Nuclear Theory·nucl-th

Friday·December 22, 2017

13 papers—5 primary·8 cross-listed

01
Spin-dependent distribution functions for relativistic hydrodynamics of spin-1/2 particles
Wojciech Florkowski🇵🇱 · Bengt Friman🇩🇪 · Amaresh Jaiswal🇮🇳 · Radoslaw Ryblewski🇵🇱 · Enrico Speranza🇩🇪
Recently advocated expressions for the phase-space dependent spin-1/2 density matrices of particles and antiparticles are analyzed in detail and reduced to the forms linear in the Dirac spin operator. This allows for a natural determination of the spin polarization vectors of particles and antiparticles by the trace of products of the spin density matrices and the Pauli matrices. We demonstrate that the total spin polarization vector obtained in this way agrees with the Pauli-Lubanski four-vector, constructed from an appropriately chosen spin tensor and boosted to the particle rest frame. We further show that several forms of the spin tensor used in the literature give the same Pauli-Lubanski four-vector.
nucl-thPRD(2018)·146 citations
02
Modification of $Δ (1232)$ in the neutrino nucleus reaction
Swapan Das🇮🇳
The remarkable observations in the pion induced and charge exchange reactions on a nucleus are the significant shift and broadening of the $Δ (1232)$ -peak relative to free pion nucleon scattering. For the forward going massless leptons, the weak process $(ν_{l}, l)$ on a nucleon, according to Adler's partially conserved axial current theorem, is connected to the pion nucleon scattering. This mechanism is also applicable to the nucleus. Therefore, the modification of the $Δ$ -peak in a nucleus can be seen in the $(ν_{l}, l)$ reaction since it is connected to the pion nucleus scattering. To investigate this issue quantitatively, the double differential cross sections of the forward going ejectile $l$ energy distribution in the $(ν_{l}, l)$ reaction are calculated in the $Δ$ -excitation region for both proton and nucleus. The measured pion nucleon and pion nucleus scattering cross sections in the quoted energy region are used in these reactions as input. Since the $(ν_{l}, l)$ reaction is connected to the pion induced scattering, the features of the previous reaction is shown analogous to those of the later.
nucl-thnucl-exActa Phys.Polon.B(2017)·0 citations
03
Shadowing in the low energy photonuclear reaction
Swapan Das🇮🇳
The photonuclear reaction in the multi-GeV region occurs because of the electromagnetic and hadronic interaction. The later originates due to the hadronic fluctuation, i.e., vector meson, of the photon. The total cross section of the reaction is shadowed because of the vector meson nucleus (hadronic) interaction. To estimate it quantitatively, the cross section of the photonuclear reaction was calculated in the low energy region ( $\sim 1 - 3$ GeV) using simple vector meson dominance (SVMD) model, i.e., the low lying vector mesons ( $ρ^{0}$ , $ω$ and $ϕ$ mesons) were considered. The nuclear shadowing is reinvestigated using generalized vector meson (GVMD) model, where the higher $ρ$ meson effective state ( $ρ^{'}$ meson) is taken into account along with the low lying vector mesons. Using GVMD model, the shadowing and the total cross section of the photonuclear reaction are calculated in the above mentioned energy region. The calculated results have been compared with the measured spectra.
nucl-thnucl-exPRC(2017)·3 citations
04
Eta-mesic nuclei
A. Cieply🇨🇿 · J. Mares🇨🇿 · M. Schaefer🇨🇿 · N. Barnea🇮🇱 · B. Bazak🇮🇱 · E. Friedman🇮🇱 · A. Gal🇮🇱
In this contribution we report on theoretical studies of $η$ nuclear quasi-bound states in few- and many-body systems performed recently by the Jerusalem-Prague Collaboration [1-5]. Underlying energy-dependent $η N$ interactions are derived from coupled-channel models that incorporate the $N^{*} (1535)$ resonance. The role of self-consistent treatment of the strong energy dependence of subthreshold $η N$ amplitudes is discussed. Quite large downward energy shift together with rapid decrease of the $η N$ amplitudes below threshold result in relatively small binding energies and widths of the calculated $η$ nuclear bound states. We argue that the subthreshold behavior of $η N$ scattering amplitudes is crucial to conclude whether $η$ nuclear states exist, in which nuclei the $η$ meson could be bound and if the corresponding widths are small enough to allow detection of these $η$ nuclear states in experiment.
