Nuclear Theory·nucl-th

Wednesday·January 23, 2019

23 papers—10 primary·13 cross-listed

11
The Jet Shape at NLL $^{'}$
Pedro Cal🇳🇱 · Felix Ringer🇺🇸 · Wouter J. Waalewijn🇳🇱
The jet shape is the fraction of the jet energy within a cone $r$ centered on the jet axis. We calculate the jet shape distribution at next-to-leading logarithmic accuracy plus next-to-leading order (NLL $^{'}$ ), accounting for logarithms of both the jet radius $R$ and the ratio $r / R$ . This is the first phenomenological study that takes the recoil of the jet axis due to soft radiation into account, which is needed to reach this accuracy, but complicates the calculation of collinear radiation and requires the treatment of rapidity logarithms and non-global logarithms. We present numerical results, finding good agreement with ATLAS and CMS measurements of the jet shape in an inclusive jet sample, $pp \to jet + X$ , for different kinematic bins. The effect of the underlying event and hadronization are included using a simple one-parameter model, since they are not part of our perturbative calculation.
↳ hep-phhep-exnucl-thJHEP(2019)·37 citations
12
Fate of spin polarization in a relativistic fluid: An entropy-current analysis
Koichi Hattori🇨🇳 · Masaru Hongo🇯🇵 · Xu-Guang Huang🇨🇳 · Mamoru Matsuo🇨🇳 · Hidetoshi Taya🇨🇳
We derive relativistic hydrodynamic equations with a dynamical spin degree of freedom on the basis of an entropy-current analysis. The first and second laws of local thermodynamics constrain possible structures of the constitutive relations including a spin current and the antisymmetric part of the (canonical) energy-momentum tensor. Solving the obtained hydrodynamic equations within the linear-mode analysis, we find spin-diffusion modes, indicating that spin density is damped out after a characteristic time scale controlled by transport coefficients introduced in the antisymmetric part of the energy-momentum tensor in the entropy-current analysis. This is a consequence of mutual convertibility between spin and orbital angular momentum.
↳ hep-thcond-mat.mes-hallcond-mat.stat-mechhep-ph+1PLB(2019)·230 citations
13
John Archibald Wheeler: A Biographical Memoir
Kip S. Thorne
John Archibald Wheeler was a theoretical physicist who worked on both down-to-earth projects and highly speculative ideas, and always emphasized the importance of experiment and observation, even when speculating wildly. His research and insights had large impacts on nuclear and particle physics, the design of nuclear weapons, general relativity and relativistic astrophysics, and quantum gravity and quantum information. But his greatest impacts were through the students, postdocs, and mature physicists whom he educated and inspired. He was guided by what he called the principle of radical conservatism, inspired by Niels Bohr: base your research on well established physical laws (be conservative), but push them into the most extreme conceivable domains (be radical). He often pushed far beyond the boundaries of well understood physics, speculating in prescient ways that inspired future generations of physicists. After completing his PhD with Karl Herzfeld at Johns Hopkins University (1933), Wheeler embarked on a postdoctoral year with Gregory Breit at NYU and another with Niels Bohr in Copenhagen. He then moved to a three-year assistant professorship at the University of North Carolina (1935-37), followed by a 40 year professorial career at Princeton University (1937-1976) and then ten years as a professor at the University of Texas, Austin (1976-1987). He returned to Princeton in retirement but remained actively and intensely engaged with physics right up to his death at age 96.
↳ physics.hist-phastro-ph.HEgr-qchep-th+17 citations
14
Causality of the Einstein-Israel-Stewart Theory with Bulk Viscosity
Fabio S. Bemfica (Rio Grande do Norte U.)🇧🇷 · Marcelo M. Disconzi (Vanderbilt U.)🇺🇸 · Jorge Noronha (Sao Paulo U.)🇧🇷
We prove that Einstein's equations coupled to equations of Israel-Stewart-type, describing the dynamics of a relativistic fluid with bulk viscosity and nonzero baryon charge (without shear viscosity or baryon diffusion) dynamically coupled to gravity, are causal in the full nonlinear regime. We also show that these equations can be written as a first-order symmetric hyperbolic system, implying local existence and uniqueness of solutions to the equations of motion. We use an arbitrary equation of state and do not make any simplifying symmetry or near-equilibrium assumption, requiring only physically natural conditions on the fields. These results pave the way for the inclusion of bulk viscosity effects in simulations of gravitational-wave signals coming from neutron star mergers.
↳ gr-qcastro-ph.HEhep-phmath-ph+2PRL(2019)·124 citations
15
Higher order Symmetric Cumulants
Cindy Mordasini🇩🇪 · Ante Bilandzic🇩🇪 · Deniz Karakoç🇩🇪 · Seyed Farid Taghavi🇩🇪
