Primary Proton Research Articles

Tracking and separation of relativistic ions using Timepix3 with a 300 μm thick silicon sensor

The response of a Timepix3 detector (256 × 256 pixels, pixel pitch 55 μm) with a 300 μm thick silicon sensor was studied in relativistic charged particle beams at the Super-Proton-Synchrotron at CERN . The detector was irradiated at different angles in a 400 GeV/c primary proton beam and in a mixed beam created by a 330 GeV/c Pb beam hitting a beryllium target. We present and discuss energy deposition spectra and particle track features for relativistic particles of different stopping power. The proton data shows that a relative energy resolution of approximately 9 % can be achieved. Analysis of deposited energy spectra and tracks in the detector produced by heavier ions are carried out with the aim to investigate the capabilities of the Timepix3 detector for decomposing the mixed beam. Using spectrum stripping technique by iterative Landau curve fitting charge discrimination could be done up to Z = 7 for impact angle of 60 degrees (with respect to the sensor normal). For smaller impact angles the particle charge separation is decreased due to the saturation of the pixel electronics (∼600 keV) . Previous works describing the 3D track reconstruction for minimally ionizing particles (Z = 1) were extended in the present work by adding the methodology of heavier ions track reconstruction in 3D.

Exploring dense baryonic matter and multi-strangeness at J-PARC

J-PARC is one of the world's highest-intensity proton synchrotron facilities for material and life sciences, neutrino physics, hadron and nuclear physics. By acceleration of heavy-ion beams, J-PARC could also become a high-intensity frontier heavy-ion beam facility (J-PARC-HI). For heavy-ion acceleration, we will build a heavy-ion linac and a booster ring as a compact heavy-ion injector, while we utilize the existing RCS and MR synchrotrons to accelerate 1011 Hz heavy-ion beams at 1–12 AGeV/c. We aim at exploring phase structures of the QCD phase diagram in a high baryon-density regime such as the first-order phase boundary and the QCD critical point, and also aim to search for multi-strangeness systems. We are developing the experimental design for a large acceptance spectrometer. In this work, physics feasibility of J-PARC-HI such as flow and hypernucleus measurements will be shown. Also, a plan to transport heavy-ion beams in the primary proton beamline at Hadron Experimental Facility and an upgrade plan to study heavy-ion collisions at the p+A experiment J-PARC E16 will be presented.

EPEN-25. EXCEPTIONAL CLINICAL AND IMAGING RESPONSE TO TRK-INHIBITION IN A PATIENT WITH SUPRATENTORIAL EPENDYMOMA HARBORING NTRK2 GENE FUSION

BACKGROUNDPatients with metastatic pediatric ependymoma have limited therapeutic options and poor outcomes. Approximately ¾ of supratentorial ependymomas are driven by C11ORF95-RELA fusions, and the remaining by a heterogeneous group of fusion events. We present a six year-old male diagnosed with supratentorial ependymoma with leptomeningeal carcinomatosis harboring an NTRK2-fusion. Local and distant multifocal, intracranial and intraspinal tumor recurrence occurred seven months following gross total resection of the primary lesion and proton beam craniospinal irradiation.METHODSDNA and RNA from FFPE tumor were used for targeted sequencing using an 81-gene fusion panel and 124-gene mutation panel. Separately, capture transcriptome sequencing, exome sequencing, and copy number array were performed as part of the Texas KidsCanSeq study, an NHGRI/NCI-funded Clinical Sequencing Evidence-Generating Research (CSER) consortium project. All sequencing was carried out in CLIA-certified laboratories.RESULTSAn in-frame fusion between 5’ exons 1–3 of KANK1 and 3’ exons 16–21 of NTRK2, predicted to retain the kinase domain, was identified. At tumor recurrence, therapy was initiated with Larotrectinib, an FDA-approved pan-TRK inhibitor. Clinical improvement in cognitive speed, motor strength, and coordination was observed at two weeks with significant tumor response on MRI at two and four months.CONCLUSIONTRK gene fusions have not previously been reported in ependymoma. Further tumor characterization by methylation profiling is underway and will be of diagnostic interest given the apparent discordance between tumor histology and molecular findings. This case highlights the potential impact of clinical genomic analysis for children with CNS tumors.

