1,023 research outputs found
The CP-Conserving Direction
A symmetry transformation is well defined in the case of an invariant theory,
being the corresponding operator undetermined otherwise. However, we show that,
even with CP violation, it is possible to determine the CP transformation by
separating the Lagrangian of the Standard Model in a CP-conserving and a
CP-violating part, in a unique way, making use of the empirically known quark
mixing hierarchy. To order \lambda^3 for the Bd-system, the CP-conserving
direction matches one of the sides of the (bd) unitarity triangle. We use this
determination to calculate the rephasing invariant parameter \epsilon, which
measures CP-mixing in the B0-B0bar system.Comment: 12 pages, no figure. Version to appear in JHE
T and CPT in B-Factories
For the Bd meson system, CP, T and CPT indirect violation can be described
using two physical parameters, epsilon and delta. The traditional observables
based on flavour tag and used in the kaon system, are not helpful in the Bd
case, and new asymmetries have to be introduced. Here such alternative
observables, based on CP tag, are presented, together with the first estimation
on the sensitivity that current asymmetric B-factories can achieve on their
measurement.Comment: 7 pages, Talk given at the International Europhysics conference on
HEP, HEP2001, July 2001, Budapest (Hungary
The Capabilities of Monochromatic EC Neutrino Beams with the SPS Upgrade
The goal for future neutrino facilities is the determination of the U(e3)
mixing and CP violation in neutrino oscillations. This will require precision
experiments with a very intense neutrino source and energy control. With this
objective in mind, the creation of monochromatic neutrino beams from the
electron capture decay of boosted ions by the SPS of CERN has been proposed. We
discuss the capabilities of such a facility as a function of the energy of the
boost and the baseline for the detector. We conclude that the SPS upgrade to
1000 GeV is crucial to reach a better sensitivity to CP violation iff it is
accompanied by a longer baseline. We compare the physics potential for two
different configurations: I) and (maximum achievable
at present SPS) to Frejus; II) and (maximum
achievable at upgraded SPS) to Canfranc. The main conclusion is that, whereas
the gain in the determination of U(e3) is rather modest, setup II provides much
better sensitivity to CP violation.Comment: 4 pages, 5 figures, To appear in the proceedings of International
Europhysics Conference on High Energy Physics (EPS-HEP2007), Manchester,
England, 19-25 July 200
Perspectives in Neutrino Physics: Monochromatic Neutrino Beams
In the last few years spectacular results have been achieved with the
demonstration of non vanishing neutrino masses and flavour mixing. The ultimate
goal is the understanding of the origin of these properties from new physics.
In this road, the last unknown mixing must be determined. If it is
proved to be non-zero, the possibility is open for Charge Conjugation-Parity
(CP) violation in the lepton sector. This will require precision experiments
with a very intense neutrino source. Here a novel method to create a
monochromatic neutrino beam, an old dream for neutrino physics, is proposed
based on the recent discovery of nuclei that decay fast through electron
capture. Such nuclei will generate a monochromatic directional neutrino beam
when decaying at high energy in a storage ring with long straight sections. We
also show that the capacity of such a facility to discover new physics is
impressive, so that fine tuning of the boosted neutrino energy allows precision
measurements of the oscillation parameters even for a mixing as
small as 1 degree. We can thus open a window to the discovery of CP violation
in neutrino oscillations.Comment: 15 pages, 7 figures. Contribution to the proceedings of GUSTAVOFEST -
Symposium in Honour of Gustavo C. Branco: CP Violation and the Flavour
Puzzle, Lisbon, Portugal, 19-20 July 200
Physics Reach with a Monochromatic Neutrino Beam from Electron Capture
Neutrino oscillation experiments from different sources have demonstrated
non-vanishing neutrino masses and flavour mixings. The next experiments have to
address the determination of the connecting mixing U(e3) and the existence of
the CP violating phase. Whereas U(e3) measures the strength of the oscillation
probability in appearance experiments, the CP phase acts as a phase-shift in
the interference pattern. Here we propose to separate these two parameters by
energy dependence, using the novel idea of a monochromatic neutrino beam
facility based on the acceleration of ions that decay fast through electron
capture. Fine tuning of the boosted neutrino energy allows precision
measurements able to open a window for the discovery of CP violation, even for
a mixing as small as 1 degree.Comment: 4 pages, 1 figure. Talk given at the International Europhysics
Conference on High Energy Physics, HEP-EPS 2005, Lisbon, Portugal, July
21-27, 200
Visibility Fringe Reduction Due to Noise-Induced Effects: Microscopic Approach to Interference Experiments
Decoherence is the main process behind the quantum to classical transition.
