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1.
Summary The GALLEX collaboration is performing an experiment for the detection of neutrinos coming principally from the p-p fusion reaction in the Sun, via the reaction νe+71Ga→71Ge+e. The experiment is running in the Gran Sasso Underground Laboratory of INFN, using as a target 30.3 tons of gallium in the form of 8.13 molar aqueous GaCl3 solution. A report is given of the status of GALLEX after the end of the operations devoted to the removal from the solution of the cosmogenically formed Ge isotopes, completed in the middle of 1991. The experiment is now collecting data on solar neutrinos and the data analysis is in progress. Preliminary results concerning the first year of measurement are presented. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.  相似文献   

2.
P K Kabir 《Pramana》2000,55(1-2):247-251
Inequality of the rates for K 0 → π+ e υ and K 0 → π e + ν transitions, reported by CPLEAR, and an asymmetry in the distribution of the dihedral angle between the π+π and e + e planes in K L → π+π e + e decays, found by KTeV, have been announced as demonstrations of T-noninvariance. These results are critically interpreted and compared as proofs of the failure of reciprocity.  相似文献   

3.
Using the ARGUS detector at the e+e storage ring DORIS II at DESY we have measured the parameters of a charmed strange meson D* s2 + (2573) decaying into D0K+. The mass of this state was found to be (2574.5±3.3±1.6) MeV/c 2. The measured value of its width is (10.4±8.3±3.0) MeV and the product of the production cross section and branching ratio for this channel was determined to be (10.6±4.2 −1.2 +2.3 ) pb. Supported by the German Bundesministerium für Forschung und Technologie, under contract number 054DO51P.  相似文献   

4.
The corrected cross section of the e + e → π+π process measured in the spherical neutral detector experiment at the VEPP-2M e + e collider is presented. The update is necessary due to a flaw in the e + e → π+π and e + e → μ+μ Monte Carlo event generators used previously in data analysis. The text was submitted by the authors in English.  相似文献   

5.
The SU(3) C ⊗ SU(3) L ⊗ U(1) X gauge model with two Higgs triplets (the economical 3-3-1 model) is presented. The minimal Higgs potential is considered in detail, and new Higgs bosons with the mass proportional to the bilepton mass are predicted. In the effective approximation, the charged Higgs bosons H 2 ± are scalar bileptons, while the neutral scalar bosons H 0 and H 1 0 do not carry a lepton number. The couplings of the charged Higgs bosons to leptons and quarks are given. We show that Yukawa couplings of H 2 ± to ordinary leptons and quarks are lepton-number violating. The pair production of H 2 ± at high-energy e + e colliders with the polarization of the e +, e beams is studied in detail. A numerical evaluation shows that, if the Higgs mass is not too heavy, then the reaction can give an observable cross section in future colliders at a high degree of polarization. The reaction e + e H 2 ± W is also examined. We show that the production cross sections of H 2 ± W are very small, much below the pair production of H 2 ± , and, therefore, the associated production of H 2 ± and W is, in general, not expected to lead to easily observable signals in the e + e annihilation. The text was submitted by the authors in English.  相似文献   

6.
The recently discovered narrow peaks (theψ-particles) in e+e system at 3.105 and 3.695 GeV are interpreted as hadrons in a broken SU4 symmetry scheme. A new additional additive quantum number, parachargeZ, is combined with the usual SU3 quantum numbers in the group SU4. Theψ (3.1) is assigned to a near ideally mixed151 multiplet of vector mesons (containing theρ) as theI=Y=0, charge conjugationC=−combination ofZ=±1.members. Theψ (3.7) is assigned correspondingly to another mixed151 multiplet containing theρ′ (1600). The hadronic electromagnetic interactions are modified by the addition of (non-minimal) anomalous pieces that can changeZ. The decays of theψ-particles are discussed. New enlarged SU4 multiplets of other hadrons are proposed. Tests of our scheme are put forward. The most crucial test will be the observation of two rather broad resonances in e+ e collisions with masses around 4.2 GeV and 5.1 GeV. Another prediction is the presence of energetic photons in the decays of theψ-particles. Important results concerning the recently observed phenomena in the process e+e→hadrons follow in this scheme.  相似文献   

7.
N. N. Achasov 《JETP Letters》1996,63(8):601-606
It is shown that BR b1(1 P)→e + e )≃3.3· 10−7 and BR c1(1 P)→e + e )≃10−8. This gives realistic possibilities for searching for the production of χ b1(1 P) and ξ c1(1 P) states in e + e collisions, even on the present-day colliders, to say nothing of b and c-τ factories. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 569–574 (25 April 1996)  相似文献   

