18 research outputs found
An Optimal Self-Stabilizing Firing Squad
Consider a fully connected network where up to processes may crash, and
all processes start in an arbitrary memory state. The self-stabilizing firing
squad problem consists of eventually guaranteeing simultaneous response to an
external input. This is modeled by requiring that the non-crashed processes
"fire" simultaneously if some correct process received an external "GO" input,
and that they only fire as a response to some process receiving such an input.
This paper presents FireAlg, the first self-stabilizing firing squad algorithm.
The FireAlg algorithm is optimal in two respects: (a) Once the algorithm is
in a safe state, it fires in response to a GO input as fast as any other
algorithm does, and (b) Starting from an arbitrary state, it converges to a
safe state as fast as any other algorithm does.Comment: Shorter version to appear in SSS0
b-physics signals of the lightest CP-odd Higgs in the NMSSM at large tan beta
We investigate the low energy phenomenology of the lighter pseudoscalar
in the NMSSM. The mass can naturally be small due to a global
symmetry of the Higgs potential, which is only broken by trilinear
soft terms. The mass is further protected from renormalization group
effects in the large limit. We calculate the
amplitude at leading order in and work out the contributions to
rare , and radiative -decays and mixing. We obtain
constraints on the mass and couplings and show that masses down to
MeV are allowed. The -physics phenomenology of the NMSSM
differs from the MSSM in the appearance of sizeable renormalization effects
from neutral Higgses to the photon and gluon dipole operators and the breakdown
of the MSSM correlation between the branching ratio and
mixing. For masses above the tau threshold the
can be searched for in processes with branching ratios
\lsim 10^{-3}.Comment: 18 pages, 3 figures; references adde
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Precison Measurements of the Mass, the Widths of Resonance and the Cross Section at GeV
By analyzing the values measured at 68 energy points in the energy region
between 3.650 and 3.872 GeV reported in our previous paper, we have precisely
measured the mass, the total width, the leptonic width and the leptonic decay
branching fraction of the to be MeV, MeV,
eV and , respectively, which result in
the observed cross section nb at MeV. We have also measured for the continuum light hadron production in the
region from 3.650 to 3.872 GeV.Comment: 5 pages, 2 figure
Measurements of the cross sections for at 3.650, 3.6648, 3.773 GeV and the branching fraction for
Using the BES-II detector at the BEPC Collider, we measured the lowest order
cross sections and the values () for inclusive hadronic event
production at the center-of-mass energies of 3.650 GeV, 3.6648 GeV and 3.773
GeV. The results lead to which is the
average of these measured at 3.650 GeV and 3.6648 GeV, and at GeV. We determined the lowest order cross
section for production to be at 3.773 GeV, the branching fractions for
decays to be , and , which result in the total non-
branching fraction of decay to be .Comment: 11 pages, 5 figure
Supernova neutrino detection in NOvA
The NOvA long-baseline neutrino experiment uses a pair of large, segmented, liquid-scintillator calorimeters to study neutrino oscillations, using GeV-scale neutrinos from the Fermilab NuMI beam. These detectors are also sensitive to the flux of neutrinos which are emitted during a core-collapse supernova through inverse beta decay interactions on carbon at energies of O(10 MeV). This signature provides a means to study the dominant mode of energy release for a core-collapse supernova occurring in our galaxy. We describe the data-driven software trigger system developed and employed by the NOvA experiment to identify and record neutrino data from nearby galactic supernovae. This technique has been used by NOvA to self-trigger on potential core-collapse supernovae in our galaxy, with an estimated sensitivity reaching out to 10 kpc distance while achieving a detection efficiency of 23% to 49% for supernovae from progenitor stars with masses of 9.6 M☉ to 27 M☉, respectively
Broadcast Amplification
Abstract. A d-broadcast primitive is a communication primitive that allows a sender to send a value from a domain of size d to a set of parties. A broadcast protocol emulates the d-broadcast primitive using only point-to-point channels, even if some of the parties cheat, in the sense that all correct recipients agree on the same value v (consistency), and if the sender is correct, then v is the value sent by the sender (validity). A celebrated result by Pease, Shostak and Lamport states that such a broadcast protocol exists if and only if t < n/3, where n denotes the total number of parties and t denotes the upper bound on the number of cheaters. This paper is concerned with broadcast protocols for any number of cheaters (t < n), which can be possible only if, in addition to point-topoint channels, another primitive is available. Broadcast amplification is the problem of achieving d-broadcast when d ′-broadcast can be used once, for d ′ < d. Let φn(d) denote the minimal such d ′ for domain size d. We show that for n = 3 parties, broadcast for any domain size is possible if only a single 3-broadcast is available, and broadcast of a single bit (d ′ = 2) is not sufficient, i.e., φ3(d) = 3 for any d ≥ 3. In contrast, for n> 3 no broadcast amplification is possible, i.e., φn(d) = d for any d. However, if other parties than the sender can also broadcast some short messages, then broadcast amplification is possible for any n. Let φ ∗ n(d) denote the minimal d ′ such that d-broadcast can be constructed from primitives d ′ 1-broadcast,..., d ′ k-broadcast, where d ′ = ∏ i d ′ i (i.e., log d ′ ∑ i log d ′ i). Note that φ ∗ n(d) ≤ φn(d). We show that broadcasting 8n log n bits in total suffices, independently of d, and that at least n−2 parties, including the sender, must broadcast at least one bit. Hence min(log d, n − 2) ≤ log φ ∗ n(d) ≤ 8n log n
Upper Bounds on the Communication Complexity of Optimally Resilient Cryptographic Multiparty Computation
Abstract. We give improved upper bounds on the communication complexity of optimally-resilient secure multiparty computation in the cryptographic model. We consider evaluating an n-party randomized function and show that if f can be computed by a circuit of size c, thenO(cn 2 κ) is an upper bound for active security with optimal resilience t<n/2and security parameter κ. This improves on the communication complexity of previous protocols by a factor of at least n. This improvement comes from the fact that in the new protocol, only O(n) messages (of size O(κ) each) are broadcast during the whole protocol execution, in contrast to previous protocols which require at least O(n) broadcasts per gate. Furthermore, we improve the upper bound on the communication complexity of passive secure multiparty computation with resilience t<n from O(cn 2 κ)toO(cnκ). This improvement is mainly due to a simple observation.