109 research outputs found
Digitization of Library Collection in Nigerian University Libraries: University of Ilorin Library Experience
The aim of this paper is to discuss the difficulties that the University of Ilorin library encountered in its digitization project and how these difficulties were handled to ensure a robust digitization outfit. The idea is to alert Nigerian Libraries which are yet to embark on digitization on some of the problems or challenges that they are likely to encounter in planning and implementing a digitization project. Admittedly, some of the problems may be unique to University of Ilorin Library but it can be said with a fair degree of accuracy that some of the problems the University of Ilorin Library encountered are general at the planning and the implementation stages. In this paper, the conception, the planning and the implementation stages of the project will be discussed. Problems will be highlighted and suggestions will be made for an effective and efficient digital service delivery
MFV Reductions of MSSM Parameter Space
The 100+ free parameters of the minimal supersymmetric standard model (MSSM)
make it computationally difficult to compare systematically with data,
motivating the study of specific parameter reductions such as the cMSSM and
pMSSM. Here we instead study the reductions of parameter space implied by using
minimal flavour violation (MFV) to organise the R-parity conserving MSSM, with
a view towards systematically building in constraints on flavour-violating
physics. Within this framework the space of parameters is reduced by expanding
soft supersymmetry-breaking terms in powers of the Cabibbo angle, leading to a
24-, 30- or 42-parameter framework (which we call MSSM-24, MSSM-30, and MSSM-42
respectively), depending on the order kept in the expansion. We provide a
Bayesian global fit to data of the MSSM-30 parameter set to show that this is
manageable with current tools. We compare the MFV reductions to the
19-parameter pMSSM choice and show that the pMSSM is not contained as a subset.
The MSSM-30 analysis favours a relatively lighter TeV-scale pseudoscalar Higgs
boson and with multi-TeV sparticles.Comment: 2nd version, minor comments and references added, accepted for
publication in JHE
The impact of the ATLAS zero-lepton, jets and missing momentum search on a CMSSM fit
Recent ATLAS data significantly extend the exclusion limits for
supersymmetric particles. We examine the impact of such data on global fits of
the constrained minimal supersymmetric standard model (CMSSM) to indirect and
cosmological data. We calculate the likelihood map of the ATLAS search, taking
into account systematic errors on the signal and on the background. We validate
our calculation against the ATLAS determinaton of 95% confidence level
exclusion contours. A previous CMSSM global fit is then re-weighted by the
likelihood map, which takes a bite at the high probability density region of
the global fit, pushing scalar and gaugino masses up.Comment: 16 pages, 7 figures. v2 has bigger figures and fixed typos. v3 has
clarified explanation of our handling of signal systematic
Modified Signals for Supersymmetry in the NMSSM with a Singlino-like LSP
In the framework of the NMSSM with a singlino-like LSP, we study
quantitatively the impact of the additional bino -> singlino cascade on the
efficiencies in several search channels for supersymmetry of the ATLAS and CMS
collaborations. Compared to the MSSM, the additional cascade reduces the
missing transverse energy, but leads to additional jets or leptons. For the
NMSSM benchmark lines which generalize cMSSM benchmark points, the efficiencies
in the most relevant 2/3 jet + missing energy search channels can drop by
factors ~1/3 to ~1/7, and can reduce the present lower bounds on M_{1/2} by as
much as ~0.9 - 0.75 in the NMSSM for large bino-singlino mass differences. The
larger efficiencies in multijet or multilepton search channels are not strong
enough to affect this conclusion. In the fully constrained cNMSSM, sparticle
decay cascades via the lightest stau can lead to signal cross sections in
multilepton and 2tau search channels which are potentially visible at the LHC
with 7 TeV center of mass energy.Comment: 24 pages, 9 Figures, misprint in Table 1 correcre
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
Sphalerons and the Electroweak Phase Transition in Models with Higher Scalar Representations
In this work we investigate the sphaleron solution in a
gauge theory, which also encompasses the Standard Model, with higher scalar
representation(s) (). We show that the field profiles
describing the sphaleron in higher scalar multiplet, have similar trends like
the doublet case with respect to the radial distance. We compute the sphaleron
energy and find that it scales linearly with the vacuum expectation value of
the scalar field and its slope depends on the representation. We also
investigate the effect of gauge field and find that it is small for the
physical value of the mixing angle, and resembles the case for the
doublet. For higher representations, we show that the criterion for strong
