Results are reported on the reaction p p → π + π + π − π − π 0 at six lab momenta spanning the region from 0.686 to 1.098 GeV/ c . The cross section for this process drops from 20.3 ± 1.2 mb at 0.686 GeV/ c to 13 1.0 mb at 1.098 GeV/ c . Resonance production is determined by means of a model which includes Bose symmetrization, Breit-Wigner amplitudes and Bose-Einstein correlations for the like-charged pion pairs in the nonresonant part of the amplitude. The likelihood fit to the resonance channels yields about 0.8% ηππ , 12% ϱ ± πππ , 2% f πππ , 8% ω ππ , 22% ϱ ± ϱ 0 π , 13% ωϱ 0 and 9% ω f with errors on the order of a few percent. Several percent A 1 ± ππ and X(1440) π were also needed to obtain good fits. The ϱ 0 πππ and ϱ 0 ϱ 0 π channels as well as A 2 ππ and A 1 0 ππ are consistent with zero. Reasonable fits to the mass distributions are obtained. Production angular distributions are found to be essentially uniform. The angular correlations between pion pairs are approximately fit by the simple model of resonance production with Bose symmetrization.
Axis error includes +- 0.0/0.0 contribution.
Axis error includes +- 0.0/0.0 contribution.
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 K ∗ (∼45%) and ϱ 0 (∼20%) production, with smaller amounts of A 2 0 (∼15%) and ϕ (∼5%) production. 25% of the reactions involved double resonance production. No significant three-body resonance production is observed.
ERRORS INCLUDE SYSTEMATICS.
The kaon electroproduction reaction 1H(e,e'K+)Lambda was studied as a function of the virtual-photon four-momentum, Q2, total energy, W, and momentum transfer, t, for different values of the virtual- photon polarization parameter. Data were taken at electron beam energies ranging from 3.40 to 5.75 GeV. The center of mass cross section was determined for 21 kinematics corresponding to Q2 of 1.90 and 2.35 GeV2 and the longitudinal, sigmaL, and transverse, sigmaT, cross sections were separated using the Rosenbluth technique at fixed W and t. The separated cross sections reveal a flat energy dependence at forward kaon angles not satisfactorily described by existing electroproduction models. Influence of the kaon pole on the cross sections was investigated by adopting an off-shell form factor in the Regge model which better describes the observed energy dependence of sigmaT and sigmaL.
Measured values of the separated cross section at Q**2 = 2.35 GeV**2 and W = 1.85 GeV.. Errors contain both statistics and systematics.
Measured values of the separated cross section at Q**2 = 1.90 GeV**2.. Errors contain both statistics and systematics.
Measured values of the separated cross section at Q**2 = 2.35 GeV**2.. Errors contain both statistics and systematics.
The process $ep \to e^{\prime}p^{\prime}\pi^0$ has been measured at $Q^2$ = 6.4 and 7.7 \ufourmomts in Jefferson Lab's Hall C. Unpolarized differential cross sections are reported in the virtual photon-proton center of mass frame considering the process $\gamma^{\ast}p \to p^{\prime}\pi^0$. Various details relating to the background subtractions, radiative corrections and systematic errors are discussed. The usefulness of the data with regard to the measurement of the electromagnetic properties of the well known $\Delta(1232)$ resonance is covered in detail. Specifically considered are the electromagnetic and scalar-magnetic ratios $R_{EM}$ and $R_{SM}$ along with the magnetic transition form factor $G_M^{\ast}$. It is found that the rapid fall off of the $\Delta(1232)$ contribution continues into this region of momentum transfer and that other resonances
Differential cross sections at Q**2=6.564 GeV**2, EPSILON=0.4523, W=1.112 GeV and COS(THETA(*))=-0.9 for the small SOS spectrometer.
Differential cross sections at Q**2=6.564 GeV**2, EPSILON=0.4523, W=1.112 GeV and COS(THETA(*))=-0.7 for the small SOS spectrometer.
Differential cross sections at Q**2=6.564 GeV**2, EPSILON=0.4523, W=1.112 GeV and COS(THETA(*))=-0.5 for the small SOS spectrometer.
We report results for the virtual photon asymmetry $A_1$ on the nucleon from new Jefferson Lab measurements. The experiment, which used the CEBAF Large Acceptance Spectrometer and longitudinally polarized proton ($^{15}$NH$_3$) and deuteron ($^{15}$ND$_3$) targets, collected data with a longitudinally polarized electron beam at energies between 1.6 GeV and 5.7 GeV. In the present paper, we concentrate on our results for $A_1(x,Q^2)$ and the related ratio $g_1/F_1(x,Q^2)$ in the resonance and the deep inelastic regions for our lowest and highest beam energies, covering a range in momentum transfer $Q^2$ from 0.05 to 5.0 GeV$^2$ and in final-state invariant mass $W$ up to about 3 GeV. Our data show detailed structure in the resonance region, which leads to a strong $Q^2$--dependence of $A_1(x,Q^2)$ for $W$ below 2 GeV. At higher $W$, a smooth approach to the scaling limit, established by earlier experiments, can be seen, but $A_1(x,Q^2)$ is not strictly $Q^2$--independent. We add significantly to the world data set at high $x$, up to $x = 0.6$. Our data exceed the SU(6)-symmetric quark model expectation for both the proton and the deuteron while being consistent with a negative $d$-quark polarization up to our highest $x$. This data setshould improve next-to-leading order (NLO) pQCD fits of the parton polarization distributions.
