We study the transverse momentum ( $p_T$ ) differential anisotropic flow and flow fluctuation in Pb+Pb collisions at $\sqrt{s_{_{NN}}}$ =5.02 TeV at the LHC. A (3+1)-dimensional CLVisc hydrodynamics framework with fluctuating TRENTO (or AMPT) initial conditions is utilized to simulate the space-time evolution of the quark-gluon plasma (QGP) medium. The effects of shear viscosity and the sub-nucleon structure on anisotropic flow and flow fluctuation are analyzed. Our result shows that shear viscosity tends to suppress both flow coefficients ( ${v_2\{2}\}$ , ${v_2\{4\}}$ , and ${\langle v_2\rangle}$ ) and flow fluctuation ( ${\sigma_{v_2}}$ ) owing to its smearing effect on local density fluctuation. The flow coefficients appear to be insensitive to the sub-nucleon structure, whereas the flow fluctuation ${\sigma_{v_2}}$ tends to be suppressed by the sub-nucleon structure in central collisions but enhanced in peripheral collisions. After taking into account the sub-nucleon structure effect, our numerical result can qualitatively describe the relative flow fluctuations ( ${v_2\{4\}/v_2\{2\}}$ , $F({v_2})$ ) measured by the ALICE Collaboration at the LHC. We further investigate the effects of shear viscosity, sub-nucleon structure, and initial condition model on the flow angle and flow magnitude decorrelations ( ${A_2^f}$ , ${M_2^f}$ ) using the four-particle correlation method. We find that the flow decorrelation effect is typically stronger in central collisions than in peripheral collisions. The flow angle decorrelation is found to be insensitive to the shear viscosity and sub-nucleon structure, whereas the flow magnitude decorrelation shows quite different behaviors when using the TRENTO and AMPT initial condition models. Our study sheds light on the anisotropic flow, transport properties, and initial structure of the QGP created in high-energy nuclear collisions.

China

Germany

Jie Zhu

Canada

Xiang-Yu Wu

Guang-You Qin

Anisotropic flow, flow fluctuation, and flow decorrelation in relativistic heavy-ion collisions: the roles of sub-nucleon structure and shear viscosity * Supported in part by the Natural Science Foundation of China (12225503, 11890710, 11890711, 11935007). Zhu Jie is supported in part by the China Scholarship Council (202306770009). Wu Xiang-Yu is supported in part by the National Science Foundation within the framework of the JETSCAPE collaboration (OAC-2004571) and in part by the Natural Sciences and Engineering Research Council of Canada. Some of the calculations were performed in the Nuclear Science Computing Center at Central China Normal University (NSC$^{3}$), Wuhan, Hubei, China.

The strange dibaryons <math><mrow><mi>p</mi><mi>Ω</mi></mrow></math> <math><mo>(</mo><mmultiscripts><mi>S</mi><mn>2</mn><none></none><mprescripts></mprescripts><none></none><mn>5</mn></mmultiscripts><mo>)</mo></math> and <math><mrow><mi>Ω</mi><mi>Ω</mi></mrow></math> <math><mo>(</mo><mmultiscripts><mi>S</mi><mn>0</mn><none></none><mprescripts></mprescripts><none></none><mn>1</mn></mmultiscripts><mo>)</mo></math> are likely bound, existing either in molecular states like the deuteron or as more exotic compact six-quark states. Here, we investigate the production of these two dibaryons in <math><mrow><mi>Pb</mi><mo>+</mo><mi>Pb</mi></mrow></math> collisions at <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>2.76</mn></mrow></math> TeV at the CERN Large Hadron Collider within a covariant coalescence model, which employs a blast-wave-like parametrization for the phase-space configurations of constituent particles at freeze-out. For the molecular states, the <math><mrow><mi>p</mi><mi>Ω</mi></mrow></math> and <math><mrow><mi>Ω</mi><mi>Ω</mi></mrow></math> are produced via <math><mrow><mi>p</mi><mtext>−</mtext><mi>Ω</mi></mrow></math> and <math><mrow><mi>Ω</mi><mtext>−</mtext><mi>Ω</mi></mrow></math> coalescence, respectively, while for the six-quark states, they are formed through <math><mrow><mi>u</mi><mi>u</mi><mi>d</mi><mi>s</mi><mi>s</mi><mi>s</mi></mrow></math> and <math><mrow><mi>s</mi><mi>s</mi><mi>s</mi><mi>s</mi><mi>s</mi><mi>s</mi></mrow></math> coalescence. We find that the yield ratios <math><mrow><msub><mi>N</mi><mrow><mi>p</mi><mi>Ω</mi></mrow></msub><mo>/</mo><msub><mi>N</mi><mi>Ω</mi></msub></mrow></math> and <math><mrow><msub><mi>N</mi><mrow><mi>Ω</mi><mi>Ω</mi></mrow></msub><mo>/</mo><msub><mi>N</mi><mi>Ω</mi></msub></mrow></math> have a distinct centrality dependence between the molecular and multiquark states, thus offering a promising way for distinguishing the two states. Our results suggest that the measurements of <math><mrow><mi>p</mi><mi>Ω</mi></mrow></math> and <math><mrow><mi>Ω</mi><mi>Ω</mi></mrow></math> production in relativistic heavy-ion collisions can shed light on their internal structures.

