Tue·May 12, 2020Tuesday·May 12, 2020

1. 01*

   A Search for the Quark-Hadron Phase Transition in pp collisions at $\sqrt{s}$ = 13 TeV using UrQMD model

   Swarnapratim Bhattacharyya🇮🇳

   Charged particle multiplicity fluctuations in pp collisions at $\sqrt{s}$ = 13 TeV have been studied by the method of scaled factorial moment for the minimum bias events generated by Ultra Relativistic Quantum Molecular Dynamics (UrQMD) model in the pseudo-rapidity ({\eta}), azimuthal angle ($\varphi$) and two dimensional anisotropic ($\eta$-$\varphi$) phase space. Strong intermittent type of fluctuations have been observed for the UrQMD simulated data. Systematic studies of intermittent fluctuations in terms of scaled factorial moments was utilized to extract the anomalous fractal dimension in the pseudo-rapidity ({\eta}), azimuthal angle ($\varphi$) and two dimensional anisotropic ($\eta$-$\varphi$) phase space. Search for the quark-hadron phase transition in the framework of Ginzburg-Landau theory of second-order phase transition by the analysis with the factorial moment method has also been performed.

   nucl-exnucl-th0 citations
2. 02*

   Spectroscopy of low spin states in 157Dy: Search for evidence of enhanced octupole correlations

   S. N. T. Majola🇿🇦 · R. A. Bark🇿🇦 · L. Bianco🇨🇦 · T. D. Bucher🇿🇦 · S. P. Bvumbi🇿🇦 · D. M. Cullen🇬🇧 · P. E. Garrett🇨🇦 · P. T. Greenlees🇫🇮 · D. Hartley🇺🇸 · J Hirvonen🇫🇮 · U. Jakobsson🇫🇮 · P. M. Jones🇿🇦 and 31 other authors

   Low-spin states of 157Dy have been studied using the JUROGAM II array, following the 155Gd ({\alpha}, 2n) reaction at a beam energy of 25 MeV. The level scheme of 157Dy has been expanded with four new bands. Rotational structures built on the [523]5/2- and [402]3/2+ neutron orbitals constitute new additions to the level scheme as do many of the inter- and intra-band transitions. This manuscript also reports the observation of cross I- to (I-1)- and I- to (I-1)+ E1 dipole transitions inter-linking structures built on the [523]5/2- (band 5) and [402]3/2+ (band 7) neutron orbitals. These interlacing band structures are interpreted as the bands of parity doublets with simplex quantum number s = -i related to possible octupole correlations.

   nucl-exnucl-thPRC(2019)·6 citations
3. 03*

   First candidates for {\gamma} vibrational bands built on the [505]11/2- neutron orbital in odd-A Dy isotopes

   S.N.T. Majola🇿🇦 · M.A. Sithole🇿🇦 · L. Mdletshe🇿🇦 · D. Hartley🇺🇸 · J. Timar🇭🇺 · B.M. Nyako🇭🇺 · J.M. Allmond🇺🇸 · R.A. Bark🇿🇦 · C. Beausang🇺🇸 · L. Bianco🇨🇦 · T.D. Bucher🇿🇦 · S.P. Bvumbi🇿🇦 and 58 other authors

   Rotational structures have been measured using the Jurogam II and GAMMASPHERE arrays at low spin following the 155Gd({\alpha},2n)157Dy and 148Nd(12C, 5n)155Dy reactions at 25 and 65 MeV, respectively. We report high-K bands, which are conjectured to be the first candidates of a K{\pi}= 2+ {\gamma} vibrational band, built on the [505]11/2- neutron orbital, in both odd-A 155, 157Dy isotopes. The coupling of the first excited K=0+ states or the so-called \b{eta} vibrational bands at 661 and 676 keV in 154Dy and 156Dy to the [505]11/2- orbital, to produce a K{\pi}=11/2- band, was not observed in both 155Dy and 157Dy, respectively. The implication of these findings on the interpretation of the first excited 0+ states in the core nuclei 154Dy and 156Dy are also discussed.

