Mon·Feb 26, 2024Monday·February 26, 2024

1. 01*

   Ultra-short lifetime isomer studies from photonuclear reactions using laser-driven ultra-intense {\gamma}-ray

   Di Wu🇨🇳 · Haoyang Lan🇨🇳 · Jiaxing Liu🇨🇳 · Huangang Lu🇺🇸 · Jianyao Zhang🇨🇳 · Jianfeng Lv🇨🇳 · Xuezhi Wu🇨🇳 · Hui Zhang🇨🇳 · Yadong Xia · Qiangyou He🇨🇳 · Jie Cai · Qianyi Ma🇨🇳 and 20 other authors

   Isomers, ubiquitous populations of relatively long-lived nuclear excited states, play a crucial role in nuclear physics. However, isomers with half-life times of several seconds or less barely had experimental cross section data due to the lack of a suitable measuring method. We report a method of online {\gamma} spectroscopy for ultra-short-lived isomers from photonuclear reactions using laser-driven ultra-intense {\gamma}-rays. The fastest time resolution can reach sub-ps level with {\gamma}-ray intensities >10^{19}/s ({\geqslant} 8 MeV). The ^{115}In({\gamma}, n)^{114m2}In reaction (T_{1/2} = 43.1 ms) was first measured in the high-energy region which shed light on the nuclear structure studies of In element. Simulations showed it would be an efficient way to study ^{229m}Th (T_{1/2} = 7 {\mu}s), which is believed to be the next generation of nuclear clock. This work offered a unique way of gaining insight into ultra-short lifetimes and promised an effective way to fill the gap in relevant experimental data.

   nucl-exphysics.plasm-ph2 citations
2. 02*

   Photo-nuclear cross sections on ${}^{197}$Au, an update on the gold standard

   J. Song🇪🇸 · D. Rotsch · J. A. Nolen · R. Gampa · R. M. de Kruijff · T. Brossard · C. R. Howell🇺🇸 · F. Krishichayan · Y. K. Wu🇨🇳 · S. Mikhailov · M. W. Ahmed · R. V. F. Janssens🇺🇸

   A method was developed for measuring photonuclear reactions concurrently at several discrete photon beam energies on a stack of different target materials via a single irradiation. Concentric ring targets of the materials (in order from front to back targets: Au, TiO${}_2$, Zn, Os, and Au) were irradiated at the High Intensity Gamma-ray Source (HI$\gamma$S). As a proof of principle, we report the result of the cross section measurements from the front Au target. The excitation functions of the ${}^{197}$Au($\gamma$,n)${}^{196}$Au and ${}^{197}$Au($\gamma$,3n)${}^{194}$Au reactions were determined in the incident photon energy range of 13-31 MeV using quasi-monoenergetic photon beams provided at HI$\gamma$S. The cross sections of the combined ground state (2${}^{-}$) and short-lived first isomeric state (m1, 5${}^{+}$), and of the second isomeric state (m2, 12${}^{-}$) in the ${}^{196}$Au production are obtained separately by subtracting the $\gamma$ rays from the internal conversion of the second isomeric state. The excitation function of the second isomeric state via the photon-induced reaction ${}^{197}$Au($\gamma$,n)${}^{196m2}$Au was measured for the first time. By using the activation method rather than direct neutron counting, the exclusive cross sections for the ($\gamma$,n) and ($\gamma$,3n) reactions were determined. Comparing the yields from the front and back gold targets validates our ability to simulate the effect of photon scattering in the target stack and provides a method for assessing the systematic uncertainty of our technique.

   nucl-exPRC(2024)·3 citations
3. 03*

   Modification of ${\chi }_{c1}$(3872) and $\psi$(2$S$) production in $p$Pb collisions at $\sqrt{s_{NN}}=8.16$ TeV

   LHCb collaboration: R. Aaij · A.S.W. Abdelmotteleb · C. Abellan Beteta · F. Abudinén · T. Ackernley · B. Adeva · M. Adinolfi · P. Adlarson · C. Agapopoulou · C.A. Aidala · Z. Ajaltouni · S. Akar and 1094 other authors

   The LHCb collaboration measures production of the exotic hadron ${\chi }_{c1}$(3872) in proton-nucleus collisions for the first time. Comparison with the charmonium state $\psi$(2$S$) suggests that the exotic ${\chi }_{c1}$(3872) experiences different dynamics in the nuclear medium than conventional hadrons, and comparison with data from proton-proton collisions indicates that the presence of the nucleus may modify ${\chi }_{c1}$(3872) production rates. This is the first measurement of the nuclear modification factor of an exotic hadron.