Jie Pu

Kai-Jia Sun

Chun-Wang Ma

Lie-Wen Chen

Probing the internal structures of <math><mrow><mi>p</mi><mi>Ω</mi></mrow></math> and <math><mrow><mi>Ω</mi><mi>Ω</mi></mrow></math> with their production at the Large Hadron Collider

Information entropy can be used for investigating the critical fluctuation phenomenon by describing multiplicity fluctuations in heavy-ion collisions. In this study, a multiphase transport (AMPT) model in the default version (AMPT-DEF) and with the string melting (AMPT-SM) were used as event generators to simulate the Au+Au reaction at different incident energies. Owing to the influence of the distribution bin number in extracting its information entropy, two methods, i.e., data binning and weighting factors, were proposed to correct the information entropy analysis. The comparison between information entropy and kurtosis also reflects the necessity to correct the information entropy analysis. The corrected information entropy of net-proton multiplicity was analyzed in central Au+Au collisions at <math><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>N</mi><mi>N</mi></mrow></msub></mrow></msqrt><mo>=</mo></math> 4.7, 6.4, 7.7, 8.8, 11.5, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 140, 170, and 200 GeV with the impact parameter <math><mi>b</mi><mo>=</mo><mn>3</mn></math> fm. The results indicated that the fluctuations of net-proton multiplicity were essentially identical at collision energies ranging from <math><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>N</mi><mi>N</mi></mrow></msub></mrow></msqrt><mo>=</mo></math> 4.7 GeV to <math><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>N</mi><mi>N</mi></mrow></msub></mrow></msqrt><mo>=</mo></math> 200 GeV in the same model. No critical fluctuation phenomenon was found in the central Au+Au collisions simulated using the AMPT models, similar to the case of the AMPT model, which does not have. Comparing the information entropy of AMPT-SM to AMPT-DEF, the effect of partonic phase leads to a bigger fluctuation, indicating that the corrected information entropy can be a useful probe to explore the phase transition. The mid-rapidity net-proton multiplicity information entropy was also calculated, and the results led to the same conclusion. The corrected information entropy may be useful for investigating critical fluctuations, which is important for exploring critical endpoint.

Yong-Bo Yu

Kai-Xuan Cheng

Yu-Ting Wang

Ya-Fei Guo

Exploring critical fluctuation phenomenon according to net-proton multiplicity information entropy in AMPT model

