403 research outputs found
Searching for the QCD Axion with Gravitational Microlensing
The phase transition responsible for axion dark matter production can create
large amplitude isocurvature perturbations which collapse into dense objects
known as axion miniclusters. We use microlensing data from the EROS survey, and
from recent observations with the Subaru Hyper Suprime Cam to place constraints
on the minicluster scenario. We compute the microlensing event rate for
miniclusters treating them as spatially extended objects with an extended mass
function. Using the published bounds on the number of microlensing events we
bound the fraction of DM collapsed into miniclusters, . For an
axion with temperature dependent mass consistent with the QCD axion we find
, which represents the first
observational constraint on the minicluster fraction. We forecast that a
high-efficiency observation of ten nights with Subaru would be sufficient to
constrain over the entire QCD axion mass range. We
make various approximations to derive these constraints and dedicated analyses
by the observing teams of EROS and Subaru are necessary to confirm our results.
If accurate theoretical predictions for can be made in future then
microlensing can be used to exclude, or discover, the QCD axion. Further
details of our computations are presented in a companion paper.Comment: 5 pages, 4 figures, v2 contains an improved description of our
modeling of miniclusters and lensing with revised limits, matches version
accepted in PR
Fully covering the MSSM Higgs sector at the LHC
In the context of the Minimal Supersymmetric extension of the Standard Model
(MSSM), we reanalyze the search for the heavier CP-even and CP-odd
neutral Higgs bosons at the LHC in their production in the gluon-fusion
mechanism and their decays into gauge and lighter bosons and into top quark
pairs. We show that only when considering these processes, that one can fully
cover the entire parameter space of the Higgs sector of the model. Indeed, they
are sensitive to the low and high Higgs mass ranges, complementing
the traditional searches for high mass resonances decaying into -lepton
pairs which are instead sensitive to the large and moderate
regions. The complementarity of the various channels in the probing of the
complete MSSM parameter space at the previous and upcoming
phases of the LHC is illustrated in a recently proposed simple and model
independent approach for the Higgs sector, the MSSM, that we also refine in
this paper.Comment: 44 pages, 21 figures, pdflate
The measurement of the Higgs self-coupling at the LHC: theoretical status
Now that the Higgs boson has been observed by the ATLAS and CMS experiments
at the LHC, the next important step would be to measure accurately its
properties to establish the details of the electroweak symmetry breaking
mechanism. Among the measurements which need to be performed, the determination
of the Higgs self-coupling in processes where the Higgs boson is produced in
pairs is of utmost importance. In this paper, we discuss the various processes
which allow for the measurement of the trilinear Higgs coupling: double Higgs
production in the gluon fusion, vector boson fusion, double Higgs-strahlung and
associated production with a top quark pair. We first evaluate the production
cross sections for these processes at the LHC with center-of-mass energies
ranging from the present TeV to TeV, and discuss
their sensitivity to the trilinear Higgs coupling. We include the various
higher order QCD radiative corrections, at next-to-leading order for gluon and
vector boson fusion and at next-to-next-to-leading order for associated double
Higgs production with a gauge boson. The theoretical uncertainties on these
cross sections are estimated. Finally, we discuss the various channels which
could allow for the detection of the double Higgs production signal at the LHC
and the accuracy on the self-coupling that could be ultimately achieved.Comment: 37 pages, 10 tables, 17 figures. Typos corrected, matches the journal
versio
The post-Higgs MSSM scenario: Habemus MSSM?
We analyze the Minimal Supersymmetric extension of the Standard Model that we
have after the discovery of the Higgs boson at the LHC, the hMSSM (habemus
MSSM?), i.e. a model in which the lighter boson has a mass of approximately
125 GeV which, together with the non-observation of superparticles at the LHC,
indicates that the SUSY-breaking scale is rather high, TeV. We
first demonstrate that the value GeV fixes the dominant
radiative corrections that enter the MSSM Higgs boson masses, leading to a
Higgs sector that can be described, to a good approximation, by only two free
parameters. In a second step, we consider the direct supersymmetric radiative
corrections and show that, to a good approximation, the phenomenology of the
lighter Higgs state can be described by its mass and three couplings: those to
massive gauge bosons and to top and bottom quarks. We perform a fit of these
couplings using the latest LHC data on the production and decay rates of the
light boson and combine it with the limits from the negative search of the
heavier and states, taking into account the current
uncertainties.Comment: 1+12 pages, pdflatex, 7 figure
AutoPSI: a database for automatic structural classification of protein sequences and structures
In protein research, structural classifications of protein domains provided by databases such as SCOP play an important role. However, as such databases have to be curated and prepared carefully, they update only up to a few times per year, and in between newly entered PDB structures cannot be used in cases where a structural classification is required. The Automated Protein Structure Identification (AutoPSI) database delivers predicted SCOP classifications for several thousand yet unclassified PDB entries as well as millions of UniProt sequences in an automated fashion. In order to obtain predictions, we make use of two recently published methods, namely AutoSCOP (sequence-based) and Vorolign (structure-based) and the consensus of both. With our predictions, we bridge the gap between SCOP versions for proteins with known structures in the PDB and additionally make structure predictions for a very large number of UniProt proteins. AutoPSI is freely accessible at http://www.bio.ifi.lmu.de/AutoPSIDB
