Cross Sections For Production Of Protons Research Articles

Direct ρL meson production in proton–proton and proton–antiproton collisions

We have investigated the contribution of the Higher Twist (HT) Feynman diagrams to the large-[Formula: see text] inclusive [Formula: see text] meson production cross-section in proton–proton and proton–antiproton collisions and we discuss the phenomenological consequences of possible HT contributions to cross-sections. To extract HT subprocesses from Leading Twist (LT) background, we use various [Formula: see text] meson distribution amplitudes (DAs). In the numerical calculations, the dependencies of the HT contribution on the transverse momentum and the rapidity are discussed with special emphasis on DAs. Analysis of our results shows that HT contributions decrease more rapidly than LT contributions with increasing [Formula: see text]. The preceding results demonstrate that HT contributions must be considered especially in the region of low [Formula: see text] and the HT contribution to the cross-section depends on the choice of the meson DAs.

Measurement of electrons from semileptonic heavy-flavour hadron decays at midrapidity in pp and Pb–Pb collisions at [formula omitted] TeV

The differential invariant yield as a function of transverse momentum (pT) of electrons from semileptonic heavy-flavour hadron decays was measured at midrapidity in central (0–10%), semi-central (30–50%) and peripheral (60–80%) lead–lead (Pb–Pb) collisions at sNN=5.02 TeV in the pT intervals 0.5–26 GeV/c (0–10% and 30–50%) and 0.5–10 GeV/c (60–80%). The production cross section in proton–proton (pp) collisions at s=5.02 TeV was measured as well in 0.5<pT<10 GeV/c and it lies close to the upper band of perturbative QCD calculation uncertainties up to pT=5 GeV/c and close to the mean value for larger pT. The modification of the electron yield with respect to what is expected for an incoherent superposition of nucleon–nucleon collisions is evaluated by measuring the nuclear modification factor RAA. The measurement of the RAA in different centrality classes allows in-medium energy loss of charm and beauty quarks to be investigated. The RAA shows a suppression with respect to unity at intermediate pT, which increases while moving towards more central collisions. Moreover, the measured RAA is sensitive to the modification of the parton distribution functions (PDF) in nuclei, like nuclear shadowing, which causes a suppression of the heavy-quark production at low pT in heavy-ion collisions at LHC.

Measurement of 12C Fragmentation Cross Sections on C, O, and H in the Energy Range of Interest for Particle Therapy Applications

In a carbon ion treatment the nuclear fragmentation of both target and beam projectiles impacts on the dose released on the tumor and on the surrounding healthy tissues. Carbon ion fragmentation occurring inside the patient body has to be studied in order to take into account this contribution. These data are also important for the development of the range monitoring techniques with charged particles. The production of charged fragments generated by carbon ion beams of 115–353 MeV/u kinetic energy impinging on carbon, oxygen, and hydrogen targets has been measured at the CNAO particle therapy center (Pavia, Italy). The use of thin targets of graphite (C), PMMA (C2O5H8) and polyvinyl-toluene [plastic scintillator (PS), ${\text{C}}_{b}{\text{H}}_{a}$ ] allowed to measure fragments production cross sections, exploiting a time-of-flight (ToF) technique. PS detectors have been used to perform the ToF measurements, while LYSO crystals have been used for the deposited energy measurement and to perform particle identification. Cross sections have been measured at 90° and 60° with respect to the beam direction. The measured proton, deuteron, and triton differential production cross sections on C, O, and H, obtained exploiting the target subtraction strategy, are presented here as a function of the fragment kinetic energy.

Measurement of PET isotope production cross sections for protons and carbon ions on carbon and oxygen targets for applications in particle therapy range verification

Measured cross sections for the production of the PET isotopes , and from carbon and oxygen targets induced by protons (40–220 ) and carbon ions (65–430 ) are presented. These data were obtained via activation measurements of irradiated graphite and beryllium oxide targets using a set of three scintillators coupled by a coincidence logic. The measured cross sections are relevant for the PET particle range verification method where accurate predictions of the emitter distribution produced by therapeutic beams in the patient tissue are required. The presented dataset is useful for validation and optimization of the nuclear reaction models within Monte Carlo transport codes. For protons the agreement of a radiation transport calculation using the measured cross sections with a thick target PET measurement is demonstrated.

