Excited decuplet baryons from QCD sum rules

A calculation of the mass spectrum in the baryon decuplet sector is presented using the method of QCD sum rules. Sum rules are derived for states of spin-parity 3/2+- and 1/2+ using both the conventional method and a parity-projection method. The predictive ability of the sum rules is explored by a Monte-Carlo based analysis procedure in which the three phenomenological parameters (mass, coupling, threshold) are treated as free parameters and fitted simultaneously. Taken together, the results give an improved determination of the mass spectrum in this sector from the perspective of non-perturbative QCD.Comment: 9 pages, 3 figures, 3 table

Magnetic moment of hyperons in nuclear matter by using quark-meson coupling models

We calculate the magnetic moments of hyperons in dense nuclear matter by using relativistic quark models. Hyperons are treated as MIT bags, and the interactions are considered to be mediated by the exchange of scalar and vector mesons which are approximated as mean fields. Model dependence is investigated by using the quark-meson coupling model and the modified quark-meson coupling model; in the former the bag constant is independent of density and in the latter it depends on density. Both models give us the magnitudes of the magnetic moments increasing with density for most octet baryons. But there is a considerable model dependence in the values of the magnetic moments in dense medium. The magnetic moments at the nuclear saturation density calculated by the quark meson coupling model are only a few percents larger than those in free space, but the magnetic moments from the modified quark meson coupling model increase more than 10% for most hyperons. The correlations between the bag radius of hyperons and the magnetic moments of hyperons in dense matter are discussed.Comment: substantial changes in the text, submitted to PL

Gluonic charmonium resonances at BaBar and Belle?

We confront predictions for hybrid charmonium and other gluonic excitations in the charm region with recently observed structures in the mass range above 3 GeV. The Y(4260), if resonant, is found to agree with expectations for hybrid charmonium. The possibility that other gluonic excitations may be influencing the data in this region is discussed.Comment: 13 pages, LaTe

Phase-shift analysis of low-energy π±p\pi^{\pm}p elastic-scattering data

Using electromagnetic corrections previously calculated by means of a potential model, we have made a phase-shift analysis of the $\pi^\pm p$ elastic-scattering data up to a pion laboratory kinetic energy of 100 MeV. The hadronic interaction was assumed to be isospin invariant. We found that it was possible to obtain self-consistent databases by removing very few measurements. A pion-nucleon model was fitted to the elastic-scattering database obtained after the removal of the outliers. The model-parameter values showed an impressive stability when the database was subjected to different criteria for the rejection of experiments. Our result for the pseudovector $\pi N N$ coupling constant (in the standard form) is $0.0733 \pm 0.0014$. The six hadronic phase shifts up to 100 MeV are given in tabulated form. We also give the values of the s-wave scattering lengths and the p-wave scattering volumes. Big differences in the s-wave part of the interaction were observed when comparing our hadronic phase shifts with those of the current GWU solution. We demonstrate that the hadronic phase shifts obtained from the analysis of the elastic-scattering data cannot reproduce the measurements of the $\pi^- p$ charge-exchange reaction, thus corroborating past evidence that the hadronic interaction violates isospin invariance. Assuming the validity of the result obtained within the framework of chiral perturbation theory, that the mass difference between the $u$- and the $d$-quark has only a very small effect on the isospin invariance of the purely hadronic interaction, the isospin-invariance violation revealed by the data must arise from the fact that we are dealing with a hadronic interaction which still contains residual effects of electromagnetic origin.Comment: 43 pages, 6 figure

New Physics in b --> s bar(s) s Decay

We perform a model-independent analysis of the data on branching ratios and CP asymmetries of $B\to\phi K$ and $B\to\eta^{(')} K^{(*)}$ modes. The present data is encouraging to look for indirect evidences of physics beyond the Standard Model. We investigate the parameter spaces for different possible Lorentz structures of the new physics four-Fermi interaction. It is shown that if one takes the data at $1\sigma$ confidence level, only one particular Lorentz structure is allowed. Possible consequences for the $B_s$ system are also discussed.Comment: 9 pages, 3 encapsulated figures, minor changes in the text, conclusions unchanged, a few references added, version to appear in PL

A posteriori inclusion of parton density functions in NLO QCD final-state calculations at hadron colliders: The APPLGRID Project

