Nuclear Theory·nucl-th

Tuesday·September 10, 2019

15 papers—9 primary·6 cross-listed

10
Aspects of isentropic trajectories in chiral effective models
Rainer Stiele🇮🇹 · Wanda Maria Alberico🇮🇹 · Andrea Beraudo🇮🇹 · Renan Câmara Pereira🇵🇹 · Pedro Costa🇵🇹 · Hubert Hansen🇫🇷 · Mario Motta🇮🇹
The evolution of the fireball in heavy ion collisions is an isentropic process, meaning that it follows a trajectory of constant entropy per baryon in the phase diagram of the strong interaction. Responsible for the collective acceleration of the fireball is the speed of sound of the system, while fluctuations of conserved charges are encoded in quark-number susceptibilities: together, they leave their imprint in final observables. Here, this isentropic evolution will be analysed within chiral effective models that account for both chiral and center symmetry breaking, two central aspects of QCD. Our discussion focusses on the impact on the isentropic trajectories of the treatment of high-momentum modes, of the meson contribution to thermodynamics and of the number of quark flavours.
↳ hep-phnucl-thJ.Phys.Conf.Ser.(2020)·0 citations
11
Yield ratio of neutrons to protons in $^{12} C (d, n)^{13}$ N and $^{12} C (d, p)^{13}$ C from 0.6 MeV to 3 MeV
W. J. Li🇨🇳 · Y. G. Ma🇨🇳 · G. Q. Zhang🇨🇳 · X. G. Deng🇨🇳 · M. R. Huang🇨🇳 · A. Bonasera🇺🇸 · D. Q. Fang🇨🇳 · J. Q. Cao🇨🇳 · Q. Deng🇨🇳 · Y. Q. Wang🇨🇳 · Q. T. Lei🇨🇳
The neutron yield in $^{12}$ C(d,n) $^{13}$ N and the proton yield in $^{12} C (d, p)^{13}$ C have been measured by deuteron beam from 0.6 MeV to 3 MeV which is delivered from a 4-MeV electro static accelerator bombarding on the thick carbon target. The neutrons are detected at $0°$ , $24°$ , $48°$ and the protons at $135°$ in the lab frame. The ratios of the neutron yield to the proton one have been calculated and can be used as an effective probe to pin down the resonances. The resonances are found at 1.4 MeV, 1.7 MeV, 2.5 MeV in $^{12} C (d, p)^{13}$ C and at 1.6 MeV, 2.7 MeV in $^{12}$ C(d,n) $^{13}$ N. This method provides a way to reduce the systematic uncertainty and helps to confirm more resonances in compound nuclei.
↳ nucl-exnucl-thNucl.Sci.Tech.(2019)·12 citations
12
Impact of Uncertainties in Astrophysical Reaction Rates on Nucleosynthesis in the $ν p$ Process
T. Rauscher · N. Nishimura · G. Cescutti · R. Hirschi · A. St.J. Murphy · C. Fröhlich
The $ν p$ process appears in proton-rich, hot matter which is expanding in a neutrino wind and may be realised in explosive environments such as core-collapse supernovae or in outflows from accretion disks. The impact of uncertainties in nuclear reaction cross sections on the finally produced abundances has been studied by applying Monte Carlo variation of all astrophysical reaction rates in a large reaction network. As the detailed astrophysical conditions of the $ν p$ process still are unknown, a parameter study was performed, with 23 trajectories covering a large range of entropies and $Y_{e}$ . The resulting abundance uncertainties are given for each trajectory. The $ν p$ process has been speculated to contribute to the light $p$ nuclides but it was not possible so far to reproduce the solar isotope ratios. It is found that it is possible to reproduce the solar $^{92}$ Mo/ $^{94}$ Mo abundance ratio within nuclear uncertainties, even within a single trajectory. The solar values of the abundances in the Kr-Sr region relative to the Mo region, however, cannot be achieved within a single trajectory. They may still be obtained from a weighted superposition of different trajectories, though, depending on the actual conditions in the production site. For a stronger constraint of the required conditions, it would be necessary to reduce the uncertainties in the 3 $α$ and $^{56}$ Ni(n,p) $^{56}$ Co rates at temperatures $T > 3$ GK.
↳ astro-ph.HEnucl-exnucl-thJPS Conf.Proc.(2020)·5 citations
13
Confinement of two-body systems and calculations in $d$ dimensions
E. Garrido · A.S. Jensen
A continuous transition for a system moving in a three-dimensional (3D) space to moving in a lower-dimensional space, 2D or 1D, can be made by means of an external squeezing potential. A squeeze along one direction gives rise to a 3D to 2D transition, whereas a simultaneous squeeze along two directions produces a 3D to 1D transition, without going through an intermediate 2D configuration. In the same way, for a system moving in a 2D space, a squeezing potential along one direction produces a 2D to 1D transition. In this work we investigate the equivalence between this kind of confinement procedure and calculations without an external field, but where the dimension $d$ is taken as a parameter that changes continuously from $d = 3$ to $d = 1$ . The practical case of an external harmonic oscillator squeezing potential acting on a two-body system is investigated in details. For the three transitions considered, 3D~ $\to$ ~2D, 2D~ $\to$ ~1D, and 3D~ $\to$ ~1D, a universal connection between the harmonic oscillator parameter and the dimension $d$ is found. This relation is well established for infinitely large 3D scattering lengths of the two-body potential for 3D~ $\to$ ~2D and 3D~ $\to$ ~1D transitions, and for infinitely large 2D scattering length for the 2D~ $\to$ ~1D case. For finite scattering lengths size corrections must be applied. The traditional wave functions for external squeezing potentials are shown to be uniquely related with the wave functions for specific non-integer dimension parameters, $d$ .
