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Albaladejo, M., Guo, F. K., Hanhart, C., Meissner, U. G., Nieves, J., Nogga, A., et al. (2017). Note on X(3872) production at hadron colliders and its molecular structure. Chin. Phys. C, 41(12), 121001–3pp.
Abstract: The production of the X (3872) as a hadronic molecule in hadron colliders is clarified. We show that the conclusion of Bignamini et al., Phys. Rev. Lett. 103 (2009) 162001, that the production of the X(3872) at high pT implies a non-molecular structure, does not hold. In particular, using the well understood properties of the deuteron wave function as an example, we identify the relevant scales in the production process.
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Geng, L. S., Molina, R., & Oset, E. (2017). On the chiral covariant approach to rho rho scattering. Chin. Phys. C, 41(12), 124101–9pp.
Abstract: We examine in detail a recent work (D. Gulmez, U. G. Meibner and J. A. Oller, Eur. Phys. J. C, 77: 460 (2017)), where improvements to make rho rho scattering relativistically covariant are made. The paper has the remarkable conclusion that the J=2 state disappears with a potential which is much more attractive than for J=0, where a bound state is found. We trace this abnormal conclusion to the fact that an “on-shell” factorization of the potential is done in a region where this potential is singular and develops a large discontinuous and unphysical imaginary part. A method is developed, evaluating the loops with full rho propagators, and we show that they do not develop singularities and do not have an imaginary part below threshold. With this result for the loops we define an effective potential, which when used with the Bethe-Salpeter equation provides a state with J=2 around the energy of the f(2)(1270). In addition, the coupling of the state to is evaluated and we find that this coupling and the T matrix around the energy of the bound state are remarkably similar to those obtained with a drastic approximation used previously, in which the q(2) terms of the propagators of the exchanged rho mesons are dropped, once the cut-off in the rho rho loop function is tuned to reproduce the bound state at the same energy.
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Bazeia, D., Losano, L., Olmo, G. J., & Rubiera-Garcia, D. (2017). Geodesically complete BTZ-type solutions of 2+1 Born-Infeld gravity. Class. Quantum Gravity, 34(4), 045006–21pp.
Abstract: We study Born-Infeld gravity coupled to a static, non-rotating electric field in 2 + 1 dimensions and find exact analytical solutions. Two families of such solutions represent geodesically complete, and hence nonsingular, spacetimes. Another family represents a point-like charge with a singularity at the center. Despite the absence of rotation, these solutions resemble the charged, rotating BTZ solution of general relativity but with a richer structure in terms of horizons. The nonsingular character of the first two families turn out to be attached to the emergence of a wormhole structure on their innermost region. This seems to be a generic prediction of extensions of general relativity formulated in metric-affine (or Palatini) spaces, where metric and connection are regarded as independent degrees of freedom.
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Alfonso, V. I., Bejarano, C., Beltran Jimenez, J., Olmo, G. J., & Orazi, E. (2017). The trivial role of torsion in projective invariant theories of gravity with non-minimally coupled matter fields. Class. Quantum Gravity, 34(23), 235003–20pp.
Abstract: We study a large family of metric-affine theories with a projective symmetry, including non-minimally coupled matter fields which respect this invariance. The symmetry is straightforwardly realised by imposing that the connection only enters through the symmetric part of the Ricci tensor, even in the matter sector. We leave the connection completely free (including torsion), and obtain its general solution as the Levi-Civita connection of an auxiliary metric, showing that the torsion only appears as a projective mode. This result justifies the widely used condition of setting vanishing torsion in these theories as a simple gauge choice. We apply our results to some particular cases considered in the literature, including the so-called Eddington-inspired-Born-Infeld theories among others. We finally discuss the possibility of imposing a gauge fixing where the connection is metric compatible, and comment on the genuine character of the non-metricity in theories where the two metrics are not conformally related.
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Allanach, B. C., Martin, S. P., Robertson, D. G., & Ruiz de Austri, R. (2017). The inclusion of two-loop SUSYQCD corrections to gluino and squark pole masses in the minimal and next-to-minimal supersymmetric standard model: SOFTSUSY3.7. Comput. Phys. Commun., 219, 339–345.
