Energy-differential cross section of the C-nat(n, p) and C-nat(n,d) reactions was measured at the neutron time-of-flight facility n_TOF at CERN. The measurement was performed in the first experimental area (EAR1; flight path of 182.5 m). Two position-sensitive Delta E-E silicon telescopes were used. Two naturally occurring carbon isotopes, C-12 and C-13, contribute to the reactions on natural carbon, with the (n,p) reaction threshold at 13.7 MeV and the (n,d) threshold at 14.9 MeV (determined by the C-12 isotope for both reactions). This paper provides the details of the analysis leading to the final results published previously as a Letter. The cross-section results are reported up to 25 MeV. During the data analysis the population of the excited states in the daughter nuclei B-11, B-12, and B-13 had to be considered, requiring the adoption of the branching ratios and angular distributions of the emitted particles from an external source of information. TALYS-2.0 calculations were used as the main source and an in-depth analysis of the model-related uncertainties was performed. The n_TOF results are largely inconsistent with the major evaluation libraries. On the other hand, an unexpected agreement is found with TALYS-2.0 calculations. Specifically, the obtained cross section for the (n,p) reaction is significantly higher than in the available evaluations, fully supporting the earlier finding from an integral measurement at n_TOF.

Neutron-induced reaction cross sections of short-lived nuclei are imperative to understand the origin of heavy elements in stellar nucleosynthesis and for societal applications, but their measurement is extremely complicated due to the radioactivity of the targets involved. One way of overcoming this issue is to combine surrogate reactions with the unique possibilities offered by heavy-ion storage rings. In this work, we describe the first surrogate-reaction experiment in inverse kinematics, which we successfully conducted at the Experimental Storage Ring (ESR) of the GSI/FAIR facility, using the ^{208}Pb(p,p^{'}) reaction as a surrogate for neutron capture on ^{207}Pb. Thanks to the outstanding detection efficiencies possible at the ESR, we were able to measure for the first time the neutron-emission probability as a function of the excitation energy of ^{208}Pb. We have used this probability to select different descriptions of the γ-ray strength function and nuclear level density, and provide reliable results for the neutron-induced radiative capture cross section of ^{207}Pb at energies for which no experimental data exist.

The probabilities for gamma-ray and particle emission as a function of the excitation energy of a decaying nucleus are valuable observables for constraining the ingredients of the models that describe the deexcitation of nuclei near the particle emission threshold. These models are essential in nuclear astrophysics and applications. In this paper, we have for the first time simultaneously measured the gamma-ray and neutron emission probabilities of 208Pb. The measurement was performed in inverse kinematics at the Experimental Storage Ring (ESR) of the GSI/FAIR facility, where a 208Pb beam interacted through the 208Pb(p, p') reaction with a hydrogen gas jet target. Instead of detecting the gamma rays and neutrons emitted by 208Pb, we detected the heavy beamlike residues produced after gamma and neutron emission. These heavy residues were fully separated by a dipole magnet of the ESR and were detected with outstanding efficiencies. The comparison of the measured probabilities with model calculations has allowed us to test and select different descriptions of the gamma-ray strength function and the nuclear level density available in the literature.

We present the first measurement of the ^{47}K(d,pγ)^{48}K transfer reaction, performed in inverse kinematics using a reaccelerated beam of ^{47}K. The level scheme of ^{48}K has been greatly extended, with nine new bound excited states identified and spectroscopic factors deduced. Uniquely, the ^{47}K(d,p) reaction gives access to nuclear states that are sensitive to the interaction of protons and neutrons in the widely spaced 1s and fp orbitals, respectively. Detailed comparisons with SDPF-U and SDPF-MU shell-model calculations reveal a number of discrepancies between theory and experiment. Intriguingly, a systematic overestimation of spectroscopic factors and a poor reproduction of the energies for 1^{-} states suggests that the mixing between the πs_{1/2}^{1}d_{3/2}^{4} and πs_{1/2}^{2}d_{3/2}^{3} proton configurations in ^{48}K is not correctly described using current interactions, challenging our description of light nuclei around the N=28 island of inversion.