   nucl-exnucl-thPRC(2020)·5 citations
4. 04*

   Observation of $\gamma$-vibrations and alignments built on non-ground-state configurations in 156Dy

   S. N. T. Majola🇿🇦 · D. J. Hartley🇺🇸 · L.L. Riedinger🇺🇸 · J.F. Sharpey-Schafer🇿🇦 · J. M. Allmond🇺🇸 · C. Beausang🇺🇸 · M.P. Carpenter🇺🇸 · C.J. Chiara🇺🇸 · N. Cooper🇺🇸 · D. Curien🇫🇷 · B. J. P. Gall🇫🇷 · P.E. Garrett🇨🇦 and 16 other authors

   The exact nature of the lowest $K^{\pi }=2_{\gamma }^{+}$ rotational bands in all deformed nuclei remains obscure. Traditionally they are assumed to be collective vibrations of the nuclear shape in the $\gamma$ degree of freedom perpendicular to the nuclear symmetry axis. Very few such $\gamma$-bands have been traced past the usual back-bending rotational alignments of high-j nucleons. We have investigated the structure of positive-parity bands in the N=90 nucleus 156Dy, using the 148Nd(12C,4n)156Dy reaction at 65 MeV, observing the resulting $\gamma$-ray transitions with the Gammasphere array. The even- and odd-spin members of the $K^{\pi }=2_{\gamma }^{+}$ $\gamma$-band are observed to 32+ and 31+ respectively. This rotational band faithfully tracks the ground-state configuration to the highest spins. The members of a possible $\gamma$-vibration built on the aligned yrast S-band are observed to spins 28+ and 27+. An even-spin positive-parity band, observed to spin 24+, is a candidate for an aligned S-band built on the seniority-zero configuration of the $0_2^{+}$ state at 676 keV. The crossing of this band with the $0_2^{+}$ band is at $\hslash \omega$= 0.28(1) MeV and is consistent with the configuration of the $0_2^{+}$ band not producing any blocking of the monopole pairing.

   nucl-exnucl-thPRC(2015)·25 citations
5. 05*

   Timescales of quantum equilibration, dissipation and fluctuation in nuclear collisions

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

   Understanding the dynamics of equilibration processes in quantum systems as well as their interplay with dissipation and fluctuation is a major challenge in quantum many-body theory. The timescales of such processes are investigated in collisions of atomic nuclei using fully microscopic approaches. Results from time-dependent Hartree-Fock (TDHF) and time-dependent random-phase approximation (TDRPA) calculations are compared for 13 systems over a broad range of energies. The timescale for full mass equilibration ($\sim 2\times 10^{-20}$s) is found to be much larger than timescales for neutron-to-proton equilibration, kinetic energy and angular momentum dissipations which are on the order of $10^{-21}$s. Fluctuations of mass numbers in the fragments and correlations between their neutron and proton numbers build up within only a few $10^{-21}$s. This indicates that dissipation is basically not impacted by mass equilibration, but is mostly driven by the exchange of nucleons between the fragments.

   ↳ nucl-thnucl-exquant-phPRL(2020)·68 citations
6. 06*

   Non-perturbative Enhancement of Heavy Quark-Antiquark Pair Annihilation in the Quark-Gluon Plasma

   Xin Wu🇨🇳 · Min He🇨🇳

   The annihilation of heavy particles close to thermal equilibrium, which plays a prominent role in the chemical equilibration of heavy quarks in the Quark-Gluon Plasma (QGP) as well as in many classic dark matter scenarios, is reexamined. We derive a scattering amplitude that resums near-threshold attractive interaction of the annihilating particles in terms of the non-relativistic scattering $T$-matrix and Green's function, thereby capturing the pertinent Sommerfeld enhancement from both nonperturbative scattering state and bound state solutions. The derived formula is of such generality that it applies to arbitrary partial wave processes of two-particle annihilation, and enables to incorporate finite widths of the annihilating particles. In a screened potential model, the non-perturbative scattering amplitude is computed and the Sommerfeld enhancement is identified for heavy quark-antiquark annihilation in the QGP.

