1,311 research outputs found
Precision on leptonic mixing parameters at future neutrino oscillation experiments
We perform a comparison of the different future neutrino oscillation
experiments based on the achievable precision in the determination of the
fundamental parameters theta_{13} and the CP phase, delta, assuming that
theta_{13} is in the range indicated by the recent Daya Bay measurement. We
study the non-trivial dependence of the error on delta on its true value. When
matter effects are small, the largest error is found at the points where CP
violation is maximal, and the smallest at the CP conserving points. The
situation is different when matter effects are sizable. As a result of this
effect, the comparison of the physics reach of different experiments on the
basis of the CP discovery potential, as usually done, can be misleading. We
have compared various proposed super-beam, beta-beam and neutrino factory
setups on the basis of the relative precision of theta_{13} and the error on
delta. Neutrino factories, both high-energy or low-energy, outperform
alternative beam technologies. An ultimate precision on theta_{13} below 3% and
an error on delta of < 7^{\circ} at 1 sigma (1 d.o.f.) can be obtained at a
neutrino factory.Comment: Minor changes, matches version accepted in JHEP. 30 pages, 9 figure
On form factors in N=4 sym
In this paper we study the form factors for the half-BPS operators
and the stress tensor supermultiplet
current up to the second order of perturbation theory and for the
Konishi operator at first order of perturbation theory in
SYM theory at weak coupling. For all the objects we observe the
exponentiation of the IR divergences with two anomalous dimensions: the cusp
anomalous dimension and the collinear anomalous dimension. For the IR finite
parts we obtain a similar situation as for the gluon scattering amplitudes,
namely, apart from the case of and the finite part has
some remainder function which we calculate up to the second order. It involves
the generalized Goncharov polylogarithms of several variables. All the answers
are expressed through the integrals related to the dual conformal invariant
ones which might be a signal of integrable structure standing behind the form
factors.Comment: 35 pages, 7 figures, LATEX2
Viscoelastic gels of guar and xanthan gum mixtures provide long-term stabilization of iron micro- and nanoparticles
Iron micro- and nanoparticles used for groundwater remediation and medical applications are prone to fast aggregation and sedimentation. Diluted single biopolymer water solutions of guar gum (GG) or xanthan gum (XG) can stabilize these particles for few hours providing steric repulsion and by increasing the viscosity of the suspension. The goal of the study is to demonstrate that amending GG solutions with small amounts of XG (XG/GG weight ratio 1:19; 3 g/L of total biopolymer concentration) can significantly improve the capability of the biopolymer to stabilize highly concentrated iron micro- and nanoparticle suspensions. The synergistic effect between GG and XG generates a viscoelastic gel that can maintain 20 g/L iron particles suspended for over 24 h. This is attributed to (i) an increase in the static viscosity, (ii) a combined polymer structure the yield stress of which contrasts the downward stress exerted by the iron particles, and (iii) the adsorption of the polymers to the iron surface having an anchoring effect on the particles. The XG/GG viscoelastic gel is characterized by a marked shear thinning behavior. This property, coupled with the low biopolymer concentration, determines small viscosity values at high shear rates, facilitating the injection in porous media. Furthermore, the thermosensitivity of the soft elastic polymeric network promotes higher stability and longer storage times at low temperatures and rapid decrease of viscosity at higher temperatures. This feature can be exploited in order to improve the flowability and the delivery of the suspensions to the target as well as to effectively tune and control the release of the iron particle
Morphology and Nanomechanics of Sensory Neurons Growth Cones following Peripheral Nerve Injury
A prior peripheral nerve injury in vivo, promotes a rapid elongated mode of sensory neurons neurite regrowth in vitro. This in vitro model of conditioned axotomy allows analysis of the cellular and molecular mechanisms leading to an improved neurite re-growth. Our differential interference contrast microscopy and immunocytochemistry results show that conditioned axotomy, induced by sciatic nerve injury, did not increase somatic size of adult lumbar sensory neurons from mice dorsal root ganglia sensory neurons but promoted the appearance of larger neurites and growth cones. Using atomic force microscopy on live neurons, we investigated whether membrane mechanical properties of growth cones of axotomized neurons were modified following sciatic nerve injury. Our data revealed that neurons having a regenerative growth were characterized by softer growth cones, compared to control neurons. The increase of the growth cone membrane elasticity suggests a modification in the ratio and the inner framework of the main structural proteins
Large-Theta(13) Perturbation Theory of Neutrino Oscillation for Long-Baseline Experiments
The Cervera et al. formula, the best known approximate formula of neutrino
oscillation probability for long-baseline experiments, can be regarded as a
second-order perturbative formula with small expansion parameter epsilon \equiv
Delta m^2_{21} / Delta m^2_{31} \simeq 0.03 under the assumption s_{13} \simeq
epsilon. If theta_{13} is large, as suggested by a candidate nu_{e} event at
T2K as well as the recent global analyses, higher order corrections of s_{13}
to the formula would be needed for better accuracy. We compute the corrections
systematically by formulating a perturbative framework by taking theta_{13} as
