620 research outputs found
Production and FCNC decay of supersymmetric Higgs bosons into heavy quarks in the LHC
We analyze the production and subsequent decay of the neutral MSSM Higgs
bosons (h = h^0, H^0, A^0) mediated by flavor changing neutral currents (FCNC)
in the LHC collider. We have computed the h-production cross-section times the
FCNC branching ratio, \sigma(pp -> h -> qq') = \sigma(pp -> h) B(h -> qq'), in
the LHC focusing on the strongly-interacting FCNC sector. Here qq' is an
electrically neutral pair of quarks of different flavors, the dominant modes
being those containing a heavy quark: tc or bs. We determine the maximum
production rates for each of these modes and identify the relevant regions of
the MSSM parameter space, after taking into account the severe restrictions
imposed by low energy FCNC processes. The analysis of \sigma(pp -> h -> qq')
singles out regions of the MSSM parameter space different from those obtained
by maximizing only the branching ratio, due to non-trivial correlations between
the parameters that maximize/minimize each isolated factor. The production
rates for the bs channel can be huge for a FCNC process (0.1-1 pb), but its
detection can be problematic. The production rates for the tc channel are more
modest (10^{-3}-10^{-2} pb), but its detection should be easier due to the
clear-cut top quark signature. A few thousand tc events could be collected in
the highest luminosity phase of the LHC, with no counterpart in the SM.Comment: 25 pages, 9 figures, 2 tables, LaTeX 2e. Typos corrected. Version to
appear in JHE
A new cell primo-culture method for freshwater benthic diatom communities
A new cell primo-culture method was developed for the benthic diatom community isolated from biofilm sampled in rivers. The approach comprised three steps: (1) scraping biofilm from river pebbles, (2) diatom isolation
from biofilm, and (3) diatom community culture. With a view to designing a method able to stimulate the growth of diatoms, to limit the development of other microorganisms, and to maintain in culture a community similar to the original natural one, different factors were tested in step 3:
cell culture medium (Chu No 10 vs Freshwater “WC” medium modified), cell culture vessel, and time of culture. The results showed that using Chu No 10 medium in an Erlenmeyer flask for cell culture was the optimal method,
producing enough biomass for ecotoxicological tests as well as minimising development of other microorganisms. After 96 h of culture, communities differed from the original communities sampled in the two rivers studied.
Species tolerant of eutrophic or saprobic conditions were favoured during culture. This method of diatom community culture affords the opportunity to assess, in vitro, the effects of different chemicals or effluents (water samples andindustrial effluents) on diatom communities, as well as on diatom cells, from a wide range of perspectives
One-loop calculations for SUSY processes
Strategy and results for complete one-loop computations in the Minimal
Supersymmetric Standard Model are reviewed, with applications to the
calculation of SUSY mass spectra and SUSY-particle processes. Determination of
renormalization constants and counterterms are described in the on-shell
renormalization scheme, and a translation between and on-shell
parameters is given. As an example, cross sections for chargino and neutralino
pair production in annihilation are presented, complete at the
one-loop level.Comment: Talk presented at Loops and Legs in Quantum Field Theory, Zinnowitz,
Germany, April 200
Fermionic decays of sfermions: a complete discussion at one-loop order
We present a definition of an on-shell renormalization scheme for the
sfermion and chargino-neutralino sector of the Minimal Supersymmetric Standard
Model (MSSM). Then, apply this renormalization framework to the interaction
between charginos/neutralinos and sfermions. A kind of universal corrections is
identified, which allow to define effective chargino/neutralino coupling
matrices. In turn, these interactions generate (universal) non-decoupling terms
that grow as the logarithm of the heavy mass. Therefore the full MSSM spectrum
must be taken into account in the computation of radiative corrections to
observables involving these interactions. As an application we analyze the full
one-loop electroweak radiative corrections to the partial decay widths
\Gamma(\tilde{f} -> f\neut) and \Gamma(\tilde{f} -> f'\cplus) for all sfermion
flavours and generations. These are combined with the QCD corrections to
compute the corrected branching ratios of sfermions. It turns out that the
electroweak corrections can have an important impact on the partial decay
widths, as well as the branching ratios, in wide regions of the parameter
space. The precise value of the corrections is strongly dependent on the
correlation between the different particle masses.Comment: LaTeX 53 pages, 22 figures, 3 tables. Typos correcte
Single top-quark production by strong and electroweak supersymmetric flavor-changing interactions at the LHC
(Abridged) We report on a complete study of the single top-quark production
by direct supersymmetric flavor-changing neutral-current (FCNC) processes at
the LHC. The total cross section for pp(gg)->t\bar{c}+\bar{t}c is computed at
the 1-loop order within the unconstrained Minimal Supersymmetric Standard Model
