The cross section for the reaction $ e p \to e^{\prime} p \pi^{+} \pi^{-}$ was measured in the resonance region for 1.4$<$W$<$2.1 GeV and 0.5$<Q^{2}<$1.5 GeV$^{2}$/c$^{2}$ using the CLAS detector at Jefferson Laboratory. The data shows resonant structures not visible in previous experiments. The comparison of our data to a phenomenological prediction using available information on $N^{*}$ and $\Delta$ states shows an evident discrepancy. A better description of the data is obtained either by a sizeable change of the properties of the $P_{13}$(1720) resonance or by introducing a new baryon state, not reported in published analyses.
Measured cross section DSIG/DM(PI+PI-) for the W range 1400 to 1425GeV.
Measured cross section DSIG/DM(PI+PI-) for the W range 1425 to 1450GeV.
Measured cross section DSIG/DM(PI+PI-) for the W range 1450 to 1475GeV.
The differential cross section, $d\sigma/dt$ for $\omega$ meson exclusive photoproduction on the proton above the resonance region ($2.6<W<2.9$ GeV) was measured up to a momentum transfer $-t = 5$ GeV$^2$ using the CLAS detector at Jefferson Laboratory. The $\omega$ channel was identified by detecting a proton and $\pi^+$ in the final state and using the missing mass technique. While the low momentum transfer region shows the typical diffractive pattern expected from Pomeron and Reggeon exchange, at large $-t$ the differential cross section has a flat behavior. This feature can be explained by introducing quark interchange processes in addition to the QCD-inspired two-gluon exchange.
Differential cross section in the energy region 3.20 to 3.38 GeV.
Differential cross section in the energy region 3.38 to 3.56 GeV.
Differential cross section in the energy region 3.56 to 3.74 GeV.
Using the HERA-B detector, the b-bbar production cross section has been measured in 920 GeV proton collisions on carbon and titanium targets. The b-bbar production was tagged via inclusive bottom quark decays into J/psi, by exploiting the longitudinal separation of J/psi->ll decay vertices from the primary proton-nucleus interaction. Both $e^+e^-$ and $\mu^+\mu^-$ channels have been reconstructed and the combined analysis yields the cross section $\sigma(b \bar b) = 32 ^{+14}_{-12} (stat) ^{+6}_{-7} (sys) nb/nucleon$.
The measured cross section for the E+ E- and MU+ MU- channels separately.
The measured and extrapolated combined B-BBAR production cross section.
First data on coherent threshold \pi^0 electroproduction from the deuteron taken by the A1 Collaboration at the Mainz Microtron MAMI are presented. At a four-momentum transfer of q^2=-0.1 GeV^2/c^2 the full solid angle was covered up to a center-of-mass energy of 4 MeV above threshold. By means of a Rosenbluth separation the longitudinal threshold s wave multipole and an upper limit for the transverse threshold s wave multipole could be extracted and compared to predictions of Heavy Baryon Chiral Perturbation Theory.
Differential cross-section d(SIG(PI0))/d(OMEGA) is related to electron-deuteron one by the relation as follows: d(SIG)/d(OMEGA_e)/d(E_e)/d(OMEGA) = Gamma *d(SIG)/d(OMEGA), where the virtual photon flux is give by: Gamma = (alpha/2*pi**2) * (E'/E) * (k_gamma/Q2) / (1-epsilon). Here epsilon is transverse degree of polarization of the virtual photon. See article for details.
Differential cross-section d(SIG(PI0))/d(OMEGA) is related to electron-deuteron one by the relation as follows: d(SIG)/d(OMEGA_e)/d(E_e)/d(OMEGA) = Gamma *d(SIG)/d(OMEGA), where the virtual photon flux is give by: Gamma = (alpha/2*pi**2) * (E'/E) * (k_gamma/Q2) / (1-epsilon). Here epsilon is transverse degree of polarizatiuon of the virtual photon. See article for details.
Differential cross-section d(SIG(PI0))/d(OMEGA) is related to electron-deuteron one by the relation as follows: d(SIG)/d(OMEGA_e)/d(E_e)/d(OMEGA) = Gamma *d(SIG)/d(OMEGA), where the virtual photon flux is give by: Gamma = (alpha/2*pi**2) * (E'/E) * (k_gamma/Q2) / (1-epsilon). Here epsilon is transverse degree of polarizatiuon of the virtual photon. See article for details.
Inclusive cross sections and one-particle inclusive spectra are given for neutral K, Λ and Λ produced in K − p and K + p interactions at 32 GeV/ c in the 4.5 m Mirabelle hydrogen bubble chamber at the Serpukhov accelerator. Cross sections for associated production are also given, and the energy dependences of the cross sections and of the x distributions in the central and in the fragmentation regions are discussed.
No description provided.
No description provided.
The differential cross section d σ d t′ for the charge-exchange process π + p → π 0 ( π + p) at 8, 16 and 23 GeV/ c is presented for several regions of the π + p effective mass. It is found that the dip at t ′ ≈ 0.6 (GeV/ c ) 2 which is observed in the Δ(1236) mass band becomes a less pronounced structure in the higher mass regions. However, while the slope of the d σ d t′ distributions in the near-forward direction decreases strongly with increasing π + p mass, there is no evidence that the observed structure moves to higher values of t ′ as the π + p mass increases. These results are consistent with a Regge-exchange picture where the position of the dip is determined by the exchanged trajectory, but are inconsistent with a simple geometrical picture.
TP DEPENDENCE FOR FOUR <PI+ P> MASS INTERVALS.
Twenty-nine proton-proton differential elastic cross sections for lab momenta p0 from 11 to 31.8 BeV/c, at four-momentum transfers squared, −t, from 2.3 to 24.4 (BeV/c)2, have been measured at the Brookhaven alternating gradient synchrotron. The circulating proton beam impinged upon a thin CH2 internal target. Both scattered protons from p−p elastic events were detected by scintillation-counter telescopes which were placed downstream from deflection magnets set at the appropriate angles to the incident beam. The angular correlation of the protons, their momenta, and the coplanarity of the events were determined by the detection system. The results show that at high momentum transfers the differential cross section, dσdt, depends strongly upon the energy; for −t=10 (BeV/c)2, the value of dσdt at p0=30 BeV/c is smaller by a factor∼1000 than at p0=10 BeV/c. At all energies, dσdt falls rapidly with increasing |t| for scattering angles up to about 65° (c.m.), while in the range from 65 to 90° the cross section falls only by a factor of about 2. The smallest cross section measured was 9×10−37 cm2 sr−1 (c.m.), at p0=31.8 BeV/c and −t=20.4 (BeV/c)2; this is about 3×10−12 of the zero-degree cross section at the same energy.
'1'. '2'.
Forum