15 research outputs found
QCD resummation in the framework of supersymmetry
Motivated by current searches for electroweak superpartners at the Large
Hadron Collider, we present precision predictions for pair production of such
particles in the framework of the Minimal Supersymmetric Standard Model. We
make use of various QCD resummation formalisms and match the results to pure
perturbative QCD computations. We study the impact of scale variations and
compare our results to predictions obtained by means of traditionally used
Monte Carlo event generators.Comment: 4 pages, 2 figures, contribution to the proceedings of Moriond QCD
201
Revisiting slepton pair production at the Large Hadron Collider
Motivated by the shift in experimental attention towards electroweak
supersymmetric particle production at the CERN LHC, we update in this paper our
precision predictions at next-to-leading order of perturbative QCD matched to
resummation at the next-to-leading logarithmic accuracy for direct slepton pair
production in proton-proton collisions. Simplified models, now commonly adopted
by the experimental collaborations for selectrons and smuons as well as mixing
staus, are used as benchmarks for total cross sections at achieved and future
center-of-mass energies. They are presented together with the corresponding
scale and parton density uncertainties in graphical and tabular form for future
reference. Using modern Monte Carlo techniques, we also reanalyze recent ATLAS
and CMS slepton searches in light of our precision cross sections and for
various assumptions on the decomposition of the sleptons and their neutralino
decay products.Comment: 32 pages, 10 figures, 4 tables; version accepted by JHE
NLO+NLL limits on and gauge boson masses
QCD resummation predictions for the production of new charged () and
neutral () heavy gauge bosons decaying leptonically are presented. These
results are obtained with our resummation code at next-to-leading order and
next-to-leading logarithmic (NLO+NLL) accuracy. Our predictions are compared to
PYTHIA at leading order (LO) supplemented with parton showers (PS) and FEWZ at
NLO and next-to-next-to-leading order (NNLO) for the -differential and
total cross sections in the Sequential Standard Model (SSM) and general
SU(2)SU(2)U(1) models. We show that the importance of
resummation for total cross sections increases with the gauge boson mass.
Finally, the latest ATLAS and CMS results are reinterpreted to derive new
limits at NLO+NLL on and boson masses in general extensions of the
Standard Model.Comment: Proceeding of the XXIII International Workshop on Deep Inelastic
Scattering and Related Subjects, April 27 - May 1, 2015, Southern Methodist
University, Dallas, Texa
QCD RESUMMATION IN THE FRAMEWORK OF SUPERSYMMETRY
Motivated by current searches for electroweak superpartners at the Large Hadron Collider, we present precision predictions for pair production of such particles in the framework of the Minimal Supersymmetric Standard Model. We make use of various QCD resummation formalisms and match the results to pure perturbative QCD computations. We study the impact of scale variations and compare our results to predictions obtained by means of traditionally used Monte Carlo event generators
Gaugino production in proton-proton collisions at a center-of-mass energy of 8 TeV
Motivated by hints for a light Standard Model-like Higgs boson and a shift in
experimental attention towards electroweak supersymmetry particle production at
the CERN LHC, we update in this paper our precision predictions at
next-to-leading order of perturbative QCD matched to resummation at the
next-to-leading logarithmic accuracy for direct gaugino pair production in
proton-proton collisions with a center-of-mass energy of 8 TeV. Tables of total
cross sections are presented together with the corresponding scale and parton
density uncertainties for benchmark points adopted recently by the experimental
collaborations, and figures are presented for up-to-date model lines attached
to them. Since the experimental analyses are currently obtained with parton
showers matched to multi-parton matrix elements, we also analyze the precision
of this procedure by comparing invariant-mass and transverse-momentum
distributions obtained in this way to those obtained with threshold and
transverse-momentum resummation.Comment: 28 pages, 7 figures, 9 tables; version to appear in JHE
Precision predictions for electroweak superpartner production at hadron colliders with Resummino
We describe the Resummino package, a C++ and Fortran program dedicated to
precision calculations in the framework of gaugino and slepton pair production
at hadron colliders. This code allows to calculate transverse-momentum and
invariant-mass distributions as well as total cross sections by combining the
next-to-leading order predictions obtained by means of perturbative QCD with
the resummation of the large logarithmic contributions arising in the small
transverse-momentum region and close to the production threshold. The results
computed in this way benefit from reduced theoretical uncertainties, compared
to a pure next-to-leading order approach as currently employed in the
experimental analyses searching for sleptons and gauginos at hadron colliders.
This is illustrated by using of Resummino in the context of a typical
supersymmetric benchmark point dedicated to superpartner searches at the Large
Hadron Collider.Comment: 9 pages, 1 figure, 1 table; version accepted by EPJC; program to be
downloaded from http://www.resummino.or
Lepton flavor violation and scalar dark matter in a radiative model of neutrino masses
Abstract We consider a simple extension of the Standard Model that can account for the dark matter and explain the existence of neutrino masses. The model includes a vector-like doublet of SU(2), a singlet fermion, and two scalar singlets, all of them odd under a new Z 2 symmetry. Neutrino masses are generated radiatively by one-loop processes involving the new fields, while the dark matter candidate is the lightest neutral particle among them. We focus specifically on the case where the dark matter particle is one of the scalars and its relic density is determined by its Yukawa interactions. The phenomenology of this setup, including neutrino masses, dark matter and lepton flavor violation, is analyzed in some detail. We find that the dark matter mass must be below 600 GeV to satisfy the relic density constraint. Lepton flavor violating processes are shown to provide the most promising way to test this scenario. Future μ→3e and μ –e conversion experiments, in particular, have the potential to probe the entire viable parameter space of this model
Assessment of the cryoprotectant concentration inside a bulky organ for cryopreservation using X-ray computed tomography
Cryoprotection of bulky organs is crucial for their storage and for subsequent transplantation. In this work we demonstrate the capability of the X-ray computed tomography (CT) as a non-invasive method to measure the cryoprotectant (cpa) concentration inside a tissue or an organ, specifically for the case of dymethil sulfoxide (Me2SO). It is remarkable that the use of Me2SO has been leader in techniques of cells and tissues cryopreservation. Although CT technologies are mainly based in density differences, and many cpas are alcohols with densities similar to water, the use of very low energies as acceleration voltage (~70 kV) and the sulfur atom in the molecule of Me2SO makes possible the visualization of this cpa inside tissues. As result we obtain a CT signal proportional to the Me2SO concentration with a spatial resolution up to 50 μm in the case of our device.This study has been funded by the Junta de Andalucía (Programa de Excelencia, 2008: P08-CTS-03965), supported by the Centro Nacional de Aceleradores, the University of Seville and the INIA project RTA2012-006.Peer Reviewe