Stripping of deuterons with 2·45 GeV/c momentum in nuclear emulsion

This paper is concerned with the evaluation of the cross-section (d, p) of the stripping due to collision of a fast-deuteron beam with atom nuclei forming a photographic nuclear emulsion without evaporation of nuclei. The cross-section was estimated using the deuteron mean free path with respect to mentioned reactions. The deuteron track on which the stripping reaction took place was identified according to the change of the characteristic of multiple scattering. Corrections were taken for the primary-beam impurities and for the length of each track where reaction was nor identifiable.Devoted to Professor V. Petrílka on his sixty-fifth birthday.     

s~(1/2)=355GeV附近的R值测量

利用北京谱仪 (BES)在s=3.5 5GeV附近获取的总积分亮度约为 5 pb-1的实验数据 ,测量了e e-湮没强子产生截面与 μ子对产生截面的比值 (即R值 ) .其测量误差比其它实验组已发表的此能区的测量误差减小约 5 0 % .     

Spallation of copper by 9 GeV/c protons and deuterons

The spallation of copper by 9 GeV/c protons and deuterons has been studied. Cross sections for the production of radionuclides with 24 A 60 were determined from direct gamma-ray counting of irradiated targets with a Ge(Li) — spectrometer. The results were parametrized in terms of a 6-parameter formula which reproduces the measured charge-dispersion and mass-yield distributions. The proton results are compared with previous investigations.We wish to acknowledge with thanks the cooperation of Yu. A. Panebratsev, A. N. Khrenov, V. G. Perevozchikov and the members of the Dubna synchrophasotron staff. Without their assistance the present work would not have been possible.     

Interactions of 9.4 GeV/c deuterons in an emulsion: Multiplicity and angular distributions

An analysis of 1650 stars induced by 9.4 GeV/c deuterons in a nuclear emulsion is presented. Multiplicity and angular distributions of secondaries are discussed.     

Target residues from the reactions of 9 GeV/c protons and deuterons with181Ta

The production of radioactive nuclides in the reactions of 9 GeV/c protons and deuterons with¹⁸¹Ta has been investigated at the Dubna synchrophasotron. The production cross section of target fragments with 24≦A≦178 were determined by off-line gamma-spectroscopy. Charge dispersions and mass yields are deduced from these data. The results are discussed in terms of the concepts of high-energy nuclear physics.     

K1±(890) production in 205 GeV/c pp interactions

Using data obtained from an exposure of the Fermilab 30-inch hydrogen bubble chamber to a 205 GeVc proton beam, we have studied K⁰π^± correlations and the inclusive production of K¹(890). Based on an analysis of the K_S⁰π^± effective mass distribution, we find a 95% confidence level upper limit of 0.22 K^1±(890) per inelastic event. Possible systematic effects in the experimental determination of the ?⁰ production rate due to the Kπ correlation are discussed. Our result for K¹ production at √s = 19.7 GeV is incompatible with that obtained in a recent ISR experiment at √s = 53 GeV.     

Measurements of GnE/GnM from the 2H(e-->,en-->)1H Reaction to Q2=1.45 (GeV/c)2

We report new measurements of the ratio of the electric form factor to the magnetic form factor of the neutron, G(n)(E)/G(n)(M), obtained via recoil polarimetry from the quasielastic 2H(e-->,e(')n-->)1H reaction at Q2 values of 0.45, 1.13, and 1.45 (GeV/c)(2) with relative statistical uncertainties of 7.6% and 8.4% at the two higher Q2 points, which points have never been achieved in polarization measurements.     

