Max Planck Institute for Nuclear Physics

We present a deep learning pipeline to perform a model-independent, likelihood-free search for anomalous (i.e., non-background) events in the proposed next-generation multi-ton scale liquid xenon-based direct detection experiment, DARWIN. We train an anomaly detector comprising a variational autoencoder (VAE) and a classifier on high-dimensional simulated detector response data and construct a 1D anomaly score to reject the background-only hypothesis in the presence of an excess of non-background-like events. We use simulated validation data to determine the power of the method to reject the background-only hypothesis in the presence of a WIMP dark matter signal, without any model-dependent assumption about the nature of the signal. We show that our neural networks learn relevant features of the events from low-level, high-dimensional detector outputs, avoiding lossy and computationally expensive compression into lower-dimensional observables. Our approach is complementary to the usual likelihood-based analysis, in that it reduces the reliance on many of the corrections and cuts that are traditionally part of the analysis chain, with the potential of achieving higher accuracy and significant reduction of analysis time. We envisage the methodology presented in this work augmenting or complementing likelihood-based and other data-driven methods currently utilized in the DARWIN (and in the future, XLZD) analysis pipeline.

We report experimental absolute total and partial ionization cross sections for electron collisions with chlorotrifluorocarbon (CFC-13, CClF3) and chlorodifluoromethane (HCFC-22, CHClF2) in the energy range from 20 to 1000 eV. For CClF3 the ionic fragments CF3+ and CClF2+ were identified to have the highest ionization cross sections, indicating a high release of chlorine and fluorine atoms. CHClF2 dissociates primarily into C(H)F2+, C(H)ClF+, and C(H)Cl+ with the release of Cl and/or F atoms. For CHClF2 single and double charged species, adiabatic ionization and partial potential energy surface calculations were performed to obtain insights into the formation-dynamics of neutral chlorine and fluorine and the pathways for the formation of metastable dications. While CHClF22+ is formed in a single-step double-electron emission, unstable CClF32+ dissociates and CClF22+ is observed. Both metastable dications have a triangular planar-like shape and show enhanced dipole moments.

The use of high-precision measurements of the g factor of single-electron ions is considered as a detailed probe for physics beyond the standard model. The contribution of the exchange of a hypothetical force-carrying scalar boson to the g factor is calculated for the ground state of H-like ions and used to derive bounds on the parameters of that force. Similarly to the isotope shift, we employ the nuclide shift, i.e., the difference for elements with different proton and/or neutron numbers, in order to increase the experimental sensitivity to the new physics contribution. In particular we find, combining available measurements with current precision with different ions, that the coupling constant for the interaction between an electron and a proton can be constrained up to 3 orders of magnitude better than with the best current atomic data and theory.

Abstract Based on the experimental Cooler Storage Ring in Lanzhou, we directly determined the masses of 27 S and 26 P using Bρ -defined isochronous mass spectrometry. The mass excesses were determined to be 17,437(24) keV for 27 S and 10,997(10) keV for 26 P. These values yield a proton separation energy of 849(26) keV for 27 S, representing an eightfold precision improvement over the previous one of 581(214) keV. With precisely measured masses, we evaluated the thermonuclear 26 P( p , γ ) 27 S reaction rate under X-ray burst conditions. The updated rate is enhanced within the 0.4–2 GK temperature range, reaching up to 5 times the previous rate at 1 GK. The uncertainty of the reverse 27 S( γ , p) 26 P reaction rate is drastically reduced with the new high-precision mass results, from over 10 orders of magnitude to less than one. We further assessed the impact of the revised rates on the nucleosynthesis in Type I X-ray bursts using a one-zone postprocessing model. The results show that the final abundance ratio of 27 S to 26 P is increased by about 1 order of magnitude, indicating a more efficient reaction flow toward 27 S. Although the sequence 25 Si( p , γ ) 26 P( p , γ ) 27 S( β + ) 27 P is not on the main rp -process path, it emerges as a nonnegligible branch contributing to 27 P synthesis.

Laser-driven dynamics in polyatomic molecules poses a complex many-body problem. Understanding intense light-matter interaction is crucial for steering intramolecular quantum dynamical processes. Here, we record time-resolved x-ray diffraction images of molecules during and after their interaction with intense near-infrared fields, giving direct access to structural changes of the molecules and their fragmentation in real time. Tuning the intensity of the excitation pulses, we uncover a transition from a weak-field regime of excited but stable molecules to a high-field regime dominated by Coulomb explosion. In the transition region, the molecules expand by up to 50% of their initial size within just 140 fs, with major fragmentation only setting in afterward. This work demonstrates that x-ray diffractive imaging is capable of retrieving time-resolved structural information of large molecules reshaped by intense laser fields. Laser-driven fragmentation is a first step toward observing molecular processes modified by laser fields of increasing intensity.

