Keizo Kobayakawa

The Production of Prompt Cosmic Ray Muons and Neutrinos

Calculs dans le cadre du modele quark-parton. On evalue le spectre energetique des muons produits dans le rayonnement cosmique, et de facon semblable celui des neutrinos

The photonuclear energy loss of cosmic-ray muons and its relation with photon-nucleon cross-section

SummaryThe coefficientbN of the photonuclear energy loss for high-energy muons is calculated by the generalized vector-dominance model with the different energy dependences in real photon-nucleon cross-sections and by the parton model with a modified scaling variable. The intensities of cosmic-ray muons at great depths are converted into the energy spectrum by taking range fluctuation into account. By comparing the exponents of the spectrum with those from other experiments, it is concluded that the real photon-nucleon cross-section has a ln2 ν dependence at higher energies than TeV regions.RiassuntoIl coefficientebN della perdita di energia fotonucleare per muoni ad alta energia è calcolata mediante il modello generalizzato di dominanza vettoriale con diverse dipendenze dallenergia nelle sezioni durto fotone-nucleone e mediante il modello a partoni con una variabile di scala modificata. Le intensità dei muoni dei raggi cosmici a grandi profondità sono convertite in spettro di energia prendendo in considerazione la fluttuazione dellintervallo. confrontando gli esponenti dello spettro con quelli ottenuti da altri esperimenti, si conclude che la sezione durto reale fotone-nucleone ha dipendenza ln2v ad energie più alte delle regioni del TeV.РезюмеВычисляется коэффициентbN фотоядерных потерь энергии для мюонов высоких энергий, используя модель обобщенной векторной доминантности с различными энергетическими зависимостями в реальных фотон-протонных поперечных сечениях и партонную модель с модифицированной переменной масштаба. Интенсивности мюонов космических личей на больших глубинах, с учетом флуктуаций пробегов, преобразовывают энергетический спектр. Сравнивая экспоненты спектра с экспонентами из друтих экспериментов, делается утверждение, что реальное фотоннуклонное поперечное сечение имеет зависимость ln2 ν при высоких энергиях, в ТэВ-ной области.

The trigger system of mutron, a cosmic ray magnetic spectrometer

Abstract A large magnetic spectrometer for cosmic-ray studies has been built at Cosmic Ray Laboratory, University of Tokyo, which consists of two 400 t solid iron magnets, multiwire proportional chambers (MWPC), wire spark chambers and a calorimeter. In this paper the trigger system will be described whose geometrical acceptance is about 1300 cm 2 sr including the magnets. The trigger system consists of twenty large area MWPCs. The trigger selection is made up of the momentum selection, which excludes low momentum muons, and the particle-number selection limiting the number of particles hitting the trigger detectors simultaneously. This combination for trigger reduces the background level and improves the ratio of muons to background. The trigger rate is about 1.0 per minute in the usual operation.

Cosmic-ray muon spectrum derived from the transferred energy spectrum of bursts observed by the mutron calorimeter

SummaryMeasurements of the energy transfer,E′, of bursts produced in a calorimeter are calibrated with the momenta of the incoming and outgoing muons measured by the Mutron magnet spectrometers. The relation between energy transferE′ and momentum difference Δpc was obtained in the energy range from 30 GeV to 1 TeV as follows:E′=(0.85±0.16) Δpc. Using this calibrated calorimeter, we observed distributions of the energy transfer of bursts produced in the calorimeter up to 6 TeV by the magnet spectrometer plus calorimeter triggers, as well as by the calorimeter trigger alone. From the observed burst spectrum, we have derived the muon energy spectrum at sea-level. The differential pion production spectrum combined with the data using composite triggers gives an exponentγ=2.58±0.19 in the muon energy region from 200 GeV to 6 TeV and 2.74±0.19 in the region from 1 TeV to 6 TeV. The muon energy spectrum thus obtained is compared with the direct measurement of the muon spectrum by the Mutron magnet spectrometers. It is thus established that measurements of the transferred energy spectrum of bursts are available for the derivation of the muon energy spectrum beyond the energy region measured by the magnet spectrometer.RiassuntoSi calibrano le misure del trasferimento d’energiaE′ di scrosci prodotti in un calorimetro con gl’impulsi dei muoni in entrata e in uscita misurati dagli spettrometri a magneti Mutron. Si ottiene la relazione tra il trasferimento di energiaE′ e la differenza d’impulsi Δpc nell’intervallo di energia da 30 GeV a 1 TeV come segue:E′=(0.85±0.16)Δpc. Usando questo calorimetro calibrato, sono state osservate le distribuzioni del trasferimento d’energia di scrosci prodotti nel calorimetro fino a 6 TeV sia mediante l’innesco dello spettrometro a magneti piú quello del calorimetro, che solamente con quello del calorimetro. Dallo spettro degli scrosci osservato, è stato derivato lo spettro d’energia dei muoni a livello del mare. Lo spettro differenziale di produzione di pioni combinato con i dati ottenuti usando inneschi composti dà un esponenteγ=2.58±0.19 nella regione d’energia muonica da 200 GeV a 6 TeV e 2.74±0.19 nella regione da 1 TeV a 6 TeV. Lo spettro d’energia muonica cosí ottenuto è confrontato con la misura diretta dello spettro muonico degli spettrometri a magneti Mutron. Si stabilisce cosí che le misure dello spettro d’energia trasferita degli scoppi permettono di derivare lo spettro d’energia muonica al di là della regione d’energia misurata dallo spettrometro a magneti.

