GeV Proton Interactions Research Articles

High-Efficiency Volume Reflection of an Ultrarelativistic Proton Beam with a Bent Silicon Crystal

The volume reflection phenomenon was detected while investigating 400 GeV proton interactions with bent silicon crystals in the external beam H8 of the CERN Super Proton Synchrotron. Such a process was observed for a wide interval of crystal orientations relative to the beam axis, and its efficiency exceeds 95%, thereby surpassing any previously observed value. These observations suggest new perspectives for the manipulation of high-energy beams, e.g., for collimation and extraction in new-generation hadron colliders, such as the CERN Large Hadron Collider.

Rapidity correlations in 800 GeV proton-nucleus interactions

Rapidity correlations in 800 GeV proton interactions with emulsion nuclei are investigated for different targets and multiplicity regions. To study the energy dependence, the results have been compared with proton interactions at 200 GeV and 400 GeV. A common feature of all the interactions is the existence of strong, short-range correlations. However, no dependence of cluster parameters on primary energy or target mass is found. A marginal increase of correlation strength with multiplicity is observed.

Intermittency and multifractality of medium-energy particles in proton-nucleus interactions at 800 GeV.

We investigate the intermittent and multifractal behaviors of the multiplicity fluctuations of medium energy particles in 800 GeV proton interactions with emulsion nuclei. For our analysis, we have used ordinary scaled factorial moments (SFM) denoted as ${\mathit{F}}_{\mathit{q}}$, modified SFM, (${\mathit{F}}_{\mathit{q}}^{\ensuremath{'}}$) and modified multifractal moments, (${\mathit{G}}_{\mathit{q}}^{\ensuremath{'}}$) with suppressed statistical contributions. For a close comparison between the ${\mathit{F}}_{\mathit{q}}^{\ensuremath{'}}$ and ${\mathit{G}}_{\mathit{q}}^{\ensuremath{'}}$ moments, they have both been expanded in a set of basic functions each of which has a characteristic fractal behavior as a function of the resolution in phase space. The experimental values of anomalous fractal dimensions ${\mathit{d}}_{\mathit{q}}$ and Renyi dimensions ${\mathit{D}}_{\mathit{q}}$ are determined for q=2-5. The latter are corrected for statistical contamination in the multiplicity fluctuations. The observed variation of ${\mathit{d}}_{\mathit{q}}$ and ${\mathit{D}}_{\mathit{q}}^{\mathrm{dyn}}$ with q supports a self-similar random cascading mechanism for the particle production process. It is found that ${\mathit{D}}_{\mathit{q}}^{\mathrm{dyn}}$+${\mathit{d}}_{\mathit{q}}$=1.

Nuclear effects in 800 GeV proton interactions

We discuss here the nuclear effects in multiparticle production processes in 800 GeV proton-emulsion nuclei interactions. The multiplicity of medium energy particles (Ng) was used as a measure of the average number of projectile collisions ( ). To study nuclear effects, we determined and ratio of normalized rapidity density of all produced charged particles in hadron-nucleus to hadron-hadron interaction,R(Nη). It was found that the average multiplicity of shower particles increases with . From theR(Nη) distribution, we find; a strong maxima in the target fragmentation region, a plateau in the central region and depletion of particle density in the projectile fragmentation region.

Factorial moments in high-multiplicity events in 800 GeV proton interactions with AgBr nuclei

The scaled factorial moments were investigated for secondary particles in high-multiplicity events produced by 800 GeV proton interactions with AgBr nuclei in a nuclear emulsion. The results show clear evidence for power-law behavior of scaled factorial moments. The variation of dimension as a function of order of the moment was also studied. The presence of phase transitions is not indicated from our data. From the behavior of the third-differential moment, we do not find any evidence for the clustering of particles in any pseudorapidity region.

