In Colombia, medical physics started formally about 3 decades ago. Two master’s programs in medical physics initiated activities at two different universities. In particular, the master’s program at the Pontificia Universidad Javeriana has been underway since 2012, and taking into account its projections, a team was established in 2015 in collaboration with the Universidad Distrital Francisco José de Caldas to conduct basic research on cancer treatment using neutron capture therapy (NCT). The primary goal of our initiative is to create the infrastructure required to adapt new technologies in our universities in the future. The long-term objective is to use neutron radiation to study not only NCT but also biomolecules, membranes, and materials. This will require the commissioning of an actual nuclear facility. Our group has been exclusively focused on carrying out calculations with GEANT4 because of its characteristics as open-source software, its accessibility, and its ample worldwide use and validation in the particle physics, nuclear physics, and medical physics communities. In this work, we present some results of our preliminary design for the ion accelerator column of a compact neutron generator. Also, we present the characterization of the kinematical and dose distributions of boron neutron capture processes using Geant4.

We report a new measurement of the beam-spin asymmetry, Sigma, for the (gamma) over right arrown -> K+Sigma(-) reaction using quasi-free neutrons in a liquid-deuterium target. The new dataset includes data at previously unmeasured photon energy and angular ranges, thereby providing new constraints on partial wave analyses used to extract properties of the excited nucleon states. The experimental data were obtained using the CEBAF Large Acceptance Spectrometer (CLAS), housed in Hall B of the Thomas Jefferson National Accelerator Facility (JLab). The CLAS detector measured reaction products from a liquid-deuterium target produced by an energy-tagged, linearly polarised photon beam with energies in the range 1.1 to 2.3 GeV. Predictions from an isobar model indicate strong sensitivity to N(1720)3/2(+), Delta(1900)1/2(-), and N(1895)1/2(-), which corroborates results from a recent combined analysis of all K Sigma channels. When our data are incorporated in the fits of partial-wave analyses, one observes significant changes in gamma-n couplings of resonances which have small branching ratios to the pi N channel. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).

The COmpact detectoR for the Eic (CORE) Proposal was submitted to the EIC "Call for Collaboration Proposals for Detectors". CORE comprehensively covers the physics scope of the EIC Community White Paper and the National Academies of Science 2018 report. The design exploits advances in detector precision and granularity to minimize size. The central detector includes a 3Tesla, 2.5m solenoid. Tracking is primarily silicon. Electromagnetic calorimetry is based on the high performance crystals. Ring-imaging Cherenkov detectors provide hadronic particle identification.

We report a new measurement of the beam-spin asymmetry $\boldsymbol{\Sigma}$ for the $\vec{\gamma} n \rightarrow K^+\Sigma^-$ reaction using quasi-free neutrons in a liquid-deuterium target. The new dataset includes data at previously unmeasured photon energy and angular ranges, thereby providing new constraints on partial wave analyses used to extract properties of the excited nucleon states. The experimental data were obtained using the CEBAF Large Acceptance Spectrometer (CLAS), housed in Hall B of the Thomas Jefferson National Accelerator Facility (JLab). The CLAS detector measured reaction products from a liquid-deuterium target produced by an energy-tagged, linearly polarised photon beam with energies in the range 1.1 to 2.3 GeV. Predictions from an isobar model indicate strong sensitivity to $N(1720)3/2^+$, $\Delta(1900)1/2^-$, and $N(1895)1/2^-$, with the latter being a state not considered in previous photoproduction analyses. When our data are incorporated in the fits of partial-wave analyses, one observes significant changes in $\gamma$-$n$ couplings of the resonances which have small branching ratios to the $\pi N$ channel.

The reaction γp→K+Λ(1520) using photoproduction data from the CLAS g12 experiment at Jefferson Lab is studied. The decay of Λ(1520) into two exclusive channels, Σ+π− and Σ−π+, is studied from the detected K+, π+, and π− particles. A good agreement is established for the Λ(1520) differential cross sections with the previous CLAS measurements. The differential cross sections as a function of center-of-mass angle are extended to higher photon energies. Newly added are the differential cross sections as a function of invariant four-momentum transfer t, which is the natural variable to use for a theoretical model based on a Regge-exchange reaction mechanism. No new N* resonances decaying into the K+Λ(1520) final state are found.

