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1.
Though the predictions of the standard model (SM) are in excellent agreement with experiments, there are still several theoretical
problems associated with the Higgs sector of the SM, where it is widely believed that some new physics will take over at the
TeV scale. One beyond the SM theory which resolves these problems is the Little Higgs (LH) model. In this work we have investigated
the effects of the LH model on γγ → γγ scattering [1].
相似文献
2.
A. V. Daniel J. H. Hamilton A. V. Ramayya A. S. Fomichev Yu. Ts. Oganessian G. S. Popeko A. M. Rodin G. M. Ter-Akopian J. K. Hwang D. Fong C. Goodin K. Li J. O. Rasmussen D. Seweryniak M. Carpenter C. J. Lister Sh. Zhu R. V. F. Janssens J. Batchelder J. Kliman L. Krupa W. -C. Ma S. J. Zhu L. Chaturvedi J. D. Cole 《Physics of Atomic Nuclei》2006,69(8):1405-1408
A new experiment devoted to the fission of 252Cf is described. It continued a series of our experiments based on correlation measurements of γ rays emitted by fission fragment pairs. The measurements of γ-γ and γ-γ-γ coincidences were done at Gammasphere with closed 252Cf sources. The open source was used for the first time in the last experiment. Fission fragment detectors were arranged in
the center hole of Gammasphere. Correlations between fission fragment masses, total kinetic energy, and γ rays were observed. The first, preliminary results of data analysis are discussed.
The text was submitted by the authors in English. 相似文献
3.
We show that gamma-ray stimulated emission experiments are comparatively easy and inexpensive. The registration of a double-
(N2γ/Nγ) and a triple-energy peak (N3γ/Nγ) is possible and the relation between their intensities permits the calculation of the recoilles factor fs (stimulated) and making a conclusion about constructing a working gamma-ray laser.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
V.B. Gavrikov V.P. Likhachev J.D.T. Arruda-Neto A.L. Bonini 《The European Physical Journal A - Hadrons and Nuclei》2001,12(4):487-493
Differential and integral features of incoherent X-radiation, induced by relativistic electrons in crystals, are studied for
observation angles θγ several times greater than γ-1, where γ is the projectile Lorentz factor. The existence of sharp maxima and a minimum of the five-folded incoherent differential
cross-section as a function of the final electron angles, and a dip minimum when the cross-section is taken as a function
of the photon energies, is demonstrated. At near backward observation angles the three-folded cross-section shows a maximum
in the region of several keV photon energies. The obtained results allow us to optimize the conditions for coincidence experiments,
minimizing the incoherent contribution to the total radiation yield, and helping to analyse results of finite-size detector
experiments with crystal targets.
Received: 2 July 2001 / Accepted: 26 November 2001 相似文献
5.
Z.G. Gan Z. Qin J.S. Guo L.J. Shi H.Y. Liu T.R. Guo X.G. Lei R.C. Ma W.X. Huang S.G. Yuan X.Q. Zhang G.M. Jin 《The European Physical Journal A - Hadrons and Nuclei》1999,6(1):59-61
The decay of 131Pm has been investigated by means of γ-ray spectroscopy. The 131Pm nuclei were produced by fusion-evaporation reaction of 106Cd(32S,3p4n) at the beam energy of 170 MeV. A helium-jet technique and a tape transport system were used to collect the activities
and transfer them to a detecting position for X and γ rays measurement. Two γ rays of 185.0 and 220.0 keV were unambiguously
identified to follow the β+ decay of 131Pm by results of X-γ and γ–γ coincidence. A growth-decay feature of the decay curve for 87.8 keV γ-ray of 131Nd confirmed the production of 131Pm nuclei. The half-life of 131Pm was measured to be 6.3 ± 0.8 s. A partial decay scheme of 131Pm is proposed on the basis of X-γ and γ–γ coincidence data in this experiment and the known structure information deduced
from in-beam experiments of the daughter nucleus 131Nd.
Received: 11 January 1999 / Revised version: 20 May 1999 相似文献
6.
