center-of-mass reference
frame, suitable for collider experiments, and in the laboratory frame, as
occurring in the Galaxy. We find that cross section data should be collected
with accuracy better that few percent with proton beams from 10 GeV to 6 TeV
and a pseudorapidity ranging from 2 to almost 8 or, alternatively, with
from 0.04 to 2 GeV and from 0.02 to 0.7. Similar considerations
hold for the He production channel. The present collection of data is far
from these requirements. Nevertheless, they could, in principle, be reached by
fixed target experiments with beam energies in the reach of CERN accelerators.Comment: 15 pages, 13 figures, matches published versio
Multi-messenger constraints to the local emission of cosmic-ray electrons
The data on the inclusive flux of cosmic positrons and electrons
() have been recently collected from GeV to tens of TeV energies by
several experiments with unprecedented precision. In addition, the Fermi-LAT
Collaboration has provided a new energy spectrum for the upper bounds on the
dipole anisotropy. This observable can bring information on the
emission from local Galactic sources, notably measured with high precision at
radio frequencies. We develop a framework in which and measured at
Earth from GeV up to tens of TeV energies have a composite origin. A dedicated
analysis is deserved to Vela YZ and Cygnus Loop Supernova Remnants (SNRs), for
which we consider two different models for the injection of . We
investigate the consistency of these models using the three physical
observables: the radio flux from Vela YZ and Cygnus Loop at all the available
frequencies, the flux from five experiments from the GeV to tens of
TeV energy, the dipole anisotropy upper limits from 50 GeV to about 1
TeV. We find that the radio flux for these nearby SNRs strongly constraints the
properties of the injection electron spectrum, partially compatible with the
looser constraints derived from the flux data. We also perform a
multi-wavelength multi-messenger analysis by fitting simultaneously the radio
flux on Vela YZ and Cygnus Loop and the flux, and checking the
outputs against the dipole anisotropy data. Remarkably, we find a
model which is compatible with all the flux data, the radio data for
Vela YZ and Cygnus Loop, and with the anisotropy upper bounds. We show the
severe constraints imposed by the most recent data on the dipole
anisotropy.Comment: 20 pages, 9 figures. Accepted for publication in the JCAP. Changes in
v3: discussion and results extended to include an evolutionary model for the
injection of cosmic-ray electrons in SNR
On distributed virtual network embedding with guarantees
To provide wide-area network services, resources from different infrastructure providers are needed. Leveraging the consensus-based resource allocation literature, we propose a general distributed auction mechanism for the (NP-hard) virtual network (VNET) embedding problem. Under reasonable assumptions on the bidding scheme, the proposed mechanism is proven to converge, and it is shown that the solutions guarantee a worst case efficiency of (?????) relative to the optimal solution, and that this bound is optimal, that is, no better approximation exists. Using extensive simulations, we confirm superior convergence properties and resource utilization when compared with existing distributed VNET embedding solutions, and we show how byappropriate policy design, our mechanism can be instantiated to accommodate the embedding goals of different service and infrastructure providers, resulting in an attractive and flexible resource allocation solution.This work is supported in part by the National Science Foundation under grant CNS-0963974
On distributed virtual network embedding with guarantees
To provide wide-area network services, resources from different infrastructure providers are needed. Leveraging the consensus-based resource allocation literature, we propose a general distributed auction mechanism for the (NP-hard) virtual network (VNET) embedding problem. Under reasonable assumptions on the bidding scheme, the proposed mechanism is proven to converge, and it is shown that the solutions guarantee a worst-case efficiency of (1-(1/e)) relative to the optimal node embedding, or VNET embedding if virtual links are mapped to exactly one physical link. This bound is optimal, that is, no better polynomial-time approximation algorithm exists, unless P=NP. Using extensive simulations, we confirm superior convergence properties and resource utilization when compared to existing distributed VNET embedding solutions, and we show how by appropriate policy design, our mechanism can be instantiated to accommodate the embedding goals of different service and infrastructure providers, resulting in an attractive and flexible resource allocation solution.CNS-0963974 - National Science Foundationhttp://www.cs.bu.edu/fac/matta/Papers/ToN-CAD.pdfAccepted manuscrip
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