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1.
The inclusive cross sections for prompt photon production by π? and π+ on protons have been measured with a beam momentum of 280 GeV/c using a fine grained electromagnetic calorimeter and the CERN Omega spectrometer. The transverse momentum and Feynmanx F ranges covered are 4.0<p T <7.0GeV/c and ?0.45<x F <0.55 respectively. A quantitative comparison of the prompt photon cross section with next-to-leading order QCD predictions using Duke and Owens structure functions is performed.  相似文献   

2.
The inclusive cross sections for η production by the interactions of 280 GeV/c momentum π?, π+, and proton beams in hydrogen have been measured. The kinematical range covered is ?0.45<x F <0.45, and 4.0<P T <7.0 GeV/c for Feynmanx F and transverse momentum respectively. The η to π0 cross section ratios are given for the three reactions. The ratio of π? p to π+ p cross sections for η production in the above kinematic ranges is 1.22±0.08±0.11.  相似文献   

3.
Direct photon production has been studied by an experiment performed with the NA3 spectrometer at CERN, using incident negative and positive beams at 200 GeV/c interacting with an isoscalar Carbon target. Two different triggers have been used; one of them requires the photon conversion. The experiment is sensitive to direct photons produced with 3.0≦P T ≦6 GeV/c and center-of-mass rapidity ?0.4≦y *≦1.2. Inclusive cross sections are given for incident π± and protons, and compared with second order QCD predictions; finally an estimation of the gluon structure function of the nucleon is given.  相似文献   

4.
The inclusive cross sections for π0 production by π? and π+ on protons have been measured with a beam momentum of 280 GeV/c using a fine grained electromagnetic calorimeter and the CERN Omega spectrometer. The transverse momentum and Feynmanx F ranges covered are 4.0<p T <7.0 GeV/c and ?0.45<x F <0.6 respectively. The data are compared with leading order QCD calculations.  相似文献   

5.
We have calculated within the QCD frame-work the inclusive one and two particle production cross sections triggering on a photon or a π0 for incident protons and antiprotons. The results are compared and shown to be in good agreement with all pertinent experimental data, provided a hard gluon structure function is used. The γ/π0 ratio as well as the ratio of bremsstrahlung to directly produced γ's are examined as a function of rapidity andp T. Results are presented for c.m. energies \(\sqrt s = 62\) and 800 GeV  相似文献   

6.
Inclusive and semi-inclusive cross sections and distributions of γ's and π0's inK + p interactions at 70 GeV/c are presented. The results are compared to other experiments and to the Lund model for low-p T hadron collisions.  相似文献   

7.
Experimental results on inclusive ? production are compared with the Lund model for lowp T hadronic interactions. The data is based on a sample of 600,000 ? mesons in the kinematic rangep T <1.0 (GeV/c)2 and 0.0<x F<0.4, produced in π±,K ±,p and \(\bar p\) Be interactions at 100 GeV/c and 120 GeV/c incident momentum. The Lund model reproduces the shapes of the longitudinal differential cross sections reasonably well, but the relative cross sections for incident, π,K andp show a discrepancy with the data.  相似文献   

8.
The inclusive π0 and γ production is studied in a \(\bar PP\) experiment at 32.1 GeV/c performed in the Mirabelle bubble chamber with a sensitivity of ~2.7 events/μb. Total and topological π0 cross sections are presented. The π0 and γ longitudinal and transverse momentum distributions are obtained and compared with \(\bar PP\) data at 22.4 GeV/c andK ± P data at 32.1 GeV/c. The inclusive π0 distributions are also compared to those obtained for charged pions in the same experiment.  相似文献   

9.
Differential cross sections for backward π?d elastic scattering (?1 ≦ cos θc.m ≦ ?0.98) have been measured at fourteen momenta from 0.98 to 1.76 GeV/c and at 2.45 GeV/c. Energy dependence of the cross section exibits a new wide structure at √s ≈ 2.9 GeV. Possible mechanisms of the reaction accounting for this structure are presented. Experimental data are compared with theoretical calculations.  相似文献   

10.
The photoproduction of prompt photons, together with an accompanying jet, has been studied in ep collisions at a centre-of-mass energy of 318 GeV with the ZEUS detector at HERA using an integrated luminosity of 77 pb-1. Cross sections were measured for the transverse energy of the photon and the jet larger than 5 and 6 GeV, respectively. The differential γ+jet cross sections were reconstructed as functions of the transverse energy, pseudorapidity and xγ obs, the fraction of the incoming photon momentum taken by the photon-jet system. Predictions based on leading-logarithm parton-shower Monte Carlo models and next-to-leading-order (NLO) QCD generally underestimate the cross sections for the transverse energies of prompt photons below 7 GeV, while the kT-factorisation QCD calculation agrees with the data better. When the minimum transverse energy of prompt photons is increased to 7 GeV, both NLO QCD and the kT-factorisation calculations are in good agreement with the data.  相似文献   