It is a purely quantum mechanical effect by which the system looses its ability
to exhibit coherent behavior. The recent experimental observation of
diffraction and interference patterns for large molecules raises some
interesting questions. In this context, we identify possible agents of
decoherence to take into account when modeling these experiments and study
theirs visible (or not) effects on the interference pattern. Thereby, we
present an analysis of matter wave interferometry in the presence of a dynamic
quantum environment and study how much the visibility fringe is reduced and in
which timescale the decoherence effects destroy the interference of massive
objects. Finally, we apply our results to the experimental data reported on
fullerenes and cold neutrons.Comment: 14 pages, 5 figures. Version to appear in Mod. Phys.
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Nascent polypeptide chains exit the ribosome in the same relative position in both eucaryotes and procaryotes.
We located the polypeptide nascent chain as it leaves cytoplasmic ribosomes from the plant Lemna gibba by immune electron microscopy using antibodies against the small subunit of the enzyme ribulose-1,5-bisphosphate carboxylase. Similar studies with Escherichia coli ribosomes, using antibodies directed against the enzyme beta-galactosidase, show that the polypeptide nascent chain emerges in the same relative position in plants and bacteria. The eucaryotic ribosomal exit site is on the large subunit, approximately 75 A from the interface between subunits and nearly 160 A from the central protuberance, the presumed site for peptidyl transfer. This is the first functional site on both the eucaryotic and procaryotic ribosomes to be determined
T and CPT Symmetries in Entangled Neutral Meson Systems
Genuine tests of an asymmetry under T and/or CPT transformations imply the
interchange between in-states and out-states. I explain a methodology to
perform model-indepedent separate measurements of the three CP, T and CPT
symmetry violations for transitions involving the decay of the neutral meson
systems in B- and {\Phi}-factories. It makes use of the quantum-mechanical
entanglement only, for which the individual state of each neutral meson is not
defined before the decay of its orthogonal partner. The final proof of the
independence of the three asymmetries is that no other theoretical ingredient
is involved and that the event sample corresponding to each case is different
from the other two. The experimental analysis for the measurements of these
three asymmetries as function of the time interval {\Delta}t > 0 between the
first and second decays is discussed, as well as the significance of the
expected results. In particular, one may advance a first observation of true,
direct, evidence of Time-Reserval-Violation in B-factories by many standard
deviations from zero, without any reference to, and independent of,
CP-Violation. In some quantum gravity framework the CPT-transformation is
ill-defined, so there is a resulting loss of particle-antiparticle identity.
This mechanism induces a breaking of the EPR correlation in the entanglement
imposed by Bose statistics to the neutral meson system, the so-called
{\omega}-effect. I present results and prospects for the {\omega}-parameter in
the correlated neutral meson-antimeson states.Comment: Proc. DISCRETE 2010, Symposium on Prospects in the Physics of
Discrete Symmetries, December 2010, Rom
Endothelium-derived microparticles from chronically thromboembolic pulmonary hypertensive patients facilitate endothelial angiogenesis.
11 p.-4 fig.-1 tab.Background: Increased circulating levels of endoglin+ endothelial microparticles (EMPs) have been identified in several cardiovascular disorders, related to severity. Endoglin is an auxilary receptor for transforming growth factor β (TGF-β) important in the regulation of vascular structure.Results: We quantified the number of microparticles in plasma of six patients with chronic thromboembolic pulmonary hypertension (CTEPH) and age- and sex-matched pulmonary embolic (PE) and healthy controls and investigated the role of microparticle endoglin in the regulation of pulmonary endothelial function in vitro. Results show significantly increased levels of endoglin+ EMPs in CTEPH plasma, compared to healthy and disease controls. Co-culture of human pulmonary endothelial cells with CTEPH microparticles increased intracellular levels of endoglin and enhanced
TGF-β-induced angiogenesis and Smad1,5,8 phosphorylation in cells, without affecting BMPRII expression. In an in vitro model, we generated endothelium-derived MPs with enforced membrane localization of endoglin. Co-culture of these MPs with endothelial cells increased cellular endoglin content, improved cell survival and stimulated
angiogenesis in a manner similar to the effects induced by overexpressed protein.Conclusions: Increased generation of endoglin+ EMPs in CTEPH is likely to represent a protective mechanism supporting endothelial cell survival and angiogenesis, set to counteract the effects of vascular occlusion and endothelial damage.This research was supported by a project grant (PG 11/13/28765) from the British Heart Foundation and by grants from Ministerio de Economia y Competitividad of Spain (SAF2013-43421-R to CB)Peer reviewe
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