8.
We determined and tried to understand the spectroscopic and structural properties of small LiAr and LiAr2 molecules within a simple model considering LiAr as a result of interaction between a valence electron and a LiAr+ molecular ion. Potential energy curves, spectroscopic constants, and vibrational levels corresponding to the Li(2s, 2p, 3s, and 3p)+Ar dissociation are reported for the LiAr molecule. The depth of the potential well for the X 2Σ+ ground state is found to be 50 cm−1 (the corresponding experimental value is (42.5±1.2) cm1 [1]). R e is determined to be 9.36 a.u. (the experimental value is 9.24 a.u.). For the first excited state A, R e = 4.97 a.u. and D e = 993cm −1 (the corresponding experimental values are 4.68 a.u. and (925−40) cm−1, respectively [1]). The spacing between the vibrational levels for the ground and first excited states is in very good agreement with the experiment. For the ground state, the difference between our results and the data of the most recent experiment is about 1 cm−1. The model has been extended to study the LiAr2 molecule in two forms (linear and triangular). We have determined the potential energy surfaces of the states dissociating to Li(2s, 2p)+Ar2 and thus found the triangular form to be more stable as compared to the linear one. We have also calculated the transition energy between the ground state and first excited states of this molecule. The emission spectrum of the Li(2s)+Ar2→Li(2p)+Ar2 transition in both forms redshifts as compared to the Li(2s)→Li(2p) atomic transition.  相似文献   

9.
We present the first energy and angle resolved measurements of e+e-pairs emitted from heavy nuclei (Z≥ 40) at rest by internal pair conversion (IPC) of transitions with energies of less than 2 MeV as well as recent theoretical results using the DWBA method, which takes full account of relativistic effects, magnetic substates and finite size of the nucleus. The 1.76 MeV E0 transition in 90Zr (90Sr source) and the 1.77 MeV M1 transition in 207Pb (207Bi source) have been investigated experimentally using the essentially improved setup at the double-ORANGE β-spectrometer of GSI. The measurements prove the capability of the setup to cleanly identify the IPC pairs in the presence of five orders of magnitude higher β and γ background from the same source and to yield essentially background-free sum spectra despite the large background. Using the ability of the ORANGE setup to directly determine the opening angle of the e+e–pairs (Θe+e−), the angular correlation of the emitted pairs was measured within the range covered experimentally (40°≤Θe+e−≤ 180°). In the 90Zr case the correlation could be deduced for a wide range of energy differences E Δ of the pairs (−530 keV ≤E Δ≤ 530 keV). The 90Zr results are in good agreement with recent theory. The angular correlation deduced for the M1 transition in 207Pb is in strong disagreement with theoretical predictions derived within the Born approximation and shows almost isotropic character. This is again in agreement with the new theoretical results. Received: 22 April 1997 / Revised version: 16 December 1997  相似文献   

10.
Laser-induced breakdown spectroscopy (LIBS) in germane (GeH4), initially at room temperature and pressures ranging from 2 to 10 kPa, was studied using a high-power transverse excitation atmospheric (TEA) CO2 laser (λ=10.653 μm, τ FWHM=64 ns and power densities ranging from 0.28 to 5.52 GW cm−2). The strong emission spectrum of the generated plasma is mainly due to electronic relaxation of excited Ge, H and ionic fragments Ge+, Ge2+ and Ge3+. The weak emission is due to molecular bands of H2. Excitation temperatures of 8100±300 K and 23,500±2500 K were estimated by Ge atomic and Ge+ singly ionized lines, respectively. Electron number densities of the order of (0.7–6.2)×1017 cm−3 were deduced from the Stark broadening of several atomic Ge lines. The characteristics of the spectral emission intensities from different species have been investigated as functions of the germane pressure and laser irradiance. Optical breakdown threshold intensities in germane at 10.653 μm have been determined. The mechanism of initiation of the laser-induced plasma in germane has been analyzed.  相似文献   

11.
In the framework of the chiral perturbation theory we obtain the phenomenological relations between decay branches of rare radiative kaon to pion and leptons K + → π+ l + l and K S 0 → π0 l + l and meson form factors. The comparison of these results with the present-day experimental data shows us that the ChPT relations for a charge kaon can determine meson form factors from already measured decay rates at high precision level. However, in the case of the neutral kaon decays K 0 → π0 e + e +μ) the form factor data are known to a higher precision than data on the differential rates of radiative kaon decay K 0 π0 e + e +μ).  相似文献   

12.
Planar channeling data ofμ +-decay positrons in various semiconductors are reported. Together with the extensive spectroscopic data supplied by transverse μSR, the location of the different states of the hydrogen pseudo-isotopeμ + e (muonium) can be identified by means of planar simulations. In high purity silicon as well as in gallium arsenide a thermally activated site transition is observed which can be assigned to a transition between different muonium states.  相似文献   

