455 research outputs found
Occurrence of a chiral-like pair band and a six-nucleon noncollective oblate isomer in ÂčÂČâ°I
We report for the first time two distinctive features in the oddâodd nucleus 120 I: a pair of doublet bands and a high-spin isomer built on the Ïh11/2Îœh11/2 configuration. For producing the excited states of 120 I, a fusion-evaporation reaction 118 Sn( 6 Li, 4n) at E =lab48 MeV was employed. The beam was provided by the 14UD tandem accelerator of the Heavy Ion Accelerator Facility at the Australian National University. The observed doublet structure built on the positive-parity states is the first case and unique in isotopes with Z=53 . The emerging properties are indicative of the known chiral characteristics, leading to a doubling of states for the Ïh11/2Îœh11/2 configuration. In contrast, the high-spin isomer with a half-life of 49(2) ns at spin-parity JÏ=25+ can be explained in terms of a noncollective oblate structure with the full alignment of six valence nucleons outside the 114 Sn core: three protons (g7/2)1(d5/2)1(h11/2)1 and three neutrons (h11/2)3 . This is an outstanding case that reveals a pure single-particle structure consisting of equal numbers of valence protons and neutrons outside the semi-double shell closure of 114 Sn with Z=50 and N=64 .Dr. C. Yuan acknowledges the National
Natural Science Foundation of China (11775316
Pion light-cone wave function and pion distribution amplitude in the Nambu-Jona-Lasinio model
We compute the pion light-cone wave function and the pion quark distribution
amplitude in the Nambu-Jona-Lasinio model. We use the Pauli-Villars
regularization method and as a result the distribution amplitude satisfies
proper normalization and crossing properties. In the chiral limit we obtain the
simple results, namely phi_pi(x)=1 for the pion distribution amplitude, and
= -M / f_pi^2 for the second moment of the pion light-cone
wave function, where M is the constituent quark mass and f_pi is the pion decay
constant. After the QCD Gegenbauer evolution of the pion distribution amplitude
good end-point behavior is recovered, and a satisfactory agreement with the
analysis of the experimental data from CLEO is achieved. This allows us to
determine the momentum scale corresponding to our model calculation, which is
close to the value Q_0 = 313 MeV obtained earlier from the analogous analysis
of the pion parton distribution function. The value of is, after the
QCD evolution, around (400 MeV)^2. In addition, the model predicts a linear
integral relation between the pion distribution amplitude and the parton
distribution function of the pion, which holds at the leading-order QCD
evolution.Comment: mistake in Eq.(38) correcte
Elevated levels of BMP2 compensate for loss of TGF-beta on proteoglycan level in articular cartilage during experimental osteoarthritis
Spectral quark model and low-energy hadron phenomenology
We propose a spectral quark model which can be applied to low energy hadronic
physics. The approach is based on a generalization of the Lehmann
representation of the quark propagator. We work at the one-quark-loop level.
Electromagnetic and chiral invariance are ensured with help of the gauge
technique which provides particular solutions to the Ward-Takahashi identities.
General conditions on the quark spectral function follow from natural physical
requirements. In particular, the function is normalized, its all positive
moments must vanish, while the physical observables depend on negative moments
and the so-called log-moments. As a consequence, the model is made finite,
dispersion relations hold, chiral anomalies are preserved, and the twist
expansion is free from logarithmic scaling violations, as requested of a
low-energy model. We study a variety of processes and show that the framework
is very simple and practical. Finally, incorporating the idea of vector-meson
dominance, we present an explicit construction of the quark spectral function
which satisfies all the requirements. The corresponding momentum representation
of the resulting quark propagator exhibits only cuts on the physical axis, with
no poles present anywhere in the complex momentum space. The momentum-dependent
quark mass compares very well to recent lattice calculations. A large number of
predictions and relations can be deduced from our approach for such quantities
as the pion light-cone wave function, non-local quark condensate, pion
transition form factor, pion valence parton distribution function, etc.Comment: revtex, 24 pages, 3 figure
Spherical and deformed isomers in Pb-188
Several isomers in Pb-188 have been identified using pulsed beams, the recoil-shadow technique, and the Er-164(Si-28,4n) Pb-188 reaction. Two of the isomers feed the 10(+) state of the yrast sequence and are suggested to be the 11(-) and 12(+) states from oblate and spherical configurations, respectively. The 12(+) isomer is fed weakly by another isomer with a relatively long lifetime, but it has not been characterized. A fourth isomer with a lifetime of about 1.2 mu s leads via a complicated path to the 8(+) and lower spin yrast states. It is a candidate for the K-pi = 8(-), two-quasineutron state which occurs systematically in N = 106 prolate-deformed nuclei, supporting the assumption that the intruding collective well is prolate
Atom-optics hologram in the time domain
The temporal evolution of an atomic wave packet interacting with object and
reference electromagnetic waves is investigated beyond the weak perturbation of
the initial state. It is shown that the diffraction of an ultracold atomic beam
by the inhomogeneous laser field can be interpreted as if the beam passes
through a three-dimensional hologram, whose thickness is proportional to the
interaction time. It is found that the diffraction efficiency of such a
hologram may reach 100% and is determined by the duration of laser pulses. On
this basis a method for reconstruction of the object image with matter waves is
offered.Comment: RevTeX, 13 pages, 8 figures; minor grammatical change
Spherical and deformed structures in Pb189
Îł-ray spectroscopy of high-spin states of the neutron-deficient nucleus Pb189 has been conducted with the Gd158(Ar36,5n) and Er164(Si29,4n) reactions. With the first of these, detection of evaporation residues and mass gating were used to unambiguously assign a number of prompt Îł-ray transitions to Pb189. With the second reaction and a pulsed beam, an isomer with a mean life of 32 ÎŒs was found. Although inconclusive, the available evidence favors identification of the isomer with the 332+ state of the Îœ(i13/2)-3 configuration. The levels observed below the isomer can be identified with states involving three different structures: the neutron (i13/2)-3 multiplet in the spherical well; a prolate-deformed band involving mixed i13/2 neutron orbitals; and a state with the oblate Ï(2p-2h)0+Îœ(i13/ 2)-1 configuration. The evidence for structures associated with different shapes is supported by the observation of E0 components in some of the JÏâJÏ transitions linking them
Baryon number violation, baryogenesis and defects with extra dimensions
In generic models for grand unified theories(GUT), various types of baryon
number violating processes are expected when quarks and leptons propagate in
the background of GUT strings. On the other hand, in models with large extra
dimensions, the baryon number violation in the background of a string is not
trivial because it must depend on the mechanism of the proton stabilization. In
this paper we argue that cosmic strings in models with extra dimensions can
enhance the baryon number violation to a phenomenologically interesting level,
if the proton decay is suppressed by the mechanism of localized wavefunctions.
We also make some comments on baryogenesis mediated by cosmological defects. We
show at least two scenarios will be successful in this direction. One is the
scenario of leptogenesis where the required lepton number conversion is
mediated by cosmic strings, and the other is the baryogenesis from the decaying
cosmological domain wall. Both scenarios are new and have not been discussed in
the past.Comment: 20pages, latex2e, comments and references added, to appear in PR
Fungicide resistance management in Australian grain crops
Fungicide resistance is a serious and increasing problem in cropping systems worldwide. Fungicides are an important component of integrated disease management strategies for the protection of crops from the impacts of fungal diseases. However, as their use has increased, the effectiveness of some fungicides has been reduced by the development of fungicide resistant pathogen populations. Without intervention, more fungicides are likely to become ineffective
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
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