1,758 research outputs found
Higgs and Dark Matter Hints of an Oasis in the Desert
Recent LHC results suggest a standard model (SM)-like Higgs boson in the
vicinity of 125 GeV with no clear indications yet of physics beyond the SM. At
the same time, the SM is incomplete, since additional dynamics are required to
accommodate cosmological dark matter (DM). In this paper we show that
interactions between weak scale DM and the Higgs which are strong enough to
yield a thermal relic abundance consistent with observation can easily
destabilize the electroweak vacuum or drive the theory into a non-perturbative
regime at a low scale. As a consequence, new physics--beyond the DM
itself--must enter at a cutoff well below the Planck scale and in some cases as
low as O(10 - 1000 TeV), a range relevant to indirect probes of flavor and CP
violation. In addition, this cutoff is correlated with the DM mass and
scattering cross-section in a parameter space which will be probed
experimentally in the near term. Specifically, we consider the SM plus
additional spin 0 or 1/2 states with singlet, triplet, or doublet electroweak
quantum numbers and quartic or Yukawa couplings to the Higgs boson. We derive
explicit expressions for the full two-loop RGEs and one-loop threshold
corrections for these theories.Comment: 29 pages, 13 figure
Ultraviolet asymptotics of scalar and pseudoscalar correlators in hot Yang-Mills theory
Inspired by recent lattice measurements, we determine the short-distance (a
> omega >> pi T) asymptotics
of scalar (trace anomaly) and pseudoscalar (topological charge density)
correlators at 2-loop order in hot Yang-Mills theory. The results are expressed
in the form of an Operator Product Expansion. We confirm and refine the
determination of a number of Wilson coefficients; however some discrepancies
with recent literature are detected as well, and employing the correct values
might help, on the qualitative level, to understand some of the features
observed in the lattice measurements. On the other hand, the Wilson
coefficients show slow convergence and it appears uncertain whether this
approach can lead to quantitative comparisons with lattice data. Nevertheless,
as we outline, our general results might serve as theoretical starting points
for a number of perhaps phenomenologically more successful lines of
investigation.Comment: 27 pages. v2: minor improvements, published versio
Electroweak Gauge-Boson Production at Small q_T: Infrared Safety from the Collinear Anomaly
Using methods from effective field theory, we develop a novel, systematic
framework for the calculation of the cross sections for electroweak gauge-boson
production at small and very small transverse momentum q_T, in which large
logarithms of the scale ratio M_V/q_T are resummed to all orders. These cross
sections receive logarithmically enhanced corrections from two sources: the
running of the hard matching coefficient and the collinear factorization
anomaly. The anomaly leads to the dynamical generation of a non-perturbative
scale q_* ~ M_V e^{-const/\alpha_s(M_V)}, which protects the processes from
receiving large long-distance hadronic contributions. Expanding the cross
sections in either \alpha_s or q_T generates strongly divergent series, which
must be resummed. As a by-product, we obtain an explicit non-perturbative
expression for the intercept of the cross sections at q_T=0, including the
normalization and first-order \alpha_s(q_*) correction. We perform a detailed
numerical comparison of our predictions with the available data on the
transverse-momentum distribution in Z-boson production at the Tevatron and LHC.Comment: 34 pages, 9 figure
The white matter is a pro-differentiative niche for glioblastoma
Glioblastomas are hierarchically organised tumours driven by glioma stem cells that retain partial differentiation potential. Glioma stem cells are maintained in specialised microenvironments, but whether, or how, they undergo lineage progression outside of these niches remains unclear. Here we identify the white matter as a differentiative niche for glioblastomas with oligodendrocyte lineage competency. Tumour cells in contact with white matter acquire pre-oligodendrocyte fate, resulting in decreased proliferation and invasion. Differentiation is a response to white matter injury, which is caused by tumour infiltration itself in a tumoursuppressive feedback loop. Mechanistically, tumour cell differentiation is driven by selective white matter upregulation of SOX10, a master regulator of normal oligodendrogenesis. SOX10 overexpression or treatment with myelination-promoting agents that upregulate endogenous SOX10, mimic this response, leading to niche-independent pre-oligodendrocyte differentiation and tumour suppression in vivo. Thus, glioblastoma recapitulates an injury response and exploiting this latent programme may offer treatment opportunities for a subset of patients
Multilevel Deconstruction of the In Vivo Behavior of Looped DNA-Protein Complexes
Protein-DNA complexes with loops play a fundamental role in a wide variety of
cellular processes, ranging from the regulation of DNA transcription to
telomere maintenance. As ubiquitous as they are, their precise in vivo
properties and their integration into the cellular function still remain
largely unexplored. Here, we present a multilevel approach that efficiently
connects in both directions molecular properties with cell physiology and use