13.
We study the decay K +π + π 0 e + e , currently under analysis by the NA62 Collaboration at CERN. In particular, we provide a detailed analysis of the Dalitz plot for the long-distance, γ -mediated, contributions (Bremsstrahlung, direct emission and its interference). We also examine a set of asymmetries to isolate genuine short-distance effects. While we show that charge asymmetries are not required to test short distances, they provide the best environment for its detection. This constitutes by itself a strong motivation for NA62 to study K decays in the future. We therefore provide a detailed study of different charge asymmetries and the corresponding estimated signals. Whenever possible, we make contact with the related processes K +π + π 0 γ and K L π + π e + e and discuss the advantages of K +π + π 0 e + e over them.  相似文献   

14.
Using the data of about 33 pb-1 collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we have studied the exclusive semileptonic decays D+→K-π+e+νe, D0→K̄0π-e+νe, D+→K̄*0e+νe and D0→K*-e+νe. The absolute branching fractions for the decays are measured to be BF(D+→K-π+e+νe)=(3.50±0.75±0.27)%, BF(D0→K̄0π-e+νe)=(2.61±1.04±0.28)%, BF(D+→K̄*0e+νe)=(5.06±1.21±0.40)% and BF(D0→K*-e+νe)=(2.87±1.48±0.39)%. The ratio of the vector to pseudoscalar semileptonic decay rates Γ(D+→K̄*0e+νe)/Γ(D+→K̄0e+νe) is determined to be 0.57±0.17±0.02.  相似文献   

15.
The oscillator representation is applied to calculate the energy spectrum of three-body Coulomb systems with total angular momentum J. For three-body Coulomb systems with J = 1 and arbitrary masses the region of stability is determined. For the systems (A + A e ), (pe C +), (pB e ), and (D + e e +), the values of the critical masses of the particles A, B, C, and D are obtained as m A = 2.22m e , m B = 1.49m e , m C = 2.11m e and m D = 4.15m e . Received November 6, 1995; received December 4, 1995; accepted for publication January 22, 1996  相似文献   

16.
The hadronic events from the e  +  e  −  annihilation data at the centre-of-mass energies ranging from 60 to 197 GeV were studied. The AMY and OPAL Collaborations offered a unique opportunity to test QCD by measuring the energy dependence of different observables. The coupling constant, α s, was measured by two different methods: first by employing the three-jet observables. Combining all the data, the value of as at next-to-next leading order (NNLO) was determined to be 0.117 ± 0.004(hard) ± 0.006(theo). Secondly, from the event-shape distributions, the strong coupling constant, α s, was extracted at NNLO and it’s evaluation was tested with the energy scale. The results were consistent with the running of α s, expected from QCD predictions. Averaging over different observables, α s was determined to be 0.115 ± 0.007(hard) ± 0.003(theo).  相似文献   

17.
The α-decay energy and halflife of 195mAt were determined to be 6960±20 keV and 385+69 −51 ms respectively, on the basis of genetic correlations in the 169Tm(36Ar, α6n)195At reaction, while those of 195gAt measured simultaneously were 7105±30 keV and 146+21 −17 ms respectively, reconfirming the previously reported values. A new isotope 199Fr was also produced and identified in the same way in the 169Tm(36Ar, 6n)199Fr reaction, yielding Eα= 7655±40 keV and T1/2= 12+10 −4 ms. Received: 26 March 1999  相似文献   

18.
The lifetimes of a negative muon in the isotopes 132Xe and 40Ar in the solid phase are measured. The lifetime of μ in the 1s state of the isotope 132Xe is τ(132Xe)=101.7±1.7 ns, which corresponds to a total nuclear capture rate Λc(132Xe)=9.4±0.2 μs−1. The lifetime of μ in the isotope 40Ar, viz., τ (40Ar)=568±6 ns, corresponding to a capture rate Λc(40Ar)=1.31±0.01 μs−1, is obtained to several times better accuracy as compared to previously published results. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 3, 181–183 (10 February 1999)  相似文献   

19.
CP-violating rate asymmetry can be generated in a process only if its amplitude possesses an absorptive part. It is pointed out that such an absorptive part can be provided ine + e annihilation by the presence of aZ(Z′) resonance of non-zero width. The CP asymmetry in the process , wherel i are charged leptons, is discussed in several models. In a specific two-Z model, large and observable CP asymmetry ine + e τ + e (τ e +) is shown to be possible at LEP/SLC energies.  相似文献   

20.
The integrated intensities of a few bands in the vibrational structure of the astrophysically significant ‘orange’ system of the molecule yttrium monoxide, have been measured experimentally by the technique of photographic photometry. The effective vibrational temperatures of the source are found to be 2402±180 K and 2901±230 K for the subsystemsA 2Π3/2X 2 Σ + andA 2Π1/2X 2 Σ + respectively.  相似文献   

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