873 research outputs found
Light dark sectors through the Fermion portal
Abstract
Pairs of Standard Model fermions form dimension-3 singlet operators that can couple to new dark sector states. This âfermion portalâ is to be contrasted with the lower-dimensional Higgs, vector and neutrino singlet portals. We characterise its distinct phenomenology and place effective field theory bounds on this framework, focusing on the case of fermion portals to a pair of light dark sector fermions. We obtain current and projected limits on the dimension-6 effective operator scale from a variety of meson decay experiments, missing energy and long-lived particle searches at colliders, as well as astrophysical and cosmological bounds. The DarkEFT public code is made available for recasting these limits, which we illustrate with various examples including an integrated- out heavy dark photon.</jats:p
Accretion Processes for General Spherically Symmetric Compact Objects
We investigate the accretion process for different spherically symmetric
space-time geometries for a static fluid. We analyse this procedure using the
most general black hole metric ansatz. After that, we examine the accretion
process for specific spherically symmetric metrics obtaining the velocity of
the sound during the process and the critical speed of the flow of the fluid
around the black hole. In addition, we study the behaviour of the rate of
change of the mass for each chosen metric for a barotropic fluid.Comment: 10 pages, 15 figures, v2 accepted for publication in 'European
Physical Journal C
A dust-parallax distance of 19 megaparsecs to the supermassive black hole in NGC 4151
The active galaxy NGC 4151 has a crucial role as one of only two active
galactic nuclei for which black hole mass measurements based on emission line
reverberation mapping can be calibrated against other dynamical methods.
Unfortunately, effective calibration requires an accurate distance to NGC 4151,
which is currently not available. Recently reported distances range from 4 to
29 megaparsecs (Mpc). Strong peculiar motions make a redshift-based distance
very uncertain, and the geometry of the galaxy and its nucleus prohibit
accurate measurements using other techniques. Here we report a dust-parallax
distance to NGC 4151 of Mpc. The measurement is
based on an adaptation of a geometric method proposed previously using the
emission line regions of active galaxies. Since this region is too small for
current imaging capabilities, we use instead the ratio of the
physical-to-angular sizes of the more extended hot dust emission as determined
from time-delays and infrared interferometry. This new distance leads to an
approximately 1.4-fold increase in the dynamical black hole mass, implying a
corresponding correction to emission line reverberation masses of black holes
if they are calibrated against the two objects with additional dynamical
masses.Comment: Authors' version of a letter published in Nature (27 November 2014);
8 pages, 5 figures, 1 tabl
Drug-microenvironment perturbations reveal resistance mechanisms and prognostic subgroups in CLL
The tumour microenvironment and genetic alterations collectively influence drug efficacy in cancer, but current evidence is limited and systematic analyses are lacking. Using chronic lymphocytic leukaemia (CLL) as a model disease, we investigated the influence of 17 microenvironmental stimuli on 12 drugs in 192 genetically characterised patient samples. Based on microenvironmental response, we identified four subgroups with distinct clinical outcomes beyond known prognostic markers. Response to multiple microenvironmental stimuli was amplified in trisomy 12 samples. Trisomy 12 was associated with a distinct epigenetic signature. Bromodomain inhibition reversed this epigenetic profile and could be used to target microenvironmental signalling in trisomy 12 CLL. We quantified the impact of microenvironmental stimuli on drug response and their dependence on genetic alterations, identifying interleukin 4 (IL4) and Toll-like receptor (TLR) stimulation as the strongest actuators of drug resistance. IL4 and TLR signalling activity was increased in CLL-infiltrated lymph nodes compared with healthy samples. High IL4 activity correlated with faster disease progression. The publicly available dataset can facilitate the investigation of cell-extrinsic mechanisms of drug resistance and disease progression
Supersymmetric Monojets at the Large Hadron Collider
Supersymmetric monojets may be produced at the Large Hadron Collider by the
process qg -> squark neutralino_1 -> q neutralino_1 neutralino_1, leading to a
jet recoiling against missing transverse momentum. We discuss the feasibility
and utility of the supersymmetric monojet signal. In particular, we examine the
possible precision with which one can ascertain the neutralino_1-squark-quark
coupling via the rate for monojet events. Such a coupling contains information
on the composition of the neutralino_1 and helps bound dark matter direct
detection cross-sections and the dark matter relic density of the neutralino_1.
