Fri·Apr 8, 2022Friday·April 8, 2022

1. 01*

   Muonic X-Ray Measurement for the Nuclear Charge Distribution: the Case of Stable Palladium Isotopes

   T. Y. Saito🇯🇵 · M. Niikura🇯🇵 · T. Matsuzaki🇯🇵 · H. Sakurai🇯🇵 · M. Igashira · H. Imao · K. Ishida🇯🇵 · T. Katabuchi · Y. Kawashima🇯🇵 · M. K. Kubo · Y. Miyake · Y. Mori🇯🇵 and 7 other authors

   Background: The nuclear charge radius and distribution are the most fundamental quantities of the atomic nucleus. From the muonic transition energies, the absolute charge radius has been experimentally obtained, while there have been no established methods to discuss the distribution. Purpose: The muonic transition energies for five palladium isotopes with the mass number $A=104$, $105$, $106$, $108$ and $110$ were measured. The procedure to deduce the charge radii and the method to discuss the charge distribution from the muonic transition energies are proposed. Method: The experiment was performed at the MuSIC-M1 beamline at Research Center for Nuclear Physics, Osaka University. A continuous muon beam impinged on the enriched palladium targets. Muonic X rays were measured by high-purity germanium detectors. Results: The muonic transition energies up to $4f$-$3d$ transitions were determined for five palladium isotopes. Discussion and conclusion: The root-mean-square charge radii are deduced assuming the two-parameter Fermi distribution. The charge distribution of the nucleus is discussed employing the Barrett model. The muonic transition energies of the $3d$-$2p$ transitions are crucial to discuss both the charge radius and the charge distribution.

   nucl-exPRC(2025)·20 citations
2. 02*

   Global polarization and spin alignment measurements

   Takafumi Niida🇯🇵

   Recent experimental results on global polarization of hyperons and spin alignment of vector mesons in heavy-ion collisions are reviewed, especially in context of the energy dependence and particle species dependence. New results on local polarization along the beam direction at the LHC are discussed with previous measurements at RHIC. Future outlook of these measurements and possible future directions for better understanding of local vorticity field are briefly discussed.

   nucl-exEPJ Web Conf.(2022)·0 citations
3. 03*

   Single Inclusive Jet Production in $pA$ Collisions at NLO in the small-$x$ regime

   Hao-yu Liu🇨🇳 · Kexin Xie🇨🇳 · Zhongbo Kang🇺🇸 · Xiaohui Liu🇨🇳

   We present the first complete NLO prediction with full jet algorithm implementation for the single inclusive jet production in $pA$ collisions within the CGC effective theory. Our prediction is fully differential over the final state physical kinematics, which allows the implementation of any IR safe observable including the jet clustering procedure. The NLO calculation is organized with the aid of the power counting proposed in [1] which gives rise to the novel soft contributions in the CGC factorization. We achieve the fully-differential calculation by constructing suitable subtraction terms to handle the singularities in the real corrections. The subtraction contributions can be exactly integrated analytically. We present the NLO cross section with the jets constructed using the anti-$k_T$ algorithm. The NLO calculation demonstrates explicitly the validity of the CGC factorization in jet production. Furthermore, as a byproduct of the subtraction method, we also derive the fully analytic cross section for the forward jet production in the small-$R$ limit. We show that in the small-$R$ approximation, the forward jet cross section can be factorized into a semi-hard cross section that produces a parton and the semi-inclusive jet functions. We argue that this feature holds for generic jet production and jet substructure observables in the CGC framework. Last, we show numerical analyses of the derived formula to validate our calculations. We justify when the small-$R$ approximation is appropriate. Like forward hadron production, the obtained NLO result also exhibits the negativity of the cross section in the large jet transverse regime, which signals the need for the threshold resummation. A sketch of the threshold resummation in the CGC framework is presented based on the multiple emission picture.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2022)·28 citations
4. 04*

   Radiative hadronization: Photon emission at hadronization from quark-gluon plasma

   Hirotsugu Fujii🇯🇵 · Kazunori Itakura🇯🇵 · Katsunori Miyachi🇯🇵 · Chiho Nonaka🇯🇵

   We investigate photon emission at the hadronization stage from a quark-gluon plasma created in relativistic heavy-ion collisions. A recombination-model picture suggests that a quark and an antiquark bind into a meson state in hadronization, which would apparently violate the energy conservation if there is nothing else involved. We consider here a hadronization process where the recombination accompanies a photon emission. This is an analog of the "{\it radiative recombination}" known in plasma physics, such as $e^{-}+p^{+}\to {\mathrm{H}}^0+\gamma$, which occurs when an electromagnetic plasma goes back to a neutral atomic gas. The "radiative hadronization" picture will bring about (i) an enhancement of the photon yield, (ii) significant flow of photons similar to that of hadrons, and (iii) the photon transverse momentum ($p_T$) distribution with a thermal profile whose effective temperature is given by blue-shifted temperature of quarks. Here as a simplest and phenomenological realization of the radiative hadronization, we modify the recombination model to involve a photon emission and evaluate the photon yield with this modified model. Adding this contribution to the direct photon yield along with thermal photon contribution calculated with a hydrodynamic model and a parametrized contribution of prompt photons, we study the $p_T$ spectrum and elliptic flow of the photons produced in heavy-ion collisions at RHIC and LHC energies.

   ↳ nucl-thhep-phnucl-exPRC(2022)·15 citations
5. 05*

   Identification of radiopure tungsten for low background applications

   J. Hakenmüller (1)🇩🇪 · W. Maneschg (1) ((1) Max-Planck-Institut für Kernphysik, Heidelberg, Germany)🇩🇪

   In this article we explore the availability of radiopure tungsten and its potential as high density shield material for low background applications. For compact shield designs, conventionally, lead is used. Metallic tungsten and tungsten pseudo-alloys reach higher densities up to 19.3 gcm${}^{-3}$ and do not exhibit a significant ${}^{210}$Pb activity, which is a typical intrinsic contamination in lead. Within several $\gamma$-ray screening campaigns we were able to identify tungsten samples with activities similar or better than 1 mBqkg${}^{-1}$ in ${}^{232}$Th, ${}^{40}$K, ${}^{60}$Co and the second part of the ${}^{238}$U decay chain. In cooperation with a manufacturer we further reduced a persisting contamination in the first part of the ${}^{238}$U decay chain by a factor of $\sim$2.5 down to (305$\pm$30) mBqkg${}^{-1}$. With Monte Carlo simulations, the construction of prototype tungsten-based setups and dedicated measurements, the shield capability of tungsten in comparison to lead was extensively studied. Specifically, the impact of cosmogenic radiation on the background at shallow depth was investigated. We showed that a 6-40% reduction (depending on the exact shield configuration) in the muon-induced neutron fluence is achievable by replacing lead with an equivalent amount of tungsten regarding the suppression of external $\gamma$-radiation. Overall, many benefits using tungsten especially for low energy applications below a few 100 keV are found. The pseudo-tungsten alloy presented in this work paves the way for several applications especially regarding background suppression in particle and astroparticle physics search programs.

   ↳ physics.ins-dethep-exnucl-exJ.Phys.G(2022)·2 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.