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1.
P. C. Sood O. S. K. S. Sastri R. K. Jain 《The European Physical Journal A - Hadrons and Nuclei》2009,39(1):101-106
The role of the band quantum number K in influencing the character of allowed transitions in heavy deformed nuclei is examined. The conditions for the occurrence of K -forbidden decays in this region are explored. Specific cases of “allowed” decays proceeding via
K = 2 to
K = 6 channels are presented to illustrate the phenomenon. The listed
K = 2 transitions, which by themselves contribute over 10% of all the presently known allowed transitions for A
228 nuclei, are seen to have an average , which is clearly outside the normal range for allowed transitions. It is concluded that, wherever the -connected states can be confidently labelled using the quantum numbers, the K -forbiddenness is in general as significant as that involving the other two (spin and parity) quantum numbers. 相似文献
2.
A.?Sibirtsev J.?Haidenbauer F.?Huang S.?Krewald U.?-G.?Mei?ner 《The European Physical Journal A - Hadrons and Nuclei》2009,40(1):65-75
We present a systematic analysis of backward pion photoproduction for the reactions
p
p and
p
n . Regge phenomenology is applied at invariant collision energies above 3GeV in order to fix the reaction amplitude. A comparision
with older data on - and -photoproduction at = 180° indicates that the high-energy limit as given by the Regge calculation could be reached possibly at energies of around ≃ 3 GeV. In the energy region of
2.5 GeV, covered by the new measurements of
p
p differential cross-sections at large angles at ELSA, JLab, and LEPS, we see no clear signal for a convergence towards the
Regge results. The baryon trajectories obtained in our analysis are in good agreement with those given by the spectrum of
excited baryons. 相似文献
3.
S. Abd El-Samad R. Bilger K. -Th. Brinkmann H. Clement M. Dietrich E. Doroshkevich S. Dshemuchadse K. Ehrhardt A. Erhardt W. Eyrich A. Filippi H. Freiesleben M. Fritsch R. Geyer A. Gillitzer J. Hauffe D. Hesselbarth R. Jaekel B. Jakob L. Karsch K. Kilian J. Kress E. Kuhlmann S. Marcello S. Marwinski R. Meier K. M?ller H. P. Morsch L. Naumann J. Ritman E. Roderburg P. Sch?nmeier M. Schulte-Wissermann W. Schroeder F. Stinzing G. Y. Sun J. W?chter G. J. Wagner M. Wagner U. Weidlich A. Wilms S. Wirth G. Zhang P. Zupranski 《The European Physical Journal A - Hadrons and Nuclei》2009,39(3):281-289
The single-pion production reactions pp
d
, pp
np
and pp
pp
were measured at a beam momentum of 0.95GeV/c ( T
p
400 MeV) using the short version of the COSY-TOF spectrometer. The central calorimeter provided particle identification,
energy determination and neutron detection in addition to time-of-flight and angle measurements from other detector parts.
Thus all pion production channels were recorded with 1-4 overconstraints. The main emphasis is put on the presentation and
discussion of the np
channel, since the results on the other channels have already been published previously. The total and differential cross-sections
obtained are compared to theoretical calculations. In contrast to the pp
channel we observe in the np
channel a strong influence of the excitation. In particular, the pion angular distribution exhibits a (3 cos2
+ 1) -dependence, typical for a pure s -channel excitation and identical to that observed in the d
channel. Since the latter is understood by a s -channel resonance in the 1
D
2
pn partial wave, we discuss an analogous scenario for the pn
channel. 相似文献
4.
We calculate the one-photon loop radiative corrections to virtual pion Compton scattering
→
, that subprocess which determines in the one-photon exchange approximation the pion-nucleus bremsstrahlung reaction
Z →
Z
. Ultraviolet and infrared divergencies of the loop integrals are both treated by dimensional regularization. Analytical
expressions for the O() corrections to the virtual Compton scattering amplitudes, A(s, u, Q) and B(s, u, Q) , are derived with their full dependence on the (small) photon virtuality Q from 9 classes of contributing one-loop diagrams. Infrared finiteness of these virtual radiative corrections is achieved
(in the standard way) by including soft photon radiation below an energy cut-off . In the region of low
center-of-mass energies, where the pion-nucleus bremsstrahlung process is used to extract the pion electric and magnetic
polarizabilities, we find radiative corrections up to about -3% for = 5 MeV. Furthermore, we extend our calculation of the radiative corrections to virtual pion Compton scattering
→
by including the leading pion-structure effect in the form of the polarizability difference - . Our analytical results are particularly relevant for analyzing the data of the COMPASS experiment at CERN which aims at
measuring the pion electric and magnetic polarizabilities with high statistics using the Primakoff effect. 相似文献
5.