It also provides a check of the supersymmetric relation between gauge couplings
and gaugino-quark-squark couplings.Comment: 46 pages, 10 figures. The appendix has been rewritten to correct an
error that appears in all previous versions of the appendix. This error has
no effect on the results in the main body of the pape
Accelerated expansion from ghost-free bigravity: a statistical analysis with improved generality
We study the background cosmology of the ghost-free, bimetric theory of
gravity. We perform an extensive statistical analysis of the model using both
frequentist and Bayesian frameworks and employ the constraints on the expansion
history of the Universe from the observations of supernovae, the cosmic
microwave background and the large scale structure to estimate the model's
parameters and test the goodness of the fits. We explore the parameter space of
the model with nested sampling to find the best-fit chi-square, obtain the
Bayesian evidence, and compute the marginalized posteriors and mean
likelihoods. We mainly focus on a class of sub-models with no explicit
cosmological constant (or vacuum energy) term to assess the ability of the
theory to dynamically cause a late-time accelerated expansion. The model
behaves as standard gravity without a cosmological constant at early times,
with an emergent extra contribution to the energy density that converges to a
cosmological constant in the far future. The model can in most cases yield very
good fits and is in perfect agreement with the data. This is because many
points in the parameter space of the model exist that give rise to
time-evolution equations that are effectively very similar to those of the
CDM. This similarity makes the model compatible with observations as
in the CDM case, at least at the background level. Even though our
results indicate a slightly better fit for the CDM concordance model
in terms of the -value and evidence, none of the models is statistically
preferred to the other. However, the parameters of the bigravity model are in
general degenerate. A similar but perturbative analysis of the model as well as
more data will be required to break the degeneracies and constrain the
parameters, in case the model will still be viable compared to the
CDM.Comment: 42 pages, 9 figures; typos corrected in equations (2.12), (2.13),
(3.7), (3.8) and (3.9); more discussions added (footnotes 5, 8, 10 and 13)
and abstract, sections 4.2, 4.3 and 5 (conclusions) modified in response to
referee's comments; references added; acknowledgements modified; all results
completely unchanged; matches version accepted for publication in JHE
Classical Mus musculus IgÎș Enhancers Support Transcription but not High Level Somatic Hypermutation from a V-Lambda Promoter in Chicken DT40 Cells
Somatic hypermutation (SHM) of immunoglobulin genes is initiated by activation-induced cytidine deaminase (AID) in activated B cells. This process is strictly dependent on transcription. Hence, cis-acting transcriptional control elements have been proposed to target SHM to immunoglobulin loci. The Mus musculus IgÎș locus is regulated by the intronic enhancer (iE/MAR) and the 3âČ enhancer (3âČE), and multiple studies using transgenic and knock-out approaches in mice and cell lines have reported somewhat contradictory results about the function of these enhancers in AID-mediated sequence diversification. Here we show that the M. musculus iE/MAR and 3âČE elements are active solely as transcriptional enhancer when placed in the context of the IGL locus in Gallus gallus DT40 cells, but they are very inefficient in targeting AID-mediated mutation events to this locus. This suggests that either key components of the cis-regulatory targeting elements reside outside the murine IgÎș transcriptional enhancer sequences, or that the targeting of AID activity to Ig loci occurs by largely species-specific mechanisms
In vitro measurement of temperature changes during implantation of cemented glenoid components
Background and purpose It is unclear whether the increase in temperature during cement curing may cause osteonecrosis, leading to loosening of the glenoid component in shoulder arthroplasty. We therefore analyzed the temperature during implantation of cemented glenoid implants
Proliferative Hypothalamic Neurospheres Express NPY, AGRP, POMC, CART and Orexin-A and Differentiate to Functional Neurons
Some pathological conditions with feeding pattern alterations, including obesity and Huntington disease (HD) are associated with hypothalamic dysfunction and neuronal cell death. Additionally, the hypothalamus is a neurogenic region with the constitutive capacity to generate new cells of neuronal lineage, in adult rodents
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