LIP - Laboratory of Instrumentation and Experimental Particle Physics

The JUpiter ICy moons Explorer (JUICE) mission, launched on 14 April 2023, is currently in its interplanetary cruise phase and is expected to arrive at Jupiter in July 2031. Throughout its eight-year journey to the Jovian system, the spacecraft is exposed to a highly variable radiation environment dominated by galactic cosmic rays (GCRs) and episodic solar energetic particle (SEP) events. Upon arrival at Jupiter, JUICE will encounter one of the most intense radiation environments in the Solar System, characterized by powerful radiation belts populated primarily by highly energetic electrons. Monitoring and characterizing this radiation environment is therefore essential both for scientific return and for spacecraft and instrument safety.To address these challenges, JUICE carries the RADiation-hard Electron Monitor (RADEM). RADEM was designed to measure high-energy protons (5-250 MeV), electrons (0.3-40 MeV), and to some extent ions (Z>=2). Since launch, RADEM has been operating continuously during the cruise phase, providing uninterrupted measurements of the energetic particle environment in interplanetary space.After nearly three years of operations, RADEM has already recorded tens of SEP events associated with solar activity. These observations provide valuable insight into the spatiotemporal evolution, intensity, and spectral characteristics of energetic particles. In this work, we present an overview of RADEM’s in-flight performance and scientific observations to date. We also discuss updates and optimizations to the instrument’s operational settings implemented during cruise, aimed at improving the quality of its measurements.

The BepiColombo Environmental Radiation Monitor (BERM), currently travelling toward Mercury, and the Energetic Particle Detector (EPD) aboard Solar Orbiter are both monitoring the radiation environment in the inner heliosphere. Three Solar Energetic Particle (SEP) events, 2021-07-15, 2022-07-23 and 2023-03-13 were detected simultaneously by the two missions during intervals of favourable magnetic connectivity, providing valuable cases for comparative analysis and instrument intercalibration.We investigated the interplanetary conditions of each event using solar wind plasma and magnetic field observations. Proton anisotropy measurements from Solar Orbiter enabled the identification of isotropic periods during the decay phase of the SEP events, from which representative proton spectra were derived. These spectra were then fitted and compared with BERM observations to obtain intercalibration factors.Our results confirm a high level of agreement between the instruments. For the 2.15 MeV and 6.85 MeV proton channels, we obtained calibration factors of 0.95±0.10 and 1.02±0.30, corresponding to deviations of only 5% and 2%. These findings demonstrate the consistency of SEP measurements by BERM and EPD and highlight the valuable role that planetary missions can play in heliophysics research.

Characterizing the radiation environment on the lunar surface is essential for a safe human and robotic exploration. Having a negligible atmosphere, the Moon is exposed to galactic cosmic rays (GCRs), a continuous high flux of very energetic particles, and solar energetic particles (SEPs), which are accelerated in the solar corona or in coronal mass ejections. These particles can damage biological, electronic systems and other materials and thus hinder or even terminate space missions.To aid future mission planning and habitat design, we developed a Geant4 based model, LUNAIRE, that simulates GCR and SEP propagation through the lunar surface. The model accounts for secondary particle generation on the sub-surface and derives physical quantities such as absorbed dose and Linear Energy Transfer (LET) spectrum at the surface and underground. This model was adapted from the detailed Mars Energetic Radiation Environment (dMEREM) developed by LIP (Laboratory of Instrumentation and Experimental Particle Physics) for ESA (European Space Agency), and includes location dependent surface composition, as well as user custom particle spectra as inputs.We validated the model by comparing the LET (Linear Energy Transfer) spectrum obtained with LUNAIRE to measurements of the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) aboard the Lunar Reconnaissance Orbiter (LRO). Additionally, we compared the spectrum of secondary particles production with those of the HZETRN (High Charge and Energy Transport) code available through OLTARIS (On-Line Tool for the Assessment of Radiation in Space). The results allow for a reconstructed GCR spectra that matches BadhwarO'Neill (BON) Galactic Cosmic Ray Model reference curves across species. We found the LET spectrum to be in good agreement with CRaTER data for both July 2009 (solar minimum available) and July 2015 (solar maximum available). Secondary particle fluxes also match HZETRN results for neutrons and protons but are not so according for electrons and gamma particles. This was attributed to differences in the physics processes of HZETRN comparing to Geant4. These results show that LUNAIRE accurately characterizes the lunar radiation environment that can lead to better forecasts of, and safer missions. Ongoing work includes the evaluation against SEP events, the incorporation of complex topography geometries and validation against other mission results.

A bstract A first study is presented of the cross section for the scattering of same-sign W boson pairs via the detection of a τ lepton. The data from proton-proton collisions at the center-of-mass energy of 13 TeV were collected by the CMS detector at the LHC, and correspond to an integrated luminosity of 138 fb −1 . Events were selected that contain two jets with large pseudorapidity and large invariant mass, one τ lepton, one light lepton (e or μ ), and significant missing transverse momentum. The measured cross section for electroweak same-sign WW scattering is $${1.44}_{-0.56}^{+0.63}$$ times the standard model prediction. In addition, a search is presented for the indirect effects of processes beyond the standard model via the effective field theory framework, in terms of dimension-6 and dimension-8 operators.