G. Meierhofer P. Kudejova L. Canella P. Grabmayr J. Jochum J. Jolie 《The European Physical Journal A - Hadrons and Nuclei》2009,40(1):61-64
The thermal neutron capture cross-sections of the 76Ge(n,)77Ge and the 76Ge(n,)77m
Ge reactions have been measured by activating targets of isotopically enriched GeO2 through cold neutrons. The -decay spectra after the -decay of 77Ge and 77m
Ge were measured with HPGe detectors. From these spectra the cross-sections for the 76Ge(n,) reactions were derived relative to the cross-section of 197Au using the absolute emission probabilities of the observed -ray energies. The methods used in this work result in smaller systematic uncertainties than those obtained in previous experiments. 相似文献
6.
V. M. Kolomietz A. I. Sanzhur 《The European Physical Journal A - Hadrons and Nuclei》2008,38(3):345-354
We apply the direct variational method to derive the equation of state for finite nuclei within the stability valley. The
extended Thomas-Fermi approximation for the energy functional with Skyrme forces is used. Applying the leptodermous expansion
for the profile nucleon densities, we have studied the neutron coat and the isospin symmetry energy for neutron-rich nuclei.
Using the equation of state for the pressure, we derive the region of spinodal instability of finite nuclei and its dependence
on the mass number, the asymmetry parameter and the Skyrme force parameters. We suggest the procedure of derivation of the
isospin symmetry energy from the analysis of the isospin shift of the chemical potential
= - beyond the beta-stability line. We show that both the structure of the neutron coat and the position of the drip line depend
significantly on the Skyrme force parameters. 相似文献
7.
We calculate the lowest-order cross-section for Dirac magnetic monopole production from photon fusion (
in p
collisions at = 1.96 TeV, pp collisions at = 14 TeV, and we compare
with Drell-Yan (DY) production. We find the total
cross-section is comparable with DY at = 1.96 TeV and dominates DY by a factor > 50 at = 14 TeV. We conclude that both the
and DY processes allow for a monopole mass limit m > 370 GeV based upon the null results of the recent monopole search at the Collider Detector at Fermilab (CDF). We also conclude
that
production is the leading mechanism to be considered for direct monopole searches at the Large Hadron Collider (LHC). 相似文献
8.
9.
A.?Sibirtsev J.?Haidenbauer S.?Krewald U.?-G.?Mei?ner A.?W.?Thomas 《The European Physical Journal A - Hadrons and Nuclei》2009,41(1):71-84
A Regge model with absorptive corrections is employed in a global analysis of the world data on the reactions
p
p and
n
n for photon energies from 3 to 18GeV. In this region resonance contributions are expected to be negligible so that the available
experimental information on differential cross-sections and single and double polarization observables at - t
2 GeV2allows us to determine the reaction amplitude reliably. The model amplitude is then used to predict observables for photon
energies below 3GeV. A detailed comparison with recent data from the CLAS and CB-ELSA Collaborations in that energy region
is presented. Furthermore, the prospects for determining the radiative decay width via the Primakoff effect from the reaction
p
p are explored. 相似文献
10.
Gauhar Abbas B. Ananthanarayan 《The European Physical Journal A - Hadrons and Nuclei》2009,41(1):7-11
We obtain stringent bounds in the 〈r
2
-c plane where these are the scalar radius and the curvature parameters of the scalar K
form factor, respectively, using analyticity and dispersion relation constraints, the knowledge of the form factor from the
well-known Callan-Treiman point , as well as at , which we call the second Callan-Treiman point. The central values of these parameters from a recent determination are accomodated
in the allowed region provided the higher loop corrections to the value of the form factor at the second Callan-Treiman point
reduce the one-loop result by about 3% with . Such a variation in magnitude at the second Callan-Treiman point yields 0.12 fm2
〈r
2
0.21 fm2and 0.56 GeV-4
c
1.47 GeV-4and a strong correlation between them. A smaller value of shifts both bounds to lower values. 相似文献
11.