We present the generalization of recently introduced observables for the studies of correlated fluctuations of different anisotropic flow amplitudes, dubbed Symmetric Cumulants. We introduce a new set of higher order observables and outline a unique way how the genuine multi-harmonic correlations can be extracted from multi-particle azimuthal correlators. We argue that correlations among flow amplitudes can be studied reliably with the general mathematical formalism of cumulants only if that formalism is applied directly on the flow amplitudes. We have tested all the desired properties of new observables with the carefully designed Toy Monte Carlo studies. By using the realistic iEBE-VISHNU model, we have demonstrated that their measurements are feasible and we have provided the predictions for the centrality dependence in Pb--Pb collisions at LHC energies. A separate study was performed for their values in the coordinate space. The new observables contain information which is inaccessible to individual flow amplitudes and correlated fluctuations of only two flow amplitudes, and therefore they provide further and independent constraints for the initial conditions and the properties of Quark-Gluon Plasma in high-energy nuclear collisions.
↳ nucl-exhep-exnucl-thPRC(2020)·42 citations
16
Implementing the three-particle quantization condition including higher partial waves
Tyler D. Blanton🇺🇸 · Fernando Romero-López🇪🇸 · Stephen R. Sharpe🇺🇸
We present an implementation of the relativistic three-particle quantization condition including both $s$ - and $d$ -wave two-particle channels. For this, we develop a systematic expansion about threshold of the three-particle divergence-free K matrix, $K_{df, 3}$ , which is a generalization of the effective range expansion of the two-particle K matrix, $K_{2}$ . Relativistic invariance plays an important role in this expansion. We find that $d$ -wave two-particle channels enter first at quadratic order. We explain how to implement the resulting multichannel quantization condition, and present several examples of its application. We derive the leading dependence of the threshold three-particle state on the two-particle $d$ -wave scattering amplitude, and use this to test our implementation. We show how strong two-particle $d$ -wave interactions can lead to significant effects on the finite-volume three-particle spectrum, including the possibility of a generalized three-particle Efimov-like bound state. We also explore the application to the $3 π^{+}$ system, which is accessible to lattice QCD simulations, where we study the sensitivity of the spectrum to the components of $K_{df, 3}$ . Finally, we investigate the circumstances under which the quantization condition has unphysical solutions.
↳ hep-latcond-mat.stat-mechhep-phnucl-th+1JHEP(2019)·119 citations
17
Dynamical analysis of the $X$ resonance contributions to the decay $J / ψ \to γ X \to γ ϕϕ$
A.A. Kozhevnikov🇷🇺
The dynamics of the $J^{P C} = 0^{-+}$ , $0^{++}$ , and $2^{++}$ resonance contributions to the decay $J / ψ \to γ X (J^{P C}) \to γ ϕϕ$ is analysed using the data obtained by BESIII collaboration. The effective coupling constants parameterising invariant amplitudes of the transitions $J / ψ \to γ X (J^{P C})$ and $X (J^{P C}) \to ϕϕ$ and masses of $X (J^{P C})$ resonances are found from the fits. They are used for evaluation of the branching fractions $B_{X (J^{P C}) \to ϕϕ}$ , relative branching fractions $B_{J / ψ \to γ X (J^{P C}) \to γ ϕϕ}$ , and for obtaining the photon angular distributions.
↳ hep-phhep-exnucl-thPRD(2019)·7 citations
18
Recent Progress on the QCD Phase Diagram
Sayantan Sharma🇮🇳
Recent progress and the latest results on the bulk thermodynamic properties of QCD matter from lattice are reviewed. In particular, I will stress upon the fact that lattice techniques are now entering into precision era where they can provide us with new insights on even the microscopic degrees of freedom in different phases of QCD. I will discuss some instances, from the recent studies of topological fluctuations and screening masses. The progress towards understanding the effects of anomalous $U_{A} (1)$ symmetry on the chiral crossover transition and transport properties of QCD matter will also be discussed.
↳ hep-lathep-phnucl-thPoS(2019)·18 citations
19
Fate of the doubly heavy spin $- 3/2$ baryons in a dense medium
N. Er🇹🇷 · K. Azizi🇹🇷