Cumulative Protons in Collisions between Carbon and Beryllium Nuclei at Energies of 0.60, 0.95, and 2.0 GeV/nucleon

Collisions between carbon and beryllium nuclei at initial kinetic energies of carbon nuclei of 0.6, 0.95, and 2.0 GeV/nucleon have been simulated within the Liege intranuclear cascade model. Invariant proton production cross sections at an angle of 3.5° have been determined. It has been shown that the dependence of experimental invariant proton production cross sections on the cumulative variable can be explained in terms of Fermi processes of motion of nucleons in a nucleus, multiple scattering, and production of delta resonances. Results of simulation have been compared to experimental data and results obtained within the quark cluster model.

Measurement of forward photon production cross-section in proton–proton collisions at [formula omitted] with the LHCf detector

In this paper, we report the production cross-section of forward photons in the pseudorapidity regions of η>10.94 and 8.99>η>8.81, measured by the LHCf experiment with proton–proton collisions at s=13TeV. The results from the analysis of 0.191nb−1 of data obtained in June 2015 are compared to the predictions of several hadronic interaction models that are used in air-shower simulations for ultra-high-energy cosmic rays. Although none of the models agree perfectly with the data, EPOS-LHC shows the best agreement with the experimental data among the models.

Electronic wave function and binding effects in M-shell ionization of gold by protons

Abstract The measured M-X-ray production cross sections for protons, which are used in the particle induced X-ray emission (PIXE) technique, are systematically underestimated for low impact energies by the ECPSSR and ECUSAR theories. These theories, which are based on the plane wave Born approximation (PWBA) and use the screened hydrogenic wave functions, include corrections for the projectile Coulomb deflection and electron relativistic and binding effects. In the present paper, in order to interpret the observed disagreement at low impact energies, the systematic calculations of the M-shell ionization cross sections for gold were performed using the semiclassical (SCA) and the binary encounter (BEA) approximations in order to identify a role of the electronic wave function and electron binding effects. In these calculations the different wave functions, from nonrelativistic hydrogenic to selfconsistent Dirac-Hartree-Fock, were considered and the binding effect was treated within extreme separated- (SA) and united-atoms (UA) limits. The results are discussed in details and the observed discrepancies are attributed to inadequate description of the electron binding effect at the lowest impact energies for which the molecular approach is required.

Measurements of the mathrm{t}overline{mathrm{t}} production cross section in lepton+jets final states in pp collisions at 8 ,text {TeV} and ratio of 8 to 7\xa0,text {TeV} cross sections

A measurement of the top quark pair production (mathrm{t}overline{mathrm{t}} ) cross section in proton–proton collisions at the centre-of-mass energy of 8,text {TeV} is presented using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.6,text {fb}^{-text {1}}. This analysis is performed in the mathrm{t}overline{mathrm{t}} decay channels with one isolated, high transverse momentum electron or muon and at least four jets, at least one of which is required to be identified as originating from hadronization of a b quark. The calibration of the jet energy scale and the efficiency of b jet identification are determined from data. The measured mathrm{t}overline{mathrm{t}} cross section is 228.5 pm 3.8,text {(stat)} pm 13.7,text {(syst)} pm 6.0,text {(lumi)} text { pb} . This measurement is compared with an analysis of 7,text {TeV} data, corresponding to an integrated luminosity of 5.0,text {fb}^{-text {1}}, to determine the ratio of 8,text {TeV} to 7,text {TeV} cross sections, which is found to be 1.43 pm 0.04,text {(stat)} pm 0.07,text {(syst)} pm 0.05,text {(lumi)} . The measurements are in agreement with QCD predictions up to next-to-next-to-leading order.

Validation of Geant4 Physics Models Relevant for Space Radiation

In order to use GEANT4 toolkit in the energies relevant to the space radiation it has been tested few of electromagnetic and hadronic models of it by comparing simulated values with NIST data and other experimental data available. For the validation of electromagnetic models energy-loss and electronic stopping powers are considered whereas for the validation of hadronic models, isotope production cross-sections and total fragmentation cross-sections are considered. The stopping power values simulated for protons in Al are agreeing very well with NIST database values. The energy-loss and residual energy values simulated for alpha particles in Si and Al respectively are in good agreement with experimental values at high energies and low-thicknesses of target materials. The stopping power values of alpha particles and Fe ions in Al are also agreeing well with tabulated values at the small thickness of target materials. The proton - proton production cross-section values for liquid hydrogen and polyethylene are within the limits of experimental errors. Although total fragmentation cross-sections for Fe ions in polyethylene and aluminum are not agreeing with the experimental values at low energies, they are agreeing at the peak of GCR spectrum which is around 1 GeV/nucleon. So the selected physics models used in the present simulation work can be used for the space radiation protection studies.

