10,873 research outputs found
Mass formula for T=0 and T=1 ground states of N=Z nuclei
An algebraic model is developed to calculate the T=0 and T=1 ground state
binding energies for N=Z nuclei. The method is tested in the sd shell and is
then extended to 28-50 shell which is currently the object of many experimental
studies.Comment: 5 figure
Sum rule for a difference of proton and neutron total photoproduction cross-sections
Starting from very high energy inelastic electron-nucleon scattering with a
production of a hadronic state to be moved closely to the direction of the
initial nucleon, then utilizing analytic properties of parts of forward virtual
Compton scattering amplitudes on proton and neutron, one obtains the relation
between nucleon form factors and a difference of proton and neutron
differential electroproduction cross-sections. In particular, for the case of
small transferred momenta, one finally derives sum rule, relating Dirac proton
mean square radius and anomalous magnetic moments of proton and neutron to the
integral over a difference of the total proton and neutron photoproduction
cross-sections.Comment: LaTeX2e, 7 pages, 1 eps figure (revised version
Conditional and constitutive expression of a Tbx1-GFP fusion protein in mice.
BACKGROUND: Velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS) is caused by a 1.5-3 Mb microdeletion of chromosome 22q11.2, frequently referred to as 22q11.2 deletion syndrome (22q11DS). This region includes TBX1, a T-box transcription factor gene that contributes to the etiology of 22q11DS. The requirement for TBX1 in mammalian development is dosage-sensitive, such that loss-of-function (LOF) and gain-of-function (GOF) of TBX1 in both mice and humans results in disease relevant congenital malformations. RESULTS: To further gain insight into the role of Tbx1 in development, we have targeted the Rosa26 locus to generate a new GOF mouse model in which a Tbx1-GFP fusion protein is expressed conditionally using the Cre/LoxP system. Tbx1-GFP expression is driven by the endogenous Rosa26 promoter resulting in ectopic and persistent expression. Tbx1 is pivotal for proper ear and heart development; ectopic activation of Tbx1-GFP in the otic vesicle by Pax2-Cre and Foxg1-Cre represses neurogenesis and produces morphological defects of the inner ear. Overexpression of a single copy of Tbx1-GFP using Tbx1Cre/+ was viable, while overexpression of both copies resulted in neonatal lethality with cardiac outflow tract defects. We have partially rescued inner ear and heart anomalies in Tbx1Cre/- null embryos by expression of Tbx1-GFP. CONCLUSIONS: We have generated a new mouse model to conditionally overexpress a GFP-tagged Tbx1 protein in vivo. This provides a useful tool to investigate in vivo direct downstream targets and protein binding partners of Tbx1
Pressure induced magnetic phase separation in LaCaMnO manganite
The pressure dependence of the Curie temperature T in
LaCaMnO was determined by neutron diffraction up to 8
GPa, and compared with the metallization temperature T \cite{irprl}.