G. G. Bunatyan 《Journal of Experimental and Theoretical Physics》1999,89(5):811-820
Since the emission of γ grays unavoidably accompanies β decay, the final state after the β decay of a neutron includes a photon along with a proton, an electron, and an antineutrino, i.e., four particles, rather
than three. Therefore, when only the electron and proton momenta are detected and the γ-ray momentum is not detected in an experiment, the antineutrino momentum cannot be uniquely reconstructed, and only its mean
value over a γ-ray momentum distribution determined from corresponding calculations can be considered. The γ grays are significant for finding the asymmetry parameter B of the antineutrino angular distribution from experiments on the β decay of polarized neutrons, where the electron momentum p directed along the x axis and the projection of the proton momentum P
x onto the x axis are detected, and the neutron polarization vector ξ is parallel or antiparallel to x. Since the γ rays are not detected in such experiments, the antineutrino kinematics are not uniquely specified by the observables p and P
x and can be reconstructed only on the average, so that the antineutrino momentum distribution averaged over a γ-ray momentum distribution is considered. Thus, the exact value of B cannot be obtained from these experiments, but the true value of B can be estimated on the average by considering the mean (most likely) value 〈B〉 and the dispersion (rms deviation) ΔB. The unavoidable uncertainty in the estimate of B amounts to several percent and is thus significant for present-day experiments, which are intended to obtain the value of
B to a very high accuracy of ∼ (0.1–1)%. If electromagnetic interactions are taken into account, measurements of the electron
and proton momentum distributions can also be used to obtain g
A, i.e., the axial β-decay amplitude, to high accuracy.
Zh. éksp. Teor. Fiz. 116, 1505–1522 (November 1999) 相似文献
7.
Characterization of the interaction between methylene blue (MB) and calf thymus deoxyribonucleic acid (ctDNA) was investigated
by UV absorption spectra, fluorescence spectra, fluorescence polarization and fluorescence quenching experiments by ferrocyanide.
The above results indicated that the binding modes of MB to ctDNA were relative to the molar ratio γ (γ=[DNA]/[MB]). At low
γ ratios (γ < 4), remarkable hypochromic effect with no shift of λmax in the absorption spectra of MB was observed in the presence of increasing amounts of ctDNA, the fluorescence of MB was efficiently
quenched by the ctDNA bases and the fluorescence polarization of MB was slightly increased, which indicated that MB cations
bound to phosphate groups of ctDNA by electrostatic interaction and then stacked on the surface of ctDNA helix. While at high
γ ratios (γ > 6), besides the fluorescence of MB was quenched efficiently by the ctDNA bases, a red shift (about 3 nm) in
the absorption spectra of MB was observed and the fluorescence polarization of MB was obviously increased, which indicated
the intercalation binding that MB molecules were intercalated into the space of two neighbouring DNA base pairs was the preferred
mode. Effects of K4Fe(CN)6 on the fluorescence quenching of the MB-ctDNA system at low and high γ ratios were also performed. The results showed that
at γ = 1.7, the quenching effect by ferrocyanide was higher than that of pure MB, while at γ = 13.6 a decreased quenching
of the fluorescence intensity was observed as compared with that of pure MB, which further proved the above conclusion. In
addition, the mechanisms of the hypochromic effect and the fluorescence quenching were also discussed in detail. 相似文献
8.
E.O. Iltan 《The European Physical Journal C - Particles and Fields》2006,48(2):605-612
We study the branching ratios of the lepton flavor violating processes μ→eγ, τ→eγ and τ→μγ by considering that the new Higgs scalars localize with Gaussian profile in the extra dimension. We see that the BRs of the LFV decays μ→eγ, τ→eγ and τ→μγ are at the order of magnitude of 10-12, 10-16 and 10-12 in the considered range of the free parameters. These numerical values are slightly suppressed in the case that the localization points of new Higgs scalars are different from the origin. 相似文献
9.