By performing global fits to inverse beta-decay (IBD) yield measurements from existing neutrino experiments based at highly <math><mrow><mmultiscripts><mrow><mi>U</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>235</mn></mrow></mmultiscripts></mrow></math>-enriched reactor cores and conventional low-enriched cores, we explore current direct bounds on neutrino production by the subdominant fission isotope <math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>241</mn></mrow></mmultiscripts></mrow></math>. For this nuclide, we determine an IBD yield of <math><mrow><msub><mrow><mi>σ</mi></mrow><mrow><mn>241</mn></mrow></msub><mo>=</mo><mn>8.16</mn><mo>±</mo><mn>3.47</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>cm</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>/</mo><mi>fission</mi></mrow></math>, a value <math><mrow><mo>(</mo><mn>135</mn><mo>±</mo><mn>58</mn><mo>)</mo><mo>%</mo></mrow></math> that of current beta-conversion models. This constraint is shown to derive from the nonlinear relationship between the burn-in of <math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>241</mn></mrow></mmultiscripts></mrow></math> and <math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>239</mn></mrow></mmultiscripts></mrow></math> in conventional reactor fuel. By considering new hypothetical neutrino measurements at highly-enriched, low-enriched, mixed-oxide, and fast reactor facilities, we investigate the feasible limits of future knowledge of IBD yields for <math><mrow><mmultiscripts><mrow><mi>U</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>235</mn></mrow></mmultiscripts></mrow></math>, <math><mrow><mmultiscripts><mrow><mi>U</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>238</mn></mrow></mmultiscripts></mrow></math>, <math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>239</mn></mrow></mmultiscripts></mrow></math>, <math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>241</mn></mrow></mmultiscripts></mrow></math>, and <math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>240</mn></mrow></mmultiscripts></mrow></math>. We find that the first direct measurement of the <math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>240</mn></mrow></mmultiscripts></mrow></math> IBD yield can be performed at plutonium-burning fast reactors, while a suite of correlated measurements at multiple reactor types can achieve precision in direct <math><mrow><mmultiscripts><mrow><mi>U</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>238</mn></mrow></mmultiscripts></mrow></math>, <math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>239</mn></mrow></mmultiscripts></mrow></math>, and <math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>241</mn></mrow></mmultiscripts></mrow></math> yield knowledge that meets or exceeds that of current theoretical predictions.

United States

Yoshi Fujikake

Bryce R. Littlejohn

Ohana B. Rodrigues

Pranava Teja Surukuchi

Exploring current constraints on antineutrino production by <math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>241</mn></mrow></mmultiscripts></mrow></math> and paths towards the precision reactor flux era

Accurate multiplicities of prompt fission neutrons emitted in neutron-induced fission on a large energy range are essential for fundamental and applied nuclear physics. Measuring them to high precision for radioactive fissioning nuclides remains, however, an experimental challenge. In this work, the average prompt-neutron multiplicity emitted in the $^{239}$Pu(<math><mi>n</mi><mo>,</mo><mi>f</mi></math>) reaction was extracted as a function of the incident-neutron energy, over the range 1-700 MeV, with a novel technique, which allowed to minimize and correct for the main sources of bias and thus achieve unprecedented precision.At low energies, our data validate for the first time the ENDF/B-VIII.0 nuclear data evaluation with an independent measurement and reduce the evaluated uncertainty by up to 60%. This work opens up the possibility of precisely measuring prompt fission neutron multiplicities on highly radioactive nuclei relevant for an essential component of energy production world-wide.

France

P. Marini

J. Taieb

D. Neudecker

G. Bélier

A. Chatillon

D. Etasse

B. Laurent

P. Morfouace

B. Morillon

M. Devlin

J.A. Gomez

R.C. Haight

K.J. Kelly

J.M. O'Donnell

Energy dependence of prompt fissions neutron multiplicity in the Pu( , ) Reaction

