Observation of multiparton interactions in proton-nucleus collisions at 70 GeV

The production of noncoplanar hadron pairs in proton-nucleus interactions is studied experimentally for the case where the transverse momenta of product particles are in excess of 1 GeV/c. The values obtained for the exponent in the A dependence of the cross section for the production of noncoplanar hadron pairs are substantially greater than those for coplanar pairs. This nuclear-mass-number dependence for the production of hadron pairs can be explained by the contribution of multiparton interactions in proton-nucleus collisions.     

Pair production of pions with symmetric momenta in the range 0.5⩽pT⩽2.0 GeV/c In 70 GeV p-p collisions

The invariant cross-section slope of the pp→π⁺π^?+X process as a function of p_T is found to have a break near 1 GeV/c. Fitting the cross section by a sum of two exponents gives the values of powers (12.3±0.9)(GeV/c)^?1 and (8.7±0.6)(GeV/c)^?1. The experimental points at p_T?1 GeV/c are significantly higher than predictions based on hard scattering models such as QCD and CIM.     

Single-spin asymmetry for charged hadrons produced in proton-nucleus collisions at 40 GeV for c.m. production angles in the range 40°–79°

The transverse single-spin asymmetry for charged hadrons (π ^±, K ^±, p, $\bar p$ ) produced in proton-nucleus collisions was measured for c.m. production angles in the range 40°–79°. The measurements were performed with the FODS-2 setup by using a 40-GeV polarized proton beam originating from the accelerator of the Institute for High Energy Physics (Protvino) and hitting carbon and copper nuclear targets. The data in question were obtained in the polarized-proton-fragmentation region (0.0 < x _F < 0.7, 0.6 < p T < 2.5 GeV/c). In agreement with data obtained at other energies, the single-spin asymmetry for π ^± mesons is significant at high x _F. For the first time, a sizable analyzing power, which changes sign at x _F = 0.43, is observed for protons. The dependence of the analyzing power on the target-nucleus mass is insignificant.     

Single-spin asymmetry for high-p T charged hadrons at negative x F in proton-nucleus collisions at an energy of 40 GeV

The transverse single-spin asymmetry was measured for charged hadrons (π ^±, K ^±, p, $\bar p$ ) produced in proton-nucleus collisions. The measurements were performed with the aid of the FODS-2 spectrometer by using a 40-GeV polarized proton beam from the accelerator of the Institute for High Energy Physics (IHEP, Protvino) and carbon and copper nuclear targets. The data subjected to the analysis in the present study were obtained for c.m. angles in the range 95°–112° in the vicinity of the central region (?0.08 < x _F < ?0.06, 0.7 < p _T < 3.4 GeV/c). The analyzing power is found to be only slightly dependent on the mass number of the target nucleus. The basic results obtained by measuring the single-spin asymmetry at three values of the particle-detection angle are discussed.     

HighP ∧ hadron production off nuclei at 70 GeV

Invariant cross sections for hadron production (π^±,K ^± ,p and \(\bar p\) ) by protons off C, Al, Cu, Sn and Pb nuclei have been measured at 70 GeV for theP _∧ range from 1 up to 4.65 GeV/c. TheA-dependence of the invariant cross section is not described by the exponentialA ^α(P _∧), which points to the presence of secondary hadron absorption in nuclei.     

Hadron production at transverse momenta from 0.5 up to 2.2 GeV/c in proton-proton collisions at 70 GeV

The cross sections for π^±, K^±, p, and $\text{p}$ production in pp collisions have been measured at transverse momenta from 0.48 up to 2.21 GeV/c at 70 GeV. The data are compared with results obtained at lower and higher proton energies and also with the quantum chromodynamics parton model (QPM) calculations. Common behaviour of the cross sections of the form $\text{g(p}{}_{\mathrm{\perp }}\text{)?(x}{}_{\mathrm{\perp }}\text{)}$ in the energy range above 200 GeV does not take place at lower energies. Qualitatively QPM fits the data and the best agreement is for π⁺/π^? and K⁺/π⁺ ratios.