Wed·Apr 7, 2021Wednesday·April 7, 2021

1. 01*

   Measurement of relative isotopic yield distribution of even-even fission fragments from ${}^{235}$U($n_{th}$,$f$) following $\gamma$ ray spectroscopy

   Aniruddha Dey🇮🇳 · D.C. Biswas🇮🇳 · A. Chakraborty🇮🇳 · S. Mukhopadhyay🇮🇳 · A. K. Mondal🇮🇳 · L. S. Danu🇮🇳 · B. Mukherjee🇮🇳 · S. Garg🇨🇦 · B. Maheshwari🇮🇳 · A. K. Jain🇮🇳 · A. Blanc🇫🇷 · G. de France🇫🇷 and 8 other authors

   A detailed investigation on the relative isotopic distributions has been carried out for the first time in case of even-even correlated fission fragments for the ${}^{235}$U($n_{th}$,$f$) fission reaction. High-statistics data were obtained in a prompt $\gamma$ ray spectroscopy measurement during the EXILL campaign at ILL, Grenoble, France. The extensive off-line analysis of the coincidence data have been carried out using four different coincidence methods. Combining the results from 2-dimensional $\gamma -\gamma$ and 3-dimensional $\gamma -\gamma -\gamma$ coincidence analysis, a comprehensive picture of the relative isotopic yield distributions of the even-even neutron-rich fission fragments has emerged. The experimentally observed results have been substantiated by the theoretical calculations based on a novel approach of isospin conservation, and a reasonable agreement has been obtained. The calculations following the semi-empirical GEF model have also been carried out. The results from the GEF model calculations are found to be in fair agreement with the experimental results.

   nucl-exnucl-thPRC(2021)·12 citations
2. 02*

   UCN, the ultracold neutron source -- neutrons for particle physics

   Bernhard Lauss🇨🇭 · Bertrand Blau🇨🇭

   Ultracold neutrons provide a unique tool for the study of neutron properties. An overview is given of the ultracold neutron (UCN) source at PSI, which produces the highest UCN intensities to fundamental physics experiments by exploiting the high intensity proton beam in combination with the high UCN yield in solid deuterium at a temperature of 5K. We briefly list important fundamental physics results based on measurements with neutrons at PSI.

   nucl-exphysics.ins-detSciPost Phys.Proc.(2021)·26 citations
3. 03*

   Auxiliary Function Approach for Determining Symmetry Energy at Supra-saturation Densities

   Bao-Jun Cai🇨🇳 · Bao-An Li🇺🇸

   Nuclear symmetry energy $E_{\mathrm{sym}}(\rho )$ at density $\rho$ is normally expanded or simply parameterized as a function of $\chi =(\rho -{\rho }_0)/3{\rho }_0$ in the form of $E_{\mathrm{sym}}(\rho )\approx S+L\chi +2^{-1}{K}_{\mathrm{sym}}{\chi }^2+6^{-1}{J}_{\mathrm{sym}}{\chi }^3+\cdots$ using its magnitude $S$, slope $L$, curvature $K_{\mathrm{sym}}$ and skewness $J_{\mathrm{sym}}$ at the saturation density ${\rho }_0$ of nuclear matter. Much progress has been made in recent years in constraining especially the $S$ and $L$ parameters using various terrestrial experiments and astrophysical observations. However, such kind of expansions/parameterizations do not converge at supra-saturation densities where $\chi$ is not small enough, hindering an accurate determination of high-density $E_{\mathrm{sym}}(\rho )$ even if its characteristic parameters at ${\rho }_0$ are all well determined by experiments/observations. By expanding the $E_{\mathrm{sym}}(\rho )$ in terms of a properly chosen auxiliary function ${\Pi }_{\mathrm{sym}}(\chi ,{\Theta }_{\mathrm{sym}})$ with a parameter ${\Theta }_{\mathrm{sym}}$ fixed accurately by an experimental $E_{\mathrm{sym}}({\rho }_{\mathrm{r}})$ value at a reference density ${\rho }_{\mathrm{r}}$, we show that the shortcomings of the $\chi$-expansion can be completely removed or significantly reduced in determining the high-density behavior of $E_{\mathrm{sym}}(\rho )$. In particular, using two significantly different auxiliary functions, we show that the new approach effectively incorporates higher $\chi$-order contributions and converges to the same $E_{\mathrm{sym}}(\rho )$ much faster than the conventional $\chi$-expansion at densities $\lesssim 3{\rho }_0$. Several quantitative demonstrations using Monte Carlo simulations are given.

   ↳ nucl-thastro-ph.HEnucl-exPRC(2021)·15 citations
4. 04*

   Jet Transport Coefficient at the Large Hadron Collider Energies in a Color String Percolation Approach

   Aditya Nath Mishra🇭🇺 · Dushmanta Sahu🇮🇳 · Raghunath Sahoo🇮🇳

   Within the color string percolation model (CSPM), jet transport coefficient, $\hat{q}$, is calculated for various multiplicity classes in proton-proton and centrality classes in nucleus-nucleus collisions at the Large Hadron Collider energies for a better understanding of the matter formed in ultra-relativistic collisions. $\hat{q}$ is studied as a function of final state charged particle multiplicity (pseudorapiditydensity at midrapidity), initial state percolation temperature and energy density. The CSPM results are then compared with different theoretical calculations from the JET Collaboration those incorporate particle energy loss in the medium.

   ↳ hep-phhep-exhep-thnucl-ex+1Physics(2022)·11 citations
5. 05*

   $V_{ud}$ radiative corrections with lattice input

   Chien-Yeah Seng🇩🇪

   We will describe several pioneering efforts in the study of electromagnetic radiative corrections to semileptonic decay processes, with particular emphasis on the role of lattice QCD. These studies are essential for the precise extraction of the matrix element $V_{ud}$ from beta decays of pion, free neutron and $J^P=0^{+}$ nuclei, and are crucial to address several recently-emerged anomalies involving $V_{ud}$ and $V_{us}$, which may provide hints for physics beyond the Standard Model.

   ↳ hep-lathep-exhep-phnucl-ex+12 citations
6. 06*

   Empirical determination of the energy loss of heavy quarks in nuclear collisions at RHIC and LHC energies

   Somnath De🇮🇳 · Sudipan De🇮🇳 · Prashant Shukla🇮🇳

   Heavy quarks produced in the heavy ion collisions loose energy while propagting in the hot partonic matter which finally fragment to heavy ($D$ or $B$) mesons. The energy loss suffered by the heavy quarks is imprinted in the nuclear modification factor as a function of transverse momenta ($p_T$) of these heavy mesons. An alternate measure of in-medium energy loss comes through the effective shift in transverse momentum spectra of hadrons recorded in nucleus-nucleus collisions when it is compared to the same in proton-proton collisions. We start by parametrizing invariant momentum yields of heavy mesons in p+p collisions. The fit function from p+p collisions and measured nuclear modification factor in heavy ion collisions are then utilised to obtain the shift in the transeverse mass $\Delta m_T$ of heavy mesons produced at the RHIC and LHC experiments.The energy loss $\Delta m_T$ so obtained is found to scale with the transverse mass ($m_T$) of heavy mesons through a power law at different energies and centralities of collisions. We have also calculated using theoretical formalism, the total energy loss suffered by a charm quark in quark-gluon plasma produced in Pb~+~Pb collisions at the LHC energies. The evolution of the plasma is described by (2+1) dimensional longitudinal boost-invariant ideal hydrodynamics. It is found that the total energy loss of charm quarks scales with the transverse mass of charm quarks through a similar power law which supports our empirical analysis of energy loss.

   ↳ hep-phhep-exnucl-exnucl-thJ.Subatomic Part.Cosmol.(2025)·0 citations
7. 07*

   Spin/Parity Dependent Level Density

   Richard B. Firestone🇺🇸

   It is shown that the Constant Temperature (CT) model of nuclear level density is a direct consequence of a symmetrized Poisson distribution of nuclear level spacings. The standard CT model describing the total level density is shown to be fatally flawed due to discontinuities at the Yrast energies, the onset of new $J^{\pi }$ sequences, that disrupt the exponential formula and cause the back shift parameter to become nonphysically negative. A new CT-JPI level density model is proposed with a constant temperature and separate back shift parameters for each $J^{\pi }$ sequence. The CT-JPI model is also constrained to reproduce the spin distribution predicted by Ericson's spin distribution function at the neutron separation energy. A fitting procedure is described for determining the temperature $T$, back shifts $E_0(J^{\pi })$, and spin cutoff parameters ${\sigma }_c$ from nuclear structure and resonance data. The CT-JPI model is demonstrated to successfully predict the level densities for a wide range of spins and parities for 46 nuclear with Z=7-92. In variance with earlier predictions the spin cut-off parameters show no mass dependence and instead substantial variation at all mass regions.

   ↳ nucl-thnucl-ex1 citation

* 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.