Tue·Nov 23, 2021Tuesday·November 23, 2021

1. 01*

   Evidence for Nonlinear Gluon Effects in QCD and their $A$ Dependence at STAR

   STAR Collaboration: M. S. Abdallah · B. E. Aboona · J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · A. Aitbaev · I. Alekseev and 384 other authors

   The STAR Collaboration reports measurements of back-to-back azimuthal correlations of di-${\pi }^0$s produced at forward pseudorapidities ($2.6<\eta <4.0$) in $p$+$p$, $p+$Al, and $p+$Au collisions at a center-of-mass energy of 200 GeV. We observe a clear suppression of the correlated yields of back-to-back ${\pi }^0$ pairs in $p+$Al and $p+$Au collisions compared to the $p$+$p$ data. The observed suppression of back-to-back pairs as a function of transverse momentum suggests nonlinear gluon dynamics arising at high parton densities. The larger suppression found in $p+$Au relative to $p+$Al collisions exhibits a dependence of the saturation scale, $Q_s^2$, on the mass number, $A$. A linear scaling of the suppression with $A^{1/3}$ is observed with a slope of $-0.09$ $\pm$ $0.01$.

   nucl-exhep-exhep-thnucl-thPRL(2022)·41 citations
2. 02*

   Charge radii, moments and masses of mercury isotopes across the N = 126 shell closure

   T. Day Goodacre🇬🇧 · A.V. Afanasjev🇺🇸 · A.E. Barzakh🇷🇺 · L. Nies🇨🇭 · B.A. Marsh🇨🇭 · S. Sels🇨🇭 · U.C. Perera🇺🇸 · P. Ring🇩🇪 · F. Wienholtz🇨🇭 · A.N. Andreyev🇬🇧 · P. Van Duppen🇧🇪 · N.A. Althubiti🇬🇧 and 39 other authors

   Combining laser spectroscopy in a Versatile Arc Discharge and Laser Ion Source, with Penning-trap mass spectrometry at the CERN-ISOLDE facility, this work reports on mean-square charge radii of neutron-rich mercury isotopes across the $N=126$ shell closure, the electromagnetic moments of ${}^{207}$Hg and more precise mass values of ${}^{206-208}$Hg. The odd-even staggering (OES) of the mean square charge radii and the kink at $N=126$ are analyzed within the framework of covariant density functional theory (CDFT), with comparisons between different functionals to investigate the dependence of the results on the underlying single-particle structure. The observed features are defined predominantly in the particle-hole channel in CDFT, since both are present in the calculations without pairing. However, the magnitude of the kink is still affected by the occupation of the $1i_{11/2}$ and $2g_{9/2}$ orbitals with a dependence on the relative energies as well as pairing.

   nucl-exnucl-thPRC(2021)·20 citations
3. 03*

   Charge resolution in the isochronous mass spectrometry and the mass of ${}^{51}$Co

   Xu Zhou · Meng Wang · Yu-Hu Zhang · Hu-Shan Xu · You-Jin Yuan · Jian-Cheng Yang · Yu. A. Litvinov · S. A. Litvinov · Bo Mei · Xin-Liang Yan · Xing Xu · Peng Shuai and 16 other authors

   Isochronous mass spectrometry (IMS) of heavyion storage rings is a powerful tool for the mass measurements of short-lived nuclei. In IMS experiments, masses are determined through precision measurements of the revolution times of the ions stored in the ring. However, the revolution times cannot be resolved for particles with nearly the same mass-to-charge (m/q) ratios. To overcome this limitation and to extract the accurate revolution times for such pairs of ion species with very close m/q ratios, in our early work on particle identification, we analyzed the amplitudes of the timing signals from the detector based on the emission of secondary electrons. Here, the previous data analysis method is further improved by considering the signal amplitudes, detection efficiencies, and number of stored ions in the ring. A sensitive Z-dependent parameter is introduced in the data analysis, leading to a better resolution of ${}^{34}$Ar${}^{18+}$ and ${}^{51}$Co${}^{27+}$ with A/Z=17/9. The mean revolution times of ${}^{34}$Ar${}^{18+}$ and ${}^{51}$Co${}^{27+}$ are deduced, although their time difference is merely 1.8 ps. The uncorrected, overlapped peak of these ions has a full width at half maximum of 7.7 ps. The mass excess of ${}^{51}$Co was determined to be -27332(41) keV, which is in agreement with the previous value of -27342(48) keV.

   nucl-ex
4. 04*

   Measurement of the ${}^{136}$Xe two-neutrino double beta decay half-life via direct background subtraction in NEXT

   NEXT Collaboration: P. Novella🇪🇸 · M. Sorel🇪🇸 · A. Usón🇪🇸 · C. Adams🇺🇸 · H. Almazán🇩🇪 · V. Álvarez🇪🇸 · B. Aparicio🇪🇸 · A.I. Aranburu🇪🇸 · L. Arazi🇮🇱 · I.J. Arnquist🇺🇸 · S. Ayet🇩🇪 · C.D.R. Azevedo🇵🇹 and 97 other authors

   We report a measurement of the half-life of the ${}^{136}$Xe two-neutrino double beta decay performed with a novel direct background subtraction technique. The analysis relies on the data collected with the NEXT-White detector operated with ${}^{136}$Xe-enriched and ${}^{136}$Xe-depleted xenon, as well as on the topology of double-electron tracks. With a fiducial mass of only 3.5 kg of Xe, a half-life of $2.34_{-0.46}^{+0.80}{\text{(stat)}}_{-0.17}^{+0.30}\text{(sys)}\times 10^{21}\text{yr}$ is derived from the background-subtracted energy spectrum. The presented technique demonstrates the feasibility of unique background-model-independent neutrinoless double beta decay searches.

