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DISTRIBUTION IS PRESENTED IN THE BEAM FRAGMENTATION REGIONS.
DISTRIBUTION IS PRESENTED IN THE BEAM FRAGMENTATION REGIONS.
DISTRIBUTION IS PRESENTED IN THE BEAM FRAGMENTATION REGIONS.
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We report a high-statistics study of the reaction p+W→μ++μ−+X with use of an intense 400-GeV/c proton beam, a magnetized-iron beam dump, and a wide-acceptance detector. Using data near xF=0, we have extracted the nucleon sea-quark distribution and find it to be a factor 1.6±0.3 larger than that obtained by inelastic charged-current neutrino scattering. We then compare the Drell-Yan prediction with our data including the previously unexplored region of large xF and find excellent agreement for a wide range of μ-pair invariant mass.
Dimuon mass mass distribution at XFP=0.1.
Dimuon production for varying mass as function of XFP.
Dimuon production for varying mass as function of XFP.
The reaction π − p→ π 0 ηn ↳2y ↳2y has been analyzed using data of an experimental performed at the 70 GeV accelerator, with the NICE 648 channel hodoscope spectrometer for γ ray detection. Events with 4 γ seen are used for the analysis. A method is applied, which allows the determination of the number of π 0 η events for each mass, cos θ GJ and t bin. Mass spectra, t distributions and decay angular distributions for the π 0 η system are presented. The cross section for the production of A 2 0 is found to be 2.7 ± 1.1 μ b at 40 GeV/ c beam momentum. No indication of a resonant 1 − state in the π 0 η system is observed, in spite of the fact that this state is allowed for the π 0 η system on the same footing as the observed 0 + and 2 + resonances.
ERROR INCLUDES UNCERTAINTIES IN SEVERAL CORRECTIONS AND IN BACKGROUND SUBTRACTION.
We present final results on the inclusive production of the\(\bar K^{*0} (890)\),K*−(890),K*0(890),K*−(890),K*−(1420), and\(\bar K^{*0} (1420)\) resonances inK−p interactions at 32 GeV/c. Total cross sections and invariantx-distributions are determined. Inclusive cross sections of\(\bar K^{*\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{o} } (890)\) amount to ≃4 mb each, of\(\bar K^{*\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{o} } (1420)\) to ≃1 mb and ofK*0(890) to ≃0.8 mb. These values are in agreement with additive quark model predictions. All strangenessS=−1 resonances are predominantly produced in the forward hemisphere, the tensor mesons being more peripherally produced than the vector ones. The\(\bar K^{*\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{o} } (890)\) density matrix elements andt-distributions are obtained. The unnatural spin-parity exchange contribution to inclusive\(\bar K^{*\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{o} } (890)\) production amounts to ≳60% at |t|<0.4 GeV2 and decreases with increasing |t|. Whenever relevant, a comparison is also made with available data at other energies.
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In a K − p experiment at 32 GeV/ c with a sensitivity of 6 ev/≈b the inclusive reaction K − p → p + X was studied in the kinematical region x < −0.3. Most of the protons in this region were identified by ionization. Correcting for losses of the very slow as well as of the fast protons in this region we obtained σ p ( x < −0.3) = 5.9 ± 0.2 mb. The double invariant differential cross sections of protons were analysed in terms of the variables x , p T 2 , and M 2 / s , t , and the contributions from separate peripheral mechanisms were analysed. A triple-Regge analysis was performed on the inclusive proton d 2 σ /d t d( M 2 / s ) distribution with | t | < 1.1 GeV 2 . The fit with an RRP term resulted in an effective trajectory for the exchanged reggeon lying somewhat lower than that for the leading meson trajectory. Inclusion in the fit of an additional ππp term showed that pion exchange is important in the triple-Regge region at small | t |.
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This Letter reports measurements of the ratios of $\pi$, K, and p production at large values of transverse momentum in $\pi^- −p$ collisions. The charge ratios, such as $\frac {\pi^−} {\pi^+}$, $\frac {K^−} {K^+}$, and $\frac {\overline{p}}{p}$ are seen to be quite different from those measured in p −p collisions. These ratios are sensitive tests of hard-scattering models, and are compared with theoretical predictions. The particle ratios have also been studied as a function of center-of-mass angle ($\theta^*$) at $\theta^*$ = 90°, 77°, and 60°.
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Lambda production is studied in K − p interactions at 32 GeV/ c . The total Λ cross section is 2.31±0.03 mb . Using the measured Λγ combinations we find that (31±4)% of all Λ's are produced via the Σ 0 → Λγ decay. About 60% of the Λ's are associated with either a N N or K K pair; about 40% of the Λ's are produced through the hypercharge annihiltion reaction K − p→ Λ + π 'a. The two-peak structure of the invariant x distribution can be related to fragmentation processes. The Λ is found to be unpolarized in the target fragmentation region, whereas a transverse polarization is observed for forward produced Λ's. As a function of p ⊥, a polarization effect is measured at medium p ⊥.
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The depolarization parameter for pp inclusive scattering at an incident momentum of 6 GeV/c was measured. The D parameter for inclusive scattering indicates the dominance of natural-parity exchange at small t, except in the case of N*(1232) production, where π exchange is more important. D for elastic scattering has also been measured. This parameter shows a small decrease from unity with increasing momentum transfer.
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The large-angle analyzing power A in proton-neutron elastic scattering at 2, 3, and 6 GeV/c with use of the polarized proton beam at the Argonne zero-gradient synchrotron and a liquid deuterium target have been measured. The measurements, the first at high energy, show that A is large (20-40%) and negative over much of the angular range and shows no decrease with incident energy, unlike the earlier data at smaller angles.
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