FLUKA simulation of target fragmentation in proton therapy.

In proton therapy, secondary fragments are created in nuclear interactions of the beam with the target nuclei. The secondary fragments have low kinetic energies and high atomic numbers as compared to primary protons. Fragments have a high LET and deposit all their energy close to the generation point. For their characteristics, secondary fragments can alter the dose distribution and lead to an increase of RBE for the same delivered physical dose. Moreover, the radiobiological impact of target fragmentation is significant mostly in the region before the Bragg peak, where generally healthy tissues are present, and immediately after Bragg peak. Considering the high biological impact of those particles, especially in the case of healthy tissues or organs at risk, the inclusion of target fragmentation processes in the dose calculation of a treatment planning system can be relevant to improve the treatment accuracy and for this reason it is one of the major tasks of the MoVe IT project. In this study, Monte Carlo simulations were employed to fully characterize the mixed radiation field generated by target fragmentation in proton therapy. The dose averaged LET has been evaluated in case of a Spread Out Bragg Peak (SOBP). Starting from LET distribution, RBE has been evaluated with two different phenomenological models. In order to characterize the mixed radiation field, the production cross section has been evaluated by means of the FLUKA code. The future development of present work is to generate a MC database of fragments fluence to be included in TPS.

Spectral Signatures of PeVatrons

Abstract We analyze the energy distributions of final (stable) products—gamma rays, neutrinos, and electrons—produced in inelastic proton–proton collisions in the PeV energy regime. We also calculate the energy spectrum of synchrotron radiation from secondary electrons, assuming that these are promptly cooled in the surrounding magnetic field. We show that the synchrotron radiation has an energy distribution much shallower than that of primary protons, hence we suggest taking advantage of such a feature in the spectral analysis of the highest-energy (cutoff) emission region from particle accelerators. For a broad range of energy distributions in the parent protons, we propose simple analytical presentations for the spectra of secondaries in the cutoff region. These results can be used in the interpretation of high-energy radiation from PeVatrons—cosmic-ray factories accelerating protons to energies up to 1 PeV.

Cancellation of Leading Contributions to Radiative Corrections to the Cross Section for Elastic Electron–Proton Scattering in Experiments Devoted to Measuring the Proton Charge Radius

A cancellation of leading contributions to radiative corrections to the cross section for elastic electron–proton scattering for experiments devoted to measuring the proton charge radius is studied. The cancellations occur in the contribution of electron interaction with the electromagnetic field. It is shown that, under experimental conditions where the recoil proton is detected, there occurs cancellation in the one-loop approximation not only for the terms containing large logarithms but also for the constants at these logarithms and that a nonzero electron contribution to radiative corrections appears starting from terms that are proportional to $$Q/E$$ , where $$Q$$ is the momentum transfer and $$E$$ is the electron energy in the rest frame of the primary proton.

Technical note: Generation of a Cerenkov scatter function convolution kernel for a primary proton beam.

PurposeTo generate a Cerenkov scatter function (CSF) for a primary proton beam and to study the dependence of the CSF on the irradiated medium.Materials and MethodsThe MCNP 6.2 code was used to generate the CSF. The CSF was calculated for light‐pigmented, medium‐pigmented, and dark‐pigmented stratified skin, as well as for a homogeneous optical phantom, which mimics the optical properties of human tissue. CSFs were generated by binning all of the Cerenkov photons which escape the back end (end opposite beam incidence) of a 20 × 20 × 20 cm phantom. A 4 × 4 cm, 500 × 500 bin grid was used to create a histogram of the Cerenkov photon flux on the simulated medium’s back surface (surface opposite beam incidence). A triple Gaussian was then used to fit the data.ResultsFrom the triple Gaussian fit, the coefficients of the CSF for the four phantom materials was generated. The individual CSF fit coefficient errors, with respect to the Gaussian representation, were found to be between 0.92% and 4.11%. The R2 value for the fit was calculated to be 0.99. The phantom material was found to have a significant effect (63% difference between materials) on the CSF amplitude and full width at half maximum (195% difference between materials). The difference in these parameters for the three skin pigments was found to be small.ConclusionsThe CSF was obtained for a proton beam using the MCNP 6.2 code for a phantom constructed of light, medium, and dark stratified human skin, as well as for an optical phantom. The CSFs were then fit with a triple‐Gaussian function. The coefficients can be used to generate a radially symmetric CSF, which can then be used to deconvolve a measured Cerenkov image to obtain the dose distribution.