it to characterize the molecular properties of the looped DNA-lac repressor
complex while functioning in vivo. The properties we uncover include the
presence of two representative conformations of the complex, the stabilization
of one conformation by DNA architectural proteins, and precise values of the
underlying twisting elastic constants and bending free energies. Incorporation
of all this molecular information into gene-regulation models reveals an
unprecedented versatility of looped DNA-protein complexes at shaping the
properties of gene expression.Comment: Open Access article available at
http://www.plosone.org/article/fetchArticle.action?articleURI=info%3Adoi%2F10.1371%2Fjournal.pone.000035
Analytic Results for Higgs Production in Bottom Fusion
We evaluate analytically the cross section for Higgs production plus one jet
through bottom quark fusion. By considering the small pT limit we derive
expressions for the resummation coefficients governing the structure of large
logarithms, and compare these expressions with those available in the
literature.Comment: 14 pages, 7 figure
The Bulk Channel in Thermal Gauge Theories
We investigate the thermal correlator of the trace of the energy-momentum
tensor in the SU(3) Yang-Mills theory. Our goal is to constrain the spectral
function in that channel, whose low-frequency part determines the bulk
viscosity. We focus on the thermal modification of the spectral function,
. Using the operator-product expansion we give
the high-frequency behavior of this difference in terms of thermodynamic
potentials. We take into account the presence of an exact delta function
located at the origin, which had been missed in previous analyses. We then
combine the bulk sum rule and a Monte-Carlo evaluation of the Euclidean
correlator to determine the intervals of frequency where the spectral density
is enhanced or depleted by thermal effects. We find evidence that the thermal
spectral density is non-zero for frequencies below the scalar glueball mass
and is significantly depleted for .Comment: (1+25) pages, 6 figure
QCD corrections to plus -boson production at the LHC
The associated production at the LHC is an important process in
investigating the color-octet mechanism of non-relativistic QCD in describing
the processes involving heavy quarkonium. We calculate the next-to-leading
order (NLO) QCD corrections to the associated production at the
LHC within the factorization formalism of nonrelativistic QCD, and provide the
theoretical predictions for the distribution of the transverse
momentum. Our results show that the differential cross section at the
leading-order is significantly enhanced by the NLO QCD corrections. We conclude
that the LHC has the potential to verify the color-octet mechanism by measuring
the production events.Comment: 14 page revtex, 5 eps figures, to appear in JHEP. fig5 and the
corresponding analysis are correcte
An effective theory for jet propagation in dense QCD matter: jet broadening and medium-induced bremsstrahlung
Two effects, jet broadening and gluon bremsstrahlung induced by the
propagation of a highly energetic quark in dense QCD matter, are reconsidered
from effective theory point of view. We modify the standard Soft Collinear
Effective Theory (SCET) Lagrangian to include Glauber modes, which are needed
to implement the interactions between the medium and the collinear fields. We
derive the Feynman rules for this Lagrangian and show that it is invariant
under soft and collinear gauge transformations. We find that the newly
constructed theory SCET recovers exactly the general result for the
transverse momentum broadening of jets. In the limit where the radiated gluons
are significantly less energetic than the parent quark, we obtain a jet
energy-loss kernel identical to the one discussed in the reaction operator
approach to parton propagation in matter. In the framework of SCET we
present results for the fully-differential bremsstrahlung spectrum for both the
incoherent and the Landau-Pomeranchunk-Migdal suppressed regimes beyond the
soft-gluon approximation. Gauge invariance of the physics results is
demonstrated explicitly by performing the calculations in both the light-cone
and covariant gauges. We also show how the process-dependent
medium-induced radiative corrections factorize from the jet production cross
section on the example of the quark jets considered here.Comment: 52 pages, 15 pdf figures, as published in JHE
Enhancing lepton flavour violation in the supersymmetric inverse seesaw beyond the dipole contribution
In minimal supersymmetric models the -penguin usually provides
sub-dominant contributions to charged lepton flavour violating observables. In
this study, we consider the supersymmetric inverse seesaw in which the
non-minimal particle content allows for dominant contributions of the
-penguin to several lepton flavour violating observables. In particular, and
due to the low-scale (TeV) seesaw, the penguin contribution to, for instance,
\Br(\mu \to 3e) and conversion in nuclei, allows to render some of
these observables within future sensitivity reach. Moreover, we show that in
this framework, the -penguin exhibits the same non-decoupling behaviour
which had previously been identified in flavour violating Higgs decays in the
Minimal Supersymmetric Standard Model.Comment: 29 pages, 9 figures, 4 tables; v2: minor corrections, version to
appear in JHE
- …