Abstract: We describe an extension of the SOFTSUSY spectrum calculator to include two-loop supersymmetric QCD (SUSYQCD) corrections of order O(alpha(2)(s)) to gluino and squark pole masses, either in the minimal supersymmetric standard model (MSSM) or the next-to-minimal supersymmetric standard model (NMSSM). This document provides an overview of the program and acts as a manual for the new version of SOFTSUSY, which includes the increase in accuracy in squark and gluino pole mass predictions. Program summary Program title: SOFTSUSY Program Files doi: http://dx.doLorg/10.17632/sh77x9j7hs.1 Licensing provisions: GNU GPLv3 Programming language: C++, fortran, C Nature of problem: Calculating supersymmetric particle spectrum, mixing parameters and couplings in the MSSM or the NMSSM. The solution to the renormalization group equations must be consistent with theoretical boundary conditions on supersymmetry breaking parameters, as well as a weak-scale boundary condition on gauge couplings, Yukawa couplings and the Higgs potential parameters. Solution method: Nested fixed point iteration. Restrictions: SOFTSUSY will provide a solution only in the perturbative regime and it assumes that all couplings of the model are real (i.e. CP-conserving). If the parameter point under investigation is nonphysical for some reason (for example because the electroWeak potential does not have an acceptable minimum), SOFTSUSY returns an error message. The higher order corrections included are for the MSSM (R-parity conserving or violating) or the real R-parity conserving NMSSM only. Journal reference of previous version: Comput. Phys. Comm. 189 (2015) 192. Does the new version supersede the previous version?: Yes. Reasons for the new version: It is desirable to improve the accuracy of the squark and gluinos mass predictions, since they strongly affect supersymmetric particle production cross-sections at colliders. Summary of revisions: The calculation of the squark and gluino pole masses is extended to be of next-to next-to leading order in SUSYQCD, i.e. including terms up to O(g(s)(4)/(16 pi(2))(2)). Additional comments: Program obtainable from http://softsusy.hepforge.org/
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Guerrero, C., Domingo-Pardo, C., Kappeler, F., Lerendegui-Marco, J., Palomo, F. R., Quesada, J. M., et al. (2017). Prospects for direct neutron capture measurements on s-process branching point isotopes. Eur. Phys. J. A, 53(5), 87–5pp.
Abstract: The neutron capture cross sections of several unstable key isotopes acting as branching points in the s-process are crucial for stellar nucleosynthesis studies, but they are very challenging to measure directly due to the difficult production of sufficient sample material, the high activity of the resulting samples, and the actual (n, gamma) measurement, where high neutron fluxes and effective background rejection capabilities are required. At present there are about 21 relevant s-process branching point isotopes whose cross section could not be measured yet over the neutron energy range of interest for astrophysics. However, the situation is changing with some very recent developments and upcoming technologies. This work introduces three techniques that will change the current paradigm in the field: the use of gamma-ray imaging techniques in (n,gamma) experiments, the production of moderated neutron beams using high-power lasers, and double capture experiments in Maxwellian neutron beams.
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Kucuk, L. et al, Orrigo, S. E. A., Montaner-Piza, A., Rubio, B., Gelletly, W., Algora, A., et al. (2017). Half-life determination of T-z =-1 and T-z =-1/2 proton-rich nuclei and the beta decay of Zn-58. Eur. Phys. J. A, 53(6), 134–10pp.
Abstract: We have measured the beta-decay half-lives of 16 neutron-deficient nuclei with T-z = -1/2 and -1, ranging from chromium to germanium. They were produced in an experiment carried out at GANIL and optimized for the production of Zn-58, for which in addition we present the decay scheme and absolute Fermi and Gamow-Teller transition strengths. Since all of these nuclei lie on the rp-process pathway, the T-1/2 values are important ingredients for the rp-process reaction flow calculations and for models of X-ray bursters.
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Colovic, P. et al, & Gadea, A. (2017). Stretched configuration of states as inferred from gamma-ray angular distributions in Ar-40+Pb-208 neutron transfer reactions. Eur. Phys. J. A, 53(8), 166–6pp.
Abstract: Angular distributions of.-rays for selected transitions in Ar-40,Ar-41,Ar-42 isotopes have been studied with the PRISMA magnetic spectrometer coupled to the CLARA gamma array. These transitions were populated in Ar isotopes reached via neutron transfer in the Ar-40 + Pb-208 reaction. By comparison with the shape of the experimental angular distribution of the known E2 transitions we established more firmly the spin and parity of excited states. In particular, in Ar-41 for the (11/2(-)) state through the (11/2(-)) -> 7/2(-) transition whose structure was discussed in terms of a phonon-fermion coupled state. The comparison with the expected fully aligned spin indicated that a high level of spin alignment has been reached.
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Kim, Y. H. et al, & Perez-Vidal, R. M. (2017). Prompt-delayed gamma-ray spectroscopy with AGATA, EXOGAM and VAMOS plus. Eur. Phys. J. A, 53(8), 162–8pp.
Abstract: A new experimental setup to measure prompt-delayed gamma-ray coincidences from isotopically identified fission fragments, over a wide time range of 100 ns-200 μs, is presented. The fission fragments were isotopically identified, on an event-by-event basis, using the VAMOS++ large acceptance spectrometer. The prompt gamma rays emitted at the target position and corresponding delayed gamma rays emitted at the focal plane of the spectrometer were detected using, respectively, thirty two crystals of the AGATA gamma-ray tracking array and seven EXOGAM HPGe Clover detectors. Fission fragments produced in fusion and transfer-induced fission reactions, using a U-238 beam at an energy of 6.2MeV/u impinging on a Be-9 target, were used to characterize and qualify the performance of the detection system.
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Vento, V. (2017). AdS gravity and the scalar glueball spectrum. Eur. Phys. J. A, 53(9), 185–4pp.
Abstract: The scalar glueball spectrum has attracted much attention since the formulation of Quantum Chromodynamics. Different approaches give very different results for the glueball masses. We revisit the problem from the perspective of the AdS/CFT correspondence.
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