Quasielastic 3He(e,e'p)2H reaction at Q2 = 1.5 GeV2 for recoil momenta up to 1 GeV/c

We have studied the quasielastic 3He(e,e(')p)2H reaction in perpendicular coplanar kinematics, with the energy and the momentum transferred by the electron fixed at 840 MeV and 1502 MeV/c, respectively. The 3He(e,e(')p)2H cross section was measured for missing momenta up to 1000 MeV/c, while the A(TL) asymmetry was extracted for missing momenta up to 660 MeV/c. For missing momenta up to 150 MeV/c, the cross section is described by variational calculations using modern 3He wave functions. For missing momenta from 150 to 750 MeV/c, strong final-state interaction effects are observed. Near 1000 MeV/c, the experimental cross section is more than an order of magnitude larger than predicted by available theories. The A(TL) asymmetry displays characteristic features of broken factorization with a structure that is similar to that generated by available models.     

Scaling in soft hadroproduction by positive projectiles in the range of 32–147 GeV/c

The total hadron multiplicity and the multiplicity in the three-jet events ine ⁺ e ^?-annihilation are considered. The formula for the total multiplicity (with account for the heavy quark contribution) agrees well with experiment. The value of the multiplicity for three-jet events is predicted.     

1GeV/c Wide Range Magnetic Spectrometer

The structure of an 1GeV/c wide-range magnetic spectrometer is briefly described.The spectrometer includes the magnet system and the detector & data acquisition system.The momentum formula at extended edge field case for non-focusing magnetic spectrometer has been derived.The momentum resolution,solid angle,momentum acceptance and other parameters for this spectrometer are calculated by Monte Carlo simulation.The effects of the multiple scattering and position resolution of the detectors to momentum resolution of this spectrometer are discussed.     

Observation of a broad structure in the pi+ pi- J/psi mass spectrum around 4.26 GeV/c2

We study initial-state radiation events, e+ e- --> gammaISR pi+ pi- J/psi, with data collected with the BABAR detector. We observe an accumulation of events near 4.26 GeV/c2 in the invariant-mass spectrum of pi+ pi- J/psi. Fits to the mass spectrum indicate that a broad resonance with a mass of about 4.26 GeV/c2 is required to describe the observed structure. The presence of additional narrow resonances cannot be excluded. The fitted width of the broad resonance is 50 to 90 MeV/c2, depending on the fit hypothesis.     

Analysis of pp → K+K− π+π− around 1 GeV/c

Approximately 100 000 four-prong antiproton annihilations in hydrogen were measured. A clean, unbiased sample of 842 K⁺K^?π⁺π^? events was obtained. This reaction is dominated by $\text{K}{}^1\text{(～45\%)}$ and ?⁰(～20%) production, with smaller amounts of A₂⁰(～15%) and ?(～5%) production. 25% of the reactions involved double resonance production. No significant three-body resonance production is observed.     

Electroproduction of single charged pions from deuterons at Q2 ∼0.5 (GeV/c)2

The ratio of π^? to π⁺ electroproduction cross sections from deuterons has been measured in the resonance region at an average four-momentum transfer squared of 0.5 (GeV/c)². Results are presented over a wide range of pion production angles and comparisons are made with theoretical predictions based on SU(6)_w symmetry and the Melosh transformation.     

Elastic electron-proton scattering between 0.05 and 0.30 (GeV/c)2

Elastic electron proton scattering has been used to check the validity of the dipole fit of the proton form factors at momentum transfer between 0.05 and 0.30 (GeV/c)². The general behaviour of the cross sections is in agreement with previous measurements and is close to the dipole predictions but there is the suggestion of some small amplitude deviations. It is speculated that these deviations may be related to similar effects in the proton formfactor derived from the ISR pp elastic scattering data via a Chou-Yang model.     