   nucl-exhep-exphysics.ins-detPRC(2022)·44 citations
5. 05*

   Modulation of pulse profile as a signal for phase transitions in a pulsar core

   Partha Bagchi🇨🇳 · Biswanath Layek🇮🇳 · Anjishnu Sarkar🇮🇳 · Ajit M. Srivastava🇮🇳

   We calculate detailed modification of pulses from a pulsar arising from the effects of phase transition induced density fluctuations on the pulsar moment of inertia. We represent general statistical density fluctuations using a simple model where the initial moment of inertia tensor of the pulsar (taken to be diagonal here) is assumed to get random additional contributions for each of its component which are taken to be Gaussian distributed with certain width characterized by the strength of density fluctuations $ϵ$. Using sample values of $ϵ$, (and the pulsar deformation parameter $\eta$) we numerically calculate detailed pulse modifications by solving Euler's equations for the rotational dynamics of the pulsar. We also give analytical estimates which can be used for arbitrary values of $ϵ$ and $\eta$. We show that there are very specific patterns in the perturbed pulses which are observable in terms of modulations of pulses over large time periods. In view of the fact that density fluctuations fade away eventually leading to a uniform phase in the interior of pulsar, the off-diagonal components of MI tensor also vanish eventually. Thus, the modification of pulses due to induced wobbling (from the off-diagonal MI components) will also die away eventually. This allows one to distinguish these transient pulse modulations from the effects of any wobbling originally present. Further, the decay of these modulations in time directly relates to relaxation of density fluctuations in the pulsar giving valuable information about the nature of phase transition occurring inside the pulsar.

   ↳ astro-ph.HEhep-phnucl-exnucl-thMNRAS(2022)·5 citations
6. 06*

   Dynamical synthesis of 4He in the scission phase of nuclear fission

   Z. X. Ren🇨🇳 · D. Vretenar🇭🇷 · T. Niksic🇭🇷 · P. W. Zhao🇨🇳 · J. Zhao🇨🇳 · J. Meng🇨🇳

   In the exothermic process of fission decay, an atomic nucleus splits into two or more independent fragments. Several aspects of nuclear fission are not properly understood, in particular the formation of the neck between the nascent fragments, and the subsequent mechanism of scission into two or more independent fragments. Using an implementation of time-dependent density functional theory, based on a relativistic energy density functional and including pairing correlations, we analyze the final phase of the process of induced fission of ${}^{240}$Pu, and show that the time-scale of neck formation coincides with the assembly of two $\alpha$-like clusters (less than 1 zs = 10${}^{-21}$ s). Because of its much larger binding energy, the dynamical synthesis of 4He in the neck predominates over other light clusters, e.g., ${}^3$H and ${}^6$He. At the instant of scission the neck ruptures exactly between the two $\alpha$-like clusters, which separate because of the Coulomb repulsion and are eventually absorbed by the two emerging fragments. The newly proposed mechanism of light charged clusters formation at scission provides a natural explanation of ternary fission.

   ↳ nucl-thnucl-exPRL(2022)·70 citations
7. 07*

   Upcgen: a Monte Carlo simulation program for dilepton pair production in ultra-peripheral collisions of heavy ions

   Nazar Burmasov🇷🇺 · Evgeny Kryshen🇷🇺 · Paul Buehler🇦🇹 · Roman Lavicka🇦🇹

   Ultra-peripheral collisions (UPCs) of heavy ions can be used as a clean environment to study two-photon induced interactions such as dilepton pair photoproduction. Recently, precise data on lepton pair production in UPCs were obtained by the ATLAS experiment at the LHC where significant deviations, of up to 20%, from available theoretical predictions were observed. In this work, we present a Monte Carlo event generator, Upcgen, that implements a refined treatment of the photon flux allowing us to improve the agreement with ATLAS data at large dilepton rapidities. Besides, the new generator offers a possibility to study photon polarization effects and set arbitrary values of the lepton anomalous magnetic moment that can be used in the future studies of tau g-2 via ditau production measurements in UPCs.

   ↳ hep-phnucl-exnucl-thComput.Phys.Commun.(2022)·27 citations
8. 08*

   Development of a low-background neutron detector array

   Y. T. Li🇨🇳 · W. P. Lin🇺🇸 · B. Gao🇨🇳 · H. Chen · H. Huang · Y. Huang🇨🇳 · T. Y. Jiao · K. A. Li · X. D. Tang · X. Y. Wang🇨🇳 · X. Fang · H. X. Huang🇨🇳 and 5 other authors

   A low-background neutron detector array was developed to measure the cross section of the ${}^{13}$C($\alpha$,n)${}^{16}$O reaction, which is the neutron source for the $s$-process in AGB stars, in the Gamow window ($E_{c.m.}$ = 190 $\pm$ 40 keV) at the China Jinping Underground Laboratory (CJPL). The detector array consists of 24 ${}^3$He proportional counters embedded in a polyethylene cube. Due to the deep underground location and a borated polyethylene shield around the detector array, a low background of 4.5(2)/hour was achieved. The ${}^{51}$V(p, n)${}^{51}$Cr reaction was used to determine the neutron detection efficiency of the array for neutrons with energy $E_n$ $<$ 1 MeV. Geant4 simulations, which were shown to well reproduce experimental results, were used to extrapolate the detection efficiency to higher energies for neutrons emitted in the ${}^{13}$C($\alpha$,n) ${}^{16}$O reaction. The theoretical angular distributions of the ${}^{13}$C($\alpha$,n)${}^{16}$O reaction were shown to be important in estimating the uncertainties of the detection efficiency.

   ↳ physics.ins-detnucl-exNucl.Sci.Tech.(2022)·11 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.