s_{13} \sim \sqrt{epsilon} \simeq 0.18, which guarantees its validity in a wide
range of theta_{13} below the Chooz limit. We show on general ground that the
correction terms must be of order epsilon^2. Yet, they nicely fill the mismatch
between the approximate and the exact formulas at low energies and relatively
long baselines. General theorems are derived which serve for better
understanding of delta-dependence of the oscillation probability. Some
interesting implications of the large theta_{13} hypothesis are discussed.Comment: Fig.2 added, 23 pages. Matches to the published versio
The Custodial Randall-Sundrum Model: From Precision Tests to Higgs Physics
We reexamine the Randall-Sundrum (RS) model with enlarged gauge symmetry
SU(2)_L x SU(2)_R x U(1)_X x P_LR in the presence of a brane-localized Higgs
sector. In contrast to the existing literature, we perform the Kaluza-Klein
(KK) decomposition within the mass basis, which avoids the truncation of the KK
towers. Expanding the low-energy spectrum as well as the gauge couplings in
powers of the Higgs vacuum expectation value, we obtain analytic formulas which
allow for a deep understanding of the model-specific protection mechanisms of
the T parameter and the left-handed Z-boson couplings. In particular, in the
latter case we explain which contributions escape protection and identify them
with the irreducible sources of P_LR symmetry breaking. We furthermore show
explicitly that no protection mechanism is present in the charged-current
sector confirming existing model-independent findings. The main focus of the
phenomenological part of our work is a detailed discussion of Higgs-boson
couplings and their impact on physics at the CERN Large Hadron Collider. For
the first time, a complete one-loop calculation of all relevant Higgs-boson
production and decay channels is presented, incorporating the effects stemming
from the extended electroweak gauge-boson and fermion sectors.Comment: 74 pages, 13 figures, 3 tables. v2: Matches version published in JHE
Non-Standard Interactions at a Neutrino Factory: Correlations and CP violation
We explore the potential of several Neutrino Factory (NF) setups to
constrain, discover and measure new physics effects due to Non-Standard
Interactions (NSI) in propagation through Earth matter. We first study the
impact of NSI in the measurement of : we find that these could be
large due to strong correlations of with NSI parameters in the
golden channel, and the inclusion of a detector at the magic baseline is
crucial in order to reduce them as much as possible. We present, then, the
sensitivity of the considered NF setups to the NSI parameters, paying special
attention to correlations arising between them and the standard oscillation
parameters, when all NSI parameters are introduced at once. Off-diagonal NSI
parameters could be tested down to the level of , whereas the diagonal
combinations and
can be tested down to and
, respectively. The possibilities of observing CP violation in this
context are also explored, by presenting a first scan of the CP discovery
potential of the NF setups to the phases and
. We study separately the case where CP violation comes only from
non-standard sources, and the case where it is entangled with the standard
source, . In case turns out to be CP conserving, the
interesting possibility of observing CP violation for reasonably small values
of the NSI parameters emerges.Comment: Final note added. 38 pages, 11 figure
Structural characterization of diabolic acid-based tetraester, tetraether and mixed ether/ester, membrane-spanning lipids of bacteria from the order Thermotogales
The distribution of core lipids in the membranes of nine different species of the order Thermotogales, one of the early and deep branching lineages in the Bacteria, were examined by HPLC/MS and demonstrated to consist of membrane-spanning diglycerol lipids comprised of diabolic acid-derived alkyl moieties. In the Thermotoga species the core membrane lipids are characterized by the presence of both ester and ether bonds, whereas in the phylogenetically more distinct Thermosipho and Fervidobacterium spp. only ester bonds occur. A tentative biosynthetic route for the biosynthesis of these membrane-spanning lipids is proposed. Since species of the order Thermotogales are assumed to have occurred early during the evolution of life on Earth, as suggested by its position in the phylogenetic tree of life, these data suggest that the ability to produce both ether and ester glycerol membrane lipids developed relatively early during microbial evolution
Vata-L: Visual-Analogue Test Assessing Anosognosia for Language Impairment
Lack of awareness (anosognosia) for one's own language impairments has rarely been investigated, despite hampering language rehabilitation. Assessment of anosognosia by means of self-report is particularly complex, as a patient's language difficulties may seriously prevent or bias the assessment. Other methods, such as measures of self-correction and error detection, have provided valuable information, although they are an indirect form of assessment of anosognosia and are not exempt from methodological criticisms. In this study we report on a new tool, the VATA-L (Visual-Analogue Test for Anosognosia for Language impairment), geared at assessing explicit anosognosia for aphasia. The VATA-L compares the patient's self-evaluation with caregivers’ evaluations of the patient's verbal communication abilities in a series of common situations. By means of non-verbal support and a system of check questions, this test minimizes some of the methodological limitations of existing diagnostic tools (e.g., structured interviews), enhancing reliability, and enabling assessment of patients with aphasia. Finally, normative data provided in the study allow a clearer interpretation of the patient's performance and facilitate assessment of anosognosia
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