Comparison of Prospective, Longitudinal Swallowing Function after Primary Intensity-Modulated Proton Therapy (IMPT) or Transoral Robotic Surgery (TORS) for Oropharyngeal Squamous Cell Carcinoma

Comparison of Prospective, Longitudinal Swallowing Function after Primary Intensity-Modulated Proton Therapy (IMPT) or Transoral Robotic Surgery (TORS) for Oropharyngeal Squamous Cell Carcinoma

His57 controls the efficiency of ESR, a light-driven proton pump from Exiguobacterium sibiricum at low and high pH

ESR, a light-driven proton pump from Exiguobacterium sibiricum, contains a lysine residue (Lys96) in the proton donor site. Substitution of Lys96 with a nonionizable residue greatly slows reprotonation of the retinal Schiff base. The recent study of electrogenicity of the K96A mutant revealed that overall efficiency of proton transport is decreased in the mutant due to back reactions (Siletsky et al., BBA, 2019). Similar to members of the proteorhodopsin and xanthorhodopsin families, in ESR the primary proton acceptor from the Schiff base, Asp85, closely interacts with His57. To examine the role of His57 in the efficiency of proton translocation by ESR, we studied the effects of H57N and H57N/K96A mutations on the pH dependence of light-induced pH changes in suspensions of Escherichia coli cells, kinetics of absorption changes and electrogenic proton transfer reactions during the photocycle. We found that at low pH (<5) the proton pumping efficiency of the H57N mutant in E. coli cells and its electrogenic efficiency in proteoliposomes is substantially higher than in the WT, suggesting that interaction of His57 with Asp85 sets the low pH limit for H+ pumping in ESR. The electrogenic components that correspond to proton uptake were strongly accelerated at low pH in the mutant indicating that Lys96 functions as a very efficient proton donor at low pH. In the H57N/K96A mutant, a higher H+ pumping efficiency compared with K96A was observed especially at high pH, apparently from eliminating back reactions between Asp85 and the Schiff base by the H57N mutation.

Measurement of the Low-Energy Antideuteron Inelastic Cross Section.

In this Letter, we report the first measurement of the inelastic cross section for antideuteron-nucleus interactions at low particle momenta, covering a range of 0.3≤p<4 GeV/c. The measurement is carried out using p-Pb collisions at a center-of-mass energy per nucleon-nucleon pair of sqrt[s_{NN}]=5.02 TeV, recorded with the ALICE detector at the CERN LHC and utilizing the detector material as an absorber for antideuterons and antiprotons. The extracted raw primary antiparticle-to-particle ratios are compared to the results from detailed ALICE simulations based on the geant4 toolkit for the propagation of (anti)particles through the detector material. The analysis of the raw primary (anti)proton spectra serves as a benchmark for this study, since their hadronic interaction cross sections are well constrained experimentally. The first measurement of the inelastic cross section for antideuteron-nucleus interactions averaged over the ALICE detector material with atomic mass numbers ⟨A⟩=17.4 and 31.8 is obtained. The measured inelastic cross section points to a possible excess with respect to the Glauber model parametrization used in geant4 in the lowest momentum interval of 0.3≤p<0.47 GeV/c up to a factor 2.1. This result is relevant for the understanding of antimatter propagation and the contributions to antinuclei production from cosmic ray interactions within the interstellar medium. In addition, the momentum range covered by this measurement is of particular importance to evaluate signal predictions for indirect dark-matter searches.

Asparagine and Glutamine Side-Chains and Ladders in HET-s(218-289) Amyloid Fibrils Studied by Fast Magic-Angle Spinning NMR.

