Thu·Jul 1, 2021Thursday·July 1, 2021

1. 01*

   Inclusive $\alpha$ Production for ${}^6$Li+${}^{51}$V System

   C. Joshi · H. Kumawat · V.V. Parkar · D. Dutta🇮🇳 · S.V. Suryanarayana · V. Jha🇮🇳 · R.K. Singh · N.L. Singh🇮🇳 · S. Kailas🇮🇳

   Measurement of angular distributions and energy spectra of $\alpha$ and deuterons through breakup, transfer and incomplete fusion processes to dis-entangle their relative contributions and to investigate relative importance of breakup-fusion compared to transfer. Inclusive $\alpha$ production cross-sections have been measured for ${}^6$Li + ${}^{51}$V system near Coulomb barrier energies. Theoretical calculations for estimation of various reaction channels contributing to $\alpha$ production have been performed with finite range coupled reaction method using \textsc{FRESCO} code. The cross-sections from non-capture breakup (NCBU) ($\alpha$ + \textit{d}) and 1\textit{n}, 1\textit{p}, and 1\textit{d} transfer channels, compound nuclear decay channel and incomplete fusion (ICF) leading to $\alpha$ production were estimated to get the cumulative production cross-sections. Contributions from breakup, transfer and incomplete fusion channels could reproduce the integral direct $\alpha$ production cross-sections and their angular distributions quite well. The direct $\alpha$ production cross-sections are in agreement with other targets. The $\alpha$ production cross-sections are higher compared to the deuteron production. Kinematic analysis of the energy spectra of $\alpha$ particles and deuterons suggest that $\alpha$ particle spectra is dominated by breakp-fusion and deuteron spectra have contribution of breakup and transfer reactions. A systematic study of direct $\alpha$ production with various targets follow a universal behavior on average but noticeable differences are observed for different targets. A ratio of $\alpha$ and deuteron yields for a wide mass range of targets shows a saturation above barrier and an increasing production of $\alpha$ particles relative to deuteron around Coulomb barrier.

   nucl-exnucl-thPRC(2022)·6 citations
2. 02*

   NEXO: Neutrinoless double beta decay search beyond $10^{28}$ year half-life sensitivity

   nEXO Collaboration: G. Adhikari🇺🇸 · S. Al Kharusi🇨🇦 · E. Angelico🇺🇸 · G. Anton🇩🇪 · I. J. Arnquist🇺🇸 · I. Badhrees🇨🇦 · J. Bane🇺🇸 · V. Belov🇷🇺 · E. P. Bernard🇺🇸 · T. Bhatta🇺🇸 · A. Bolotnikov🇺🇸 · P. A. Breur🇺🇸 and 148 other authors

   The nEXO neutrinoless double beta decay experiment is designed to use a time projection chamber and 5000 kg of isotopically enriched liquid xenon to search for the decay in ${}^{136}$Xe. Progress in the detector design, paired with higher fidelity in its simulation and an advanced data analysis, based on the one used for the final results of EXO-200, produce a sensitivity prediction that exceeds the half-life of $10^{28}$ years. Specifically, improvements have been made in the understanding of production of scintillation photons and charge as well as of their transport and reconstruction in the detector. The more detailed knowledge of the detector construction has been paired with more assays for trace radioactivity in different materials. In particular, the use of custom electroformed copper is now incorporated in the design, leading to a substantial reduction in backgrounds from the intrinsic radioactivity of detector materials. Furthermore, a number of assumptions from previous sensitivity projections have gained further support from interim work validating the nEXO experiment concept. Together these improvements and updates suggest that the nEXO experiment will reach a half-life sensitivity of $1.35\times 10^{28}$ yr at 90% confidence level in 10 years of data taking, covering the parameter space associated with the inverted neutrino mass ordering, along with a significant portion of the parameter space for the normal ordering scenario, for almost all nuclear matrix elements. The effects of backgrounds deviating from the nominal values used for the projections are also illustrated, concluding that the nEXO design is robust against a number of imperfections of the model.

   nucl-exphysics.ins-detJ.Phys.G(2022)·319 citations
3. 03*

   Ratio of photon anisotropic flow in relativistic heavy ion collisions

   Rupa Chatterjee🇮🇳 · Pingal Dasgupta🇨🇳

   The $p_T$ dependent elliptic and triangular flow parameters of direct photons are known to be dominated by thermal radiations. The non-thermal contributions dilute the photon anisotropic flow by adding extra weight factor in the $v_n$ calculation. The discrepancy between experimental photon anisotropic flow data and results from theoretical model calculations is not well understood even after significant developments in the model calculations as well as in the experimental analysis. We show that the ratio of photon $v_n$ can be a potential observable in this regard by minimizing the uncertainties arising due to the non-thermal contributions. We calculate the $v_2/v_3$ of photons as a function of $p_T$ from heavy ion collisions at RHIC and compare the results with available experimental data. The ratio does not change significantly $p_T$ in the region $p_T>2$ GeV. However, it rises towards smaller $p_T$ ($<2$ GeV) values. The ratio is found to be larger for peripheral collisions than for central collisions. In addition, it is found to be sensitive to the initial formation time and the final freeze-out temperature at different $p_T$ regions unlike the individual anisotropic flow parameters. We show that the photon $v_1/v_2$ and $v_1/v_3$ along with the $v_2/v_3$ results may help us constraining the initial conditions.

