Angular Distributions Of Protons Research Articles

On determining the cross section of the supposed pentaquark $ \Theta^{+}_{}$ in the reaction pp $ \rightarrow$ $ \Theta^{+}_{}$ $ \Sigma^{+}_{}$ $ \rightarrow$ pK0 $ \Sigma^{+}_{}$

This paper addresses the problem of how to extract an upper limit on the cross section for $ \Theta^+$ production via the reaction $ pp\rightarrow\Theta^+\Sigma^+$ , where the $ \Theta^+$ is assumed to decay into the $ pK^0$ subsystem. Recent data of the COSY-TOF Collaboration, namely the angular distribution of protons in the $ \Sigma^+K^0$ helicity frame and the invariant mass spectrum of the $ pK^0$ system, were scrutinised with regard to a resonance by applying the profile likelihood method. It is found that the former distribution is best suited for setting an upper limit on the $ \Theta^+$ production, which varies between 90nb for an assumed $ \Theta^+$ mass of 1500MeV/c^2 and 56nb for 1540MeV/c^2.

Channeling of protons in radially compressed carbon nanotubes

Channeling of 10 MeV protons in radially compressed chiral carbon nanotubes is considered. Monte Carlo simulation program is used for the calculation of the trajectories, energy losses and angular distributions of protons in nanotubes of various lengths, where the potential in Doyle-Turner approximation is used to describe the interaction between a proton and a nanotube. Calculations were carried out for different incident angles between proton beam and the nanotube axis. The results show that a decreased angular distribution of the beam is observed, compared with propagation through a straight nanotube, in case when it enters from the compressed end of the nanotube. The energy and spatial distribution of channeled protons in compressed nanotubes is examined.

Proton angular distribution research by a new angle-resolved proton energy spectrometer

The proton spectral and angular distributions simultaneously within the target normal direction and laser propagation direction by using an angle-resolved proton energy spectrometer are studied. For the protons generated in the interactions of 100 fs, 800 nm laser pulses with aluminum foil targets, the deviations of proton beam centers of different energies from the target normal direction towards the laser propagation direction are different. This is probably because of the toroidal magnetic fields generated at the rear target surface, which deflect protons transversely. As a result, protons in low energy range have large deviation angles, protons in middle energy range have the smallest deviation angles, while protons in high energy tail have large deviation angles.

Channeling and energy losses of 10 MeV protons in straight chiral carbon nanotube bundles

Channeling of 10MeV protons in straight chiral single carbon nanotubes (6,4) and (11,9), as well as in corresponding nanotube bundles is considered. Monte Carlo simulation program is used for the calculation of the trajectories, energy losses and angular distributions of protons in nanotubes and bundles of various lengths and different incident angles. The energy distribution of protons channeled through single carbon nanotubes, as well as through corresponding nanotube bundles are also examined.

Proton recoil energy and angular distribution of neutron radiativeβ−decay

We analyze the proton recoil energy and angular distribution of the radiative ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of the neutron to leading order in the large baryon mass expansion by taking into account the contributions of the proton-photon correlations. We show that the account for the proton-photon correlations does not contradict the description of the radiative corrections to the lifetime of the neutron and the proton recoil energy spectrum of the neutron ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay in terms of the functions $(\ensuremath{\alpha}/\ensuremath{\pi}){g}_{n}({E}_{e})$ and $(\ensuremath{\alpha}/\ensuremath{\pi}){f}_{n}({E}_{e})$, where ${E}_{e}$ is the electron energy. In addition we find that the contributions of the proton-photon correlations in the radiative ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of the neutron to the proton recoil asymmetry $C$ are of order ${10}^{\ensuremath{-}4}$. They make the contributions of the radiative corrections to the proton recoil asymmetry $C$ symmetric with respect to a change ${A}_{0}\ensuremath{\leftrightarrow}{B}_{0}$, where ${A}_{0}$ and ${B}_{0}$ are the correlation coefficients of the neutron ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay.

Study ofe+e−→pp¯via initial-state radiation atBABAR

The process e+e- --> p anti-p gamma is studied using 469 fb-1 of integrated luminosity collected with the BABAR detector at the PEP-II collider, at an e+e- center-of-mass energy of 10.6 GeV. From the analysis of the p anti-p invariant mass spectrum, the energy dependence of the cross section for e+e- --> p anti-p is measured from threshold to 4.5 GeV. The energy dependence of the ratio of electric and magnetic form factors, |G_E/G_M|, and the asymmetry in the proton angular distribution are measured for p anti-p masses below 3 GeV. We also measure the branching fractions for the decays J/psi --> p anti-p and psi(2S) --> p anti p.

