1,119 research outputs found
The light-quark contribution to the leading HVP term of the muon from twisted-mass fermions
We present a lattice calculation of the leading Hadronic Vacuum Polarization
(HVP) contribution of the light u- and d-quarks to the anomalous magnetic
moment of the muon, , adopting the gauge configurations
generated by the European Twisted Mass Collaboration with
dynamical quarks at three values of the lattice spacing with pion masses in the
range 210 - 450 MeV. Thanks to several lattices at fixed values of the
light-quark mass and scale but with different sizes we perform a careful
investigation of finite-volume effects (FVEs). In order to remove FVEs we
develop an analytic representation of the vector correlator, which describes
the lattice data for time distances larger than fm. The
representation is based on quark-hadron duality at small and intermediate time
distances and on the two-pion contributions in a finite box at larger time
distances. After extrapolation to the physical pion point and to the continuum
limit we obtain . Adding the
contribution of strange and charm quarks, obtained by ETMC, and an estimate of
the isospin-breaking corrections and quark-disconnected diagrams from the
literature we get , which is
consistent with recent results based on dispersive analyses of the experimental
cross section data for annihilation into hadrons. Using our analytic
representation of the vector correlator, taken at the physical pion mass in the
continuum and infinite volume limits, we provide the first eleven moments of
the polarization function and we compare them with recent results of the
dispersive analysis of the channels. We estimate also the
light-quark contribution to the missing part of not covered
in the MUonE experiment.Comment: 34 pages, 20 figures, 7 tables. Version to appear in PR
Electromagnetic and strong isospin-breaking corrections to the muon from Lattice QCD+QED
We present a lattice calculation of the leading-order electromagnetic and
strong isospin-breaking corrections to the hadronic vacuum polarization (HVP)
contribution to the anomalous magnetic moment of the muon. We employ the gauge
configurations generated by the European Twisted Mass Collaboration (ETMC) with
dynamical quarks at three values of the lattice spacing ( fm) with pion masses between and
MeV. The results are obtained adopting the RM123 approach in the
quenched-QED approximation, which neglects the charges of the sea quarks. Quark
disconnected diagrams are not included. After the extrapolations to the
physical pion mass and to the continuum and infinite-volume limits the
contributions of the light, strange and charm quarks are respectively equal to
, and . At leading order in and we obtain , which is currently the most accurate determination of the
isospin-breaking corrections to .Comment: 23 pages, 7 figures, 5 tables. Version to appear in PRD. A bug in the
update of the strange and charm contributions is removed and an extended
discussion on the identification of the ground-state is included. arXiv admin
note: text overlap with arXiv:1808.00887, arXiv:1707.0301
Leading isospin-breaking corrections to pion, kaon and charmed-meson masses with Twisted-Mass fermions
We present a lattice computation of the isospin-breaking corrections to
pseudoscalar meson masses using the gauge configurations produced by the
European Twisted Mass collaboration with dynamical quarks at
three values of the lattice spacing ( and fm)
with pion masses in the range MeV. The strange and
charm quark masses are tuned at their physical values. We adopt the RM123
method based on the combined expansion of the path integral in powers of the
- and -quark mass difference () and of the
electromagnetic coupling . Within the quenched QED approximation,
which neglects the effects of the sea-quark charges, and after the
extrapolations to the physical pion mass and to the continuum and infinite
volume limits, we provide results for the pion, kaon and (for the first time)
charmed-meson mass splittings, for the prescription-dependent parameters
, \epsilon_\gamma(\overline{MS}, 2~\mbox{GeV}),
\epsilon_{K^0}(\overline{MS}, 2~\mbox{GeV}), related to the violations of the
Dashen's theorem, and for the light quark mass difference (\widehat{m}_d -
\widehat{m}_u)(\overline{MS}, 2~\mbox{GeV}).Comment: 47 pages, 20 figures, 4 tables; comments on QED and QCD splitting
prescriptions added; version to appear in PR
Strange and charm HVP contributions to the muon ( including QED corrections with twisted-mass fermions
We present a lattice calculation of the Hadronic Vacuum Polarization (HVP)
contribution of the strange and charm quarks to the anomalous magnetic moment
of the muon including leading-order electromagnetic corrections. We employ the
gauge configurations generated by the European Twisted Mass Collaboration
(ETMC) with dynamical quarks at three values of the lattice
spacing ( fm) with pion masses in the range
MeV. The strange and charm quark masses are tuned at
their physical values. Neglecting disconnected diagrams and after the
extrapolations to the physical pion mass and to the continuum limit we obtain:
,
and
,
for the strange
and charm contributions, respectively.Comment: 34 pages, 10 figures, 5 tables; version to appear in JHE
The effectiveness of intra-articular injectionc of Hyalubrix combined with exercise therapy in the tratment of hip osteoarthritis
Purpose. Osteoarthritis (OA) is the most common joint
disorder in the elderly, causing significant pain which
negatively affects mobility and quality ol liie. The aim of
the study was to assess the effectiveness of ultrasound
\ucdmage-guided intra-articular injections of Hyalubrix@ combined
with exercise therapy in the treatment of hip osteoarthritis.
Methods. This was a single site, prosp\ue8ctive, open-fabel,
Investigator-initiated study. Forty patients rilere enrolled
and received three ultrasound image.guided injections
of Hyalubrix@, 45 days apart, combined with three sessions
a week of phys\uedcal therapy (proprioceptive rehabilitation
of the lower limbs; gait training; balance training)
up to a total of 30 sessions (10 weeks), starting from one
week after the first injection.
