5,806 research outputs found
Towards Guidelines for Preventing Critical Requirements Engineering Problems
Context] Problems in Requirements Engineering (RE) can lead to serious
consequences during the software development lifecycle. [Goal] The goal of this
paper is to propose empirically-based guidelines that can be used by different
types of organisations according to their size (small, medium or large) and
process model (agile or plan-driven) to help them in preventing such problems.
[Method] We analysed data from a survey on RE problems answered by 228
organisations in 10 different countries. [Results] We identified the most
critical RE problems, their causes and mitigation actions, organizing this
information by clusters of size and process model. Finally, we analysed the
causes and mitigation actions of the critical problems of each cluster to get
further insights into how to prevent them. [Conclusions] Based on our results,
we suggest preliminary guidelines for preventing critical RE problems in
response to context characteristics of the companies.Comment: Proceedings of the 42th Euromicro Conference on Software Engineering
and Advanced Applications, 201
High P_T Leptons and W Production at HERA
Details are given of the observation by H1 of events containing high P_T
leptons in addition to large missing P_T. A closely related ZEUS analysis,
including a preliminary measurement of the W production cross section, is
discussed and the two experiments are compared. Some possible non-Standard
Model sources for the events are considered.Comment: 9 pages, 6 figures, LaTeX, uses iop style files and axodraw.sty. To
appear in the proceedings of the 3rd UK Phenomenology Workshop on HERA
Physics, September 1998, Durham (J.Phys.G: Nucl.Part.Phys.
Bose Condensation and the BTZ Black Hole
Although all popular approaches to quantum gravity are able to recover the
Bekenstein-Hawking entropy-area law in the thermodynamic limit, there are
significant differences in their descriptions of the microstates and in the
application of statistics. Therefore they can have significantly different
phenomenological implications. For example, requiring indistinguishability of
the elementary degrees of freedom should lead to changes in the black hole's
radiative porperties away from the thermodynamic limit and at low temperatures.
We demonstrate this for the Ba\~nados-Teitelboim-Zanelli (BTZ) black hole. The
energy eigenstates and statistical entropy in the thermodynamic limit of the
BTZ black hole were obtained earlier by us via symmetry reduced canonical
quantum gravity. In that model the BTZ black hole behaves as a system of
Bosonic mass shells moving in a one dimensional harmonic trap. Bose
condensation does not occur in the thermodynamic limit but this system
possesses a finite critical temperature, , and exhibits a large condensate
fraction below when the number of shells is finite.Comment: 5 pages, 5 figures. Published versio
On Evidence-based Risk Management in Requirements Engineering
Background: The sensitivity of Requirements Engineering (RE) to the context
makes it difficult to efficiently control problems therein, thus, hampering an
effective risk management devoted to allow for early corrective or even
preventive measures. Problem: There is still little empirical knowledge about
context-specific RE phenomena which would be necessary for an effective
context- sensitive risk management in RE. Goal: We propose and validate an
evidence-based approach to assess risks in RE using cross-company data about
problems, causes and effects. Research Method: We use survey data from 228
companies and build a probabilistic network that supports the forecast of
context-specific RE phenomena. We implement this approach using spreadsheets to
support a light-weight risk assessment. Results: Our results from an initial
validation in 6 companies strengthen our confidence that the approach increases
the awareness for individual risk factors in RE, and the feedback further
allows for disseminating our approach into practice.Comment: 20 pages, submitted to 10th Software Quality Days conference, 201
HERA Physics Beyond the Standard Model
The prospects of physics beyond the standard model in deep inelastic
scattering are reviewed, emphasizing some scenarios which attained attention
after the observation of an excess of events with large momentum transfer at
HERA.Comment: 8 pages, LaTeX, uses iop style files and axodraw.sty, Talk presented
at the 3rd UK Phenomenology Workshop on HERA Physics, September 1998, Durha
\mu to e in R-symmetric Supersymmetry
We demonstrate that mu/e slepton mixing is significantly more restricted than
previously thought within the already remarkably flavor-safe R-symmetric
