The aim of the BOLD-PET project is to develop a fast-response, high-efficiency gamma detector with fine grained spatial resolution for positron emission tomography (PET) based on recent developments using the liquid TriMethyl Bismuth (TMBi). This liquid with a bismuth mass fraction of more than 80% allows for a very efficient and accurate detection of 511 keV photons originated from positron annihilation. Bismuth has the highest nuclear charge (Z = 83) and thus the largest photoelectric cross section of all stable isotopes. The gamma energy of 511 keV is transferred to electrons in this material in nearly 50 % of the cases through the photoelectric effect. Both the Cherenkov light emitted by the resulting relativistic photo-electron and the secondary charge carriers produced during multiple scattering interactions are detected in a liquid ionisation chamber, supplemented by photodetectors. Based on previous studies of liquid TMBi, we intend to develop and evaluate a novel PET detector with simultaneous detection of Cherenkov light and ionisation in a common effort of four research partners. Excellent imaging resolution is anticipated with the proposed detector by cancelling out Depth Of Interaction effects while allowing for placement of the detector close to the body which is increasing the detector’s solid angle. The TMBi’s coincidence photoelectric efficiency is the highest available, with twice the value of LSO/LYSO crystals. The new detector should be able to use accurate time-of-flight (TOF) information through Cherenkov light detection in order to improve the contrast of the reconstructed image. To achieve a breakthrough in this challenging project, the expertise of the existing French CaLIPSO group (CEA-IRFU, CNRS-LAL) will be supplemented by the expertise on high-resolution PET imaging and detector development (WWU-EIMI group), and ultra-purification as well as light and charge detector readout (WWU-PHYSICS group), both from University of Munster. The main objective of this collaborative project is to develop a novel detector system for PET imaging (e.g. human brain PET, small animal PET) with a projected efficiency of 30%, high spatial precision of 1 mm3 , and high time of flight resolution of 100 ps (FWHM). In order to achieve these objectives the project will focus on the following work areas: (1) ultra-purification of TMBi and further characterisation of TMBi for gamma radiation detection, (2) development of an ionisation detector prototype, (3) study of the Cherenkov photon detection in liquid TMBi, (4) Monte Carlo simulation and image reconstruction of a full PET scanner employing the new technology, and (5) evaluation of a final PET detection demonstrator, merging charge and optical readout.

The aim of the ClearMind project is to develop a monolithic gamma ray detector (0.5 MeV to few MeV) with a large surface area (= 25 cm2), high efficiency, high spatial accuracy (< 4 mm3 FWHM ) and high timing accuracy ( < 20 ps FWHM, excluding contributions of the collection and amplification of photoelectrons). Our motivation is to improve the performance of Positron Emission Tomography scanners (PET). We propose to develop a position-sensitive detector consisting of a scintillating crystal on which is directly deposited a photo-electric layer of refractive index greater than that of the crystal. This "scintronic" crystal, which combines scintillation and photoelectron generation, optimizes the transmission of scintillation photons and Cherenkov light photons to the photoelectric layer. We expect a factor 4 gain on the probability of optical photon transmission between the crystal and the photoelectric layer, compared to conventional assemblies using optical contact gels. The crystal will be encapsulated with a micro-channel plate multiplier tube (MCP-MT) in order to amplify the signal and optimize the transit time of the photo-electrons towards the plane of detection anodes (densely pixelated) and thus the temporal and spatial resolutions of the detection chain. The originality of our detector consists in: - Improve the efficiency of light collection in a high-density, and high-effective atomic number crystal by depositing a photoelectric layer directly on the scintillating crystal. - Use the Cherenkov light emission for detection. The gain in optical coupling optimizes the measurement of time based Cherenkov photons, inherently very fast. - Use the map of photoelectrons produced at the surface of the crystal to reconstruct the properties of the gamma interactions by means of robust statistical estimators and information processing using machine learning algorithms. The scintillation photons provide the necessary statistics for a measurement of the energy deposited in the crystal, modest but compatible with a use on a PET imager, and a precise measurement of the coordinates of the interaction position of the gamma ray. - The fast acquisition of signal shapes (SAMPIC technology), which facilitates the optimization of the detector. - The effort to reduce the number of electronic channels (and associated constraints) while keeping optimal performance. We propose to develop the ClearMind prototypes in two phases. Phase 1 consists in producing a "thin" detector, ~ 10 mm, instrumented on one side. The objective is a proof of principle of the technology, the characterization of the performances of this prototype, and its confrontation with a Monte Carlo model, using the GATE simulation tool. This should allow us to set up all the technologies and to concretely understand their stakes. Deadline 18 months. Phase 2 involves the production of a ~ 20 mm thick detector, instrumented on both sides. The objective will then be to produce a detector module of optimized efficiency, spatial and temporal resolutions, close to what would be used in future PET machines. Deadline 30 months. The GATE Monte Carlo simulation will then allow us to assess the potential of the technology to design an enhanced cerebral Time-Of-Flight PET imager, (and alternatively whole body TOF-PET). Our efforts with the manufacturers involved in the development of the prototypes resulted in quotations and delivery times compatible with the schedule and the budget presented in this project.

