Charged Particle Spectra Research Articles

Charged hadron spectra in PHENIX

PHENIX has measured transverse momentum spectra of charged particles at mid-rapidity up to 10 GeV/c in Au+Au collisions at √s nn = 200 GeV. For central collisions, the yield at high p T is significantly suppressed comparing to binary scaled p+p data, and this suppression is stronger than observed at 130 GeV [1,2]. Above 4 GeV/c, the deficit of high momentum particles is almost independent of p T .

A comparison of methods to calculate biological effectiveness (RBE) from Monte Carlo simulations

The relative biological effectiveness (RBE) of radiation is assessed and easily calculated by Monte Carlo simulations of the passage of radiation through matter. The expression to calculate the RBE provided by microdosimetry requires the use of the energy spectrum of charged particles. This paper compares the RBE values obtained for Palladium-103 ( 103Pd) and iodine-125 ( 125I) when calculated with 2 different spectra: the electron slowing-down spectrum and the ejection spectrum. The former yields a value of 10.6%, twice the value obtained with the latter (4.5%). Which spectrum to use is an open question. A theoretical argument is presented in favor of the ejection spectrum.

The A dependence of fast-particle spectra in π +, K +, and p interactions with Al and Au targets at 250 GeV/c

The A dependence of charged-particle spectra in π+, K+, and p interactions with Al and Au targets at 250 GeV/c are presented and compared to predictions of the Quark-Gluon String Model (QGSM). It is shown that the A dependence of invariant inclusive charged-particle spectra on the Feynman variable x is very weak between Al and Au targets. The QGSM shows a larger difference between fast-particle spectra for both Al and Au targets and different beam particles. The QGSM prediction for the leading-particle spectrum over an energy range from 250 GeV to 10 TeV in pAu(Pb) reactions is in a reasonable agreement with the results of NA22 data and a cosmic-ray experiment.

A perturbative QCD analysis of charged-particle distributions in hadronic and nuclear collisions

We compute the distributions of charged particles at large transverse momenta in p p ̄ (p) , pA and AA collisions in the framework of perturbative QCD, by using collinear factorization and the modern PDFs and fragmentation functions. At the highest cms-energies the shape of the spectra measured in p p ̄ (p) collisions at large q T can be well explained. The difference between the data and the lowest-order computation is quantified in terms of a constant K-factor for each energy. The K-factor is found to systematically decrease with growing s . Also a lower limit for the partonic transverse momentum, p 0 , is extracted for each s based on the comparison with the measurements. A systematic increase of p 0 as a function of s is found. Nuclear effects in the charged-particle spectra in pA and AA collisions at RHIC and LHC are studied in the framework of collinear factorization by applying the EKS98 nuclear corrections to the parton distributions. The nuclear effects are shown to mostly enhance the computed spectra. A comparison with the recent PHENIX data from central and peripheral Au +Au collisions at RHIC is done.

Highly deformed40Caconfigurations in28Si+12C

The possible occurrence of highly deformed configurations in the $^{40}$Ca di-nuclear system formed in the $^{28}$Si + $^{12}$C reaction is investigated by analyzing the spectra of emitted light charged particles. Both inclusive and exclusive measurements of the heavy fragments (A $\geq$ 10) and their associated light charged particles (protons and $\alpha$ particles) have been made at the IReS Strasbourg {\sc VIVITRON} Tandem facility at bombarding energies of $E_{lab} (^{28}$Si) = 112 MeV and 180 MeV by using the {\sc ICARE} charged particle multidetector array. The energy spectra, velocity distributions, and both in-plane and out-of-plane angular correlations of light charged particles are compared to statistical-model calculations using a consistent set of parameters with spin-dependent level densities. The analysis suggests the onset of large nuclear deformation in $^{40}$Ca at high spin.

Application of TEPC microdosimetry to boron neutron capture therapy.

Boron neutron capture therapy (BNCT) is a bimodal radiation therapy used primarily for highly malignant gliomas. Tissue-equivalent proportional counter (TEPC) microdosimetry has proven an ideal dosimetry technique for BNCT, facilitating accurate separation of the photon and neutron absorbed dose components, assessment of radiation quality and measurement of the BNC dose. A miniature dual-TEPC system has been constructed to facilitate microdosimetry measurements with excellent spatial resolution in high-flux clinical neutron capture therapy beams. A 10B-loaded TEPC allows direct measurement of the secondary charged particle spectrum resulting from the BNC reaction. A matching TEPC fabricated from brain-tissue-equivalent plastic allows evaluation of secondary charged particle spectra from photon and neutron interactions in normal brain tissue. Microdosimetric measurements performed in clinical BNCT beams using these novel miniature TEPCs are presented, and the advantages of this technique for such applications are discussed.

