0000000000161558
AUTHOR
W. Brückner
Spectra and correlations of Λ andΛ¯produced in 340-GeV/cΣ−+Cand 260-GeV/cn+Cinteractions
We have measured the production of strange baryons and antibaryons in 340-GeV/c Sigma /sup -/+C and 260-GeV/c n+C interactions. The single x/sub F/ distributions show the expected leading particle effect, and the single p/sub t//sup 2/ distributions show a distinct nonthermal behavior. The x/sub F/ distributions of Lambda - Lambda pairs indicate two different phase space distributions for the two coincident baryons. On the other hand two Lambda 's show identical distributions. Momentum conservation during the formation process may represent a significant source for the observed behavior.
Transverse momentum distributions for exclusive $\varrho^{0}$ muoproduction
We have studied transverse momentum distributions for exclusive rho(0) muoproduction on protons and heavier nuclei at 2 < Q2 < 25 GeV2. The Q2 dependence of the slopes of the p(t)2 and t' distributions is discussed. The influence of the non-exclusive background is investigated. The p(t)2-slope for exclusive events is 4.3 +/- 0.6 +/- 0.7 GeV-2 at large Q2. The p(t)2 spectra are much softer than inclusive p(t)2 spectra of leading hadrons produced in deep inelastic scattering.
Search for the exoticΞ−−(1860)resonance in340GeV∕cΣ−-nucleus interactions
We report on a high statistics search for the ${\ensuremath{\Xi}}^{\ensuremath{-}\ensuremath{-}}(1860)$ resonance in ${\ensuremath{\Sigma}}^{\ensuremath{-}}$-nucleus collisions at $340\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}∕c$. No evidence for this resonance is found in our data sample which contains 676000 ${\ensuremath{\Xi}}^{\ensuremath{-}}$ candidates above background. For the decay channel ${\ensuremath{\Xi}}^{\ensuremath{-}\ensuremath{-}}(1860)\ensuremath{\rightarrow}{\ensuremath{\Xi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}$ and the kinematic range $0.15l{x}_{F}l0.9$ we find a $3\ensuremath{\sigma}$ upper limit for the production cross section of 3.1 and $3.5\phantom{\rul…
Measurement of the proton and deuteron structure functions, F2p and F2d, and of the ratio
The muon-proton and muon-deuteron inclusive deep inelastic scattering cross sections were measured in the kinematic range 0.002 < x < 0.60 and 0.5 < Q(2) < 75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV. These results are based on the full data set collected by the New Muon Collaboration, including the data taken with a small angle trigger. The extracted values of the structure functions F-2(p) and F-2(d) are in good agreement with those from other experiments. The data cover a sufficient range of y to allow the determination of the ratio of the longitudinally to transversely polarised virtual photon absorption cross sections, R = sigma(L)/sigma(T), for 0.002 < x < 0.12. The …
Quark and gluon distributions and $\alpha_{s}$ from nucleon structure functions at low $x$
Abstract The Q2 dependence of the structure functions F2p and F2d recently measured by the NMC is compared with the predictions of perturbative QCD at next-to-leading order. Good agreement is observed, leading to accurate determinations of the quark and gluon distributions in the range 0.008 ⩽ × ⩽ 0.5. The strong coupling constant is measured from the low x data; the result agrees with previous determinations.
Measurements of $R^{d}-R^{p}$ and $R^{Ca}-R^{C}$ in deep inelastic muon scattering
Results are presented on the difference in R, the ratio of longitudinally to transversely polarised virtual photon absorption cross sections, for the deuteron and the proton. They are obtained by c ...
Exclusive ϱ0 and φ muoproduction at large Q2
Abstract Exclusive ϱ 0 and φ muoproduction on deuterium, carbon and calcium has been studied in the kinematic range 2 Q 2 2 and 40 Q 2 dependence of the cross sections, the transverse momentum distributions for the vector mesons, the decay angular distributions and, in the case of the ϱ 0 , nuclear effects. The data for 0 production are compatible with a diffractive mechanism. The distinct features of φ production are a smaller cross section and less steep p t 2 distributions than those for the 0 mesons.