This Letter reports the first extraction of individual antineutrino spectra from <math><mrow><mmultiscripts><mrow><mi>U</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>235</mn></mrow></mmultiscripts></mrow></math> and <math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>239</mn></mrow></mmultiscripts></mrow></math> fission and an improved measurement of the prompt energy spectrum of reactor antineutrinos at Daya Bay. The analysis uses <math><mn>3.5</mn><mo>×</mo><msup><mn>10</mn><mn>6</mn></msup></math> inverse beta-decay candidates in four near antineutrino detectors in 1958 days. The individual antineutrino spectra of the two dominant isotopes, <math><mrow><mmultiscripts><mrow><mi>U</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>235</mn></mrow></mmultiscripts></mrow></math> and <math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>239</mn></mrow></mmultiscripts></mrow></math>, are extracted using the evolution of the prompt spectrum as a function of the isotope fission fractions. In the energy window of 4–6 MeV, a 7% (9%) excess of events is observed for the <math><mrow><mmultiscripts><mrow><mi>U</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>235</mn></mrow></mmultiscripts></mrow></math> (<math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>239</mn></mrow></mmultiscripts></mrow></math>) spectrum compared with the normalized Huber-Mueller model prediction. The significance of discrepancy is <math><mn>4.0</mn><mi>σ</mi></math> for <math><mrow><mmultiscripts><mrow><mi>U</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>235</mn></mrow></mmultiscripts></mrow></math> spectral shape compared with the Huber-Mueller model prediction. The shape of the measured inverse beta-decay prompt energy spectrum disagrees with the prediction of the Huber-Mueller model at <math><mn>5.3</mn><mi>σ</mi></math>. In the energy range of 4–6 MeV, a maximal local discrepancy of <math><mrow><mn>6.3</mn><mi>σ</mi></mrow></math> is observed.

D. Adey

F. P. An

A. B. Balantekin

H. R. Band

M. Bishai

Taiwan

S. Blyth

D. Cao

G. F. Cao

J. Cao

J. F. Chang

Y. Chang

H. S. Chen

S. M. Chen

Y. Chen

Y. X. Chen

J. Cheng

Z. K. Cheng

J. J. Cherwinka

Hong Kong

M. C. Chu

JINR

A. Chukanov

J. P. Cummings

N. Dash

F. S. Deng

Y. Y. Ding

M. V. Diwan

Czechia

T. Dohnal

J. Dove

M. Dvořák

D. A. Dwyer

M. Gonchar

G. H. Gong

H. Gong

W. Q. Gu

J. Y. Guo

L. Guo

X. H. Guo

Y. H. Guo

Z. Guo

R. W. Hackenburg

S. Hans

M. He

K. M. Heeger

Y. K. Heng

A. Higuera

Y. K. Hor

Y. B. Hsiung

B. Z. Hu

J. R. Hu

T. Hu

Z. J. Hu

H. X. Huang

X. T. Huang

Y. B. Huang

P. Huber

D. E. Jaffe

K. L. Jen

X. L. Ji

X. P. Ji

R. A. Johnson

D. Jones

L. Kang

S. H. Kettell

L. W. Koerner

S. Kohn

M. Kramer

T. J. Langford

J. Lee

J. H. C. Lee

R. T. Lei

R. Leitner

J. K. C. Leung

C. Li

F. Li

H. L. Li

Q. J. Li

S. Li

S. C. Li

S. J. Li

W. D. Li

X. N. Li

X. Q. Li

Y. F. Li

Z. B. Li

H. Liang

C. J. Lin

G. L. Lin

S. Lin

J. J. Ling

J. M. Link

L. Littenberg

B. R. Littlejohn

J. C. Liu

J. L. Liu

Y. Liu

Y. H. Liu

C. Lu

H. Q. Lu

J. S. Lu

K. B. Luk

X. B. Ma

Extraction of the <math><mrow><mmultiscripts><mrow><mi>U</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>235</mn></mrow></mmultiscripts></mrow></math> and <math><mrow><mmultiscripts><mrow><mi>Pu</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>239</mn></mrow></mmultiscripts></mrow></math> Antineutrino Spectra at Daya Bay