Correction of measured charged-particle spectra for energy losses in the target – A comparison of three methods

The experimental facility, MEDLEY, at the The Svedberg Laboratory in Uppsala, has been constructed to measure neutron-induced charged-particle production cross-sections for (n, xp), (n, xd), (n, xt), (n, x 3He) and (n, xα) reactions at neutron energies up to 100 MeV. Corrections for the energy loss of the charged particles in the target are needed in these measurements, as well as for loss of particles. Different approaches have been used in the literature to solve this problem. In this work, a stripping method is developed, which is compared with other methods developed by Rezentes et al. and Slypen et al. The results obtained using the three codes are similar and they could all be used for correction of experimental charged-particle spectra. Statistical fluctuations in the measured spectra cause problems independent of the applied technique, but the way to handle it differs in the three codes.

Light-charged-particle evaporation from hot 31P nucleus at E*∼ 60 MeV

The inclusive energy spectra of light charged particles, such as, α, p, d and t, evaporated from the hot 31P nucleus at an excitation energy E*∼ 60 MeV, have been measured at various angles. The compound nucleus 31P has been populated using two different entrance channel configurations; i.e., 7Li (47 MeV) + 24Mg and 19F (96 MeV) + 12C reactions, leading to the same excitation energy of the compound system. It has been observed that the spectra obtained in the 7Li (47 MeV) + 24Mg reaction follow the standard statistical-model prediction with a spherical configuration of the compound nucleus. But, the spectra obtained in the 19F (96 MeV) + 12C reaction deviate from similar predictions of the statistical model both on higher- as well as on lower-energy sides. Considerable deformation was required to be incorporated in the calculation in order to reproduce the measured-energy spectra in this case. Dynamical trajectory model calculations were not found to play any significant role in explaining the differences in behaviour between the two cases under study. The observed discrepancy has been attributed to the difference in the angular-momentum distributions of the compound nuclei formed in the two reactions.

Spectral emissions and dosimetry of metal tritide particulates.

Inference of intakes and doses from inhalation of metal tritide particles has come under scrutiny because of decommissioning and decontamination of US Department of Energy facilities. Since self-absorption of radiation is very significant for larger particles, interpretation of counting results of metal tritide particles by liquid scintillation requires information about emission spectra. Similarly, inference of dose requires knowledge of charged particle and photon spectra. The PENELOPE Monte Carlo radiation transport computer code was used to compute spectral emissions and other dosimetric quantities for tritide particulates of Sc, Ti, Zr, Er, and Hf. Emission fractions, radial absorbed dose distributions, specific energy distributions and related frequency-mean specific energies and lineal energies, and the emitted spectra of electrons and bremsstrahlung photons are presented for selected particulates with diameters ranging from about 0.01 microm to 25 microm. Results characterising the effects of uncertainties associated with the composition and density of the tritides are also presented. Emission spectra are used to illustrate trends in the relationship between apparent and observed activity as a function of particle type and size. Emissions from metal tritide particles are weakly penetrating, and electron emission spectra tend to 'harden' as particle size increases. Microdosimetric considerations suggest that the radiation emitted by metal tritides can be classified as a low linear energy transfer radiation source. For cells less than about 7 microm away from the surface of a metal tritide, the primary dose component is due to electrons. However, bremsstrahlung radiation may deposit some energy tens, hundreds or even thousands of micrometres away from the surface of a tritide particle. The data and analyses presented in this report will help improve the accuracy of dose determinations for particulates of five metal tritides. Future work on the spectral emissions and dosimetry of metal tritide particulates needs to consider the contributions of so-called internal bremsstrahlung, an additional form of bremsstrahlung radiation emitted during beta decay.

The parallel cylindrical mirror electron energy analyzer

An electrostatic energy analyzer is described that allows parallel acquisition of the energy spectrum of charged particles over a wide range of energies and over the complete range of azimuthal directions. The analyzer is similar to the cylindrical mirror analyzer except that a linear potential variation is applied in the axial direction to the outer cylinder. The analyzer can also be used in a second-order focusing mode to analyze a narrow range of energies with higher energy resolution. A position sensitive detector is required, the shape of which depends on the way in which the analyzer is used. Comparisons with existing electron energy analyzers are given.