Since the first 40 Ar beam accelerated 40 years ago at an energy of 44 MeV per nucleon, GANIL, Grand Accelerateur National d’Ions Lourds, has undergone continuous evolution, with some major upgrades, to remain at the forefront of basic research in accelerator-based science. Because basic science in nuclear physics is closely linked to nuclear industry needs, GANIL can make significant contributions in the knowledge required for improving precision of nuclear data of interest for nuclear energy or health applications. New facility NFS for neutron beams allows high accuracy nuclear data in neutron-induced reactions. Accelerated actinide beams like 238 U or 232 Th allow new-generation nuclear data in the field of nuclear fission. Heavy-ion beams allow the study of radiation in living organisms as part of the development of new cancer therapy techniques as well as space journeys. The instrumentation developed by GANIL offers modern dosimetry techniques for hadrontherapy. Finally, the irradiation of matter enables the investigation of new materials and more resistant electronic components for nuclear and space industries. Some of these developments are done in collaboration with local or national industries to develop the skills and innovation to meet future challenges.

Using proton-proton collision data corresponding to an integrated luminosity of 140 fb$^{-1}$ collected by the CMS experiment at $\sqrt{s}$ = 13 TeV, the $\Lambda_\text{b}^0$ $\to$ J/$\psi\Xi^-$K$^+$ decay is observed for the first time, with a statistical significance exceeding 5 standard deviations. The relative branching fraction, with respect to the $\Lambda_\text{b}^0$ $\to$ $\psi$(2S)$\Lambda$ decay, is measured to be $\mathcal{B}$($\Lambda_\text{b}^0$ $\to$ J/$\psi\Xi^-$K$^+$)/$\mathcal{B}$( $\Lambda_\text{b}^0$ $\to$ $\psi$(2S)$\Lambda$) = [3.38 $\pm$ 1.02 $\pm$ 0.61 $\pm$ 0.03]%, where the first uncertainty is statistical, the second is systematic, and the third is related to the uncertainties in $\mathcal{B}$($\psi$(2S) $\to$ J/$\psi\pi^+\pi^-$) and $\mathcal{B}$($\Xi^-$ $\to$ $\Lambda\pi^-$).

Improved resistive plate chambers (iRPCs) will be installed in the challenging forward region of the compact muon solenoid (CMS) during its Phase-2 upgrade. The design target of iRPC time resolution is 1.5 ns. It will help the Level-1 trigger system distinguish the muons from high backgrounds and improve the trigger efficiency. Studying the time resolution after integrating the new backend electronics boards (BEB) is essential for ensuring timely performance. In this system, a time reference (Tref) signal is distributed by the BEB to several frontend electronics boards (FEB) to reset the time-to-digital converters (TDC). In the CMS experiment, the arrangement of the iRPC chambers and on-chamber FEBs is at different positions, resulting in varying Tref arrival times on the FEB side. This paper describes the measures taken to ensure the time resolution of the single path and adjust the time base for multi-paths. Unique designs were implemented in the chamber, FEB, and BEB to ensure a satisfactory time resolution. Tref adjustments for different paths were performed in bunch crossing steps (24.950 ns) in the BEB using shift registers. And the sub-bunch crossing adjustment steps were performed in the FEB using the TDC correction module. Finally, the arrival time differences of Tref on different FEBs were less than 1.25 ns after adjustment. The time resolution of the FEB–BEB system was observed to be 32 ps. The time resolution of the chamber FEB–BEB system was first measured and is 554 ps at an iRPC working point of 7200 V. In addition, the Tref arrival time differences of different paths were adjusted from − 99.923 (− 90.113) ns to 0.073 (− 0.141) ns. The test results revealed that the system time resolution and Tref adjustment performed by the BEB met the Phase-2 upgrade goals.

In view of the High Luminosity upgrade of the CERN LHC, the forward CMS Muon spectrometer will be extended with two new stations of improved Resistive Plate Chambers (iRPC) covering the pseudorapidity range from 1.8 to 2.4. Compared to the present RPC system, the gap thickness is reduced to lower the avalanche charge, and an innovative 2D strip readout geometry is proposed. These improvements will allow iRPC detector to cope with higher background rates. A new Front-End-Board (FEB) is designed to readout iRPC signals with a threshold as low as 30fC and an integrated Time Digital Converter with a resolution of 30ps. In addition, the communication bandwidth is significantly increased by using optical fibers. The history, final design, certification, and calibration of this FEB are presented.

