Nuclear Theory·nucl-th

Friday·December 13, 2019

17 papers—7 primary·10 cross-listed

01
[Submitted on 11 Dec 2019]
Multi-gluon correlations and evidence of saturation from dijet measurements at an Electron Ion Collider
Heikki Mäntysaari🇫🇮 · Niklas Mueller🇺🇸 · Farid Salazar🇺🇸 · Björn Schenke🇺🇸
We study inclusive and diffractive dijet production in electron-proton and electron-nucleus collisions within the Color Glass Condensate effective field theory. We compute dijet cross sections differentially in both mean dijet transverse momentum $P$ and recoil momentum $Δ$ , as well as the anisotropy in the relative angle between $P$ and $Δ$ . We use the nonlinear Gaussian approximation to compute multiparticle correlators for general small $x$ kinematics, employing running coupling Balitsky-Kovchegov evolution to determine the dipole amplitude at small $x$ . Our results cover a much larger kinematic range than accessible in previous computations performed in the correlation limit approximation, where it is assumed that $∣ P ∣ ≫ ∣ Δ ∣$ . We validate this approximation in its range of applicability and quantify its failure for $∣ P ∣ ≲ ∣ Δ ∣$ . We also predict significant target-dependent deviations from the correlation limit approximation for $∣ P ∣ > ∣ Δ ∣$ and $∣ P ∣ ≲ Q_{s}$ , which offers a straightforward test of gluon saturation and access to multi-gluon distributions at a future electron ion collider.
Comments:
9 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1912.05586 [pdf]
PRL(2020)·79 citations
02
[Submitted on 11 Dec 2019]
Variational and parquet-diagram calculations for neutron matter. I. Structure and Energetics
E.Krotscheck · J. Wang
We develop the variational/parquet diagram approach to the structure of nuclear systems with strongly state-dependent interactions. For that purpose, we combine ideas of the general Jastrow-Feenberg variational method and the local parquet-diagram theory for bosons with state-dependent interactions (R. A. Smith and A. D. Jackson, Nucl. Phys. {\bf 476}, 448 (1988)). The most tedious aspect of variational approaches, namely the symmetrization of an operator dependent variational wave function, is thereby avoided. We carry out calculations for neutron matter interacting via the Reid and Argonne $v_{6}$ models of the nucleon-nucleon interaction. While the equation of state is a rather robust quantity that comes out reasonably well even in very simplistic approaches, we show that effective interactions, which are the essential input for calculating dynamic properties, depend sensitively on the quality of the treatment of the many-body problem.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1912.05685 [pdf]
PRC(2020)·8 citations
03
[Submitted on 12 Dec 2019]
Properties of exotic nuclei and their linkage to the nucleonic interaction
H. Nakada
The structure of exotic nuclei sheds new light on the linkage of the nuclear structure to the nucleonic interaction. The self-consistent mean-field (SCMF) theories are useful to investigate this linkage, which are applicable to many nuclei covering almost the whole range of the nuclear chart without artificial truncation of model space. For this purpose, it is desired to develop effective interaction for the SCMF calculations well connected to the bare nucleonic interaction. Focusing on ground-state properties, I show results of the SCMF calculations primarily with the M3Y-type semi-realistic interaction, M3Y-P6 and M3Y-P6a to be precise, and discuss in detail how the nucleonic interaction affects structure of nuclei including those far off the $β$ -stability.
Comments:
To be published in IJMPE (as a review article)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1912.05756 [pdf]
IJMPE(2020)·22 citations
04
[Submitted on 12 Dec 2019]
Issues with Search for Critical Point in QCD with Relativistic Heavy Ion Collisions
Masayuki Asakawa🇯🇵 · Masakiyo Kitazawa🇯🇵 · Berndt Müller🇺🇸
A systematic search for a critical point in the phase diagram of QCD matter is underway at the Relativistic Heavy Ion Collider (RHIC) and is planned at several future facilities. Its existence, if confirmed, and its location will greatly enhance our understanding of QCD. In this note we emphasize several important issues that are often not fully recognized in theoretical interpretations of experimental results relevant to the critical point search. We discuss ways in which our understanding on these issues can be improved.