An Analyzer of Pulse Convective and Radiant Thermal Fluxes

A sensor based on a grid analyzer and a three-layer bolometer with a bismuth thermistor is described. The sensor has a time resolution of 1.5–2 μs and a sensitivity of 10–5–10–6 J/cm2. The use of grids at a retarding potential allows for the separate detection of the energy contributions of charged and neutral particles and the radiation within the absorption spectrum of the receiving plate of the bolometer. The energy spectrum of charged particles can also be determined.

Results from the First Physics Run of PHENIX at RHIC

First results from measurements of Au−Au collisions at \(\sqrt {s_{NN} } = 130\) GeV, performed with the PHENIX experiment during the initial physics run of Brookhaven National Laboratory’s Relativistic Heavy Ion Collider in summer 2000, are summarized. Global characterization of the collisions was obtained from charged-particle multiplicity and transverse energy densities. At mid-rapidity, dNch/dν and dET/dν rise steadily with the event centrality, while the ratio / remains constant. Transverse momentum spectra of charged particles up to 5 GeV/c yield a suppression of high-momentum particles in the most central events when compared to a simple scaling of binary nucleon-nucleon collisions. The scaling matches with peripheral collisions. Transverse momentum spectra of identified neutral pions from 1 to 4 GeV/c in peripheral collisions show consistency with point-like scaling with the average number of binary collisions. Yields in central collisions are significantly suppressed. Transverse momentum spectra of identified charged hadrons up to 3.5 GeV/c were measured in minimum bias events. The mass and centrality dependencies of inverse slope parameters and mean transverse momenta were determined. Inclusive spectra of electrons were measured for momenta from a few hundred MeV/c to 4 GeV/c. Inclusive photon spectra from a few hundred MeV/c to 3 GeV/c were obtained from conversion pair measurements.

Energy-loss spectra of swift ions: Beyond the Landau approximation

The paper revises the well-known simple approximation for the energy-loss spectrum of swift charged particles. The original formula by Landau is restricted to the range of path lengths where the energy loss straggling Ω 2≪T m 2 , T m being the maximum energy transfer in a collision; this is a severe limitation in the case of penetrating ions. The present work eliminates the restriction by means of a general relationship between the energy-loss spectra for true and extended collision cross-sections. Improving accuracy, this also delivers a straight generalization of Landau's argument based upon plain equivalence of the two spectra for Ω 2/T m 2→0 . Arising expressions for the spectrum remain sufficiently simple roughly up to Ω 2∼T m 2 , thus complementing existing approximations applicable for Ω 2≳T m 2 and eliminating the notorious gap at moderately small Ω 2/T m 2 . For the range Ω 2/T m 2≲1/5 , 1/3, especially simple accurate formulae arise for the peak energy loss, the half-widths, and related parameters of the spectrum. Analytical formulae are tested against numerical results confirming good accuracy and wide applicability of the former.

Deformation effects in56Ninuclei produced in28Si+28Siat 112 MeV

Velocity and energy spectra of the light charged particles (protons and $\alpha$-particles) emitted in the $^{28}$Si(E$_{lab}$ = 112 MeV) + $^{28}$Si reaction have been measured at the Strasbourg VIVITRON Tandem facility. The ICARE charged particle multidetector array was used to obtain exclusive spectra of the light particles in the angular range 15 - 150 degree and to determine the angular correlations of these particles with respect to the emission angles of the evaporation residues. The experimental data are analysed in the framework of the statistical model. The exclusive energy spectra of $\alpha$-particles emitted from the $^{28}$Si + $^{28}$Si compound system are generally well reproduced by Monte Carlo calculations using spin-dependent level densities. This spin dependence approach suggests the onset of large deformations at high spin. A re-analysis of previous $\alpha$-particle data from the $^{30}$Si + $^{30}$Si compound system, using the same spin-dependent parametrization, is also presented in the framework of a general discussion of the occurrence of large deformation effects in the A$_{CN}$ ~ 60 mass region.