Measurement of strange-quark contributions to the nucleon's form factors at Q(2) = 0.230 (GeV/c)(2)

We report on a measurement of the parity-violating asymmetry in the scattering of longitudinally polarized electrons on unpolarized protons at a Q2 of 0.230 (GeV/c)(2) and a scattering angle of theta (e) = 30 degrees - 40 degrees. Using a large acceptance fast PbF2 calorimeter with a solid angle of delta omega = 0.62 sr, the A4 experiment is the first parity violation experiment to count individual scattering events. The measured asymmetry is A(phys)=(-5.44+/-0.54(stat)+/-0.26(sys))x10(-6). The standard model expectation assuming no strangeness contributions to the vector form factors is A(0) = (-6.30+/-0.43) x 10(-6). The difference is a direct measurement of the strangeness contribution to the vector form factors of the proton. The extracted value is G(s)(E) + 0.225G(s)(M) = 0.039+/-0.034 or F(s)(1) + 0.130F(s)(2) = 0.032+/-0.028.     

K1±(892) Production in π−N interactions at 200 GeV/c

K^1±(892) production is studied in the reaction π^?N → K_S⁰K_S⁰ + X where X includes up to five observed charged particles. An excess of K^1? over K¹⁺ is observed for Feynman-x > 0.1. The ratio of K¹⁺ to K^1? decreases with x as predicted by QCD counting rules. K_S⁰ and K¹ production are compared to recent D and D¹ data from other experiments.     

Asymmetry in the scattering of protons on polarized deuterons at 1.21 GeV/c

By using a polarized deuteron target we have measured the asymmetry in the differential cross section for elastic scattering of protons on deuterons and for quasi-elastic scattering of protons on protons bound in deuterons between the two states of opposite polarization, normal to the scattering plane of the initial deuteron. The beam momentum was 1.21 GeV/c. It is checked that the neutrons bound in the deuterons are polarized to approximately 20%.     

Single-pion production in pp collisions at 0.95 GeV/c (II)

The single-pion production reactions pp d , pp np and pp pp were measured at a beam momentum of 0.95GeV/c ( T _p 400 MeV) using the short version of the COSY-TOF spectrometer. The central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements from other detector parts. Thus all pion production channels were recorded with 1-4 overconstraints. The main emphasis is put on the presentation and discussion of the np channel, since the results on the other channels have already been published previously. The total and differential cross-sections obtained are compared to theoretical calculations. In contrast to the pp channel we observe in the np channel a strong influence of the excitation. In particular, the pion angular distribution exhibits a (3 cos² + 1) -dependence, typical for a pure s -channel excitation and identical to that observed in the d channel. Since the latter is understood by a s -channel resonance in the ¹ D ₂ pn partial wave, we discuss an analogous scenario for the pn channel.     

Single-pion production in pp collisions at 0.95 GeV/c (I)

The single-pion production reactions pp → dπ⁺, pp → npπ⁺ and pp → ppπ⁰ were measured at a beam momentum of 0.95GeV/c ( T _p ≈ 400MeV) using the short version of the COSY-TOF spectrometer. The implementation of a central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements. Thus, all pion production channels were recorded with 1-4 overconstraints. The total and differential cross-sections obtained are compared to previous data and theoretical calculations. Main emphasis is put on the discussion of the ppπ⁰ channel, where we obtain angular distributions different from previous experimental results, however, partly in good agreement with recent phenomenological and theoretical predictions. In particular, we observe very large anisotropies for the π⁰ angular distributions in the kinematical region of small relative proton momenta revealing there a dominance of proton spinflip transitions associated with π⁰ s and d partial waves and emphasizing the important role of π⁰ d-waves.     

Determination of the pion charge form factor at Q2=1.60 and 2.45 (GeV/c)2

The 1H(e,e'pi+)n cross section was measured at four-momentum transfers of Q2=1.60 and 2.45 GeV2 at an invariant mass of the photon nucleon system of W=2.22 GeV. The charged pion form factor (F(pi)) was extracted from the data by comparing the separated longitudinal pion electroproduction cross section to a Regge model prediction in which F(pi) is a free parameter. The results indicate that the pion form factor deviates from the charge-radius constrained monopole form at these values of Q2 by one sigma, but is still far from its perturbative quantum chromodynamics prediction.