Elastic scattering of protons from9C with a 290 MeV/nucleon9C beam

The angular distribution of proton-${}^{9}$C elastic scattering at 277--300 MeV/nucleon was measured with a newly designed recoil proton spectrometer. The angular distribution was analyzed using the relativistic impulse approximation. The root-mean-square matter radius of ${}^{9}$C was deduced to be $2.{43}_{\ensuremath{-}0.28}^{+0.55}$ fm with different two-parameter Fermi density distributions for protons and neutrons.

The influence of target material and thickness on proton energy and angular distribution

The paper has studied the influence of target material and thickness on energy and angular distributions of the protons generated by using an 800 nm, 60 fs, 0.24 J laser pulse to irradiate solid target foils. The results show that the initial density and thickness of the targets will affect the formation of the acceleration sheath fields in the target normal direction. For the same target thickness, using lower density target materials can obtain a higher proton maximum energy. However, lower density targets tend to be deformed due to the shock waves launched by the laser pulses, making the proton spatial distribution more divergent.

NUCLEAR STRUCTURE OF 97Mo FROM THE (d, p) REACTION

The reaction 96 Mo (d, p)97 Mo has been studied at 12 MeV using the tandem Van de Graaff accelerator and a multi-channel magnetic spectrograph at the Atomic Weapon Research Establishment, Aldermaston, England. Angular distributions of protons are measured at 12 different angles from 5° to 87.5° at an interval of 7.5° and the reaction products are detected in nuclear emulsion plates. Thirty levels in the energy range from 0.000 to 2.458 MeV have been observed and absolute differential cross-sections for these levels have been measured. The data are analyzed in terms of the distorted-wave Born approximation (DWBA) theory of the direct reactions, and spins, parities and spectroscopic factors are deduced for various levels. Ambiguity in the spin assignments of d5/2 and d3/2 which is allowed in ln = 2(d, p) transition is removed by using the corresponding L-value of the 95 Mo (t, p)97 Mo reaction at Et = 12 MeV . Determined value of the sum of spectroscopic factors for transfers of d5/2 neutrons suggests configuration mixing in the ground state of 96 Mo . The properties of the levels in 97 Mo are compared with previous experimental results and theoretical predictions.

Identification of the types of carbon nanotubes using donut effects

We investigate the angular distributions of protons of initial energy 10MeV after channeling through a (6,4), (8,6), (11,9) and (15,10) single-wall carbon nanotube, each of length 1μm. The interaction between the proton and nanotube atoms is described by Doyle–Turner interaction potential. The angular distributions of channeled protons are generated using a Monte Carlo computer simulation code, based on the numerical solutions of the proton equations of motion in the transverse position plane. As the proton incident angle increases and approaches the critical angle for channeling, a ring-like structure is developed in the angular distribution known as the donut effect. Its appearance in the proton angular distribution is highly dependent on the size and type of nanotube. Thus, we propose that the donut structure produced by a given carbon nanotube could act as a sort of “fingerprint”, allowing one to identify the nanotube type.

Dynamical effects in proton breakup from exotic nuclei

We study dynamical effects in proton breakup from a weakly bound state in an exotic nucleus on a heavy target. The Coulomb interactions between the proton and the core and between the proton and the target are treated to all orders, including also the full multipole expansion of the Coulomb potential. The dynamics of proton nuclear and Coulomb breakup is compared to that of an equivalent neutron of higher binding energy in order to elucidate the differences with the well-understood neutron breakup mechanism. A number of experimentally measurable observables such as parallel momentum distributions, proton angular distributions, and total breakup cross sections are calculated. With respect to nuclear breakup it is found that a proton behaves exactly as a neutron of higher binding energy. The extra ``effective energy'' is caused by the combined core-target Coulomb barrier. In Coulomb breakup we distinguish the effect of the core-target Coulomb potential (called the recoil effect), with respect to which the proton behaves, again, as a more bound neutron, from the direct proton-target Coulomb potential. The latter gives cross sections about an order of magnitude larger than the recoil term. The two effects give rise to complicated interferences in the parallel momentum distributions. They are instead easily separable in the proton angular distributions, which are therefore suggested as a very useful observable for future experimental studies.