A method to facilitate the consistent inclusion of cross-section measurements based on complex final-states from HERA, TEVATRON and the LHC in proton parton density function (PDF) fits has been developed. This can be used to increase the sensitivity of LHC data to deviations from Standard Model predictions. The method stores perturbative coefficients of NLO QCD calculations of final-state observables measured in hadron colliders in look-up tables. This allows the posteriori inclusion of parton density functions (PDFs), and of the strong coupling, as well as the a posteriori variation of the renormalisation and factorisation scales in cross-section calculations. The main novelties in comparison to original work on the subject are the use of higher-order interpolation, which substantially improves the trade-off between accuracy and memory use, and a CPU and computer memory optimised way to construct and store the look-up table using modern software tools. It is demonstrated that a sufficient accuracy on the cross-section calculation can be achieved with reasonably small look-up table size by using the examples of jet production and electro-weak boson (Z, W) production in proton-proton collisions at a center-of-mass energy of 14 TeV at the LHC. The use of this technique in PDF fitting is demonstrated in a PDF-fit to HERA data and simulated LHC jet cross-sections as well as in a study of the jet cross-section uncertainties at various centre-of-mass energies

Naturally light right-handed neutrinos in a 3-3-1 Model

In this work we show that light right-handed neutrinos, with mass in the sub-eV scale, is a natural outcome in a 3-3-1 model. By considering effective dimension five operators, the model predicts three light right-handed neutrinos, weakly mixed with the left-handed ones. We show also that the model is able to explain the LSND experiment and still be in agreement with solar and atmospheric data for neutrino oscillation.Comment: About 5 pages, no-figure

Properties of Light Flavour Baryons in Hypercentral quark model

The light flavour baryons are studied within the quark model using the hyper central description of the three-body system. The confinement potential is assumed as hypercentral coulomb plus power potential ($hCPP_\nu$) with power index $\nu$. The masses and magnetic moments of light flavour baryons are computed for different power index, $\nu$ starting from 0.5 to 1.5. The predicted masses and magnetic moments are found to attain a saturated value with respect to variation in $\nu$ beyond the power index $\nu>$ 1.0. Further we computed transition magnetic moments and radiative decay width of light flavour baryons. The results are in good agreement with known experimental as well as other theoretical models.Comment: Accepted in Pramana J. of Physic

WMAP-Compliant Benchmark Surfaces for MSSM Higgs Bosons

We explore `benchmark surfaces' suitable for studying the phenomenology of Higgs bosons in the minimal supersymmetric extension of the Standard Model (MSSM), which are chosen so that the supersymmetric relic density is generally compatible with the range of cold dark matter density preferred by WMAP and other observations. These benchmark surfaces are specified assuming that gaugino masses m_{1/2}, soft trilinear supersymmetry-breaking parameters A_0 and the soft supersymmetry-breaking contributions m_0 to the squark and slepton masses are universal, but not those associated with the Higgs multiplets (the NUHM framework). The benchmark surfaces may be presented as M_A-tan_beta planes with fixed or systematically varying values of the other NUHM parameters, such as m_0, m_{1/2}, A_0 and the Higgs mixing parameter mu. We discuss the prospects for probing experimentally these benchmark surfaces at the Tevatron collider, the LHC, the ILC, in B physics and in direct dark-matter detection experiments. An Appendix documents developments in the FeynHiggs code that enable the user to explore for her/himself the WMAP-compliant benchmark surfaces.Comment: Minor corrections, references added. 43 pages, 10 figures. Version to appear in JHE

Search for the decay K+ to pi+ gamma gamma in the pi+ momentum region P>213 MeV/c

We have searched for the K+ to pi+ gamma gamma decay in the kinematic region with pi+ momentum close to the end point. No events were observed, and the 90% confidence-level upper limit on the partial branching ratio was obtained, B(K+ to pi+ gamma gamma, P>213 MeV/c) < 8.3 x 10-9 under the assumption of chiral perturbation theory including next-to-leading order ``unitarity'' corrections. The same data were used to determine an upper limit on the K+ to pi+ gamma branching ratio of 2.3 x 10-9 at the 90% confidence level.Comment: 15 pages, 3 figures; no change in the results, accepted for publication in Physics Letters