Light-ion Production in 175 MeV Neutron-induced Reactions on Oxygen

We have measured double-differential cross sections for 175 MeV quasi-monoenergetic neutrons on oxygen. The detector setup used in MEDLEY consists of eight Si-Si-CsI telescopes designed to detect light ions (up to A=4), with a low-energy threshold and over an angular domain ranging from 20∘ to 160∘, in steps of 20∘. The ΔE−E technique is used to identify the light ions. Suppression of events induced by neutrons in the low-energy tail of the neutron field is achieved by time-of-flight techniques. The data are normalised relative to elastic np scattering measured in one of the telescopes at 20∘. We present preliminary double-differential production cross sections for protons, deuterons and α particles and compare them with theoretical reaction model calculations.

Close-coupling approach to antiproton-impact breakup of molecular hydrogen

An ab initio time-dependent convergent close-coupling approach to describing antiproton collisions with molecular hydrogen or the hydrogen molecular ion has been developed. The approach accounts for all possible orientations of the molecular target. Averaging over the molecular orientations is performed fully analytically. For the molecular hydrogen target calculated orientation-averaged total cross sections for single ionization and proton production are compared with several experiments over the energy range of 1–2000 keV. Results for single ionization are in good agreement with experiment, except for the region around the experimental maximum. For proton production reasonable agreement with experiment is observed above 40 keV.

Measurement of the sum of WW and WZ production with W+dijet events in pp collisions at [Formula: see text

A measurement of the inclusive WW+WZ diboson production cross section in proton–proton collisions is reported, based on events containing a leptonically decaying W boson and exactly two jets. The data sample, collected at sqrt{s} = 7~mbox{TeV} with the CMS detector at the LHC, corresponds to an integrated luminosity of 5.0 fb−1. The measured value of the sum of the inclusive WW and WZ cross sections is σ(pp→WW+WZ)=68.9±8.7 (stat.)±9.7 (syst.)±1.5 (lum.) pb, consistent with the standard model prediction of 65.6±2.2 pb. This is the first measurement of WW+WZ production in pp collisions using this signature. No evidence for anomalous triple gauge couplings is found and upper limits are set on their magnitudes.

W ± Z production in pp collisions at 7 TeV with ATLAS

The measurement of the W ± Z production cross-section in proton–proton interactions at $\sqrt{s}=7$ TeV is reported from the ATLAS experiment at the Large Hadron Collider using 1.02 fb − 1 of data. The measurement is derived from events with leptonically decaying bosons with electrons, muons, and missing energy in the final state. Limits on anomalous triple gauge boson couplings are derived.

Experimental evaluation of the nuclide production cross sections for 50-GeV protons in copper

A thin target composed of copper and aluminum foils was placed in the accelerator vacuum tube and irradiated with circulating 50-GeV protons. The number of protons that hit the target during the accelerator run was determined by the activation of the monitor aluminum foil, and the radionuclide activities in each foil were measured. A set of the radionuclide production cross sections in 50-GeV proton interactions with copper nuclei were evaluated.

Meson wave functions from holographic QCD and the role of infrared renormalons in proton–proton collisions

We calculate the contribution of the higher-twist Feynman diagrams to the large-pT inclusive pion production cross section in proton–proton collisions in the cases of the running and frozen coupling approaches within holographic QCD. The structure of the infrared renormalon singularities of the higher-twist subprocess cross section and its resummed expression are found. We compare the resummed higher-twist cross sections with the ones obtained in the framework of the frozen coupling approximation and the leading-twist cross section. We discuss the phenomenological consequences of possible higher-twist contributions to the pion production in proton–proton collisions within holographic QCD.

MESON PRODUCTION IN PROTON–PROTON COLLISIONS IN THE NAIVE NONABELIANIZATION APPROXIMATION AND THE ROLE OF INFRARED RENORMALONS

We calculate the "naive nonabelianization" (NNA) contributions of the higher-twist Feynman diagrams to the large-pT inclusive pion production cross-section in proton–proton collisions in the case of the running coupling and frozen coupling approaches. We compare the resummed "naive nonabelianization" higher-twist cross-sections with the ones obtained in the framework of the frozen coupling approach and leading-twist cross-section. The structure of infrared renormalon singularities of the higher-twist subprocess cross-section and it's resummed expression are found. We discuss the phenomenological consequences of possible higher-twist contributions to the pion production in proton–proton collisions in within NNA.

