3,467 research outputs found
Proton recoil polarization in exclusive (e,e'pp) reactions
The general formalism of nucleon recoil polarization in the () reaction is given. Numerical predictions are presented for the
components of the outgoing proton polarization and of the polarization transfer
coefficient in the specific case of the exclusive O()C knockout reaction leading to discrete states in the residual
nucleus. Reaction calculations are performed in a direct knockout framework
where final-state interactions and one-body and two-body currents are included.
The two-nucleon overlap integrals are obtained from a calculation of the
two-proton spectral function of O where long-range and short-range
correlations are consistently included. The comparison of results obtained in
different kinematics confirms that resolution of different final states in the
O()C reaction may act as a filter to
disentangle and separately investigate the reaction processes due to
short-range correlations and two-body currents and indicates that measurements
of the components of the outgoing proton polarization may offer good
opportunities to study short-range correlations.Comment: 12 pages, 6 figure
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
Short-range and tensor correlations in the O(e,epn) reaction
The cross sections for electron induced two-nucleon knockout reactions are
evaluated for the example of the O(e,epn)N reaction leading to
discrete states in the residual nucleus N. These calculations account
for the effects of nucleon-nucleon correlations and include the contributions
of two-body meson exchange currents as the pion seagull, pion in flight and the
isobar current contribution. The effects of short-range as well as tensor
correlations are calculated within the framework of the coupled cluster method
employing the Argonne V14 potential as a model for a realistic nucleon-nucleon
interaction. The relative importance of correlation effects as compared to the
contribution of the meson exchange currents depends on the final state of the
residual nucleus. The cross section leading to specific states, like e.g. the
ground state of N, is rather sensitive to the details of the correlated
wave function.Comment: 16 pages, 9 figures include
A co-ultramicronized palmitoylethanolamide/luteolin composite mitigates clinical score and disease-relevant molecular markers in a mouse model of experimental autoimmune encephalomyelitis
Background: Persistent and/or recurrent inflammatory processes are the main factor leading to multiple sclerosis (MS) lesions. The composite ultramicronized palmitoylethanolamide, an endogenous N-acylethanolamine, combined with the flavonoid luteolin, PEALut, have been found to exert neuroprotective activities in experimental models of spinal and brain injury and Alzheimer disease, as well as a clinical improvement in human stroke patients. Furthermore, PEALut enhances the expression of different myelin proteins in oligodendrocyte progenitor cells suggesting that this composite might have protective effects in MS experimental models. Methods: The mouse model of experimental autoimmune encephalomyelitis (EAE) based on active immunization with a fragment of myelin oligodendrocyte glycoprotein (MOG35-55) was used. The daily assessment of clinical score and the expression of serum amyloid A (SAA1), proinflammatory cytokines TNF-\u3b1, IL-1\u3b2, IFN-\u3b3, and NLRP3 inflammasome, as well as TLR2, Fpr2, CD137, CD3-\u3b3, and TCR-\u3b6 chain, heterodimers that form T cell surface glycoprotein (TCR), and cannabinoid receptors CB1, CB2, and MBP, were evaluated in the brainstem and cerebellum at different postimmunization days (PIDs). Results: Vehicle-MOG35-55-immunized (MOG35-55) mice developed ascending paralysis which peaked several days later and persisted until the end of the experiment. PEALut, given intraperitoneally daily starting on day 11 post-immunization, dose-dependently improved clinical score over the range 0.1-5 mg/kg. The mRNA expression of SAA1, TNF-\u3b1, IL-1\u3b2, IFN-\u3b3, and NLRP3 were significantly increased in MOG35-55 mice at 14 PID. In MOG35-55 mice treated with 5 mg /kg PEALut, the increase of SAA1, TNF- \u3b1, IL-1\u3b2, and IFN-\u3b3transcripts at 14 PID was statistically downregulated as compared to vehicle-MOG35-55 mice (p < 0.05). The expression of TLR2, Fpr2, CD137, CD3-\u3b3, TCR-\u3b6 chain, and CB2 receptors showed a significant upregulation in vehicle-MOG35-55 mice at 14 PID. Instead, CB1 and MBP transcripts have not changed in expression at any time. In MOG/PEALut-treated mice, TLR2, Fpr2, CD137, CD3-\u3b3, TCR-\u3b6 chain, and CB2 mRNAs were significantly downregulated as compared to vehicle MOG35-55 mice. Conclusions: The present results demonstrate that the intraperitoneal administration of the composite PEALut significantly reduces the development of clinical signs in the MOG35-55 model of EAE. The dose-dependent improvement of clinical score induced by PEALut was associated with a reduction in transcript expression of the acute-phase protein SAA1, TNF-\u3b1, IL-1\u3b2, IFN-\u3b3, and NLRP3 proinflammatory proteins and TLR2, Fpr2, CD137, CD3-\u3b3, TCR-\u3b6 chain, and CB2 receptors
Quenched Hadron Spectrum and Decay Constants on the lattice
In this talk we present the results obtained from a study of
(quenched) lattice configurations from the APE collaboration, at
, using both the Wilson and the SW-Clover fermion action.
We determine the light hadronic spectrum and the meson decay constants. For the
light-light systems we find an agreement with the experimental data of for mesonic masses and for baryonic masses and pseudoscalar
decay constants; a larger deviation is present for the vector decay constants.
For the heavy-light decay constants we find , in good agreement with previous estimates.Comment: 8 pages, latex, Talk given at XXV ITEP Winter School of Physics,
Moscow - Russia, 18-27 Feb 199
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
The Chiral Condensate of Strongly Coupled QCD in the 't Hooft Limit
Using the recently proposed generalization to an arbitrary number of colors
of the strong coupling approach to lattice gauge
theories\cite{Grignani:2003uv}, we compute the chiral condensate of massless
QCD in the 't Hooft limit.Comment: 12 pages, revtex
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
Final State Interaction in Exclusive Reactions
Contributions of nucleon-nucleon (NN) correlations, meson exchange currents
and the residual final state interactions (FSI) on exclusive two-nucleon
knock-out reactions induced by electron scattering are investigated. All
contributions are derived from the same realistic meson exchange model for the
NN interaction. Effects of correlations and FSI are determined in a consistent
way by solving the NN scattering equation, the Bethe-Goldstone equation, for
two nucleons in nuclear matter. One finds that the FSI re-scattering terms are
non-negligible even if the two nucleons are emitted back to back.Comment: 8 pages, 5 figure
Light hadron spectroscopy on the lattice with the non-perturbatively improved Wilson action
We present results for the light meson masses and decay constants as obtained
from calculations with the non-perturbatively improved (`Alpha') action and
operators on a 24^3 \times 64 lattice at beta = 6.2, in the quenched
approximation. The analysis was performed in a way consistent with O(a)
improvement. We obtained: reasonable agreement with experiment for the
hyperfine splitting; f_K=156(17) MeV, f_pi =139(22) MeV, f_K/f_pi = 1.13(4) ;
f_{K*}=219(7) MeV, f_rho =199(15) MeV, f_phi =235(4) MeV; f_{K*}^{T}(2 GeV) =
178(10) MeV, f_rho^{T}(2 GeV) =165(11) MeV, where f_V^{T} is the coupling of
the tensor current to the vector mesons; the chiral condensate
^\bar{MS} (2 GeV)= - (253 +/- 25 MeV)^3. Our results are compared to
those obtained with the unimproved Wilson action. We also verified that the
free-boson lattice dispersion relation describes our results very accurately
for a large range of momenta.Comment: 29 pages (LaTeX), 14 Postscript figure
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