The K − p reactions leading to charge exchange and hyperon final states have been studied at nine momenta between 862 and 1001 MeV/ c using data from a 600 000 picture exposure of the Lawrence Berkeley Laboratory 25″ liquid hydrogen bubble chamber. Partial cross sections are determined for all final states resolved by kinematic fitting. In addition, differential cross sections are presented for the two-body final states K o n , Λπ o and Σ +- π -+ along with hyperon polarization angular distributions for Λπ o and Σ + π − .
No description provided.
The differential cross sections of the combined elastic and break-up K − d reaction have been measured at 1.21, 1.42 and 2.61 GeV/ c incident K − momentum. The measurements have been performed at the CERN PS using multiwire proportional chambers. The values of the invariant momentum transfer t explored (0.0005<| t |<0.1 GeV 2 ) include the Coulomb-nuclear interference region. The differential cross sections have been analysed in the framework of the Glauber impact-parameter formalism. The observed interference effects have been used to derive the ratio of the real to imaginary part of the forward K − n nuclear amplitude.
USING OPTICAL THEOREM: IMAGAMP1 = 0.0403*P*SIG.
None
No description provided.
We have measured the differential cross section d2σdΩdTπ and the polarization parameter P for the production of π+ and π− in various target nuclei (H1, H2, Be, C, O, Al, Ni, Cu, Mo, and Pb) by protons with a kinetic energy of 585 MeV, for production angles θπ=22.5°, 45°, 60°, 90°, and 135°, and for pion kinetic energies Tπ of 24, 35, 46, 88, 151, 192, and 254 MeV (all quantities in the laboratory system). Our data disagree strongly with recent data for 580-MeV protons. On the other hand, for pion energies up to 150 MeV, our cross sections differ little from those measured for a proton energy of 730 MeV. For nuclei with A>20, the total production cross sections σ(π+) and σ(π−) show the Z13 and N23 proportionality expected from theoretical arguments. There is evidence in our data of a shift of the π+ energy distributions compared to the π− distributions due to the effects of the Coulomb field of the nuclear protons on the emitted pions. NUCLEAR REACTIONS H1, H2, Be, C, O, Al, Ni, Cu, Mo, Pb p, π±, Tp=585 MeV; measured σ(Tπ, θπ) and asymmetry parameter P(Tπ, θπ).
No description provided.
A measurement of the nucleon structure function F 2 on iron is presented. The data cover a kinematic range of 3.25 ⪕ Q 2 ⪕ 200 GeV 2 and 0.05 ⪕ x ⪕ 0.65 . The data clearly show scaling violation. Fits in leading-order QCD have been made and values for the scale breaking parameter λ are given.
No description provided.
A precision measurement of the angular distribution of the analyzing power of the reaction p + p → d + π + has been made at 0.8 GeV. It is shown that none of the existing theoretical calculations, including those which introduce resonant dibaryon amplitudes, reproduce even the qualitative features of the data. It is concluded that our data do not require dibaryon admixtures of the kind proposed for the interpretation of recent data on vector analyzing power, i T 11 (θ), of π− d elastic scattering at the same center of mass energy.
LOWER ENERGY DATA NOT IN PUBLICATION.
LOWER ENERGY DATA NOT IN PUBLICATION.
LOWER ENERGY DATA NOT IN PUBLICATION.
Angular distributions of the analyzing powers for π+p→ and π−p→ elastic scattering have been measured in a single-scattering experiment employing a polarized proton target. Measurements were obtained for pion energies of 98, 139, 166, 215, and 263 MeV. The addition of these data to the existing πp database significantly reduces the uncertainties in all S and P phase shifts for πp reactions over the delta resonance.
Measured values of the analyzing power for PI+ P elastic scattering at incident kinetic energy 98 MeV.
Measured values of the analyzing power for PI+ P elastic scattering at incident kinetic energy 139 MeV.
Measured values of the analyzing power for PI+ P elastic scattering at incident kinetic energy 166 MeV.