In the context of climate change, one of the main contributors to global warming is the greenhouse effect. Regulations have been implemented in different areas of society to reduce or ban the use of Greenhouse Gases (GHG), such as Tetrafluoroethane (TFE). Despite the fact that large-scale experiments (such as the ones held at CERN) have been excluded from these restrictions, it is necessary to look for alternatives more eco-friendly to the environment. In this work we present performance studies for RPC detectors using eco-friendly gas mixtures tested at the Gamma Irradiation Facility (GIF++) at CERN in the context of the Phase II upgrade of the CMS detector.

ALICE (A Large Ion Collider Experiment) studies the Quark-Gluon Plasma (QGP): a deconfined state of nuclear matter obtained in ultra-relativistic heavy-ion collisions. One of the key probes for QGP characterization is the study of quarkonia and open heavy flavor production, of which ALICE exploits the muonic decay. In particular, a set of Resistive Plate Chambers (RPCs), placed in the forward rapidity region of the ALICE detector, is used for muon identification purposes. The correct operation of these detectors is ensured by the choice of the proper gas mixture. Currently they are operated with a mixture of C2H2F4, i-C4H10 and SF6 but, starting from 2017, new EU regulations have enforced a progressive phase-out of C(2)H(2)F(4 )because of its large Global Warming Potential (GWP), which is making it difficult and costly to purchase. Moreover, CERN asked LHC experiments to reduce greenhouse gases emissions, to which RPC operation contributes significantly. A possible candidate for C(2)H(2)F(4 )replacement is the C3H2F4 (diluted with other gases, such as CO2), which has been extensively tested using cosmic muons. Promising gas mixtures have been devised; the next crucial steps are the detailed in-beam characterization of such mixtures as well as the study of their performance under increasing irradiation levels. This contribution will describe the methodology and results of beam tests carried out at the CERN Gamma Irradiation Facility (equipped with a high activity Cs-137 source and muon beam) with an ALICE-like RPC prototype, operated with several mixtures with varying proportions of CO2, C3H2F4, i-C4H10-and SF6 Absorbed currents, efficiencies, prompt charges, cluster sizes, time resolutions and rate capabilities will be presented, both from digitized (for detailed shape and charge analysis) and discriminated (using the same front-end electronics as employed in ALICE) signals.

The pygmy dipole resonance (PDR) has been the subject of numer-ous studies, both experimental and theoretical. Indeed, the study of the PDR has been and still is of great interest since it allows to constrain the symmetry energy, an important ingredient of the equation of state of nuclear matter that describes the matter within neutron stars. Moreover, the PDR is predicted to play a key role in the r-pro cess via the increase of the neutron capture rate. However, despite numerous experiments dedicated to the study of the PDR, a consistent description is still missing. In this context, we have proposed to study the PDR using a new probe: the neutron inelastic scattering reaction (n,n'-y). An experiment to study the pygmy resonance in 140Ce using the (n,n'-y) reaction has been performed in Septem-ber 2022. This experiment has been made possible thanks to the high-intensity proton beam of the new accelerator SPIRAL2 at GANIL and the NFS (Neutron For Science) facility. The experimental setup was composed of the new generation multi-detectors PARIS, for the detection of-y-rays coming from the de-excitation of the PDR, and MONSTER, for the detection of scattered neutrons. In this article, the experiment motivation and description are presented.

The improved Resistive Plate Chambers (iRPC) are designed using thin low resistivity High-Pressure Laminate (HPL) gaps. They are proposed to equip the very forward region of the Compact Muon Solenoid (CMS) detector, as they can stand rates ∼2kHz/cm2. To withstand 3 times higher rates than the installed CMS RPC chambers, the HPL electrode thickness was reduced from 2 mm to 1.4 mm. The gas gain of the detector is dependent on the gas pressure and temperature which requires correcting for the applied voltage to keep detector operational characteristics such as efficiency, cluster size and noise rate constant. Herein, we study the pressure correction at constant temperature for CMS iRPC and compare its correction coefficient with the one for the 2 mm RPC gap technology. Pressure correction parameters for both technologies are found compatible.

