In-flight (K~-,N) Reactions for Study of Kaon-nucleus Interaction

We would like to emphasize that the in-flight (K~-,N) reactions are particularly useful for the study of the K-nucleus interaction.Since the reaction mechanism is well known,there is little ambiguity to derive the K-nucleus interaction from the measured missing mass spectra.Here we discuss the missing mass spectra of the (K~-,N) reactions on the ~(12)C and ~(16)O targets.The spectra show an appreciable amount of strength below the K-nucleus threshold which indicates that the K-nuclear potential is strongly attractive.Comparison of the missing mass spectra with theoretical calculations leads to a potential depth of around-190 MeV for the ~(12)C(K~-,n) reaction.A less deep potential of around-160 MeV reproduces well that of the ~(12)C(K~-,p) reaction.The difference can be due to isospin dependence of the interaction.Our data show that the K-nucleus potential is very deep to realize kaon condensation in the core of neutron stars.     

What can we learn from the decay of NX(1625) in the molecule picture?

Considering two assumptions on the molecular state, i.e. the S-wave Λ̄–K^- and S-wave Σ̄⁰–K^- molecular states, we study the possible decays of N̄_X(1625) that include N̄_X(1625)→K^-Λ̄,π⁰p̄,ηp̄,π^-n̄. Our results indicate that (1) if N̄_X(1625) is the Λ̄–K^- molecular state, K^-Λ̄ is the main decay mode of N̄_X(1625), and the branching ratios of the rest decay modes are tiny; (2) if N̄_X(1625) is the Σ̄⁰–K^- molecular state, the branching ratio of N̄_X(1625)→K^-Λ̄ is one or two orders smaller than that of N̄_X(1625)→π⁰p̄,ηp̄,π^-n̄. Thus the search for N̄_X(1625)→π⁰p̄,ηp̄,π^-n̄ will be helpful to shed light on the nature of N̄_X(1625). PACS 13.30.Eg, 13.75.Jz     

Study about Light Hypernuclei and YN Interaction Based on Chiral SU(3) Quark Model

In terms of the YN interaction based on the chiral SU(3) quark model,the spectra of light hypernuclei 4ΛH,4ΛHe and 5ΛHe are calculated. The result shows that the effective local ΛN potential,as an approximation,cannot offer a reasonable explanation of the empirical data, while the non-local ΛN potential,also as an approximation,can provide a reasonable range of the binding energy of 5ΛHe and correct ordering of the energy levers of 4ΛH,4ΛHe. This indicates that the non-local character of the effective YN interaction plays an important role in binding behavior. The upper bounds and lower bounds of energy levels are given by employing two sets of model parameters in the calculation. Thus,the experimental data of hypernuclei can provide more information as the constraints of model. In the present stage,YN interaction(no matter phenomenology of theoretical interaction) cannot be finalized due to lack of experimental data. Utilizing experimental data,it is possible to optimize model parameters in the theoretical studies of YN interaction.     

X(3872) and Bound State Problem of D~0(D)*~0((D)~0D*~0)

We have performed a dynamical calculation of the bound state problem of D~0(D)~(*0) by considering the pion and sigma meson exchange potential.Our preliminary analysis disfavors the molecular interpretation of X(3872) if we use the experimental D~* Dπ coupling constant g=0.59 and a reasonable cutoff around 1 GeV,which is the typical hadronic scale.In contrast,there probably exists a loosely bound S-wave B (-B)~* molecular state.Such a molecular state would be rather stable since its dominant decay mode is the radiative decay through B~*→Bγ.     

Luminescence quenching of cyclometalated Pt(II) complexes by halogenide ions

The luminescence quenching of [Pt(CΛN)En]ClO₄ complexes ((CΛN)^? = ppy^?, tpy^?, and bt^? are deprotonated forms of 2-phenylpyridine, 2(2′-thienyl(pyridine), and 2-phenylbenzothiazole, respectively; En is ethylenediamine) by halogenide ions (Hal^? = Cl^?, Br^?, I^?) in ethanol solutions is studied. It is shown that the quenching has a dynamic character and its bimolecular rate constants are consistent with the enhancement of nonradiative deactivation of the excited state of {[Pt(CΛN)En]*...Hal} collision complexes with increasing spin-orbit interaction constant of the halogen.     

Strange (K) nuclear systems (S=-1)

Λ(1405) is considered as a superposition of two resonances instead of a simple bound state of the kaon and proton. Within the framework of the Brueckner-Hartree-Fock(BHF) theory, we have investigated the K nuclear systems (S=-1), especially K- pp and K- pnn(T=1). The binding energy BK-is 23 MeV (3 MeV) and the width Γ is 62 MeV (56 MeV) for K-pp(K-pnn(T=1)).     

正反重强子对构成的强子分子态能谱

近二十年来,世界上众多高能物理实验发现了大量超出传统夸克模型的共振结构。为了理解 这些性质奇特的共振结构,科学家们提出了很多方法和模型。其中,因为实验上发现的这些奇特态 大多处在一对强子阈值附近,强子分子态的观点得到了很多关注。本文我们将以粲{反粲强子对为例 来探究哪些系统可以形成分子态,进而给出粲{反粲强子分子态的能谱。我们考虑了所有由 S 波粲 介子、粲重子以及窄的 P 波粲介子构成的粲{反粲强子对。我们假定它们之间的相互作用由介子交 换主导,在最低阶近似下可简化为常数。通过求解常数相互作用的 Bethe---Salpeter 方程,我们可以 找到振幅的极点进而确定该系统分子态的质量。最终我们发现,那些通过轻矢量介子交换在阈值附 近产生吸引力的系统,会存在一个靠近阈值的极点。不同的系统,由于其相互作用强度不同,极点 可能会处于能量复平面的第一黎曼面或者第二黎曼面,分别对应于束缚态或者虚态。我们总共发现 了 229 个强子分子态。很多实验上发现的那些位于粲---反粲强子对阈值附近的共振结构可以很好地 与我们的结果吻合。另外,我们需要强调所预言的一个 ΛcΛc  分子态,这个态可以很好地解释北京正负电子谱仪 (BESIII) 上测量的数据。     

FT Infrared Spectra of FCN from 1200 to 1800 cm(-1) and from 2800 to 7000 cm(-1) and Global Rovibrational Analysis of the Main Isotopomers

We measured the FT spectrum of natural FCN from 1200 to 1800 cm(-1) and from 2800 to 7000 cm(-1) with a near Doppler resolution and a line-position accuracy between 1 and 8 x 10(-4) cm(-1). Lines were assigned to 91 different bands (75 of (19)F(12)C(14)N, 11 of (19)F(13)C(14)N, and 5 of (19)F(12)C(15)N), of which no more than five had been previously reported at lower resolution. From band-by-band analyses we deduced effective state parameters. As those results complete the study of the Fourier transform spectra of natural cyanogen fluoride from 1200 to 7000 cm(-1), global rovibrational analyses of (19)F(12)C(14)N, (19)F(13)C(14)N, and (19)F(12)C(15)N have been performed on the basis of all the available experimental data about their rovibrational energies. We have so determined sets of about 100 molecular parameters for each isotopomer, and a statistical agreement was obtained. A labeling of the vibrational states is proposed on the basis of the eigenvector coefficients. Copyright 2000 Academic Press.     

New measurement of the beta decay rate of the16N(0−)-16O(0+) transition

The beta decay rate of the¹⁶N(0^?; 120keV) →¹⁶O(0⁺, G.S.) transition has been remeasured. Our result (Λ _β =0.48±0.024 s^?1) is in excellent agreement with a previous measurement but strongly disagrees with another experimental value. The two agreeing results provide an experimental verification of the importance of meson exchange currents in 0⁺-0^? weak transitions. A value ofg _p/g _A～11–12 can be inferred from the correspondingΛ _μ rate.     

The πN→ηN Reactions near Threshold and η-N Scatterings

The N^*(1535) model is proposed for pionic η- production reactions.The πN→ηN reaction cross sections near threshold and the S-wave η-N scattering length are calculated and compared with the experimental data and other theoretical calculations.     

Λ polarization in12C(π −,Λ) reactions atp π=4 GeV/c

We study theΛ formation cross sections andΛ polarizations based on the Regge pole amplitudes in theπ ^?+¹²C→Λ+X(inclusive) reactions and the exclusive kaon channel reactions atp _π =4 GeV/c. We found that the experimental data of inclusive cross sections can be reproduced qualitatively well by our calculation. As for the polarization, we have the experimental data that were reported by two different groups, although they have opposite sign and different magnitudes. Our calculated results do not agree with either set of data. We show that the sign of polarization is sensitive to the outgoingΛ kinetic energy in the inclusive reactions and to the outgoing kaon angle in the exclusive kaon channel reactions.     

On Possible S-Wave Bound States for an N\bar{N} System Within a Constituent Quark Model

We try to apply a constituent quark model (a variety chiral constituent quark model) and the resonating group approach for the multi-quark problems to compute the effective potential between the N\bar{N} in S-wave (the quarks in the nucleons N and \bar{N}, and the two nucleons relatively as well, are in S wave) so as to see the possibility if there may be a tight bound state of six quarks as indicated by a strong enhancement at threshold of p\bar{p} in J/ψ and B decays. The effective potential which we obtain in terms of the model and approach shows if the experimental enhancement is really caused by a tight S-wave bound state of six quarks, then the quantum number of the bound state is very likely to be I=1, J^PC=0^-+.     

K-p scattering and hyperon excitations in a chiral quark model

A chiral quark-model approach is employed to study theˉ KN scattering at low energies.The processes of Kˉp →Σ 0 π 0,Λπ 0 andˉ K 0 n at P K 800 MeV/c (i.e.the center mass energy W 1.7 GeV) are investigated.The analysis shows that the Λ(1405)S 01 dominates the processes Kˉp →Σ 0 π 0,ˉ K 0 n in the energy region considered here.Around P K 400 MeV/c,the Λ(1520)D 03 is responsible for a strong resonant peak in the cross section of Kˉp →Σ 0 π 0 andˉ K 0 n.To reproduce the data,an unexpectedly large coupling for Λ(1520)D 03 to KN is needed.In contrast,the coupling for Λ(1670)S 01 to KN appears to be weak,which could be due to configuration mixings between Λ(1405)S 01 and Λ(1670)S 01 .By analyzing Kˉ p →Λπ 0,evidences for two low mass S-wave states,Σ(1480)S 11 and Σ(1560)S 11,seem to be available.With these two states,the reaction Kˉp →ˉ K 0 n can also be described well.However,it is difficult to understand the low masses of Σ(1480)S 11 and Σ(1560)S 11 .The s-channel amplitudes for Kˉp →Λπ 0 are also larger than the naive quark model expectations.The non-resonant background contributions,i.e.t-channel and/or u-channel,also play important roles in the explanation of the angular distributions due to amplitude interferences.     

Is X(3872) really a molecular state?

After taking into account both the pion and sigma meson exchange potential, we have performed a dynamical calculation of the D⁰D̄^*0 system. The σ meson exchange potential is repulsive from heavy quark symmetry and numerically important for a loosely bound system. Our analysis disfavors the interpretation of X(3872) as a loosely bound molecular state if we use the experimental D^*Dπ coupling constant g=0.59 and a reasonable cutoff around 1 GeV, which is the typical hadronic scale. Bound state solutions with negative eigenvalues for the DD̄^* system exist only with either a very large coupling constant (twice the experimental value) or a large cutoff (Λ ∼ 6 GeV or β ∼ 6 GeV²). In contrast, there probably exists a loosely bound S-wave BB̄^* molecular state. Once produced, such a molecular state would be rather stable, since its dominant decay mode is the radiative decay through B^*→Bγ. Experimental search of these states will be very interesting. PACS  12.39.Pn; 12.40.Yx; 13.75.Lb     

On the Nature of f0(400-1200)

We discuss about the nature of f₀(400-1200) which we decompose into three parts, i.e., t-channel ρ meson and f₂(1270) meson exchange plus an additional s-channel resonance f₀(X). Below 1.2GeV of ππ invariant mass, t-channel ρ meson exchange can explain the I=2 ππ S-wave scattering very well. However, the f₂(1270) meson exchange must be considered for the ππ invariant mass above 1.2GeV. With the t-channel ρ meson and f₂(1270) meson exchange fixed by the isotensor ππ→ππ S-wave scattering, we re-fit the CERN-Mülich(CM) data on ππ scattering to get parameters for the f₀(X). We find that it is necessary to introduce a broad 0⁺⁺ resonance with a pole about 1.6-1.7GeV.     

