399 research outputs found
Extraction of and from experimental decay rates using lattice QCD form factors
We present a determination of the Cabibbo-Kobayashi-Maskawa matrix elements
and obtained by combining the momentum dependence of the
semileptonic vector form factors and , recently determined from lattice QCD simulations, with the
differential rates measured for the semileptonic and decays. Our analysis is based on the results for the
semileptonic form factors produced by the European Twisted Mass Collaboration
with flavors of dynamical quarks in the whole range of values
of the squared 4-momentum transfer accessible in the experiments. The
statistical and systematic correlations between the lattice data as well as
those present in the experimental data are properly taken into account. With
respect to the standard procedure based on the use of only the vector form
factor at zero 4-momentum transfer, we obtain more precise and consistent
results: and . The
second-row CKM unitarity is fulfilled within the current uncertainties:
. Moreover, using for the
first time hadronic inputs determined from first principles, we have calculated
the ratio of the semileptonic decay rates into muons and
electrons, which represent a test of lepton universality within the SM,
obtaining in the isospin-symmetric limit of QCD: and .Comment: 8 pages, 2 figures, 8 tables. Version to appear in EPJ
Hypercubic effects in semileptonic decays of heavy mesons, toward , with Twisted fermions
We present a preliminary study toward a lattice determination of the vector
and scalar form factors of the semileptonic decays. We
compute the form factors relative to the transition between heavy-light
pseudoscalar mesons, with masses above the physical D-mass, and the pion. We
simulate heavy-quark masses in the range .
Lorentz symmetry breaking due to hypercubic effects is clearly observed in the
data, and included in the decomposition of the current matrix elements in terms
of additional form factors. We discuss the size of this breaking as the
parent-meson mass increases. Our analysis is based on the gauge configurations
produced by the European Twisted Mass Collaboration with
flavors of dynamical quarks at three different values of the lattice spacing
and with pion masses as small as MeV.Comment: 7 pages, 5 figures; contribution to the XXXVI International Symposium
on Lattice Field Theory (LATTICE2018), East Lansing (Michigan State
University, USA), July 22-28, 201
Masses and decay constants of mesons with twisted mass fermions
We present a preliminary lattice determination of the masses and decay
constants of the pseudoscalar and vector mesons and . Our analysis
is based on the gauge configurations produced by the European Twisted Mass
Collaboration with flavors of dynamical quarks. We simulated
at three different values of the lattice spacing and with pion masses as small
as 210 MeV. Heavy-quark masses are simulated directly on the lattice up to
times the physical charm mass. The physical b-quark mass is reached
using the ETMC ratio method. Our preliminary results are: MeV, MeV, and .Comment: 7 pages, 3 figures, 1 table; contribution to the proceedings of the
XXXVI Int'l Workshop on Lattice Field Theory (LATTICE2018), July 22-28, 2018,
East Lansing, Michigan State University (Michigan, USA
Dispersive analysis of the experimental data on the electromagnetic form factor of charged pions at spacelike momenta
The experimental data on the electromagnetic form factor of charged pions
available at spacelike momenta are analyzed using the Dispersive Matrix (DM)
approach, which describes the momentum dependence of hadronic form factors
without introducing any explicit parameterization and includes properly the
constraints coming from unitarity and analyticity. The unitary bound is
evaluated nonperturbatively making use of the results of lattice QCD
simulations of suitable two-point correlation functions contributing to the HVP
term of the muon. Thanks to the DM method we determine the pion charge radius
from existing spacelike data in a completely model-independent way and
consistently with the unitary bound, obtaining fm. This finding differs by standard deviations from the
latest PDG value fm, which is dominated by
the very precise results of dispersive analyses of timelike data coming from
measurements of the cross section of the process. We
have analyzed the spacelike data using also traditional -expansions, like
the Boyd-Grinstein-Lebed (BGL) or Bourrely-Caprini-Lellouch (BCL) fitting
functions and adopting a simple procedure that incorporates ab initio the
non-perturbative unitary bound in the fitting process. We get fm and fm in nice
agreement with the DM result. We have addressed also the issue of the onset of
perturbative QCD by performing a sensitivity study of the pion form factor at
large spacelike momenta, based only on experimental spacelike data and
unitarity. Hence, although the leading pQCD behaviour is found to set in only
at very large momenta, our DM bands may provide information about the
pre-asymptotic effects related to the scale dependence of the pion distribution
amplitude.Comment: 39 pages, 21 figures, 4 table
Angular momentum exchange between coherent light and matter fields
Full, three dimensional, time-dependent simulations are presented
demonstrating the quantized transfer of angular momentum to a Bose-Einstein
condensate from a laser carrying orbital angular momentum in a
Laguerre-Gaussian mode. The process is described in terms of coherent Bragg
scattering of atoms from a chiral optical lattice. The transfer efficiency and
the angular momentum content of the output coupled vortex state are analyzed
and compared with a recent experiment.Comment: 4 pages, 4 figure
Targeting Drp1 and mitochondrial fission for therapeutic immune modulation
Mitochondria are dynamic organelles whose processes of fusion and fission are tightly regulated by specialized proteins, known as mitochondria-shaping proteins. Among them, Drp1 is the main pro-fission protein and its activity is tightly regulated to ensure a strict control over mitochondria shape according to the cell needs. In the recent years, mitochondrial dynamics emerged as a new player in the regulation of fundamental processes during T cell life. Indeed, the morphology of mitochondria directly regulates T cell differentiation, this by affecting the engagment of alternative metabolic routes upon activation. Further, Drp1-dependent mitochondrial fission sustains both T cell clonal expansion and T cell migration and invasivness. By this review, we aim at discussing the most recent findings about the roles played by the Drp1-dependent mitochondrial fission in T cells, and at highlighting how its pharmacological modulation could open the way to future therapeutic approaches to modulate T cell response
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