Mon·May 5, 2025Monday·May 5, 2025

1. 01*

   Femtoscopic study of the proton-proton and proton-deuteron systems in heavy-ion collisions at the LHC

   ALICE Collaboration

   This work reports femtoscopic correlations of p$-$p ($\bar{\mathrm{p}}-\bar{\mathrm{p}}$) and p$-$d ($\bar{\mathrm{p}}-\bar{\mathrm{d}}$) pairs measured in Pb$-$Pb collisions at center-of-mass energy per nucleon $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV in the ALICE Collaboration. A fit to the measured proton-proton correlation functions allows one to extract the dependence of the nucleon femtoscopic radius of the particle-emitting source on the pair transverse mass ($m_{\text{T}}$) and on the average charge particle multiplicity $⟨{\text{dN}}_{\text{ch}}/\text{d}\eta {⟩}^{1/3}$ for three centrality intervals (0$-$10$\%$, 10$-$30$\%$, 30$-$50$\%$). In both cases, the expected power-law and linear scalings are observed, respectively. The measured p$-$d correlations can be described by both two- and three-body calculations, indicating that the femtoscopy observable is not sensitive to the short-distance features of the dynamics of the p$-$(p$-$n) system, due to the large inter-particle distances in Pb$-$Pb collisions at the LHC. Indeed, in this study, the minimum measured femtoscopic source sizes for protons and deuterons have a minimum value at $2.73_{-0.05}^{+0.05}$ and $3.10_{-0.86}^{+1.04}$ fm, respectively, for the 30$-$50$\%$ centrality collisions. Moreover, the $m_{\mathrm{T}}$-scaling obtained for the p$-$p and p$-$d systems is compatible within 1$\sigma$ of the uncertainties. These findings provide new input for fundamental studies on the production of light (anti)nuclei under extreme conditions.

   nucl-exhep-exPLB(2025)·17 citations
2. 02*

   Photoproduction and detection of ${\rho }^{\prime }\to {\pi }^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-}$ decays in ultra-peripheral collisions and at an electron-ion collider

   Neha Devi🇺🇸 · Minjung Kim🇺🇸 · Spencer R. Klein🇺🇸 · Janet Seger🇺🇸

   Vector meson photoproduction is an important probe of nuclear structure. Light vector mesons are most sensitive to low$-x$ structure, as long as they are not too light for perturbative QCD calculations. The ${\rho }^{\prime }$ is of interest as an intermediate mass state (between the $\rho$ and $J/\psi$) that is easier to detect than the $\varphi$. Using HERA data on proton targets, we make projections for lead/gold targets in UPCs at the Large Hadron Collider and RHIC, and for $ep$ and $eA$ collisions at a future Electron-Ion Collider (EIC). We compare the UPC projections with ALICE data, and constrain the branching ratio divided by the square of the photon-${\rho }^{\prime }$ coupling. The data prefer large couplings and small branching ratio, probably less than 25\%. The photon-meson coupling predicted by generalized vector meson dominance does not fit the data. The HERA $ep$ and ALICE UPC $e$Pb data exhibit very similar $4\pi$ mass spectra, indicating that, if the system is composed of two resonances, the products of their photon couplings with their four-pion branching ratios are similar. The predicted rates are high for both UPCs and the EIC. The ${\rho }^{\prime }\to {\pi }^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-}$ decay can be observed at the EIC with high efficiency. In $ep$ collisions at the highest energy, the forward B0 detector is needed to observe this channel down to the lowest achievable Bjorken$-x$ values.

   ↳ hep-phnucl-exPRC(2026)·4 citations
3. 03*

   Summary Report of the Physics Beyond Colliders Study at CERN

   R. Alemany Fernández🇨🇭 · M. Au🇨🇭 · G. Arduini🇨🇭 · L. Bandiera🇮🇹 · D. Banerjee🇨🇭 · H. Bartosik🇨🇭 · J. Bernhard🇨🇭 · D. Boer🇳🇱 · J. Boyd🇨🇭 · O. Brandt🇬🇧 · M. Brugger🇨🇭 · O. Buchmüller🇬🇧 and 71 other authors

   The Physics Beyond Collider (PBC) Study Group was initially mandated by the CERN Management to prepare the previous European Particle Physics Strategy Update for CERN projects other than the high-energy frontier colliders. The main findings were summarized in an PBC Summary Report submitted to the Strategy Update. Following the Update process, the PBC Study Group was confirmed on a permanent basis with an updated mandate taking into account the strategy recommendations. The Study Group is now in charge of supporting the proponents of new ideas to address the technical issues and physics motivation of the projects ahead of their review by the CERN Scientific Committees and decision by the Management. The present document updates the previous PBC summary report to inform the new ongoing European Particle Physics Strategy Update process, taking into account the evolution of the CERN and worldwide landscapes and the new projects under consideration within the Study Group.