nucl-thPoS(2018)·1 citation
05
D mesons in strongly magnetized asymmetric nuclear matter
P. Sushruth Reddy🇮🇳 · C. S. Amal Jahan🇮🇳 · Nikhil Dhale🇮🇳 · Amruta Mishra🇮🇳 · Juergen Schaffner-Bielich
The medium modifications of the open charm mesons ( $D$ and $D ˉ$ ) are studied in isospin asymmetric nuclear matter in the presence of strong magnetic fields, using a chiral effective model. The mass modifications of these mesons in the effective hadronic model, arise due to their interactions with the protons, neutrons and the scalar mesons (non-strange isoscalar $σ$ , strange isoscalar, $ζ$ and non-strange isovector, $δ$ ), in the magnetized nuclear matter. In the presence of magnetic field, for the charged baryon, i.e., the proton, the number density as well as the scalar density have contributions due to the summation over the Landau energy levels. For a given value of the baryon density, $ρ_{B}$ , and isospin asymmetry, the scalar fields are solved self consistently from their coupled equations of motion. The modifications of the masses of the $D$ and $D ˉ$ mesons are calculated, from the medium modifications of the scalar fields and the nucleons. The effects of the anomalous magnetic moments of the nucleons on the masses of the open charm mesons are also investigated in the present work. The effects of isospin asymmetry as well as of the anomalous magnetic moments are observed to be prominent at high densities for large values of magnetic fields.
nucl-thhep-phPRC(2018)·54 citations
06
The charming beauty of the strong interaction
Laura Tolos🇩🇪
Charmed and beauty hadrons in matter are discussed within a unitarized coupled-channel model consistent with heavy-quark spin symmetry. We analyse the formation of D-mesic states as well as the propagation of charmed and beauty hadrons in heavy-ion collisions from LHC to FAIR energies.
↳ hep-phhep-exnucl-th0 citations
07
Resummed Photon Spectra for WIMP Annihilation
Matthew Baumgart🇺🇸 · Timothy Cohen🇺🇸 · Ian Moult🇺🇸 · Nicholas L. Rodd🇺🇸 · Tracy R. Slatyer🇺🇸 · Mikhail P. Solon🇺🇸 · Iain W. Stewart🇺🇸 · Varun Vaidya🇺🇸
We construct an effective field theory (EFT) description of the hard photon spectrum for heavy WIMP annihilation. This facilitates precision predictions relevant for line searches, and allows the incorporation of non-trivial energy resolution effects. Our framework combines techniques from non-relativistic EFTs and soft-collinear effective theory (SCET), as well as its multi-scale extensions that have been recently introduced for studying jet substructure. We find a number of interesting features, including the simultaneous presence of SCET $_{I}$ and SCET $_{II}$ modes, as well as collinear-soft modes at the electroweak scale. We derive a factorization formula that enables both the resummation of the leading large Sudakov double logarithms that appear in the perturbative spectrum, and the inclusion of Sommerfeld enhancement effects. Consistency of this factorization is demonstrated to leading logarithmic order through explicit calculation. Our final result contains both the exclusive and the inclusive limits, thereby providing a unifying description of these two previously-considered approximations. We estimate the impact on experimental sensitivity, focusing for concreteness on an SU(2) $_{W}$ triplet fermion dark matter - the pure wino - where the strongest constraints are due to a search for gamma-ray lines from the Galactic Center. We find numerically significant corrections compared to previous results, thereby highlighting the importance of accounting for the photon spectrum when interpreting data from current and future indirect detection experiments.
↳ hep-phastro-ph.COastro-ph.HEnucl-thJHEP(2018)·73 citations
08
Quantized Skyrmions from SU(4) Weight Diagrams
C. J. Halcrow🇨🇳 · N. S. Manton🇬🇧 · J. I. Rawlinson🇬🇧
Starting from solutions of the lightly-bound Skyrme model, we construct many new Skyrmion solutions of the standard Skyrme model with tetrahedral or octahedral symmetry. These solutions are closely related to weight diagrams of the group SU(4), which enables us to systematically derive some geometric and energetic properties of the Skyrmions, up to baryon number 85. We discuss the rigid body quantization of these Skyrmions, and compare the results with properties of a selection of observed nuclei.
↳ hep-thnucl-thPRC(2018)·5 citations
09
Symmetry Realization via a Dynamical Inverse Higgs Mechanism
Ira Z. Rothstein🇺🇸 · Prashant Shrivastava🇺🇸
The Ward identities associated with spontaneously broken symmetries can be saturated by Goldstone bosons. However, when space-time symmetries are broken, the number of Goldstone bosons necessary to non-linearly realize the symmetry can be less than the number of broken generators. The loss of Goldstones may be due to a redundancy or the generation of a gap. This phenomena is called an Inverse Higgs Mechanism (IHM). However, there are cases when a Goldstone boson associated with a broken generator does not appear in the low energy theory despite the lack of the existence of an associated IHM. In this paper we will show that in such cases the relevant broken symmetry can be realized, without the aid of an associated Goldstone, if there exists a proper set of operator constraints, which we call a Dynamical Inverse Higgs Mechanism (DIHM). We consider the spontaneous breaking of boosts, rotations and conformal transformations in the context of Fermi liquids, finding three possible paths to symmetry realization: pure Goldstones, no Goldstones and DIHM, or some mixture thereof. We show that in the two dimensional degenerate electron system the DIHM route is the only consistent way to realize spontaneously broken boosts and dilatations, while in three dimensions these symmetries could just as well be realized via the inclusion of non-derivatively coupled Goldstone bosons. We have present the action, including the leading order non-linearities, for the rotational Goldstone (angulon), and discuss the constraint associated with the possible DIHM that would need to be imposed to remove it from the spectrum. Finally we discuss the conditions under which Goldstone bosons are non-derivatively coupled, a necessary condition for the existence of a Dynamical Inverse Higgs Constraint (DIHC), generalizaing the results for Vishwanath and Wantanabe.