The CMS detector, including its muon system, has been operating at the CERN LHC in increasingly challenging conditions for about 15 years. The muon detector was designed to provide excellent triggering and track reconstruction for muons produced in proton–proton collisons at an instantaneous luminosity ( ℒ ) of 1 × 10^34 cm ^-2 s ^-1 . During the Run 2 data-taking period (2015–2018), the LHC achieved an instantaneous luminosity of twice its design value, resulting in larger background rates and making the efficient detection of muons more difficult. While some backgrounds result from natural radioactivity, cosmic rays, and interactions of the circulating protons with residual gas in the beam pipe, the dominant source of background hits in the muon system arises from proton–proton interactions themselves. Charged hadrons leaving the calorimeters produce energy deposits in the muon chambers. In addition, high-energy particles interacting in the hadron calorimeter and forward shielding elements generate thermal neutrons, which leak out of the calorimeter and shielding structures, filling the CMS cavern. We describe the method used to measure the background rates in the various muon subsystems. These rates, in conjunction with simulations, can be used to estimate the expected backgrounds in the High-Luminosity LHC. This machine will run for at least 10 years starting in 2029 reaching an instantaneous luminosity of ℒ = 5 ×10^34 cm^-2 s^-1 and increasing ultimately to ℒ = 7.5 ×10^34 cm^-2 s^-1 . These background estimates have been a key ingredient for the planning and design of the muon detector upgrade.

The Compact Muon Solenoid (CMS) experiment will undergo phase-II upgrade to enhance the capacity of detectors in the High-Luminosity Large Hadron Collider era. An important extension involves the installation of the Improved Resistive Plate Chambers (iRPC) in the most forward part of the endcap muon system. The iRPC detector addresses the efficiency drop experienced by the current CMS trigger system for single muon triggers in the high pseudorapidity region. It features a double-ended read-out method, allowing the determination of the hit position along the strip using the time difference between signals from both ends. This feature provides precise spatial information for clustering. To utilize this feature and integrate iRPC cluster information into the CMS trigger system, this paper proposes a 2-Dimensional (2D) cluster-finding algorithm. This algorithm provides the 2D coordinates to CMS trigger system, with each cluster being timestamped to reduce time ambiguity in endcap trajectory reconstruction. The proposed algorithm was implemented in the firmware of the iRPC Back-End Electronics and evaluated using a dedicated cosmic muon setup. The results show a position precision of 2.55 cm and an algorithm efficiency better than 99%, demonstrating the algorithm's potential to improve muon detection and trigger efficiency in the CMS endcap region.

AbstractThe CMS detector, including its muon system, has been operating at the CERN LHC in increasingly challenging conditions for about 15 years. The muon detector was designed to provide excellent triggering and track reconstruction for muons produced in proton–proton collisons at an instantaneous luminosity ($$\mathcal {L}$$ L ) of $$1 \times 10^{34}$$ 1 × 10 34 cm$$^{-2}$$ - 2 s$$^{-1}$$ - 1 . During the Run 2 data-taking period (2015–2018), the LHC achieved an instantaneous luminosity of twice its design value, resulting in larger background rates and making the efficient detection of muons more difficult. While some backgrounds result from natural radioactivity, cosmic rays, and interactions of the circulating protons with residual gas in the beam pipe, the dominant source of background hits in the muon system arises from proton–proton interactions themselves. Charged hadrons leaving the calorimeters produce energy deposits in the muon chambers. In addition, high-energy particles interacting in the hadron calorimeter and forward shielding elements generate thermal neutrons, which leak out of the calorimeter and shielding structures, filling the CMS cavern. We describe the method used to measure the background rates in the various muon subsystems. These rates, in conjunction with simulations, can be used to estimate the expected backgrounds in the High-Luminosity LHC. This machine will run for at least 10 years starting in 2029 reaching an instantaneous luminosity of $$\mathcal {L} = 5 \times \text {10}^\text {34}\,\text {cm}^\text {-2}\,\text {s}^\text {-1}$$ L = 5 × 10 34 cm -2 s -1 and increasing ultimately to $$\mathcal {L} = 7.5 \times \text {10}^\text {34}\,\text {cm}^\text {-2}\,\text {s}^\text {-1}$$ L = 7.5 × 10 34 cm -2 s -1 . These background estimates have been a key ingredient for the planning and design of the muon detector upgrade.