Comments:
The title has been changed. One reference has been added. Physical Review C in press
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1912.05840 [pdf]
PRC(2020)·18 citations
05
[Submitted on 12 Dec 2019]
Rate for Laser-Induced Nuclear Dipole Absorption
Adriana Pálffy🇩🇪 · Paul-Gerhard Reinhard🇩🇪 · Hans A. Weidenmüller🇩🇪
Using the Brink-Axel hypothesis we derive the rate $R$ for nuclear dipole excitation by a laser pulse carrying $N ≫ 1$ photons with average energy $ℏ ω_{0} \approx 5$ MeV. As expected $R \propto (ℏ ω_{0})^{3}$ . The rate is also proportional to the aperure $α$ of the laser pulse. Perhaps less expected is the fact that $R \propto N$ , irrespective of the degree of coherence of the laser pulse. The expression for $R$ , derived for a nearly stationary laser pulse, is valid also for short times and can, thus, be used in simulations via rate equations of multiple nuclear dipole excitations by a single pulse. The explicit dependence of $R$ on the parameters of the laser pulse and on nuclear parameters given in the paper should help to optimize experiments on laser-nucleus reactions.
Comments:
12 pages, v2 slightly modified to match the published version
Subjects:
Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
1912.05991 [pdf]
PRC(2020)·2 citations
06
[Submitted on 12 Dec 2019]
Implementing chiral three-body forces in terms of medium-dependent two-body forces
Jeremy W. Holt · Mamiya Kawaguchi · Norbert Kaiser
Three-nucleon (3N) forces are an indispensable ingredient for accurate few-body and many-body nuclear structure and reaction theory calculations. While the direct implementation of chiral 3N forces can be technically very challenging, a simpler approach is given by employing instead a medium-dependent NN interaction V_med that reflects the physics of three-body forces at the two-body normal-ordered approximation. We review the derivation and construction of V_med from the chiral 3N interaction at next-to-next-to-leading order (N2LO), consisting of a long-range $2 π$ -exchange term, a mid-range $1 π$ -exchange component and a short-range contact term. Several applications of V_med to the equation of state of cold nuclear and neutron matter, the nucleon single-particle potential in nuclear matter, and the nuclear quasiparticle interaction are discussed. We also explore differences in using local vs. nonlocal regulating functions on 3N forces and make direct comparisons to exact results at low order in perturbation theory expansions for the equation of state and single-particle potential. We end with a discussion and numerical calculation of the in-medium NN potential V_med from the next-to-next-to-next-to-leading order (N3LO) chiral 3N force, which consists of a series of long-range and short-range terms.
Comments:
31 pages, 15 figures, Published in Frontiers in Physics special volume "The Long-Lasting Quest for Nuclear Interactions: The Past, the Present and the Future"
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1912.06055 [pdf]
Front.in Phys.(2020)·25 citations
07
[Submitted on 12 Dec 2019]
Ab initio rotation in 10Be
M. A. Caprio · P. J. Fasano · A. E. McCoy · P. Maris · J. P. Vary
Ab initio theory describes nuclei from a fully microscopic formulation, with no presupposition of collective degrees of freedom, yet signatures of clustering and rotation nonetheless arise. We can therefore look to ab initio theory for an understanding of the nature of these emergent phenomena. To probe the nature of rotation in 10Be, we examine the predicted rotational spectroscopy from no-core configuration interaction (NCCI) calculations with the Daejeon16 internucleon interaction, and find spectra suggestive of coexisting rotational structures having qualitatively different intrinsic deformations: one triaxial and the other with large axial deformation arising primarily from the neutrons.
