共查询到20条相似文献,搜索用时 47 毫秒
1.
The dynamic changes in ferroelectric liquid crystal (FLC) molecular alignments under an applied electric field are examined
by observing the formation of conoscopic figures with a time resolution of 0.1 ms. Close agreements between observed and simulated
conoscopic figures under low voltage (30 V) were obtained. Under high voltage (120 V), however, the observed conoscopic figures
became blurred between 0.8 ms and 1.1 ms after reversal of the electric field. The light scattering producing the blurriness
occurred due to the development of fast transient molecular alignments during the switching transition above the applied voltage
70 V. 相似文献
2.
A. A. Kuznetsov Yu. A. Panebrattsev R. Togoo B. Baatar 《Physics of Particles and Nuclei Letters》2006,3(2):99-112
The charged π-meson and proton mixed hadronic jets in the fragmentation regions of π− + p and π− + C interactions at 40 GeV/c are extracted and their properties are investigated. It has been shown that the characteristics of the jets in the π−-meson fragmentation region are universal in jet events, do not depend on the type of the target and are defined only from
the quark contents of the π− meson. The jet characteristics in the proton fragmentation region are different and depend upon the quark contents of the
proton. Mixed hadronic jets with defined values of the electric charge were studied. The resonance structures related to the
Δ isobars are discovered in the effective mass distributions of the jets. It has been shown that the small azimuthal angle
high-p
T
correlations are observed and strong back-to-back correlations exist.
The text was submitted by the authors in English. 相似文献
3.
Jiangyong Jia 《Indian Journal of Physics》2011,85(1):149-154
We provide a detailed survey study of dihadron azimuthal angle (Δϕ) correlations in a broad range of transverse momentum (0.4 < p
T
< 10 GeV/c) and centrality (0–92%) in Au+Au collisions at 149-2 = 200 GeV. The evolution of the jet shape and yield with p
T
seems to suggest two distinct components at the away-side pairs: a suppressed jet fragmentation component around Δϕ ∼ π, and a medium-induced components around |Δϕ − π| ∼ 1.1. The former dominates p
T
> 5 GeV/c and the later dominates at p
T
< 4 GeV/c. 相似文献
4.
Bijan K Bagchi 《Pramana》1981,17(5):405-414
We consider the effects ofη−π mixing on the violation of the |ΔI|=1/2 rule in |ΔS|=1 weak transitions. The processes considered are theK→2π,K→3π, Λ, Ξ and Λ hyperon decays. 相似文献
5.
I. Horn A. V. Anisovich G. Anton R. Bantes O. Bartholomy R. Beck Y. Beloglazov R. Bogendörfer R. Castelijns V. Credé A. Ehmanns J. Ernst I. Fabry H. Flemming A. Fösel M. Fuchs Ch. Funke R. Gothe A. Gridnev E. Gutz S. Höffgen J. Hößl J. Junkersfeld H. Kalinowsky F. Klein E. Klempt H. Koch M. Konrad B. Kopf B. Krusche J. Langheinrich H. Löhner I. Lopatin J. Lotz H. Matthäy D. Menze J. Messchendorp V. Metag V. A. Nikonov D. Novinski M. Ostrick H. van Pee A. V. Sarantsev C. Schmidt H. Schmieden B. Schoch G. Suft V. Sumachev T. Szczepanek U. Thoma D. Walther Ch. Weinheimer 《The European Physical Journal A - Hadrons and Nuclei》2008,38(2):173-186
The reaction γp → pπ0η has been studied with the CBELSA detector at the tagged photon beam of the Bonn electron stretcher facility. The reaction
shows contributions from Δ+(1232)η , N(1535)+π0 and pa
0(980) as intermediate states. A partial-wave analysis suggests that the reaction proceeds via formation of six Δ -resonances,
Δ(1600)P
33 , Δ(1920)P
33 , Δ(1700)D
33 , Δ(1940)D
33 , Δ(1905)F
35 , Δ(2360)D
33 , and two nucleon resonances N(1880)P
11 and N(2200)P
13 , for which pole positions and decay branching ratios are given. 相似文献
6.