↳ physics.atm-clusnucl-thphysics.opticsquant-phPRResearch(2019)·9 citations
14
$J / ψ$ Production Dynamics: Event shape, Multiplicity and Rapidity dependence in Proton+Proton Collisions at LHC energies using PYTHIA8
Anisa Khatun🇮🇳 · Dhananjaya Thakur🇮🇳 · Suman Deb🇮🇳 · Raghunath Sahoo🇮🇳
High-multiplicity pp collisions at the Large Hadron Collider (LHC) energies have created special importance in view of the Underlying Event (UE) observables. The recent results of LHC, such as long range angular correlation, flow-like patterns, strangeness enhancement etc. in high multiplicity events are not yet completely understood. In the same direction, the understanding of multiplicity dependence of J/ $ψ$ production is highly necessary. Transverse spherocity, which is an event shape variable, helps to investigate the particle production by isolating the hard and the soft components. In the present study, we have investigated the multiplicity dependence of J/ $ψ$ production at mid-rapidity and forward rapidity through the transverse spherocity analysis and tried to understand the role of jets by separating the isotropic and jetty events from the minimum bias collisions. We have analyzed the J/ $ψ$ production at the mid-rapidity and forward rapidities via dielectron and dimuon channels, respectively using 4C tuned PYTHIA8 event generator. The analysis has been performed in two different center-of-mass energies: $s$ = 5.02 and 13 TeV, to see the energy dependence of jet contribution to the multiplicity dependence study of J/ $ψ$ production. Furthermore, we have studied the production dynamics through the dependence of thermodynamic parameters on event multiplicity and transverse spherocity.
↳ hep-phhep-exnucl-exnucl-thJ.Phys.G(2020)·15 citations
15
$Z_{c} (4430)$ , $Z_{c} (4200)$ , $Z_{1} (4050)$ , and $Z_{2} (4250)$ as triangle singularities
Satoshi X. Nakamura (University of Science and Technology of China)🇨🇳
$Z_{c} (4430)$ discovered in $B ˉ^{0} \to ψ (2 S) K^{-} π^{+}$ , $Z_{c} (4200)$ found in $B ˉ^{0} \to J / ψ K^{-} π^{+}$ , and $Z_{1} (4050)$ and $Z_{2} (4250)$ observed in $B ˉ^{0} \to χ_{c 1} K^{-} π^{+}$ are candidates of charged charmonium-like states. All surviving theoretical models interpreted these candidates as four-quark states, until we recently identified a compelling alternative. We discuss that kinematical singularities in triangle loop diagrams induce a resonance-like behavior that can consistently explain the properties (such as spin-parity, mass, width, and Argand plot) of $Z_{c} (4430)$ , $Z_{c} (4200)$ , $Z_{1} (4050)$ and $Z_{2} (4250)$ from experiments. In terms of the triangle singularities, we can also naturally understand interesting experimental findings such as the appearance (absence) of $Z_{c} (4200)$ ( $Z_{c} (4430)$ )-like contribution in $Λ_{b}^{0} \to J / ψ p π^{-}$ , and the highly asymmetric shape of the spectrum bump for $Z_{1} (4050)$ ; the other theoretical models have not successfully addressed these points. Although Pakhlov et al. proposed another triangle diagram to generate a $Z_{c} (4430)$ -like bump, we argue that this scenario is very unlikely.
↳ hep-phhep-exnucl-thAIP Conf.Proc.(2020)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE

Aspects of isentropic trajectories in chiral effective models

Yield ratio of neutrons to protons in 12C(d,n)13N and 12C(d,p)13C from 0.6 MeV to 3 MeV

Impact of Uncertainties in Astrophysical Reaction Rates on Nucleosynthesis in the νp Process

Confinement of two-body systems and calculations in d dimensions

J/ψ Production Dynamics: Event shape, Multiplicity and Rapidity dependence in Proton+Proton Collisions at LHC energies using PYTHIA8

Zc​(4430), Zc​(4200), Z1​(4050), and Z2​(4250) as triangle singularities

Affiliations

Yield ratio of neutrons to protons in $^{12} C (d, n)^{13}$ N and $^{12} C (d, p)^{13}$ C from 0.6 MeV to 3 MeV

Impact of Uncertainties in Astrophysical Reaction Rates on Nucleosynthesis in the $ν p$ Process

Confinement of two-body systems and calculations in $d$ dimensions

$J / ψ$ Production Dynamics: Event shape, Multiplicity and Rapidity dependence in Proton+Proton Collisions at LHC energies using PYTHIA8

$Z_{c} (4430)$ , $Z_{c} (4200)$ , $Z_{1} (4050)$ , and $Z_{2} (4250)$ as triangle singularities