A measurement of the photonuclear interactions of 180 GeV muons in iron

The energy spectrum and the cross section of photonuclear interactions of 180 GeV muons in iron were measured at the CERN SPS using prototype modules of the ATLAS hadron calorimeter. The differential cross section for a muon fractional energy loss was measured in the range 0.1<v<1. The integrated cross section is cm²g^-1 in agreement with the theoretical prediction of cm²g^-1. The best adjustment of the data to the theory is achieved for the value of of the photon-nucleon cross section for photons with energies in the range from 18 to 180 GeV. Received: 22 January 2003 / Published online: 5 May 2003     

The lateral distribution of energetic shower muons

Summary The customary assumption of a unique structure function of the formf(r)∞r ^−αexp[−r/R ₀] with parameters independent of the shower size and the nature of the primary is tested against evidence on the multiplicity distribution of shower muons. The experimental data were obtained with an array of three spark chamber telescopes installed at the Mt. Cappuccini underground station, Torino, at depths of about 40 to 60 hg/cm². They pertain to events with mean shower sizes between about 10⁵ and a few 10⁷ electrons. It is shown that the results are incompatible with this assumption, whatever values are assigned to the exponent α and to the characteristic radiusR ₀ of the structure function. A modified representation allowing for a variation ofR ₀ with the shower size and with the massA of the primary is suggested. The resulting distribution is in reasonable agreement both with thorough Monte Carlo evaluations for proton and iron primaries and with direct experimental observations of other authors.

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Riassunto L'ipotesi usuale di una funzione di struttura unica della formaf(r)∞r ^−αexp[−r/R ₀] con parametri indipendenti dalle dimensioni dello sciame e dalla natura dei primari è provata rispetto alle prove sperimentali sulla distribuzione di molteplicità dei muoni dello sciame. I dati sperimentali sono stati ottenuti con un sistema di tre telescopi con camere a scintille istallati nella stazione sotterranea del Monte dei Capuccini, Torino, a profondità da 40 a 60 hg/cm². Essi riguardano eventi con grandezze medie di sciami tra circa 10⁵ e pochi 10⁷ elettroni. Si mostra che i risultati non sono compatibili con questa ipotesi, qualsiasi valore sia assegnato all'esponente α e al raggio caratteristicoR ₀ della funzione di struttura. Si suggerisce una rappresentazione modificata che consente una variazione diR ₀ con la grandezza dello sciame e con la massaA dei primari. La distribuzione risultante è in ragionevole accordo sia con tutte le valutazioni di Montecarlo per primari di protoni e di ferro e con osservazioni sperimentali dirette di altri autori.

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Резюме Исследуется обычное предположение о единственной структурной функции видаf(r)∼r ^−αexp[−r/R ₀], с параметрами, не зависяцими от размеров ливня и природы первичной частицы, на основе данных о распределении множественности мюонов в ливне. Зкспериментальные данные получены с помошью системы трех телескпов искровых камеп, установленных на подземной стандии Капучини в Турине, на глубинах от 40 до 60 гг/см². Полученные данные относятся к событиям со средними размерами ливня от 10⁵ до 10⁷ злектронов. Показывается, что полученные результаты являются несовместимыми с зтим предположением, какие бы значения зкспоненте α и характерному радиусуR ₀ структурной функции не были бы приписаны. Предлагается модифицированное представление, учитывающее изменение велиьиныR ₀ с размером ливия и с массойA первичной частицы. Полученное распределение хорошо согласуется и с оценками по Монте-Карло для первичных протонов и ядер железа и с непосредственными экспериментальными результатами других авторов.

     

A direct measurement of the energy spectrum of cosmic ray muons in the Mont Blanc underground laboratory

Using a transition radiation detector we have neasured the energy of cosmicray muons in the Mont Blanc laboratory, where the NUSEX experiment is located. With this technique we have been able to cover linearly the energy range from 0.1 TeV to about 0.5 TeV, where the detector response begins to saturate. The measurements are consistent with a muon energy spectrum deduced from a E^−3.71 distribution folded with 5000 hg/cm² standard rock absorption.     

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

Summary The coefficientb _N 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.

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Riassunto Il coefficienteb _N della perdita di energia fotonucleare per muoni ad alta energia è calcolata mediante il modello generalizzato di dominanza vettoriale con diverse dipendenze dall'energia nelle sezioni d'urto 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 dell'intervallo. confrontando gli esponenti dello spettro con quelli ottenuti da altri esperimenti, si conclude che la sezione d'urto reale fotone-nucleone ha dipendenza ln² v ad energie più alte delle regioni del TeV.

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Резюме Вычисляется коэффициентb _N 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.

     

A precise measurement of 180 GeV muon energy losses in iron

The energy loss spectrum of 180 GeV muons has been measured with the 5.6 m long finely segmented Module 0 of the ATLAS hadron Tile Calorimeter at the CERN SPS. The differential probability per radiation length of a fractional energy loss has been measured in the range ; it is compared with theoretical predictions for energy losses due to bremsstrahlung, production of electron–positron pairs, and energetic knock-on electrons. The iron elastic form factor correction to muon bremsstrahlung in the region of no screening of the nucleus by atomic electrons has been measured for the first time, and is compared with different theoretical predictions. Received: 28 December 2000 / Revised version: 14 February 2001 / Published online: 28 May 2001     

用于能量标定的束流损失测量系统

为精确地测量合肥电子储存环电子束的能量,建立了一套束流损失的测量装置,选择了一款对低能光子探测效率高的塑料闪烁体探测器,根据测量到的束流损失信号研制了一套数字化的信号处理电路,并进行了实际测量。测量结果表明该束流损失测量系统能够精确、灵敏地反映出束流损失的变化,可以用于自旋共振退极化法标定电子束能量的实验;并介绍了自旋共振退极化法的测量原理及依据的理论基础。     

