Search results for "MBD"
showing 10 items of 646 documents
SU(3) Chiral approach to meson and baryon dynamics
1999
We report on recent progress on the chiral unitary approach, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV and meson baryon interaction up to the first baryonic resonances. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented, concretely the K^- p\to\Lambda(1405)\gamma reaction and the N^\ast (1535)N^\ast(1535)\pi and \eta couplings.
Isospin 0 and 1 resonances fromπΣphotoproduction data
2013
Recently we presented a successful strategy to extract the position of the two $\ensuremath{\Lambda}(1405)$ poles from experimental photoproduction data on the $\ensuremath{\gamma}p\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{0}{\ensuremath{\Sigma}}^{0}$ reaction at Jefferson Lab. Following a similar strategy, we extend the previous method to incorporate also the isospin 1 component which allows us to consider in addition the experimental data on $\ensuremath{\gamma}p\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\Sigma}}^{\ensuremath{\mp}}$. The idea is based on considering a production mechanism as model independent as possible and imple…
Measuring the cosmological background of relativistic with the Wilkinson Microwave Anisotropy Probe
2003
We show that the first year results of the Wilkinson Microwave Anisotropy Probe (WMAP) constrain very efficiently the energy density in relativistic particles in the Universe. We derive new bounds on additional relativistic degrees of freedom expressed in terms of an excess in the effective number of light neutrinos $\ensuremath{\Delta}{N}_{\mathrm{eff}}.$ Within the flat \ensuremath{\Lambda}CDM scenario, the allowed range is $\ensuremath{\Delta}{N}_{\mathrm{eff}}l6$ (95% confidence level) using WMAP data only, or $\ensuremath{-}2.6l\ensuremath{\Delta}{N}_{\mathrm{eff}}l4$ with the prior ${H}_{0}=72\ifmmode\pm\else\textpm\fi{}8\mathrm{km}{\mathrm{s}}^{\ensuremath{-}1}{\mathrm{Mpc}}^{\ensure…
Dark Radiation in extended cosmological scenarios
2012
Recent cosmological data have provided evidence for a "dark" relativistic background at high statistical significance. Parameterized in terms of the number of relativistic degrees of freedom Neff, however, the current data seems to indicate a higher value than the one expected in the standard scenario based on three active neutrinos. This dark radiation component can be characterized not only by its abundance but also by its clustering properties, as its effective sound speed and its viscosity parameter. It is therefore crucial to study the correlations among the dark radiation properties and key cosmological parameters, as the dark energy equation of state or the running of the scalar spec…
Search for anomalous quarticWWγγcouplings in dielectron and missing energy final states inpp¯collisions ats=1.96 TeV
2013
We present a search for anomalous components of the quartic gauge boson coupling WW gamma gamma in events with an electron, a positron and missing transverse energy. The analyzed data correspond to 9.7 fb(-1) of integrated luminosity collected by the D0 detector in p (p) over bar collisions at root s 1.96 TeV. The presence of anomalous quartic gauge couplings would manifest itself as an excess of boosted WW events. No such excess is found in the data, and we set the most stringent limits to date on the anomalous coupling parameters a(0)(W) and a(C)(W). When a form factor with Lambda(cutoff) = 0.5 TeV is used, the observed upper limits at 95% C. L. are vertical bar a(0)(W)/Lambda(2)vertical …
ScalarΛNandΛΛinteraction in a chiral unitary approach
2006
We study the central part of the {lambda}N and {lambda}{lambda} potential by considering the correlated and uncorrelated two-meson exchange in addition to the {omega} exchange contribution. The correlated two-meson exchange is evaluated within a chiral unitary approach. We find that a short-range repulsion is generated by the correlated two-meson potential, which also produces an attraction in the intermediate-distance region. The uncorrelated two-meson exchange produces a sizable attraction in all cases that is counterbalanced by the {omega} exchange contribution.
Role of theΔ*(1940)in theπ+p→K+Σ+(1385)andpp→nK+Σ+(1385)reactions
2014
The pp -> nK(+)Sigma(+)(1385) reaction is a very good isospin 3/2 filter for studying Delta(++)* resonance decaying to K+Sigma(+)(1385). Within the effective Lagrangian method, we investigate the Sigma (1385) (spin parity J(P) = 3/2(+)) hadronic production in the pi(+) p -> K+Sigma(+)(1385) and pp -> nK(+)Sigma(+)(1385) reactions. For the pi(+) p -> K+Sigma(+)(1385) reaction, in addition to the "background" contributions from t-channel K*(0) exchange and u-channel Lambda(1115) and Sigma(0)(1193) exchange, we also consider the contribution from the s-channel Delta*(1940) resonance, which has significant coupling to the K Sigma(1385) channel. We show that the inclusion of the Delta*(1940) res…
Ks0andΛproduction inppinteractions ats=0.9and 7 TeV measured with the ATLAS detector at the LHC
2012
The production of K(S)(0) and Lambda hadrons is studied in pp collision data at root s = 0.9 and 7 TeV collected with the ATLAS detector at the LHC using a minimum-bias trigger. The observed distributions of transverse momentum, rapidity, and multiplicity are corrected to hadron level in a model-independent way within well-defined phase-space regions. The distribution of the production ratio of (Lambda) over bar to Lambda baryons is also measured. The results are compared with various Monte Carlo simulation models. Although most of these models agree with data to within 15% in the K(S)(0) distributions, substantial disagreements are found in the Lambda distributions of transverse momentum.
Measurements of the Λb0→J/ψΛ decay amplitudes and the Λb0 polarisation in pp collisions at s=7 TeV
2013
An angular analysis of Λ0b→J/ψΛ decays is performed using a data sample corresponding to 1.0 fb−1 collected in pp collisions at √s=7 TeV with the LHCb detector at the LHC. A parity violating asymmetry parameter characterising the Λ0b→J/ψΛ decay of 0.05±0.17±0.07 and a Λ0b transverse production polarisation of 0.06±0.07±0.02 are measured, where the first uncertainty is statistical and the second systematic.
Search for doubly charmed baryonsΞcc+andΞcc++inBABAR
2006
We search for the production of doubly charmed baryons in e(+)e(-) annihilations at or near a center-of-mass energy of 10.58 GeV, in a data sample with an integrated luminosity of 232 fb(-1) recorded with the BABAR detector at the PEP-II storage ring at the Stanford Linear Accelerator Center. We search for Xi(+)(cc) baryons in the final states Lambda K-+(c)-pi(+) and Xi(0)(c)pi(+), and Xi(++)(cc) baryons in the final states Lambda K-+(c)-pi(+)pi(+) and Xi(0)(c)pi(+)pi(+). We find no evidence for the production of doubly charmed baryons.