Nuclear Theory·nucl-th

Monday·February 7, 2022

11 papers—1 primary·10 cross-listed

02
Toward the discovery of matter creation with neutrinoless double-beta decay
Matteo Agostini🇬🇧 · Giovanni Benato🇮🇹 · Jason A. Detwiler🇺🇸 · Javier Menéndez🇪🇸 · Francesco Vissani🇮🇹
The discovery of neutrinoless double-beta decay could soon be within reach. This hypothetical ultra-rare nuclear decay offers a privileged portal to physics beyond the Standard Model of particle physics. Its observation would constitute the discovery of a matter-creating process, corroborating leading theories of why the universe contains more matter than antimatter, and how forces unify at high energy scales. It would also prove that neutrinos and anti-neutrinos are not two distinct particles, but can transform into each other, with their mass described by a unique mechanism conceived by Majorana. The recognition that neutrinos are not massless necessitates an explanation and has boosted interest in neutrinoless double-beta decay. The field stands now at a turning point. A new round of experiments is currently being prepared for the next decade to cover an important region of parameter space. In parallel, advances in nuclear theory are laying the groundwork to connect the nuclear decay with the underlying new physics. Meanwhile, the particle theory landscape continues to find new motivations for neutrinos to be their own antiparticle. This review brings together the experimental, nuclear theory, and particle theory aspects connected to neutrinoless double-beta decay, to explore the path toward - and beyond - its discovery.
↳ hep-exhep-phhep-thnucl-ex+1RMP(2023)·433 citations
03
A Smörgåsbord of Skyrmions
Sven Bjarke Gudnason🇨🇳 · Chris Halcrow🇬🇧
We study static solutions of the standard Skyrme model with a pion mass. Using approximately $1 0^{5}$ pseudo-random initial configurations made of single Skyrmions in the non-symmetrized product Ansatz and an automatic detection of repeated solutions, we find 409 local energy minimizers (Skyrmions) of the model with baryon numbers 1 through 16, of which 383 are new. In particular, we find new solutions for baryon numbers 5, 8, 9, 10, 11, 12, 13, 14, 15, and 16. Our results for the number of solutions per baryon number suggest that this number could grow either polynomially or exponentially. We identify new families of solutions: sheets of Skyrmions in synchronized and antisynchronized hexagonal layers (which we call graphene); chains of 2- and 3-tori; chain-like solutions containing a hinge and many clustered Skyrmions. Contrary to common lore, only the $B = 12$ global energy minimizer is made of alpha particles or some chunk of a cubic crystal, whereas the $B = 9, 11, 14, 15$ minimizers contain the $B = 7$ icosahedrally symmetric Skyrmion as a component. The $B = 10, 13, 16$ are symmetric graphene-like solutions. We find $B = 5$ and $B = 8$ minimizers with numerically indistinguishable energies. The $B = 8$ candidates are the chain of two cubes, which is a chunk of the cubic Skyrme crystal and the fullerene-type ball found originally by the rational map approximation. The $B = 5$ global minimizer is either the well-known $D_{2 d}$ symmetric fullerene or a new $C_{2 v}$ symmetric solution. Finally, our findings show a large number of solutions have no discrete symmetries or just one symmetry, contrary to the common lore that Skyrmions are highly symmetric configurations.
↳ hep-thnucl-thJHEP(2022)·26 citations
04
A Challenge for Discrimination of Color-Singlet versus Color-Octet Quarkonium Production
Andrew J. Larkoski🇺🇸
The precise mechanism for production of quarkonium at hadron colliders is still an open question. Within non-relativistic quantum chromodynamics, quarkonium production cross sections can be factorized into short-distance, perturbative contributions and universal, non-perturbative, long-distance matrix elements, and then summed over quantum numbers of the heavy quark pair. In principle, at short-distances, the heavy quark pair can be either in a color-singlet or color-octet state, and it is desirable to establish the relative contributions to compare with data and to make predictions in different experimental environments. From the explicit form of the lowest-order perturbative matrix elements for color-singlet and color-octet production, we show that the structure of the optimal observable for discrimination on phase space, the likelihood ratio, has strong dependence on the angular momentum state of the heavy quark pair. This presents an obstruction for construction of a single, robust discrimination observable that can be applied to production of an arbitrary quarkonium state.