Asparagine and glutamine side-chains can form hydrogen-bonded ladders which contribute significantly to the stability of amyloid fibrils. We show, using the example of HET-s(218–289) fibrils, that the primary amide side-chain proton resonances can be detected in cross-polarization based solid-state NMR spectra at fast magic-angle spinning (MAS). J-coupling based experiments offer the possibility to distinguish them from backbone amide groups if the spin-echo lifetimes are long enough, which turned out to be the case for the glutamine side-chains, but not for the asparagine side-chains forming asparagine ladders. We explore the sensitivity of NMR observables to asparagine ladder formation. One of the two possible asparagine ladders in HET-s(218–289), the one comprising N226 and N262, is assigned by proton-detected 3D experiments at fast MAS and significant de-shielding of one of the NH2 proton resonances indicative of hydrogen-bond formation is observed. Small rotating-frame 15N relaxation-rate constants point to rigidified asparagine side-chains in this ladder. The proton resonances are homogeneously broadened which could indicate chemical exchange, but is presently not fully understood. The second asparagine ladder (N243 and N279) in contrast remains more flexible.

Energy sensitivity of the GRAPES-3 EAS array for primary cosmic ray protons

Low energy ground-based cosmic ray air shower experiments generally have energy threshold in the range of a few tens to a few hundreds of TeV. The shower observables are measured indirectly with an array of detectors. The atmospheric absorption of low energy secondaries limits their detection frequencies at the Earth's surface. However, due to selection effects, a tiny fraction of low energy showers, which are produced in the lower atmosphere can reach the observational level. But, due to less information of shower observables, the reconstruction of these showers are arduous. Hence, it is believed that direct measurements by experiments aboard on satellites and balloon flights are more reliable at low energies. Despite having very small efficiency ($\sim$0.1%) at low energies, the large acceptance ($\sim$5 m$^2$sr) of GRAPES-3 experiment allows observing primary cosmic rays down below to $\sim$1 TeV and opens up the possibility to measure primary energy spectrum spanning from a few TeV to beyond cosmic ray knee (up to 10$^{16}$ eV), covering five orders of magnitude. The GRAPES-3 energy threshold for primary protons through Monte Carlo simulations are calculated, which gives reasonably good agreement with data. Furthermore, the total efficiencies and acceptance are also calculated for protons primaries. The ability of GRAPES-3 experiment to cover such a broader energy range may provide a unique handle to bridge the energy spectrum between direct measurements at low energies and indirect measurements at ultra-high energies.

Hydroxide Ion Carrier for Proton Pumps in Bacteriorhodopsin: Primary Proton Transfer.

Bacteriorhodopsin (BR) is a model protein for light-driven proton pumps, where the vectorial active proton transport results in light-energy conversion. To clarify the microscopic mechanism of primary proton transfer from retinal Schiff base (SB) to Asp85 in BR, herein, we performed quantum-mechanical metadynamics simulations with the isolated BR model (∼3750 atoms). The simulations showed a novel proton transfer mechanism, viz. the hydroxide ion mechanism, in which the deprotonation of specific internal water (Wat452) yields the protonation of Asp85 via Thr89, after which the resulting hydroxide ion accepts the remaining proton from retinal SB. Systematic investigations adopting four sequential snapshots obtained by the time-resolved serial femtosecond crystallography revealed that proton transfer took 2-5.25 μs on the photocycle. The presence of Wat401, which is the main difference between snapshots at 2 and 5.25 μs, is found to be essential in assisting the primary proton transfer. Furthermore, the hydroxide ion mechanism was confirmed by the minimum energy path for the primary proton transfer in BR obtained by the nudged elastic band calculations with the embedded BR model (10,119 atoms), in which BR was embedded within lipid membranes in between water solvents.

