63 research outputs found
The Electric Dipole Form Factor of the Nucleon in Chiral Perturbation Theory to Sub-leading Order
The electric dipole form factor (EDFF) of the nucleon stemming from the QCD
theta term and from the quark color-electric dipole moments is calculated in
chiral perturbation theory to sub-leading order. This is the lowest order in
which the isoscalar EDFF receives a calculable, non-analytic contribution from
the pion cloud. In the case of the theta term, the expected lower bound on the
deuteron electric dipole moment is |d_d| > 1.4 10^(-4) \theta e fm. The
momentum dependence of the isovector EDFF is proportional to a non-derivative
time-reversal-violating pion-nucleon coupling, and the scale for momentum
variation ---appearing, in particular, in the radius of the form factor--- is
the pion mass.Comment: 14 pages, 3 figure
Differentiation of binding sites on reconstituted hepatic scavenger receptors using oxidized low-density lipoprotein
The Nucleon Electric Dipole Form Factor From Dimension-Six Time-Reversal Violation
We calculate the electric dipole form factor of the nucleon that arises as a
low-energy manifestation of time-reversal violation in quark-gluon interactions
of effective dimension 6: the quark electric and chromoelectric dipole moments,
and the gluon chromoelectric dipole moment. We use the framework of two-flavor
chiral perturbation theory to one loop
The Effective Chiral Lagrangian From the Theta Term
We construct the effective chiral Lagrangian involving hadronic and
electromagnetic interactions originating from the QCD theta term. We impose
vacuum alignment at both quark and hadronic levels, including field
redefinitions to eliminate pion tadpoles. We show that leading
time-reversal-violating (TV) hadronic interactions are related to
isospin-violating interactions that can in principle be determined from
charge-symmetry-breaking experiments. We discuss the complications that arise
from TV electromagnetic interactions. Some implications of the expected sizes
of various pion-nucleon TV interactions are presented, and the pion-nucleon
form factor is used as an example.Comment: 57 page
Non-perturbative Test of the Witten-Veneziano Formula from Lattice QCD
We compute both sides of the Witten-Veneziano formula using lattice
techniques. For the one side we perform dedicated quenched simulations and use
the spectral projector method to determine the topological susceptibility in
the pure Yang-Mills theory. The other side we determine in lattice QCD with
dynamical Wilson twisted mass fermions including for the first time
also the flavour singlet decay constant. The Witten-Veneziano formula
represents a leading order expression in the framework of chiral perturbation
theory and we also employ leading order chiral perturbation theory to relate
the flavor singlet decay constant to the relevant decay constant parameters in
the quark flavor basis and flavor non-singlet decay constants. After taking the
continuum and the SU chiral limits we compare both sides and find good
agreement within uncertainties.Comment: 30 pages, 7 figures, version accepted for publicatio
The Time-Reversal- and Parity-Violating Nuclear Potential in Chiral Effective Theory
We derive the parity- and time-reversal-violating nuclear interactions
stemming from the QCD theta term and quark/gluon operators of effective
dimension 6: quark electric dipole moments, quark and gluon chromo-electric
dipole moments, and two four-quark operators. We work in the framework of
two-flavor chiral perturbation theory, where a systematic expansion is
possible. The different chiral-transformation properties of the sources of
time-reversal violation lead to different hadronic interactions. For all
sources considered the leading-order potential involves known one-pion
exchange, but its specific form and the relative importance of short-range
interactions depend on the source. For the theta term, the leading potential is
solely given by one-pion exchange, which does not contribute to the deuteron
electric dipole moment. In subleading order, a new two-pion-exchange potential
is obtained. Its short-range component is indistinguishable from one of two
undetermined contact interactions that appear at the same order and represent
effects of heavier mesons and other short-range QCD dynamics. One-pion-exchange
corrections at this order are discussed as well.Comment: 39 pages, 8 figure
Up, down, strange and charm quark masses with N-f=2+1+1 twisted mass lattice QCD