A. S. Prishchepov G. D. Kochubeev N. D. Kochubeeva 《Journal of Applied Spectroscopy》1999,66(3):353-360
Absorption spectra and dispersion of optical rotation (DOR) are measured for monomers of 6,γ- and,7,γ-dimethyl ethers of chlorin e6 (Ch-6,γ-DME and Ch-7,γ-DME) in 96% ethanol and for associates of them that are polymers and colloidal particles. The optical activity of Ch-6,γ-DME
monomers is higher than that of Ch-7,γ-DME monomers, which is linked with more pronounced distortion of the molecular macrocycle for Ch-6,γ-DME in the γ-C6 local region. The structural and energy parameters of dimeric unit cells of Ch-6,γ-DME and Ch-7,γ-DME polymers are discussed from the standpoint of the Davydov-Tinoko exciton theories. Longwave absorption spectra and
DOR are resolved into individual components with the aid of a modified Alentsev-Fock method.
Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072,
Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 331–337, May–June, 1999. 相似文献
10.
Recent theoretical calculations show for defect complexes in semiconductors, characterized by electric field gradients (EFG),
that their chemical compositions, electronic charge states and the induced lattice relaxations can be obtained by comparing
the experimental and calculated EFG. The experimental data are obtained by perturbed γγ angular correlation experiments and
the calculations are performed using ab initio full potential methods in the framework of density functional theory.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
11.
《The European Physical Journal C - Particles and Fields》2008,54(1):61-72
Results of background measurements with a prototype of the Borexino detector were used to search for 478 keV solar axions
emitted in the M1-transitions of 7Li*. The Compton conversion of axion to a photon A+e→e+γ, axioelectric effect A+e+Z→e+Z, decay of axion in two photons A→2γ and
Primakoff conversion on nuclei A+Z→γ+Z are considered. The upper limit on constants of interaction of axion with electrons,
photons and nucleons – gAegAN≤(1.0–2.4)×10-10 at mA≤450 keV and gAγgAN≤5×10-9 GeV-1 at mA≤10 keV are obtained (90%c.l.). For heavy axions with mass at 100<mA<400 keV the limits gAe<(0.7–2.0)×10-8 and gAγ<10-9–10-8 are obtained in assumption that gAN depends on mA as for KSVZ axion model. These limits are stronger than obtained in previous laboratory-based experiments using nuclear reactor
and artificial radioactive sources.
PACS 14.80.Mz; 29.40.Mc; 26.65.+t 相似文献
12.
We give an overview of low-energy Compton scattering γ(∗)
p → γp with a real or virtual incoming photon. These processes allow the investigation of one of the fundamental properties of the
nucleon, i.e. how its internal structure deforms under an applied static electromagnetic field. Our knowledge of nucleon polarisabilities
and their generalization to non-zero four-momentum transfer will be reviewed, including the presently ongoing experiments
and future perspectives. 相似文献
13.
We propose a new method for γ-direction measurements for the CsI calorimeter of the E391 experiment. This method is based
on using the GRRBF neural network. By using this method, the sensitivity of the E391 experiment could be significantly increased.
Current results could be applied to other experiments in which the same γ detector is used. 相似文献
14.
L.V. Fil'kov V.L. Kashevarov 《The European Physical Journal A - Hadrons and Nuclei》1999,5(3):285-292
The Compton scattering on a charged pion and the process γγ→π0π0 are studied using the dispersion relations. Unknown parameters of the S-wave ππ interaction and a sum and a difference of the π0 meson polarizabilities are found from a fit to the experimental data for the γγ→π0π0 process. The found parameters of the ππ interaction are used for the calculation of the cross section of the elastic γπ± scattering. The analysis of the obtained results shows that the experimental data for the elastic γπ± scattering in the energy region up to 1 GeV together with the data for the γγ→π0π0 process could be used both for a determination of the pion polarizability values and for study of the S-wave ππ interaction.
Received: 20 November 1998 / Revised version: 22 January 1999 相似文献
15.
L. Labzowsky D. Solovyev G. Plunien G. Soff 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,37(3):335-343
Two-photon transitions in the hydrogen atom are analytically evaluated within the
nonrelativistic limit utilizing the Coulomb Green function method.