M. V. Polyakov K. M. Semenov-Tian-Shansky 《The European Physical Journal A - Hadrons and Nuclei》2009,40(2):181-198
We establish a link between the dual parametrization of GPDs and a popular parametrization based on the double distribution
Ansatz, which is in prevalent use in phenomenological applications. We compute several first forward-like functions that express
the double distribution Ansatz for GPDs in the framework of the dual parametrization and show that these forward-like functions
make the dominant contribution into the GPD quintessence function. We also argue that the forward-like functions with
1 contribute to the leading singular small-xBj behavior of the imaginary part of DVCS amplitude. This makes the small-xBj behavior of independent of the asymptotic behavior of PDFs. Assuming analyticity of Mellin moments of GPDs in the Mellin space we are
able to fix the value of the D -form factor in terms of the GPD quintessence function N(x, t) and the forward-like function Q
0(x, t) . 相似文献
12.
A. Caciolli L. Agostino D. Bemmerer R. Bonetti C. Broggini F. Confortola P. Corvisiero H. Costantini Z. Elekes A. Formicola Zs. Fül?p G. Gervino A. Guglielmetti C. Gustavino Gy. Gyürky G. Imbriani M. Junker M. Laubenstein A. Lemut B. Limata M. Marta C. Mazzocchi R. Menegazzo P. Prati V. Roca C. Rolfs C. Rossi Alvarez E. Somorjai O. Straniero F. Strieder F. Terrasi H. P. Trautvetter 《The European Physical Journal A - Hadrons and Nuclei》2009,39(2):179-186
Ultra-sensitive in-beam -ray spectroscopy studies for nuclear astrophysics are performed at the LUNA (Laboratory for Underground Nuclear Astrophysics)
400 kV accelerator, deep underground in Italy’s Gran Sasso laboratory. By virtue of a specially constructed passive shield,
the laboratory -ray background for < 3 MeV at LUNA has been reduced to levels comparable to those experienced in dedicated offline underground -counting setups. The -ray background induced by an incident -beam has been studied. The data are used to evaluate the feasibility of sensitive in-beam experiments at LUNA and, by extension,
at similar proposed facilities. 相似文献
13.
D. Elsner B. Bantes O. Bartholomy D. E. Bayadilov R. Beck Y. A. Beloglazov R. Castelijns V. Crede A. Ehmanns K. Essig R. Ewald I. Fabry F. Frommberger K. Fornet-Ponse M. Fuchs C. Funke A. B. Gridnev E. Gutz W. Hillert S. H?ffgen P. Hoffmeister I. Horn I. Jaegle J. Junkersfeld H. Kalinowsky Frank Klein Friedrich Klein E. Klempt M. Konrad M. Kotulla B. Krusche H. L?hner I. V. Lopatin J. Lotz S. Lugert D. Menze T. Mertens J. G. Messchendorp V. Metag C. Morales M. Nanova D. V. Novinski R. Novotny M. Ostrick L. M. Pant H. van Pee M. Pfeiffer A. V. Sarantsev C. Schmidt H. Schmieden B. Schoch S. Shende A. Süle V. V. Sumachev T. Szczepanek U. Thoma D. Trnka D. Walther C. Weinheimer C. Wendel 《The European Physical Journal A - Hadrons and Nuclei》2009,39(3):373-381
At the electron accelerator ELSA a linearly polarised tagged photon beam is produced by coherent bremsstrahlung off a diamond
crystal. Orientation and energy range of the linear polarisation can be deliberately chosen by accurate positioning of the
crystal with a goniometer. The degree of polarisation is determined by the form of the scattered electron spectrum. Good agreement
between experiment and expectations on the basis of the experimental conditions is obtained. Polarisation degrees of % are typically achieved at half of the primary electron energy. The determination of is confirmed by measuring the beam asymmetry, , in photoproduction and by a comparison of the results to independent measurements using laser backscattering. 相似文献
14.
T. Shizuma T. Ishii H. Makii T. Hayakawa M. Matsuda 《The European Physical Journal A - Hadrons and Nuclei》2009,39(3):263-266
Excited states in neutron-rich 183Ta have been studied using a two-neutron transfer reaction of 181Ta(18O,16O) . In-beam -rays were measured in coincidence with scattered ions detected by a high-resolution
E -E Si telescope for reaction channel selection. Previously known 1-quasiparticle bands are extended to higher spins, and several
levels including a T
1/2 = 0.9(3) μs 3-quasiparticle isomer are identified. 相似文献
15.
