We present the midrapidity charged pion invariant cross sections and the ratio of $\pi^-$-to-$\pi^+$ production ($5<p_T<13$ GeV/$c$), together with the double-helicity asymmetries ($5<p_T<12$ GeV/$c$) in polarized $p$$+$$p$ collisions at $\sqrt{s} = 200$ GeV. The cross section measurements are consistent with perturbative calculations in quantum chromodynamics within large uncertainties in the calculation due to the choice of factorization, renormalization, and fragmentation scales. However, the theoretical calculation of the ratio of $\pi^-$-to-$\pi^+$ production when considering these scale uncertainties overestimates the measured value, suggesting further investigation of the uncertainties on the charge-separated pion fragmentation functions is needed. Due to cancellations of uncertainties in the charge ratio, direct inclusion of these ratio data in future parameterizations should improve constraints on the flavor dependence of quark fragmentation functions to pions. By measuring charge-separated pion asymmetries, one can gain sensitivity to the sign of $\Delta G$ through the opposite sign of the up and down quark helicity distributions in conjunction with preferential fragmentation of positive pions from up quarks and negative pions from down quarks. The double-helicity asymmetries presented are sensitive to the gluon helicity distribution over an $x$ range of $\sim$0.03--0.16.
Invariant cross section for $\pi^+$ and $\pi^-$ hadrons, as well as the statistical and systematic uncertainties. In addition, there is an absolute scale uncertainty of 9.6$\%$.
Double-helicity asymmetries and statistical uncertainties for $\pi^+$ and $\pi^-$ hadrons. The primary systematic uncertainties, which are fully correlated between points, are $1.4\times10^{-3}$ from relative luminosity and a $^{+7.0\%}_{-7.7\%}$ scaling uncertainty from beam polarization.
Ratio of charged pion cross section, as shown in Fig.6.
Charged current scattering of \nu_\mu on ^{12}C has been studied using a \pi^+ decay-in-flight \nu_\mu beam at the Los Alamos Neutron Science Center. A sample of 66.9+-9.1 events satisfying criteria for the exclusive reaction ^{12}C(\nu_\mu,\mu^-)^{12}N_{g.s.} was obtained using a large liquid scintillator neutrino detector. The observed flux-averaged cross section (5.6+-0.8+-1.0) x 10^{-41} cm^2 agrees well with reliable theoretical expectations. A measurement was also obtained for the inclusive cross section to all accessible ^{12}N states ^{12}C(\nu_\mu,\mu^-)X. This flux-averaged cross section is (10.6+-0.3+-1.8) x 10^{-40} cm^2 which is lower than present theoretical calculations.
Measured Quasi-Elastic total cross section.
Integral cross sections for the scattering of pions by protons into angles greater than 30° (lab) have been measured at a wide range of energies spanning the delta resonance using liquid hydrogen targets. Cross sections were measured for π+p scattering at 40 energies from 39.8 to 283.9 MeV and for π−p at 15 energies from 80.0 to 283.9 MeV. Comparisons with phase shift predictions from the Karlsruhe group show good agreement on resonance but significant deviations below 100 MeV.
The uncertainties shown include statistical and systematic contributions.
The uncertainties shown include statistical and systematic contributions.
Total reaction cross sections, σR, of 20–60A MeV He4,6,8, Li6–9,11, and Be10 were measured by injecting magnetically separated, focused, monoenergetic, identified secondary beams of those projectiles into a Si detector telescope and measuring their energy-deposition spectra. These σR’s, accurate to about 3%, were compared with predictions of optical, strong absorption, and microscopic models. The latter gave the best overall fit to the data, providing long-tailed matter densities were assumed. The best available optical potentials generally overpredicted the data by about 10%. Strong absorption calculations, in which the isospin-dependent term is quite important, were often unsuccessful, especially for projectiles with large neutron excess. Two-neutron removal cross sections were measured for He6 and Li11; the Li11 data were slightly overpredicted by a microscopic model which includes correlation effects for the Li11 valence neutrons. Both 2n and 4n removal from He8 were observed, in about a 2:1 ratio. Subtraction analysis of the data indicates that He4 is a good core within He6 and He8, as is Li9 within Li11. © 1996 The American Physical Society.