↳ hep-thcond-mat.str-elhep-phnucl-thJHEP(2018)·27 citations
10
Symmetry Obstruction to Fermi Liquid Behavior in the Unitary Limit
Ira Z. Rothstein🇺🇸 · Prashant Shrivastava🇺🇸
We show that a Fermi gas, in three dimensions, at temperatures above the superconducting phase transition but below the Fermi temperature, can not be described by Fermi Liquid Theory (FLT) in the unitary limit where the scattering length diverges. The result follows by showing that the there are no effective field theory descriptions that both behave like a Fermi liquid and properly non-linearly realize the spontaneously broken boost and conformal invariance of the system.
↳ cond-mat.str-elhep-phhep-thnucl-thPRB(2019)·23 citations
11
Towards a new paradigm for heavy-light meson spectroscopy
Meng-Lin Du🇩🇪 · Miguel Albaladejo🇪🇸 · Pedro Fernandez-Soler🇪🇸 · Feng-Kun Guo🇨🇳 · Christoph Hanhart🇩🇪 · Ulf-G. Meißner🇩🇪 · Juan Nieves🇪🇸 · De-Liang Yao🇪🇸
Since 2003 many new hadrons, including the lowest-lying positive-parity charm-strange mesons $D_{s 0}^{*} (2317)$ and $D_{s 1} (2460)$ , were observed that do not conform with quark model expectations. It was recently demonstrated that various puzzles in the charm meson spectrum find a natural resolution, if the SU(3) multiplets for the lightest scalar and axial-vector states, amongst them the $D_{s 0}^{*} (2317)$ and the $D_{s 1} (2460)$ , owe their existence to the nonperturbative dynamics of Goldstone-Boson scattering off $D_{(s)}$ and $D_{(s)}^{*}$ mesons. Most importantly the ordering of the lightest strange and nonstrange scalars becomes natural. In this work we demonstrate for the first time that this mechanism is strongly supported by the recent high quality data on the $B^{-} \to D^{+} π^{-} π^{-}$ provided by the LHCb experiment. This implies that the lowest quark-model positive-parity charm mesons, together with their bottom counterparts, if realized in nature, do not form the ground-state multiplet. This is similar to the pattern that has been established for the scalar mesons made from light up, down and strange quarks, where the lowest multiplet is considered to be made of states not described by the quark model. In a broader view, the hadron spectrum must be viewed as more than a collection of quark model states.
↳ hep-phhep-exhep-latnucl-thPRD(2018)·117 citations
12
Mass sensitivity of the three-flavor chiral phase transition
Simon Resch🇩🇪 · Fabian Rennecke🇺🇸 · Bernd-Jochen Schaefer🇩🇪
The mass sensitivity of the chiral phase transition of QCD with and without axial $U_{A} (1)$ -symmetry breaking at vanishing and finite quark chemical potential is investigated. To focus on the low-energy sector of QCD, a quark-meson model with three dynamical quark flavors is employed. Non-perturbative quantum fluctuations are taken into account with the functional renormalization group. The inherent ambiguities in fixing the low-energy model parameters away from the physical mass point and their consequences for spontaneous chiral symmetry breaking are discussed in detail and a heuristic parameter fixing scheme motivated by chiral perturbation theory is proposed. The influence of vacuum and thermal fluctuations of quarks and mesons on the order of the chiral phase transition is additionally assessed with a mean-field analysis.
↳ hep-phhep-thnucl-thPRD(2019)·65 citations
13
Dynamically generated hadronic states in the $K ˉ N$ and $η N$ coupled-channels interactions
Ales Cieply🇨🇿
We compare and review the theoretical predictions for the $K ˉ N$ and $η N$ elastic amplitudes where sizable variations are found among the considered approaches, especially at subthreshold energies relevant for studies of kaonic atoms and meson-nuclear quasi-bound states. Conditions for an appearance of dynamically generated states in meson-baryon multi-channel interactions are established and discussed for the $K ˉ N$ and $η N$ systems.
↳ hep-phnucl-thEPJ Web Conf.(2018)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE