Thu·Apr 10, 2025Thursday·April 10, 2025

1. 01*

   European Strategy for Particle Physics Update -- PIONEER: a next generation rare pion decay experiment

   PIONEER Collaboration: A. Adelmann🇨🇭 · W. Altmannshofer🇺🇸 · S. Ban🇯🇵 · O. Beesley🇺🇸 · A. Bolotnikov🇺🇸 · T. Brunner · D. Bryman🇨🇦 · Q. Buat · L. Caminada🇨🇭 · J. Carlton🇺🇸 · S. Chen🇨🇳 · M. Chiu🇺🇸 and 66 other authors

   PIONEER is a rapidly developing effort aimed to perform a pristine test of lepton flavour universality (LFU) and of the unitarity of the first row of the CKM matrix by significantly improving the measurements of rare decays of the charged pion. In Phase I, PIONEER aims to measure the charged-pion branching ratio to electrons vs.\ muons $R_{e/\mu }$ to 1 part in $10^4$, improving the current experimental result $R_{e/\mu }\text{(exp)}=1.2327(23)\times 10^{-4}$ by a factor of 15. This precision on $R_{e/\mu }$ will match the theoretical accuracy of the SM prediction allowing for a test of LFU at an unprecedented level, probing non-SM explanations of LFU violation through sensitivity to quantum effects of new particles up to the PeV mass scale. Phase II and III will aim to improve the experimental precision of the branching ratio of pion beta decay, ${\pi }^{+}\to {\pi }^0{e}^{+}\nu (\gamma )$, currently at $1.036(6)\times 10^{-8}$, by a factor of three and six, respectively. The improved measurements will be used to extract $V_{ud}$ in a theoretically pristine manner. The ultimate precision of $V_{ud}$ is expected to reach the 0.05\,\% level, allowing for a stringent test of CKM unitarity. The PIONEER experiment will also improve the experimental limits by an order of magnitude or more on a host of exotic decays that probe the effects of heavy neutrinos and dark sector physics. This input to the 2026 update of the European Strategy for Particle Physics Strategy describes the physics motivation and the conceptual design of the PIONEER experiment, and is prepared based on the PIONEER proposal submitted to and approved with high priority by the PSI program advisory committee (PAC). Using intense pion beams, and state-of-the-art instrumentation and computational resources, the PIONEER experiment is aiming to begin data taking by the end of this decade.

   ↳ hep-exnucl-exphysics.ins-det8 citations
2. 02*

   AI-Assisted Transport of Radioactive Ion Beams

   Sergio Lopez-Caceres🇺🇸 · Daniel Santiago-Gonzalez🇺🇸

   Beams of radioactive heavy ions allow researchers to study rare and unstable atomic nuclei, shedding light into the internal structure of exotic nuclei and on how chemical elements are formed in stars. However, the extraction and transport of radioactive beams rely on time-consuming expert-driven tuning methods, where hundreds of parameters are manually optimized. Here, we introduce a system that employs Artificial Intelligence (AI), specifically utilizing Bayesian Optimization, to assist in the transport process of radioactive beams. We apply our methodology to real-life scenarios showing advantages when compared with standard tuning methods. This AI-assisted approach can be extended to other radioactive beam facilities around the world to improve operational efficiency and enhance scientific output.

   ↳ physics.acc-phcs.AInucl-exPhys.Rev.Accel.Beams(2025)·2 citations
3. 03*

   Non Nucleonic Components in Short Nuclear Distances

   Misak M Sargsian

   One of the important features of nuclear forces is their strong repulsive nature at short ($\le 0.5-0.6$~Fm) distances which prevents atomic nuclei from collapsing, thus guarantying the stability for the visible matter. However the dynamical nature of this repulsion (referred to as a nuclear core) is as elusive as ever. We present the study of nuclear dynamics at extremely large internal momenta in the deuteron dominated by the nuclear core. It is demonstrated that the paradigm shift in the description of the deuteron consisting of proton and neutron to the description of the deuteron as a pseudo-vector composite system in which proton and neutron is observed in high energy electro-disintegration processes results in the emergence of a new structure. We demonstrate that this new structure can exist only if it emerges from pre-existing non-nucleonic component in the deuteron. The study of the dynamics of the predicted new structure is presented focusing on the question if it allows to understand the anomaly observed in the recent experiment at Jefferson Lab that probed deuteron structure at internal momenta above 800 MeV/c.

   ↳ nucl-thhep-phnucl-exPoS(2025)·0 citations
4. 04*

   Double shape quantum phase transitions in the SU3-IBM: new $\gamma$-soft phase and the shape phase transition from the new $\gamma$-soft phase to the prolate shape

   De-hao Zhao · Xiao-shen Kang · Li Gong · Ze-yu Yin · Tao Wang

   Shape quantum phase transition is an important topic in nuclear structure. In this paper, we begin to study the shape quantum phase transition in the SU3-IBM. In this new proposed model, spherical-like spectra was found to resolve the spherical nucleus puzzle, which is a new $\gamma$-soft rotational mode. In this paper, the shape phase transition along the new $\gamma$-soft line is first discussed, and then the neighbouring case at the prolate side is also studied. We find that double shape phase transitions occur along a single parameter path. The new $\gamma$-softness is really a shape phase and the shape phase transition from the new $\gamma$-soft phase to the prolate shape is found. The experimental support is also found and ${}^{108}$Pd may be the critical nucleus.

   ↳ nucl-thnucl-exNucl.Sci.Tech.(2026)·6 citations
5. 05*

   High-order fluctuations of temperature in hot QCD matter

   Jinhui Chen🇨🇳 · Wei-jie Fu🇨🇳 · Shi Yin🇩🇪 · Chunjian Zhang🇨🇳

   A new thermodynamic state function is introduced to describe the thermodynamics relevant for the mean transverse momentum fluctuations of charged particles in heavy-ion collisions, which allows us to compute the temperature fluctuations of different orders in hot quantum chromodynamics (QCD) matter for the first time. Consequently, it is found that the temperature fluctuations are suppressed remarkably as the system transitions from the hadron resonance gas (HRG) to the quark-gluon plasma (QGP) with increasing temperature or baryon chemical potential, alongside a negative skewness. This is attributed to the general fact that the heat capacity of QCD matter increases significantly in QGP in comparison to that in HRG. These predictions provide a candidate observable to discover the thermodynamic temperature fluctuations in upcoming heavy-ion collision experiments, which also paves a novel way to study QCD thermodynamics and QCD phase diagram through measurements of the mean transverse momentum fluctuations of charged particles.

   ↳ hep-phnucl-exnucl-thPRD(2026)·11 citations
6. 06*

   Broadband Optical Modulation and Control at Millikelvin Temperatures

   N. Tabassum🇺🇸 · T. Aralis🇺🇸 · J. Anczarski🇺🇸 · D. Baxter🇺🇸 · B. Cabrera🇺🇸 · R. Chapla🇺🇸 · N. Entin🇺🇸 · L. Hsu🇺🇸 · H.W. Magoon🇺🇸 · A. Nunez🇺🇸 · J.L. Ryan🇺🇸 · M. Salatino🇺🇸 and 8 other authors

   A universal experimental challenge when studying radiation effects on cryogenic devices is to precisely and accurately characterize the position-dependent device response very near the energy detection threshold. We have developed a compact cryogenic optical beam steering system that can be used to generate O({\mu}s) pulses of small numbers of photons over the energy range of 1.2 - 4.5eV at room temperature, and deliver those photons via fiber optic to any specified location on the surface of a detector operating at cryogenic temperatures. This new system will allow for robust calibration of any photon-sensitive detector, including supercondcting devices. The system can be used efficiently to explore the physics of target materials, quantify the position sensitivity of different sensor designs, measure phonon transport, and study the effects of quasiparticle poisoning on detector operation. We describe the design of this pulsed calibration method and present first results obtained with a second-generation system operated at room temperature and sub-Kelvin temperatures.

   ↳ physics.ins-detastro-ph.IMhep-exnucl-ex+1Rev.Sci.Instrum.(2025)·4 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.