first order phase transition, , is relaxed with respect to
the doublet case, i.e. .Comment: 20 pages, 5 figures & 1 table, published versio
Implications of LHC Searches on SUSY Particle Spectra: The pMSSM Parameter Space with Neutralino Dark Matter
We study the implications of LHC searches on SUSY particle spectra using flat
scans of the 19-parameter pMSSM phase space. We apply constraints from flavour
physics, g_mu-2, dark matter and earlier LEP and Tevatron searches. The
sensitivity of the LHC SUSY searches with jets, leptons and missing energy is
assessed by reproducing with fast simulation the recent CMS analyses after
validation on benchmark points. We present results in terms of the fraction of
pMSSM points compatible with all the constraints which are excluded by the LHC
searches with 1 fb^{-1} and 15 fb^{-1} as a function of the mass of strongly
and weakly interacting SUSY particles. We also discuss the suppression of Higgs
production cross sections for the MSSM points not excluded and contrast the
region of parameter space tested by the LHC data with the constraints from dark
matter direct detection experiments.Comment: 14 pages, 13 figures. v2: increased statistics, to appear in EPJ
Interpreting LHC SUSY searches in the phenomenological MSSM
We interpret within the phenomenological MSSM (pMSSM) the results of SUSY
searches published by the CMS collaboration based on the first ~1 fb^-1 of data
taken during the 2011 LHC run at 7 TeV. The pMSSM is a 19-dimensional
parametrization of the MSSM that captures most of its phenomenological
features. It encompasses, and goes beyond, a broad range of more constrained
SUSY models. Performing a global Bayesian analysis, we obtain posterior
probability densities of parameters, masses and derived observables. In
contrast to constraints derived for particular SUSY breaking schemes, such as
the CMSSM, our results provide more generic conclusions on how the current data
constrain the MSSM.Comment: 15 pages, 7 figures; minor revision, some references and a comment on
prior dependence added; version accepted by JHE
Accidental Inflation in String Theory
We show that inflation in type IIB string theory driven by the volume modulus
can be realized in the context of the racetrack-based Kallosh-Linde model (KL)
of moduli stabilization. Inflation here arises through the volume modulus
slow-rolling down from a flat hill-top or inflection point of the scalar
potential. This situation can be quite generic in the landscape, where by
uplifting one of the two adjacent minima one can turn the barrier either to a
flat saddle point or to an inflection point supporting eternal inflation. The
resulting spectral index is tunable in the range of 0.93 < n_s < 1, and there
is only negligible production of primordial gravitational waves r < 10^{-6}.
The flatness of the potential in this scenario requires fine-tuning, which may
be justified taking into account the exponential reward by volume factors
preferring the regions of the universe with the maximal amount of slow-roll
inflation. This consideration leads to a tentative prediction of the spectral
index or depending on whether the
potential has a symmetry phi -> - phi or not.Comment: 15 pages, 6 figures, LaTeX, uses RevTex
Tuning supersymmetric models at the LHC: A comparative analysis at two-loop level
We provide a comparative study of the fine tuning amount (Delta) at the
two-loop leading log level in supersymmetric models commonly used in SUSY
searches at the LHC. These are the constrained MSSM (CMSSM), non-universal
Higgs masses models (NUHM1, NUHM2), non-universal gaugino masses model (NUGM)
and GUT related gaugino masses models (NUGMd). Two definitions of the fine
tuning are used, the first (Delta_{max}) measures maximal fine-tuning wrt
individual parameters while the second (Delta_q) adds their contribution in
"quadrature". As a direct result of two theoretical constraints (the EW minimum
conditions), fine tuning (Delta_q) emerges as a suppressing factor (effective
prior) of the averaged likelihood (under the priors), under the integral of the
global probability of measuring the data (Bayesian evidence p(D)). For each
model, there is little difference between Delta_q, Delta_{max} in the region
allowed by the data, with similar behaviour as functions of the Higgs, gluino,
stop mass or SUSY scale (m_{susy}=(m_{\tilde t_1} m_{\tilde t_2})^{1/2}) or
dark matter and g-2 constraints. The analysis has the advantage that by
replacing any of these mass scales or constraints by their latest bounds one
easily infers for each model the value of Delta_q, Delta_{max} or vice versa.
For all models, minimal fine tuning is achieved for M_{higgs} near 115 GeV with
a Delta_q\approx Delta_{max}\approx 10 to 100 depending on the model, and in
the CMSSM this is actually a global minimum. Due to a strong (
exponential) dependence of Delta on M_{higgs}, for a Higgs mass near 125 GeV,
the above values of Delta_q\approx Delta_{max} increase to between 500 and
1000. Possible corrections to these values are briefly discussed.Comment: 23 pages, 46 figures; references added; some clarifications (section
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