Projectile break-up with two outgoing intermediate-mass fragments in 26 AMeV32S+197Au

Correlations between two intermediate-mass fragments resulting from 840 MeV³²S projectiles interacting with¹⁹⁷Au were measured. The angular correlations and absolute two-fragment cross sections agree with predictions of a semi-microscopic model for direct dynamic projectile break-up. This suggests a predominantly direct mechanism for the production of intermediate-mass fragment pairs. It is argued that the intensity of such a channel which, compared to decays yieldingα particles, is much larger than observed for the sequential decay of corresponding primary excited nuclei, supports the direct-break-up interpretation. The model mechanism yields also strongly damped projectile fragments of intermediate mass.     

Emission of intermediate-mass fragments in the interaction of 16O with 59Co, 93Nb and 197Au

In this paper we study the emission of ⁸Be_gs, B and N fragments in the interaction of ¹⁶O ions with ⁵⁹Co, ⁹³Nb and ¹⁹⁷Au at incident energies varying from 6 to 25 MeV/nucleon. The spectra of these fragments, as well as those of C fragments studied in a previous paper, are dominated at forward angles by a component originating from break-up of ¹⁶O. At the higher incident energies break-up occurs after quite a sizeable projectile energy loss. Another mechanism which dominates at large emission angles, favours the emission of low-energy fragments and is attributed to the coalescence of nucleons during the cascade of nucleon-nucleon interactions by means of which the excited nuclei produced in the primary two-ion interaction thermalize. Received: 21 January 2003 / Accepted: 27 March 2003 / Published online: 5 June 2003     

超亮X射线源与中等质量黑洞

超亮X射线源是在邻近星系中发现的一类特殊的辐射X射线的天体.它们类似银河系中的黑洞双星,但却具有更高的亮度,因此可能包含更高质量的黑洞,即所谓的中等质量黑洞.中等质量黑洞并不像恒星级质量黑洞一样,可以是大质量恒星演化末期核塌缩的产物,因此在天体物理中具有重要意义.文章描述了超亮X射线源的一些基本性质,综述了近年来对这些源多波段观测的重要结果,以及这些结果对这些天体本质的暗示.     

The infrared spectral features of circumstellar envelope of evolved low- and intermediate-mass stars

The circumstellar envelope of evolved stars of low- and intermediate-mass is an important site for dust formation. In comparison with the interstellar medium, they have more types of organics and different types of inorganics. Various infrared features in the circumstellar envelope can reveal the composition and abundance of dust, as well as the chemical and physical conditions of the circumstellar shell. Infrared features and their carriers are different in the C-rich or O-rich environment, and the mixed-environment where the C-rich and O-rich circumstellar materials co-exist. The C-rich sources exhibit a series of spectral features which are attributed to organic molecules. They also show two prominent features at 21 μm and 30 μm which emit a large portion of infrared radiation. The O-rich sources exhibit the strong 9.7 μm and 18 μm features attributed to the Si-O bending and O-Si-O stretching modes of amorphous silicate dust. With the ISO/SWS spectrometer, about 50 narrow bands are identified with the crystalline silicate grains, mainly forsterite and enstatite. In addition, a series of features, at 13 μm, 16.8 μm, 19.5 μm and 31.8 μm, appearing to be correlated with each other, are attributed to oxides. Some objects simultaneously show the C-rich and O-rich features, e.g. some C-rich sources have silicate features. There is no well-accepted interpretation for such mixed appearance, though a binary model is suggested. Supported by the Program for New Century Excellent Talents in University of China (Grant No. NCET-05-0144), the Doctoral Fund of Ministry of Education of China (Grant No. 20060027013), and the National Natural Science Foundation of China (Grant No. 10473003)     

太阳邻域的小型及微型暗晕和中等质量黑洞

银河系中可能存在10^3--10^4个中等质量的黑洞（10^2--10^3M⊙）和10^3个小型暗晕（质量为10^6M⊙）或10^15个微型暗晕（质量10^-6M⊙）。离我们最近的微小暗晕和黑洞可能只有0．3—3000光年．如果暗物质是可以自湮灭的中超子（即最轻的中性超对称粒子，neutralino），这些子结构所产生的高能γ射线就有希望被下一代γ射线探测器（如GLAST）探测到。     

