Nuclear Theory·nucl-th

Friday·April 17, 2020

10 papers—3 primary·7 cross-listed

04
[Submitted on 15 Apr 2020] (cross-list from nucl-ex)
$^{12}$ C(e,e'pN) Measurements of Short Range Correlations in the Tensor-to-Scalar Interaction Transition Region
I. Korover · J. R. Pybus · A. Schmidt · F. Hauenstein · M. Duer · O. Hen · E. Piasetzky · L.B. Weinstein · D.W. Higinbotham · the CLAS Collaboration
High-momentum configurations of nucleon pairs at short-distance are probed using measurements of the $^{12}$ C $(e, e^{'} p)$ and $^{12}$ C $(e, e^{'} pN)$ reactions (where $N$ is either $n$ or $p$ ), at high- $Q^{2}$ and $x_{B} > 1.1$ . The data span a missing-momentum range of 300--1000 MeV/c and are predominantly sensitive to the transition region of the strong nuclear interaction from a Tensor to Scalar interaction. The data are well reproduced by theoretical calculations using the Generalized Contact Formalism with both chiral and phenomenological nucleon-nucleon ( $N N$ ) interaction models. This agreement suggests that the measured high missing-momentum protons up to $1000$ MeV/c predominantly belong to short-ranged correlated (SRC) pairs. The measured $^{12}$ C $(e, e^{'} pN)$ / $^{12}$ C $(e, e^{'} p)$ and $^{12}$ C $(e, e^{'} pp)$ / $^{12}$ C $(e, e^{'} p n)$ cross-section ratios are consistent with a decrease in the fraction of proton-neutron SRC pairs and increase in the fraction of proton-proton SRC pairs with increasing missing momentum. This confirms the transition from an isospin-dependent tensor $N N$ interaction at $\sim 400$ MeV/c to an isospin-independent scalar interaction at high-momentum around $\sim 800$ MeV/c as predicted by theoretical calculation.
Comments:
Accepted for publication in Physics Letters B. 7 pages, 3 figures, and online supplementary materials
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2004.07304 [pdf]
PLB(2021)·48 citations
05
[Submitted on 16 Apr 2020] (cross-list from hep-lat)
Neutrinoless Double Beta Decay from Lattice QCD: The Long-Distance $π^{-} \to π^{+} e^{-} e^{-}$ Amplitude
W. Detmold🇺🇸 · D.J. Murphy🇺🇸
Neutrinoless double beta decay ($ 0 \nu \beta \beta $) is a hypothetical nuclear decay mode with important implications. In particular, observation of this decay would demonstrate that the neutrino is a Majorana particle and that lepton number conservation is violated in nature. Relating experimental constraints on $0 \nu \beta \beta$ decay rates to the neutrino masses requires theoretical input in the form of non-perturbative nuclear matrix elements which remain difficult to calculate reliably. This work marks a first step toward providing a general lattice QCD framework for computing long-distance $0 \nu \beta \beta$ matrix elements in the case where the decay is mediated by a light Majorana neutrino. The relevant formalism is developed and then tested by computing the simplest such matrix element describing an unphysical $ \pi^{-} \rightarrow \pi^{+} e^{-} e^{-} $ transition on a series of domain wall fermion ensembles. The resulting lattice data is then fit to next-to-leading-order chiral perturbation theory, allowing a fully-controlled extraction of the low energy constant governing the transition rate, $g_{\nu}^{\pi \pi}(\mu = 770 \,\, \mathrm{MeV}) = -10.78(12)_{\rm stat}(51)_{\rm sys}$. Finally, future prospects for calculations of more complicated processes, such as the phenomenologically important $n^{0} n^{0} \rightarrow p^{+} p^{+} e^{-} e^{-}$ decay, are discussed.
Comments:
26 pages, 10 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2004.07404 [pdf]
40 citations
06
[Submitted on 16 Apr 2020] (cross-list from hep-ph)
Roper-like resonances with various flavor contents and their two-pion emission decays
A. J. Arifi🇯🇵 · H. Nagahiro🇯🇵 · A. Hosaka🇯🇵 · K. Tanida🇯🇵
We study the three-body decay of the newly observed bottom baryon $Λ_{b}^{*} (6072)$ by LHCb; $Λ_{b}^{*} (6072) \to Λ_{b} π π$ . Its mass about 500 MeV above the ground state $Λ_{b}$ and a broad width imply that the state could be an analogue of the Roper resonance of the nucleon $N (1440)$ . In terms of sequential processes going through $Σ_{b}$ and $Σ_{b}^{*}$ , we find that the observed invariant mass distribution is reproduced assuming its spin and parity $J^{P} = 1/ 2^{+}$ . We discuss that the ratio of the two sequential processes and angular correlation of two pions are useful for the determination of spin and parity. We suggest further studies for the Roper resonance analogue in various flavor contents, raising an interesting and important question in baryon spectroscopy.
Comments:
4 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2004.07423 [pdf]
PRD(2020)·21 citations
07
[Submitted on 16 Apr 2020] (cross-list from hep-ph)
The chiral magnetic effect and the chiral spin symmetry in QCD above Tc
L. Ya. Glozman🇦🇹
The chiral magnetic effect (CME) is an exact statement that connects via the axial anomaly the electric current in a system consisting of interacting fermions and gauge field with chirality imbalance that is put into a strong external magnetic field. Experimental search of the magnetically induced current in QCD in heavy ion collisions above a pseudocritical temperature hints, though not yet conclusive, that the induced current is either small or vanishing. This would imply that the chirality imbalance in QCD above $T_{c}$ that could be generated via topological fluctuations is at most very small. Here we present the most general reason for absence (smallness) of the chirality imbalance in QCD above Tc. It was recently found on the lattice that QCD above Tc is approximately chiral spin (CS) symmetric with the symmetry breaking at the level of a few percent. The CS transformations mix the right- and left-handed components of quarks. Then an exact CS symmetry would require absence of any chirality imbalance. Consequently an approximate CS symmetry admits at most a very small chirality imbalance in QCD above Tc. Hence the absence or smallness of an magnetically induced current observed in heavy ion collisions could be considered as experimental evidence for emergence of the CS symmetry above Tc.