After deriving the projected stress tensor in cylindrical geometry for a fluid membrane described by the Helfrich Hamiltonian,
we calculate the average force f exerted by a thermally fluctuating nanotubule of radius R , and its standard deviation
f . We obtain f and
f in terms of the internal membrane tension , the bending rigidity , the temperature k
B
T and a molecular cutoff . We find for f a shift ∼ 1/ with respect to the mean field behavior ∼ . We obtain (
f )2 ∼ R ln(R/b) where b is a molecular length,
f being typically small compared to f . Taking into account the difference between the internal tension and the actual mechanical tension applied to the membrane from which the tubule is drawn, we discuss the amplitude of the fluctuation-induced corrections to
the average force. Our results, obtained in the harmonic approximation, hold for tubules with aspect ratio not larger than
200 , of radius significantly smaller than 100nm, that are connected to a large membrane reservoir, e.g., a giant vesicle. 相似文献
16.
A.?V.?Anisovich I.?Jaegle E.?Klempt B.?Krusche V.?A.?Nikonov A.?V.?Sarantsev U.?Thoma 《The European Physical Journal A - Hadrons and Nuclei》2009,41(1):13-24
A formalism is developed for the partial-wave analysis of data on meson photoproduction off deuterons and applied to photoproduction
of and mesons. Different interpretations of a dip-bump structure of the photoproduction cross-section in the 1670MeV region are presented and discussed. Helicity amplitudes for two low-mass S11 states are determined. 相似文献
17.
The effect of confinement in the segmental relaxation of polymers is considered. On the basis of a thermodynamic model we
discuss the emerging relevance of the fast degrees of freedom in stimulating the much slower segmental relaxation, as an effect
of the constraints at the walls of the amorphous regions. In the case that confinement is due to the presence of crystalline
domains, a quasi-Poissonian distribution of local constraining conditions is derived as a result of thermodynamic equilibrium.
This implies that the average free-energy barrier
F for conformational rearrangement is of the same order of the dispersion of the barrier heights, (
F) , around
F . As an example, we apply the results to the analysis of the -relaxation as observed by dielectric broad-band spectroscopy in semicrystalline poly(ethylene terephthalate) cold-crystallized
from either an isotropic or an oriented glass. It is found that in the latter case the regions of cooperative rearrangement
are significantly larger than in the former. 相似文献
18.
Yu. A. Berezhnoy V. P. Mikhailyuk V. V. Pilipenko 《The European Physical Journal A - Hadrons and Nuclei》2009,39(1):125-131
The -cluster model with dispersion has been developed for the case of the 24Mg nucleus. The 24Mg nucleus is considered as composed of the core ( 16O nucleus) and two -clusters that form a dumbbell configuration and are arranged with the most probability inside the core. In the calculations
the -cluster structure of the core has been taken into account. On the basis of the multiple diffraction scattering theory the
differential cross-section and the polarization observables for the elastic p - 24Mg scattering at 800 and 250MeV have been calculated. The results obtained are in agreement with the existing experimental
data. 相似文献
19.
A. Majethiya B. Patel P. C. Vinodkumar 《The European Physical Journal A - Hadrons and Nuclei》2008,38(3):307-315
Properties of single heavy flavor baryons in a non-relativistic potential model with colour Coulomb plus a power law confinement
potential have been studied using a simple variational method. The ground-state masses of single heavy baryons and the mass
difference between the J
P =
+ and J
P =
+ states are computed using a spin-dependent two-body potential. Using the spin-flavour structure of the constituting quarks
and by defining an effective confined mass of the constituent quarks within the baryons, the magnetic moments are computed.
The masses and magnetic moments of the single heavy baryons are found to be in accordance with the existing experimental values
and with other theoretical predictions. It is found that an additional attractive interaction of the order of -200 MeV is
required for the antisymmetric states of (Q
c, b) . It is also found that the spin-hyperfine interaction parameters play a decisive role in hadron spectroscopy. 相似文献
20.
V. A. Tryasuchev 《The European Physical Journal A - Hadrons and Nuclei》2008,38(3):265-269
The properties of previously discovered nucleon resonances are amended basing on the recent and more detailed experimental
data about the photoproduction of -mesons on protons. 相似文献