Electromagnetic interactions of cosmic-ray muons up to 10 TeV (pair productions and bremsstrahlung)

SummaryElectromagnetic interactions (excluding nuclear interactions) of cosmic-ray muons were investigated by a combined arrangement of the Mutron magnet spectrometer and calorimeter. The interactions covered their transferred energies ranging from 1 GeV to several TeV produced by muons with energies up to 10 TeV. There is reasonable agreement between the experimental results and the theoretical predictions. For transferred energies less than 10 GeV, however, the observed number of events produced by muons around 1 TeV may be somewhat smaller than theoretically expected. The probability of accompaniment of a muon emerging from thick iron plates is also studied. The data are very useful for the measurement of the muon momentum by the magnet spectrometer. The ratio of the interaction probability for positive muons to that for negative muons is 0.94±0.02 for interactions with energy transfers over 1 GeV. However, by considering the measured accuracy of the value ±0.05 used for the charge ratio of incident muons, there is no evidence to support any suggestion that the interaction cross-sections of positive and negative muons for energy transfers above 1 GeV differ in the range from 100 GeV to 10 TeV.RiassuntoSono state studiate le interazioni elettromagnetiche (escludendo le interazioni nucleari) dei muoni dei raggi cosmici mediante una disposizione combinata dello spettrometro a magneti Mutron e del calorimetro. Le interazioni riguardano le energie trasferite che vanno da 1 GeV a qualche TeV prodotte da muoni con energie fino a 10 TeV. Si trova un discreto accordo tra i risultati sperimentali e le previsioni teoriche. Per energie trasferite minori di 10 GeV, comunque, il numero osservato di eventi prodotti da muoni a circa 1 TeV può essere un po’ piú piccolo di quanto previsto teoricamente. Si studia anche la probabilità di accompagnamento di un muone uscente da spesse piastre di ferro. I dati sono molto utili per misurare l’impulso del muone con lo spettrometro a magneti. Il rapporto tra la probabilità d’interazione per muoni positivi e quella per muoni negativi è di 0.94±0.02 per interazioni con trasferimenti di energia al di sopra di 1 GeV. Comunque, considerando l’accuratezza misurata del valore ±0.05 usato per il rapporto di carica dei muoni incidenti, non c’è nessuna prova che sostenga l’ipotesi che le sezioni d’urto d’interazione tra muoni positivi e negativi per trasferimento d’energia al di sopra di 1 GeV differiscano nell’intervallo da 100 GeV a 10 TeV.

A calorimeter to study cosmic ray muon interactions

Abstract A calorimeter with a volume of 3.6×4×2.4 m 3 has been built in the Institute for Cosmic Ray Research, University of Tokyo to study the interactions of cosmic ray muons of known momenta. The calorimeter is located between the two magnets of MUTRON, a magnet spectrometer built by the same laboratory to measure muon momenta up to a maximum of 17 TeV c −1 . In this article, the design of the calorimeter is described and the characteristics of the counters used are reported. The expected number of the interactions and the accuracy of energy determinations by the calorimeter are also discussed.

Backward Emission of Relativistic Particles in the Laboratory System in 200 GeV Proton-Nucleus Collisions

In proton-nucleus collisions at 200 GeV studied in nuclear emulsion, relativistic particles are found to be emitted in the laboratory backward hemisphere frequently. These backward particles consist of pions and protons of relatively high energy. Emission of backward particles increases rapidly with the mass number of the target nucleus. Backward emission of such high energy particles is difficult to explain by the simple superposition of proton-nucleon elementary interactions.

Particle Correlations in an Independent Emission Model

Up to now, the particle correlations in the multiparticle production phenomena are studied mainly by various cluster models which have two step mechanisms, the pro: duction and the subsequent decay of clusters.u However, in these models some kinematical constraints such as energy-momentum conservation or charge conservation have not been explicitly taken into account. In this paper, we discuss the role of these kinematical constraints on particle correlations in a simple, independentparticle-emission model and comment on the structure of clusters. Model: -We analyze the reaction p+p ---+N+N+mc at 205GeV/c where n is the total number of produced pions. The distribution of n is assumed to be Poissons one with (n)=10.02, since the average charged multiplicity for this reaction is 7.68±0.07. 21 We consider the production mechanism based on the multiperipheral-like diagram as shown in Fig. 1 so that the charge conservation at each vertex point are taken into account. The double charge (or exotic meson) exchange mechanisms are assumed to be suppressed. Further, the situation of final pions and nucleons in one event is