   ↳ nucl-thnucl-exPRC(2021)·10 citations
4. 04*

   Comparison of fission and quasi-fission modes

   C. Simenel🇦🇺 · P. McGlynn🇦🇺 · A.S. Umar🇺🇸 · K. Godbey🇺🇸

   Quantum shell effects are known to affect the formation of fragments in nuclear fission. Shell effects also affect quasi-fission reactions occurring in heavy-ion collisions. Systematic time-dependent Hartree-Fock simulations of 50Ca+176Yb collisions show that the mass equilibration between the fragments in quasi-fission is stopped when they reach similar properties to those in the asymmetric fission mode of the 226Th compound nucleus. Similar shell effects are then expected to determine the final repartition of nucleons between the nascent fragments in both mechanisms. Future experimental studies that could test these observations are discussed.

   ↳ nucl-thnucl-exPLB(2021)·31 citations
5. 05*

   Measurement of ion backflow fraction in GEM detectors

   A. Tripathy🇮🇳 · P. K Sahu · S. Swain🇮🇳 · S. Sahu🇲🇽

   A systematic study is performed to measure the ion backflow fraction of the GEM detectors. The effects of different voltage configurations and Ar/CO_2 gas mixtures, in ratios of 70:30, 80:20 and 90:10, on positive ion fraction are investigated in detail. Moreover, a comparative study is performed between single and quadruple GEM detectors.The ion current with detector effective gain is measured with various field configurations and with three proportions of gas mixtures. The ion backflow fraction for the GEM is substantially reduced with the lower drift field. A minimum ion backflow fraction of 18 % is achieved in the single GEM detector with Ar/CO_2 80:20 gas mixture, however, a minimum ion backflow fraction of 3.5 %, 3.0%, and 3.8 % are obtained for a drift field of 0.1kV/cm with Ar/CO_2 70:30, 80:20 and 90:10 gas mixtures, respectively for quadrupole GEM detector. Similar values of effective gain and ion backflow fraction have been found by calculating the current from pulse height spectrum method, obtained in the Multi Channel Analyser.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2021)·3 citations
6. 06*

   Inclusive and diffractive dijet photoproduction in ultraperipheral heavy ion collisions at the LHC

   V. Guzey (St. Petersburg, INP)🇷🇺 · M. Klasen (Munster U., ITP)🇩🇪

   We calculate the cross section of inclusive dijet photoproduction in ultraperipheral collisions (UPCs) of heavy ions at the CERN Large Hadron Collider using next-to-leading order perturbative QCD and demonstrate that it provides a good description of the ATLAS data. We study the role of this data in constraining nuclear parton distribution functions (nPDFs) using the Bayesian reweighting technique and find that it can reduce current uncertainties of nPDFs at small $x$ by a factor of 2. We also make predictions for diffractive dijet photoproduction in UPCs and examine its potential to shed light on the disputed mechanism of QCD factorization breaking in diffraction.

   ↳ hep-phhep-exnucl-exSciPost Phys.Proc.(2022)·0 citations
7. 07*

   Investigation of neutron transfer in ${}^7$Li+${}^{124}$Sn reaction

   V. V. Parkar🇮🇳 · A. Parmar · Prasanna M. · V. Jha🇮🇳 · S. Kailas🇮🇳

   The relative importance of neutron transfer and breakup process in reaction around Coulomb barrier energies have been studied for the ${}^7$Li+${}^{124}$Sn system. Coupled channel calculations have been performed to understand the one neutron stripping and pickup cross sections along with the breakup in the ${}^7$Li+${}^{124}$Sn system. The systematics of one and two neutron striping and pickup cross sections with ${}^7$Li projectile on several targets show an approximate universal behaviour that have been explained by a simple model. Complete reaction mechanism have been studied by comparing the reaction cross sections with cumulative cross sections of total fusion and one neutron transfer.

   ↳ nucl-thnucl-exPRC(2021)·14 citations
8. 08*

   Quantum dots as a probe of fundamental physics: Deviation from exponential decay law

   A.Yoshimi🇯🇵 · M.Tanaka🇯🇵 · M.Yoshimura🇯🇵

   We explore a possibility of measuring deviation from the exponential decay law in pure quantum systems. The power law behavior at late times of decay time profile is predicted in quantum mechanics, and has been experimentally attempted to detect, but with failures except a claim in an open system. It is found that electron tunneling from resonance state confined in man-made atoms, quantum dots, has a good chance of detecting the deviation and testing theoretical predictions. How initial unstable state is prepared influences greatly the time profile of decay law, and this can be used to set the onset time of the power law at earlier times. Comparison with similar process of nuclear alpha decay to discover the deviation is discussed, to explain why there exists a difficulty in this case.

   ↳ quant-phcond-mat.mes-hallhep-exhep-ph+2Eur.Phys.J.D(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.