↳ hep-phhep-exnucl-exnucl-th1 citation
05
Thermal effects on tidal deformability in the last orbits of an inspiraling binary neutron star system
A. Kanakis-Pegios · P.S. Koliogiannis · Ch.C. Moustakidis
The study of binary neutron stars mergers by the detection of the emitted gravitational waves is one of the most promised tools to study the properties of dense nuclear matter at high densities. It is worth claiming that, at the moment, strong evidence that the temperature of the stars is zero during the last orbits before coalescing, does not exist. Nevertheless, theoretical studies suggest that the temperature concerning the inspiral phase, could reach even a few MeV. According to the main theory, tides transfer mechanical energy and angular momentum to the star at the expense of the orbit, where friction within the star converts the mechanical energy into heat. During the inspiral, these effects are potentially detectable. Different treatments have been used to estimate the transfer of the mechanical energy and the size of the tidal friction, leading to different conclusions about the importance of pre-merger tidal effects. The present work is dedicated to the study of the effect of temperature on the tidal deformability of neutron stars during the inspiral of a neutron star system just before the merger. We applied a class of hot equations of state, both isothermal and adiabatic, originated from various nuclear models. We found that even for low values of temperature ( $T < 1$ MeV), the effects on the basic ingredients of tidal deformability are not negligible. On the other hand, in the case of the adiabatic star, the thermal effects on tidal deformability remain imperceptible, up to the value $S = 0.2 k_{B}$ . According to the main finding, the effect of the temperature on the tidal deformability is indistinguishable. The consequences of the above result are discussed and analyzed.
↳ astro-ph.HEnucl-thPLB(2022)·11 citations
06
Collective neutrino oscillations with tensor networks using a time-dependent variational principle
Michael J. Cervia🇺🇸 · Pooja Siwach🇺🇸 · Amol V. Patwardhan🇺🇸 · A. B. Balantekin🇺🇸 · S. N. Coppersmith🇺🇸 · Calvin W. Johnson🇺🇸
If a system of flavor-oscillating neutrinos is at high enough densities that neutrino-neutrino coherent forward scatterings are non-negligible, the system becomes a time-dependent many-body problem. An important and open question is whether the flavor evolution is sufficiently described by a mean-field approach or can be strongly affected by correlations arising from two-body interactions in the neutrino Hamiltonian, as measured by nontrivial quantum entanglement. Numerical computations of the time evolution of many-body quantum systems are challenging because the size of the Hilbert space scales exponentially with the number of particles N in the system. Thus, it is important to investigate approximate but beyond-mean-field numerical treatments at larger values of N. Here we investigate the efficacy of tensor network methods to calculate the time evolution of interacting neutrinos at larger values of N than are possible with conventional methods. In particular, we introduce the use of time-dependent variational principle methods to address the long-range (in momentum space) interactions of the neutrino Hamiltonian when including many distinct vacuum oscillation frequencies. We also define new error measures based upon the instantaneously conserved charge operators known for this Hamiltonian to determine validity of large-N tensor network calculations.
↳ hep-phnucl-thquant-phPRD(2022)·46 citations
07
Rotationally-Invariant Circuits: Universality with the exchange interaction and two ancilla qubits
Iman Marvian🇺🇸 · Hanqing Liu🇺🇸 · Austin Hulse🇺🇸
Universality of local unitary transformations is one of the cornerstones of quantum computing with many applications and implications that go beyond this field. However, it has been recently shown that this universality does not hold in the presence of continuous symmetries: generic symmetric unitaries on a composite system cannot be implemented, even approximately, using local symmetric unitaries on the subsystems [I. Marvian, Nature Physics (2022)]. In this work, we study qubit circuits formed from k-local rotationally-invariant unitaries and fully characterize the constraints imposed by locality on the realizable unitaries. We also present an interpretation of these constraints in terms of the average energy of states with a fixed angular momentum. Interestingly, despite these constraints, we show that, using a pair of ancilla qubits, any rotationally-invariant unitary can be realized with the Heisenberg exchange interaction, which is 2-local and rotationally-invariant. We also show that a single ancilla is not enough to achieve universality. Finally, we discuss applications of these results for quantum computing with semiconductor quantum dots, quantum reference frames, and resource theories.
