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1.
We consider the results of experimental measurements of P-odd and P-even (left-right) and T-odd asymmetries of charged-particle emission in binary and ternary fission induced by polarized neutrons. We show what information on the ternary-fission mechanism can be obtained from a theoretical analysis of these data. 相似文献
2.
I. Piqueras M.J.G. Borge Ph. Dessagne J. Giovinazzo A. Huck A. Jokinen A. Knipper C. Longour G. Marguier M. Ramdhane V. Rauch O. Tengblad G. Walter Ch. Miehé 《The European Physical Journal A - Hadrons and Nuclei》2003,16(3):313-329
The beta-decay of the N = Z, even-even nucleus 72Kr has been studied at the ISOLDE PSB facility at CERN. Measurements of βγ and βγγ coincidences have enriched the decay scheme
of the daughter nucleus 72Br with 27 new low spin levels. A more precise half-life of T
1/2 = 17.1(2) s has been determined. Strong feeding to the 72Br ground state is established yielding an unambiguous J
π = 1+ assignment for this state. Candidates for the 72Br g.s. wave function are discussed in the framework of a self-consistent deformed mean-field calculation with SG2 Skyrme
force and pairing correlations. A search for beta-delayed particle emission was made and an upper limit of 10-6 for this decay branch obtained. The cumulated experimental level density of 1+ states has been fitted with the constant temperature formula. The comparison indicates that most likely all 1+ levels up to 1.2 MeV have been observed in this investigation. The corresponding nearest-neighbour level spacing does not
follow a Poisson distribution. The Gamow-Teller strength distribution is compared, in terms of nuclear deformation, with different
calculations made in the framework of the quasiparticle random phase approximation.
Received: 7 February 2002 / Accepted: 31 October 2002 / Published online: 6 March 2003
RID="a"
ID="a"e-mail: borge@pinar2.csic.es
RID="b"
ID="b"Present address: Centre d' Etudes Nucléaires de Bordeaux-Gradignan, Le Haut Vigneau, F-33175 Gradignan Cedex, France.
RID="c"
ID="c"Present address: University Mentouri, 25000 Constantine, Algeria.
Communicated by J. ?yst? 相似文献
3.
M. Mihara K. Matsuta D. Nishimura M. Fukuda M. Yaguchi K. Iwamoto M. Wakabayashi Y. Kamisho J. Ohno Y. Morita T. Izumikawa T. Ohtsubo S. Suzuki M. Nagashima K. Abe T. Sakai S. Momota A. Ozawa D. Nagae Y. Ishibashi Y. Abe T. Niwa T. Nagatomo T. Minamisono M. K. Kubo A. Kitagawa M. Torikoshi M. Kanazawa S. Sato 《Hyperfine Interactions》2013,219(1-3):83-88
The structural and magnetic properties of Ho substituted BiFeO3 (BHFO) have been investigated using 57Fe Mössbauer spectroscopy and X-Ray diffraction (XRD) as a function of temperature. The Mössbauer spectrum obtained at room temperature for the as-synthesized BHFO sample exhibits broadened features due to the hyperfine field distributions related to the local variation of the neighbourhood of Fe and the magnetic hyperfine splitting patterns are indicative of magnetic ordering, mostly probably screwed or slightly antiferromagnetic. The spectrum was fitted with two superimposed asymmetric sextets, with similar hyperfine magnetic fields of Bhf1 = 48.0(1) T and Bhf2 = 49.0(1) T, corresponding to rhombohedral BFO. The hyperfine fields of the magnetic components decreased systematically with increasing temperature to a ‘field distribution’ just below the Néel temperature, TN ~ 600 K. At temperatures above 600 K, the spectral line associated with the Bi25FeO40 impurity phase dominates the spectra. This phase is confirmed by XRD measurements. From the temperature dependence of the site populations of the spectral components an average Debye temperature of θ D = 240(80) K has been estimated. 相似文献
4.
K. D. Paschke 《The European Physical Journal A - Hadrons and Nuclei》2007,32(4):549-553
The control of helicity-correlated changes in the electron beam is a critical issue for the next generation of parity-violating
electron scattering measurements. The underlying causes and methods for controlling these changes are reviewed with reference
to recent operational experience at Jefferson Lab. 相似文献
5.
6.
7.
M. Avenier G. Bagieu H. Benkoula J.F. Cavaignac A. Idrissi D.H. Koang B. Vignon Richard Wilson 《Nuclear Physics A》1985,436(1):83-92
We report a measurement of the forward-backward asymmetry in the radiative capture of polarized cold neutrons in the reaction 35Cl(n, γ)36Cl where 36Cl is in the ground state. The measured value of the asymmetry is a = (1.57 ± 0.531) × 10?4. We deduce the mixing between the 2+ capture level and the neighboring 2? levelto be before corrections. A measurement of the integral asymmetry of all γ-rays in the neutron capture by 35Cl leads to agreement with measurements at Leningrad. 相似文献
8.