Searching for long-lived particles beyond the Standard Model at the Large Hadron Collider

Particles beyond the Standard Model (SM) can generically have lifetimes that are long compared to SM particles at the weak scale. When produced at experiments such as the Large Hadron Collider (LHC) at CERN, these long-lived particles (LLPs) can decay far from the interaction vertex of the primary proton–proton collision. Such LLP signatures are distinct from those of promptly decaying particles that are targeted by the majority of searches for new physics at the LHC, often requiring customized techniques to identify, for example, significantly displaced decay vertices, tracks with atypical properties, and short track segments. Given their non-standard nature, a comprehensive overview of LLP signatures at the LHC is beneficial to ensure that possible avenues of the discovery of new physics are not overlooked. Here we report on the joint work of a community of theorists and experimentalists with the ATLAS, CMS, and LHCb experiments—as well as those working on dedicated experiments such as MoEDAL, milliQan, MATHUSLA, CODEX-b, and FASER—to survey the current state of LLP searches at the LHC, and to chart a path for the development of LLP searches into the future, both in the upcoming Run 3 and at the high-luminosity LHC. The work is organized around the current and future potential capabilities of LHC experiments to generally discover new LLPs, and takes a signature-based approach to surveying classes of models that give rise to LLPs rather than emphasizing any particular theory motivation. We develop a set of simplified models; assess the coverage of current searches; document known, often unexpected backgrounds; explore the capabilities of proposed detector upgrades; provide recommendations for the presentation of search results; and look towards the newest frontiers, namely high-multiplicity ‘dark showers’, highlighting opportunities for expanding the LHC reach for these signals.

Studying the thinning Effect of Longitudinal development in Extensive Air Showers for Primary Proton and Iron Nuclei at Ultra-High Energies

In the present work, extensive air showers (EAS) effects are described by estimating the longitudinal development model of EAS at very high energies of various cosmic ray particles. The longitudinal development was simulated for charged particles such as gamma, charged pions and charged muons at very high energies 1017, 1018 and 1019eV. The simulation was performed using an air shower simulator system (AIRES) version 19.04.0. The effect of primary particles, energies, thinning energy and zenith angle (θ) on the number of charged particles (longitudinal development) produced in the EAS was taken into account. The rapprochement of the estimated longitudinal development of the charged particles such as the charged muons and charged pions with the experimental measurements (AUGER experiment) that gave a good agreement for primary proton at the fixed primary energy 1019eV for θ =0˚.

Radiation damage from energetic particles at GRad-level of SiO[formula omitted] fibers of the Large Hadron Collider ATLAS Zero-Degree Calorimeter (ZDC)

Core SiO2 quartz fibers of the Large Hadron Collider (LHC) ATLAS Zero-degree Calorimeter (ZDC) are expected to experience integrated doses of a few giga-Rad (Grad) at their closest position to the LHC beam. An array of fibers was irradiated with 200 MeV protons and spallation-generated mixed spectra (primarily fast neutrons) at the Brookhaven National Laboratory (BNL) Linac. Specifically, 1 mm- and 2 mm-diameter quartz (GE 124) rods of 50 mm length were exposed to direct 200 MeV protons leading to peak integrated dose of ∼28 Grad (∼0.28 GGy). Exposure of 1 mm-diameter SiO2 fibers to a neutron flux was also achieved in the spallation field generated by 128 MeV protons. In the post-irradiation analysis, the quartz fiber transmittance was evaluated as a function of the absorbed dose. Significant degradation of the transmittance and increased radiation damage of the material were observed. Microscopic evaluation of the fibers revealed extensive micro-structural damage and irradiation-induced defects. The measurements revealed that a threshold fluence (∼2.6 1016 p/cm2) or dose of ∼10 Grad (0.1 GGy) appears to exist beyond which light transmittance drops below 10%. Also observed is that fiber transmittance loss increased drastically with SiO2 fiber diameter (1 mm vs. 2 mm diameter). This is attributed, in part, to the earlier lateral leakage from the 1 mm fiber of knock-on electrons and primary protons implying that more damage-inducing protons travel within the bulk of the 50 mm long 2-mm fibers. While Monte Carlo simulations performed tend to support such assumption, future experiments and sensitivity studies are envisioned to address the fiber diameter influence on degradation.

Conformational Motions and Water Networks at the α/β Interface in E. coli Ribonucleotide Reductase.