Normal (N) metallic (Ag) mesoscopic conductors with two superconducting (S) faces (Al), arranged mirror-symmetrically relative
to the streamlines of the current, periodically switch into the normal state as the superconducting phase difference Δϕ between
the NS boundaries approaches the values Δϕ =(2n+1)π, n=0,1,2,..., irrespective of temperature and applied voltage. For Δϕ =2nπ and low applied voltages the conductance passes through a maximum and approaches the normal value as temperature decreases
(reentrance). As the voltage subsequently increases, the conductance increases and passes through a maximum. As the phase
difference moves away from the values Δϕ=2nπ, the maxima shift in the direction of low temperatures and voltages. The latter result shows unequivocally that in our metal
structures it is necessary to take into account the next-order corrections to the “weak” proximity effect approximation.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 7, 489–494 (10 April 1998) 相似文献
7.
T. Matulewicz L. Aphecetche Y. Charbonnier H. Delagrange K.K. Gudima G. Martınez M. Płoszajczak Y. Schutz V.D. Toneev M. Appenheimer R. Averbeck J. Dıaz A. Döppenschmidt M.J. van Goethem S. Hlavač M. Hoefman R. Holzmann F. Lefèvre A. Kugler H. Löhner A. Marın V. Metag R. Novotny R.W. Ostendorf R.H. Siemssen R.S. Simon R. Stratmann H. Ströher P. Tlusty P.H. Vogt V. Wagner J. Weiss H.W. Wilschut F. Wissmann A.R. Wolf M. Wolf 《The European Physical Journal A - Hadrons and Nuclei》2000,9(1):69-72
Proton-π0 coincidences have been measured at the beam energy of 180A MeV in the reaction Ar+Ca studied by TAPS at SIS/GSI. In the proton-π0 invariant mass spectrum we observe a significant excess of strength above the background obtained by event mixing. We attribute
this signal to the strength distribution N
Δ of the Δ baryonic resonance. No correlation is observed in the case of deuteron-π0 coincidences. Assuming isotropic emission of π0 and Δ+ from a midrapidity thermal source and isospin symmetry, we determined the global N
Δ/N
πratio of 0.79 ±0.30(stat) ±0.2(syst). This value indicates that most pions produced at subthreshold energy in heavy-ion reaction
are mediated by the Δ-resonance.
Received: 7 April 2000 / Accepted: 29 August 2000 相似文献
8.
K. Kamiyama D. Shiomi S. Hase M. Nishizawa K. Sato M. Kozaki K. Okada T. Takui 《Applied magnetic resonance》2000,19(1):45-57
A crystal-engineering approach to organic ferrimagnets is reported. Coulombic energy between an anionic biradical withS = 1 and a cationic monoradical withS = 1/2 can be utilized as a driving force of cocrystallization of open-shell molecules with different spin quantum numbers,
leading to organic salt ferrimagnets. In this study, 3,5-substituted phenol and benzoic acid derivatives of nitronyl nitroxide
biradicals were synthesized as an ionizableS = 1 component of organic salt ferrimagnets. The molecular ground states of the biradicals in the neutral state were examined
by continuous wave electron spin resonance (ESR) spectroscopy and static paramagnetic susceptibility measurements in the solid
state. The molecular ground state of the phenol derivative was found to be triplet (S = 1) with the singlet-triplet energy gap of ΔE/kB ≈ 25 K, indicating that the biradical can be a building block of organic salt ferrimagnetics. The benzoic acid derivative
was found to have a singlet (S = 0) ground state (ΔE/kB
≧ −5 K), exemplifying thatmeta-(3,5)-linkage of unpaired electrons in π-aromatic rings does not necessarily give a triplet ground state for heteroatomic-substituted
π conjugation. The molecular ground states of the biradicals determined in the ESR experiments were confirmed by the susceptibility
in the solid state. 相似文献
9.
Khusniddin K. Olimov Mahnaz Q. Haseeb Alisher K. Olimov Imran Khan 《Central European Journal of Physics》2011,9(6):1393-1409
The production of Δ0(1232)-resonances in p+12C collisions at 4.2 GeV/c was analyzed with 4π acceptance. The mass distribution of Δ0(1232) was reconstructed using an angular criterion. The fraction of charged π
−-mesons coming from Δ0(1232) decay was estimated and compared to those obtained in earlier works. The momentum, transverse momentum, kinetic energy,
and rapidity distributions as well as invariant cross sections of Δ0(1232)-resonances were reconstructed in the laboratory frame. The mean kinematical characteristics of the reconstructed Δ0(1232) were compared to those of participant protons in experiment and within some of the models. The freeze-out temperature
of Δ0(1232) estimated in the present analysis was compared with those obtained using different methods for Δ(1232) produced with
other sets of colliding nuclei at various incident energies. The relative number of nucleons excited to Δ0 (1232) at freeze-out conditions in p+12C collisions was estimated. 相似文献
10.
