7,802 research outputs found
TeV gravity at neutrino telescopes
Cosmogenic neutrinos reach the Earth with energies around 10^9 GeV, and their
interactions with matter will be measured in upcoming experiments (Auger,
IceCube). Models with extra dimensions and the fundamental scale at the TeV
could imply signals in these experiments. In particular, the production of
microscopic black holes by cosmogenic neutrinos has been extensively studied in
the literature. Here we make a complete analysis of gravity-mediated
interactions at larger distances, where they can be calculated in the eikonal
approximation. In these processes a neutrino of energy E_\nu interacts
elastically with a parton inside a nucleon, loses a small fraction y of its
energy, and starts a hadronic shower of energy y E_\nu << E_\nu. We analyze the
ultraviolet dependence and the relevance of graviton emission in these
processes, and show that they are negligible. We also study the energy
distribution of cosmogenic events in AMANDA and IceCube and the possibility of
multiple-bang events. For any neutrino flux, the observation of an enhanced
rate of neutral current events above 100 TeV in neutrino telescopes could be
explained by TeV-gravity interactions. The values of the fundamental scale of
gravity that IceCube could reach are comparable to those to be explored at the
LHC.Comment: 10 pages, 7 figures; new section on air showers added, version to be
publishe
Probing TeV gravity at neutrino telescopes
Models with extra dimensions and the fundamental scale at the TeV could imply
sign als in large neutrino telescopes due to gravitational scattering of
cosmogenic neu trinos in the detection volume. Apart from the production of
microscopic black hol es, extensively studied in the literature, we present
gravity-mediated interactions at larger distances, that can be calculated in
the e ikonal approximation. In these elastic processes the neutrino loses a
small fracti on of energy to a hadronic shower and keeps going. The event rate
of these events is higher than that of black hole formation and the signal is
distinct: no charged leptons and possibly multiple-bang events.Comment: 5 pages; to appear in the proceedings of the Workshop on Exotic
Physics with Neutrino Telesocpes, Uppsala 20-22 September 200
Origin of the high energy neutrino flux at IceCube
We discuss the spectrum of the different components in the astrophysical
neutrino flux reaching the Earth and the possible contribution of each
component to the high-energy IceCube data. We show that the diffuse flux from
cosmic ray interactions with gas in our galaxy implies just 2 events among the
54 event sample. We argue that the neutrino flux from cosmic ray interactions
in the intergalactic (intracluster) space depends critically on the transport
parameter describing the energy dependence in the diffusion
coefficient of galactic cosmic rays. Our analysis motivates a E^{-2.1} neutrino
spectrum with a drop at PeV energies that fits well the data, including the
non-observation of the Glashow resonance at 6.3 PeV. We also show that a cosmic
ray flux described by an unbroken power law may produce a neutrino flux with
interesting spectral features (bumps and breaks) related to changes in the
cosmic ray composition.Comment: 19 pages, new section about changes in CR composition, version to
appear in Ap
The social brain meets the reactive genome: neuroscience, epigenetics and the new social biology
The rise of molecular epigenetics over the last few years promises to bring the discourse about the sociality and susceptibility to environmental influences of the brain to an entirely new level. Epigenetics deals with molecular mechanisms such as gene expression, which may embed in the organism âmemoriesâ of social experiences and environmental exposures. These changes in gene expression may be transmitted across generations without changes in the DNA sequence. Epigenetics is the most advanced example of the new postgenomic and context-dependent view of the gene that is making its way into contemporary biology. In my article I will use the current emergence of epigenetics and its link with neuroscience research as an example of the new, and in a way unprecedented, sociality of contemporary biology. After a review of the most important developments of epigenetic research, and some of its links with neuroscience, in the second part I reflect on the novel challenges that epigenetics presents for the social sciences for a re-conceptualization of the link between the biological and the social in a postgenomic age. Although epigenetics remains a contested, hyped, and often uncritical terrain, I claim that especially when conceptualized in broader non-genecentric frameworks, it has a genuine potential to reformulate the ossified biology/society debate
Cosmogenic neutrinos and signals of TeV gravity in air showers and neutrino telescopes
The existence of extra dimensions allows the possibility that the fundamental
scale of gravity is at the TeV. If that is the case, gravity could dominate the
interactions of ultra-high energy cosmic rays. In particular, the production of
microscopic black holes by cosmogenic neutrinos has been estimated in a number
of papers. We consider here gravity-mediated interactions at larger distances,
where they can be calculated in the eikonal approximation. We show that for the
expected flux of cosmogenic neutrinos these elastic processes give a stronger
signal than black hole production in neutrino telescopes. Taking the bounds on
the higher dimensional Planck mass M_D (D=4+n) from current air shower
experiments, for n=2 (6) elastic collisions could produce up to 118 (34) events
per year at IceCube. On the other hand, the absence of any signal would imply a
bound of M_D>~5 TeV.Comment: 10 pages, 1 figure; version to appear in Phys. Rev. Let
New Synthetic Endocannabinoid as Anti-Inflammaging Cosmetic Active: an In Vitro Study on a Reconstructed Skin Model
Endocannabinoids have been recently appointed as interesting cosmetic actives in regulating inflammaging, a state of chronic low-grade inflammation, known for being involved in many senescence\u2019s manifestations, included skin aging. The aim of this study was to assess the anti-inflammaging activity of a new synthetic endocannabinoid, Isopalmide\uae, on a reconstructed skin model, on which inflammaging has been reproduced through UVA radiation and light mechanical stress. We tested Isopalmide\uae both as a single active and conveyed in a cosmetic product, in comparison with Anandamide, a well-known natural endocannabinoid with anti-inflammatory action. The anti-inflammaging activity of topically applied products has been assessed, after 6 hours of treatment post-irradiation, through the transcriptional modification of genes involved in the NF-\u3baB pathway and the epigenetic pathway targeting miRs as potential biomarkers of inflammaging: miR-21, miR-126 and miR-146a. The results confirmed the anti-inflammatory action of Anandamide which inhibits NF-\u3baB, while Isopalmide\uae showed its anti-inflammaging activity through the establishment of an inflammatory/anti-inflammatory balance by maintaining NF-\u3baB inactive in the cytoplasm and active in the nucleus. The anti-inflammaging activity was shown also by the cosmetic product containing Isopalmide
New physics from ultrahigh energy cosmic rays
Cosmic rays from outer space enter the atmosphere with energies of up to
10^{11} GeV. The initial particle or a secondary hadron inside the shower may
then interact with an air nucleon to produce nonstandard particles. In this
article we study the production of new physics by high energy cosmic rays,
focusing on the long-lived gluino of split-SUSY models and a WIMP working as
dark matter. We first deduce the total flux of hadron events at any depth in
the atmosphere, showing that secondary hadrons can not be neglected. Then we
use these results to find the flux of gluinos and WIMPs that reach the ground
after being produced inside air showers. We also evaluate the probability of
producing these exotic particles in a single proton shower of ultrahigh energy.