Ribonucleotide reductases (RNRs) catalyze the conversion of all four ribonucleotides to deoxyribonucleotides and are essential for DNA synthesis in all organisms. The active form of E. coli Ia RNR is composed of two homodimers that form the active α2β2 complex. Catalysis is initiated by long-range radical translocation over a ∼32 Å proton-coupled electron transfer (PCET) pathway involving Y356β and Y731α at the interface. Resolving the PCET pathway at the α/β interface has been a long-standing challenge due to the lack of structural data. Herein, molecular dynamics simulations based on a recently solved cryogenic-electron microscopy structure of an active α2β2 complex are performed to examine the structure and fluctuations of interfacial water, as well as the hydrogen-bonding interactions and conformational motions of interfacial residues along the PCET pathway. Our free energy simulations reveal that Y731 is able to sample both a flipped-out conformation, where it points toward the interface to facilitate interfacial PCET with Y356, and a stacked conformation with Y730 to enable collinear PCET with this residue. Y356 and Y731 exhibit hydrogen-bonding interactions with interfacial water molecules and, in some conformations, share a bridging water molecule, suggesting that the primary proton acceptor for PCET from Y356 and from Y731 is interfacial water. The conformational flexibility of Y731 and the hydrogen-bonding interactions of both Y731 and Y356 with interfacial water and hydrogen-bonded water chains appear critical for effective radical translocation along the PCET pathway. These simulations are consistent with biochemical and spectroscopic data and provide previously unattainable atomic-level insights into the fundamental mechanism of RNR.

Neutron-Physical Calculation of Targets for a Subcritical Assembly Controlled by a Proton Accelerator

A neutron-physical calculation is performed for neutron-producing lead, tungsten, and natural uranium targets for a subcritical assembly controlled by a proton accelerator at 0.6, 1, and 2.5 GeV. At these high proton energies, the interaction of protons with target atoms is accompanied by a splitting reaction. In terms of the neutron yield per primary proton, this reaction is more advantageous than the fission reaction. The calculation results are used to estimate the neutron-flux densities in a subcritical multiplying assembly.

Low-Energy Protons—Where and Why “Rare Events” Matter

Failures (or upsets) of complementary metal-oxide-semiconductor (CMOS) devices, due to direct ionization from protons, were first predicted in 1982 and subsequently realized in 2007 for low-energy (1 MeV) protons (LEPs). For terrestrial applications, secondary LEPs, generated during collision events, may cause upsets, especially in cells far away from the initial strike location than their heavier spallation-fragment cousins. However, direct ionization may be more important in space and high-altitude environments due to the large flux of primary high-energy protons impinging on nearby spacecraft (and local device) shielding. In this article, a brief review of the relevant literature will be followed by a discussion of the sensitivity to direct ionization of typical CMOS devices. It will be shown that a significant number of LEPs are generated by cosmic radiation spallation events, suggesting that track structures and exact device hit locations need to be understood and effectively modeled, especially for modern devices. Also, the rate of multiple cell upsets, and hence multiple bit upsets, in these environments will be explored, with possible mitigation techniques discussed. The published work on muons and delta electrons, in addition to LEPs, will be reviewed as potential single-event upset (SEU) sources with the future scaling of CMOS devices.

On the relative importance of hadronic emission processes along the jet axis of active galactic nuclei

ABSTRACTWith the coincident detection of a gamma-ray flare and a neutrino from the blazar TXS 0506+056, active galactic nuclei (AGNs) have been put into focus as possible sources of the diffuse neutrino flux. We present a space and time-resolved model of the high-energy particle emission of a plasmoid assumed to travel along the axis of an AGN jet at relativistic speed. This was achieved by modifying the publicly available crpropa (version 3.1+) propagation framework that in our work is capable of being applied to source physics on sub-kpc scales. The propagation of a population of primary protons is modelled in a purely turbulent magnetic field and we take into account interactions of these protons with photons scattered from the accretion disc, synchrotron radiation emitted by ambient relativistic electrons, as well with themselves and with other ambient matter. Our model produces a PeV-neutrino flare caused mainly by photohadronic interactions of primaries with the accretion disc field. Secondary high-energy gamma-rays partly attenuate with the ambient photon fields whose combined optical depths achieve their minimal opacity for photons of around 10 TeV. Thus, our model is well capable of producing neutrino flares with a significantly reduced emission of gamma-rays in jets with a hadronic jet component that in the future can be fit to specific AGN flare scenarios.