Resistive Plate Chambers (RPCs) are gaseous detectors widely used in high energy physics experiments, operating with a gas mixture primarily containing Tetrafluoroethane (C2H2F4), commonly known as R134a, which has a global warming potential (GWP) of 1430. To comply with European regulations, the RPC EcoGas@GIF++ collaboration, involving ALICE, ATLAS, CMS, LHCb/SHiP, and EP-DT communities, has undertaken intensive R&D efforts to explore new environmentally friendly alternative gas mixtures for RPC technology. A leading alternative under investigation is HFO1234ze, boasting a low GWP of 6 and demonstrating reasonable performance compared to R-134a. Over the past few years, RPC detectors with slightly different characteristics and electronics have been studied using HFO and CO2-based gas mixtures at the CERN Gamma Irradiation Facility. An aging test campaign was launched in August 2022, and during the latest test beam in July 2023, all detector systems underwent evaluation. This contribution will report the results of the aging studies and the performance evaluations of the detectors with and without irradiation.

^{140}Ce(n,γ) is a key reaction for slow neutron-capture (s-process) nucleosynthesis due to being a bottleneck in the reaction flow. For this reason, it was measured with high accuracy (uncertainty ≈5%) at the n_TOF facility, with an unprecedented combination of a high purity sample and low neutron-sensitivity detectors. The measured Maxwellian averaged cross section is up to 40% higher than previously accepted values. Stellar model calculations indicate a reduction around 20% of the s-process contribution to the Galactic cerium abundance and smaller sizeable differences for most of the heavier elements. No variations are found in the nucleosynthesis from massive stars.

Results obtained by the RPC ECOgas@GIF++ Collaboration, using Resistive Plate Chambers operated with new, eco-friendly gas mixtures, based on Tetrafluoropropene and carbon dioxide, are shown and discussed in this paper. Tests aimed to assess the performance of this kind of detectors in high-irradiation conditions, analogous to the ones foreseen for the coming years at the Large Hadron Collider experiments, were performed, and demonstrate a performance basically similar to the one obtained with the gas mixtures currently in use, based on Tetrafluoroethane, which is being progressively phased out for its possible contribution to the greenhouse effect. Long term aging tests are also being carried out, with the goal to demonstrate the possibility of using these eco-friendly gas mixtures during the whole High Luminosity phase of the Large Hadron Collider.

In the last few years, an intense R D activity on particle detectors for future HEP applications has been carried on with the aim of developing new techniques as well as studying the performance of already existing detectors when operated in a high rate environment. As for Resistive Plate Chamber detectors, the main challenges to face are the improvement of their detection capabilities and longevity at very high-rates, and the search for new eco-friendly gasmixtures free from greenhouse components. Results obtained in the framework of the RPC ECOGas@GIF++ Collaboration on a thin-Resistive Plate Chamber exposed at the CERN Gamma Irradiation Facility and operated with eco-friendly gas mixtures based on Tetrafluoropropene and Carbon dioxide will be discussed in this paper.

Nuclear fission is still one of the most complex physical processes due to the interplay between macroscopic and microscopic nuclear properties that decide the output. An example of this coupling is the presence of nuclear dissipation as an important ingredient that contributes to drive the dynamics and has a clear impact on the time of the process. However, different theoretical interpretations and scarce experimental data make it poorly understood. At low excitation energy, the relative yields of fragments even and odd atomic numbers show a clear difference, which can be quantified with the so-called even-odd effect. This seemingly mundane property can be used to obtain information about the energy dissipated during the process and the role of structure in its dynamics. In this paper, the study of the even-odd effect for elasticand transfer-induced fission data is discussed. A clear connection with particular fragment shells and the dissipation energy is found, as detailed in Ref. [1]. In addition, preliminary results from quasi-fission data show the formation of a relatively large even-odd effect, which suggests a process with low dissipation mainly consisting in the exchange of nucleon pairs.