Sufficiently strong and long-lasting first-order phase transitions can produce primordial black holes (PBHs) that contribute substantially to the dark matter abundance of the Universe, and can produce large-scale primordial magnetic fields. We study these mechanisms in a generic class of conformal U(1)' models that also explain active neutrino oscillation data via the type-I seesaw mechanism.We find that phase transitions that occur at seesaw scales between 104 GeV and 1011 GeV produce gravitational wave signals (from the dynamics of the phase transition and from the decay of cosmic string loops) at LISA/ET that can be correlated with microlensing signals of PBHs at the Roman Space Telescope, while scales near 1011 GeV can be correlated with Hawking evaporation signals at future gamma-ray telescopes. LISA can probe the entire range of PBH masses between 1 × 10-16 M ⊙ and 8 × 10-11 M ⊙ if PBHs fully account for the dark matter abundance. For Z' masses between 40 TeV and 104 TeV, and 10 TeV right-handed neutrinos, helical magnetic fields can be produced with magnitudes ≳ 0.5 pG and coherence lengths ≳ 0.008 Mpc, above current blazar lower bounds.

According to recent lore, it is difficult to explain the evidence for a stochastic gravitational wave background obtained by pulsar timing arrays with supercooled first-order phase transitions (FOPTs). We demonstrate that supercooled FOPTs in dark U(1) ′ models with a conformal dark sector easily explain the nHz signal at NANOGrav.

Context. Following its launch in April 2023, JUICE is now in its cruise phase to Jupiter, where it is scheduled to arrive in July 2031. JUICE carries a radiation monitor, namely the RADiation hard Electron Monitor (RADEM) to measure protons, electrons, and ions, detecting particles coming mainly from the anti-Sunwards direction. On 13 May 2024, a large solar energetic particle (SEP) event took place in association with an eruption close to the western limb of the Sun, as seen from Earth. Providentially, at that time, JUICE was located very close to STEREO-A, separated by only 0.13 au in radial distance, 0.3° in latitude, and 1.6° in longitude. Aims. Our main aims are to characterise the observations within the interplanetary (IP) context whereby SEPs propagated to near-Earth, JUICE, and STEREO-A observers, while performing a first comparison of energetic particle instruments on board JUICE and STEREO-A spacecraft. Methods. We analysed the IP context using in situ measurements and studied the proton anisotropies measured by near-Earth spacecraft and STEREO-A. We focussed on an isotropic period during the decay phase of the SEP event to compute the proton energy spectrum. We fit the STEREO-A spectrum and compared it to the one measured by SOHO and JUICE. Results. We find the proton spectral indices measured by JUICE, SOHO, and STEREO-A to be similar. The proton fluxes measured by RADEM are in agreement with those from STEREO-A, with a deviation of less than 25%. Conclusions. The RADEM instrument aboard JUICE is a valuable tool for measuring SEP events in the heliosphere, providing an excellent opportunity to study and characterise the energetic particle environment in the solar wind between 0.65 and 5.2 au. The intercalibration factors between the fluxes measured by STEREO-A and JUICE at the effective energies of 6.9 MeV, 13.3 MeV, 21.6 MeV, and 31.2 MeV are 1.02, 1.23, 1.12, and 0.95, respectively. We note that these intercalibration factors are valid only until 2024 July 10, when the configuration of the RADEM instrument was changed.

Abstract A search for a pseudoscalar a produced in association with a top-quark pair, or in association with a single top quark plus a W boson, with the pseudoscalar decaying into b -quarks ( $$a\rightarrow b\bar{b}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>a</mml:mi> <mml:mo>→</mml:mo> <mml:mi>b</mml:mi> <mml:mover> <mml:mrow> <mml:mi>b</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> </mml:math> ), is performed using the full Run 2 data sample using a dileptonic decay mode signature. The search covers pseudoscalar boson masses between 12 and 100 GeV and involves both the kinematic regime where the decay products of the pseudoscalar are reconstructed as two standard b -tagged small-radius jets, or merged into a large-radius jet due to its Lorentz boost. No significant excess relative to expectations is observed. Assuming a branching ratio $$\text {BR}(a\rightarrow b\bar{b})=100\% $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mtext>BR</mml:mtext> <mml:mo>(</mml:mo> <mml:mi>a</mml:mi> <mml:mo>→</mml:mo> <mml:mi>b</mml:mi> <mml:mover> <mml:mrow> <mml:mi>b</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> <mml:mo>)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>100</mml:mn> <mml:mo>%</mml:mo> </mml:mrow> </mml:math> , the range of pseudoscalar masses between 50 and 80 GeV is excluded at 95% confidence level for a coupling of the pseudoscalar to the top quark of 0.5, while a coupling of 1.0 is excluded at 95% confidence level for the masses considered, with the coupling defined as the strength modifier of the Standard Model Yukawa coupling.