In order to improve existing I=0 phase shift solutions, the spin correlation parameter ANN and the analyzing powers A0N and AN0 have been measured in n-p elastic scattering over an angular range of 50°–150° (c.m.) at three neutron energies (220, 325, and 425 MeV) to an absolute accuracy of ±0.03. The data have a profound effect on various phase parameters, particularly the P11, D23, and ε1 phase parameters which in some cases change by almost a degree. With the exception of the highest energy, the data support the predictions of the latest version of the Bonn potential. Also, the analyzing power data (A0N and AN0) measured at 477 MeV in a different experiment over a limited angular range [60°–80° (c.m.)] are reported here.
The beam analysing power at incident kinetic energy 220 MeV. Additional systematic uncertainty of +- 0.015 and a scalar error of 3.5 PCT.
The beam analysing power at incident kinetic energy 325 MeV. Additional systematic uncertainty of +- 0.018 and a scalar error of 3.1 PCT.
The beam analysing power at incident kinetic energy 425 MeV. Additional systematic uncertainty of +- 0.022 and a scalar error of 3.3 PCT.
A high-statistics measurement of the differential cross-sections for neutrino-iron scattering in the wide-band neutrino beam at the CERN SPS is presented. Nucleon structure functions are extracted and theirQ2 evolution is compared with the predictions of quantum chromodynamics.
Structure functions for neutrino and antineutrino combined.
Data from BEBC experiments are combined to provide large statistics for neutrino interactions. ChargedD* mesons are produced in (1.22±0.25)% of neutrino and (1.01±0.31)% of antineutrino charged current interactions. The mean fraction of the hadronic laboratory energy taken by theD*+ in these events is 0.59±0.03±0.08. Less than 18% of all chargedD* mesons from (anti)neutrino interactions are found to be daughters ofD**0 (at the 90% confidence level).
Mean fractional hadronic energy carried by the D*+- in the laboratory system.
The experimental setup and detection technique of the COSY-11 installation, an internal experimental facility at the cooler synchrotron and storage ring COSY Jülich, are described. The detection system has been designed for meson production studies with full geometrical acceptance close to threshold. Preliminary results of first measurements are presented, emphasis is put on strangeness production in the reactions pp → ppK + K − and pp → pK + Λ .
Excess energy of 6.1 MeV above threshold 3.3016 GeV.
Excess energy of 2 MeV above threshold 2.339 GeV.
Threshold measurements of the associated strangeness production reactions pp --> p K(+) Lambda and pp --> p K(+) Sigma(0) are presented. Although slight differences in the shapes of the excitation functions are observed, the most remarkable feature of the data is that at the same excess energy the total cross section for the Sigma(0) production appears to be about a factor of 28 smaller than the one for the Lambda particle. It is concluded that strong Sigma(0)-p final state interactions, and in particular the Sigma-N --> Lambda-p conversion reaction, are the likely cause of the depletion for the yield in the Sigma signal. This hypothesis is in line with other experimental evidence in the literature.
The given errors are statistical only. The cross section presented as a function of the nominal excess energy.
The production of eta mesons has been measured in the proton-proton interaction close to the reaction threshold using the COSY-11 internal facility at the cooler synchrotron COSY. Total cross sections were determined for eight different excess energies in the range from 0.5 MeV to 5.4 MeV. The energy dependence of the total cross section is well described by the available phase-space volume weighted by FSI factors for the proton-proton and proton-eta pairs.
The total cross sections as a function of beam momentum and excess energy with statistical errors. The uncertainty on the beam momentum and excess energy are +- 0.00080 GeV and +- 0.28 MeV respectively.
Total cross sections for the pp --> pp eta' reaction have been measured in the excess energy range from Q = 1.53 MeV to Q = 23.64 MeV. The experiment has been performed at the internal installation COSY-11 using a stochastically cooled proton beam of the COoler SYnchrotron COSY and a hydrogen cluster target. The determined energy dependence of the total cross section weakens the hypothesis of the S-wave repulsive interaction between the eta' meson and the proton. New data agree well with predictions based on the phase-space distribution modified by the proton-proton final-state-interaction (FSI) only.
Total cross sections w.r.t the excess energy in the CM system. Statistical errors only are given. As well as the 15 PCT overall systematic uncertainty there is an uncertainty on the energy of 0.44 MeV.