A simulation of neutron interaction from Am–Be source with the CR-39 detector

Abstract Presented in this paper is a simulation of the interaction of neutrons emitted from a cylindrical Am–Be source with a CR-39 detector. A Fortran90 program, called Neutron.f90, has been written to determine the specifications of secondary particles (alpha particle or proton) and the kinematics of the interactions. A Monte Carlo method was used to simulate which interactions occurred with the constituents of the CR-39 detector, H, C and O atoms. Due to the detector composition, elastic and nonelastic scattering of neutrons is possible. In this paper, nonelastic scattering includes: inelastic scattering; the emission of an alpha particle (n,α) reaction and the emission of a proton (n,p) reaction. Cross sections of other reactions are very small and negligible in comparison with the above mentioned. The energy deposited per unit mass per one neutron was calculated. In addition the contribution to the energy deposited by the alpha particles and protons were determined separately. The program Neutron.f90 computes the coordinates of points in which interactions occur i.e. where secondary particles appear. The energy and angular distributions of protons are also represented in this paper. Another Fortran90 program, called Track_Visibility.f90, was written to calculate the number of visible proton tracks and to calculate the energy deposited per one neutron per one visible track.

Systematic study of the pp $ \rightarrow$ pp$ \omega$ reaction

A systematic study of the production of omega-mesons in proton-proton-collisions was carried out in a kinematically complete experiment at three excess energies(epsilon= 92, 128, 173MeV). Both protons were detected using the large-acceptance COSY-TOF spectrometer at an external beam line at the Cooler Synchrotron COSY at Forschungszentrum J\"ulich. The total cross section, angular distributions of both omega-mesons and protons were measured and presented in various reference frames such as the overall CMS, helicity and Jackson frame. In addition, the orientation of the omega-spin and invariant mass spectra were determined. We observe omega-production to take place dominantly in Ss and Sp final states at epsilon = 92, 128 MeV and, additionally, in Sd at epsilon= 173 MeV. No obvious indication of resonant omega-production via N^*-resonances was found, as proton angular distributions are almost isotropic and invariant mass spectra are compatible with phase space distributions. A dominant role of ^3P_1 and ^1S_0 initial partial waves for omega-production was concluded from the orientation of the decay plane of the omega-meson. Although the Jackson angle distributions in the omega-p-Jackson frame are anisotropic we argue that this is not an indication of a resonance but rather a kinematical effect reflecting the anisotropy of the omega angular distribution. The helicity angle distribution in the omega-p-helicity frame shows an anisotropy which probably reflects effects of the omega angular momenta in the final state; this observable may be, in addition to the orientation of the omega decay plane, the most sensitive one to judge the validity of theoretical descriptions of the production process.

TIARA: A large solid angle silicon array for direct reaction studies with radioactive beams

A compact, quasi- 4 π position sensitive silicon array, TIARA, designed to study direct reactions induced by radioactive beams in inverse kinematics is described here. The Transfer and Inelastic All-angle Reaction Array (TIARA) consists of 8 resistive charge division detectors forming an octagonal barrel around the target and a set of double-sided silicon-strip annular detectors positioned at each end of the barrel. The detector was coupled to the γ -ray array EXOGAM and the spectrometer VAMOS at the GANIL Laboratory to demonstrate the potential of such an apparatus with radioactive beams. The N ( d , p ) 14 N 15 reaction, well known in direct kinematics, has been carried out in inverse kinematics for that purpose. The observation of the N 15 ground state and excited states at 7.16 and 7.86 MeV is presented here as well as the comparison of the measured proton angular distributions with DWBA calculations. Transferred l-values are in very good agreement with both theoretical calculations and previous experimental results obtained in direct kinematics.

Effects of the Micro-hole Target Structures on the Laser-driven Energetic Proton Generation

Micro-hole targets are studied to generate energetic protons from laser-thin foil targets by using 2-dimensional particle-in-cell simulations. By using a small hole, the maximum energy of the accelerated proton is increased to 4 times higher than that from a simple planar target. The main proton acceleration mechanism of the hole-targets is the electrostatic field created between the fast electrons accelerated by the laser pulse ponderomotive force combined with the vacuum heating and the target rear surface. But in this case, the proton angular distribution shows double-peak shape, which means poor collimation and low current density. By using a small cone-shaped hole, the maximum proton energy is increased 3 times higher than that from a simple planar target. Furthermore, the angular distribution of the accelerated protons shows good collimation.

