We present a total of 427 np analyzing power data points in a large angular interval at 12 energies between 0.312 and 1.10 GeV. The SATURNE II polarized beam of free monochromatic neutrons was scattered either on the Saclay frozen-spin polarized proton target or on CH 2 and C targets. Present results are compared with existing elastic and quasieleastic data.
Results of the analyzing power for n p scattering at 0.312 GeV. The CH2 target was used.
Results of the analyzing power for n p scattering at 0.363 GeV. The CH2 target was used.
Results of the analyzing power for n p scattering at 0.800 GeV.
Parity nonconservation in proton-proton scattering has been studied by measuring the angle-integrated longitudinal analyzing power A z . We found A z (13.6 MeV)=(−1.5±0.5)×10 −7 . The error includes uncertainties due to statistics and corrections, as well as upper limits on systematic effects. The experimental result is discussed with respect to recent theoretical calculations.
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The polarization parameter in pn elastic scattering has been measured at 24 GeV/ c over the range of four-momentum transfer squared 0.1 < | t | < 1.25 (GeV/ c ) 2 , and found to be negative except for a zero at | t | = 0.65 (GeV/ c ) 2 .
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We have measured the analyzing power A y in n-d elastic scattering at 67.0 MeV. The experiment was based on the detection of recoil deuterons, allowing for a precise measurement of the backward angular range. The results are in good agreement with recent three-nucleon calculations which are based on the Paris and Bonn NN potentials.
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The analysing powers in free →n p forward elastic scattering have been measured for incident neutron energies of 633, 784, 834, 934 and 985 MeV, and for momentum transfer 0.01 < ‖ t ‖ < 0.10 ( GeV / c ) 2 . The experiment used a recoil detector ionisation chamber which served at the same time as a gas target, and scintillation counters to measure the asymmetry of the scattered neutrons.
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An experiment resulting in the first measurement of the isospin-mixing, charge-symmetry-violating component of the n−p interaction has been performed. The experiment determined the difference in the angles of the zero crossing of the neutron and proton analyzing powers An and Ap at 477 MeV. In terms of the laboratory scattering angle of the neutron, the measured difference is θ0n(An)−θ0n(Ap)=+0.13° ±0.06° (±0.03°), where the second error is a worst-case estimate of systematic error. The resulting difference in the analyzing powers at the zero-crossing angle is An−Ap=+0.0037 ±0.0017 (±0.0008).
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The DIS diffractive cross section, $d\sigma^{diff}_{\gamma^* p \to XN}/dM_X$, has been measured in the mass range $M_X < 15$ GeV for $\gamma^*p$ c.m. energies $60 < W < 200$ GeV and photon virtualities $Q^2 = 7$ to 140 GeV$^2$. For fixed $Q^2$ and $M_X$, the diffractive cross section rises rapidly with $W$, $d\sigma^{diff}_{\gamma^*p \to XN}(M_X,W,Q^2)/dM_X \propto W^{a^{diff}}$ with $a^{diff} = 0.507 \pm 0.034 (stat)^{+0.155}_{-0.046}(syst)$ corresponding to a $t$-averaged pomeron trajectory of $\bar{\alphapom} = 1.127 \pm 0.009 (stat)^{+0.039}_{-0.012} (syst)$ which is larger than $\bar{\alphapom}$ observed in hadron-hadron scattering. The $W$ dependence of the diffractive cross section is found to be the same as that of the total cross section for scattering of virtual photons on protons. The data are consistent with the assumption that the diffractive structure function $F^{D(3)}_2$ factorizes according to $\xpom F^{D(3)}_2 (\xpom,\beta,Q^2) = (x_0/ \xpom)^n F^{D(2)}_2(\beta,Q^2)$. They are also consistent with QCD based models which incorporate factorization breaking. The rise of $\xpom F^{D(3)}_2$ with decreasing $\xpom$ and the weak dependence of $F^{D(2)}_2$ on $Q^2$ suggest a substantial contribution from partonic interactions.
Cross section for diffractive scattering.
Cross section for diffractive scattering.
Cross section for diffracitve scattering.
The diffractive dissociation of a 200-GeV/c π− beam into KS0KS0π+π−π− has been observed. The diffractive KS0KS0π+π−π− cross section is 1.59±0.78 μb. The ratio of the diffractive KS0KS0π+π−π− cross section to the diffractive KS0KS0π− cross section is 0.40±0.13, which is in good agreement with a diffractive-fragmentation-model prediction of 0.36. There is evidence for simultaneous production of K*− and K*+ in the diffractive KS0KS0π+π−π− sample. The K*+−KS0π−+ mass distribution shows an enhancement near 1.95 GeV.
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We report the first observation of diffractively produced open charm in 800−GeV/c pp collisions of the type pp→pD*X. We measure cross sections of σdiff(D*+)=(0.185±0.044±0.054)μb and σdiff(D*−)=(0.174±0.034±0.029)μb. Our measurements are based on 4.3×109 events recorded by FNAL E690 in the fixed-target run of 1991. We compare our results with previous fixed-target charm experiments.
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