Nuclear Theory·nucl-th

Friday·December 23, 2016

13 papers—6 primary·7 cross-listed

01
[Submitted on 21 Dec 2016]
Quasiparticle second-order viscous hydrodynamics from kinetic theory
Leonardo Tinti🇺🇸 · Amaresh Jaiswal🇩🇪 · Radoslaw Ryblewski🇵🇱
We present the derivation of second-order relativistic viscous hydrodynamics from an effective Boltzmann equation for a system consisting of quasiparticles of a single species. We consider temperature-dependent masses of the quasiparticles and devise a thermodynamically-consistent framework to formulate second-order evolution equations for shear and bulk viscous pressure corrections. The main advantage of this formulation is that one can consistently implement realistic equation of state of the medium within the framework of kinetic theory. Specializing to the case of one-dimensional purely-longitudinal boost-invariant expansion, we study the effect of this new formulation on viscous hydrodynamic evolution of strongly-interacting matter formed in relativistic heavy-ion collisions.
Comments:
10 pages, 3 figures, version published in Phys. Rev. D
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1612.07329 [pdf]
PRD(2017)·50 citations
02
[Submitted on 21 Dec 2016]
Extracting Neutron Polarizabilities from Compton Scattering on The Quasi-Free Neutrons in $γ d \to γ n p$
Berhan Demissie🇺🇸 · Harald W. Grießhammer🇺🇸
Compton scattering processes are ideal to study electric and magnetic dipole polarizabilities of nucleons. These fundamental quantities parametrize the responses of the internal degrees of freedoms to a monochromatic photon probe. In this work, the inelastic channel $γ d \to γ n p$ is treated in $χ$ EFT, with a focus on the kinematic region of the neutron quasi-free peak, where the momentum of the outgoing proton is small enough that it is considered to remain at rest. This provides access to the Compton scattering process $γ n \to γ n$ , from which the scalar polarizabilites of the neutron, $α_{E 1}$ and $β_{M 1}$ , are extracted. Using $χ$ EFT, triple differential cross-sections $d^{3} σ / d E_{n} d Ω_{γ^{'}} Ω_{n}$ in the photon energy range of 200-to-400 MeV are computed. The biggest contribution comes from the impulse approximation, with small corrections stemming from final state interactions, meson exchange currents and rescattering. In this presentation, we report progress and preliminary results.
Comments:
9 pages, 10 figures, presented at the 8th International Workshop on Chiral Dynamics (CD2015), accepted for publication in the PoS, PoS(CD15)097
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1612.07351 [pdf]
2 citations
03
[Submitted on 21 Dec 2016]
Electromagnetic probes of heavy ion collisions: recent developments
Jean-François Paquet🇺🇸
The current status of photon and dilepton emission in ultra-relativistic heavy ion collisions is reviewed, and recent developments are highlighted. The importance of emissions at early, intermediate and late times is emphasized.
Comments:
6 pages, 3 figures, contribution to Hard Probes 2016 proceedings. Figure 2 corrected. To be published in Nuclear and Particle Physics Proceedings
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1612.07359 [pdf]
Nucl.Part.Phys.Proc.(2017)·4 citations
04
[Submitted on 22 Dec 2016]
Mass and width of the $Δ (1232)$ resonance using complex-mass renormalization
T. Bauer🇩🇪 · Y. Unal🇩🇪 · A. Kucukarslan🇹🇷 · S. Scherer🇩🇪
We discuss the pole mass and the width of the $Δ (1232)$ resonance to third order in chiral effective field theory. In our calculation we choose the complex-mass renormalization scheme (CMS) and show that the CMS provides a consistent power-counting scheme. In terms of the pion-mass dependence, we compare the convergence behavior of the CMS with the small-scale expansion (SSE).