We report on a measurement of the differential cross sections of inclusive$K^{\pm}_{890}$production in$\sigma^-, pi^-$and ne
The production cross sections for K*+- per nucleus and per nucleon for the SIGMA- beam.
The production cross sections for K*+- per nucleus and per nucleon for the PI- beam.
A precision measurement of absolute pi+p and pi-p elastic differential cross sections at incident pion laboratory kinetic energies from T_pi= 141.15 to 267.3 MeV is described. Data were obtained detecting the scattered pion and recoil proton in coincidence at 12 laboratory pion angles from 55 to 155 degrees for pi+p, and six angles from 60 to 155 degrees for pi-p. Single arm measurements were also obtained for pi+p energies up to 218.1 MeV, with the scattered pi+ detected at six angles from 20 to 70 degrees. A flat-walled, super-cooled liquid hydrogen target as well as solid CH2 targets were used. The data are characterized by small uncertainties, ~1-2% statistical and ~1-1.5% normalization. The reliability of the cross section results was ensured by carrying out the measurements under a variety of experimental conditions to identify and quantify the sources of instrumental uncertainty. Our lowest and highest energy data are consistent with overlapping results from TRIUMF and LAMPF. In general, the Virginia Polytechnic Institute SM95 partial wave analysis solution describes our data well, but the older Karlsruhe-Helsinki PWA solution KH80 does not.
Centre of mass absolute differential cross sections at pion kinetic energy 141.15 MeV using the liquid H2 target and single arm pion detection. There is an additional systematic error of 1.1 PCT for PI+ beams which is not included in the errors shown in the table.
Centre of mass absolute differential cross sections at pion kinetic energy 141.15 MeV using the liquid H2 target and two arm pion detection. There is an additional systematic error of 1.3 PCT for PI+ beams which is not included in the errors shown in the table.
Centre of mass absolute differential cross sections at pion kinetic energy 141.15 MeV using the liquid H2 target and two arm pion detection. There is an additional systematic error of 1.3 PCT (1.6 PCT) for PI+ (PI-) beams which is not included in the errors shown in the table.
We report first results on elliptic flow of identified particles at mid-rapidity in Au+Au collisions at $\sqrt{s_{_{NN}}}=130$ GeV using the STAR TPC at RHIC. The elliptic flow as a function of transverse momentum and centrality differs significantly for particles of different masses. This dependence can be accounted for in hydrodynamic models, indicating that the system created shows a behavior consistent with collective hydrodynamical flow. The fit to the data with a simple model gives information on the temperature and flow velocities at freeze-out.
Differential elliptic flow of pions for different centrality bins. The systematic uncertainty is smallest for the centrality region with the best reaction plane resolution and is estimated to be 20% for the most central bin, 8% for the mid-central bin, and 22% for the most peripheral bin.
Differential elliptic flow of protons + antiprotons for different centrality bins. The systematic uncertainty is smallest for the centrality region with the best reaction plane resolution and is estimated to be 20% for the most central bin, 8% for the mid-central bin, and 22% for the most peripheral bin.
The reaction ${n} {p} \to {p} {p} \pi^{-}$ has been studied in a kinematically complete measurement with a large acceptance time-of-flight spectrometer for incident neutron energies between threshold and 570 MeV. The proton-proton invariant mass distributions show a strong enhancement due to the pp($^{1}{S}_{0}$) final state interaction. A large anisotropy was found in the pion angular distributions in contrast to the reaction ${p}{p} \to {p}{p} \pi^{0}$. At small energies, a large forward/backward asymmetry has been observed. From the measured integrated cross section $\sigma({n}{p} \to {\rm p}{p} \pi^{-})$, the isoscalar cross section $\sigma_{01}$ has been extracted. Its energy dependence indicates that mainly partial waves with Sp final states contribute. Note: Due to a coding error, the differential cross sections ${d \sigma}/{d M_{pp}}$ as shown in Fig. 9 are too small by a factor of two, and inn Table 3 the differential cross sections ${d \sigma}/{d \Omega_{\pi}^{*}}$ are too large by a factor of $10/2\pi$. The integrated cross sections and all conclusions remain unchanged. A corresponding erratum has been submitted and accepted by European Physics Journal.
