Mon·Nov 4, 2024Monday·November 4, 2024

1. 01*

   Recent results and upgrade of the ALICE muon spectrometer

   Luca Quaglia · ALICE collaboration

   The ALICE experiment at the CERN Large Hadron Collider (LHC) is a multi-purpose particle detector, mainly focused on the study of quark-gluon plasma (QGP) in heavy-ion collisions. In the forward rapidity region, 2.5 $<$ y $<$ 4, ALICE is equipped with a muon spectrometer (MS), which allows to study quarkonia and open heavy-flavor particles, both key probes to investigate QGP properties. Although in LHC Run 1 and 2 many important results were achieved, the front absorber of the MS represented a limit to the physics program, due to the multiple scattering and energy loss in the material. To assess this limitation, a new forward vertex tracker (Muon Forward Tracker, MFT) was installed between the inner tracking system (ITS) and the front absorber. This has enhanced the MS physics performance, enabling the separation of prompt/non-prompt charmonium production at forward rapidity. It will also allow one to reduce the combinatorial background from semi-leptonic decays of kaons and pions. Finally, it will greatly improve the invariant-mass resolution of the low-mass dimuon pairs. Moreover, during the ongoing LHC Run 3, the rate of Pb\textendash{}Pb collisions has been increased from 10~kHz (in Run 2) up to 50~kHz, allowing to collect a data sample about 5 times larger than the one recorded in Run 2. This contribution will provide a brief overview of the MS upgrades and it will focus on the expected physics performance during the LHC Run 3. Some of the preliminary results already obtained will also be shown.

   nucl-exhep-exphysics.ins-detNucl.Part.Phys.Proc.(2024)·2 citations
2. 02*

   Isospin breaking in the ${}^{71}$Kr and ${}^{71}$Br mirror system

   A. Algora🇪🇸 · A. Vitéz-Sveiczer🇭🇺 · A. Poves🇪🇸 · G. G. Kiss🇭🇺 · B. Rubio🇪🇸 · G. de Angelis🇮🇹 · F. Recchia🇮🇹 · S. Nishimura🇯🇵 · T. Rodriguez🇪🇸 · P. Sarriguren🇪🇸 · J. Agramunt🇪🇸 · V. Guadilla🇪🇸 and 56 other authors

   Isospin symmetry is a fundamental concept in nuclear physics. Even though isospin symmetry is partially broken, it holds approximately for most nuclear systems, which makes exceptions very interesting from the nuclear structure perspective. In this framework, it is expected that the spins and parities of the ground states of mirror nuclei should be the same, in particular for the simplest systems where a proton is exchanged with a neutron or vice versa. In this work, we present evidence that this assumption is broken in the mirror pair ${}^{71}$Br and ${}^{71}$Kr system. Our conclusions are based on a high-statistics $\beta$ decay study of ${}^{71}$Kr and on state-of-the-art shell model calculations. In our work, we also found evidence of a new state in ${}^{70}$Se, populated in the $\beta$-delayed proton emission process which can be interpreted as the long sought coexisting 0${}^{+}$ state.

   nucl-exnucl-thPRL(2025)·6 citations
3. 03*

   Estimate of the $S$-wave $D^{\ast }K$ scattering length in the isospin-0 channel from Belle and LHCb data

   N. N. Achasov🇷🇺 · G. N. Shestakov🇷🇺

   It is shown that the Belle and LHCb data on the interference of the amplitudes of the $S$ and $D$ partial waves in the decays $D_{s1}(2536{)}^{+}\to D^{\ast +}{K}_S^0$ and $D_{s1}(2536{)}^{-}\to {\bar{D}}^{\ast 0}{K}^{-}$ allow us to obtain an estimate of the $S$-wave $D^{\ast }K$ scattering length in the channel with isospin $I=0$: $|a_{D^{\ast }K}^{(0)}|=(0.94\pm 0.06)$ fm. The possibility of explaining the found value by the contribution of the $D_{s1}(2460)$ resonance is discussed. The decay of $B_{s1}(5830)\to B^{\ast }\bar{K}$ is also briefly discussed.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2025)·0 citations
4. 04*

   Unlocking "imprints" of conserved charges in the initial state of heavy-ion collisions

   Fernando G. Gardim🇧🇷 · Dekrayat Almaalol🇺🇸 · Jordi Salinas San Martín🇺🇸 · Christopher Plumberg🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸

   Hydrodynamic approaches to modeling relativistic high-energy heavy-ion collisions are based on the conservation of energy and momentum. However, the medium formed in these collisions also carries additional conserved quantities, including baryon number (B), strangeness (S), and electric charge (Q). In this Letter, we propose a new set of anisotropic flow observables designed to be exclusively sensitive to the effects of conserved BSQ charge fluctuations, providing insight into the initial state. Using the recently developed hydrodynamic framework \iccing{}+\ccake{}, we show that these new observables provide a measurable effect of initial BSQ charge fluctuations (ranging up to $\sim$10\%), which can be tested by experiments.

   ↳ nucl-thhep-phnucl-ex4 citations
5. 05*

   Machine-Learning-Enabled Measurements of Astrophysical (p,n) Reactions with the SECAR Recoil Separator

   P. Tsintari · N. Dimitrakopoulos · R. Garg🇺🇸 · K. Hermansen🇺🇸 · C. Marshall🇺🇸 · F. Montes🇺🇸 · G. Perdikakis🇺🇸 · H. Schatz🇺🇸 · K. Setoodehnia🇺🇸 · H. Arora🇺🇸 · G.P.A. Berg🇺🇸 · R. Bhandari and 20 other authors

   The synthesis of heavy elements in supernovae is affected by low-energy (n,p) and (p,n) reactions on unstable nuclei, yet experimental data on such reaction rates are scarce. The SECAR (SEparator for CApture Reactions) recoil separator at FRIB (Facility for Rare Isotope Beams) was originally designed to measure astrophysical reactions that change the mass of a nucleus significantly. We used a novel approach that integrates machine learning with ion-optical simulations to find an ion-optical solution for the separator that enables the measurement of (p,n) reactions, despite the reaction leaving the mass of the nucleus nearly unchanged. A new measurement of the ${}^{58}$Fe(p,n)${}^{58}$Co reaction in inverse kinematics with a 3.66$\pm$0.12 MeV/nucleon ${}^{58}$Fe beam (corresponding to 3.69$\pm$0.12 MeV proton energy in normal kinematics) yielded a cross-section of 20.3$\pm$6.3 mb and served as a benchmark for the new technique demonstrating its effectiveness in achieving the required performance criteria. This novel approach marks a significant advancement in experimental nuclear astrophysics, as it paves the way for studying astrophysically important (p,n) reactions on unstable nuclei produced at FRIB.

   ↳ physics.ins-detnucl-exPRResearch(2025)·0 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.