Comments:
15 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1612.07506 [pdf]
PRC(2017)·2 citations
05
[Submitted on 22 Dec 2016]
Electric Properties of One-Neutron Halo Nuclei in Halo EFT
Jonas Braun🇩🇪 · Hans-Werner Hammer🇩🇪
We exploit the separation of scales in weakly-bound nuclei to compute E2 transitions and electric form factors in a Halo EFT framework. The relevant degrees of freedom are the core and the halo neutron. The EFT expansion is carried out in powers of $R_{cor e} / R_{ha l o}$ , where $R_{cor e}$ and $R_{ha l o}$ denote the length scales of the core and halo, respectively. We include the strong $s$ -wave and $d$ -wave interactions by introducing dimer fields. The dimer propagators are regulated by employing the power divergence subtraction scheme and matched to the effective range expansion in the respective channel.Electromagnetic interactions are included via minimal substitution in the Lagrangian. We demonstrate that, depending on the observable and respective partial wave, additional local gauge-invariant operators contribute in LO, NLO and higher orders.
Comments:
4 pages, 2 figures, proceedings of EFB23
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1612.07689 [pdf]
Few Body Syst.(2017)·3 citations
06
[Submitted on 22 Dec 2016]
Implications of Missing Resonances in Heavy Ions Collisions
Jacquelyn Noronha-Hostler🇺🇸
Between 2004 until today many new resonances in the QCD spectrum have been added by the Particle Data Group. However, it is still possible that there are further states that have yet to be measured, as predicted by Lattice QCD calculations and Quark Models. In this paper I review how these missing states would influence the field of heavy-ion collisions. Additionally, the quantum numbers that characterize these missing states are also discussed.
Comments:
6 pages, 7 figures, Talk presented by JNH at the YSTAR2016 meeting on Excited Hyperons in QCD Thermodynamics at Freeze-Out, 16-17 November 2016, Thomas Jefferson National Accelerator Facility, Newport News, VA
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1612.07765 [pdf]
5 citations
07
[Submitted on 21 Dec 2016] (cross-list from hep-lat)
Deconfinement, gradient and cooling scales for pure SU(2) lattice gauge theory
Bernd A. Berg🇺🇸 · David A. Clarke🇺🇸
We investigate the approach of pure SU(2) lattice gauge theory with the Wilson action to its continuum limit using the deconfining phase transition, the gradient flow and the cooling flow to set the scale. For the gradient and cooling scales we explore three different energy observables and two distinct reference values for the flow time. When the aim is to follow scaling towards the continuum limit, one gains at least a factor of 100 in computational efficiency by relying on the gradient instead of the deconfinement scale. Using cooling instead of the gradient flow one gains another factor of at least 34 in computational efficiency on the gradient flow part without any significant loss in the accuracy of scale setting. Concerning our observables, the message is to keep it simple. The Wilson action itself performs as well as or even better than the other two observables explored. Two distinct fitting forms for scaling are compared of which one connects to asymptotic scaling. Differences of the obtained estimates show that systematic errors of length ratios, though only about 1%, can be considerably larger than statistical errors of the same observables.
Comments:
13 pages, 5 figures
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1612.07347 [pdf]
PRD(2017)·15 citations
08
[Submitted on 21 Dec 2016] (cross-list from gr-qc)
Lorentz-symmetry test at Planck-scale suppression with nucleons in a spin-polarized $^{133}$ Cs cold atom clock
H. Pihan-Le Bars🇫🇷 · C. Guerlin🇫🇷 · R.-D. Lasseri🇫🇷 · J.-P. Ebran🇫🇷 · Q. G. Bailey🇺🇸 · S. Bize🇫🇷 · E. Khan🇫🇷 · P. Wolf🇫🇷
We introduce an improved model that links the frequency shift of the $^{133} Cs$ hyperfine Zeeman transitions $∣ F = 3, m_{F} >⟷ ∣ F = 4, m_{F} >$ to the Lorentz-violating Standard-Model Extension (SME) coefficients of the proton and neutron. The new model uses Lorentz transformations developed to second order in boost and additionally takes the nuclear structure into account, beyond the simple Schmidt model used previously in SME analyses, thereby providing access to both proton and neutron SME coefficients including the isotropic coefficient $c ~_{T T}$ . Using this new model in a second analysis of the data delivered by the FO2 dual Cs/Rb fountain at Paris Observatory and previously analysed in arXiv:hep-ph/0601024v1, we improve by up to 12 orders of magnitude the present maximum sensitivities (see arXiv:0801.0287v9) on the $c ~_{Q}$ , $c ~_{T J}$ and $c ~_{T T}$ coefficients for the neutron and on the $c ~_{T T}$ coefficient for the proton, reaching respectively $1 0^{- 20}$ , $1 0^{- 17}$ , $1 0^{- 13}$ and $1 0^{- 15}$ GeV.