   ↳ hep-exhep-phnucl-ex26 citations
4. 04*

   Deblurring fission fragment mass distributions

   Pierre Nzabahimana · Amy E. Lovell🇺🇸 · Patrick Talou🇺🇸

   Measurements of fission fragment mass distributions provide valuable insights into the properties of fissioning systems and the dynamics of the fission process. Pre-neutron emission distributions, essential for fission fragment evaporation codes like \cgmf{}, are extracted from distributions that are always measured after neutron emission, as the time scale of the emission of prompt fission neutrons is too short for direct measurement before the emission. However, obtaining accurate pre-neutron emission distributions requires methods that eliminate the effects of mass resolution and detector efficiency. We propose a deblurring technique based on the Richardson-Lucy (RL) algorithm, commonly used in optics for image restoration, to correct for these experimental effects. The RL algorithm uses the measured mass distributions and a transfer matrix to perform iterative deconvolution. The advantage of this method over others is that it does not assume any predefined shape such as a sum of Gaussians, as in \cgmf{}, for the distributions. In this paper, we apply the algorithm to the fission fragment mass distributions measured in the spontaneous fission of ${}^{252}$Cf to extract pre-neutron emission fission fragment mass distributions. The results from deblurring are then used as inputs to \cgmf{}, and we compare the \cgmf{} results obtained using deblurring inputs with the default \cgmf{} results.

   ↳ nucl-thnucl-exPRC(2025)·1 citation
5. 05*

   Higher order flow coefficients -- A Messenger of QCD medium formed in heavy-ion collisions at the Large Hadron Collider

   Suraj Prasad🇮🇳 · Aswathy Menon K R · Raghunath Sahoo🇮🇳 · Neelkamal Mallick🇫🇮

   Anisotropic flow and fluctuations are sensitive observables of the initial state effects in heavy ion collisions and are characterized by the medium properties and final state interactions. Using event-shape observables, one can constrain the probability distributions of anisotropic flow coefficients, thus reducing the linear and nonlinear contributions in the measured higher-order harmonics. In this paper, we use transverse spherocity as an event shape observable to study the flow coefficients and elliptic flow fluctuations. Transverse spherocity is found to have a strong correlation with elliptic flow and its fluctuations. We exploit this feature of transverse spherocity to remove the contribution to elliptic flow from higher-order harmonics. The study is performed in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV using a multi-phase transport model. The multi-particle Q-cumulant method estimates the anisotropic flow coefficients, which reduces the non-flow contributions. We observe a stronger system response to the flow coefficients for the events with smaller values of elliptic flow.

   ↳ nucl-thhep-exhep-phnucl-exPLB(2025)·7 citations
6. 06*

   Data-driven Approach for Interpolation of Sparse Data

   R.F. Ferguson🇬🇧 · D.G. Ireland🇬🇧 · B. McKinnon🇬🇧

   Studies of hadron resonances and their properties are limited by the accuracy and consistency of measured datasets, which can originate from many different experiments. We have used Gaussian Processes (GP) to build interpolated datasets, including quantification of uncertainties, so that data from different sources can be used in model fitting without the need for arbitrary weighting. GPs predict values and uncertainties of observables at any kinematic point. Bayesian inference is used to optimise the hyperparameters of the GP model. We demonstrate that the GP successfully interpolates data with quantified uncertainties by comparison with generated pseudodata. We also show that this methodology can be used to investigate the consistency of data from different sources. GPs provide a robust, model-independent method for interpolating typical datasets used in hadron resonance studies, removing the limitations of arbitrary weighting in sparse datasets.

   ↳ physics.data-annucl-exstat.ML2 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.