The dissociation of virtual photons, $\gamma^{\star} p \to X p$, in events with a large rapidity gap between $X$ and the outgoing proton, as well as in events in which the leading proton was directly measured, has been studied with the ZEUS detector at HERA. The data cover photon virtualities $Q^2>2$ GeV$^2$ and $\gamma^{\star} p$ centre-of-mass energies $40<W<240$ GeV, with $M_X>2$ GeV, where $M_X$ is the mass of the hadronic final state, $X$. Leading protons were detected in the ZEUS leading proton spectrometer. The cross section is presented as a function of $t$, the squared four-momentum transfer at the proton vertex and $\Phi$, the azimuthal angle between the positron scattering plane and the proton scattering plane. It is also shown as a function of $Q^2$ and $\xpom$, the fraction of the proton's momentum carried by the diffractive exchange, as well as $\beta$, the Bjorken variable defined with respect to the diffractive exchange.
The differential cross section DSIG/DT for the LRG and the LPS data samples.
The fitted exponential slope of the T distribution as a function of X(NAME=POMERON).
The fitted exponential slope of the T distribution as a function of X(NAME=POMERON).
Differential cross sections for π − p and pp elastic scattering have been measured at incident momenta ranging from 30 to 345 GeV and in the t range 0.002 (GeV/ c ) 2 ⩽ | t | ⩽ 0.04 (GeV/ c ) 2 . From the analysis of the data, the ratio ϱ ( t = 0) of the real to the imaginary parts of the forward scattering amplitude was determined together with the logarithmic slope b of the diffraction cone.
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A high-statistics measurement of the reaction π − p→ η n; η →2 γ has been performed at the 70 GeV Serpukhov accelerator for 15, 20, 25, 30 and 40 GeV/ c incident pion momentum using the NICE set-up with its associated 648-channel hodoscope spectrometer for γ-ray detection. It is found that the spin-flip and non-spin-flip amplitudes can be parametrized, for small | t |, as exponentials with the same slopes to within a few percent. For | t | ≳ 1 (GeV/ c ) 2 there is a break in the differential cross section. In addition, the A 2 effective trajectory deviates markedly for | t | ≳ 1 GeV/ c ) 2 from the linear behaviour valid for smaller | t |.
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AT PLAB OF 25 GEV, 'REF(8)' HAS 11.0 +- 1.4 MUB WHICH COMBINED WITH THIS MEASUREMENT GIVES 11.6 +- 1.0 MUB.
AT PLAB OF 25 GEV, THE DATA HAVE BEEN COMBINED WITH THOSE OF 'REF(8)'.
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In this paper we present tables of absolute differential cross sections of elastic pp scattering together with the values of the slope parameter B and the real-part parameter α, where B= d d t In dσ d t α= Re A(0) Im A(0) and A (0) is the amplitude of elastic pp scattering at t = 0. The cross-section data have been obtained at the Serpukhov accelerator from 8 to 70 GeV in the | t |-range 0.0007 − 0.12 (GeV/ c ) 2 .
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Differential cross sections for charge exchange π − p → π 0 n have been measured for momenta up to 50 GeV/ c . The cross section falls as a power of energy. The forward scattering cone shrinks with increasing energy. The cross section for charge exchange at zero angle drops with momentum as P −0.81±0.05 . The charge exchange cross section in the region of the second maximum decrease as P −2.8±0.1 . The ϱ trajectory is described by a linear function α ( t ) = 0.56 + 0.97 t in the interval 0 < − t -<1.5 (GeV/ c ) 2 .
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Differential cross sections for π − p → η 0 n, η 0 → 2 γ have been measured from 20 to 50 GeV for four-momentum transfers − ≲ 3 (GeV/ c ) 2 . The cross sections decrease as a power of momentum and the forward scattering cone shrinks slowly. The parameters of the A 2 trajectory, which is considerably non-linear, have been determined.
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