Understanding how the nuclear force emerges from the basic constituents of matter is one of the challenges of contemporary physics. It is empirically established that the nucleon-nucleon (NN) interaction has an intermediate-range attractive part (for NN distances between 1 and 1.5 fm) and a short-range repulsive part (for NN distances below 1 fm), which is poorly known. The presence of a high momentum tail (k > kF, with kF ~ 250 MeV/c) in the nucleon momentum distribution, and the back-to-back emission of nucleons with such high momenta have been observed in proton and electron induced quasi-free scattering and interpreted in terms of short-range correlations (SRC). SRC, i.e. the combination of the attraction at intermediate range and repulsion at short range of NN potentials give rise to a spatially compact configuration (~1-1.5 fm) of nucleons with high relative momentum. SRC offer a unique laboratory benchmark for the short-range part of NN interaction that plays an important role in calculations involving nuclear matter at high density and momentum, such as neutron stars. Nucleons (protons and neutrons) are commonly considered as the relevant degrees of freedom to describe nuclear properties. Nevertheless, some phenomena fail to be accounted for in this approach, like the European Muon Collaboration effect, which shows that the partonic structure of bound nucleons is modified by the nuclear medium. The striking linear correlation between SRC and EMC effect strength shows that nucleons affected by SRC are susceptible to undergo such modifications. About 20% of nucleons are paired in the SRC regime. Among them, 90% are paired in neutron-proton pairs (isospin T=0). The prevalence of isospin T=0 pairs is associated with the dominance of the tensor interaction, mainly active in the T=0 channel, for NN distances ~1-1.5 fm and implies that the minority species (protons in the case of stable nuclei with mass A>20) has on average higher momentum and kinetic energy than the majority species. The isospin content of SRC has been determined up to now only for stable nuclei with N/Z asymmetry close to 1 (N/Z ~ 1-1.5), and data are integrated over very large intrinsic nucleon momentum windows due to the limited statistics available. Exploring the N/Z and momentum dependence of the isospin content of SRC will allow testing our understanding of SRC. Is the current description of SRC as short-distance and high-relative momentum nucleon pairs correct? What is the role of the different terms of the nuclear interaction (central, tensor) at different relative momenta (and therefore distances)? Are nucleons and mesons the right degrees of freedom to describe nuclear structure when high-momentum probes are involved? The goal of the COCOTIER project is to address these questions bypassing both limitations in statistics and N/Z asymmetry by performing a high-luminosity measurement with radioactive beams in inverse kinematics. The study of the evolution of SRC along the Oxygen isotopic chain from 14O to 24O will be the subject of the first COCOTIER experiment. The experimental method that will be used to probe SRC is the well known Quasi-Free Scattering reaction. In inverse kinematics this demands the use of a proton target, that for luminosity reasons has to be a thick cryogenic liquid hydrogen target. Such a target with a thickness of 20 cm along the beam axis (corresponding of 1.5 g.cm-2 of hydrogen) will be developed at IRFU within the COCOTIER project, and combined with the R3B detection system at the GSI accelerator facility in Germany, a world-unique laboratory capable to deliver radioactive ion beams at energies above 1 GeV/u, key for the extraction of SRC observables. The combination of GSI radioactive ion-beams, the R3B detection system and the liquid hydrogen target from IRFU is a unique asset of the COCOTIER project.

