Production of thermal photons in viscous fluid dynamics with temperature-dependent shear viscosity

We compute the spectrum of thermal photons created in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV, taking into account dissipative corrections in production processes corresponding to the quark--gluon plasma and hadronic phases. To describe the evolution of the fireball we use a viscous fluid dynamic model with different parametrizations for the temperature--dependence of $\eta/s$. We find that the spectrum significantly depends on the values of $\eta/s$ in the QGP phase, and is almost insensitive to the values in the hadronic phase. We also compare the influence of the temperature--dependence of $\eta/s$ on the spectrum of thermal photons to that of using different equations of state in the fluid dynamic simulations, finding that both effects are of the same order of magnitude.Comment: 16 pages, 4 figures. Accepted for publication in Mod. Phys. Lett.

Description of the 11^{11}Li(p,d)10(p,d){^{10}}Li transfer reaction using structure overlaps from a full three-body model

Recent data on the differential angular distribution for the transfer reaction $^{11}$Li(p,d)$^{10}$Li at $E/A=5.7$ MeV in inverse kinematics are analysed within the DWBA reaction framework, using the overlap functions calculated within a three-body model of $^{11}$Li. The weight of the different $^{10}$Li configurations in the system's ground state is obtained from the structure calculations unambiguously. The effect of the $^{9}$Li spin in the calculated observables is also investigated. We find that, although all the considered models succeed in reproducing the shape of the data, the magnitude is very sensitive to the content of $p_{1/2}$ wave in the $^{11}$Li ground-state wave function. Among the considered models, the best agreement with the data is obtained when the $^{11}$Li ground state contains a $\sim$31\% of $p_{1/2}$ wave in the $n$-$^9$Li subsystem. Although this model takes into account explicitly the splitting of the $1^+$ and $2^+$ resonances due to the coupling of the $p_{1/2}$ wave to the $3/2^-$ spin of the core, a similar degree of agreement can be achieved with a model in which the $^{9}$Li spin is ignored, provided that it contains a similar p-wave content.Comment: 8 pages, 3 figures. Final versio

Linking structure and dynamics in (p,pn)(p,pn) reactions with Borromean nuclei: the 11^{11}Li(p,pn)10(p,pn){^{10}}Li case

One-neutron removal $(p,pn)$ reactions induced by two-neutron Borromean nuclei are studied within a Transfer-to-the-Continuum (TC) reaction framework, which incorporates the three-body character of the incident nucleus. The relative energy distribution of the residual unbound two-body subsystem, which is assumed to retain information on the structure of the original three-body projectile, is computed by evaluating the transition amplitude for different neutron-core final states in the continuum. These transition amplitudes depend on the overlaps between the original three-body ground-state wave function and the two-body continuum states populated in the reaction, thus ensuring a consistent description of the incident and final nuclei. By comparing different $^{11}$Li three-body models, it is found that the $^{11}$Li$(p,pn){^{10}}$Li relative energy spectrum is very sensitive to the position of the $p_{1/2}$ and $s_{1/2}$ states in $^{10}$Li and to the partial wave content of these configurations within the $^{11}$Li ground-state wave function. The possible presence of a low-lying $d_{5/2}$ resonance is discussed. The coupling of the single particle configurations with the non-zero spin of the $^{9}$Li core, which produces a spin-spin splitting of the states, is also studied. Among the considered models, the best agreement with the available data is obtained with a $^{11}$Li model that incorporates the actual spin of the core and contains $\sim$31\% of $p_{1/2}$-wave content in the $n$-$^9$Li subsystem, in accord with our previous findings for the $^{11}$Li(p,d)$^{10}$Li transfer reaction, and a near-threshold virtual state.Comment: 7 pages, 4 figures, submitted to PL

Disentangling phase transitions and critical points in the proton-neutron interacting boson model by catastrophe theory

We introduce the basic concepts of catastrophe theory needed to derive analytically the phase diagram of the proton-neutron interacting boson model (IBM-2). Previous studies [1,2,3] were based on numerical solutions. We here explain the whole IBM-2 phase diagram including the precise order of the phase transitions in terms of the cusp catastrophe.Comment: To be published in Physics Letters

Investigating the 10Li continuum through 9Li(d,p)10Li reactions

The continuum structure of the unbound system $^{10}$Li, inferred from the $^{9}$Li$(d,p)^{10}$Li transfer reaction, is reexamined. Experimental data for this reaction, measured at two different energies, are analyzed with the same reaction framework and structure models. It is shown that the seemingly different features observed in the measured excitation energy spectra can be understood as due to the different incident energy and angular range covered by the two experiments. The present results support the persistence of the $N=7$ parity inversion beyond the neutron dripline as well as the splitting of the well-known low-lying $p$-wave resonance. Furthermore, they provide indirect evidence that most of the $\ell=2$ single-particle strength, including possible $d_{5/2}$ resonances, lies at relatively high excitations energies.Comment: accepted for publication in Physics Letters