Observation of possible production and decay of short-living heavy neutral particles in the SKAT neutrino experiment

In the SKAT bubble chamber neutrino experiment production of a short-living neutral particle with mass (1.4?m?2.5) GeV/c² and lifetime τ≈6×10^?12 s has been detected. The event may be interpreted as production and decay of the heavy lepton M⁰→μ^?+e⁺+ν_e with mass (1.4?m_M⁰?2.1) GeV/c². It might also be the production of a charmed particle D⁰→e⁺+τ^?+ν_e (D⁰→e⁺+π^?+ν_e) with mass 1.4?m_D⁰?2.5) GeV/c² in a non-diagonal neutral current. The probability to interpret the event as other possible processes is very low.     

Testing the Distance-Duality Relation from Hubble,Galaxy Clusters and Type Ia Supernovae Data with Model Independent Methods

In this paper, we perform cosmological-model-independent tests for the distance-duality (DD) relation η(z)=D _L(1+z)^?2/D _A by combining the angular diameter distance D _A(or comoving distances D _c ) with the luminosity distance D _L. The D _A are provided by two galaxy clusters samples compiled by De Filippis et al. (the elliptical β model), Bonamente et al. (the spherical β model), the D _c are obtained from Hubble parameter data and D _L are given from the Union2.1 supernovae (SNe) Ia compilation. We employ two methods, i.e., method A: binning the SNe Ia data within the range Δz=|z?z _SNe|<0.005, and method B: reconstructing the D _L(z) by smoothing the noise of Union2.1 data set over redshift with the Gaussian smoothing function, to obtain D _L associated with the redshits of the observed D _A or D _c. Four parameterizations for η(z), i.e., η(z)=1+η ₀ z, η(z)=1+η ₀ z/(1+z), η(z)=1+η ₀ z/(1+z)² and η(z)=1?η ₀ ln(1+z), are adopted for the DD relation. We find that DD relation is consistent with the present observational data, and the results we obtained are not sensitive to the method and parameterization.     

Charmed particle production in hadron-hadron collisions

In the framework of Quark-Gluon-String Model developed recently in ITEP we calculate spectra of charmed particlesD,D _s,Λ_c,Ξ_c,Ω_c in hadron-hadron collisions taking into account the decays ofS-wave resonances like D^*,D_s ^*,Σ_c,Σ_c ^*,Ξ_c ^*,Ξ_c ^′, and Ω_c ^*. We describe the bulk of the existing data onD, D^*, adΛ _c production in πp andpp collisions and predict the yield of charmed particlesin Σ^?p and Ξ^?p reactions at hyperon beam energies of 340 GeV/c and 600 GeV/c. Because of significant production of baryon resonances our predictions for unfavored fragmentation differ from predictions of other models which do not take resonance production into account.     

Albedo for an inhomogeneous half space

The Albedo is calculated for an inhomogeneous half-space by assuming that the single scattering albedo behaves like c(z) = c_oe^-(z/s). The modified Eddington method is used to obtain the outgoing flux and hence the albedo. Numerical calculations and comparisons with Pomraning et al. and with an improved version of the F_N- method indicate that the approach is reasonably accurate.     

Weak decays of charm and quark masses

We calculate the effects of finite quark masses for the semileptonic and nonleptonic decays of charmed particles. The total lifetimes of charmed particles are not sensitive to the masses of the quarks in the final state. However the semileptonic branching ratios changes considerably. Using conventional constituent quark masses, one expect e.g. B_e(D⁺)≈ 21%. The brancing ratios and lifetimes of the charmed particles are estimated, taking into account the annihilation hypothesis.     

Charmed meson decays and right-handed currents

In the presence of right-handed currents including $\text{(}\text{c}\text{s}\text{)}{}_{\mathrm{<mtext>R</mtext>}}$, it is emphasized that the dominant parity-violating (-conserving) Hamiltonian for nonleptonic decays of charmed hadrons transforms like $\text{45}\text{+}\text{45}{}^1\text{(}\text{20″ +}\text{84}\text{)}$ of SU(4), and leads to distinctive results especially in D⁺ → K_Sπ⁺, F⁺ → μ⁺ν_μ and D⁰ → K^?e⁺ν_e, etc.     