Comments:
11 pages, 4 figures; contribution to the proceedings of the Third International Workshop "Shapes and Dynamics of Atomic Nuclei: Contemporary Aspects" (SDANCA-19), Sofia, Bulgaria, October 2019, to be published in Bulg. J. Phys
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1912.06082 [pdf]
Bulg.J.Phys.(2019)·5 citations
08
[Submitted on 11 Dec 2019] (cross-list from hep-ph)
Nucleon-to-meson transition distribution amplitudes in impact parameter space
Bernard Pire🇫🇷 · Kirill Semenov-Tian-Shansky🇷🇺 · Lech Szymanowski🇵🇱
Recent analyses of backward meson electroproduction support the validity of a collinear QCD factorization framework for these hard exclusive reactions. This opens a way to the extraction of nucleon-to-meson transition distribution amplitudes (TDAs) from the experimental data. Similarly to the generalized parton distributions, TDAs - after the Fourier transform in the transverse plane - carry valuable information on the transverse location of hadron constituents. We address the properties of integrated nucleon-to-meson TDAs in the impact parameter representation. We argue that the emerging picture provides an intuitive interpretation for the hadron structural information contained in nucleon-to-meson TDAs and allows to study diquark-quark contents of fast moving hadrons in the transverse plane.
Comments:
6 pages, 2 figures. LC2019 - QCD on the light cone: from hadrons to heavy ions, 16-20 September 2019, Ecole Polytechnique, Palaiseau, France
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1912.05165 [pdf]
PoS(2019)·6 citations
09
[Submitted on 11 Dec 2019] (cross-list from hep-ph)
T-dependence of the axion mass when the U_A(1) and chiral symmetry breaking are tied
Dubravko Klabučar🇭🇷 · Davor Horvatić🇭🇷 · Dalibor Kekez🇭🇷
Modulo the scale of spontaneous breaking of Peccei-Quinn symmetry, the axion mass $m_{a} (T)$ is given by the QCD topological susceptibility $χ (T)$ at all temperatures $T$ . From an approach tying the $U_{A} (1)$ and chiral symmetry breaking and getting good $T$ -dependence of $η$ and $η$ mesons, we get $χ (T)$ for an effective Dyson-Schwinger model of nonperturbative QCD. Comparison with lattice results for $χ (T)$ , and thus also for $m_{a} (T)$ , shows good agreement for temperatures ranging from zero up to the double of the chiral restoration temperature $T_{c}$ .
Comments:
appolb.cls, 6 pages, 1 figure, condensed version of the part of arXiv:1909.09879 presented at Excited QCD 2019, to appear in Acta Physica Polonica B Proceedings Supplement
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1912.05619 [pdf]
Acta Phys.Polon.Supp.(2020)·0 citations
10
[Submitted on 12 Dec 2019] (cross-list from astro-ph.HE)
A NICER View of PSR J0030+0451: Millisecond Pulsar Parameter Estimation
Thomas E. Riley🇳🇱 · Anna L. Watts🇳🇱 · Slavko Bogdanov🇺🇸 · Paul S. Ray🇺🇸 · Renee M. Ludlam🇺🇸 · Sebastien Guillot🇫🇷 · Zaven Arzoumanian🇺🇸 · Charles L. Baker🇺🇸 · Anna V. Bilous🇳🇱 · Deepto Chakrabarty🇺🇸 · Keith C. Gendreau🇺🇸 · Alice K. Harding🇺🇸 and 4 other authors
We report on Bayesian parameter estimation of the mass and equatorial radius of the millisecond pulsar PSR J0030 $+$ 0451, conditional on pulse-profile modeling of Neutron Star Interior Composition Explorer (NICER) X-ray spectral-timing event data. We perform relativistic ray-tracing of thermal emission from hot regions of the pulsar's surface. We assume two distinct hot regions based on two clear pulsed components in the phase-folded pulse-profile data; we explore a number of forms (morphologies and topologies) for each hot region, inferring their parameters in addition to the stellar mass and radius. For the family of models considered, the evidence (prior predictive probability of the data) strongly favors a model that permits both hot regions to be located in the same rotational hemisphere. Models wherein both hot regions are assumed to be simply-connected circular single-temperature spots, in particular those where the spots are assumed to be reflection-symmetric with respect to the stellar origin, are strongly disfavored. For the inferred configuration, one hot region subtends an angular extent of only a few degrees (in spherical coordinates with origin at the stellar center) and we are insensitive to other structural details; the second hot region is far more azimuthally extended in the form of a narrow arc, thus requiring a larger number of parameters to describe. The inferred mass $M$ and equatorial radius $R_{eq}$ are, respectively, $1.3 4_{- 0.16}^{+ 0.15}$ M $_{⊙}$ and $12.7 1_{- 1.19}^{+ 1.14}$ km, whilst the compactness $GM / R_{eq} c^{2} = 0.15 6_{- 0.010}^{+ 0.008}$ is more tightly constrained; the credible interval bounds reported here are approximately the $16%$ and $84%$ quantiles in marginal posterior mass.