Multiplicity correlations of intermediate-mass fragments with pions and fast protons in <Superscript>12</Superscript>C + <Superscript>197</Superscript>Au

Low-energy ( MeV) from ¹² C + ¹⁹⁷ Au collisions at incident energies from 300 to 1800 MeV per nucleon were detected with the Si-Si(Li)-CsI(Tl) calibration telescopes of the INDRA multidetector. The inclusive angular distributions are approximately isotropic, consistent with multiple rescattering in the target spectator. The multiplicity correlations of the low-energy pions and of energetic protons ( MeV) with intermediate-mass fragments were determined from the measured coincidence data. The deduced correlation functions for inclusive event samples reflect the strong correlations evident from the common impact parameter dependence of the considered multiplicities. For narrow impact parameter bins (based on charged-particle multiplicity), the correlation functions are close to unity and do not indicate strong additional correlations. Only for pions at high particle multiplicities (central collisions) a weak anticorrelation is observed, probably due to a limited competition between these emissions. Overall, the results are consistent with the equilibrium assumption made in statistical multifragmentation scenarios. Predictions obtained with intranuclear-cascade models coupled to the Statistical Multifragmentation Model are in good agreement with the experimental data.Received: 9 December 2003, Revised: 18 February 2004, Published online: 31 August 2004PACS: 25.70.Mn Projectile and target fragmentation - 25.70.Pq Multifragment emission and correlations - 25.75.Dw Particle and resonance production - 25.75.Gz Particle correlations     

太阳邻域的小型及微型暗晕和中等质量黑洞

银河系中可能存在103—104个中等质量的黑洞（102—103 M⊙）和103个小型暗晕(质量为106M⊙)或1015个微型暗晕（质量10－6M⊙）.离我们最近的微小暗晕和黑洞可能只有0.3—3000光年. 如果暗物质是可以自湮灭的中超子（即最轻的中性超对称粒子,neutralino）,这些子结构所产生的高能γ射线就有希望被下一代γ射线探测器（如GLAST）探测到.     

Associated production of intermediate-mass Higgs particle with a large-pT jet at SSC energy

We calculate the higher-order Higgs particle production process gg→gH for a large top-quark mass (2m_t > m_H). We compute the resulting associated cross section for intermediate-mass Higgs particle (m_W<m_H<2m_W) at SSC, followed by its dominant decay mode into a bottom-quark pair. At large p_T the cross section becomes comparable to that of the QCD background while remaining sufficiently large for detection at SSC.     

Role of h-->etaeta in intermediate-mass Higgs boson searches at the Large Hadron Collider

The dominance of the h-->etaeta decay mode for the intermediate-mass Higgs boson is highly motivated to solve the little hierarchy problem and to ease the tension with the precision data. However, the discovery modes for m(h) approximately <150 GeV, h-->gammagamma, and W/Zh-->(lnu/ll)(bb), will be substantially affected. In this Letter, we show that h-->etaeta-->4b is complementary and we can use this decay mode to detect the intermediate Higgs boson at the LHC, via Wh and Zh production. Requiring at least one charged lepton and 4B tags in the final state, we can identify a clean Higgs boson signal for m(h) approximately <150 GeV with a high significance and with a full Higgs mass reconstruction. We use the next-to-minimal supersymmetric standard model and the simplest little Higgs model for illustration.     

Six-fermion calculation of intermediate-mass Higgs boson production at future {e^+ e^-} colliders

The production of an intermediate-mass Higgs boson in processes of the kind fermions at the energies of future linear colliders is studied. The recently developed and fully automatic algorithm/code ALPHA is used to compute the tree-level scattering amplitudes for the reactions . The code has been interfaced with the Monte Carlo program HIGGSPV/WWGENPV, properly adapted to 6-fermion production, in order to provide realistic results, both in the form of cross sections and event samples at the partonic level. Phenomenological results, that incorporate the effects of initial-state radiation and beamstrahlung, are shown and commented, emphasizing the potentials of full six-fermion calculations for precise background evaluation as well as for detailed studies of the fundamental properties of the Higgs particle. Received: 22 May 1997 / Published online: 20 February 1998