It is generally believed that the quark-hadron transition at small values of baryon chemical potentials <math><msub><mrow><mi>μ</mi></mrow><mrow><mi>B</mi></mrow></msub></math> is a crossover but changes to a first-order phase transition with an associated critical endpoint (CEP) as <math><msub><mrow><mi>μ</mi></mrow><mrow><mi>B</mi></mrow></msub></math> increases. Such a <math><msub><mrow><mi>μ</mi></mrow><mrow><mi>B</mi></mrow></msub></math>-dependent quark-hadron transition is expected to result in a double-peak structure in the collision energy dependence of the baryon density fluctuation in heavy-ion collisions with one at lower energy due to the spinodal instability during the first-order phase transition and another at higher energy due to the critical fluctuations in the vicinity of the CEP. By analyzing the data on the p, d and 3H yields in central heavy-ion collisions within the coalescence model for light nuclei production, we find that the relative neutron density fluctuation <math><mi>Δ</mi><msub><mrow><mi>ρ</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>=</mo><mo>〈</mo><msup><mrow><mo>(</mo><mi>δ</mi><msub><mrow><mi>ρ</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>)</mo></mrow><mrow><mn>2</mn></mrow></msup><mo>〉</mo><mo>/</mo><msup><mrow><mo>〈</mo><msub><mrow><mi>ρ</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>〉</mo></mrow><mrow><mn>2</mn></mrow></msup></math> at kinetic freeze-out indeed displays a clear peak at <math><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>N</mi><mi>N</mi></mrow></msub></mrow></msqrt><mo>=</mo><mn>8.8</mn><mspace width="0.25em"></mspace><mtext>GeV</mtext></math> and a possible strong re-enhancement at <math><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>N</mi><mi>N</mi></mrow></msub></mrow></msqrt><mo>=</mo><mn>4.86</mn><mspace width="0.25em"></mspace><mtext>GeV</mtext></math>. Our findings thus provide a strong support for the existence of a first-order phase transition at large <math><msub><mrow><mi>μ</mi></mrow><mrow><mi>B</mi></mrow></msub></math> and its critical endpoint at a smaller <math><msub><mrow><mi>μ</mi></mrow><mrow><mi>B</mi></mrow></msub></math> in the temperature versus baryon chemical potential plane of the QCD phase diagram.

Che Ming Ko

Zhangbu Xu

Light nuclei production as a probe of the QCD phase diagram

The experimental determination of the total excitation energy, the total kinetic energy, and the evaporation neutron multiplicity of fully identified fragments produced in transfer-induced fission of 240 Pu, combined with reasonable assumptions, permits to extract the intrinsic and collective excitation energy of the fragments as a function of their atomic number, along with their quadrupole deformation and their distance at scission. The results show that the deformation increases with the atomic number, Z , except for a local maximum around Z=44 and a minimum around Z=50 , associated with the effect of deformed shells at Z∼44 , N∼64 , and spherical shells in 132 Sn, respectively. The distance between the fragments also shows a minimum around Z1=44 , Z2=50 , suggesting a mechanism that links the effect of structure with the length of the neck at scission.

Spain

Manuel Caamaño

Fanny Farget

Energy balance and deformation at scission in 240 Pu fission

For a system of current interest (composed of charm, anticharm and a pair of light quarks), we show trends in phenomenological implications of QCD-based improvements to a simple quark model treatment. We employ a resonating group method to render this difficult four-body problem manageable. We use a quadratic confinement so as to be able to improve beyond the Born approximation. We report the position of the pole corresponding to the D̄0D0* molecule for the best fit of a model parameter to the relevant QCD simulations. We point out the interesting possibility that the pole can be shifted to 3872 MeV by introducing another parameter I0 that changes the strength of the interaction in this one component of X(3872). The revised value of this second parameter can guide future trends in modeling of the full exotic meson X(3872). We also report the changes with I0 in the S-wave spin averaged cross sections for D̄0D0* ⟶ ωJ/ψ and D̄0D0* ⟶ ρJ/ψ. These cross sections are important regarding the study of QGP (quark gluon plasma).

Pakistan

M. Imran Jamil

Bilal Masud

Faisal Akram

S.M. Sohail Gilani

D̄0D0* (D0D̄0*) system in QCD-improved many body potentialBM and FA acknowledge the support of PU research (D/605/Est.I Sr. 20 Project 2014-15, D/34/Est.1 Sr. 109 Project 2013-14), SG is thankful to the Higher Education Commission (HEC) of Pakistan for its financial support through (17-5-4(Ps3-128) HEC/Sch/2006)