Production and decay of xi(c)(0) at BABAR

Using 116.1 fb(-1) of data collected by the BABAR detector, we present an analysis of xi(c)(0) production in B decays and from the cc continuum, with the xi(c)(0) decaying into omega- K+ and xi- pi+ final states. We measure the ratio of branching fractions B(xi(c)(0) --> omega- K+)/B(xi(c)(0) --> xi- pi+) spectrum is measured on and 40 MeV below the upsilon(4S) resonance. From these spectra the branching fraction product B(B --> xi(c)(0)X) x B(xi(c)(0) --> xi- pi+) is measured to be (2.11 +/- 0.19 +/- 0.25) x 10(-4), and the cross-section product sigma(e+ e- --> xi(c)(0)X) x B(xi(c)(0) --> xi- pi+) from the continuum is measured to be (388 +/- 39 +/- 41) fb at a center-of-mass energy of 10.58 GeV.     

Production and decay of269110

In an experiment carried out to identify element 110, we have observed anα-decay chain, that can be unambiguously assigned to²⁶⁹110. In a scries of preexperiments the excitation functions of the fusion reactions⁵⁰Ti +²⁰⁸Pb→²⁵⁸104^* and⁵⁸Fe +²⁰⁸Pb→²⁶⁶108^* were measured with high precision in order to get the optimum projectile energies for the production of these heavy elements. The cross-section maxima of the 1n evaporation channels were observed at excitation energies of 15.6 MeV and 13.4 MeV, respectively. These data result in an optimum excitation energy of 12.3 MeV of the compound nucleus for the production of²⁶⁹110 in the reaction⁶²Ni +²⁰⁸Pb→²⁶⁹110 + 1n. In irradiations at the corresponding beam energy of 311 MeV we have observed a decay chain of 4 subsequent a decays. This can be assigned to the isotope with the mass number 269 of the element 110 on the basis of delayed α-α coincidences. The accurately measured decay data of the daughter isotopes of the elements 108 to 102, obtained in the previous experiments, were used. The isotope²⁶⁹110 decays with a hair-life of (270 _-120 ⁺¹³⁰⁰ ) μs by emission of (11.132±0.020) MeV alpha particles. The production cross-section is (3.3 _-2.7 ^+6.2 ) pb.     

Production and decay of toponiumP-states

Energy levels, production and decay rates of toponiumP-states are calculated and their dependence on different assumptions on the short distance part of the potential is studied. The branching ratio for radiative decays to lower lyingS-states will be very large. Weak decays ofP-states will play an important role for quark masses above 25 GeV. Experimental consequences of our results are discussed.     

关于B-0→K-0π0衰变过程研究

系统地计算B^0→K^0π^0衰变过程的强子矩阵元，它包括领头阶因子化部分，αs修正的硬胶子交换部分和软胶子交换部分．其中软胶子交换部分，无论在量子色动力学(QCD)因子化方法中，还是在微扰QCD中都不能进行计算．用光锥QCD求和规则系统地计算了这部分贡献．并发现在该衰变道中软胶子交换部分与领头阶因子化部分以及αs修正的硬胶子交换部分有相同的数量级，因此不能忽略．最后计算了该衰变过程的分支比，计算结果与实验结果相一致．     

Two-axigluon decay of the Z0

In the realm of the chiral color model, we compute the decay widths of the Z⁰ into two axigluons as a function of the axigluon mass. The results indicate that an axigluon with a mass under 41 GeV should be clearly detectable at LEP or SLC.     

Production and decay of polarized hyperon-antihyperon pairs

Polarized hyperon-antihyperon pairs shed light on various unresolved puzzles in contemporary physics: How the strong interaction confines quarks into hadrons, how accurately the Standard Model describes microcosmos and even why our universe consists of so much more matter than antimatter. Thanks to their weak, parity violating decays, hyperons reveal their spin properties. This can be exploited e.g. the decomposition of the electromagnetic structure of hyperons, precision tests of flavour symmetry and searches for CP violation. At the BESIII experiment at BEPC-II, Beijing, China, hyperon-antihyperon pairs can be produced in abundance. Recently collected large data samples have triggered the development of new methods that provide unprecedented precision and a plethora of new results have emerged. When applied at future high-intensity facilities like PANDA and STCF, precision physics will be taken to a new level which can contribute to the solution to the aforementioned puzzles.     

Production and decay of highly-charged fullerene ions

Highly-charged fullerene ions C ₆₀ ^z+ and C ₇₀ ^z+ with charge states up to z=7 have been produced in an electron impact ion source of a two sector field mass spectrometer by using ion source operating conditions similar to those used in EBIT sources. The stability of these ions was investigated quantitatively in the two field free regions of the mass spectrometer. It was found that besides C₂ evaporation the dominant fission process for ions with charges larger than +2 is the loss of a charged C ₂ ⁺ unit via a super-asymmetric charge separation reaction C ₆₀ ^z+ C ₅₈ ^(z–1)+ +C ₂ ⁺ and C ₇₀ ^z+ C ₆₈ ^(z–1)+ +C ₂ ⁺ , respectively. The most important finding from these studies is that this super-asymmetric dissociation reaction proceeds via a three stage reaction sequence involving an electron transfer reaction at the second stage between a receding C₂ unit and the remaining highly-charged fullerene cage.Based on a lecture given by S. Matt at the 1st Euroconference on Atomic Physics with Stored Highly Charged Ions, Heidelberg, 1995.     

SupersymmetricZ 0 decay into lepton-antilepton and two photinos

Working in a softly broken supersymmetricSU(2)×U(1) standard model with the photino as lightest SUSY-particle \((m_{\bar \gamma } \leqq 10GeV)\) differential and total rates for the decay \(Z^0 \to l^ + l^ - \tilde \gamma \tilde \gamma \) as functions of various parameters of the model are presented. The decay involves intermediate scalar leptons and the total rate strongly depends on their masses. The results indicate that for a scalar lepton mass less than 70GeV this process might still be seen at SLC and CERN LEP I.     

Production and decay of heavy proton drip-line nuclei

Recent work at the NSCL using unusual isotopic beams to study nuclei along the proton drip-line up to A≈95 is presented. The most recent results were obtained by the fragmentation of a ¹⁰⁶Cd beam. Following identification, measurements of the decay properties of such exotic nuclei in specialized measurements of beta-decay half-lives of the stopped ions were undertaken. The results of the studies that focused on the waiting point nuclei ⁶⁵As and ⁶⁹Br in the astrophysical rp-process are also presented. Very recent measurements of the masses of some of these exotic nuclei with a direct time of flight technique are briefly described.     

Exotic meson decay to omegapi0pi-

A partial-wave analysis of the mesons from the reaction pi(-)p --> pi(+)pi(-)pi(-)pi(0)pi(0)p has been performed. The data show b(1)pi decay of the spin-exotic states pi(1)(1600) and pi(1)(2000). Three isovector 2(-+) states were seen in the omegarho(-) decay channel. In addition to the well known pi(2)(1670), signals were also observed for pi(2)(1880) and pi(2)(1970).