Zhi-Gang Wang 《The European Physical Journal C - Particles and Fields》2008,57(4):711-718
We calculate the strong coupling constant g
ΔN
π
and study the strong decay Δ++→p
π with light-cone QCD sum rules. The numerical value of the strong coupling constant g
ΔN
π
is consistent with the experimental data. The small discrepancy may be due to the failure to take into account perturbative
corrections. 相似文献
11.
Yu. A. Simonov 《JETP Letters》2008,87(3):121-123
The dipion spectrum for the ϒ(nS) → ϒ(n′S) transition with n < 4 has the form dw/dq ∼ (phase space) |η − x|2, with x = q
2 − 4m
π2 / (ΔM)2 − 4m
π2 < q
2 ≡ M
ππ2, and ΔM = M(nS) − M(n′S). The parameter η is calculated and the spectrum is shown to reproduce the experimental data for all three types of decays:
3 → 1, 2 → 1, and 3 → 2 with η ≈ 0.5, 0, and −3, respectively.
The text was submitted by the author in English. 相似文献
12.
G. Fäldt U. Tengblad C. Wilkin 《The European Physical Journal A - Hadrons and Nuclei》2006,28(2):245-249
The cross-section for the dd →^4Heππ reaction is estimated near threshold in a two-step model where a pion created in a first interaction produces a second
pion in a subsequent interaction. This approach, which describes well the rates of 2π and η production in the pd →^3Heππ and dd →^4Heη reactions, leads to predictions that are much too low compared to experiment. Alternatives to this and the double-Δ
model will have to be sought to explain these data. 相似文献
13.
Nagatomo T. Matsuta K. Hashimoto K. Ota M. Arimura K. Minamisono K. Sumikama T. Ogura M. Iwakoshi T. Miyake T. Kudo S. Akutsu K. Minamisono T. Fukuda M. Mihara M. Momota S. Nojiri Y. Kitagawa A. Torikoshi M. Kanazawa M. Suda M. Hirai M. Symons T. J. M. Krebs G. F. Alonso J. R. Zhu S. Y. Zhu J. Z. Xu Y. J. 《Hyperfine Interactions》2001,136(3-8):233-237
The nuclear spin alignments of the β-emitting fragments 12B(I
π=1+, T
1/2=20.2 ms) and 13B(I
π=3/2−, T
1/2=17.4 ms) produced in the 100A-MeV 13C, 15N + 9Be collisions respectively have been observed for the first time detecting asymmetric β-ray emission from these nuclei. By
means of the spin manipulation technique based on the hyperfine interaction of B isotopes in TiO2, both the polarization P and the alignment A were determined reliably. The obtained P and A were significantly smaller than the expectation from the kinematical model. From the fact that the quenching factors for
P and A are almost the same, there may be some depolarization mechanism in the collision process itself.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
14.
The production of Δ
0(1232)-resonances in p + 12C collisions at 4.2 GeV/c was investigated with 4π acceptance. The masses and widths of the resonances were obtained from ananalysis of foreground and background invariant-mass
distributions of pπ
− pairs obtained using an angular criterion. The fraction of charged π
−-mesons coming from the Δ
0(1232) decay was estimated and compared to those obtained in earlier analyses. The momentum, transverse momentum, kinetic
energy, rapidity, and emission angle distributions as well as the invariant cross-sections of Δ
0(1232)-resonances werere constructed in the laboratory frame. The freeze-out temperature of theΔ
0(1232)-resonances produced in p + 12C collisions was estimated and compared to the freeze-out temperatures obtained using different methods for Δ(1232)-resonances produced in other experiments with different sets of colliding nuclei at various incident energies. 相似文献
15.
K. A. Gridnev A. T. D’yachenko V. N. Baryshnikov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(4):471-474
We propose including in the calculation of the cross section of the process p + N → N + N + π the process of pion production and absorption that proceeds through creation of a Δ-resonance. By taking into account
the energy dependence of Δ-resonance width, the contribution of deuteron channel is included in the cross section of π0-, π+-meson production. 相似文献
16.
I. V. Glavanakov P. Grabmayr Yu. F. Krechetov A. N. Tabachenko 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(6):747-749
Experimental research on positive-pion photoproduction on the oxygen nucleus in the 16O(γ, π+p) reaction at high recoil momenta of the residual nuclear system was performed. The yield for the 16O(γ, π+p) reaction was analyzed using a model that takes Δ-isobar configurations in nuclei ground states into account, together with
the earlier-measured yield of the12C(γ, π+p) reaction. The estimated number of isobars per nucleon N
Δ = 0.012 ± 0.005 was obtained for the 12C nucleus, and 16O N
Δ = 0.018 ± 0.004 was obtained for the 16O nucleus. 相似文献
17.