Inclusive electron production from heavy quarks in e+e− annihilation at 34.6 GeV center of mass energy

The production of electrons by bottom and charm hadrons has been studied in e⁺e^? annihilation at 34.6 GeV center of mass energy. It is observed that the b quark fragmentation function is peaked at large values of the scaling variable z with 〈z_b〉 = 0.84^{+0.15 + 0.15}_{?0.10 ? 0.11}. For c quarks 〈z_c〉 = 0.57^{+0.10 + 0.05}_{?0.09 ? 0.06} is observed. A forward-backward charge asymmetry of A = ?0.25 ± 0.22 was measured in b production.     

Energy distributions for charmed hadrons in the QCD cluster model for e+e− annihilation

Predictions of the QCD cluster model for charm production in high energy e⁺e^? annihilation are presented. Details of the model relevant for heavy flavor production are discussed. The model is shown to describe well the shape of the recently measured z-distribution for charged D¹ production at Q = 29 GeV. Reported rates for D¹ production at CESR, PEP, and PETRA are found to be inexplicably high. Substantial Λ_c production is predicted, with the ratio $\text{N(Λ}{}_{\mathrm{<mtext>c</mtext>}}\text{)/N(}\text{D}{}^1\text{)}$ found to be roughly flat in z for z ? 0.5 at high energies. It is argued that the results presented here are rather general predictions of models in which color is locally screened before hadrons actually form.     

Nonleptonic Cabibbo favouredB-decays andCP-asymmetries for charmed final hadron states in Isgur and Wise theory

The Cabibbo allowed non-leptonicB-decays in two hadrons are studied, within the factorization hypothesis, in the framework of Isgur and Wise theory for the matrix elements of the ΔB=?ΔC=±1 weak currents. TheSU(2) _HF symmetry relates |ΔB|=1 to |ΔC|=1 currents, which have been measured in the semileptonic strange decays of charmed particles. By assuming colour screening and allowing forSU(3) invariant contributions from the annihilation terms with charmed final states one is able to comply with the present experimental knowledge. TheCP violating asymmetries in neutralB decays are given charmed final states in terms of theK-M angles. With the central values found for the annihilation parameters there is a destructive (constructive) interference between the direct and annihilation terms in the Cabibbo allowed (doubly forbidden) amplitudes for the decays intoD ⁰(D ^*0)π⁰ and {D ⁰ρ⁰ so that they may be of the same order. This would imply large asymmetries, for which however our present knowledge on the amplitudes does not allow to predict even their sign. We have better confidence in our predictions for the charged final states than the neutral ones and can draw the conclusion that the detection of the corresponding asymmetries requires, at least, 10⁶ tagged neutralB-particles.     

Ising ferromagnet with biquadratic exchange

A spin one Ising system with biquadratic exchange, is investigated, using Green's function technique in random phase approximation (RPA). Transition temperature T_c and <(S^z)²> at T_c, are found to increase with biquadratic exchange parameter α for sc, bcc and fcc lattices. The variation of <(S^z)²> at T_c with α is found to be the same for the above lattices.     