Comments:
Appears in ApJ Letters Focus Issue on NICER Constraints on the Dense Matter Equation of State; 76 pages, 24 figures, 7 tables, 8 figure sets (available in the online journal or from the authors)
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1912.05702 [pdf]
ApJL(2019)·1829 citations
11
[Submitted on 12 Dec 2019] (cross-list from astro-ph.HE)
A NICER view of PSR J0030+0451: Implications for the dense matter equation of state
G. Raaijmakers🇳🇱 · T. E. Riley🇳🇱 · A. L. Watts🇳🇱 · S. K. Greif🇩🇪 · S. M. Morsink🇨🇦 · K. Hebeler🇩🇪 · A. Schwenk🇩🇪 · T. Hinderer🇳🇱 · S. Nissanke🇳🇱 · S. Guillot🇫🇷 · Z. Arzoumanian🇺🇸 · S. Bogdanov🇺🇸 and 5 other authors
Both the mass and radius of the millisecond pulsar PSR J0030+0451 have been inferred via pulse-profile modeling of X-ray data obtained by NASA's NICER mission. In this Letter we study the implications of the mass-radius inference reported for this source by Riley et al. (2019) for the dense matter equation of state (EOS), in the context of prior information from nuclear physics at low densities. Using a Bayesian framework we infer central densities and EOS properties for two choices of high-density extensions: a piecewise-polytropic model and a model based on assumptions of the speed of sound in dense matter. Around nuclear saturation density these extensions are matched to an EOS uncertainty band obtained from calculations based on chiral effective field theory interactions, which provide a realistic description of atomic nuclei as well as empirical nuclear matter properties within uncertainties. We further constrain EOS expectations with input from the current highest measured pulsar mass; together, these constraints offer a narrow Bayesian prior informed by theory as well as laboratory and astrophysical measurements. The NICER mass-radius likelihood function derived by Riley et al. (2019) using pulse-profile modeling is consistent with the highest-density region of this prior. The present relatively large uncertainties on mass and radius for PSR J0030+0451 offer, however, only a weak posterior information gain over the prior. We explore the sensitivity to the inferred geometry of the heated regions that give rise to the pulsed emission, and find a small increase in posterior gain for an alternative (but less preferred) model. Lastly, we investigate the hypothetical scenario of increasing the NICER exposure time for PSR J0030+0451.
