Nuclear Theory·nucl-th

Monday·January 1, 2018

13 papers—8 primary·5 cross-listed

09
Finite Temperature Phase Diagrams of a Two-band Model of Superconductivity
Heron Caldas · A. Celes · David Nozadze
We explore the temperature effects in the superconducting phases of a hybridized two-band system. We show that for zero hybridization between the bands, there are two different critical temperatures. However, for any finite hybridization there are only one critical temperature at which the two gaps vanish simultaneously. We construct the phase diagrams of the critical temperature versus hybridization parameter $α$ and critical temperature versus critical chemical potential asymmetry $δ μ$ between the bands, identifying the superconductor and normal phases in the system. We find an interesting reentrant behavior in the superconducting phase as the parameters $α$ or $δ μ$ , which drive the phase transitions, increase. We also find that for optimal values of both $α$ and $δ μ$ there is a significant enhancement of the critical temperature of the model.
↳ cond-mat.supr-concond-mat.quant-gasnucl-thAnnals Phys.(2018)·1 citation
10
Prospects for $γ γ \to$ Higgs observation in ultraperipheral ion collisions at the Future Circular Collider
David d'Enterria🇨🇭 · Daniel E. Martins🇧🇷 · Patricia Rebello Teles🇧🇷
We study the two-photon production of the Higgs boson, $γ γ \to H$ , at the Future Circular Collider (FCC) in ultraperipheral PbPb and pPb collisions at $s_{N N} = 39$ and 63 TeV. Signal and background events are generated with MADGRAPH 5, including $γ$ fluxes from the proton and lead ions in the equivalent photon approximation, yielding $σ (γ γ \to H)$ = 1.75 nb and 1.5 pb in PbPb and pPb collisions respectively. We analyse the H $\to b b ˉ$ decay channel including realistic reconstruction efficiencies for the final-state $b$ -jets, showered and hadronized with PYTHIA 8, as well as appropriate selection criteria to reduce the dominant exclusive $γ γ \to b b ˉ$ continuum background. Observation of $PbPb γ γ (Pb) H (Pb)$ is achievable in the first year with the expected PbPb integrated luminosities.
↳ hep-phhep-exnucl-exnucl-thCERN Proc.(2018)·4 citations
11
Directed flow in Au+Au collisions from the RHIC Beam Energy Scan at the STAR experiment
Subhash Singha (for the STAR Collaboration)🇺🇸
We report results of $v_{1} (y)$ and $d v_{1} / d y$ near mid-rapidity for $π^{\pm}$ , $K^{\pm}$ , $K_{s}^{0}$ , $p$ , $p$ , $Λ$ , $Λ$ and $ϕ$ from Beam Energy Scan Au+Au collisions at $s_{N N} =$ 7.7 - 200 GeV using the STAR detector at RHIC. The $d v_{1} / d y$ of $π^{\pm}$ , $K^{\pm}$ and $K_{s}^{0}$ mesons remains negative over all beam energies. The $d v_{1} / d y$ of $p$ and $Λ$ baryons shows a sign change around 10 - 15 GeV, while net baryons (net p and net $Λ$ ) indicate a double sign change. The $d v_{1} / d y$ of $p$ , $Λ$ and $ϕ$ show a similar trend for $s_{N N} >$ 14.5 GeV. For the first time, $v_{1}$ measurements are used to test a quark coalescence hypothesis. Many measurements are found to be consistent with the particles being formed via coalescence of constituent quarks. The observed deviations from that consistency offer a new approach for probing the collision process at the quark level.
↳ nucl-exhep-exnucl-thPoS(2018)·0 citations
12
Traps in hadron spectroscopy: Thresholds, triangle singularities, etc
Feng-Kun Guo🇨🇳
The knowledge of hadron spectrum is based on experimental observations of hadronic resonances. The resonances are normally observed as peaks in certain invariant mass distributions. However, neither is a peak necessarily due to the presence of a resonance, nor does a resonance necessarily lead to a peak. Kinematic singularities can also produce peaks. Here, we discuss such possibilities and methods distinguishing genuine resonances from kinematic effects.
↳ hep-phhep-exnucl-thPoS(2018)·9 citations
13
Exclusive photoproduction of $π^{0}$ up to large values of Mandelstam variables $s, t$ and $u$ with CLAS
M.C. Kunkel · 32 · 18 M.J. Amaryan · 32 · I.I. Strakovsky · 16 J. Ritman · 3 · 18 G.R. Goldstein · 43 K.P. Adhikari · 28 S Adhikari · 13 H. Avakian · 39 J. Ball and 160 other authors
Exclusive photoproduction cross sections have been measured for the process $γ p \to p π^{0} (e^{+} e^{-} (γ))$ with the Dalitz decay final state using tagged photon energies in the range of $E_{γ} = 1.275 - 5.425$ GeV. The complete angular distribution of the final state $π^{0}$ , for the entire photon energy range up to large values of $t$ and $u$ , has been measured for the first time. The data obtained show that the cross section $d σ / d t$ , at mid to large angles, decreases with energy as $s^{- 6.89 \pm 0.26}$ . This is in agreement with the perturbative QCD quark counting rule prediction of $s^{- 7}$ . Paradoxically, the size of angular distribution of measured cross sections is greatly underestimated by the QCD based Generalized Parton Distribution mechanism at highest available invariant energy $s = 11$ GeV $^{2}$ . At the same time, the Regge exchange based models for $π^{0}$ photoproduction are more consistent with experimental data.
↳ hep-exhep-phnucl-exnucl-thPRC(2018)·27 citations

Affiliations

first authorsco-authorsvia INSPIRE

Finite Temperature Phase Diagrams of a Two-band Model of Superconductivity

Prospects for γγ→ Higgs observation in ultraperipheral ion collisions at the Future Circular Collider

Directed flow in Au+Au collisions from the RHIC Beam Energy Scan at the STAR experiment

Traps in hadron spectroscopy: Thresholds, triangle singularities, etc

Exclusive photoproduction of π0 up to large values of Mandelstam variables s,t and u with CLAS

Affiliations

Prospects for $γ γ \to$ Higgs observation in ultraperipheral ion collisions at the Future Circular Collider

Exclusive photoproduction of $π^{0}$ up to large values of Mandelstam variables $s, t$ and $u$ with CLAS