Ground state hyperfine structure of95Mo and97Mo

The hyperfine structure of the ground state 4d ⁵ 5s ⁷ S ₃ of⁹⁵Mo and⁹⁷Mo has been measured by the atomic beam magnetic resonance technique with the following results:⁹⁵Mo:A=?208.582060(10)MHz,B=37.050 (100) kHzC=?30 (10) Hz,D=?3 (3) Hz⁹⁷Mo:A=? 212.980930 (10) MHz,B?69.990(140)kHzC=?5 (10) Hz,D=0 (3) Hz. After application of corrections calculated according to second order perturbation theory, the hyperfine structure constants became:⁹⁵Mo: A_c=?208.582560(290)MHz,B _c =16.920(4300)kHzC _c=?30(270) Hz,D _c =? 3 (50) Hz⁹⁷Mo: A_c=212.981450(300) MHz,B _c =?90.780(4400)kHzC _c=?6(270) Hz,D _c =0 (50) Hz. With the known ratio ofg _I(⁹⁵Mo)/g _I(⁹⁷Mo) [1] a calculation of the hyperfine anomaly yields:₉₅ Δ ₉₇=?0.01009(17)%. The ratio of the uncorrectedB factors isB(⁹⁷Mo)/B(⁹⁵Mo)=?1.8890(47). Because of the relatively large effects of second order hyperfine structure, the ratio of the correctedBfactors differs considerably from the ratio of the uncorrectedB factors. From the correctedB factors the electric quadrupole moments may be evaluated by means of calculated radial integrals [2]. The results are:Q (⁹⁵Mo)=?0.019(12)barns,Q(⁹⁷Mo)=0.102(39)barns.     

Upon the determination of heavy quark fragmentation functions ine + e − annihilation

Results on the fragmentation of heavy quarks from analyses of inclusive lepton production ine ⁺ e ^? annihilation are studied. The use of various fragmentation variables is closely examined and their differences resolved, providing a common basis for comparison of experimental results. The mean value of the fraction of available energy-momentum carried by the primary heavy hadron, defined as $$z = \frac{{(E + p_\parallel )_{hadron} }}{{(E + p)_{quark} }},$$ is determined to be 〈z〉=0.67±0.02±0.02 and 〈z〉_b=0.83±0.01±0.02 for an unknown mixture of charmed and bottom flavoured hadrons respectively. The corresponding values of the parameter? _Q of the Peterson fragmentation function are $$\varepsilon _c = 0.06_{ + 0.02 + 0.02}^{ - 0.01 - 0.01} and \varepsilon _b = 0.06_{ + 0.001 + 0.02}^{ - 0.001 - 0.02} .$$ The ratio? _c /? _b can be approximately related toM _b ² /M _c ² giving a value of 10 _?2?4 ⁺⁴⁺⁵ , in agreement with an expectation of ～10. Measurements of the charged multiplicity of hadronic events containing heavy quark jets are investigated in terms of the mean value ofz.     

Observation of charmed baryon production in νp interactions in BEBC

Two examples of charmed baryon production by neutrinos have been observed in BEBC filled with hydrogen. Both events fit uniquely the reaction νp → μ^?pK^?π⁺π⁺ and thus apparently violate the ΔS = ΔQ rule. None of the appropriate mass combinations is consistent with the mass values of the D⁰ and D⁺ mesons. However, for the mass combinations of the pK^?π⁺ systems, values of (2.285 ± 0.005) GeV and (2.280 ± 0.003) GeV are found for event 1 and 2, respectively. These values agree with the mass of (2.285 ± 0.006) GeV for the Λ_c⁺ charmed baryon determined recently in e⁺e^? collisions at SLAC.     

激光束在漫射表面上的散射(Ⅱ)

首先在前文的基础上,对于用激光根据“光核、光带比”(D₂/D₁)来测定磨削工件表面光洁度的原理加以系统总结,然后按照经验关系R_x=5R_a(对于▽7以上光洁度),确定了表面随机高度的概率密度函数中的衰减系数。对于有限负指数型函数P₁(h)={e^{(-b(|h|/h_m))} 当|h|≤h_m; 0 当|h|>h_m, 定出b=1.23,对于正则型函数P₂(h)=e^{(-a2(h/h_m)2)} 定出a²=2.分别讨论了以上两种函数中h_m的物理意义(皆对应于1/2R_z)将前文中公式加以精确改进后,对P₁(h)和P₂(h)分别计算了D₂/D₁与R_x的关系曲线,即绝对定标曲线。最后还计算了衍射图样半强度宽与R_x的关系曲线。 关键词：     