Comments:
Appears in ApJ Letters Focus Issue on NICER Constraints on the Dense Matter Equation of State, 17 pages, 5 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1912.05703 [pdf]
ApJL(2019)·300 citations
12
[Submitted on 12 Dec 2019] (cross-list from astro-ph.HE)
PSR J0030+0451 Mass and Radius from NICER Data and Implications for the Properties of Neutron Star Matter
M. C. Miller🇺🇸 · F. K. Lamb🇺🇸 · A. J. Dittmann🇺🇸 · S. Bogdanov🇺🇸 · Z. Arzoumanian🇺🇸 · K. C. Gendreau🇺🇸 · S. Guillot🇫🇷 · A. K. Harding🇺🇸 · W. C. G. Ho🇺🇸 · J. M. Lattimer🇺🇸 · R. M. Ludlam🇺🇸 · S. Mahmoodifar🇺🇸 and 9 other authors
Neutron stars are not only of astrophysical interest, but are also of great interest to nuclear physicists, because their attributes can be used to determine the properties of the dense matter in their cores. One of the most informative approaches for determining the equation of state of this dense matter is to measure both a star's equatorial circumferential radius $R_{e}$ and its gravitational mass $M$ . Here we report estimates of the mass and radius of the isolated 205.53 Hz millisecond pulsar PSR J0030+0451 obtained using a Bayesian inference approach to analyze its energy-dependent thermal X-ray waveform, which was observed using the Neutron Star Interior Composition Explorer (NICER). This approach is thought to be less subject to systematic errors than other approaches for estimating neutron star radii. We explored a variety of emission patterns on the stellar surface. Our best-fit model has three oval, uniform-temperature emitting spots and provides an excellent description of the pulse waveform observed using NICER. The radius and mass estimates given by this model are $R_{e} = 13.0 2_{- 1.06}^{+ 1.24}$ km and $M = 1.4 4_{- 0.14}^{+ 0.15} M_{⊙}$ (68%). The independent analysis reported in the companion paper by Riley et al. (2019) explores different emitting spot models, but finds spot shapes and locations and estimates of $R_{e}$ and $M$ that are consistent with those found in this work. We show that our measurements of $R_{e}$ and $M$ for PSR J0030 $+$ 0451 improve the astrophysical constraints on the equation of state of cold, catalyzed matter above nuclear saturation density.
Comments:
49 pages, 16 figures, part of The Astrophysical Journal Letters focus issue on the Neutron Star Interior Composition Explorer
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1912.05705 [pdf]
ApJL(2019)·1995 citations
13
[Submitted on 12 Dec 2019] (cross-list from hep-ph)
Quark Transverse Parton Distribution at the Next-to-Next-to-Next-to-Leading Order
Ming-xing Luo🇨🇳 · Tong-Zhi Yang🇨🇳 · Hua Xing Zhu🇨🇳 · Yu Jiao Zhu🇨🇳
We report a calculation of the perturbative matching coefficients for the transverse-momentum-dependent parton distribution functions for quark at the next-to-next-to-next-to-leading order in QCD, which involves calculation of non-standard Feynman integrals with rapidity divergence. We introduce a set of generalized Integration-By-Parts equations, which allows an algorithmic evaluation of such integrals using the machinery of modern Feynman integral calculation.
Comments:
v1:5+19 pages, 2 figures; v2: references added; v3: fig. 3 added. journal version; v4: Coefficient for d33 in (A.13) corrected, fig. 2 updated, ancillary files updated, numerical fitting added
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1912.05778 [pdf]
PRL(2020)·144 citations
14
[Submitted on 12 Dec 2019] (cross-list from hep-ph)
Potential analysis of holographic Schwinger effect in the magnetized background
Zhou-Run Zhu🇨🇳 · De-fu Hou (CCNU)🇨🇳 · Xun Chen🇨🇳
We study the holographic Schwinger effect with magnetic field at RHIC and LHC energies by using the AdS/CFT correspondence. We consider both weak and strong magnetic field cases with $B ≪ T^{2}$ and $B ≫ T^{2}$ solutions respectively. Firstly, we calculate separating length of the particle pairs at finite magnetic field. It is found that for both weak and strong magnetic field solutions the maximum value of separating length decreases with the increase of magnetic field , which can be inferred that the virtual electron-positron pairs become real particles more easily. We also find that the magnetic field reduces the potential barrier and the critical field for the weak magnetic field solution, thus favors the Schwinger effect. With strong magnetic field solution, the magnetic field enhances the Schwinger effect when the pairs are in perpendicular to the magnetic field although the magnetic field increases the critical electric field.