Comments:
9 pp
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2004.07525 [pdf]
1 citation
08
[Submitted on 16 Apr 2020] (cross-list from hep-ph)
Inelasticity resulting from rapidity spectra analysis
Zbigniew Włodarczyk🇵🇱 · Maciej Rybczyński🇵🇱
In this work we study the pseudorapidity spectra o charged particles produced in proton+proton and proton+antiproton interactions in a wide energy range using the non-extensive Tsallis approach. We evaluate the inelasticity coefficients of the discussed reactions which remain approximately independent of the collision energy.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2004.07617 [pdf]
New J.Phys.(2020)·1 citation
09
[Submitted on 16 Apr 2020] (cross-list from astro-ph.HE)
Direct Astrophysical Tests of Chiral Effective Field Theory at Supranuclear Densities
Reed Essick🇺🇸 · Ingo Tews🇺🇸 · Philippe Landry🇺🇸 · Sanjay Reddy🇺🇸 · Daniel E. Holz🇺🇸
Recent observations of neutron stars with gravitational waves and X-ray timing provide unprecedented access to the equation of state (EoS) of cold dense matter at densities difficult to realize in terrestrial experiments. At the same time, predictions for the EoS with reliable uncertainty estimates from chiral effective field theory ( $χ$ EFT) bound our theoretical ignorance. In this work, we analyze astrophysical data using a nonparametric representation of the neutron-star EoS conditioned on $χ$ EFT to directly constrain the underlying physical properties of the compact objects. We discuss how the data alone constrain the EoS at high densities when we condition on $χ$ EFT at low densities. We also demonstrate how to exploit astrophysical data to directly test the predictions of $χ$ EFT for the EoS up to twice nuclear saturation density, and estimate the density at which these predictions might break down. We find that the existence of massive pulsars, gravitational waves from GW170817, and NICER observations of PSR J0030+0451 favor $χ$ EFT predictions for the EoS up to nuclear saturation density over a more agnostic analysis by as much as a factor of 7 for the quantum Monte Carlo (QMC) calculations used in this work. While $χ$ EFT predictions using QMC are fully consistent with gravitational-wave data up to twice nuclear saturation density, NICER observations suggest that the EoS stiffens relative to these predictions at nuclear saturation density. Additionally, we marginalize over the uncertainty in the density at which $χ$ EFT begins to break down, constraining the radius of a $1.4 M_{⊙}$ neutron star to $R_{1.4} = 11.4 0_{- 1.04}^{+ 1.38}$ ( $12.5 4_{- 0.63}^{+ 0.71}$ ) km and the pressure at twice nuclear saturation density to $p (2 n_{sat}) = 14. 2_{- 8.4}^{+ 18.1}$ ( $28. 7_{- 15.0}^{+ 15.3}$ ) MeV/fm $^{3}$ with massive pulsar and gravitational-wave (and NICER) data.
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2004.07744 [pdf]
PRC(2020)·154 citations
10
[Submitted on 16 Apr 2020] (cross-list from hep-ph)
QZE and IZE in a simple approach and the neutron decay
Francesco Giacosa🇵🇱
We discuss a simple and analytically solvable measurement model which describes the famous Quantum Zeno Effect (QZE) and Inverse Zeno Effect (IZE), that correspond to the slow down and to the increase of the decay rate caused by measurements (or, more in general, by the interaction of an unstable state with the detector and the environment). Within this model one can understand quite general features of the QZE and IZE: by considering an unstable quantum state, such as an unstable particle, whose decay width as function of energy is $Γ (ω) = g^{2} ω^{α},$ then -- under quite general assumptions -- the QZE occurs for $α \in (0, 1)$ , while the IZE for $α \in (- \infty, 0) \cup (1, \infty) .$ This result is valid also for more realistic measurement models than the one described in this work. We then apply these considerations to the decay of the neutron, for which $α = 5.$ Hence, the realization of the IZE for the neutron decay (and for the majority of weak decays) is in principle possible. Indeed, trap experiments find a lifetime that is $8.7 \pm 2.1$ s shorter than beam experiments, suggesting that the IZE could have taken place.
Comments:
13 pages. Prepared for the proceedings of the XXVI Cracow Epiphany Conference on LHC Physics: Standard Model and Beyond, 7-10/1/2020, Cracow, Poland
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2004.07772 [pdf]
Acta Phys.Polon.B(2020)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE

12C(e,e'pN) Measurements of Short Range Correlations in the Tensor-to-Scalar Interaction Transition Region

Neutrinoless Double Beta Decay from Lattice QCD: The Long-Distance π−→π+e−e− Amplitude

Roper-like resonances with various flavor contents and their two-pion emission decays

The chiral magnetic effect and the chiral spin symmetry in QCD above Tc

Inelasticity resulting from rapidity spectra analysis

Direct Astrophysical Tests of Chiral Effective Field Theory at Supranuclear Densities

QZE and IZE in a simple approach and the neutron decay

Affiliations

$^{12}$ C(e,e'pN) Measurements of Short Range Correlations in the Tensor-to-Scalar Interaction Transition Region

Neutrinoless Double Beta Decay from Lattice QCD: The Long-Distance $π^{-} \to π^{+} e^{-} e^{-}$ Amplitude