用于能量标定的束流损失测量系统

为精确地测量合肥电子储存环电子束的能量,建立了一套束流损失的测量装置,选择了一款对低能光子探测效率高的塑料闪烁体探测器,根据测量到的束流损失信号研制了一套数字化的信号处理电路,并进行了实际测量。测量结果表明该束流损失测量系统能够精确、灵敏地反映出束流损失的变化,可以用于自旋共振退极化法标定电子束能量的实验;并介绍了自旋共振退极化法的测量原理及依据的理论基础。     

Protection from muons in high energy proton accelerators

A generalization of the works on muon shielding in proton accelerators is carried out. Coulomb scattering of muons, energy losses in ionization and excitation of atoms, bremsstrahlung, direct pair formation, and nuclear interaction are taken into consideration in the computations. Coefficients obtained from recent experimental data are used in the double differential distribution of pions in p-nuclear interaction. Results of computations of muon shielding in a 1000 Ge Vaccelerator are presented. Results obtained for a. 200 GeV proton accelerator are compared with the computations of other authors.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 50–55, April, 1972.     

Diffusion of positive muons in zone-refined iron below room temperature

The relaxation rate λ of μ⁺ spin in α-iron polycrystals and single crystal of 99.995% purity has been measured from 299 down to 50 K. At room temperature it is 0.14 μsec^-1, much smaller than ever observed. Above 120 K its temperature dependence obeys an Arrhenius law (activation energy 44 ± 3 meV) for the μ⁺ diffusion. Previous values in less pure samples are discussed in terms of internal field inhomogeneity and of μ⁺ trapping by chemical or non-chemical defects. The deduced diffusion rate is proportional to T² in the whole temperature region studied.     

Anomalous energy loss distributions of alpha particles in heavily implanted thin aluminium films

Anomalous energy loss distributions of ^l48Gd alpha particles have been observed in heavily implanted thin aluminium films. It is surmised that thin film micro-wrinkling is responsible for the observed effect and that the novel technique of energy loss spectral analysis (ELSA) should be useful in studies of the topography of such films.     

托卡马克装置中高能离子的直接损失

通过严格求解导心坐标系下的哈密顿方程,提出了托卡马克装置中离子的真实轨道理论,并利用此理论对国际热核聚变实验堆(ITER)中α离子的真实轨道进行了数值模拟研究,获得了驻点轨道和近期理论预言的半俘获轨道.根据此真实轨道理论计算了ITER中α离子的直接损失率.结果发现,与所提出的真实轨道理论相比,以前的回旋平均理论大幅度低估了α离子的直接损失率,两种理论的损失率差值可达14%,对此差异进行了详细的分析并给出了物理上的解释.     

Change of energy profiles for muons upon lattice relaxation

Systematic calculations of potentials for muons and protons in various simple metals have been recently performed using local pseudopotentials in first-order perturbation theory. In the present contribution some results which are of particular interest forSR are discussed. The modification of the energy profiles with lattice relaxation is studied in Cu and Cs.     

The measurement of upward going muons using the MACRO detector

The upward-going muon flux (E_μ > 1 GeV) has been measured with the underground detector MACRO at LNGS. The total number of measured events is compatible at the 8% c.l. with the expected one. Moreover, the zenith angular distribution of the measured flux does not match the expectation showing a deficit in the vertical direction where the apparatus performance is best known. Assuming an oscillation hypothesis with parameters in the range recently suggested to solve the atmospheric neutrino problem, the agreement increases, but not significantly. The results of an indirect dark matter search for a signal of WIMPs from the core of the Sun and of the Earth are given. Neutrino astronomy with MACRO is giving interesting results regarding possible high energy neutrino emission from pointlike sources and coincidences of neutrino events with γ-ray bursts.     

Low energy muons as probes of thin films and surfaces

Polarized muons with kinetic energies of a few eV (epithermal μ⁺) can be generated by slowing down energetic muons in appropriate moderators consisting of a thin layer of a van der Waals gas frozen on a substrate. The availability of polarized muons with kinetic energies in the eV to several keV range opens the possibility to extend the μSR technique to the study of thin films and surfaces (low energy μSR, LE-μSR). We summarize the characteristics of the very slow polarized muons and of a low energy beam based on the moderation technique. We discuss the implantation of muons in thin film samples and the potential and limitations of LE-μSR. As an example first results obtained by implanting slow μ⁺ in a sample consisting of a Ni film deposited on Ag are presented.     

Influence of asymmetric energetic ion distributions on sawtooth stabilization

The effect of energetic asymmetrically distributed ions on the stability of the internal kink mode in tokamaks is analyzed. Circulating ions which intersect the resonant surface due to finite radial excursion contribute to the mode either in the region of favorable or unfavorable curvature depending on the sign of v( parallel ). Internal kink mode stabilization for predominantly cocirculating ion populations is consistent with the observation of long sawteeth using tangential coinjection of neutral beams in JT-60U [Nucl. Fusion 40, 1383 (2000)]]. Off-axis neutral beam heating emerges as a possible means of assisting sawtooth control in future fusion grade experiments.     

The energy spectrum of neutrons produced by cosmic ray muons in LVD

The energy spectrum of neutrons produced by cosmic ray muons in the underground detector LVD (3650 m.w.e.) is obtained for the energy range of 30–450 MeV. The spectrum is derived using the energy release spectrum of neutron interaction products in 1.5 m³ scintillation counters.