J. Koster 《Physics of Particles and Nuclei》2014,45(1):88-90
The PHENIX experiment probes the transverse spin structure of the proton with asymmetries of particle production in polarized proton collisions. This talk summarizes the measurements of A N in hadron production at forward and at mid rapidities. 相似文献
9.
通过第一性原理计算研究了具有锯齿状边沿并且具有反铁磁构型的单层石墨纳米带的自旋极化输运.研究发现,在中心散射区同一位置掺入单个B和N原子,尽管对整个体系磁矩的影响完全相同,但对两个自旋分量电流的影响却完全相反.掺B时,自旋向上的电流显著大于自旋向下的电流;而掺N时,自旋向下的电流显著大于自旋向上的电流.这是由于不管掺B还是掺N都将打破自旋简并,使得导带和价带中自旋向上的能级比自旋向下的能级更高.掺B引入空穴,使完全占据的价带变为部分占据,从而自旋向上的能级正好处于费米能级,使得电子透射能力更强、电流更大,而自旋向下的能级则离费米能级较远使电子透射的能力较弱.掺N则引入电子,使得原来全空的导带变为部分占据,从而费米能级穿过导带中自旋向下的能级,使得自旋向下的电子比自旋向上的电子透射能力更强.
关键词:
自旋极化输运
单层石墨纳米带
第一性原理
非平衡格林函数 相似文献
10.
Y. Kuno J. Imazato K. Nishiyama K. Nagamine T. Yamazaki K. Matsuta S. Ise Y. Nojiri T. Minamisono 《Hyperfine Interactions》1988,39(3):253-267
NMR measurements on12B nuclei implanted in a thin sheet of highly oriented pyrolytic graphite (Grafoil) have been made to study the magnitude of
the polarization of12B and its electric quadrupole coupling. The magnitude of the residual polarization of12B held in carbon material is of crucial importance to the experiment measuring the average polarization of12B produced in the muon capture by12C. It was found that the polarization of12B can be maintained at 101.0±2.2% in Grafoil under a magnetic field of 3 kG. The electric quadrupole coupling was determined
to bee
2
qQ/h=+1207.3±8.2 kHz. From the magnitude and the sign of the electric field gradienteq, the location of12B was found to be a substitutional site in the carbon lattice. The anomalous B-C bond involving thesp
2
hybrid orbitals with partially filledp
z
electrons is also discussed. 相似文献
11.
Nuclear dipolar brondening in the NMR spectra of beta-emitting12B and12N implanted in single crystal Mg with h.c.p. structure was studied as function of orientation of the crystal axes relative
to the external magnetic field. The implanted12N was located in interstitial trigonal site. The surrounding Mg atoms nearest to the12N were displaced from the regular lattice position, and lattice expansion δa/a=0.15 was determined. 相似文献
12.
S. Arnold K. Goeke A. Metz P. Schweitzer W. Vogelsang 《The European physical journal. Special topics》2008,162(1):31-36
Longitudinal, parity-violating single spin asymmetries in proton-proton collisions for RHIC kinematics are considered. The
focus of this study is on the production of a single jet as well as a hadron containing a charm quark. While the asymmetry
for jets is rather small, considerably larger effects can be expected for the production of charm because of the strongly
reduced QCD background. The general outcome of a fixed order calculation is not much affected by the resummation of large
threshold logarithms. 相似文献
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14.
S. G. Kadmensky V. E. Bunakov L. V. Titova 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(11):1177-1181
T-odd asymmetries in the ternary fission of oriented target nuclei, induced by cold unpolarized neutrons and accompanied by emission of ?? particles, are described using quantum fission theory. The differential cross section for the reaction in question is obtained using the spin density matrix of the target nucleus by considering the Coriolis interaction of the spin of a fissioning compound nucleus with the orbital momentum of an ?? particle and interference from the fission amplitudes of various pairs of neutron resonances excited in the compound nucleus as the target nucleus captures a cold neutron. It is shown that in the case under consideration, T-odd asymmetries occur only at odd values of the target nucleus??s order of orientation. It is demonstrated that the concepts of TRI and ROT asymmetries are preserved while the absolute values of the coefficients for these asymmetries can change noticeably in comparison to the similar coefficients for the fission of unoriented target nuclei induced by cold polarized neutrons. 相似文献
15.