Self-similarity in one and two dimension of 800 GeV proton interactions with AgBr nuclei

The normalized multiplicity moments in one and two dimensions were investigated for secondary particles produced in 800 GeV proton interactions with AgBr nuclei in nuclear emulsion. The fluctuations are found to be more in two dimensions as compared to one dimension. It has been shown that the self-similar cascade model describes well the observed fluctuations. The multiplicity shows a weaker dependence of moments for high multiplicity events in comparison to all multiplicity events. The slope ratios (rq) are not different in one and two dimensions and are found to be independent of the multiplicity. Therq distribution is well represented by the logbinomial and Levy-stable distributions which follows from the self-similar cascade model.

HADRON PRODUCTION IN THE RESTRICTED RAPIDITY INTERVALS IN PROTON-NUCLEUS INTERACTIONS AT HIGH ENERGIES

Data on 200 and 400 GeV proton interactions with nuclear emulsion have been analyzed. It is found that the multiplicity distributions of the shower particles in the restricted rapidity intervals are well described by the negative binomial distribution (NBD). The dependences of the NBD parameters on rapidity interval, energy and target size have been studied. The results have also been discussed in terms of Giovannini and Van Hove’s clan model of multiparticle production.

Dependence of Cluster Size on Shower Particle Multiplicity

Characteristics of clusters and the dependence of their size on the multiplicity of charged shower particles are investigated by analysing the experimental data involving 50 GeV negative pion and 400 GeV proton interactions with emulsion nuclei. The results reveal that the maximum number of particles constituting a cluster is four for the disintegrations with \(n_{s}{\geqslant}10\), where n s is the number of charged particles having \(\beta{\geqslant}0.7\), whilst this number is observed to be three for the events having n s <10. The findings also suggest that cluster size is independent of the nature and energy of the impinging hadron.

Multiparticle production in proton-nucleus collisions at tevation energy

For 800 GeV proton interactions with nuclear emulsions, the multiplicity ofshower particles, their correlation and the pseudorapidity distributions are presented.

Search for tau-neutrino interactions in the BEBC beam dump experiment

A novel and efficient kinematic method is used to estimate the number of ν τ charged current interactions with E ν > 20 GeV in the BEBC beam dump experiment. The result, −14±12 ν τ events, is consistent with zero. The ratio of D s to D meson production in 400 GeV proton interactions in copper is estimated to be below 0.65 at 90% c.l. The oscillation probability P( ν e→ ν τ ) averaged over the electron-(anti)neutrino spectrum is found to be below 18%. The hypothesis that ν e and ν τ are identical is excluded by about 6 standard deviations. A remarkable event is described: it contains a muon, a high p T photon and a high p T hadron.

A total energy trigger at large angles used in a calorimetric study of 150 GeV and 300 GeV pion and proton interactions on hydrogen

Hard hadronic scattering was studied by selecting 150 GeV and 300 GeV π −p and pp events with large energy in a 240 cell calorimeter covering 45† to 135† in the c.m.s. polar angle and the full 2 π azimuth. A downstream calorimeter measured the remaining energy flow at smaller angles. For large energy deposited in the segmented calorimeter the proton induced cross section drops below the pion induced cross section, as expected in a constituent scattering picture. However, neither a simple energy scaling of the cross section nor a dominant jet structure of the events is observed. No evidence was found for recently proposed higher-twist mechanisms leading to events

Search for superdense nuclei of Rb and Cs among the products of 8 GeV proton interactions with Ta

Experimental searches for β-active superdense nuclei of Rb and Cs among the products of 8 GeV proton interactions with Ta are described. The method of selective off-line mass-separation with scanning of the β-activity distribution on the collector was used. According to π-condensation theory, the long-lived anomalous nuclei are expected to be more neutron-deficient than the usual ones. Moreover, their mass numbers may be significantly nonintegral measured on the normal mass scale, because of unusual binding energy. These predictions guided the present search. No anomalous nuclei were found. The upper limit for Rb nuclei in the range 69 ⩽ A ⩽ 78 is 10 −5 with respect to the yield for 81Rb; for Cs in the range 112 ⩽ A ⩽ 122 the limit is (5–10) × 10 −6 of the yield for 127Cs. These estimations are based on the assumption that the half-life of superdense nuclei equals 5 h.