Spectra of charmed and bottom baryons with hyperfine interaction

Up to now,the excited charmed and bottom baryon states have still not been well studied experimentally or theoretically.In this paper,we predict the mass of ?*b,the only L=0 baryon state which has not been observed,to be 6069.2 Me V.The spectra of charmed and bottom baryons with the orbital angular momentum L = 1 are studied in two popular constituent quark models,the Goldstone boson exchange(GBE) model and the one gluon exchange(OGE) hyperfine interaction model.Inserting the latest experimental data from the "Review of Particle Physics",we find that in the GBE model,there exist some multiplets(Σc(b),Ξ c(b)and ?c(b)) in which the total spin of the three quarks in their lowest energy states is 3/2,but in the OGE model there is no such phenomenon.This is the most important difference between the GBE and OGE models.These results can be tested in the near future.We suggest more efforts to study the excited charmed and bottom baryons both theoretically and experimentally,not only for the abundance of baryon spectra,but also for determining which hyperfine interaction model best describes nature.     

Understanding the masses of the cs̄ states in Regge phenomenology

In the framework of Regge phenomenology, the masses of the charmed states cq̄ (q=u,d,s) lying on the 1³S₁-like trajectories are estimated. The overall agreement between our estimated masses and the recent predictions given using modified quark models by Matsuki et al., Lakhina et al. and Close et al. is good. The masses of the observed charmed states D_s0(2317), D_sJ(2860) and D_sJ(2690)/D_sJ(2700) can reasonably be reproduced in the picture of these charmed states as simple quark–antiquark configurations. We therefore suggest that D_s0(2317) can be identified with the cs̄(1³P₀) states. The possible assignments of the D_sJ(2860) and D_sJ(2690)/D_sJ(2700) are discussed. PACS 11.55.Jy; 14.40.-n     

A monte-carlo/molecular dynamics study of the diffusional recombination kinetics of C(a) + O(a) → CO(g) on Pt(111)

The diffusion constants for C and O adsorbates on Pt(111) surfaces have been calculated with Monte-Carlo/Molecular Dynamics techniques. The diffusion constants are determined to be D_C(T)=(3.4 × 10^?3e^{$\text{?13156}\text{T}$})cm²s^?1 for carbon and D_O(T) = (1.5×10^?3 e^{$\text{?9089}\text{T}$}) cm² s^?1 for oxygen. Using a recently developed diffusion model for surface recombination kinetics an approximate upper bound to the recombination rate constant of C and O on Pt(111) to produce CO_(g) is found to be (9.4×10^?3 e^{$\text{?9089}\text{T}$}) cm² s^?1.     

The microwave spectrum,substitution structure and dipole moment of cyanobutadiyne,HCCCCCN

Cyanobutadiyne (cyanodiacetylene), HCCCCCN, is sufficiently stable at low pressures to permit its rotational spectrum to be studied by microwave spectroscopy. The spectrum consists of a series of R-branch transitions typical of a linear molecule. The transitions with J = 9 to 14 which lie between 26.5 and 40.0 GHz have been measured for the vibrational ground state. Transitions have also been detected in natural abundance for all possible singly substituted ¹³C and ¹⁵N isotopic species. Deuteriated cyanobutadiyne, DCCCCCN, has also been synthesized and its ground state spectrum recorded. These measurements have enabled a complete substitution structure to be derived for the first time for a polyacetylene: r₈(HC_a) = 1.0569 ± 0.001, r₈(C_aC_b) = 1.2087 ± 0.001, r₈(C_bC_c) = 1.3623 ± 0.003, r₈(C_cC_d) = 1.2223 ± 0.004, r₈(C_dC_e) = 1.3636 ± 0.003, $\text{r}{}_8\text{(}\text{C}{}_{\mathrm{e}}\text{}\text{N}\text{) = 1.1606 ± 0.001}\text{A}\text{?}\text{(10}{}^{\mathrm{?10}}\text{m}\text{)}$. The spectroscopic parameters for the ground state are B₀ = 1331.3313 ± 0.001 MHz and D₀ = 0.0257 ± 0.002 KHz. The dipole moment, determined from the Stark effects of the J = 9 and 10 lines, is 4.33 ± 0.03 Debye.