H. Fraas 《Nuclear Physics B》1976,113(3):532-546
We discuss the cross-section asymmetries for forward diffractive vector meson (ρ0) production by inelastic scattering of longitudinally polarized electrons (or muons) on polarized protons. Only for the case when both the beam and the target are polarized can considerable effects be expected. On the basis of the off-diagonal GVDM we give relations between the cross section asymmetries in ep → epρ0 (forward direction) and in ep → eX. For a longitudinally polarized target the cross-section asymmetries in ep → epρ0 are predicted to be roughly twice as large as in ep → eX. 相似文献
16.
Airapetian A Akopov N Akopov Z Amarian M Andrus A Aschenauer EC Augustyniak W Avakian R Avetissian A Avetissian E Bacchetta A Bailey P Balin D Beckmann M Belostotski S Bianchi N Blok HP Böttcher H Borissov A Borysenko A Bouwhuis M Brüll A Bryzgalov V Capitani GP Cappiluppi M Chen T Ciullo G Contalbrigo M Dalpiaz PF Leo RD Demey M Nardo LD Sanctis ED Devitsin E Nezza PD Düren M Ehrenfried M Elalaoui-Moulay A Elbakian G Ellinghaus F Elschenbroich U Fabbri R Fantoni A Fechtchenko A Felawka L 《Physical review letters》2005,94(1):012002
Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic scattering of positrons are measured for the first time with transverse target polarization. The asymmetry depends on the azimuthal angles of both the pion (phi) and the target spin axis (phi(S)) about the virtual-photon direction and relative to the lepton scattering plane. The extracted Fourier component sin((phi+phi(S))(pi)(UT) is a signal of the previously unmeasured quark transversity distribution, in conjunction with the Collins fragmentation function, also unknown. The component sin((phi-phi(S)(pi)(UT) arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson production. 相似文献
17.
Beta-ray angular distributions from aligned12B and12N have been observed in order to study the meson-exchange effect in a nucleus. Alignment-correlation coefficients for12B and12N were determined to be –=–(0.0174±0.0059)%/MeV and +=–(0.2774±0.0086)%/MeV, respectively. These values are fairly consistent with the previous values, while the reliability was greatly improved. From these coefficients, the nuclear parametery, i.e. the ratio of the time component of the axial vector currents of the Gamow-Teller matrix element, was determined to bey=4.13±0.15. The value is enhanced by 33% from that calculated by use of the impulse approximation, which clearly shows a considerable effect due to meson-exchange currents. 相似文献
18.
Abe K Abe K Abe T Adam I Akimoto H Aston D Baird KG Baltay C Band HR Barklow TL Bauer JM Bellodi G Berger R Blaylock G Bogart JR Bower GR Brau JE Breidenbach M Bugg WM Burke D Burnett TH Burrows PN Calcaterra A Cassell R Chou A Cohn HO Coller JA Convery MR Cook V Cowan RF Crawford G Damerell CJ Daoudi M de Groot N de Sangro R Dong DN Doser M Dubois R Erofeeva I Eschenburg V Etzion E Fahey S Falciai D Fernandez JP Flood K Frey R Hart EL Hasuko K Hertzbach SS Huffer ME Huynh X Iwasaki M 《Physical review letters》2001,86(7):1162-1166
We present final measurements of the Z boson-lepton coupling asymmetry parameters A(e), A(mu), and A(tau) with the complete sample of polarized Z bosons collected by the SLD detector at the SLAC Linear Collider. From the left-right production and decay polar angle asymmetries in leptonic Z decays we measure A(e) = 0.1544+/-0.0060, A(mu) = 0.142+/-0.015, and A(tau) = 0.136+/-0.015. Combined with our left-right asymmetry measured from hadronic decays, we find A(e) = 0.1516+/-0.0021. Assuming lepton universality, we obtain a combined effective weak mixing angle of sin (2)theta(eff)(W) = 0.230 98+/-0.000 26. 相似文献
19.
N. G. Deshpande 《Pramana》2003,60(2):353-362
We briefly discuss measurements of angles β and α of the unitarity triangle. We then review rate asymmetries usingSU(3) relationships in the standard model (SM). Some methods to measure angle y usingSU(3) are then discussed. We note that rate forb →
sγ can be used to set limits on extra dimensions in which standard model particles propagate. 相似文献
20.
《Physics letters. [Part B]》1988,202(3):411-416
We propose a strategy to express some of the electroweak parameters characterizing a certain type of new physics beyond the standard model through “new physics sum rules” involving experimentally measureable e+e− polarization asymmetries on (near) the Z resonance. In the case of a single E6-generated new Z′, our sum rules would provide an unambiguous measurement of the mixing angle for |θM|⩾0.04. 相似文献