Photon Production Data Research Articles

Parton distribution functions of the charged pion within the xFitter framework

We present the first open-source analysis of parton distribution functions (PDFs) of charged pions using xFitter, an open-source QCD fit framework to facilitate PDF extraction and analyses. Our calculations are implemented at next-to-leading order (NLO) using APPLgrids generated by MCFM generator. Using currently available Drell-Yan and photon production data, we find the valence distribution is well constrained; however, the considered data are not sensitive enough to unambiguously determine sea and gluon distributions. Fractions of momentum carried by the valence, sea and gluon components are discussed, and we compare with the results of JAM collaboration and the GRV group.

Direct photon production and PDF fits reloaded

Direct photon production in hadronic collisions provides a handle on the gluon PDF by means of the QCD Compton scattering process. In this work we revisit the impact of direct photon production on a global PDF analysis, motivated by the recent availability of the next-to-next-to-leading (NNLO) calculation for this process. We demonstrate that the inclusion of NNLO QCD and leading-logarithmic electroweak corrections leads to a good quantitative agreement with the ATLAS measurements at 8 and 13 TeV, except for the most forward rapidity region in the former case. By including the ATLAS 8 TeV direct photon production data in the NNPDF3.1 NNLO global analysis, we assess its impact on the medium-x gluon. We also study the constraining power of the direct photon production measurements on PDF fits based on different datasets, in particular on the NNPDF3.1 no-LHC and collider-only fits. We also present updated NNLO theoretical predictions for direct photon production at 13 TeV that include the constraints from the 8 TeV measurements.

Prompt photon production and photon-jet correlations at the LHC

Next-to-leading order predictions matched to parton showers are compared with recent ATLAS data on isolated photon production and CMS data on associated photon and jet production in pp and pPb collisions at different centre-of-mass energies of the LHC. We find good agreement and, as expected, considerably reduced scale uncertainties compared to previous theoretical calculations. Predictions are made for the ratio of inclusive photons over decay photons Rγ , an important quantity to evaluate the significance of additional photon sources, e.g. thermal radiation from a Quark-Gluon-Plasma, and for distributions in the parton momentum fraction in lead ions xPbobs, that could be determined by ALICE, ATLAS, CMS and LHCb in ongoing analyses of photon+jet production in pPb collisions at sqrt{s_{N N}} = 5.02 TeV. These data should have an important impact on the determination of nuclear effects such as shadowing at low x.

Testing of the ABBN-RF multigroup data library in photon transport calculations

Gamma radiation is produced via both of nuclear fuel and shield materials. Photon interaction is known with appropriate accuracy, but secondary gamma ray production known much less. The purpose of this work is studying secondary gamma ray production data from neutron induced reactions in iron and lead by using MCNP code and modern nuclear data as ROSFOND, ENDF/B-7.1, JEFF-3.2 and JENDL-4.0. Results of calculations show that all of these nuclear data have different photon production data from neutron induced reactions and have poor agreement with evaluated benchmark experiment. The ABBN-RF multigroup cross-section library is based on the ROSFOND data. It presented in two forms of micro cross sections: ABBN and MATXS formats. Comparison of group-wise calculations using both ABBN and MATXS data to point-wise calculations with the ROSFOND library shows a good agreement. The discrepancies between calculation and experimental C/E results in neutron spectra are in the limit of experimental errors. For the photon spectrum they are out of experimental errors. Results of calculations using group-wise and point-wise representation of cross sections show a good agreement both for photon and neutron spectra.

Variance reduction adjustment in Monte Carlo TRIPOLI-4® neutron gamma coupled calculations

This paper presents a diagnosis tool for the users of the TRIPOLI-4 Monte Carlo transport code. The aim is to facilitate the adjustment of the variance reduction scheme when dealing with coupled neutron-photon simulations. Up to now, neutron and photon importance functions have been generated independently by TRIPOLI-4 when transport biasing for both particles was necessary, leading to further adjustments by the user after running a first coupled simulation. The idea is here to combine in a fast step the TRIPOLI-4 photon importance map on the one hand, and the photon production data used by the simulation on the other hand, so as to provide at once a better knowledge of important points of neutron phase space with respect to photon tallies. The highest neutron importance mesh cells are then derived and optionally displayed on geometry graphs. The user's intervention consists then in different possible options defining the neutron variance reduction scheme of the TRIPOLI-4 coupled simulation, in the light of the previous diagnosis results. Finally, coupled neutron-photon simulations involving polyethylene and stainless steel slabs are investigated: an example of use of this diagnosis tool is provided and figures of merit related to photon tallies are then compared.