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The fermionic universal one-loop effective action
Abstract
Recent development of path integral matching techniques based on the covariant derivative expansion has made manifest a universal structure of one-loop effective Lagrangians. The universal terms can be computed once and for all to serve as a reference for one-loop matching calculations and to ease their automation. Here we present the fermionic universal one-loop effective action (UOLEA), resulting from integrating out heavy fermions (Dirac or Majorana) with scalar, pseudo-scalar, vector and axial-vector couplings. We also clarify the relation of the new terms computed here to terms previously computed in the literature and those that remain to complete the UOLEA. Our results can be readily used to efficiently obtain analytical expressions for effective operators arising from heavy fermion loops [13].</jats:p
GW182-Free microRNA Silencing Complex Controls Post-transcriptional Gene Expression during Caenorhabditis elegans Embryogenesis
MicroRNAs and Argonaute form the microRNA induced silencing complex or miRISC that recruits GW182, causing mRNA degradation and/or translational repression. Despite the clear conservation and molecular significance, it is unknown if miRISC-GW182 interaction is essential for gene silencing during animal development. Using Caenorhabditis elegans to explore this question, we examined the relationship and effect on gene silencing between the GW182 orthologs, AIN-1 and AIN-2, and the microRNA-specific Argonaute, ALG-1. Homology modeling based on human Argonaute structures indicated that ALG-1 possesses conserved Tryptophan-binding Pockets required for GW182 binding. We show in vitro and in vivo that their mutations severely altered the association with AIN-1 and AIN-2. ALG-1 tryptophan-binding pockets mutant animals retained microRNA-binding and processing ability, but were deficient in reporter silencing activity. Interestingly, the ALG-1 tryptophan-binding pockets mutant phenocopied the loss of alg-1 in worms during larval stages, yet was sufficient to rescue embryonic lethality, indicating the dispensability of AINs association with the miRISC at this developmental stage. The dispensability of AINs in miRNA regulation is further demonstrated by the capacity of ALG-1 tryptophan-binding pockets mutant to regulate a target of the embryonic mir-35 microRNA family. Thus, our results demonstrate that the microRNA pathway can act independently of GW182 proteins during C. elegans embryogenesis
A new bioinformatics analysis tools framework at EMBL–EBI
The EMBL-EBI provides access to various mainstream sequence analysis applications. These include sequence similarity search services such as BLAST, FASTA, InterProScan and multiple sequence alignment tools such as ClustalW, T-Coffee and MUSCLE. Through the sequence similarity search services, the users can search mainstream sequence databases such as EMBL-Bank and UniProt, and more than 2000 completed genomes and proteomes. We present here a new framework aimed at both novice as well as expert users that exposes novel methods of obtaining annotations and visualizing sequence analysis results through one uniform and consistent interface. These services are available over the web and via Web Services interfaces for users who require systematic access or want to interface with customized pipe-lines and workflows using common programming languages. The framework features novel result visualizations and integration of domain and functional predictions for protein database searches. It is available at http://www.ebi.ac.uk/Tools/sss for sequence similarity searches and at http://www.ebi.ac.uk/Tools/msa for multiple sequence alignments
Java GUI for InterProScan (JIPS): A tool to help process multiple InterProScans and perform ortholog analysis
BACKGROUND: Recent, rapid growth in the quantity of available genomic data has generated many protein sequences that are not yet biochemically classified. Thus, the prediction of biochemical function based on structural motifs is an important task in post-genomic analysis. The InterPro databases are a major resource for protein function information. For optimal results, these databases should be searched at regular intervals, since they are frequently updated. RESULTS: We describe here a new program JIPS (Java GUI for InterProScan), a tool for tracking and viewing results obtained from repeated InterProScan searches. JIPS stores matches (in a local database) obtained from InterProScan searches performed with multiple versions of the InterPro database and highlights hits that have been added since the last search of the InterPro database. Results are displayed in an easy-to-use tabular format. JIPS also contains tools to assist with ortholog-based comparative studies of protein signatures. CONCLUSION: JIPS is an efficient tool for performing repeated InterProScans on large batches of protein sequences, tracking and viewing search results, and mining the collected data
Direct detection of Higgs-portal dark matter at the LHC
We consider the process in which a Higgs particle is produced in association
with jets and show that monojet searches at the LHC already provide interesting
constraints on the invisible decays of a 125 GeV Higgs boson. Using the
existing monojet searches performed by CMS and ATLAS, we show the 95%
confidence level limit on the invisible Higgs decay rate is of the order of the
total Higgs production rate in the Standard Model. This limit could be
significantly improved when more data at higher center of mass energies are
collected, provided systematic errors on the Standard Model contribution to the
monojet background can be reduced. We also compare these direct constraints on
the invisible rate with indirect ones based on measuring the Higgs rates in
visible channels. In the context of Higgs portal models of dark matter, we then
discuss how the LHC limits on the invisible Higgs branching fraction impose
strong constraints on the dark matter scattering cross section on nucleons
probed in direct detection experiments.Comment: 6 pages, 3 figures; v2: references added; v3: monojet and Higgs data
updated, version published in EPJ
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