The permutation group S_N and large Nc excited baryons

We study the excited baryon states for an arbitrary number of colors Nc from the perspective of the permutation group S_N of N objects. Classifying the transformation properties of states and quark-quark interaction operators under S_N allows a general analysis of the spin-flavor structure of the mass operator of these states, in terms of a few unknown constants parameterizing the unknown spatial structure. We explain how to perform the matching calculation of a general two-body quark-quark interaction onto the operators of the 1/Nc expansion. The inclusion of core and excited quark operators is shown to be necessary. Considering the case of the negative parity L=1 states transforming in the MS of S_N, we discuss the matching of the one-gluon and the Goldstone-boson exchange interactions.Comment: 38 pages. Final version to be published in Physical Review

Pion Electroproduction Amplitude Relations in the 1/N_c Expansion

We derive expressions for pion electroproduction amplitudes in the 1/N_c expansion of QCD, and obtain from them linear relations between the electromagnetic multipole amplitudes that hold at all energies. The leading-order relations in 1/N_c compare favorably with available data (especially away from resonances), but the next-to-leading-order relations tend to provide only small or no improvement.Comment: 45 pages, pdflatex, contains multiple figures but .pdf file is < 4 MB. This version to appear in Phys. Rev. D, but has much better figure resolution. References greatly expanded, some additional discussio

Positive parity pentaquark towers in large Nc QCD

We construct the complete set of positive parity pentaquarks, which correspond in the quark model to {\bar s} q^{Nc+1} states with one unit of orbital angular momentum L=1. In the large Nc limit they fall into the K=1/2 and K=3/2 irreps (towers) of the contracted SU(4)c symmetry. We derive predictions for the mass spectrum and the axial couplings of these states at leading order in 1/Nc. The strong decay width of the lowest-lying positive parity exotic state is of order O(1/Nc), such that this state is narrow in the large Nc limit. Replacing the antiquark with a heavy antiquark {\bar Q} q^{Nc+1}, the two towers become degenerate, split only by O(1/mQ) hyperfine interactions. We obtain predictions for the strong decay widths of heavy pentaquarks to ordinary baryons and heavy H(*)_{\bar Q} mesons at leading order in 1/Nc and 1/mQ.Comment: 21 pages, 2 figures, 5 table

A vertical diatomic artificial molecule in the intermediate coupling regime in a parallel and perpendicular magnetic field

We present experimental results for the ground state electrochemical potentials of a few electron semiconductor artificial molecule made by vertically coupling two quantum dots, in the intermediate coupling regime, in perpendicular and parallel magnetic fields up to 5 T. We perform a quantitative analysis based on local-spin density functional theory. The agreement between theoretical and experimental results is good, and the phase transitions are well reproduced.Comment: Typeset using Revtex, 13 pages and 8 Postscript figure

Molecular phases in coupled quantum dots

We present excitation energy spectra of few-electron vertically coupled quantum dots for strong and intermediate inter-dot coupling. By applying a magnetic field, we induce ground state transitions and identify the corresponding quantum numbers by comparison with few-body calculations. In addition to atomic-like states, we find novel "molecular-like" phases. The isospin index characterizes the nature of the bond of the artificial molecule and this we control. Like spin in a single quantum dot, transitions in isospin leading to full polarization are observed with increasing magnetic field.Comment: PDF file only, 28 pages, 3 tables, 4 color figures, 2 appendices. To appear in Physical Review B, Scheduled 15 Feb 2004, Vol. 69, Issue

A mitochondrial half-size ABC transporter is involved in cadmium tolerance in Chlamydomonas reinhardtii

Five cadmium-sensitive insertional mutants, all affected at the CDS1 ('cadmium-sensitive 1') locus, have been previously isolated in the unicellular green alga Chlamydomonas reinhardtii. We here describe the cloning of the Cds1 gene (8314 bp with 26 introns) and the corresponding cDNA. The Cds1 gene, strongly induced by cadmium, encodes a putative protein (CrCds1) of 1062 amino acid residues that belongs to the ATM/HMT subfamily of half-size ABC transporters. This subfamily includes both vacuolar HMT-type proteins transporting phytochelatin-cadmium complexes from the cytoplasm to the vacuole and mitochondrial ATM-type proteins involved in the maturation of cytosolic Fe/S proteins. Unlike the Delta sphmt1 cadmium-sensitive mutant of Schizosaccharomyces pombe that lacks a vacuolar HMT-type transporter, the cds1 mutant accumulates a high amount of phytochelatin-cadmium complexes. By epitope tagging, the CrCds1 protein was localized in the mitochondria. Even though mitochondria of cds1 do not accumulate important amounts of 'free' iron, the mutant cells are hypersensitive to high iron concentrations. Our data show for the first time that a mitochondrial ATM-like transporter plays a major role in tolerance to cadmium.Peer reviewe