↳ quant-phcond-mat.str-elhep-thmath-ph+2PRL(2024)·29 citations
08
In-flight production of an isomeric beam of $^{16}$ N
C. R. Hoffman · T. L. Tang · M. Avila · Y. Ayyad · K. W. Brown · J. Chen · K. A. Chipps · H. Jayatissa · B. P. Kay · C. Müller-Gatermann · H. J. Ong · J. Song · G. L. Wilson
An in-flight beam of $^{16}$ N was produced via the single-neutron adding ( $d$ , $p$ ) reaction in inverse kinematics at the recently upgraded Argonne Tandem Linear Accelerator System (ATLAS) in-flight system. The amount of the $^{16}$ N beam which resided in its excited 0.120-MeV $J^{π} = 0^{-}$ isomeric state (T $_{1/2} \approx 5$ $μ$ s) was determined to be 40(5)% at a reaction energy of 7.9(3) MeV/ $u$ , and 24(2)% at a reaction energy of 13.2(2) MeV/ $u$ . The isomer measurements took place at an experimental station $\approx 30$ m downstream of the production target and utilized an Al beam-stopping foil and a HPGe Clover detector. Composite $^{16}$ N beam rate determinations were made at the experimental station and the focal plane of the Argonne in-flight radioactive ion-beam separator (RAISOR) with Si $Δ$ E-E telescopes. A Distorted Wave Born Approximation (DWBA) approach was coupled with the known spectroscopic information on $^{16}$ N in order to estimate the relative $^{16}$ N isomer yields and composite $^{16}$ N beam rates. In addition to the observed reaction-energy dependence of the isomer fraction, a large sensitivity to angular acceptance of the recoils was also observed.
↳ physics.ins-detnucl-exnucl-thNucl.Instrum.Meth.A(2022)·11 citations
09
Bayesian inference of the fluctuating proton shape
Heikki Mäntysaari🇫🇮 · Björn Schenke🇺🇸 · Chun Shen🇺🇸 · Wenbin Zhao🇺🇸
Using Bayesian inference, we determine probabilistic constraints on the parameters describing the fluctuating structure of protons at high energy. We employ the color glass condensate framework supplemented with a model for the spatial structure of the proton, along with experimental data from the ZEUS and H1 Collaborations on coherent and incoherent diffractive $J / ψ$ production in e+p collisions at HERA. This data is found to constrain most model parameters well. This work sets the stage for future global analyses, including experimental data from e+p, p+p, and p+A collisions, to constrain the fluctuating structure of nucleons along with properties of the final state.
↳ hep-phnucl-thPLB(2022)·59 citations
10
Two-current transition amplitudes with two-body final states
Keegan H. Sherman🇺🇸 · Felipe G. Ortega-Gama🇺🇸 · Raúl A. Briceño🇺🇸 · Andrew W. Jackura🇺🇸
We derive the on-shell form of amplitudes containing two external currents with a single hadron in the initial state and two hadrons in the final state, denoted as $1 + J \to 2 + J$ . This class of amplitude is relevant in precision tests of the Standard Model as well as for exploring the structure of excited states in the QCD spectrum. We present a model-independent description of the amplitudes where we sum to all orders in the strong interaction. From this analytic form we are able to extract transition and elastic resonance form factors consistent with previous work as well as a novel Compton-like amplitude coupling a single particle state to a resonance. The results also hold for reactions where the one-particle state is replaced with the vacuum, namely $J \to 2 + J$ amplitudes. We also investigate constraints placed upon the formalism for the case of a conserved vector current in the form of the Ward-Takahashi identity. The formalism presented here is valid for currents of arbitrary Lorentz structure and quantum numbers with spinless hadrons where any number of two-particle intermediate channels may be open. When combined with the appropriate finite-volume framework, this work facilitates the extraction of physical observables from this class of amplitudes via lattice QCD calculations.
↳ hep-lathep-phnucl-thPRD(2022)·14 citations
11
Observing true tauonium via two-photon fusion at $e^{+} e^{-}$ and hadron colliders
David d'Enterria🇨🇭 · Hua-Sheng Shao🇫🇷
The feasibility of observing true tauonium, the bound state of two tau leptons, $T_{0} \equiv (τ^{+} τ^{-})_{0}$ , via photon-photon collisions at $e^{+} e^{-}$ colliders and at the LHC, is studied. The production cross sections of the process $γ γ \to T_{0} \to γ γ$ -- as well as those of all relevant backgrounds: spin-0 and 2 charmonium resonances decaying to diphotons, and light-by-light scattering -- are computed in the equivalent photon approximation for $e^{+} e^{-}$ collisions at BES III ( $s = 3.8$ GeV), Belle II ( $s = 10.6$ GeV), and FCC-ee ( $s = 91.2$ GeV), as well as for ultraperipheral p-p, p-Pb, and Pb-Pb collisions at the LHC. Despite small $T_{0}$ production cross sections and a final state swamped by decays from overlapping pseudoscalar and tensor charmonium states -- the $χ_{c2}$ , $η_{c} (2S)$ , and $χ_{c0}$ states have masses only 2.5, 84, and 139 MeV away, respectively, from the $T_{0}$ peak -- evidence and observation of the ground state of the heaviest leptonium appears feasible at Belle II and FCC-ee, respectively, with in-situ high-precision measurements of the irreducible backgrounds.
↳ hep-phhep-exnucl-exnucl-thPRD(2022)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE