A study of double pomeron exchange inπ + p andK + p interactions at 250 GeV/c

Using the ARGUS detector at thee ⁺ e ^– storage ring DORIS II at DESY, we have measured the inclusive production ofD ⁰,D ⁺ andD ^*(2010)⁺ mesons inB decays and in nonresonante ⁺ e ^– annihilation around 10.6 GeV. The inclusive branching ratios forB decays toD ⁰,D ⁺ andD ^*+ mesons are found to be (52.2±8.2±3.5)%, (27.2±6.3±3.5)% and (34.8±6.0±3.5)% respectively. Thus,D ⁰ andD ⁺ production account for about 70% of the charm produced inB decays, neglectingbu contributions to the total width. The production cross sections and momentum spectra for continuume ⁺ e ^– annihilation are also presented.Supported by the German Bundesministerium für Forschung und Technologie, under contract number 054DO51P     

Prompt ternary break-up in 32S+59Co and 32S+63Cu reactions at 5.6 A · MeV

Final states indicating the presence in the reaction of three-body fragmentation processes has been observed in ³²S+⁵⁹Co and ³²S+⁶³Cu dissipative collisions at 5.6 A · MeV. Besides the already observed sequential binary process, data analysis reveals the presence of prompt ternary break-up of the composite system. Indications on the system configuration at the scission have been deduced by analyzing the event shape in the momentum phase space. The decay appears to occur in a collinear configuration, one of the produced fragments originating from the neck which connects the other two. In spite of the large energy dissipation, structure effects in the charge partition seem to affect part of events. Received: 3 July 1998 / Revised version: 15 October 1999     

Microscopic description of the reactions d + d → p + 3H and d + d → n + 3He at low energies

A collective adiabatic approach is used to explore the total and differential cross sections for the reactions d + d → p + ³H and d + d → n + ³He at incident-deuteron energies of up to 6 MeV. All substantially contributing partial waves of order not higher than that of G waves are taken into account. The experimental value of the difference of the cross sections for the above mirror reactions is reproduced theoretically under the assumption that nuclear forces obey the condition of isotopic invariance. The positions and amplitudes of the maxima in the calculated total cross sections virtually coincide with those of the corresponding experimental values. It is shown that, around the maxima of the cross sections under study, dominant contributions to them come from the P wave. The sensitivity of observables to the parameters of nucleon-nucleon interaction is analyzed.     

Study of the mechanism of the 3He + p → p + p + d reaction at a 3He momentum of 5 GeV/c

The mechanism of the reaction ³He + p → p + p + d is studied by making use of the ITEP 80 cm liquid-hydrogen bubble chamber exposed to a beam of 5 GeV/c ³He nuclei. The reaction cross section is equal to 20.6 ± 0.3 mb. The phase-space regions associated with quasifree scattering (QFS) and final-state interactions (FSI) are selected. Angular, mass and momentum distributions of the reaction products are obtained in the entire kinematically allowed range. The experimental data in the QFS region are compared with theoretical calculations based on the simplest pole-diagram approximation. The ³He and deuteron wave functions (WF) correspond to the realistic RSC potential. The D-wave components of these WF are taken into account. The absolute value of the cross section and shape of the distributions are described as a whole reasonably well within the frame of the model considered in the kinematical region where FSI may be neglected. But at large spectator momenta there is an essential disagreement. The possible reasons for this are discussed.     

Measurement of A zz of pd radiative capture at E d = 196 MeV

In our previous measurement of pd radiative capture at E _d = 137 and 196?MeV, we found an interesting fact that the measured tensor analyzing powers show the relation A _xx ≈ A _yy , although calculated A _xx and A _yy are apparently different, A _xx ≠ A _yy . The measured A _yy agrees fairly well with the 3N calculations, and the measured A _xx largely disagrees with calculated A _xx . Similar experiments on pd capture have been made at KVI at nearly the same energies of 130–180?MeV. The KVI data also support A _xx ≈ A _yy relation, but absolute values of A _xx and A _yy at KVI are about half of RCNP data. Therefore, we made a new experiment of pd capture at E _d = 196?MeV. A _zz was measured in three different ways, and data analysis is in progress. Preliminary data seem to support our previous data.     

Measurement of PV asymmetry in +p→d+γ and ■+d→n+p

The measurement of parity-violating (PV) observables in few-nucleon system can shed light on our current understanding of the weak interaction between nucleons.Theoretical models describe the nucleonnucleon weak interaction at low energies use a series of undetermined parameters.Two parity violating measurements have been considered: the capture of polarized slow neutrons on hydrogen (n + p → d + γ) at Los Alamos National Laboratory for first phase and Oka Ridge National Laboratory for second phase and the helicity dependence of the deuteron photodisintegration cross section using circularly polarized photons (γ + d → n + p) at Shanghai Institute of Applied Physics.The goal of both experiments is to constraint the weak meson-nucleon couplings to a precision of 1 ×10-8 .The introduction of both experiments is presented.     

A study ofK + p elastic scattering and reactionK + p→K + pπ+π− at 70 GeV/c

Results are presented onK ⁺ p elastic scattering and on the reactionK ⁺ p→K ⁺ pπ⁺π^? at 70 GeV/c. For the elastic channel, we measured the total ((2.29±0.04)mb) and differentialdσ/dt cross sections. The reactionK ⁺ p→K ⁺ pπ⁺π^? has a total cross section of (470±23) μb and is shown to be dominated by diffractive dissociation processes. The contributions of the quasi-two-body channels $$K^ + p \to K*^0 (890)\Delta ^{ + + } (1,236)$$ and $$K^ + p \to K*^0 (1,430)\Delta ^{ + + } (1,236)$$ and of the Double-Pomeron Exchange (DPE) processes are estimated.     

A systematic study of irrational precipitation crystallography in fcc–bcc systems with an analytical O-line method

Precipitations that exhibit irrational transformation crystallography can often be explained in terms of the O-lines in the habit plane. The present work developed an analytical O-line method, which is more useful than the numerical O-line method to study the variation in the habit plane and its structure in a systematic manner. This method has an advantage that the orientation relationship (OR) is the output from the calculation, while in many other models interpreting precipitation crystallography the OR is either an input or is constrained by a prerequisite condition. This paper described the derivation of this method and its application to the study of the precipitation crystallography in fcc-bcc systems. Examples were given for three alloy systems, namely Cu-0.33wt%Cr and Ni-45wt%Cr alloys and a duplex-phase a-y stainless steel. The solutions include the OR between the precipitates and their matrix, the habit plane, the invariant line and the dislocation structure in the habit plane. The calculated results are in good agreement with the experimental observations reported in the literatures. Furthermore, the variation in the optimum O-line features with the lattice parameter ratio has also been studied systematically, providing some guidelines for estimating and understanding possible transformation crystallography from different fcc-bcc systems.     

A modified explanation of cold nuclear matter effects on J/ψ production in p+A collisions

A modified explanation of the cold nuclear matter(CNM) effects on J/ψ production in p+A collisions is presented in this paper.The advantage of the modified explanation is that all the CNM effects implemented in this model have clear physical origins and are mostly centered on the idea of multiple parton scattering.With the CNM effects presented in this paper, we calculated the nuclear modification factor Rp A in J/ψ production under different collision energies.The results are compared with the corresponding experiment data and the factors calculated with classic nuclear effects.The factors calculated with CNM effects presented in this paper can accurately reproduce almost all existing J/ψ measurements in p-A collisions, which is much better than results obtained with the factors calculated with classic nuclear effects.The new model is therefore a more suitable approach to explain CNM effects in the hardproduction of quarkonium.     

Resonant structure due to the 3p→3d transition in the photoionization of Ca+

Many-body perturbation theory has been used to calculate the resonance structure (3p→3d) into the photoionization (4s→kp) for ion Ca⁺. This resonance structure results from the interference between a photoionization process or a photoionization with excitation process and a resonant Auger process. The coupled equation method has been improved to calculate this interference by the summation of specific classes of diagrams of perturbation theory to infinite order. The resonance structure in the region of the 3p threshold is enhanced via a super-Coster–Kronig transition. The theoretical results are in good agreement with experiment.     

A study of (n,nα) reaction cross sections at 14.7 MeV

Cross sections for (n, nα) reactions induced by 14.7 ± 0.3 MeV neutrons on ⁵¹V, ⁹²Mo, ¹¹⁵In, ¹⁶⁵Ho and ¹⁷⁶Yb have been measured by the activation technique using radiochemical separations and high resolution γ-ray spectroscopy or low-level β⁻counting. A brief summary of the activation data reported in the literature is given and a tentative trend in the data is suggested. The contribution of the (n, nα) process generally amounts to between 10 and 15% of the (n, α) cross section; in some cases, however, it is as low as 0.5%. The summed (n, α) and (n, nα) reaction cross sections obtained by the activation technique are generally in agreement with those deduced from emitted α-particle characterisation as well as mass spectrometry. Detailed Hauser-Feshbach calculations show that the statistical model can describe the (n, nα) cross section only with partial success.     

A numerical study of nonlinear and anti-sound effects of sound propagation in ducts

A numerical method dealing with anti-sound effect is presentedto calculate nonlinear sound propagation in varying cross section areaand hard-wall ducts with transonic flow and without acousticshock waves.The effects of duct geometry,the flow Mach number atthe throat,the sound source intensity at the inlet and the anti-soundintensity on the nonlinear sound propagation are discussed through severalexamples.It is also shown from the examples that there is an optimalanti-sound intensity at which a remarkable sound attenuation can beobtained at the exit.     