The A dependence of the nuclear structure function ratios
Results are presented for six nuclei from Be to Pb on the structure function ratios F-2(A)/F-2(C)(X) and their A dependence in deep inelastic muon scattering at 200 GeV incident: muon energy. The data cover the kinematic range 0.01 < x < 0.8 with Q(2) ranging from 2 to 70 GeV2. The A dependence of nuclear structure function ratios is parametrised and compared to various models.
Precision measurement of the structure function ratiosF 2 He /F 2 D ,F 2 C /F 2 D andF 2 Ca /F 2 D
We present the structure function ratiosF2He/F2D,F2C/F2D andF2Ca/F2D measured in deep inelastic muon-nucleus scattering at an incident muon momentum of 200 GeV. The kinematic range 0.0035<x<0.65 and 0.5<Q2<90 GeV2 is covered. At lowx the three ratios are significantly smaller than unity and the size of the depletion grows with decreasingx and increasing mass numberA. At intermediatex the ratios show an enhancement of about 2% above unity for C/D and Ca/D, possibly less for He/D. There are indications of someQ2 dependence in the Ca/D data. The integrals of the structure function differencesF2A−F2D are discussed.
Precision measurement of structure function ratios for $^{6}$Li, $^{12}$C and $^{40}$Ca
The structure function ratiosF2C/F2Li,F2Ca/F2Li andF2Ca/F2C were measured in deep inelastic muonnucleus scattering at an incident muon energy of 90 GeV, covering the kinematic range 0.0085<x<0.6 and 0.8<Q2<17GeV2. The sensitivity of the nuclear structure functions to the size and mean density of the target nucleus is discussed.
Ranges of interaction in $$p\bar p$$ scattering at low energies
Thep¯ p cross sections at low energies are analysed in the framework of the optical model. It is shown that the annihilation range is closely related to the size of the proton as measured in electromagnetic and hadronic interactions. At larger distances thep¯ p interaction has the similar character as the NN one.
Measurements of the antiproton-proton elastic cross section in the beam momentum range between 180 and 600 MeV/c
The differential cross section for antiproton-proton elastic scattering has been measured for the beam momenta between 180 and 600 MeV/c. The real-to-imaginary ratio of the forward elastic scattering amplitude is derived from the Coulomb-nuclear interference. The ratio is found to be close to zero between 180 and 500 MeV/c with a minimum ofρ=−0.14 at 260 MeV/c. This result is contrary to model predictions. The phase shifts for thes-,p- andd-waves are extracted. The partial wave compositions of the elastic and inelastic cross sections have been determined. A large contribution of thep-wave is identified in the antiproton-proton interactions at small momenta.
Antiproton-Proton Cross Sections at Small Momenta
Since the startup of LEAR in 1983 we have undertaken a series of measurements of antiproton-proton cross sections for annihilation (pp → mesons)1, charge-exchange reaction (pp → nn)2, and elastic scattering (pp → pp)3,4. We have focussed our efforts of the measurements on the beam momentum range between 160 and 600 MeV/c. Our detector is optimized to handle the antiproton beam at very small momenta5. The liquid hydrogen target is placed in the vacuum tank, and the vacuum is directly connected to the beam line. The incident beam is defined by thin scintillators also placed in the vacuum. With the apparatus of these unique designs we have explored the beam momentum region below 300 MeV/c with…
Measurement of the polarization of $$\Lambda ^0 , \overline \Lambda ^0 , \Sigma ^ + $$ and ?? produced in a ?? beam of 330 GeV/c
The polarization of Lambda0 , AntiLambda0 , Sigma+ and Xi- inclusively produced in Sigma- induced interactions at 330 GeV has been measured in the experiment WA89 at CERN. This is the first measurement of polarization of baryons produced by a hyperon beam. No polarization of AntiLambda is observed, as was also the case in proton beam data. At transverse momenta of about 1~GeV/c Lambda0 and Sigma+ show little polarization, significantly lower than in the proton beam data, while Xi- have a polarization comparable to the polarization of Lambda0 produced in proton beams. The polarization of Lambda0, AntiLambda0, Sigma+ and Xi- inclusively produced in Sigma- induced interactions at 330 GeV has b…