Comments:
21 pages with 9 figures in Revtex; one new section and 4 figures added
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1912.05806 [pdf]
EPJC(2020)·24 citations
15
[Submitted on 12 Dec 2019] (cross-list from nucl-ex)
Jets as precision probes in electron-nucleus collisions at the Electron-Ion Collider
Miguel Arratia🇺🇸 · Youqi Song🇺🇸 · Felix Ringer🇺🇸 · Barbara V. Jacak🇺🇸
We discuss the prospects of using jets as precision probes in electron-nucleus collisions at the future Electron-Ion Collider. Jets produced in deep-inelastic scattering can be calibrated by a measurement of the scattered electron. Such electron-jet "tag and probe" measurements call for an approach that is orthogonal to most HERA jet measurements as well as previous studies of jets at the future EIC. We present observables such as the electron-jet momentum balance, azimuthal correlations and jet substructure, which can provide constraints on the parton transport coefficient in nuclei. We compare simulations and analytical calculations and provide estimates of the expected medium effects. Implications for detector design at the future EIC are discussed.
Comments:
published version
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1912.05931 [pdf]
PRC(2020)·66 citations
16
[Submitted on 12 Dec 2019] (cross-list from nucl-ex)
$^{78}$ Ni revealed as a doubly magic stronghold against nuclear deformation
R. Taniuchi · C. Santamaria🇫🇷 · P. Doornenbal · A. Obertelli🇫🇷 · K. Yoneda · G. Authelet🇫🇷 · H. Baba · D. Calvet🇫🇷 · F. Château🇫🇷 · A. Corsi🇫🇷 · A. Delbart🇫🇷 · J.-M. Gheller🇫🇷 and 59 other authors
Nuclear magic numbers, which emerge from the strong nuclear force based on quantum chromodynamics, correspond to fully occupied energy shells of protons, or neutrons inside atomic nuclei. Doubly magic nuclei, with magic numbers for both protons and neutrons, are spherical and extremely rare across the nuclear landscape. While the sequence of magic numbers is well established for stable nuclei, evidence reveals modifications for nuclei with a large proton-to-neutron asymmetry. Here, we provide the first spectroscopic study of the doubly magic nucleus $^{78}$ Ni, fourteen neutrons beyond the last stable nickel isotope. We provide direct evidence for its doubly magic nature, which is also predicted by ab initio calculations based on chiral effective field theory interactions and the quasi-particle random-phase approximation. However, our results also provide the first indication of the breakdown of the neutron magic number 50 and proton magic number 28 beyond this stronghold, caused by a competing deformed structure. State-of-the-art phenomenological shell-model calculations reproduce this shape coexistence, predicting further a rapid transition from spherical to deformed ground states with $^{78}$ Ni as turning point.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1912.05978 [pdf]
Nature(2019)·182 citations
17
[Submitted on 12 Dec 2019] (cross-list from nucl-ex)
Comment on "Direct Observation of Proton Emission in $^{11}$ Be"
H.O.U. Fynbo · Z. Janas · C. Mazzocchi · M. Pfuetzner · J. Refsgaard · K. Riisager · N. Sokolowska
We argue that conclusions of [PRL 123, 082501 (2019)] are incorrect. The authors present the direct observation of beta-delayed proton emission in the beta decay of 11Be. From the determined branching ratio for this process and from the energy spectrum of emitted protons the existence of a so far unobserved narrow resonance in 11Be was deduced. The given beta strength for the transition to this state is however wrong. In addition, we show that the combination of peak position and branching ratio is in strong disagreement with models considered by the authors. Furthermore, we identify several deficiencies in the analysis, and we provide possible sources of background, that could explain the error.
Comments:
1 page, 1 figure
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1912.06064 [pdf]
3 citations

Affiliations

first authorsco-authorsvia INSPIRE