We report measurements of π+ and π0 meson photoproduction from longitudinally spin-polarised protons by an energy tagged (0.73-2.3 GeV) and linearly polarised photon beam. A close to complete solid angle coverage for the reaction products was provided by the CEBAF Large Acceptance Spectrometer at Jefferson Laboratory. The double-polarisation observable G is extracted from Maximum Likelihood fits to the data, enabling the first accurate determination for the reaction γ→p→→π+n, while also significantly extending the kinematic coverage for γ→p→→π0p. This large data set provides an important constraint on the properties and spectrum of excited nucleon states decaying to Nπ in the mass range from 1.4 to 2.2 GeV, as well as for background (non-resonant) photoproduction processes. The considerable improvement achieved in the description of the observable G within the SAID and Bonn-Gatchina approaches after implementation of our data, illustrates that the partial-wave analyses now significantly extend the knowledge on Nπ photoproduction amplitudes at W>1.8 GeV. A partial-wave analysis using the new high-precision data set has a large impact on the extracted properties of high-spin nucleon excited states.

Strange matter is believed to exist in the cores of neutron stars based on simple kinematics. If this is true, then hyperon-nucleon interactions will play a significant part in the neutron star equation of state (EOS). Yet, compared to other elastic scattering processes, there is very little data on Λ-N scattering. This experiment utilized the CLAS detector to study the Λ p →Λ p elastic scattering cross section in the incident Λ momentum range 0.9-2.0 GeV/c. This is the first data on this reaction in several decades. The new cross sections have significantly better accuracy and precision than the existing world data, and the techniques developed here can also be used in future experiments.

The quark structure of the f_{2}(1270) meson has, for many years, been assumed to be a pure quark-antiquark (qq[over ¯]) resonance with quantum numbers J^{PC}=2^{++}. Recently, it was proposed that the f_{2}(1270) is a molecular state made from the attractive interaction of two ρ mesons. Such a state would be expected to decay strongly to final states with charged pions due to the dominant decay ρ→π^{+}π^{-}, whereas decay to two neutral pions would likely be suppressed. Here, we measure for the first time the reaction γp→π^{0}π^{0}p, using the CEBAF Large Acceptance Spectrometer detector at Jefferson Lab for incident beam energies between 3.6 and 5.4 GeV. Differential cross sections, dσ/dt, for f_{2}(1270) photoproduction are extracted with good precision due to low backgrounds and are compared to theoretical calculations.

Strange matter is believed to exist in the cores of neutron stars based on simple kinematics. If this is true, then hyperon-nucleon interactions will play a significant part in the neutron star equation of state. Yet, compared to other elastic scattering processes, there is very little data on Λ-N scattering. This experiment utilized the CEBAF Large Acceptance Spectrometer (CLAS) detector to study the Λp→Λp elastic scattering cross section in the incident Λ momentum range 0.9-2.0  GeV/c. These are the first data on this reaction since the 1970s. The new cross sections have significantly better accuracy and precision than the existing world data, and the techniques developed here can also be used in future experiments.

We report a measurement of a beam–target double-polarisation observable (E) for the γ→n→(p)→K+Σ−(p) reaction. The data were obtained impinging the circularly-polarised energy-tagged photon beam of Hall B at Jefferson Lab on a longitudinally-polarised frozen-spin hydrogen deuteride (HD) nuclear target. The E observable for an effective neutron target was determined for centre-of-mass energies 1.70≤W≤2.30 GeV, with reaction products detected over a wide angular acceptance by the CLAS spectrometer. These new double-polarisation data give unique constraints on the strange decays of excited neutron states. Inclusion of the new data within the Bonn-Gatchina theoretical model results in significant changes for the extracted photocouplings of a number of established nucleon resonances. Possible improvements in the PWA description of the experimental data with additional "missing" resonance states, including the N(2120)3/2− resonance, are also quantified.

Photoproduction cross sections are reported for the reaction gamma p -> p eta using energy-tagged photons and the CLAS spectrometer at Jefferson Laboratory. The eta mesons are detected in their dominant charged decay mode, eta -> pi(+)pi(-) pi(0), and results on differential cross sections are presented for incident photon energies between 1.2 and 4.7 GeV. These new eta photoproduction data are consistent with earlier CLAS results but extend the energy range beyond the nucleon resonance region into the Regge regime. The normalized angular distributions are also compared with the experimental results from several other experiments, and with predictions of eta-MAID 2018 and the latest solution of the Bonn-Gatchina coupled-channel analysis. Differential cross sections d sigma / dt are presented for incident photon energies E gamma > 2.9 GeV (W > 2.5 GeV), and compared with predictions which are based on Regge trajectories exchange in the t -channel (Regge models). The data confirm the expected dominance of rho, omega vector-meson exchange in an analysis by the Joint Physics Analysis Center.

