Using a data sample of 6.8 pb$^{-1}$ collected with the CMD-3 detector at the VEPP-2000 $e^+e^-$ collider we select about 2700 events of the $e^+e^- \to p\bar{p}$ process and measure its cross section at 12 energy ponts with about 6\% systematic uncertainty. From the angular distribution of produced nucleons we obtain the ratio $|G_{E}/G_{M}| = 1.49 \pm 0.23 \pm 0.30$.
The c.m. energy, beam energy shift, luminosity, number of selected $e^+e^- \to p\bar{p}$ events, detection efficiency, radiative correction, and cross section with statistical and systematic errors. The data for collinear type events.
The c.m. energy, luminosity, number of signal events, fraction of antiprotons stopped in beam pipe and DC inner shell, efficiency, cross section with statistical and systematic errors, for annihilation events.
The process $e^+e^- \to K^+K^-\pi^+\pi^-$ has been studied in the center-of-mass energy range from 1500 to 2000\,MeV using a data sample of 23 pb$^{-1}$ collected with the CMD-3 detector at the VEPP-2000 $e^+e^-$ collider. Using about 24000 selected events, the $e^+e^- \to K^+K^-\pi^+\pi^-$ cross section has been measured with a systematic uncertainty decreasing from 11.7\% at 1500-1600\,MeV to 6.1\% above 1800\,MeV. A preliminary study of $K^+K^-\pi^+\pi^-$ production dynamics has been performed.
Center-of-mass energy, integrated luminosity, number of four-track events, number of three-track events, detection efficiency, radiative correction and Born cross section of the process $e^{+}e^{-} \to K^{+} K^{-} \pi^{+} \pi^{-}$. Errors are statistical only.
Total and differential cross sections are presented for proton-antiproton annihilation into π+π− and K+K− at six laboratory momenta between 686 and 1098 MeV/c. The two-pion final state displays moderate energy dependence in its differential cross section, but shows no evidence of any direct-channel resonances. In contrast, the two-kaon final state exhibits some behavior in the total and differential cross section suggestive of a possible direct-channel effect between 800 and 1000 MeV/c.
NOTE CUT EXCLUDES LARGE FORWARD CROSS SECTION.
LEGENDRE COEFFICIENTS NORMALIZED TO LEGN(L=0) = 0.5.
LEGENDRE COEFFICIENTS NORMALIZED TO LEGN(L=0) = 0.5.
We have measured the cross sections for these reactions and the cross sections of resonances produced in them. The production of Y ∗± (1385) , ϱ o (765), and f o (1260) is observed in the first reaction; ϱ o (765) in the second; Y ∗−,o (1385), ω o (748), B − (1235), probably ϱ o,− (765), and an enhancement we interpret to be the J P = 1 2 − Σ o (1750) in the third. Single particle longitudinal momentum distributions and average values of transverse momentum are presented. The observed single particle production angular distributions show good qualitative but not quantitative agreement with the Reggeized multiperipheral model of Chan, Loskiewicz, and Allison. We found strong disagreement between the amounts of observed resonance production and the results of the multiperipheral model of Plahte and Roberts that is based on the models of Chan et al. and Veneziano. However, we included isospin effects only in an approximate manner.
No description provided.
Resonance production in the above reactions containing a proton in the final state is characterized primarily by the production of K ∗− (890). The events with a final state neutron are characterized by the production of either K ∗− (890) or Δ − (1236), but very little double resonance production. Cross sections are presented. Exponential slopes for the momentum-transfer distributions of the K ∗− (890) and Δ − (1236) were determined and found to be much smaller than for elastic scattering. For the π − π − p K 0 events the spin density matrix elements for the decay of the K ∗− (890) in the Jackson frame imply alignment. Single particle longitudinal momentum distributions and average values of transverse momentum are presented. The single particle production angular distributions of all three reactions were compared with the results of the Reggeized multiperipheral model of Chan, Loskiewicz, and Allison (CLA) modified to include resonance production. Good qualitative agreement was found. The data from the π − π − p K 0 events were also compared with a multiperipheral model of Plahte and Roberts that is based on the CLA and Veneziano models.
No description provided.
Differential cross sections are presented for pion-proton elastic scattering in the angular range −0.6≳cosθc.m.≳−0.98 at 15 incident π+ momenta from 2.18−5.25 GeVc. The angular distributions rise steeply near 180° at all momenta. For laboratory momenta ≳2.75 GeVc they show a minimum at u≈−0.17 (GeVc)2 and a broad maximum near u≈−0.6 (GeVc)2. When the data are plotted versus s, for fixed u, a strong signal from the Δ(2420) resonance is observed. The data are compared with a direct-channel resonance model and with a Regge model which considers the exchange of the Nα, Nγ, and Δδ Regge trajectories. The qualitative success of both the direct-channel resonance model and the Regge model lends support to the concept of duality.
No description provided.
No description provided.
No description provided.
This paper presents differential cross sections for backward π−p elastic scattering in the angular region −0.55≥cosθc.m.≥−0.98 for five incident momenta: 2.38, 2.50, 2.65, 2.80, and 3.00 GeV/c. The structure of the angular distribution undergoes a marked change over this momentum interval. A pronounced dip near 180°, which is seen for momenta ≲2.50 GeV/c, becomes a sharp peak at 2.80 and 3.00 GeV/c. A minimum in the cross section at cosθc.m.≃−0.7 is indicated at all momenta. In addition, a dip in the differential cross section appears at cosθc.m.≃−0.92 at 3.00 GeV/c. A good fit to the data from 2.1 to 3.0 GeV/c is obtained with a direct-channel resonance model.
No description provided.
No description provided.
No description provided.
The differential cross sections for γp→γp and γp→π0p have been measured for incident photon energies in the range of 2 to 6 GeV and for |t| ranging from 0.7 to 4.3 GeV2. This corresponds to a center-of-mass angle range of 45° to 128°. The energy dependence of the data is compared to that predicted by several parton models.
No description provided.
No description provided.
No description provided.
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.
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