Nuclear Theory·nucl-th

Friday·February 26, 2016

15 papers—7 primary·8 cross-listed

08
[Submitted on 24 Feb 2016] (cross-list from hep-lat)
Remarks on the pion-nucleon sigma-term
Martin Hoferichter🇺🇸 · Jacobo Ruiz de Elvira🇩🇪 · Bastian Kubis🇩🇪 · Ulf-G. Meißner🇩🇪
The pion-nucleon $σ$ -term can be stringently constrained by the combination of analyticity, unitarity, and crossing symmetry with phenomenological information on the pion-nucleon scattering lengths. Recently, lattice calculations at the physical point have been reported that find lower values by about $3 σ$ with respect to the phenomenological determination. We point out that a lattice measurement of the pion-nucleon scattering lengths could help resolve the situation by testing the values extracted from spectroscopy measurements in pionic atoms.
Comments:
5 pages, 2 figures; version published in PLB
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1602.07688 [pdf]
PLB(2016)·77 citations
09
[Submitted on 25 Feb 2016] (cross-list from hep-ph)
Elements of QED-NRQED Effective Field Theory: I. NLO scattering at leading power
Steven P. Dye🇺🇸 · Matthew Gonderinger🇺🇸 · Gil Paz🇺🇸
The proton radius puzzle, i.e. the large discrepancy in the extraction of the proton charge radius between regular and muonic hydrogen, challenges our understanding of the structure of the proton. It can also be an indication of a new force that couples to muons, but not to electrons. An effective field theory analysis using Non Relativistic Quantum Electrodynamics (NRQED) indicates that the muonic hydrogen result can be interpreted as a large, compared to some model estimates, muon-proton spin-independent contact interaction. The muonic hydrogen result can be tested by a muon-proton scattering experiment, MUSE, that is planned at the Paul Scherrer Institute in Switzerland. The typical momenta of the muons in this experiment are of the order of the muon mass. In this energy regime the muons are relativistic but the protons are still non-relativistic. The interaction between the muons and protons can be described by a hybrid QED-NRQED effective field theory. We present some elements of this effective field theory. In particular we consider $O (Z α)$ scattering up to power $m^{2} / M^{2}$ , where $m$ ( $M$ ) is the muon (proton) mass and $Z = 1$ for a proton, and $O (Z^{2} α^{2})$ scattering at leading power. We show how the former reproduces Rosenbluth scattering up to power $m^{2} / M^{2}$ and the latter the relativistic scattering off a static potential. Proton structure corrections at $O (Z^{2} α^{2})$ will be considered in a subsequent paper.
Comments:
15 pages, 3 figures. v2: text and references added, journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1602.07770 [pdf]
PRD(2016)·16 citations
10
[Submitted on 25 Feb 2016] (cross-list from hep-lat)
$Λ_{c} - N$ interaction from lattice QCD
Takaya Miyamoto · for HAL QCD Collaboration
We investigate the s-wave $Λ_{c} - N$ interaction for spin singlet systems( $^{1} S_{0}$ ) using the HAL QCD method. In our lattice QCD simulations, we employ gauge configurations generated by the PACS-CS Collaboration at $a = 0.0907 (13)$ fm on a $3 2^{3} \times 64$ lattice ( $L a = 2.902 (42)$ fm). We employ two ensembles, one at $m_{π} = 700 (1)$ MeV and the other at $m_{π} = 570 (1)$ MeV to study the quark mass dependence of the $Λ_{c} - N$ interactions. We calculate a $^{1} S_{0}$ central potential not only for the $Λ_{c} - N$ system but also for $Λ - N$ system to understand the role of heavy charm quarks in $Λ_{c} - N$ system. We find repulsion at short distance and attraction at mid-range for both the $Λ_{c} - N$ and the $Λ - N$ potentials. The short range repulsion of the $Λ_{c} - N$ potential is smaller than that of the $Λ - N$ potential, and the attraction of the $Λ_{c} - N$ potential is small compared with the $Λ - N$ potential. The phase shift and scattering length calculated with these potentials show that there exist no bound state for both the $Λ_{c} - N$ and $Λ - N$ systems for $m_{π} > 570$ MeV.
Comments:
7 pages, 3 figures, and 3 tables, Proceedings for the 33rd International Symposium on Lattice Field Theory (Lattice 2015), 14-18 July 2015, Kobe, Japan
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1602.07797 [pdf]
PoS(2016)·15 citations
11
[Submitted on 25 Feb 2016] (cross-list from hep-ph)
Coherent Pion Production in Neutrino Nucleus Scattering
Kapil Saraswat🇮🇳 · Prashant Shukla🇮🇳 · Vineet Kumar🇮🇳 · Venktesh Singh🇮🇳
In this article, we study the coherent pion production in neutrino-nucleus interaction in the resonance region using the formalism based on partially conserved axial current (PCAC) theorem which relates the neutrino-nucleus cross section to the pion-nucleus elastic cross section. The pion nucleus elastic cross section is calculated using the Glauber model in terms of pion-nucleon cross sections obtained by parameterizing the experimental data. We calculate the differential and integrated cross sections for charged current coherent pion production in neutrino carbon scattering. The results of integrated cross section calculations are compared with the measured data. Predictions for the differential and integrated cross sections for coherent pion productions in neutrino iron scattering using above formalism are also made.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1602.07820 [pdf]