Subjects:
General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
arXiv:
1612.07390 [pdf]
PRD(2017)·43 citations
09
[Submitted on 22 Dec 2016] (cross-list from hep-lat)
Light-quark contributions to the magnetic form factor of the Lambda(1405)
Jonathan M. M. Hall🇦🇺 · Waseem Kamleh🇦🇺 · Derek B. Leinweber🇦🇺 · Benjamin J. Menadue🇦🇺 · Benjamin J. Owen🇦🇺 · Anthony W. Thomas🇦🇺
In a recent study of the Lambda(1405), the suppression of the strange-quark contribution to the magnetic form factor was interpreted as the discovery of a dominant antikaon-nucleon composition for this low-lying state. We confirm this result by calculating the light u- and d-quark contributions to the Lambda(1405) magnetic form factor in lattice QCD in order to determine the extent to which their contributions support this exotic molecular description. Drawing on the recent graded-symmetry approach for the flavor-singlet components of the Lambda(1405), the separation of connected and disconnected contributions is performed in both the flavor-octet and singlet representations. The relationship between light-quark contributions to the Lambda(1405) magnetic form factor and the connected contributions of the nucleon magnetic form factors is established and compared with lattice calculations of the same quantities, confirming the KN molecular structure of the Lambda(1405) in lattice QCD.
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1612.07477 [pdf]
PRD(2017)·34 citations
10
[Submitted on 22 Dec 2016] (cross-list from hep-ph)
Magnetic-Field Induced Critical Endpoint
Stefan Rechenberger🇩🇪
The phase diagram of strong interaction matter is analyzed utilizing the Nambu--Jona-Lasinio model. Special emphasis is placed on its dependence on an external magnetic field and isospin chemical potential. Using flavor mixing induced by instanton effects the influence of isospin breaking due to the magnetic field and the isospin chemical potential is compared. It is found that at low temperatures and large quark chemical potential the magnetic field, depending on its strength, induces a new critical endpoint or a triple point.
Comments:
8 pages, 5 figures, references added in second version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1612.07541 [pdf]
PRD(2017)·9 citations
11
[Submitted on 22 Dec 2016] (cross-list from hep-lat)
Strong isospin violation and chiral logarithms in the baryon spectrum
David A. Brantley🇺🇸 · Balint Joo🇺🇸 · Ekaterina V. Mastropas🇺🇸 · Emanuele Mereghetti🇺🇸 · Henry Monge-Camacho🇺🇸 · Brian C. Tiburzi🇺🇸 · Andre Walker-Loud🇺🇸
We present a precise lattice QCD calculation of the contribution to the neutron-proton mass splitting arising from strong isospin breaking, $m_{n} - m_{p} ∣_{QC D} = 2.32 \pm 0.17$ MeV. We also determine $m_{Ξ^{-}} - m_{Ξ^{0}} ∣_{QC D} = 5.44 \pm 0.31$ MeV. The calculation is performed at three values of the pion mass, with several values of the quark mass splitting and multiple lattice volumes, but only a single lattice spacing and an estimate of discretization errors. The calculations are performed on the anisotropic clover-Wilson ensembles generated by the Hadron Spectrum Collaboration. The omega-baryon mass is used to set the scale $a_{t}^{- 1} = 6111 \pm 127$ MeV, while the kaon masses are used to determine the value of the light-quark mass spitting. The nucleon mass splitting is then determined as a function of the pion mass. We observe, for the first time, conclusive evidence for non-analytic light quark mass dependence in lattice QCD calculations of the baryon spectrum. When left as a free parameter, the fits prefer a nucleon axial coupling of $g_{A} = 1.24 (56)$ . To highlight the presence of this chiral logarithm in the nucleon mass splitting, we also compute the isospin splitting in the cascade-baryon system which is less sensitive to chiral dynamics. Finally, we update the best lattice QCD determination of the CP-odd pion-nucleon coupling that would arise from a non-zero QCD theta-term, $g ˉ_{0} / (2 f_{π}) = (14.7 \pm 1.8 \pm 1.4) \cdot 1 0^{- 3} θ ˉ$ . The original lattice QCD correlation functions, analysis results and extrapolated quantities are packaged in HDF5 files made publicly available including a simple Python script to access the numerical results, construct effective mass plots along with our analysis results, and perform the extrapolations of various quantities determined in this work.