Pressure Lineshift and Broadening Coefficients in the 2nu(3) Band of (16)O(12)C(32)S

In this study we report the first measurements of the pressure-induced lineshift coefficients due to Ar, He, O(2), and N(2) for 22 rovibrational lines from P(53) to R(53), belonging to the 2nu(3) band of (16)O(12)C(32)S at 4100 cm(-1). The lineshift results were obtained from the simultaneous record of the pressure-broadened and pure low-pressure OCS lines, using a tunable difference-frequency laser spectrometer. For four lines of the 2nu(3) band we also report Ar-, He-, O(2)-, and N(2)-broadening coefficients by fitting Voigt and Rautian profiles to the measured shapes of these lines. The broadening and shift coefficients are compared to the results of theoretical calculations based on the semiclassical Robert-Bonamy formalism and two different isotropic and anisotropic intermolecular potentials. For OCS-Ar we also consider the Smith-Giraud-Cooper model including all orders of the interaction within the peaking approximation. In all cases, the calculated broadening coefficients are in reasonable agreement with the experimental data. By considering adjustable parameters for the vibrational dependence of the isotropic potential, the general trends of the lineshifts with J can be roughly predicted, except at low J values where an asymmetry behavior for P and R branches is generally observed. Copyright 2000 Academic Press.     

Absolute Line Intensities and Self-Broadening Coefficients in the nu(1) Band of (35)Cl(12)C(14)N

The self-broadening coefficients and the intensities of 29 lines in the nu(1) band of cyanogen chloride ((35)Cl(12)C(14)N) have been measured at high resolution in the range 699-736 cm(-1), using a tunable diode-laser spectrometer. The collisional widths and most of the intensities are obtained by fitting Voigt and Rautian profiles to the measured shapes of the lines. From the analysis of the line intensities we determine the absolute strength as well as the Herman-Wallis factors for the nu(1) band. A semiclassical calculation of the self-broadening coefficients, performed by considering the main electrostatic interactions only, has provided larger results than the experimental data. Copyright 2001 Academic Press.     

在重离子碰撞中的K－介子吸收对其产生的影响

用RBUU方法研究了中高能重离子碰撞中K^－介子产额及谱的情况.我们发现K⁺/K^－产额比是与核系统大小相关的,这种相关性与K^－介子在核介质中所受的吸收效应有关.还研究了在三种不同核系统中的K^－平均吸收路程,发现K^－平均吸收路程在轻核系统中与在中、重核系统中存在较大的差别,从而定量地解释了这种K⁺/K^－比与核系统的相关性.研究结果给出了核介质对K^－介子的吸收程度还与不同反应道的贡献有关,这是导致Bπ→K^－X道在核系统,特别是在轻、中量核系统中起重要作用的一个重要原因.     

高位K2(1Λg) 与基态原子的碰撞转移

在K原子密度约为0.5～5×1016cm-3的样品池中,脉冲激光710 nm线双光子激发K2基态到高位1Λg态,研究了K2(1Λg)+ K(4S)碰撞转移过程.K原子密度由测量KD2线蓝翼对白光的吸收得到.测量不同K密度下1Λg态发射的时间分辨荧光强度,它是一条指数衰减曲线,由此得到1Λg态的有效寿命,从描绘出的有效寿命倒数与K原子密度关系直线的斜率得到1Λg态总的碰撞猝灭截面为(2.1±0.2)×10-14cm2,从截距得到的辐射寿命为(22±2)ns.测量了K的6S →4P3/2和4D→4P3/2在不同K密度下的时间积分荧光强度,得到了K2(1Λg)+K→K2(11∑ +g)+K(6S,4D)碰撞转移截面为(1.5±0.3)×10-15cm2(对转移到6S)和(8.5±3.0)×10-15cm2(对转移到4D).     

Calculation of A Λp invariant-mass distribution in the reaction K−d → π−Λp

The Λp invariant-mass distribution in the reaction K^?d → π^?Λp, which is observed Cline et al., has two enhancements: just below the ΣN threshold and just above the ΛN threshold. We have calculated the Λp invariant mass distribution with the two-channel formalism. It has been well discussed in our previous paper that the enhancement just below the ΣN threshold is mainly due to a Λp resonance. In our previous paper, we have interpreted the enhancement just above the ΛN threshold as the two-channel final state interaction or a Λp final state interaction associated with the ΣΛ conversion process. The physical meaning will be intensively discussed in this paper. In fact, we have clearly shown, in this paper, that the effect due to the ΣΛ conversion process is in the enhancement just above the ΛN threshold. If the experimental data should be interpreted by the two-step process K^?d → π^?(ΣN) → π^?Λp, the effect due to the ΣΛ conversion process should have appeared in the experimental data, although some experimental data do not show the enhancement just above the ΛN threshold.