Nuclear Theory·nucl-th

Friday·August 5, 2016

7 papers—3 primary·4 cross-listed

04
Canonical description of the new LHCb resonances
Pablo G. Ortega🇪🇸 · Jorge Segovia🇩🇪 · David R. Entem🇪🇸 · Francisco Fernández🇪🇸
The LHCb Collaboration has recently observed four $J / ψ ϕ$ structures called $X (4140)$ , $X (4274)$ , $X (4500)$ and $X (4700)$ in the $B^{+} \to J / ψ ϕ K^{+}$ decays. We study them herein using a nonrelativistic constituent quark model in which the degrees of freedom are quark-antiquark and meson-meson components. The $X (4140)$ resonance appears as a cusp in the $J / ψ ϕ$ channel due to the near coincidence of the $D_{s}^{\pm} D_{s}^{*\pm}$ and $J / ψ ϕ$ mass thresholds. The remaining three $X (4274)$ , $X (4500)$ and $X (4700)$ appear as conventional charmonium states with quantum numbers $3^{3} P_{1}$ , $4^{3} P_{0}$ and $5^{3} P_{0}$ , respectively; and whose masses and widths are slightly modified due to their coupling with the corresponding closest meson-meson thresholds. A particular feature of our quark model is a lattice-based screened linear confining interaction that has been constrained in the light quark sector and usually produces higher excited heavy-quark states with lower masses than standard quark model predictions.
↳ hep-phhep-exhep-latnucl-thPRD(2016)·62 citations
05
Effects of Longitudinal Asymmetry in Heavy-Ion Collisions
Rashmi Raniwala (University of Rajasthan)🇮🇳 · Sudhir Raniwala (University of Rajasthan)🇺🇸 · Constantin Loizides (LBNL)🇺🇸
In collisions of identical nuclei at a given impact parameter, the number of nucleons participating in the overlap region of each nucleus can be unequal due to nuclear density fluctuations. The asymmetry due to the unequal number of participating nucleons, referred to as longitudinal asymmetry, causes a shift in the center of mass rapidity of the participant zone. The information of the event asymmetry allows us to isolate and study the effect of longitudinal asymmetry on rapidity distribution of final state particles. In a Monte Carlo Glauber model the average rapidity-shift is found to be almost linearly related to the asymmetry. Using toy models, as well as Monte Carlo data for Pb-Pb collisions at 2.76 TeV generated with HIJING, two different versions of AMPT and DPMJET models, we demonstrate that the effect of asymmetry on final state rapidity distribution can be quantitatively related to the average rapidity shift via a third-order polynomial with a dominantly linear term. The coefficients of the polynomial are proportional to the rapidity shift with the dependence being sensitive to the details of the rapidity distribution.Experimental estimates of the spectator asymmetry through the measurement of spectator nucleons in a Zero Degree Calorimeter may hence be used to further constrain the initial conditions in ultra-relativistic heavy-ion collisions.
↳ nucl-exnucl-thPRC(2018)·11 citations
06
Heteronuclear Efimov scenario with positive intraspecies scattering length
Juris Ulmanis · Stephan Häfner · Rico Pires · Eva D. Kuhnle · Yujun Wang · Chris H. Greene · Matthias Weidemüller
We investigate theoretically and experimentally the heteronuclear Efimov scenario for a three-body system that consists of two bosons and one distinguishable particle with positive intraspecies scattering lengths. The three-body parameter at the three-body scattering threshold and the scaling factor between consecutive Efimov resonances are found to be controlled by the scattering length between the two bosons, approximately independent of short-range physics. We observe two excited-state Efimov resonances in the three-body recombination spectra of an ultracold mixture of fermionic $^{6}$ Li and bosonic $^{133}$ Cs atoms close to a Li-Cs Feshbach resonance, where the Cs-Cs interaction is positive. Deviation of the obtained scaling factor of 4.0(3) from the universal prediction of 4.9 and the absence of the ground state Efimov resonance shed new light on the interpretation of the universality and the discrete scaling behavior of heteronuclear Efimov physics.
↳ cond-mat.quant-gasnucl-thphysics.atom-phquant-phPRL(2016)·21 citations
07
Photoproduction of the scalar mesons $f_{0} (500)$ and $f_{0} (980)$ off the nucleon
Je-Hee Lee🇰🇷 · Hyun-Chul Kim🇰🇷 · Sang-Ho Kim🇰🇷 · Hui-Young Ryu🇰🇷 · Byung-Geel Yu🇰🇷
We investigate photoproduction of the scalar mesona off the nucleon, using the effective Lagrangians and the Regge approach. We first study $f_{0} (980)$ photoproduction, replacing the Feynman propagator with the Regge ones for the $ρ$ -meson exchange in the $t$ -channel. The model parameters are fixed by reproducing the experimental data on the differential cross section. We then apply the same method to $f_{0} (500)$ or $σ$ photoproduction with the same parameters for the Regge propagator. Since the threshold energy of the $f_{0} (500)$ production is rather low, $N^{*}$ resonances, which can decay into the nucleon and two pions in the isoscalar and scalar state, can come into play in the $s$ -channel. To examine the effects of the $N^{*}$ resonances, we set up two models to look into the respective contribution of the $N^{*}$ resonances. We find that in particular $N^{*} (1440)$ and $N^{*} (1680)$ play important roles in $f_{0} (500)$ photoproduction. We discuss the physical implications of the present results.
↳ hep-phhep-exnucl-exnucl-thPTEP(2017)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Canonical description of the new LHCb resonances

Effects of Longitudinal Asymmetry in Heavy-Ion Collisions

Heteronuclear Efimov scenario with positive intraspecies scattering length

Photoproduction of the scalar mesons f0​(500) and f0​(980) off the nucleon

Affiliations

Photoproduction of the scalar mesons $f_{0} (500)$ and $f_{0} (980)$ off the nucleon