We present the first measurement of the reaction gamma p -> a(2) (1320)(0) p in the photon energy range 3.5-5.5 GeV and four-momentum transfer squared 0.2 < -t < 2.0 GeV2. Data were collected with the CEBAF Large Acceptance Spectrometer detector at the Thomas Jefferson National Accelerator Facility. The a(2) resonance was detected by measuring the reaction gamma p -> pi(0)eta p Tip and reconstructing the pi(0)eta invariant mass. The most prominent feature of the differential cross section is a dip at -t approximate to 0.55 GeV2. This can be described in the framework of Regge phenomenology, where the exchange degeneracy hypothesis predicts a zero in the reaction amplitude for this value of the four-momentum transfer.

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This paper determines analytically the velocity field induced by a configuration of linked vortices, with the aim of finding the translational velocity of such a configuration. The linked-vortex configuration consists of two vortices; the vortices are thin tubes of circular cross section lying on the surface of an immaterial torus of small aspect ratio r1r0 (where r1 is the cross section radius of a torus and r0 is its centerline radius). The induced velocity field has been found based on the vector potential associated with the Biot-Savart law by using a multipolar expansion; the comparison of this field with the material condition on the surface of the vortices allows one to calculate the translational velocity. The solution obtained retains effects to first order at the multipolar expansion, which corresponds to the effects the vortex curvature has at the vorticity distribution on its cross section. This solution agrees with the numerical results in the range of 2%. The method presented is generalized to the case of n linked vortices.

El uso de nucleidos de gadolinio como agentes de captura de neutrones en la terapia de cáncer por captura neutrónica es de gran interés debido principalmente a su alta sección eficaz de 225.000 barns. El espectro del estado final de la reacción contiene 158-gadolinio (158Gd), emisión de fotones (rayos X y rayos gamma) y electrones (conversión interna y Auger). Este espectro ofrece una física muy rica y de enorme potencial para la eliminación de células tumorales debido a su alta transferencia lineal de energía. En este trabajo presentamos simulaciones de este proceso, realizadas en las últimas seis versiones de Geant4 (10.00.p04, 10.01.p03, 10.02.p03, 10.03.p03, 10.04.p03 y 10.05.p01). Tomando en cuenta que para este trabajo nos interesan particularmente los neutrones de baja energía (energías < 20 MeV), usaremos el paquete G4NeutronHP. Finalmente obtenemos el conteo de eventos, la energía promedio y las distribuciones angulares (theta y phi) de las partículas en el estado final, encontrando, de esta manera, que para neutrones de baja energía, el estudio de la reacción de captura neutrónica por 158Gd es viable con Geant4.

Background: Measurements of polarization observables for the reactions (cid:2) γp → K + (cid:3) and (cid:2) γp → K + (cid:4) 0 have been performed. This is part of a program of measurements designed to study the spectrum of baryon resonances in particular, and nonperturbative QCD in general. Purpose: The accurate measurement of several polarization observables provides tight constraints for phenomenological fits, which allow the study of strangeness in nucleon and nuclear systems. Beam-recoil observables for the (cid:2) γp → K + (cid:4) 0 reaction have not been reported before now. Method: The measurements were carried out using linearly polarized photon beams incident on a liquid hydrogen target, and the CLAS detector at the Thomas Jefferson National Accelerator Facility. The energy range of the results is 1 . 71 < W < 2 . 19 GeV, with an angular range − 0 . 75 < cos θ ⋆K < + 0 . 85. Results: The observables extracted for both reactions are beam asymmetry (cid:4) , target asymmetry T , and the beam-recoil double polarization observables O x and O z . Conclusions: Comparison with theoretical fits indicates that, in the regions where no previous data existed, the new data contain significant new information, and strengthen the evidence for the set of resonances used in the latest Bonn-Gatchina fit. DOI:

This Article is brought to you for free and open access by the Physics at ODU Digital Commons. It has been accepted for inclusion in Physics Faculty Publications by an authorized administrator of ODU Digital Commons. For more information, please contact digitalcommons@odu.edu. Repository Citation CLAS Collaboration; Amaryan, M. J.; Careccia, S. L.; Dodge, G. E.; Hyde, C. E.; Kuhn, S. E.; Mayer, M.; Nepali, C. S.; Niroula, M. R.; Seraydaryan, H.; Tkachenko, S.; Weinstein, L.B.; and Zhang, J., "Photodisintegration of 4HE into p+t" (2009). Physics Faculty Publications. 353. https://digitalcommons.odu.edu/physics_fac_pubs/353

25 a 29 de septiembre de 2017 Facultad de Ciencias y Educación Proyecto Curricular de Licenciatura en Física Universidad Distrital Francisco José de Caldas