Estimation of Absorbed Dose Rates in Air Based on Flux Densities of Cosmic Ray Muons and Electrons on the Ground Level in Japan

Flux densities of cosmic ray muons and electrons were estimated from the pulse height spectra of cosmic ray charged particles observed using a spherical plastic scintillation detector. In order to obtain the pulse height spectrum of cosmic ray electrons separately from that of cosmic ray muons, the pulse height spectrum of cosmic ray electrons was derived by calculating the probability distribution of energy deposited in a plastic scintillator by electrons alone, utilizing the spectrum of cosmic ray electrons given in literature. Calculation was corroborated by measurement with spherical plastic scintillator detector of cosmic ray muons alone, obtained by passing the particles through a lead shield to eliminate electrons and photons. The aggregate absorbed dose rates in air imparted by cosmic ray muons and electrons thus derived proved upon further adding the contribution of cosmic ray photons to come quite close to the total absorbed dose rate given in literature from measurements performed in Japan.

Miniature tissue-equivalent proportional counters for BNCT and BNCEFNT dosimetry.

A dual miniature tissue-equivalent proportional counter (TEPC) system has been developed to facilitate microdosimetry for Boron Neutron Capture Therapy (BNCT). This system has been designed specifically to allow the analysis of the single event charged particle spectrum in phantom in high intensity BNCT beams and to provide this microdosimetric information with excellent spatial resolution. Paired A-150 and 10B-loaded A-150 TEPCs with 12.3 mm3 collecting volumes have been constructed. These TEPCs allow more accurate neutron dosimetry than current techniques, offer a direct measure of the boron neutron capture dose, and provide a framework for predicting the biological effectiveness of the absorbed dose. Design aspects and characterization of these detectors are reviewed, along with an exposition of the advantages of microdosimetry using these detectors over conventional dosimetry methods. In addition, the utility of this technique for boron neutron capture enhancement of fast neutron therapy (BNCEFNT) is discussed.

Energy loss of charged particles interacting with simple metal surfaces

Self-consistent calculations of the energy-loss spectra of charged particles moving near a plane-bounded free-electron gas are reported. Energy-loss probabilities are obtained, within linear-response theory, from the knowledge of the density-response function of the inhomogeneous electron system. Self-consistent single-particle wave functions and energies are obtained by solving the Kohn-Sham equation of density-functional theory, and the electronic response is then computed either in the random-phase approximation or with the use of an adiabatic local-density approximation. Special emphasis is placed on the various contributions from collective and electron-hole excitations to the energy loss of charged particles moving parallel with the surface. The effect of the electronic selvage at a metal surface on the energy-loss spectra is also discussed, by comparing our full self-consistent calculations with those obtained for electron densities that drop abruptly to zero at the surface.

Calorimetric-time-of-flight technique for determination of energy spectra of particles from a high intensity pulsed proton target

A Calorimetric-Time-Of-Flight (CTOF) technique is proposed for real-time, high precision measurement of neutrons spectrum, and for evaluation of charged particles spectra and parameters of gamma radiation. By using the CTOF technique, it is possible to make these measurements in framework of the single experiment. This technique consists of a set of current mode time-of-flight instruments each having a set of organic scintillation detector placed at a different distance from a source at an interested angle from the initial proton beam direction. The CTOF technique is applicable to burst source conditions with radiation pulse duration of some dozens of nanoseconds and intensity of the order of 10 10–10 12 particles per pulse. In experiment, a cylindrical tungsten target of 20 cm in diameter, 22.5 cm thick, was irradiated with 50 ns width, 1.2 and 0.5 GeV proton pulses of 2.5×10 11 ppp. One-litre scintillators followed with 120 m long light-guides and photomultipliers were used for determining neutron and proton spectra and gamma rays flux intensity at the angle 175° from the initial proton beam direction. The method and results of this experiment are given in this paper.

Proportional counter as neutron detector

A technique to separate out the dose, and lineal energy spectra of neutrons and charged particles is described. It is based on using two proportional counters, one with a tissue equivalent wall, and the other with similar characteristics but wall made from a non-hydrogen containing material. Results of a calibration in a neutron field are also shown.

Medium corrections in the formation of light charged particles in heavy ion reactions

Within a microscopic statistical description of heavy ion collisions, we investigate the effect of the medium on the formation of light clusters. The dominant medium effects are self-energy corrections and Pauli blocking that produce the Mott effect for composite particles and enhanced reaction rates in the collision integrals. Microscopic description of composites in the medium follows the Dyson equation approach combined with the cluster mean-field expansion. The resulting effective few-body problem is solved within a properly modified Alt-Grassberger-Sandhas formalism. The results are incorporated in a Boltzmann-Uehling-Uhlenbeck simulation for heavy ion collisions. The number and spectra of light charged particles emerging from a heavy ion collision changes in a significant manner in effect of the medium modification of production and absorption processes.