   ↳ hep-phnucl-exnucl-thPRD(2020)·0 citations
7. 07*

   A Fourier-Cumulant Analysis for Multiharmonic Flow Fluctuation

   Seyed Farid Taghavi🇩🇪

   The Fourier analysis of the final particle distribution followed by cumulant study of the Fourier coefficient event-by-event fluctuation is one of the main approaches for testing the collective evolution in the heavy-ion collision. Using a multidimensional generating function, we propose a method to extract any possible cumulant of multiharmonic flow fluctuations and classify them in terms of the order of cumulants and harmonics involved in them. In particular, we show that there are 33 distinct cumulants with orders $2,3,4,5$ and harmonics $2,3,4,5$. We compute the normalized version of these cumulants from hydrodynamic simulation for Pb--Pb collisions based on {\tt T${}_{\text{R}}$ENTo}+{\tt VISH2+1}+{\tt UrQMD}. We compare the simulation with those normalized cumulants that the LHC has measured and predict the unmeasured ones. Comparing the initial and final state fluctuation normalized cumulants, we compute the linear and nonlinear hydrodynamic response couplings. We finally introduce the genuine three-particle correlation function containing information of all third-order cumulants.

   ↳ nucl-thhep-phnucl-exEPJC(2021)·15 citations
8. 08*

   Excitation function of initial temperature of heavy flavor quarkonium emission source in high energy collisions

   Qi Wang🇨🇳 · Fu-Hu Liu🇨🇳

   The transverse momentum spectra of $J/\psi$, $\psi (2S)$, and ${\rm Y}(nS,n=1,2,3)$ produced in proton-proton ($p$+$p$), proton-antiproton ($p$+$\bar{p}$), proton-lead ($p$+Pb), gold-gold (Au+Au), and lead-lead (Pb+Pb) collisions over a wide energy range are analyzed by the (two-component) Erlang distribution, the Hagedorn function (the inverse power-law), and the Tsallis-Levy function. The initial temperature is obtained from the color string percolation model due to the fit by the (two-component) Erlang distribution in the framework of multisource thermal model. The excitation functions of some parameters such as the mean transverse momentum and initial temperature increase from dozens of GeV to above 10 TeV. The mean transverse momentum and initial temperature decrease (increase slightly or do not change obviously) with the increase of rapidity (centrality). Meanwhile, the mean transverse momentum of ${\rm Y}(nS,n=1,2,3)$ is larger than that of $J/\psi$ and $\psi (2S)$, and the initial temperature for ${\rm Y}(nS,n=1,2,3)$ emission is higher than that for $J/\psi$ and $\psi (2S)$ emission, which shows a mass-dependent behavior.

   ↳ hep-phhep-exnucl-exnucl-thAdv.High Energy Phys.(2020)·10 citations
9. 09*

   Laser-nucleus interactions in the sudden regime

   Sergei Kobzak · Hans A. Weidenmüller🇩🇪 · Adriana Pálffy🇩🇪

   The interaction between medium-weight nuclei and a strong zeptosecond laser pulse of MeV photons is investigated theoretically. Multiple absorption of photons competes with nuclear equilibration. We investigate the sudden regime. Here the rate of photon absorption is so strong that there is no time for the nucleus to fully equilibrate after each photon absorption process. We follow the temporal evolution of the system in terms of a set of rate equations. These account for dipole absorption and induced dipole emission, equilibration (modeled in terms of particle-hole states coupled by the residual nuclear interaction), and neutron decay (populating a chain of proton-rich nuclei). Our results are compared with earlier work addressing the adiabatic regime where equilibration is instantaneous. We predict the degree of excitation and the range of nuclei reached by neutron evaporation. These findings are relevant for planning future experiments.

   ↳ nucl-thnucl-exPRC(2021)·3 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.