Finally we discuss the possible signal in current and projected experiments.
While the tiny flux of WIMPs does not seem to have any phenomenological
consequences, we show that the gluinos could modify substantially the profile
of a small fraction of extensive air showers. In particular, they could produce
a distinct signal observable at AUGER in showers of large zenith angle.Comment: 9 pages, version to appear in PR
Perturbative and non-perturbative renormalization results of the Chromomagnetic Operator on the Lattice
The Chromomagnetic operator (CMO) mixes with a large number of operators
under renormalization. We identify which operators can mix with the CMO, at the
quantum level. Even in dimensional regularization (DR), which has the simplest
mixing pattern, the CMO mixes with a total of 9 other operators, forming a
basis of dimension-five, Lorentz scalar operators with the same flavor content
as the CMO. Among them, there are also gauge noninvariant operators; these are
BRST invariant and vanish by the equations of motion, as required by
renormalization theory. On the other hand using a lattice regularization
further operators with will mix; choosing the lattice action in a
manner as to preserve certain discrete symmetries, a minimul set of 3
additional operators (all with ) will appear. In order to compute all
relevant mixing coefficients, we calculate the quark-antiquark (2-pt) and the
quark-antiquark-gluon (3-pt) Green's functions of the CMO at nonzero quark
masses. These calculations were performed in the continuum (dimensional
regularization) and on the lattice using the maximally twisted mass fermion
action and the Symanzik improved gluon action. In parallel, non-perturbative
measurements of the matrix element are being performed in simulations
with 4 dynamical () twisted mass fermions and the Iwasaki improved
gluon action.Comment: 7 pages, 1 figure, 3 tables, LATTICE2014 proceeding
matrix elements of the chromomagnetic operator on the lattice
We present the results of the first lattice QCD calculation of the matrix elements of the chromomagnetic operator , which appears in the effective Hamiltonian
describing transitions in and beyond the Standard Model. Having
dimension 5, the chromomagnetic operator is characterized by a rich pattern of
mixing with operators of equal and lower dimensionality. The multiplicative
renormalization factor as well as the mixing coefficients with the operators of
equal dimension have been computed at one loop in perturbation theory. The
power divergent coefficients controlling the mixing with operators of lower
dimension have been determined non-perturbatively, by imposing suitable
subtraction conditions. The numerical simulations have been carried out using
the gauge field configurations produced by the European Twisted Mass
Collaboration with dynamical quarks at three values of the
lattice spacing. Our result for the B-parameter of the chromomagnetic operator
at the physical pion and kaon point is , while
in the SU(3) chiral limit we obtain . Our findings are
significantly smaller than the model-dependent estimate ,
currently used in phenomenological analyses, and improve the uncertainty on
this important phenomenological quantity.Comment: 20 pages, 4 figures, 2 table. Refined SU(3) ChPT analysis with no
changes in the final result. Version to appear in PR
The chromomagnetic operator on the lattice
We study matrix elements of the "chromomagnetic" operator on the lattice.
This operator is contained in the strangeness-changing effective Hamiltonian
which describes electroweak effects in the Standard Model and beyond.
Having dimension 5, the chromomagnetic operator is characterized by a rich
pattern of mixing with other operators of equal and lower dimensionality,
including also non gauge invariant quantities; it is thus quite a challenge to
extract from lattice simulations a clear signal for the hadronic matrix
elements of this operator.
We compute all relevant mixing coefficients to one loop in lattice
perturbation theory; this necessitates calculating both 2-point
(quark-antiquark) and 3-point (gluon-quark-antiquark) Green's functions at
nonzero quark masses. We use the twisted mass lattice formulation, with
Symanzik improved gluon action.
For a comprehensive presentation of our results, along with detailed
explanations and a more complete list of references, we refer to our
forthcoming publication [1].Comment: 7 pages, 1 figure. Talk presented at the 31st International Symposium
on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz,
German
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