The behavior of the two temperatures appears similar over the whole pressure
range suggesting a key role of magnetic double exchange also in the pressure
regime where the superexchange interaction is dominant. Coexistence of
antiferromagnetic and ferromagnetic peaks at high pressure and low temperature
indicates a phase separated regime which is well reproduced with a dynamical
mean-field calculation for a simplified model. A new P-T phase diagram has been
proposed on the basis of the whole set of experimental data.Comment: 5 pages, 4 figure
Odd Parity Light Baryon Resonances
We use a consistent SU(6) extension of the meson-baryon chiral Lagrangian
within a coupled channel unitary approach in order to calculate the T-matrix
for meson-baryon scattering in s-wave. The building blocks of the scheme are
the pion and nucleon octets, the rho nonet and the Delta decuplet. We identify
poles in this unitary T-matrix and interpret them as resonances. We study here
the non exotic sectors with strangeness S=0,-1,-2,-3 and spin J=1/2, 3/2 and
5/2. Many of the poles generated can be associated with known N, Delta, Sigma,
Lambda and Xi resonances with negative parity. We show that most of the
low-lying three and four star odd parity baryon resonances with spin 1/2 and
3/2 can be related to multiplets of the spin-flavor symmetry group SU(6). This
study allows us to predict the spin-parity of the Xi(1620), Xi(1690), Xi(1950),
Xi(2250), Omega(2250) and Omega(2380) resonances, which have not been
determined experimentally yet.Comment: New appendix and references adde
Mixing of pseudoscalar-baryon and vector-baryon in the J(P)=1/2(-) sector and the N* (1535) and N* (1650) resonances
We study the meson-baryon interaction with J(P) = 1/2 using the hidden-gauge Lagrangians and mixing pseudoscalar meson-baryon with the vector meson-baryon states in a coupled channels scheme with pi N, eta N, K Lambda, K Sigma, rho N, and pi Delta (d wave). We fit the subtraction constants of each channel to the S-11 partial wave amplitude of the pi N scattering data extracted from the partial wave analysis of the George Washington group. We find two poles that we associate to the N*(1535) and the N*(1650) resonances, with negative subtraction constants of natural size, and compare the results with empirical determinations of these pole positions. We calculate the branching ratios for the different channels of each resonance and we find a good agreement with the experimental data. The cross section for the pi(-)p -> eta n scattering is also evaluated and compared with experiment
Two Detector Reactor Neutrino Oscillation Experiment Kr2Det at Krasnoyarsk. Status Report
We consider status of the Kr2Det project aimed at sensitive searches for
neutrino oscillations in the atmospheric neutrino mass parameter region around
Dm2 ~ 3x10-3 eV2and at obtaining new information on the electron neutrino mass
structure (Ue3).Comment: 4 pages in pdf file. Talk presented at NANP-2001 International
Conference in Dubna, Russia, June 200
Dilepton production in nucleus-nucleus collisions at top SPS energy within the Parton-Hadron-String Dynamics (PHSD) transport approach
Dilepton production in In+In collisions at 158 AGeV is studied within the
microscopic parton-hadron-string dynamics (PHSD) transport approach that
incorporates explicit partonic degrees-of-freedom, dynamical hadronization as
well as the more familiar hadronic dynamics in the final reaction stages. A
comparison to the data of the NA60 Collaboration shows that the measured
dilepton yield is well described by including the collisional broadening of
vector mesons, while simultaneously accounting for the electromagnetic
radiation of the strongly coupled quark-gluon plasma (sQGP) via off-shell
quark-antiquark annihilation, quark annihilation with additional gluon
Bremsstrahlung and the gluon-Compton scattering mechanisms. In particular, the
spectra in the intermediate mass range (1 GeV < M < 2.5 GeV) are dominated by
quark-antiquark annihilation in the nonperturbative QGP. Also, the observed
softening of the transverse mass spectra at intermediate masses (1 GeV < M <
2.5 GeV) is approximately reproduced. Furthermore, for dileptons of low masses
(M < 0.6 GeV), we find a sizable contribution from the quark annihilation with
additional gluon bremsstrahlung, thus providing another possible window for
probing the properties of the sQGP.Comment: 16 pages, 14 figure
The role of the N*(1535) resonance and the pi^- p --> KY amplitudes in the OZI forbidden pi N --> phi N reaction
We study the pi N --> phi N reaction close to the phi N threshold within the
chiral unitary approach, by combining the pi^- p --> K^+ Sigma^-, pi^- p -->
K^0 Sigma^0 and pi^- p --> K^0 Lambda amplitudes with the coupling of the phi
to the K components of the final states of these reactions via quantum loops.
We obtain a good agreement with experiment when the dominant pi^- p --> K^0
Lambda amplitude is constrained with its experimental cross section. We also
evaluate the coupling of the N*(1535) to phi N and find a moderate coupling as
a consequence of partial cancellation of the large KY components of the
N*(1535). We also show that the N*(1535) pole approximation is too small to
reproduce the measured cross section for the pi N --> phi N reaction.Comment: 10 pages, 6 figure
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