The difference of the energies of levels Δ
n
= E
lev(2+0
n
) − E
lev(0+0
n
) at n = 1, 2, and 3 and the multipole-mixture parameter δ for (2+02−2+01) and (2+03−2+01) transitions are contrasted against the structure of the K
π
= 02+ and 03+ rotational bands that was calculated on the basis of the quasiparticle-phonon model. The values of (Δ2 − Δ1), (Δ3 − Δ1), and (Δ2 − Δ3) are found to correlate with the sign of the parameter δ and with the calculated structure of the K
π
= 02+ and 03+ bands.
Original Russian Text ? A.M. Demidov, L.I. Govor, V.A. Kurkin, I.V. Mikhailov, 2009, published in Yadernaya Fizika, 2009,
Vol. 72, No. 2, pp. 236–240. 相似文献
18.
Vladimir G. Neudatchin Igor T. Obukhovsky Ludmila L. Sviridova Nikolai P. Yudin 《Central European Journal of Physics》2004,2(3):511-522
The pion momentum distributions (MDs) in four channels of virtual decay p→B+π, B = N, Δ, N
1/2-(1535), N
1/2+(1440) are calculated in two models, the microscopic model of 3
P
0 scalar q−q fluctuation with the pion as a composite q−q-system and the chiral semi-microscopic model of πq interaction with the pion as a structureless Goldstone boson. The results of the above models are similar for the baryon
states B = N, Δ, N
1/2-(1535) but are rather different for the Roper resonance N
1/2+(1440) which corresponds to excitation of two oscillator quanta in the nucleon. The experimental investigation of pion MDs
by means of the reaction of quasi-elastic knockout of pion by an electron of a few GeV energy p(e, e′ π)B may be very suitable for Jefferson Laboratory, Virginia (JLab). 相似文献
19.
J. Ahrens S. Altieri J. R. M. Annand H. -J. Arends R. Beck M. A. Blackston C. Bradtke A. Braghieri N. d'Hose H. Dutz A. Fix S. Goertz P. Grabmayr S. Hasegawa E. Heid H. Holvoet N. Horikawa T. Iwata O. Jahn P. Jennewein F. Klein R. Kondratiev M. Lang B. Lannoy V. Lisin M. Martinez-Fabregate J. C. McGeorge W. Meyer A. Panzeri P. Pedroni T. Pinelli I. Preobrajenski G. Reicherz Ch. Rohlof G. Rosner M. Rost T. Rostomyan D. Ryckbosch M. Schumacher B. Seitz G. Tamas A. Thomas R. Van de Vyver H. R. Weller F. Zapadtka 《The European Physical Journal A - Hadrons and Nuclei》2007,34(1):11-21
The helicity dependence of the total cross-section and the invariant-mass distributions in the (pπ±) and (π+π-) final states for the γp → pπ+π- reaction have been measured for the first time at incident photon energies from 400 to 800MeV. The measurement was performed
with the large-acceptance detector DAPHNE at the tagged photon beam facility of the MAMI accelerator in Mainz. Although this
channel is found to be predominantly excited by the intermediate production of a Δπ state, both the measured unpolarized and
the helicity-dependent observables are generally not well described by the existing theoretical models. 相似文献
20.
Experimental data on πN scattering in the elastic energy region T
π ≤ 250 MeV are analyzed within the multichannel K-matrix approach with effective Lagrangians. Isospin invariance is not assumed in this analysis and the physical values for
masses of the involved particles are used. The corrections due to π
+-π
0 and p-n mass differences are calculated and found to be in a reasonable agreement with the NORDITA results. The results of our analysis
describe the experimental observables very well. New values for mass and width of the Δ0 and Δ++ resonances were obtained from the data. The isospin-symmetric version yields phase-shift values similar to the new solution,
FA02, for the πN elastic scattering amplitude by the GW group based on the latest experimental data. While our analysis leads to a considerably
smaller (≤1%) isospin violation in the energy interval T
π ∼ 30–70 MeV as compared to 7% in works by W.R. Gibbs et al. and E. Matsinos, it confirms calculations based on chiral perturbation
theory.
The text was submitted by the authors in English. 相似文献