supersymmetric standard model. We calculate bounds from mu to e gamma, mu to 3e
and, most importantly, mu to e conversion. The process mu to e conversion is
significantly more restrictive in R-symmetric models since this process can
occur through operators that do not require a chirality-flip. We delineate the
allowed parameter space, demonstrating that maximal mixing is rarely possible
with weak scale superpartners, while O(0.1) mixing is permitted within most of
the space. The best approach to find or rule out mu/e mixing in R-symmetric
supersymmetric models is a multi-pronged attack looking at both mu to e
conversion as well as mu to e gamma. The redundancy eliminates much of the
parameter space where one process, but not both processes, contain amplitudes
that accidentally destructively interfere. We briefly discuss implications for
searches of slepton flavor violation at the LHC.Comment: 31 pages, 16 figures; Typos fixed, minor corrections to fig. 13,
version published in PR
Propagators on the two-dimensional light-cone
Light-cone quantization procedure recently presented is applied to the
two-dimensional light-cone theories. By introducing the two distinct null
planes it is shown that the modification term in the two-dimensional massless
light-cone propagators suggested about twenty years ago vanishs.Comment: LATEX, 9page
R-parity violation and uses of the rare decay sneutrino-->gamma+gamma in hadron and photon colliders
We consider implications of the loop process sneutrino -> gamma gamma in the
MSSM with R-parity violation for future experiments, where the sneutrino is
produced as the only supersymmetric particle. We present a scenario for the
R-parity violating couplings, where this clean decay, although rare with
Br(sneutrino -> gamma gamma) ~ 10^{-6}, may be useful for sneutrino detection
over a range of sneutrino masses at the LHC. Furthermore, the new
sneutrino-gamma-gamma effective coupling may induce detectable sneutrino
resonant production in gamma gamma collisions, over a considerably wide mass
range. We compare sneutrino -> gamma gamma, gg throughout the paper with the
analogous yet quantitatively very different, Higgs -> gamma gamma, gg decays
and comment on the loop processes sneutrino -> WW, ZZ.Comment: 19 pages using REVTEX, 3 figures embadded in the text using epsfi
Broken R Parity Contributions to Flavor Changing Rates and CP Asymmetries in Fermion Pair Production at Leptonic Colliders
We examine the effects of the R parity odd renormalizable interactions on
flavor changing rates and CP violation asymmetries in the production of
fermion-antifermion pairs at leptonic colliders. The produced
fermions may be leptons, down-quarks or up-quarks, and the center of mass
energies may range from the Z-boson pole up to GeV. Off the Z-boson
pole, the flavor changing rates are controlled by tree level amplitudes and the
CP asymmetries by interference terms between tree and loop level amplitudes. At
the Z-boson pole, both observables involve loop amplitudes. The lepton number
violating interactions, associated with the coupling constants, \l_{ijk},
\l'_{ijk}, are only taken into account. The consideration of loop amplitudes
is restricted to the photon and Z-boson vertex corrections. We briefly review
flavor violation physics at colliders. We present numerical results using a
single, species and family independent, mass parameter, , for all the
scalar superpartners and considering simple assumptions for the family
dependence of the R parity odd coupling constants.Comment: Latex File. 23 pages. 4 postscript figures. 1 table. Revised version
with new results and several corrections in numerical result
R-parity violation and CP-violating and CP-conserving spin asymmetries in l^+ l^- -> sneutrino -> tau^+ tau^-: probing sneutrino mixing at LEP2, NLC and mu^+mu^- colliders
We consider the sneutrino resonance reaction l^+ l^- -> sneutrino -> tau^+
tau^- in the MSSM without R-parity. We introduce new CP-violating and
CP-conserving tau-spin asymmetries which are generated already at the
tree-level if there is sneutrino - sneutrino-bar mixing and that are forbidden
in the SM. It is remarkable that these spin asymmetries can reach ~75% around
resonance for a sneutrino mass splitting of \Delta m ~ \Gamma and ~10% for a
splitting as low as \Delta m ~ 0.1\Gamma, where \Gamma is the sneutrino width.
We show that they are easily detectable already at LEP2 so long as the beam
energy is within ~10 GeV range around the muon-sneutrino masses and may
therefore serve as extremely powerful probes of sneutrino mixing phenomena.Comment: 12 pages, plain latex, 3 figures embadded in the text using epsfi
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