Needs of Accurate Prompt and Delayed γ-spectrum and Multiplicity for Nuclear Reactor Designs

Abstract The local energy photon deposit must be accounted accurately for Gen-IV fast reactors, advanced light-water nuclear reactors (Gen-III+) and the new experimental Jules Horowitz Reactor (JHR). The γ energy accounts for about 10% of the total energy released in the core of a thermal or fast reactor. The γ-energy release is much greater in the core of the reactor than in its structural sub-assemblies (such as reflector, control rod followers, dummy sub-assemblies). However, because of the propagation of γ from the core regions to the neighboring fuel-free assemblies, the contribution of γ energy to the total heating can be dominant. For reasons related to their performance, power reactors require a 7.5% (1σ) uncertainty for the energy deposition in non-fuelled zones. For the JHR material-testing reactor, a 5% (1 s) uncertainty is required in experimental positions. In order to verify the adequacy of the calculation of γ-heating, TLD and γ-fission chambers were used to derive the experimental heating values. Experimental programs were and are still conducted in different Cadarache facilities such as MASURCA (for SFR), MINERVE and EOLE (for JHR and Gen-III+ reactors). The comparison of calculated and measured γ-heating values shows an underestimation in all experimental programs indicating that for the most γ-production data from 239Pu in current nuclear-data libraries is highly suspicious.The first evaluation priority is for prompt γ-multiplicity for U and Pu fission but similar values for otheractinides such as Pu and U are also required. The nuclear data library JEFF3.1.1 contains most of the photon production data. However, there are some nuclei for which there are missing or erroneous data which need to be completed or modified. A review of the data available shows a lack of measurements for conducting serious evaluation efforts. New measurements are needed to guide new evaluation efforts which benefit from consolidated modeling techniques.

Direct hadron production in hadronic collisions

The scaling behavior of the invariant production cross section is a powerful tool in order to probe the dynamics of particle production. Here, we investigate the scaling properties of large- p ⊥ hadron, jet and prompt photon production in hadronic collisions by comparing systematically world data to NLO QCD predictions. In the hadron sector a significant discrepancy is reported, while prompt photon and jet production data prove in agreement with leadingtwist expectations. We interpret these results as coming from a non-negligible contribution of higher-twist processes, in which the hadron is produced directly in the hard subprocess. Predictions at RHIC are successfully compared to PHENIX preliminary measurements and LHC predictions are given.

Jet energy loss, photon production, and photon-hadron correlations at energies available at the BNL Relativistic Heavy Ion Collider (RHIC)

Jet energy loss, photon production and photon-hadron correlations are studied together at high transverse momentum in relativistic heavy-ion collisions at RHIC energies. The modification of hard jets traversing a hot and dense nuclear medium is evaluated by consistently taking into account induced gluon radiation and elastic collisions. The production of high transverse momentum photons in Au+Au collisions at RHIC is calculated by incorporating a complete set of photon-production channels. Comparison with experimental photon production and photon-hadron correlation data is performed, using a (3+1)-dimensional relativistic hydrodynamic description of the thermalized medium created in these collisions. Our results demonstrate that the interaction between the hard jets and the soft medium is important for the study of photon production and of photon-hadron correlation at RHIC.

The Role of Fast Neutron-Induced Photon Production Data in the Search for Oil

The sensitivity of coupled neutron-photon transport simulations to the underlying nuclear data is studied for oil well logging applications using the Monte Carlo radiation transport code MCNP4C. Results obtained with the JEF-2.2, ENDF/B-VI.5, and JENDL-3.2 data libraries reveal large discrepancies, confirming immediately the importance of well-established nuclear data. In order to refine this conclusion, the impact of several nuclides is determined by varying their neutron and photon total cross sections. As a next step, neutron cross sections and photon production cross sections are modified per reaction channel to identify the most important nuclear reactions playing a role in C/O logging. The influence of neutron and photon angular distributions is studied as well. The outcome of this analysis is a list of nuclear reactions that have a significant impact on borehole logging tool simulations in different environments and, therefore, would deserve much attention in the construction of a new library for oil well logging.

Neutronics benchmark experiment on tungsten

In order to validate neutron cross sections for W, a benchmark experiment was carried out at the Frascati Neutron Generator (FNG), that consisted of the irradiation with 14 MeV neutrons of a tungsten block. Neutron flux and gamma heating were measured inside the block. The results were analysed with the Monte Carlo code MCNP-4C using for W, Fe and Ni the cross sections derived from EFF-2.4 and FENDL-2.0. In the neutron flux case, most of the calculations were in agreement with the experimental data within the total uncertainty using EFF-2.4, while they underestimated the fast neutron flux with increasing depth when using FENDL-2 cross sections. A strong discrepancy was found in the photon production data from the EFF-2.4 and FENDL-2 libraries, producing different values for the gamma heating in the two cases. FENDL-2 calculations showed better agreement with the measurements.