Quarkonium production measurements with the ALICE detector at the LHC

In this new energy regime, quarkonium provides a unique probe to study the properties of the high-density, strongly interacting system formed in the early stages of high-energy heavy-ion collisions. In ALICE, quarkonium states are reconstructed down to pT = 0 via their µ+µ− decay channel in the muon spectrometer (2.5 ⩽ y ⩽ 4.0) and via their e+e− channel in the central barrel (|y| ⩽ 0.9). Measurement of the transverse momentum and rapidity distributions of the inclusive J/ψ production cross section in proton–proton collisions at = 2.76 and 7 TeV will be presented. We will discuss the dependence on charged particle multiplicity of the inclusive J/ψ yield in proton–proton collisions at = 7 TeV. Finally, the analysis of the inclusive J/ψ production in Pb–Pb collisions at = 2.76 TeV will be described. Preliminary results on the nuclear modification factor (RAA) and the central to peripheral nuclear modification factor (RCP) will be discussed.

Response functions for computing absorbed dose to skeletal tissues from neutron irradiation

Spongiosa in the adult human skeleton consists of three tissues—active marrow (AM), inactive marrow (IM) and trabecularized mineral bone (TB). AM is considered to be the target tissue for assessment of both long-term leukemia risk and acute marrow toxicity following radiation exposure. The total shallow marrow (TM50), defined as all tissues lying within the first 50 µm of the bone surfaces, is considered to be the radiation target tissue of relevance for radiogenic bone cancer induction. For irradiation by sources external to the body, kerma to homogeneous spongiosa has been used as a surrogate for absorbed dose to both of these tissues, as direct dose calculations are not possible using computational phantoms with homogenized spongiosa. Recent micro-CT imaging of a 40 year old male cadaver has allowed for the accurate modeling of the fine microscopic structure of spongiosa in many regions of the adult skeleton (Hough et al 2011 Phys. Med. Biol. 56 2309–46). This microstructure, along with associated masses and tissue compositions, was used to compute specific absorbed fraction (SAF) values for protons originating in axial and appendicular bone sites (Jokisch et al 2011 Phys. Med. Biol. 56 6857–72). These proton SAFs, bone masses, tissue compositions and proton production cross sections, were subsequently used to construct neutron dose-response functions (DRFs) for both AM and TM50 targets in each bone of the reference adult male. Kerma conditions were assumed for other resultant charged particles. For comparison, AM, TM50 and spongiosa kerma coefficients were also calculated. At low incident neutron energies, AM kerma coefficients for neutrons correlate well with values of the AM DRF, while total marrow (TM) kerma coefficients correlate well with values of the TM50 DRF. At high incident neutron energies, all kerma coefficients and DRFs tend to converge as charged-particle equilibrium is established across the bone site. In the range of 10 eV to 100 MeV, substantial differences are observed among the kerma coefficients and DRF. As a result, it is recommended that the AM kerma coefficient be used to estimate the AM DRF, and that the TM kerma coefficient be used to estimate the TM50 DRF below 10 eV. Between 10 eV and 100 MeV, the appropriate DRF should be used as presented in this study. Above 100 MeV, spongiosa kerma coefficients apply well for estimating skeletal tissue doses. DRF values for each bone site as a function of energy are provided in an electronic annex to this article available at http://stacks.iop.org/0031-9155/56/6873/mmedia.

A possible determination of the quark radiation length in cold nuclear matter

We calculate the differential Drell–Yan production cross section in proton–nucleus collisions by including both next-to-leading order perturbative effects and effects of the nuclear medium. We demonstrate that dilepton production in fixed target experiments is an excellent tool to study initial-state parton energy loss in large nuclei and to accurately determine the stopping power of cold nuclear matter. We provide theoretical predictions for the attenuation of the Drell–Yan cross section at large values of Feynman xF and show that for low proton beam energies experimental measurements at Fermilabʼs E906 can clearly distinguish between nuclear shadowing and energy loss effects. If confirmed by data, our results may help determine the quark radiation length in cold nuclear matter X0∼10−13 m.

Light-Ion Production in The Interaction of 175 MeV Neutrons with Iron and Bismuth

We have measured double-differential (angle and energy) cross sections for light-ion (p, d, t, (3)He, and a) production in the interaction of quasi-monoenergetic 175 MeV neutrons with iron and bismuth. Measurements have been performed at the The Svedberg Laboratory, Uppsala (Sweden), using the Medley setup which allows low-energy thresholds and wide energy and angular ranges. Medley is a spectrometer system consisting of eight three-element telescopes placed at angles from 20 degrees to 160 degrees, in steps of 20 degrees. Each telescope is composed of two silicon surface barrier detectors and a CsI(Tl) scintillator, to perform particle identification, fully stop the produced light-ions and measure their kinetic energy. The time-of-flight was used to reduce the contribution from the low energy tail in the accepted incident neutron spectrum. We report double-differential production cross sections for protons, deuterons, tritons, (3)He and alpha particles and compare them with model calculations with TALYS-1.2.