Abstract The detection of high-energy astrophysical multimessengers establishes a connection between ultra-high-energy cosmic rays (UHECRs) and powerful cosmic accelerators. Interactions of UHECRs with radiation fields and interstellar matter generate very-high-energy (VHE) gamma rays and neutrinos, making them key components in the multimessenger framework. This study examines the cosmogenic gamma-ray and neutrino fluxes resulting from UHECR propagation in starburst galaxies with supernova remnants, with a particular focus on NGC 1068, a well-established high-energy neutrino source. Using extragalactic simulations, we calculate the upper limit on cosmic-ray luminosity, applying upper limits on gamma-ray fluxes derived from observations by H.E.S.S. and MAGIC observatories. Our analysis incorporates the effects of both extragalactic and galactic magnetic fields on particle propagation, constraining the maximum extragalactic magnetic field (EGMF) intensity to 10 −14 G to ensure that at least 90% of injected UHECRs successfully reach Earth. The results provide upper limits on gamma-ray and neutrino fluxes, estimates of UHECR luminosity for individual sources, and predictions for the detection capabilities of the Cherenkov Telescope Array Observatory regarding gamma-ray emission from NGC 1068. Combining gamma-ray, neutrino, and UHECR observations reinforces the importance of multimessenger approaches in understanding the nature of high-energy astrophysical sources and their role in cosmic-ray acceleration.

An amplitude analysis of the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msubsup> <a:mi mathvariant="normal">Ξ</a:mi> <a:mi>c</a:mi> <a:mo>+</a:mo> </a:msubsup> <a:mo stretchy="false">→</a:mo> <a:mi>p</a:mi> <a:msup> <a:mi>K</a:mi> <a:mo>−</a:mo> </a:msup> <a:msup> <a:mi>π</a:mi> <a:mo>+</a:mo> </a:msup> </a:math> decay together with a measurement of the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:msubsup> <e:mi mathvariant="normal">Ξ</e:mi> <e:mi>c</e:mi> <e:mo>+</e:mo> </e:msubsup> </e:math> polarization vector in semileptonic beauty-hadron decays is presented. The analysis is performed using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"> <h:mn>9</h:mn> <h:mtext> </h:mtext> <h:mtext> </h:mtext> <h:msup> <h:mi>fb</h:mi> <h:mrow> <h:mo>−</h:mo> <h:mn>1</h:mn> </h:mrow> </h:msup> </h:math> . An amplitude model is developed and the resonance fractions as well as two- and three-body decay parameters are reported. A sizeable <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"> <j:msubsup> <j:mi mathvariant="normal">Ξ</j:mi> <j:mi>c</j:mi> <j:mo>+</j:mo> </j:msubsup> </j:math> polarization is found. A large sensitivity of the <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"> <m:msubsup> <m:mi mathvariant="normal">Ξ</m:mi> <m:mi>c</m:mi> <m:mo>+</m:mo> </m:msubsup> <m:mo stretchy="false">→</m:mo> <m:mi>p</m:mi> <m:msup> <m:mi>K</m:mi> <m:mo>−</m:mo> </m:msup> <m:msup> <m:mi>π</m:mi> <m:mo>+</m:mo> </m:msup> </m:math> decay to the polarization is seen, making the amplitude model suitable for <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"> <q:msubsup> <q:mi mathvariant="normal">Ξ</q:mi> <q:mi>c</q:mi> <q:mo>+</q:mo> </q:msubsup> </q:math> polarization measurements in other systems.

The generation of dense electron-positron pair beams in the laboratory can enable direct tests of theoretical models of γ-ray bursts and active galactic nuclei. We have successfully achieved this using ultrarelativistic protons accelerated by the Super Proton Synchrotron at CERN. In the first application of this experimental platform, the stability of the pair beam is studied as it propagates through a meter-length plasma, analogous to TeV γ-ray-induced pair cascades in the intergalactic medium. It has been argued that pair beam instabilities disrupt the cascade, thus accounting for the observed lack of reprocessed GeV emission from TeV blazars. If true, this would remove the need for a moderate strength intergalactic magnetic field to explain the observations. We find that the pair beam instability is suppressed if the beam is not perfectly collimated or monochromatic, hence the lower limit to the intergalactic magnetic field inferred from γ-ray observations of blazars is robust.

We perform a detailed study of the cosmological constraints on the decay of a relic particle ϕ into neutrinos, ϕ → νν̅, in particular those arising from the observed light-element abundances in the early Universe. Several processes are relevant, including final-state radiation associated with the decay, as well as subsequent interactions of the injected neutrinos with the thermal background neutrinos or between themselves. All processes generically contribute to the production of electromagnetic and often also hadronic material and may therefore induce late-time photodisintegration and hadrodisintegration reactions, i.e. the destruction of light elements that have previously been formed during BBN. Here, we examine this scenario with a Monte-Carlo inspired probabilistic approach rather than Boltzmann techniques, taking into account all of these different reactions as well as their interplay. We find the resulting constraints to be very significant, covering a broad range of previously unexplored masses and lifetimes of the relic source particle.