The total integrated cross section for exclusive PI- production in N P interactions as a function of the incident kinetic energy (EKIN), ETA (=P(p=5,rf=cm)/M(pi) and the excess energy Q (=srqt(s)-sqrt(s-threshold)).
Distributions of event-by-event fluctuations of the mean transverse momentum and mean transverse energy near mid-rapidity have been measured in Au+Au collisions at sqrt(s_NN) = 130 GeV at RHIC. By comparing the distributions to what is expected for statistically independent particle emission, the magnitude of non-statistical fluctuations in mean transverse momentum is determined to be consistent with zero. Also, no significant non-random fluctuations in mean transverse energy are observed. By constructing a fluctuation model with two event classes that preserve the mean and variance of the semi-inclusive p_T or e_T spectra, we exclude a region of fluctuations in sqrt(s_NN) = 130 GeV Au+Au collisions.
The $M_{p_T}$ distributions for four different centrality classes. The curves are the random baseline mixed event distributions.
The residual distribution between the data and mixed event $M_{p_T}$ in units of standard deviations for all centrality classes. The total ${\chi}^2$ and the number of degrees of freedom for the $0-5\%$, $0-10\%$, $10-20\%$, $20-30\%$ centrality classes are 89.0/39, 155.7/40,163.3/47, and 218.4/61, respectively.
The $M_{e_T}$ distributions for four different centrality classes. The curves are the random baseline mixed event distributions. The source of differences in the data and mixed event distributions are addressed in the text.
Measurements of charged pion and kaon production in central Pb+Pb collisions at 40, 80 and 158 AGeV are presented. These are compared with data at lower and higher energies as well as with results from p+p interactions. The mean pion multiplicity per wounded nucleon increases approximately linearly with s_NN^1/4 with a change of slope starting in the region 15-40 AGeV. The change from pion suppression with respect to p+p interactions, as observed at low collision energies, to pion enhancement at high energies occurs at about 40 AGeV. A non-monotonic energy dependence of the ratio of K^+ to pi^+ yields is observed, with a maximum close to 40 AGeV and an indication of a nearly constant value at higher energies.The measured dependences may be related to an increase of the entropy production and a decrease of the strangeness to entropy ratio in central Pb+Pb collisions in the low SPS energy range, which is consistent with the hypothesis that a transient state of deconfined matter is created above these energies. Other interpretations of the data are also discussed.
The energy dependence of the K+/PI+ ratio at y = 0 in PB PB and AU AU collisions. This table includes the present NA49 data as well as other data CT.= The commmon systematic error on the NA49 points is +-7%. including PHENIX and AGS data.
The energy dependence of the K-/PI- ratio at y = 0 in PB PB and AU AU collisions. This table includes the present NA49 data as well as other data includingPHENIX and AGS data, and preliminary E895 data.. The commmon systematic error on the NA49 points is +-7%.
The energy dependence of the ratio of the K+ to PI+ multiplicities in full phase space from PB PB and AU AU collisions. This table includes the present NA49 data as well as other data including AGS data.. The commmon systematic error on the NA49 points is +-7%.
Differential cross sections for quasi-free Compton scattering from the proton and neutron bound in the deuteron have been measured using the Glasgow/Mainz tagging spectrometer at the Mainz MAMI accelerator together with the Mainz 48 cm $\oslash$ $\times$ 64 cm NaI(Tl) photon detector and the G\"ottingen SENECA recoil detector. The data cover photon energies ranging from 200 MeV to 400 MeV at $\theta^{LAB}_\gamma=136.2^\circ$. Liquid deuterium and hydrogen targets allowed direct comparison of free and quasi-free scattering from the proton. The neutron detection efficiency of the SENECA detector was measured via the reaction $p(\gamma,\pi^+ n)$. The "free" proton Compton scattering cross sections extracted from the bound proton data are in reasonable agreement with those for the free proton which gives confidence in the method to extract the differential cross section for free scattering from quasi-free data. Differential cross sections on the free neutron have been extracted and the difference of the electromagnetic polarizabilities of the neutron have been obtained to be $\alpha-\beta= 9.8\pm 3.6(stat){}^{2.1}_1.1(syst)\pm 2.2(model)$ in units $10^{-4}fm^3$. In combination with the polarizability sum $\alpha +\beta=15.2\pm 0.5$ deduced from photoabsorption data, the neutron electric and magnetic polarizabilities, $\alpha_n=12.5\pm 1.8(stat){}^{+1.1}_{-0.6}\pm 1.1(model)$ and $\beta_n=2.7\mp 1.8(stat){}^{+0.6}_{-1.1}(syst)\mp 1.1(model)$ are obtained. The backward spin polarizability of the neutron was determined to be $\gamma^{(n)}_\pi=(58.6\pm 4.0)\times 10^{-4}fm^4$.
