554 research outputs found
Using a Logic Programming Framework to Control Database Query Dialogues in Natural Language
We present a natural language question/answering system to interface the University of Ăvora databases that uses clarification dialogs in order to clarify user questions. It was developed in an integrated logic programming framework, based on constraint logic programming using the GnuProlog(-cx) language [2,11] and the ISCO framework [1]. The use of this LP framework allows the integration of Prolog-like inference mechanisms with classes and inheritance, constraint solving algorithms and provides the connection with relational databases, such as PostgreSQL. This system focus on the questionsâ pragmatic analysis, to handle ambiguity, and on an efficient dialogue mechanism, which is able to place relevant questions to clarify the user intentions in a straightforward manner. Proper Nouns resolution and the pp-attachment problem are also handled.
This paper briefly presents this innovative system focusing on its ability to correctly determine the user intention through its dialogue capability
Supersymmetry and the positron excess in cosmic rays
Recently the HEAT balloon experiment has confirmed an excess of high-energy
positrons in cosmic rays. They could come from annihilation of dark matter in
the galactic halo. We discuss expectations for the positron signal in cosmic
rays from the lightest superpartner. The simplest interpretations are
incompatible with the size and shape of the excess if the relic LSPs evolved
from thermal equilbrium. Non-thermal histories can describe a sufficient
positron rate. Reproducing the energy spectrum is more challenging, but perhaps
possible. The resulting light superpartner spectrum is compatible with collider
physics, the muon anomalous magnetic moment, Z-pole electroweak data, and other
dark matter searches.Comment: 4 pages, 2 figures, references added, minor wording change
On the Observability of "Invisible" / "Nearly Invisible" Charginos
It is shown that if the charginos decay into very soft leptons or hadrons +
due to degeneracy/ near- degeneracy with the LSP or the sneutrino,
the observability of the recently proposed signal via the single photon (+ soft
particles) + channel crucially depends on the magnitude of the \SNU
mass due to destructive interferences in the matrix element squared. If the
\SNU's and, consequently, left-sleptons are relatively light, the size of the
signal, previously computed in the limit \MSNU \to \infty only, is
drastically reduced. We present the formula for the signal cross section in a
model independent way and discuss the observability of the signal at LEP 192
and NLC energies.Comment: 27 pages, Late
The reaction in ion-ion collisions
We study the threshold -meson production in the process , which appears as a possible important mechanism in high energy
nuclei-nuclei collisions. The isotopic invariance of the strong interaction and
the selection rules due to P-parity and total angular momentum result in a
general and model independent parametrization of the spin structure of the
matrix element in terms of three partial amplitudes. In the framework of
one-pion exchange model these amplitudes can be derived in terms of the two
threshold partial amplitudes for the process . We predict the
ratio of cross sections for meson production in - and -collisions and the polarization properties of the -meson, in
, as a function of a single parameter, which
characterizes the relative role of transversal and longitudinal -meson
polarizations in the process .Comment: 10 pages 3 figure
Pair production of neutralinos via gluon-gluon collisions
The production of a neutralino pair via gluon-gluon fusion is studied in the
minimal supersymmetric model(MSSM) at proton-proton colliders. The numerical
analysis of their production rates are carried out in the mSUGRA scenario. The
results show that this cross section may reach about 80 femto barn for
pair production and 23 femto barn
for pair production with suitable
input parameters at the future LHC collider. It shows that this loop mediated
process can be competitive with the quark-antiquark annihilation process at the
LHC.Comment: LaTex file, l4 pages, 5 EPS figure
Measurement of the ttÂŻ production cross-section using eÎŒ events with b-tagged jets in pp collisions at âs=13TeV with the ATLAS detector
This paper describes a measurement of the inclusive top quark pair production cross-section (ÏttÂŻ) with a data sample of 3.2fbâ1 of protonâproton collisions at a centre-of-mass energy of s=13TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electronâmuon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously ÏttÂŻ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be:ÏttÂŻ=818±8(stat)±27(syst)±19(lumi)±12(beam) pb, where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented
Cumulant to Factorial Moment Ratio and Multiplicity Data
The ratio of cumulant to factorial moments of experimental multiplicity
distributions has been calculated for and interactions in a
wide range of energies. As a function of the rank it exhibits an initial steep
decrease and a series of oscillations around zero. Those features cannot be
reproduced by the Negative Binomial Distribution. A comparable behaviour is
instead predicted in high-energy perturbative QCD. The presence of a
qualitatively similar behaviour for different processes and in wide energy
intervals suggests speaking of an approximate scaling of the cumulant to
factorial moment ratio.Comment: Submitted to Phys.Lett.B; Latex document, 11 pages, 4 PostScript
figures appended. Preprint number FIAN/TD-15/93 also FNT/AE 93-2
Bottom-Tau Unification in SUSY SU(5) GUT and Constraints from b to s gamma and Muon g-2
An analysis is made on bottom-tau Yukawa unification in supersymmetric (SUSY)
SU(5) grand unified theory (GUT) in the framework of minimal supergravity, in
which the parameter space is restricted by some experimental constraints
including Br(b to s gamma) and muon g-2. The bottom-tau unification can be
accommodated to the measured branching ratio Br(b to s gamma) if superparticle
masses are relatively heavy and higgsino mass parameter \mu is negative. On the
other hand, if we take the latest muon g-2 data to require positive SUSY
contributions, then wrong-sign threshold corrections at SUSY scale upset the
Yukawa unification with more than 20 percent discrepancy. It has to be
compensated by superheavy threshold corrections around the GUT scale, which
constrains models of flavor in SUSY GUT. A pattern of the superparticle masses
preferred by the three requirements is also commented.Comment: 21pages, 6figure
Virtual LSPs at e+ e- Colliders
Currently popular search strategies for supersymmetric particles may be
significantly affected due to relatively light sneutrinos which decay
dominantly into invisible channels. In certain cases the second lightest
neutralino may also decay invisibly leading to two extra carriers of missing
energy (in addition to the lightest supersymmetric particle (LSP)) -- the
virtual LSPs (VLSPs). It is shown that if the sneutrino masses happen to be in
the small but experimentally allowed range ~ 45 - 55 GeV, these particles
together with neutralino pairs may contribute significantly to the missing
energy in the process e+ e- ---> \gamma + missing energy at LEP-2 energies as
an enhancement over the Standard Model or the conventional MSSM predictions. It
is further shown that a much larger region of the parameter space can be
scanned at a high luminosity e+ e- collider at 500 GeV like the proposed NLC
machine. Moreover this process can play a complementary role to direct chargino
searches at LEP-2 and NLC which may fail due to a near mass degeneracy of the
chargino and the sneutrino. Formulae for the cross sections taking into account
full mixings of the charginos and the neutralinos are derived. The signal
remains observable even in the context of more restricted models based on N=1
SUGRA with common scalar and gaugino masses. The effect of soft photon
brehmsstrahlung on the signal is also discussed briefly.Comment: 51 pages, LaTeX plus 13 postscript figures included using epsfig in
uuencoded and compressed form, minor comments adde
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