We investigate the behavior of the doubly heavy spin $- 3/2$ baryons in cold nuclear matter. In particular, we study the variations of the spectroscopic parameters of the ground state $Ξ_{Q Q^{'}}^{*}$ and $Ω_{Q Q^{'}}^{*}$ particles, with $Q$ and $Q^{'}$ being $b$ or $c$ quark, with respect to the changes in the density of the nuclear medium. We find the shifts on the parameters under question at saturation medium density compared to their vacuum values. It is observed that the parameters of the $Ξ_{Q Q^{'}}^{*}$ states containing two heavy quarks and one up or down quark are affected by the medium, considerably. The parameters of the $Ω_{Q Q^{'}}^{*}$ states containing two heavy quarks and one strange quark, however, do not show any sensitivity to the density of the cold nuclear medium. We also discuss the variations of the vector self-energy at each channel with respect to the changes in the density. The negative shifts in the mass of $Ξ_{Q Q^{'}}^{*}$ states due to nucleons in the medium can be used to study the doubly heavy baryons' interactions with the nucleons. The results obtained can also be used in analyses of the results of the future in-medium experiments.
↳ hep-phhep-exhep-latnucl-thPRD(2019)·5 citations
20
$Φ$ and $J /Ψ$ Mesons in Cold Nuclear Matter
J. J. Cobos-Martínez🇲🇽 · K. Tsushima🇧🇷 · G. Krein🇧🇷 · A. W. Thomas🇦🇺
We present $Φ$ - and $J /Ψ$ --nuclear bound state energies and absorption widths for some selected nuclei, using potentials in the local density approximation computed from an effective Lagrangian approach combined with the quark-meson coupling model. Our results suggest that these mesons should form bound states with all the nuclei considered provided that these mesons are produced in nearly recoilless kinematics.
↳ hep-phnucl-exnucl-thJPS Conf.Proc.(2019)·3 citations
21
Soft modifications to jet fragmentation in high energy proton-proton collisions
Christian Bierlich🇩🇰
The discovery of collectivity in proton-proton collisions, is one of the most puzzling outcomes from the two first runs at LHC, as it points to the possibility of creation of a Quark-Gluon Plasma, earlier believed to only be created in heavy ion collisions. One key observation from heavy ion collisions is still not observed in proton-proton, namely jet-quenching. In this letter it is shown how a model capable of describing soft collective features of proton-proton collisions, also predicts modifications to jet fragmentation properties. With this starting point, several new observables suited for the present and future hunt for jet quenching in small collision systems are proposed.
↳ hep-phnucl-thPLB(2019)·18 citations
22
Orbital Angular Momentum at Small $x$
Yuri V. Kovchegov🇺🇸
We determine the small Bjorken $x$ asymptotics of the quark and gluon orbital angular momentum (OAM) distributions in the proton in the double-logarithmic approximation (DLA), which resums powers of $α_{s} ln^{2} (1/ x)$ with $α_{s}$ the strong coupling constant. Starting with the operator definitions for the quark and gluon OAM, we simplify them at small $x$ , relating them, respectively, to the polarized dipole amplitudes for the quark and gluon helicities defined in our earlier works. Using the small- $x$ evolution equations derived for these polarized dipole amplitudes earlier we arrive at the following small- $x$ asymptotics of the quark and gluon OAM distributions in the large- $N_{c}$ limit: \begin{align} L_{q + \bar{q}} (x, Q^2) = - \Delta \Sigma (x, Q^2) \sim \left(\frac{1}{x}\right)^{\frac{4}{\sqrt{3}} \, \sqrt{\frac{\alpha_s \, N_c}{2 \pi}} }, \ \ \ \ \ L_G (x, Q^2) \sim \Delta G (x, Q^2) \sim \left(\frac{1}{x}\right)^{\frac{13}{4 \sqrt{3}} \, \sqrt{\frac{\alpha_s \, N_c}{2 \pi}}} . \end{align}
↳ hep-phnucl-exnucl-thJHEP(2019)·61 citations
23
Lattice QCD determination of neutron-antineutron matrix elements with physical quark masses
Enrico Rinaldi🇺🇸 · Sergey Syritsyn🇺🇸 · Michael L. Wagman🇺🇸 · Michael I. Buchoff🇺🇸 · Chris Schroeder🇺🇸 · Joseph Wasem🇺🇸
Matrix elements of six-quark operators are needed to extract new physics constraints from experimental searches for neutron-antineutron oscillations. This work presents in detail the first lattice quantum chromodynamics calculations of the necessary neutron-antineutron transition matrix elements including calculation methods and discussions of systematic uncertainties. Implications of isospin and chiral symmetry on the matrix elements, power counting in the isospin limit, and renormalization of a chiral basis of six-quark operators are discussed. Calculations are performed with a chiral-symmetric discretization of the quark action and physical light quark masses in order to avoid the need for chiral extrapolation. Non-perturbative renormalization is performed, including a study of lattice cutoff effects. Excited-state effects are studied using two nucleon operators and multiple values of source-sink separation. Results for the dominant matrix elements are found to be significantly larger compared to previous results from the MIT bag model. Future calculations are needed to fully account for systematic uncertainties associated with discretization and finite-volume effects but are not expected to significantly affect this conclusion.
↳ hep-lathep-phnucl-thPRD(2019)·74 citations

Affiliations

first authorsco-authorsvia INSPIRE