Yields and isomeric ratio of xenon and krypton isotopes from thermal neutron fission ofU235

The experimental cumulative yields of /sup 85/Kr/sup m/, /sup 87/Kr, /sup 88/Kr, /sup 133/Xe/sup g/, /sup 135/Xe/sup m/, and /sup 135/Xe/sup g/ and the independent isomeric yield of /sup 133/Xe/sup m/ in the thermal neutron fission of /sup 235/U have been measured by the gas chromatographic method. The independent yields of /sup 133/Xe/sup g/, /sup 135/Xe/sup m/, and /sup 135/Xe/sup g/ were deduced with the aid of /sup 133/I and /sup 135/I data. The isomeric yield ratios of /sup 133/Xe and /sup 135/Xe have been computed and compared with theoretical values since they have the same high spin state J = 11/2/sup -/ and low spin ground state J = 3/2/sup +/. The influence of the shell effect on the fission isomeric yield ratio is discussed. From the measured independent yield of Xe isotopes plus the reported data, the Xe-isotopic distribution curve has been constructed. The curve is compared with the isotopic distribution curves of Xe isotopes formed in 11.5 GeV proton interactions with /sup 238/U and Cs isotopes formed in 24 GeV proton interactions with /sup 238/U. Upon fitting the yield curves we find that only those products with N/Z> or =1.48 fit a curve typical of a binarymore » fission process.« less

Comparative study of inclusive correlation functions in proton interactions on emulsion nuclei

R( η 1, η 2) and C( η 1, η 2) inclusive correlation functions are studied in 300 GeV proton interactions on emulsion nuclei. Their dependence on nuclear excitation is investigated and some differences between their behaviours are pointed out. The interpretation of experimental data is attempted in the framework of a repeated independent collision picture of hadron-nucleus interactions. The introduction of clustering patterns in produced hadronic matter provides a qualitative description of the target dependence of correlations.

Some aspects of 400 GeV proton interactions in nuclear emulsions

Ilford G5 nuclear emulsions were exposed to 300 GeV and 400 GeV proton beams at the National Accelerator Laboratory. A total of 350 interactions were found and analyzed. The study was concentrated on non-white stars because of insufficient scanning efficiency for white stars. The mean free path for 300 GeV proton is 36.9 ± 2.6 cm which is in good agreement with other authors. A linear relation is observed between the charge shower particle multiplicity and the star size indicating that the number of shower particles is independent of the target nuclei. Black prongs for smaller stars seems to show higher value of forward-backward ratio suggesting larger motion of nucleus after collisions.

Search for the production of particles with lifetimes ∼(10−12÷10−14) s in 400 GeV proton interactions in nuclear emulsion

Search for the production of particles with lifetimes ∼(10−12÷10−14) s in 400 GeV proton interactions in nuclear emulsion

Nucleon and charged-pion albedo spectra in an accelerator cave from 200 GeV proton interactions in iron

Nucleon and charged-pion albedo flux distributions in an accelerator cave resulting from the interaction of 200 GeV protons have been calculated. The spectra are given as a function of secondary-particle energy and of radial position and distance from the point where the beam is dumped into the iron. Comparisons between the omnidirectional and “backward” flux distributions are presented.

The production of 7Be by 7 GeV proton interactions with oxygen

The cross section for 7Be production by 7 GeV proton interactions with oxygen has been measured and found to be 9.1 ±0.5 mb (with an absolute accuracy better than 20 %). A comparison with other published data is made.

On the neutrons produced in 24 GeV proton interactions in graphite

The energy of neutral particles originating in 24 GeV/ c proton interactions in carbon has been investigated from the interactions produced by them in an emulsion stack exposed behind a graphite target placed in the 24 GeV/ c proton beam at CERN. The energy has been estimated for the cases n S ⩾ 2, 3 and 4. It is found that the high-energy neutrons which survive the interactions have about one third of the primary energy.

Spallation and fission fragments of heavy nuclei induced by 18 GeV protons registered by means of solid plastic detectors

Results of 18 GeV proton interactions with heavy nuclei by means of solid ionographic detectors are presented. Sandwich and detector technique is exposed. The possibility of existence of three prong events is examined and discussed.