(MSSM). The present study extends the results of the supersymmetric strong
effects (SUSY-QCD), which were advanced by some of us in a previous work, and
includes the computation of the full supersymmetric electroweak corrections
(SUSY-EW). Our analysis of pp(gg)->t\bar{c}+\bar{t}c in the MSSM has been
performed in correspondence with the stringent low-energy constraints from b->s
gamma. In the most favorable scenarios, the SUSY-QCD contribution can give rise
to production rates of around 10^5 events per 100 fb^{-1} of integrated
luminosity. Furthermore, we show that there exist regions of the MSSM parameter
space where the SUSY-EW correction becomes sizeable. In the SUSY-EW favored
regions, one obtains lower, but still appreciable, event production rates that
can reach the 10^3 level for the same range of integrated luminosity. We study
also the possible reduction in the maximum event rate obtained from the full
MSSM contribution if we additionally include the constraints from
B^0_s-\bar{B}^0_s. In view of the fact that the FCNC production of heavy quark
pairs of different flavors is extremely suppressed in the SM, the detection of
a significant number of these events could lead to evidence of new physics --
of likely supersymmetric origin.Comment: LaTex, 35 pages, typos corrected. Version accepted in JHE
HETEROTOPIA WORK. Correlation between the domestic built environment and home offices during COVID-19 confinement
The new COVID-19 context has transported work to a domestic setting. These new locations, heterotopic, do not always adequately respond to user needs.This paper explores the relationship between the domestic built environment and certain elements that shape it, the perception, emotional state and productivity of the users.A pilot case study was carried out with 11 volunteers who evaluated their home offices for seven work days using physical environment tools, two tests -fixed data and daily evaluation-. Also, environmental parameters of the territory were monitored.Among the main findings, we observed that the perception of size does not relate to actual size; a balcony is associated with happiness and calm. We have verified how biophilic elements promote well-being. Happiness and calm are related to hight and low levels of lux. There is a tendency of happiness associated with collaborative tasks, and calm with individual ones. This article opens up a path for exploratory research on resilient situations in which physical barriers force people to seek creative solutions and offers tools to empower users. Current trends in data-driven design and teleworking support research proposals like this one, with a focus on well-being, productivity
Obstructed D-Branes in Landau-Ginzburg Orbifolds
We study deformations of Landau-Ginzburg D-branes corresponding to obstructed
rational curves on Calabi-Yau threefolds. We determine D-brane moduli spaces
and D-brane superpotentials by evaluating higher products up to homotopy in the
Landau-Ginzburg orbifold category. For concreteness we work out the details for
lines on a perturbed Fermat quintic. In this case we show that our results
reproduce the local analytic structure of the Hilbert scheme of curves on the
threefold.Comment: 44 pages; v3: typos correcte
MW and sin^2\theta_eff in Split SUSY: present and future expectations
We analyse the precision electroweak observables MW and sin^2\theta_eff and
their correlations in the recently proposed Split SUSY model. We compare the
results with the Standard Model and Minimal Supersymmetric Standard Model
predictions, and with present and future experimental accuracies. Present
experimental accuracies in (MW, sin^2\theta_eff) do not allow constraints to be
placed on the Split SUSY parameter space. We find that the shifts in (MW,
sin^2\theta_eff) induced by Split SUSY can be larger than the anticipated
accuracy of the GigaZ option of the International Linear Collider, and that the
most sensitive observable is sin^2\theta_eff. These large shifts are possible
also for large chargino masses in scenarios with small tan(\beta) =~ 1.Comment: LaTeX, 13 pages, 4 figures. Comments adde
Sfermion Precision Measurements at a Linear Collider
At future e+- e- linear colliders, the event rates and clean signals of
scalar fermion production - in particular for the scalar leptons - allow very
precise measurements of their masses and couplings and the determination of
their quantum numbers. Various methods are proposed for extracting these
parameters from the data at the sfermion thresholds and in the continuum. At
the same time, NLO radiative corrections and non-zero width effects have been
calculated in order to match the experimental accuracy. The substantial mixing
expected for the third generation sfermions opens up additional opportunities.
Techniques are presented for determining potential CP-violating phases and for
extracting tan(beta) from the stau sector, in particular at high values. The
consequences of possible large mass differences in the stop and sbottom system
are explored in dedicated analyses.Comment: Expanded version of contributions to the proceedings of ICHEP'02
(Amsterdam) and LCWS 2002 (Jeju Island
α-Tubulin detyrosination impairs mitotic error correction by suppressing MCAK centromeric activity
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