Quarks and gluons (named partons) traversing a QCD medium – either quark-gluon plasma but also confined, cold nuclear matter – are expected to lose energy dominantly through gluon radiation, leading to the phenomenon of jet quenching observed in high-energy heavy ion collisions. Understanding quantitatively parton energy loss is thus a central question of this field, which the present proposal addresses. More specifically, the objective of the project is a systematic investigation of parton energy loss processes in cold nuclear matter. This ambitious program will be carried out through detailed and complementary theoretical, phenomenological, and experimental studies, with measurements performed in hadron-nucleus collisions from fixed-target facilities (COMPASS at the CERN Super Proton Synchrotron, SPS) to colliders (CMS at the Large Hadron Collider, LHC). The synergy between theory, phenomenology and experiment is at the heart of this proposal. The effects of energy loss in the fully coherent regime on various QCD processes will be investigated, such as forward production of light hadrons, heavy hadrons (D and B mesons) and Drell-Yan lepton pairs, in pi-A and p-A collisions at different center-of-mass energies. Another important task is the development of a unified framework enabling the rigorous treatment of parton energy loss in the two most relevant dynamical regimes, namely the Landau-Pomeranchuk-Migdal (partially coherent) regime and the fully coherent regime. In addition, both radiative energy loss processes and parton saturation – expected in nuclei at small values of Bjorken-x and an important topic in the phenomenology of high-energy nuclear collisions – will also be implemented in a unified approach based on first principles. Resulting from this theoretical work, detailed phenomenology of QCD processes in hadron-nucleus collisions will allow for the interpretation of the present data and for providing reliable predictions on future measurements. Closely related to radiative energy loss, the transverse momentum broadening of partons propagating through cold QCD matter will also be investigated, at both theoretical and phenomenological levels. On the experimental side, the measurements of Drell-Yan lepton pairs and quarkonium production will be performed in pion-nucleus collisions at SPS energy by the COMPASS experiment. At the LHC, Drell-Yan, quarkonia and heavy mesons will be measured by the CMS collaboration, as well as forward dijet production. The measurements performed at both SPS and LHC, together with past measurements at Fermilab (FNAL) and Brookhaven (RHIC), will allow for the extraction of the cold nuclear matter transport coefficient at different energies and using different processes. In fine, the phenomenological and experimental results will clarify the contributions of radiative energy loss (in both LPM and fully coherent regimes) on the production of hard processes in nuclear collisions. On top of these research studies, an important aspect of the proposal is that of education of young researchers. This project will allow for the organization of two international high-level schools on QCD, in 2019 and 2021, gathering PhD students and young researchers together with world-class lecturers. The proposal will also lead to outreach activities through the publication of brochures on particle physics and astrophysics, intended to a general audience, as well as for the organization of conferences in high-schools and during public events.

Micromegas detectors are used in a variety of physics projects including in low-energy nuclear physics and neutron-beam related detectors. With this proposal we intend to develop a “transparent” orthogonal strip Micromegas neutron detector with unprecedented position and time resolving data acquisition capabilities, for use at the major neutron time-of-flight facilities. Typical usages are neutron flux and reaction cross section measurements, and neutron beam imaging. A very thin detector with both a segmented anode and segmented mesh, coupled to the dedicated VMM3 chip developed for Micromegas detectors, will lead to an innovative detection device. The new detector will also be used as a time-projection chamber (TPC) to investigate angular distribution measurements of reaction particles of interest for nuclear reaction studies and nuclear data. The TPC mode will be tested in the neutron beam of GELINA with light charged particles and fission fragments.