We present a lattice QCD calculation of the up, down, strange and charm quark masses performed using the gauge configurations produced by the European Twisted Mass Collaboration with N-f = 2 + 1 + 1 dynamical quarks, which include in the sea, besides two light mass degenerate quarks, also the strange and charm quarks with masses close to their physical values. The simulations are based on a unitary setup for the two light quarks and on a mixed action approach for the strange and charm quarks. The analysis uses data at three values of the lattice spacing and pion masses in the range 210-450 MeV, allowing for accurate continuum limit and controlled chiral extrapolation. The quark mass renormalization is carried out non-perturbatively using the RI'-MOM method. The results for the quark masses converted to the (MS) over bar scheme are: m(ud) (2 GeV) = 3.70(17) MeV, m(s)(2 GeV) = 99.6(4.3) MeV and m(c)(m(c)) = 1.348(46) GeV. We obtain also the quark mass ratios m(s)/m(ud) = 26.66(32) and m(c)/m(s) = 11.62(16). By studying the mass splitting between the neutral and charged kaons and using available lattice results for the electromagnetic contributions, we evaluate m(u)/m(d) = 0.470(56), leading to m(u) = 2.36(24) MeV and m(d) = 5.03(26) MeV
Parity- and Time-Reversal-Violating Moments of Light Nuclei
I present the calculation of parity- and time-reversal-violating moments of
the nucleon and light nuclei, originating from the QCD theta term and effective
dimension-six operators. By applying chiral effective field theory these
calculations are performed in a unified framework. I argue that measurements of
a few light-nuclear electric dipole moments would shed light on the mechanism
of parity and time-reversal violation.Comment: 8 pages, contribution to the proceedings of the 5th International
Symposium on Symmetries in Subatomic Physics (SSP2012), June 18-22, 2012,
Groningen, The Netherland
Probing exotic phenomena at the interface of nuclear and particle physics with the electric dipole moments of diamagnetic atoms: A unique window to hadronic and semi-leptonic CP violation
The current status of electric dipole moments of diamagnetic atoms which
involves the synergy between atomic experiments and three different theoretical
areas -- particle, nuclear and atomic is reviewed. Various models of particle
physics that predict CP violation, which is necessary for the existence of such
electric dipole moments, are presented. These include the standard model of
particle physics and various extensions of it. Effective hadron level combined
charge conjugation (C) and parity (P) symmetry violating interactions are
derived taking into consideration different ways in which a nucleon interacts
with other nucleons as well as with electrons. Nuclear structure calculations
of the CP-odd nuclear Schiff moment are discussed using the shell model and
other theoretical approaches. Results of the calculations of atomic electric
dipole moments due to the interaction of the nuclear Schiff moment with the
electrons and the P and time-reversal (T) symmetry violating
tensor-pseudotensor electron-nucleus are elucidated using different
relativistic many-body theories. The principles of the measurement of the
electric dipole moments of diamagnetic atoms are outlined. Upper limits for the
nuclear Schiff moment and tensor-pseudotensor coupling constant are obtained
combining the results of atomic experiments and relativistic many-body
theories. The coefficients for the different sources of CP violation have been
estimated at the elementary particle level for all the diamagnetic atoms of
current experimental interest and their implications for physics beyond the
standard model is discussed. Possible improvements of the current results of
the measurements as well as quantum chromodynamics, nuclear and atomic
calculations are suggested.Comment: 46 pages, 19 tables and 16 figures. A review article accepted for
EPJ
The upgrade of the ALICE TPC with GEMs and continuous readout
The upgrade of the ALICE TPC will allow the experiment to cope with the high interaction rates foreseen for the forthcoming Run 3 and Run 4 at the CERN LHC. In this article, we describe the design of new readout chambers and front-end electronics, which are driven by the goals of the experiment. Gas Electron Multiplier (GEM) detectors arranged in stacks containing four GEMs each, and continuous readout electronics based on the SAMPA chip, an ALICE development, are replacing the previous elements. The construction of these new elements, together with their associated quality control procedures, is explained in detail. Finally, the readout chamber and front-end electronics cards replacement, together with the commissioning of the detector prior to installation in the experimental cavern, are presented. After a nine-year period of R&D, construction, and assembly, the upgrade of the TPC was completed in 2020.publishedVersio
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