Wed·Jun 19, 2019Wednesday·June 19, 2019

1. 01*

   Prediction of possible exotic states in the $\eta \bar{K}{K}^{\ast }$ system

   Xu Zhang🇨🇳 · Ju-Jun Xie🇨🇳

   We investigate the $\eta \bar{K}{K}^{\ast }$ three body system in order to look for possible $I^G(J^{PC})=0^{+}(1^{-+})$ exotic states in the framework of the fixed center approximation to the Faddeev equation. We assume the scattering of $\eta$ on a clusterized system $\bar{K}{K}^{\ast }$, which is known to generate the $f_1(1285)$, or a $\bar{K}$ on a clusterized system $\eta K^{\ast }$, which is shown to generate the $K_1(1270)$. In the case of the $\eta$-$(\bar{K}{K}^{\ast }{)}_{f_1(1285)}$ scattering, we find evidence of a bound state $I^G(J^{PC})=0^{+}(1^{-+})$ below the $\eta f_1(1285)$ threshold with mass around 1700 MeV and width about 180 MeV. Considering the $\bar{K}$-$(\eta K^{\ast }{)}_{K_1(1270)}$ scattering, we obtain a bound state $I(J^P)=0(1^{-})$ just below the $\bar{K}{K}_1(1270)$ threshold with a mass around 1680 MeV and a width about 160 MeV.

   ↳ nucl-thhep-exhep-phnucl-exCPC(2020)·16 citations
2. 02*

   Higgs boson production in partonic and electromagnetic interactions with heavy ions

   David d'Enterria🇨🇭

   Higgs boson production in partonic and electromagnetic (photon-photon) interactions of light- and heavy-ions (A-A) at the LHC and future colliders is summarized. Parton-induced cross sections --including gluon-gluon, vector-boson fusion, and associated W, Z, t processes-- are computed at NNLO with MCFM 8.0 using nuclear parton distribution functions. Photon-photon cross sections are computed with MadGraph 5.0 for ultraperipheral A-A interactions with both ions surviving the collision. In the center-of-mass energy range $\sqrt{s}\approx 5$--100 TeV, the ratio of electromagnetic-to-partonic Higgs cross sections is ${\mathrm{R}}_{e.m./parton}\approx 10^{-5}$--10${}^{-4}$. At FCC energies, this ratio is 10--100 times larger in A-A than in p-p thanks to the strong nuclear coherent $\gamma$ fluxes. The feasibility of Higgs boson measurements at LHC, HE-LHC, and FCC, in the most-favourable $H\to \gamma \gamma ,b\bar{b}$ decay channels in partonic and e.m. interactions respectively, is determined taking into account standard acceptance and efficiency losses on the final states, plus selection criteria to minimize the respective continuum backgrounds. Whereas $3\sigma$ evidence for partonic and e.m. Higgs production requires about $\times$35 and $\times$200 ($\times$7 and $\times$30) larger integrated luminosities than those expected for a nominal 1-month run at the LHC (HE-LHC), a $5\sigma$ observation of both production modes is warranted in just one month at the FCC.

   ↳ hep-exhep-phnucl-exnucl-th1 citation
3. 03*

   Limits on assigning a shape to a nucleus

   Alfredo Poves🇪🇸 · Frederic Nowacki🇫🇷 · Yoram Alhassid🇺🇸

   The interpretation of nuclear observables in the laboratory frame in terms of the intrinsic deformation parameters beta and gamma is a classical theme in nuclear structure. Here we use the quadrupole invariants (Kumar), calculated within the framework of the configuration-interaction shell model, to clarify the meaning and limitations of nuclear shapes. We introduce a novel method that enables us to calculate accurately higher-order invariants and, therefore, the fluctuations in both beta and gamma. We find that the shape parameter beta often has a non-negligible degree of softness, and that the angle gamma is usually characterized by large fluctuations, rendering its effective value not meaningful. Contrary to common belief, we conclude that doubly magic nuclei are not spherical because the notion of a well-defined shape does not apply to them.

   ↳ nucl-thnucl-exPRC(2020)·55 citations
4. 04*

   Deformed shell effects in ${}^{48}$Ca+${}^{249}$Bk quasifission fragments

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

   Background: Quasifission is the main reaction channel hindering the formation of superheavy nuclei (SHN). Its understanding will help to optimize entrance channels for SHN studies. Quasifission also provides a probe to understand the influence of shell effects in the formation of the fragments. Purpose: Investigate the role of shell effects in quasifission and their interplay with the orientation of the deformed target in the entrance channel. Methods: ${}^{48}$Ca${+}^{249}$Bk collisions are studied with the time-dependent Hartree-Fock approach for a range of angular momenta and orientations. Results: Unlike similar reactions with a ${}^{238}$U target, no significant shell effects which could be attributed to ${}^{208}$Pb "doubly-magic" nucleus are found. However, the octupole deformed shell gap at $N=56$ seems to strongly influence quasifission in the most central collisions. Conclusions: Shell effects similar to those observed in fission affect the formation of quasifission fragments. Mass-angle correlations could be used to experimentally isolate the fragments influenced by $N=56$ octupole shell gaps.

   ↳ nucl-thnucl-exPRC(2019)·55 citations
5. 05*

   Sensitivity of one-neutron knockout to the nuclear structure of halo nuclei

   Chloë Hebborn🇺🇸 · Pierre Capel🇩🇪

   Background: Information about the structure of halo nuclei are often inferred from one-neutron knockout reactions. Typically the parallel-momentum distribution of the remaining core is measured after a high-energy collision of the exotic projectile with a light target. Purpose: We study how the structure of halo nuclei affects knockout observables considering an eikonal model of reaction. Method: To evaluate the sensitivity of both the diffractive and stripping parallel-momentum distributions to the structure of halo nuclei, we consider several descriptions of the projectile within a halo effective field theory. We consider the case of 11Be, the archetypical one-neutron halo nucleus, impinging on 12C at 68 MeV/nucleon, which are usual experimental conditions for such measurements. The low-energy constants of the description of 11Be are fitted to experimental data as well as to predictions of an ab initio nuclear-structure model. Results: One-neutron knockout reaction is confirmed to be purely peripheral, the parallel-momentum distribution of the remaining core is only sensitive to the asymptotics of the ground-state wavefunction and not to its norm. The presence of an excited state in the projectile spectrum reduces the amplitude of the breakup cross section; the corresponding probability flux is transferred to the inelastic-scattering channel. Although the presence of a resonance in the core-neutron continuum significantly affects the energy distribution, it has no impact on the parallel-momentum distribution. Conclusions: One-neutron knockout cross section can be used to infer information about the tail of the ground-state wavefunction, viz. its asymptotic normalization coefficient (ANC). The independence of the parallel-momentum distribution on the continuum description makes the extraction of the ANC from this observable very reliable.

   ↳ nucl-thnucl-exPRC(2019)·15 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.