   ↳ hep-exnucl-exPRL(2024)·23 citations
4. 04*

   The Pixel Charging-up effect in Gas Micro-Pixel Detectors

   Difan Yi · Qian Liu · Hongbang Liu🇨🇳 · Fei Xie🇬🇧 · Huanbo Feng🇨🇳 · Lin Zhou · Zuke Feng · Yangheng Zheng🇨🇳

   This study investigates the charging-up effect on the Topmetal-II- chip in Gas Micro-Pixel Detectors(GMPD). It is found that this effect differs from the charging-up typically observed in gas detector multiplier devices and increases the relative gain of the detector. The research indicates that this effect originates from the accumulation of charges on the insulating layer of the chip's pixel surface. Iterative simulations using COMSOL and GARFIELD++ are employed to model the variation of detector relative gain with the charging-up effect, and a simple yet effective model is proposed, which aligns well with experimental data. The feasibility of validating the deposition of resistive materials and adjusting the local voltage distribution on the chip to suppress charging-up effects and enhance the relative gain is also verified.

   ↳ physics.ins-dethep-exnucl-ex1 citation
5. 05*

   Distinguishing fission-like events from deep-inelastic collisions

   Hong Yao · Cheng Li🇨🇦 · Houbing Zhou🇨🇳 · Ning Wang🇨🇳

   We propose two functions to distinguish fission-like events from quasi-elastic (QE) scattering and deep inelastic collisions (DIC), for a better analysis of the measured mass-total kinetic energy distributions of binary fragments formed in fusion-fission reactions. We note that the ratio of capture to DIC events evidently decreases with the decreasing of the depth of the capture pocket predicted from the Skyrme energy density functional, with which the capture pocket could be extracted from the measured mass-energy distributions. Together with the improved quantum molecular dynamics simulations, in which the typical contact time of the reaction partners is smaller than 200 fm/c for QE and is larger than 600 fm/c for fission-like events, we find that the ratio of capture to touching cross section systematically increases with the pocket depth.

   ↳ nucl-thnucl-exPRC(2024)·6 citations
6. 06*

   Detailed Report on the Measurement of the Positive Muon Anomalous Magnetic Moment to 0.20 ppm

   D. P. Aguillard (33)🇺🇸 · T. Albahri (30)🇬🇧 · D. Allspach (7)🇺🇸 · A. Anisenkov (4 and 38)🇷🇺 · K. Badgley (7)🇺🇸 · S. Baeßler (35 and 39)🇺🇸 · I. Bailey (17 and 40)🇬🇧 · L. Bailey (27)🇬🇧 · V. A. Baranov (15)🇷🇺 · E. Barlas-Yucel (28)🇺🇸 · T. Barrett (6)🇺🇸 · E. Barzi (7)🇺🇸 and 181 other authors

   We present details on a new measurement of the muon magnetic anomaly, $a_{\mu }=(g_{\mu }-2)/2$. The result is based on positive muon data taken at Fermilab's Muon Campus during the 2019 and 2020 accelerator runs. The measurement uses $3.1$ GeV$/c$ polarized muons stored in a $7.1$-m-radius storage ring with a $1.45$ T uniform magnetic field. The value of $a_{\mu }$ is determined from the measured difference between the muon spin precession frequency and its cyclotron frequency. This difference is normalized to the strength of the magnetic field, measured using Nuclear Magnetic Resonance (NMR). The ratio is then corrected for small contributions from beam motion, beam dispersion, and transient magnetic fields. We measure $a_{\mu }=116592057(25)\times 10^{-11}$ (0.21 ppm). This is the world's most precise measurement of this quantity and represents a factor of $2.2$ improvement over our previous result based on the 2018 dataset. In combination, the two datasets yield $a_{\mu }(\text{FNAL})=116592055(24)\times 10^{-11}$ (0.20 ppm). Combining this with the measurements from Brookhaven National Laboratory for both positive and negative muons, the new world average is $a_{\mu }$(exp) $=116592059(22)\times 10^{-11}$ (0.19 ppm).

   ↳ hep-exhep-phnucl-exPRD(2024)·113 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.