Comments:
16 pages including figures and tables. The original lattice QCD correlation functions and our analysis results can be found at this address http://ntc0.lbl.gov/~walkloud/mn_mns_mp/ stored in HDF5 format. Additionally, there are a number of Python files which can be used to access the original results and our analysis, see the README.txt to get started
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1612.07733 [pdf]
45 citations
12
[Submitted on 22 Dec 2016] (cross-list from hep-ph)
Helicity Evolution at Small x: Summary of Recent Developments
Yuri V. Kovchegov🇺🇸 · Daniel Pitonyak🇺🇸 · Matthew D. Sievert🇺🇸
We construct small- $x$ evolution equations which can be used to calculate quark and anti-quark helicity TMDs and PDFs, along with the $g_{1}$ structure function. These evolution equations resum powers of $α_{s} ln^{2} (1/ x)$ in the polarization-dependent evolution along with the powers of $α_{s} ln (1/ x)$ in the unpolarized evolution which includes saturation effects. The equations are written in an operator form in terms of polarization-dependent Wilson line-like operators. While the equations do not close in general, they become closed and self-contained systems of non-linear equations in the large- $N_{c}$ and large- $N_{c} & N_{f}$ limits. We construct a numerical solution of the helicity evolution equations in the large- $N_{c}$ limit. Employing the extracted intercept, we are able to predict directly from theory the behavior of the quark helicity PDFs at small $x$ , which should have important phenomenological consequences. We also give an estimate of how much of the proton's spin may be at small $x$ and what impact this has on the so-called "spin crisis." Based on JHEP 1601 (2016) 072 (arXiv:1511.06737), arXiv:1610.06197 and arXiv:1610.06188.
Comments:
8 pages, 6 figures; combined proceedings of "QCD Evolution 2016" workshop, Amsterdam, Netherlands, May 30 - June 3, 2016 and the 22nd International Spin Symposium (SPIN 2016), Champaign, IL, USA, September 26 - 30, 2016. Based on JHEP 1601 (2016) 072 (arXiv:1511.06737), arXiv:1610.06197 and arXiv:1610.06188
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1612.07758 [pdf]
0 citations
13
[Submitted on 22 Dec 2016] (cross-list from hep-ph)
Exploring correlations in the CGC wave function: odd azimuthal anisotropy
Alex Kovner🇺🇸 · Michael Lublinsky🇮🇱 · Vladimir Skokov🇺🇸
We extend the CGC approach to calculation of the double inclusive gluon production by including high-density effect in the CGC wave function of the projectile (proton). Our main result is that these effects lead to the appearance of odd harmonics in the two-particle correlation C(k,p). We find that in the high momentum limit, |k|,|p|>>Q_s, this results in a positive c_1{2}. Additionally when the magnitudes of the two momenta are approximately equal, |k|/|p| ~ 1, the density effects also generate a positive third harmonic c_3{2}, which translates into a non-vanishing v_3 when the momenta of the trigger and associated particle are in the same momentum bin. The sign of c_3{2} becomes negative when |k|/|p|>1.1 suggesting an interesting experimental signature.
Comments:
32 pages; 5 figures; version accepted to Phys. Rev. D
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1612.07790 [pdf]
PRD(2017)·44 citations

Affiliations

first authorsco-authorsvia INSPIRE