11.
A high-statistics study of the π0π0-system produced in the π- p→π0π0 n reaction at 38GeV/c has been carried out at the IHEP accelerator using the GAMS-2000 multiphoton spectrometer. A partial-wave analysis which includesS, D 0, D? andD + waves has been performed in the |t|-range up to 1 (GeV/c)2. TheS */f 0(980) resonance is seen as a dip in theS-wave amplitude at small |t|. A distinct peak with a mass of 997±5MeV and a width of 48±10MeV is observed in theS-wave at |t|>0.3 (GeV/c)2. The production cross sections are measured.  相似文献   

12.
The production of energetic π? at 0° has been measured in Ne+NaF and Ni+Ni collisions with incident energies between 1.3 and 2AGeV. In Ne+NaF collisions the investigation was extended to extreme subthreshold processes with lab momenta up to 4.5 GeV/c. In both systems at all incident energies the π? production cross sections deviate in a systematic way from thermal distributions.  相似文献   

13.
Inclusive charged pion production is studied in an exposure of BEBC, filled with hydrogen, to an incidentK + beam of 70 GeV/c. Total cross sections for pion production and inclusive longitudinal and transverse momentum distributions of π?'s and of positive particles are presented and compared with data at lower energies. Earlier evidence for scaling in the fragmentation regions is confirmed. The central region π? cross section increases proportionally top LAB ?1/4 ; positive particles show almost no energy dependence atx=0. Particle ratios π+? are studied as a function ofx andy * and a comparison with 70 GeV/cK ? p data is made. Analysis of structure functions for (ππ) pairs and of particle production associated with π± triggers at large |x| in the context of quark/parton models, provides qualitative evidence for the diquark-quark structure of the proton.  相似文献   

14.
The reaction π? AAπ? γ at 40 GeV/c was studied on “Sigma” spectrometer on six different nuclear targets in the region of four-momentum transfer |t|<0.05 (GeV/c)2. A phenomenon of elastic scattering of pions on the nuclear Coulomb field photons was observed, its total and differential cross sections were measured. The cross section of Compton effect on π?-meson was measured.  相似文献   

15.
The inclusive production of γ's and πp0's inK ? p-interactions at 32 GeV/c is studied. About 30.000 γ's coming from a Mirabelle bubble chamber experiment with a sensitivity of 6.5 ev/μb have been used for the analysis. Inclusive and topological cross sections of γ's are measured. The γ invariant differential distributions and their scaling properties are investigated. The inclusive cross section of πp0-production is determined and the πp0 invariant differential distributions are evaluated and compared to those of π.  相似文献   

16.
A search for massive photon pair production at \(\sqrt s = 63 GeV\) has been carried out on the data sample previously employed for the electron pair production study. Positive evidence is reported form γγ>6GeV, with a production cross-section similar to Drell-Yan electron pairs. The ratio γγ/π0π0 was measured to be ~10?3 for ap T of each γ or γ or π0 above 3 GeV/c.  相似文献   

17.
The inclusive production of π+ for 0.4≤pT<1.0 GeV/c in pion-nucleus and proton-nucleus collisions at 4.3 GeV/c was measured. A strong A-dependence of the cross sections at high pT is observed to be persistent in the low energy region. The ratio of the cross sections for proton-nucleus and pion-nucleus collisions is also observed to be compatible with the quark-parton picture, for pT>0.6 GeV/c.  相似文献   

18.
A new second vacuum trajectory passing throughf*(1515) and σ(548), α(t)=? 0.3+t, is proposed, which, together with αp″(t=0)=? 0.5, overcomes the failure of Igi's original superconvergent πN sum rule and avoids the ghost-state of the conventionalP′-trajectory. The negative residue att=0 confirms the repulsive contribution of a vacuum pole component withJ=0 to the generalizeds-reaction potential, as postulated by Chew (1965). TheP- andP′-poles can build the non resonating background. The Gell-Mann nonsense mechanism at the negative integers with wrong signature explains the dips in the elastic π± p-scattering att=?0.7, ?2.7 and ?4.5 (GeV/c)2. σ(∞) for πN reactions turns out to be 24.3 mb, if α p (t=0)=1, but the best fits to the total πN cross sections for pion momenta between 2 and 29 GeV/c yield α p (t=0)=0.93.  相似文献   

19.
An experiment has been performed to study the inclusive photoproduction of π0 mesons. Photoproduced π0's were detected in a hodoscope consisting of 14 lead glass Cerenkov counters. To obtain the cross sections at a photon energy of 6 GeV we used the photon-difference method. Data are presented in terms of the Feynman variable x = q61(√s/2) and the trnasverse momentum q⊥. We have measured four q⊥ distributions at x = 0.2, 0.4, 0.6 and 0.8. The results dhow that the π0 rate at small values of q⊥ is smaller than the π± rate. The data can be fitted smoothly by a form A exp (?Bq2) with a value about 3.5 GeV?2 for the slope parameter B.  相似文献   

20.
The production of π 0 and η mesons has been investigated in the system 12C+12C at 0.8A GeV, 1.0A GeV, and 2.0A GeV using the TAPS photon detector. The production cross sections and transverse-momentum distributions measured around midrapidity extend the existing systematics of neutral-meson production to light systems and the highest energy available at the GSI accelerator facility. At all beam energies scaling of the differential production cross section with the transverse mass of the emitted meson is observed. In addition π0 production has been studied in the mass-asymmetric systems 12C+197Au and 197Au+12C at 0.8A GeV.  相似文献   

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