Discrepancy of Cross Sections in pd Breakup Reactions at E p = 250?MeV

In our previous inclusive experiment on ²H(p, p)pn at 247?MeV, the measured cross section at forward angles is about twice larger than 3N calculation with ?Ц? 3NF. Therefore, we have made an exclusive experiment on ²H(p, p ₁ p ₂)n at the same energy. The preliminary data suggest that the cross section was enhanced at forward angle of ?? ₁ and ?? ₂.     

A study of K−π+ scattering in the reaction K−p→K−π+n at 11 GeV/c

Results from a high statistics study of the reaction K⁻p→K⁻π⁺n are presented. These results are based on data obtained with an 11 GeV/c beam using the LASS spectrometer at SLAC. The mass dependence of the spherical harmonic moments provides clear evidence for the production of the complete leading orbitally excited K¹ series up through J^P = 5⁻. These moments are used to perform an energy independent partial wave analysis of the K⁻π⁺ system from threshold to 2.6 GeV/c² using a t-dependent parametrization of the production amplitudes. The amplitudes corroborate the leading K¹(892), K₂¹(1430), K₃¹(1780), K₄¹(2060), and K₅¹(2380) resonances observed directly in the moments, and also provide new evidence for underlying states. The 0⁺ amplitude contains the K₀¹(1350) and a second 0⁺K¹(1950) at higher mass. The 1⁻K¹(1790) seen earlier two and three-body analyses is confirmed, and evidence is provided for suppressed K⁻π⁺ decay mode of a second 1⁻ state, the K¹(1410), which has been seen in earlier three-body analyses.     

The 13C(p̄, d)12C reaction at 119 MeV

Differential cross sections and analysing powers for transitions to many residual states of ¹²C below 20 MeV excitation energy have been measured for the (p̄, d) reaction on ¹³C at 119 MeV. Distorted wave Born approximation calculations using either adiabatic or conventional deuteron elastic scattering potentials were unable to adequately reproduce the cross-section and analysing power data for the strongest observed transitions. In order to improve the fits to both these sets of data it was necessary to include an imaginary spin-orbit term in the deuteron potential. The spectroscopic factors deduced in this analysis are, however, smaller than theoretical predictions. The mechanisms for the population of the observed weak residual states are discussed semi- quantitatively, and for the higher excitation energy region, a comparison to the known level structure of ¹²C is made.     

类钴Pd19+离子3p63d9-3p53d10,3p63d9-3p83d84p跃迁的计算

用多组态自洽场方法,结合我们提出的半经验拟合公式,计算了高离化态类钴Pd19+离子3p63d9-3p53d10,3p63d9-3p83d84p跃迁和振子强度,并与实验符合得较好。     

A-dependence of φ-meson production in p + A collisions

A systematic analysis of the A-dependence of φ-meson production in proton-nucleus collisions is presented. We apply different formalisms for the evaluation of the φ-meson distortion in nuclei and discuss the theoretical uncertainties of the data analysis. The corresponding results are compared to theoretical predictions. We also discuss the interpretation of the extracted results with respect to different observables and provide relations between frequently used definitions. The perspectives of future experiments are evaluated and estimates based on our systematical study are given.     

Measurement of all Deuteron Analyzing Powers for {\overrightarrow{d} + p} Elastic Scattering at 294 MeV/Nucleon

We have measured all deuteron analyzing powers ${(A_{y}^{d}, A_{yy}, A_{xx}, A_{xz})}$ for deuteron-proton elastic scattering at 294 MeV/nucleon in order to study the properties of three nucleon forces (3 NFs). Measurement was made at in an angular range of ${\theta_{{\rm c.m.}} = 35.6^{\circ} - 163.0^{\circ}}$ . Obtained data were compared with Faddeev calculations with and without the 3 NFs. At ${\theta_{{\rm c.m.}}\lesssim 120^{\circ}}$ all the data have general agreement with the calculations, while the measured data at ${\theta_{{\rm c.m.}} \gtrsim 120^{\circ}}$ are not explained by any theoretical calculations. These results were consistent with those at 250 MeV/nucleon.     

Measurement of PV asymmetry in(→n)+p→d+γ and (→γ)+d→n+p

The measurement of parity-violating(PV)observables in few-nucleon system can shed light on our current understanding of the week interaction between nucleons.Theoretical models describe the nucleonnucleon weak interaction at low energies use a series of undetermined parameters.Two parity violating measurements have been considered: the capture of polarized slow neutrons on hydrogen((n)+p→d+γ)at Los Alamos National Laboratory for first phase and Oka Ridge National Laboratory for second phase and the helicity dependence of the deuteron photodisintegration cross section using circularly polarized photons((γ)+d→n+p*)at Shanghai Institute of Applied Physics.The goal of both experiments is to constraint the weak meson-nucleon couplings to a precision of 1 × 10-8.The introduction of both experiments is presented.