Energy dependence of the free-proton differential cross section.
Energy dependence of the quasi-free proton differential cross section.
Energy dependence of the free neutron differential cross section.
The energy spectrum and the cross section of photonuclear interactions of 180 GeV muons in iron were measured at the CERN SPS using prototype modules of the ATLAS hadron calorimeter. The differential
Total photonuclear cross section which gives best agreement of energy loss with theory. See text of paper for details.
Beam polarization asymmetries for the p(gamma,K+)Lambda and p(gamma,K+)sigma0 reactions are measured for the first time for Egamma=1.5-2.4 GeV and 0.6<cos(theta_cm(K+))<1.0 by using linearly polarized photons at the Laser-Electron-Photon facility at SPring-8 (LEPS). The observed asymmetries are positive and gradually increase with rising photon energy. The data are not consistent with theoretical predictions based on tree-level effective Lagrangian approaches. Including the new results in the development of the models is, therefore, crucial for understanding the reaction mechanism and to test the presence of baryon resonances which are predicted in quark models but are sofar undiscovered.
Measured beam asymmetries for the reaction GAMMA P --> K+ LAMBDA for beam energy 1.5 to 1.6.
Measured beam asymmetries for the reaction GAMMA P --> K+ LAMBDA for beam energy 1.6 to 1.7.
Measured beam asymmetries for the reaction GAMMA P --> K+ LAMBDA for beam energy 1.7 to 1.8.
We report results on rho(770)^0 -> pi+pi- production at midrapidity in p+p and peripheral Au+Au collisions at sqrt(s_NN) = 200 GeV. This is the first direct measurement of rho(770)^0 -> pi+pi- in heavy-ion collisions. The measured rho^0 peak in the invariant mass distribution is shifted by ~40 MeV/c^2 in minimum bias p+p interactions and ~70 MeV/c^2 in peripheral Au+Au collisions. The rho^0 mass shift is dependent on transverse momentum and multiplicity. The modification of the rho^0 meson mass, width, and shape due to phase space and dynamical effects are discussed.
$\rho^{0}/\pi$ ratios as a function of c.m. system energy. The ratios are from measurements in $e^{+} e^{−}$ collisions at $10.45$ GeV, $29$ GeV and $91$ GeV c.m. system energy, $p$+$p$ at $6.8$ GeV, $19.7$ GeV, $27.5$ GeV, and $52.5$ GeV, Kp at $7.82$ GeV and $\pi^{-}$p at $19.6$ GeV. The errors on the ratios at $\sqrt{s_{NN}}= 200$ GeV are the quadratic sum of the statistical and systematic errors. The ratios at $\sqrt{s_{NN}}= 200$ GeV are offset from one another for clarity.
The reactions gamma p --> K+ Lambda and gamma p --> K+ Sigma0 were measured in the energy range from threshold up to a photon energy of 2.6 GeV. The data were taken with the SAPHIR detector at the electron stretcher facility, ELSA. Results on cross sections and hyperon polarizations are presented as a function of kaon production angle and photon energy. The total cross section for Lambda production rises steeply with energy close to threshold, whereas the Sigma0 cross section rises slowly to a maximum at about E_gamma = 1.45 GeV. Cross sections together with their angular decompositions into Legendre polynomials suggest contributions from resonance production for both reactions. In general, the induced polarization of Lambda has negative values in the kaon forward direction and positive values in the backward direction. The magnitude varies with energy. The polarization of Sigma0 follows a similar angular and energy dependence as that of Lambda, but with opposite sign.
Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 0.9 to 1.0 GeV.
Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 1.0 to 1.2 GeV.
Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 1.2 to 1.4 GeV.
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