Results. The primary obiective was to achieve a lasting
reduction in OA symptoms related to pain during activity.
During the course of the study the pain perceived by
the patient during activity dropped from a mean value of
6.94 cm to a mean value of 1.46 cm and showed a statistically
significant decrease from visit 1 compared to
baseline (p < 0.05) which was confirmed at all the subsequent
time points. Significant improvements were also
observed in the evaluation of the secondary objectives:
hip disability; OA-related pain at rest; daily functioning
and NSAIDs intake.
Conclusions. Results from this study including 40 patients
for a total of 65 treated hips demonstrate a significant improvement in OA-related pain, hip disability, and
patient's daily functioning as well as a reduction in
NSAIDS intake. Patients suffering from hip OA s\ue8em to
benefil from the treatment wiih Hyalubrix@ injections
plus exercise therapy
First lattice calculation of the QED corrections to leptonic decay rates
The leading-order electromagnetic and strong isospin-breaking corrections to
the ratio of and decay rates are evaluated for the
first time on the lattice, following a method recently proposed. The lattice
results are obtained using the gauge ensembles produced by the European Twisted
Mass Collaboration with dynamical quarks. Systematics effects
are evaluated and the impact of the quenched QED approximation is estimated.
Our result for the correction to the tree-level decay
ratio is to be compared to the estimate based
on Chiral Perturbation Theory and adopted by the Particle Data Group.Comment: 5 pages, 6 figures; extended supplemental material with 1 table and 1
figure, results unchange
Light-meson leptonic decay rates in lattice QCD+QED
The leading electromagnetic (e.m.) and strong isospin-breaking corrections to
the and leptonic
decay rates are evaluated for the first time on the lattice. The results are
obtained using gauge ensembles produced by the European Twisted Mass
Collaboration with dynamical quarks. The relative
leading-order e.m.~and strong isospin-breaking corrections to the decay rates
are 1.53(19)\% for decays and 0.24(10)\% for decays.
Using the experimental values of the and decay rates
and updated lattice QCD results for the pion and kaon decay constants in
isosymmetric QCD, we find that the Cabibbo-Kobayashi-Maskawa matrix element , reducing by a factor of about the corresponding
uncertainty in the Particle Data Group review. Our calculation of
allows also an accurate determination of the first-row CKM unitarity relation
. Theoretical
developments in this paper include a detailed discussion of how QCD can be
defined in the full QCD+QED theory and an improved renormalisation procedure in
which the bare lattice operators are renormalised non-perturbatively into the
(modified) Regularization Independent Momentum subtraction scheme and
subsequently matched perturbatively at into the
W-regularisation scheme appropriate for these calculations.Comment: 63 pages, 10 figures and 2 tables. Version matches the published
pape
Effectiveness of sodium acetate treatment on the mechanical properties and morphology of natural fiber-reinforced composites
This paper aims to investigate the ability of an eco-friendly and cheap treatment based on sodium acetate solutions to improve the mechanical properties of flax fiber-reinforced composites. Flax fibers were treated for 5 days (i.e., 120 h) at 25â—¦C with mildly alkaline solutions at 5%, 10% and 20% weight content of the sodium salt. Quasi-static tensile and flexural tests, Charpy impact tests and dynamical mechanical thermal (DMTA) tests were carried out to evaluate the mechanical properties of the resulting composites. Fourier transform infrared analysis (FTIR) was used to evaluate the chemical modification on the fibers surface due to the proposed treatment, whereas scanning electron microscope (SEM) and helium pycnometry were used to get useful information about the morphology of composites. It was found that the treatment with 5% solution of sodium acetate leads to the best mechanical performance and morphology of flax fiber-reinforced composites. SEM analysis confirmed these findings highlighting that composites reinforced with flax fibers treated in 5% sodium acetate solution show an improved morphology compared to the untreated ones. On the contrary, detrimental effects on the morphology as well as on the mechanical performance of composites were achieved by increasing the salt concentration of the treating solution
Flax–Glass Fiber Reinforced Hybrid Composites Exposed to a Salt-Fog/Dry Cycle: A Simplified Approach to Predict Their Performance Recovery
Despite natural fibers gaining significant attention in recent decades, their limited performance and poor durability under humid environments cannot allow them to fully replace their synthetic counterparts as reinforcement for structural composites. In such a context, this paper aims to investigate how exposure to a humid/dry cycle affects the mechanical response of epoxy laminates reinforced with flax and glass fibers. In particular, the main goal is to assess the performance evolution of a glass–flax hybridized stacking sequence in comparison with the full glass and flax fiber reinforced composites. To this end, the investigated composites were first exposed to salt-fog for 15 or 30 days and then to dry conditions (i.e., 50% R.H. and 23 °C) for up to 21 days. The presence of glass fibers in the stacking sequence significantly stabilizes the mechanical performance of composites during the humid/dry cycle. Indeed, hybridization of inner flax laminae with outer glass ones, acting as a protective shield, hinders the composite degradation due to the humid phase also promoting performance recovery during the dry phase. Hence, this work showed that a tailored hybridization of natural fibers with glass fibers represents a suitable approach to extend the service-life of natural fiber reinforced composites exposed to discontinuous humid conditions, thus allowing their employment in practical indoor and outdoor applications. Finally, a simplified theoretical pseudo-second-order model that aimed to forecast the performance recovery shown by composites was proposed and experimentally validated, highlighting good agreement with the experimental data
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