Baryon Tri-local Interpolating Fields

We systematically investigate tri-local (non-local) three-quark baryon fields with U_L(2)*U_R(2) chiral symmetry, according to their Lorentz and isospin (flavor) group representations. We note that they can also be called as "nucleon wave functions" due to this full non-locality. We study their chiral transformation properties and find all the possible chiral multiplets consisting J=1/2 and J=3/2 baryon fields. We find that the axial coupling constant |g_A| = 5/3 is only for nucleon fields belonging to the chiral representation (1/2,1)+(1,1/2) which contains both nucleon fields and Delta fields. Moreover, all the nucleon fields belonging to this representation have |g_A| = 5/3.Comment: 8 pages, 3 tables, accepted by EPJ

Centrality, rapidity, and transverse-momentum dependence of gluon shadowing and antishadowing on J/ψJ/\psi production in ddAu collisions at s\sqrt{s}=200 GeV

We have carried out a wide study of shadowing and antishadowing effects on \jpsi\ production in \dAu\ collisions at $\sqrt{s_{NN}}=200$ GeV. We have studied the effects of three different gluon nPDF sets, using the exact kinematics for a $2\to 2$ process, namely $g+g\to J/\psi+g$ as expected from LO pQCD. We have computed the rapidity dependence of \RCP\ and $R_{d\rm Au}$ for the different centrality classes of the PHENIX data. For mid rapidities, we have also computed the transverse-momentum dependence of the nuclear modification factor, which cannot be predicted with the usual $2\to 1$ simplified kinematics. All these observables have been compared to the PHENIX data in \dAu\ collisions.Comment: 10 pages, 11 figures, talk given by N. Matagne at the conference "thirty years of hadronic physics", Spa, Belgium, April 6-8, 2011, to appear in Few Body System

Evaluation of the reach and impact of the 100% Jeune youth social marketing program in Cameroon: findings from three cross-sectional surveys

BACKGROUND: The 100% Jeune youth social marketing program in Cameroon aims to address the high STI/HIV prevalence rates and the high levels of unwanted pregnancy. This study evaluates the 100% Jeune program, analyzing its reach and impact on condom use, level of sexual activity, and predictors of condom use. METHODS: This analysis uses data from three waves of the Cameroon Adolescent Reproductive Health Survey, implemented at 18-month intervals between 2000 and 2003. The sample is restricted to unmarried youth aged 15–24; sample sizes are 1,956 youth in 2000, 3,237 in 2002, and 3,370 in 2003. Logistic regression analyses determine trends in reproductive health behavior and their predictors, as well as estimate the effect of program exposure on these variables. All regression analyses control for differences in sample characteristics. RESULTS: A comparison of trends over the 36-month study period shows that substantial positive changes occurred among youth. Results of dose response analyses indicate that some of these positive changes in condom use and predictors of use can be attributed to the 100% Jeune youth social marketing program. The program contributed to substantial increases in condom use, including consistent use with regular partners among youth of both sexes. Among males, it also contributed to consistent use with casual partners. While condom use increased with both regular and casual partners, levels of use are higher with the latter. Observed secular trends indicate that factors besides the 100% Jeune program also contributed to the observed improvements. Despite efforts to promote abstinence, the 100% Jeune program had no effect on levels of sexual activity or number of sexual partners. Likewise, there is no evidence that reproductive health programs for youth lead to increased sexual activity. CONCLUSION: Results show that 100% Jeune successfully used a variety of mass media and interpersonal communication channels to reach a high proportion of youth throughout the intervention period. In a context in which a variety of governmental and nongovernmental partners are increasing youth-focused reproductive health programming, the 100% Jeune program reached a higher proportion of youth than did other programs. Collective efforts of multiple organizations over time can lead to improvements in adolescent reproductive health. Resources should be allocated to identify and understand predictors of abstinence and partner reduction to inform future programming decisions