A fine structure in angular distributions of protons transmitted through insulating capillaries

The processes of interaction of accelerated protons with the surface of insulating capillaries have been investigated to determine the character of motion of particles during such an interaction. The angular distributions of 240-keV protons transmitted through glass capillaries have been measured, and splitting of the distribution into a series of lines equally spaced from each other is revealed.

The role of various mechanisms in the formation of the 12B nucleus in the 10B(t, p)12B reaction

The angular distribution of protons from the 10B(t, p)12B reaction is analyzed within the framework of three mechanisms: dineutron cluster stripping, heavy 9Be cluster stripping, and successive time-delay neutron transfer. The dineutron cluster stripping and successive neutron transfer mechanisms are shown to be of considerable importance. Wave functions of the relative motion of the 10B and dineutron, as well as of the 10B and both neutrons, in the 12B ground state are reconstructed, which revealed that the neutron halo in the 12B nucleus practically does not manifest itself in the 10B(t, p)12B reaction.

Single-neutron excitations in neutron-richGe83andSe85

The $^{2}\mathrm{H}$($^{82}\mathrm{Ge}$,$p$)$^{83}\mathrm{Ge}$ and $^{2}\mathrm{H}$($^{84}\mathrm{Se}$,$p$)$^{85}\mathrm{Se}$ reactions were studied with radioactive beams of $^{82}\mathrm{Ge}$ and $^{84}\mathrm{Se}$ at beam energies of ${E}_{\mathrm{beam}}=330$ and 380 MeV, respectively. Excitation energies, proton angular distributions, and asymptotic normalization coefficients have been determined for the lowest lying states of $^{83}\mathrm{Ge}$ and $^{85}\mathrm{Se}$. Spectroscopic factors have also been extracted under normal assumptions of the bound-state potential properties in the distorted waves Born approximation analysis. However, the peripheral character of the measurements leads to large uncertainties in this extraction. Shell-model calculations have been performed in the region above $^{78}\mathrm{Ni}$, comparing the single-particle properties of the even-$Z,N=51$ nuclei up to $^{91}\mathrm{Zr}$ and including $^{83}\mathrm{Ge}$ and $^{85}\mathrm{Se}$. Direct-semidirect neutron capture calculations to $^{83}\mathrm{Ge}$ and $^{85}\mathrm{Se}$ have also been performed using the spectroscopic input from these $(d,p)$ reaction measurements.

Proton sputtering from polycrystalline Al surface interacting with highly charged ions at grazing incidence angle

Sputtering processes of protons from a polycrystalline Al surface interacting with Arq+ (q=3–14) ions at a grazing incidence angle (∼0.5°) were investigated. The intensity of protons (IH) detected in coincidence with scattered Ar atoms was measured as a function of q. IH saturated at q⩾10, although it increased rapidly with q at 3⩽q⩽8. The angular distribution of protons with low kinetic energy (⩽2eV) began to deviate from the cosine distribution and assumed a rather flat equidistribution as q increased. To analyze the sputtering processes of protons at the grazing incidence angle, a modified model of the “above-surface potential sputtering model” was proposed by considering image acceleration of projectile ions.

Proton acceleration from microdroplet spray by weakly relativistic femtosecond laser pulses

Angular distribution of protons is measured from ethanol droplet spray irradiated by linearly polarized 150 fs laser pulses at an intensity of 1.1 x 10(16)W/cm2. Fast protons (with energies >16 keV ) with an anisotropic distribution can be observed only in or near the polarization plane of the laser fields, while the slow protons (with energies <or=16 keV ) emit with nearly an isotropic distribution. Two-dimensional particle-in-cell simulations suggest that three groups of protons originate from different acceleration regimes in the laser-droplet interaction. The first group with the highest energies is accelerated backwards by the anisotropic charge-separation field near the front surface (laser-droplet interaction side) due to the resonance absorption; the second group (forward emission) is generated by the target-normal sheath acceleration mechanism; and the third group, with the lowest energies, is accelerated by the hydrodynamic expansion of the droplet plasmas.