Axis error includes +- 3/3 contribution (Statistical uncertainty is negligible).
Axis error includes +- 3/3 contribution (Statistical uncertainty is negligible).
Axis error includes +- 3/3 contribution (Statistical uncertainty is negligible).
A search for charm production in the coherent diffractive dissociation reaction pSi→XSi was carried out for the modes D 0 → K − π + , D 0 → K − π + π + π − , and D + → K − π + π + . No charm signals were observed, and the 90% confidence level upper limit for coherent charm pair production was determined to be 26 μ b per silicon nucleus. The results are interpreted as an upper limit of 0.2% on the amount of intrinsic charm in the proton.
90 pct CL upper limits.
We report on the production characteristics and total cross section for 9 beauty hadron pairs produced by a 600 GeV/ c π − beam, the first such information in this energy region. The events were detected in the hybrid emulsion spectrometer of Fermilab Experiment E653. The measured pair cross section for all χ F , assuming linear A dependence, is 33±11 (stat.)±6(syst.) nb/nucleon. Fits of the inclusive single-hadron production distribution to the forms d σ d χ F ∝ (1−|χ F −χ 0 |) n and d σ d p T 2 ∝ exp (−bp t 2 ) give n=5.0 −2.1−1.7 +2.7+1.7 , χ 0 =0.06 −0.07−0.03 +0.06+0.02 , and b=0.13 −0.04−0.02 +0.05+0.02 ( GeV /c −2 . .The pairs tend to be produced back-to-back.
Cross section over all x assuming A**1 nuclear dependence.
Fit to data of form dsig/dx ^ (1-ABS(X-X0))**N yields X0 = 0.06 +0.06,-0.07(DSYS=+0.02,-0.03) and N = 5.0 +2.7,-2.1(DSYS=+-1.7).
Fit to data of form dsig/dPT**2 ^ exp(-B*PT**2) yields B = 0.13 +0.05,-0.04(DSYS=+-0.02).
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The cross section per nucleon is evaluated with assumption of the linear atomic number dependence. SIG(C=NEUTRINO) and SIG(C=ANTINEUTRINO) are corresponded to the NUMU and NUMUBAR data, respectevly. CLOOP-OVER.
We present total and differential cross sections for charm mesons produced in 600 GeV/ c π - emulsion interactions. Fits to d 2 σ / dx F dp T 2 ∞ (1−| x F |) n exp (- bp T 2 ) for 676 electronically reconstructed D mesons with x F >0 give n =4.25±0.24 ( stat .)±0.23 ( syst .) and b =0.76±0.03±0.03 ( GeV / c ) -2 . The total inclusive D + and D 0 cross sections are σ ( π - N → D ± ; x F >0) = 8.66±0.46±1.96 μb nucleon and σ(π - N→D 0 D 0 ; x F >0)=22.05±1.37±4.82μb nucleonk, where a linear dependence on the mean atomic weight of the target is assumed. These results are compared to next-to-leading order QCD predictions.
Linear A-dependence. Different modes of the charm mesons detection were used (see text for detail). The differential cross section is fitted by the equation : D2(SIG)/D(XL)/D(PT**2) = CONST*(1-XL)**POWER*EXP(-SLOPE*PT**2).
Linear A-dependence.
We report results on D 0 and D + production in proton-emulsion interactions at s =38.7 GeV. A fit to the form (1−| x F |) n exp (−bp 2 T ) yields n=6.9 +1.9 −1.8 and b=0.84 +0.10 −0.08 (GeV/ c ) −2 . The total inclusive cross section, is assuming linear A dependence, is measured to be 38±3(stat.) ±13 (sys.) μ b for the D 0 and 38±9±14 μ b for the D + . A comparison of these results with previous measurements indicates that nuclear effects do not strongly influence charm production. The predictions of QCD are in good agreement with our data.
The differential cross section is fitted by the equation : D2(SIG)/D(XL)/D(PT**2) = CONST*(1-XL)**POWER*EXP(-SLOPE*PT**2).
The differential cross section is fitted by the equation : D2(SIG)/D(XL)/D(PT**2) = CONST*(1-XL)**POWER*EXP(-SLOPE*PT**2).
Linear A-dependence. Different modes of the charm mesons detection were used (see text for detail).
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