The two-photon emission probability for the transition process
2s→2γ(E1)+1s serves as a test for the other calculations and was
compared with the results of previous analytical and numerical calculations. The
two-photon emission probabilities for the processes 2p→
γ(E1)+γ(M1)+1s and 2p→γ(E1)+γ(E2)+1s are also evaluated
and compared with previous numerical calculations. Different nonrelativistic “forms" for
the decay probabilities in combination with different gauge choices are considered. 相似文献
16.
A scenario that removes the contradiction between the suppression of the η(1475) → γγ decay width and the strong coupling
of η(1475) to the ρρ, ωω, and γρ0 channels and which leads to a nontrivial prediction for the manifestation of η(1475) in γγ*(Q
2) collisions is considered. Data on the dependence of the cross section for the reaction γγ*(Q
2) → K[`(K)]pK\bar K\pi on the photon virtuality in the energy range 1.35–1.55 GeV are explained here by the production of an η(1475) resonance in
contrast to their standard interpretation in terms of the f
1(1420) resonance. Experimental verification of the present explanation requires determining the spin-parity of resonance contributions,
R, in the reactions γγ*(Q
2) R → R → K[`(K)]pK\bar K\pi and J/ψ → γR → γ(γρ0, γϕ). 相似文献
17.
Background
Stargazin (γ2) and the closely related γ3, and γ4 transmembrane proteins are part of a family of proteins that may act as both neuronal voltage-dependent calcium channel (VDCC) γ subunits and transmembrane α-amino-3-hydroxy-5-methyl-4-isoxazoleproponinc (AMPA) receptor regulatory proteins (TARPs). In this investigation, we examined the distribution patterns of the stargazin-like proteins γ2, γ3, and γ4 in the human central nervous system (CNS). In addition, we investigated whether human γ2 or γ4 could modulate the electrophysiological properties of a neuronal VDCC complex transiently expressed in Xenopus oocytes. 相似文献18.
Sayipjamal Dulat Bing-Song Zou 《The European Physical Journal A - Hadrons and Nuclei》2005,26(1):125-134
With accumulation of high statistics data at BES and CLEO-c, many new interesting channels can get enough statistics for partial-wave
analysis (PWA). Among them, ψ↦γpˉ,γΛˉ,γΣˉ,γΞˉ channels provide a good place for studying baryon-antibaryon interactions; the double radiative decays ψ↦γγV with V ≡ ρ,ω,φ have a potential to provide information on the flavor content of any meson resonances (R) with positive charge parity
(C = +) and mass above 1 GeV through ψ↦γR↦γγV; ψ(2s)↦γχc0,1,2 with χc0,1,2↦Kˉπ+π- and 2π+2π- decays are good processes to study χcJ charmonium decays. Using the covariant tensor formalism, here we provide theoretical PWA formulae for these channels. 相似文献
19.
Current and upcoming experiments should improve the sensitivity to e
α
→e
β
γ decays by an order of magnitude. This paper assumes that one of the τ→e
β
γ decays is observed, and explores the structure and consequences of the required new flavoured couplings. In simple models
(a low-scale seesaw, leptoquarks) it is shown that the dipole vertex function is proportional to a product of flavoured matrices
from the Lagrangian (a “Jarlskog-like” invariant), provided that the loop particles are weakly coupled to the Higgs. Secondly,
if the dipole vertex function has a hierarchical structure, this might imply that only some of the τ→e
β
γ modes can be observed, due to the “approximate zero” implied by the bound on μ→eγ. The assumptions underlying this potential test of a hierarchical structure are discussed. 相似文献
20.
Swapan Das 《Pramana》2006,66(5):947-952
π0γ invariant mass distribution spectrum has been calculated for the (γ, π0γ) reaction on12C nucleus at 2.5 GeV beam energy. These π0 and γ are assumed to originate due to the decay of vector mesons produced in the photonuclear reaction. The nuclear medium
effect on vector mesons and the effect of π0 rescattering on the π0γ invariant mass spectrum have been investigated 相似文献