A1 and g1/F1 for the P target at incident energy 1.6000 GeV and W = 1.1300 GeV.
A1 and g1/F1 for the P target at incident energy 1.6000 GeV and W = 1.1500 GeV.
A1 and g1/F1 for the P target at incident energy 1.6000 GeV and W = 1.1700 GeV.
The differential cross section for the gamma +n --> pi- + p and the gamma + p --> pi+ n processes were measured at Jefferson Lab. The photon energies ranged from 1.1 to 5.5 GeV, corresponding to center-of-mass energies from 1.7 to 3.4 GeV. The pion center-of-mass angles varied from 50 degree to 110 degree. The pi- and pi+ photoproduction data both exhibit a global scaling behavior at high energies and high transverse momenta, consistent with the constituent counting rule prediction and the existing pi+ data. The data suggest possible substructure of the scaling behavior, which might be oscillations around the scaling value. The data show an enhancement in the scaled cross section at center-of-mass energy near 2.2 GeV. The differential cross section ratios at high energies and high transverse momenta can be described by calculations based on one-hard-gluon-exchange diagrams.
Differential cross section for the process GAMMA N --> PI- P for an incident electron energy of 5.614 GeV.
Differential cross section for the process GAMMA N --> PI- P for an incident electron energy of 4.236 GeV.
Differential cross section for the process GAMMA N --> PI- P for an incident electron energy of 3.400 GeV.
We report on precision measurements of the elastic cross section for electron-proton scattering performed in Hall C at Jefferson Lab. The measurements were made at 28 unique kinematic settings covering a range in momentum transfer of 0.4 $<$ $Q^2$ $<$ 5.5 $(\rm GeV/c)^2$. These measurements represent a significant contribution to the world's cross section data set in the $Q^2$ range where a large discrepancy currently exists between the ratio of electric to magnetic proton form factors extracted from previous cross section measurements and that recently measured via polarization transfer in Hall A at Jefferson Lab.
Measured values of the electron-proton elastic cross section for beam energy 1.148 GeV.
Measured values of the electron-proton elastic cross section for beam energy 1.882 GeV.
Measured values of the electron-proton elastic cross section for beam energy 2.235 GeV.
Exclusive electroproduction of pi0 mesons on protons in the backward hemisphere has been studied at Q**2 = 1.0 GeV**2 by detecting protons in the forward direction in coincidence with scattered electrons from the 4 GeV electron beam in Jefferson Lab's Hall A. The data span the range of the total (gamma* p) center-of-mass energy W from the pion production threshold to W = 2.0 GeV. The differential cross sections sigma_T+epsilon*sigma_L, sigma_TL, and sigma_TT were separated from the azimuthal distribution and are presented together with the MAID and SAID parametrizations.
Cross section SIG(T) + EPSILON*SIG(L) for COS(THETA*) = -0.975.
Cross section SIG(T) + EPSILON*SIG(L) for COS(THETA*) = -0.925.
Cross section SIG(T) + EPSILON*SIG(L) for COS(THETA*) = -0.875.
We have measured the differential cross section for the gamma n --> pi- p and gamma p --> pi+ n reactions at center of mass angle of 90 degree in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at photon energies greater than 3.3 GeV exhibit a global scaling behavior for both pi- and pi+ photoproduction, consistent with the constituent counting rule and the existing pi+ photoproduction data. Possible oscillations around the scaling value are suggested by these new data The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive pi- to pi+ photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.
Differential cross section at THETA(CM) = 90 degrees.
Measurements of the deuteron elastic magnetic structure function B(Q2) are reported at squared four-momentum transfer values 1.20≤Q2≤2.77 (GeV/c)2. Also reported are values for the proton magnetic form factor GMp(Q2) at 11 Q2 values between 0.49 and 1.75 (GeV/c)2. The data were obtained using an electron beam of 0.5 to 1.3 GeV. Electrons backscattered near 180° were detected in coincidence with deuterons or protons recoiling near 0° in a large solid-angle double-arm spectrometer system. The data for B(Q2) are found to decrease rapidly from Q2=1.2 to 2 (GeV/c)2, and then rise to a secondary maximum around Q2=2.5 (GeV/c)2. Reasonable agreement is found with several different models, including those in the relativistic impulse approximation, nonrelativistic calculations that include meson-exchange currents, isobar configurations, and six-quark configurations, and one calculation based on the Skyrme model. All calculations are very sensitive to the choice of deuteron wave function and nucleon form factor parametrization. The data for GMp(Q2) are in good agreement with the empirical dipole fit.
The measured cross section have been devided by those obtained using the dipole form for the proton form factors: G_E=1/(1+Q2/0.71)**2, G_E(Q2)=G_M(Q2)/mu,where Q2 in GeV2, mu=2.79.
Axis error includes +- 0.0/0.0 contribution (?////Errors given are the statistical errors and systematic uncertainties add ed in quadreture).
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