High-Resolution Measurements and Calculations of Photon-Production Cross Sections for 16O(n,xγ) Reactions Induced by Neutrons with Energies between 4 and 200 MeV

Photon-production data from neutron-induced reactions with oxygen are important over a wide range of neutron energies for many applied purposes. The quality of existing data is not sufficient for many applications as evident from the lack of agreement between various data sets, the rather large uncertainties quoted, and the dearth of angular-distribution data. Moreover, measurements of these reactions were rarely made above 15 MeV. To address these data needs, the high-energy pulsed neutron source at the Weapons Neutron Research Facility at the Los Alamos Neutron Science Center was used to measure photon-production data over a wide neutron-energy range. The gamma rays were detected with two high-resolution germanium detectors. Several measurements were made with these detectors at different locations to obtain data at seven angles. Excitation functions and angular-distribution data have been extracted for 24 gamma rays produced in neutron-induced reactions on oxygen. The data are presented and compared with previous measurements and with cross-section calculations. The data reported here are the basis for a new evaluation of neutron-induced reactions with oxygen; furthermore, the photon-production results have been validated through comparison with independent measurements of emitted-neutron spectra in inelastic 16O(n,n’) reactions at 14 MeV.

Improvements to the photon-production data for radiative capture in ENDF

High-quality photon-production data from thermal-neutron-capture reactions are important for many applications, including oil-well logging, planetary gamma-ray spectroscopy, and environmental techniques. Radiation transport codes usually access photon-production data from the national U.S. nuclear database, ENDF/B. To improve the photon-production data for thermal-neutron capture, we have compiled and evaluated the energies and yields of gamma rays for most naturally occurring isotopes with Z<31 and for a few heavier isotopes. The impact of improved photon-production cross sections for thermal-neutron capture in Cl is illustrated by comparing MCNP simulations and experimental measurements for a pulsed neutron oil-well logging instrument. The new compilation of photon-production data is being incorporated into the latest ENDF/B evaluations for each isotope and will be provided for future releases of the ENDF/B database.

Photon production in heavy-ion collisions and nuclear equation of state

Photon-production cross sections in 12C + 12C, 40Ca + 40Ca and 93Nb + 93Nb collisions at E lab = 84 and 200 Me V are calculated within the framework of the quantum molecula dynamics approach. The sensitivity of the photon-production cross section to the different types of nuclear equation of state and the momentum dependence in the in-medium NN interaction is studied in detail. Although we found some difference between the soft and hard equation of state in the calculated photon-production cross section, it is suppressed strongly by the momentum dependence in the interaction. There is a sizeable difference between the results calculated with or without taking into account the momentum dependence in the in-medium interaction. The time dependence of the production of the high-energy photons arising from incoherent pn collisions is also studied. The heavier the masses of colliding nuclei, the more number of energetic photons are produced after the system reaches the maximum density, at the expansion stage. Therefore, the photon-production data for heavy colliding nuclei might provide sc me information on the in-medium NN interaction during the time evolution of the heavy-ion reaction.

Hard-photon production in heavy-ion collisions and the nuclear structure function

The production of hard photons in heavy-ion collisions at intermediate energies is studied. The particles result from first-chance single proton-neutron collisions. The cross sections are expressed in terms of the product of the structure functions of the nuclei. At large momentum transfers the structure function is related to the momentum distribution of the nucléons. The parametrization obtained from high-energy proton scattering gives a good description of the photon production data. The mass dependence of the reaction phase space and its implications are examined. An energy conservation condition that describes correctly the mass of the system is used. The Pauli principle is discussed. The experimental data are in agreement with the assumption that photons are produced before the colliding nuclei overlap.

Japanese Evaluated Nuclear Data Library (JENDL).

Three versions of Japanese Evaluated Nuclear Data Library (JENDL) are briefly explained. The first version, JENDL-1, was made aiming mainly at application to fast reactors. The second version, JENDL-2, was built as a bigger general purpose evaluated nuclear data library. It stores nuclear data for 181 nuclides. It has, however, some drawbacks particularly for fusion neutronics calculation. To remove these drawbacks of JENDL-2 and further extend its applicability, the third version, JENDL-3, has now been made. JENDL-3 includes photon-production data for some nuclides, in addition to the data contained in JENDL-2.