PRC(2016)·10 citations
12
[Submitted on 25 Feb 2016] (cross-list from hep-ph)
Decay $B_{s} \to ϕ ℓ^{+} ℓ^{-}$ in covariant quark model
Stanislav Dubnička🇸🇰 · Anna Z. Dubničková🇸🇰 · Aidos Issadykov🇷🇺 · Mikhail A. Ivanov🇷🇺 · Andrej Liptaj🇸🇰 · Sayabek K. Sakhiyev🇰🇿
Our article is devoted to the study of the rare $B_{s} \to ϕ ℓ^{+} ℓ^{-}$ decay where $ℓ = μ, τ$ . We compute the relevant form factors in the framework of the covariant quark model with infrared confinement in the full kinematical momentum transfer region. The calculated form factors are used to evaluate branching fractions and polarization observables in the cascade decay $B \to ϕ (\to K^{+} K^{-}) ℓ^{+} ℓ^{-}$ . We compare the obtained results with available experimental data and the results from other theoretical approaches.
Comments:
16 pages, 13 figures. arXiv admin note: text overlap with arXiv:1511.04887
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1602.07864 [pdf]
PRD(2016)·27 citations
13
[Submitted on 25 Feb 2016] (cross-list from nucl-ex)
Unexpectedly large charge radii of neutron-rich calcium isotopes
R.F. Garcia Ruiz🇧🇪 · M. L. Bissell🇧🇪 · K. Blaum🇩🇪 · A. Ekstrom🇺🇸 · N. Frommgen🇩🇪 · G. Hagen🇺🇸 · M. Hammen🇩🇪 · K. Hebeler🇩🇪 · J.D. Holt🇨🇦 · G.R. Jansen🇺🇸 · M. Kowalska🇨🇭 · K. Kreim🇩🇪 and 10 other authors
Despite being a complex many-body system, the atomic nucleus exhibits simple structures for certain "magic" numbers of protons and neutrons. The calcium chain in particular is both unique and puzzling: evidence of doubly-magic features are known in 40,48Ca, and recently suggested in two radioactive isotopes, 52,54Ca. Although many properties of experimentally known Ca isotopes have been successfully described by nuclear theory, it is still a challenge to predict their charge radii evolution. Here we present the first measurements of the charge radii of 49,51,52Ca, obtained from laser spectroscopy experiments at ISOLDE, CERN. The experimental results are complemented by state-of-the-art theoretical calculations. The large and unexpected increase of the size of the neutron-rich calcium isotopes beyond N = 28 challenges the doubly-magic nature of 52Ca and opens new intriguing questions on the evolution of nuclear sizes away from stability, which are of importance for our understanding of neutron-rich atomic nuclei.
Comments:
Submitted version. See original publication (doi:10.1038/nphys3645) for final version
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1602.07906 [pdf]
Nat.Phys.(2016)·365 citations
14
[Submitted on 25 Feb 2016] (cross-list from quant-ph)
How to quantify coherence: Distinguishing speakable and unspeakable notions
Iman Marvian · Robert W. Spekkens
Quantum coherence is a critical resource for many operational tasks. Understanding how to quantify and manipulate it also promises to have applications for a diverse set of problems in theoretical physics. For certain applications, however, one requires coherence between the eigenspaces of specific physical observables, such as energy, angular momentum, or photon number, and it makes a difference which eigenspaces appear in the superposition. For others, there is a preferred set of subspaces relative to which coherence is deemed a resource, but it is irrelevant which of the subspaces appear in the superposition. We term these two types of coherence unspeakable and speakable respectively. We argue that a useful approach to quantifying and characterizing unspeakable coherence is provided by the resource theory of asymmetry when the symmetry group is a group of translations, and we translate a number of prior results on asymmetry into the language of coherence. We also highlight some of the applications of this approach, for instance, in the context of quantum metrology, quantum speed limits, quantum thermodynamics, and NMR. The question of how best to treat speakable coherence as a resource is also considered. We review a popular approach in terms of operations that preserve the set of incoherent states, propose an alternative approach in terms of operations that are covariant under dephasing, and we outline the challenge of providing a physical justification for either approach. Finally, we note some mathematical connections that hold among the different approaches to quantifying coherence.
Comments:
A non-technical summary of the results and applications is provided in the first section. V5 close to the published version. Typos corrected
Subjects:
Quantum Physics (quant-ph); cond-mat.dis-nn (cond-mat.dis-nn); Strongly Correlated Electrons (cond-mat.str-el); Superconductivity (cond-mat.supr-con); Nuclear Theory (nucl-th)
arXiv:
1602.08049 [pdf]
PRA(2016)·335 citations
15
[Submitted on 25 Feb 2016] (cross-list from hep-ph)
Measuring light-by-light scattering at the LHC and FCC
David d'Enterria🇨🇭 · Gustavo G. da Silveira🇧🇷
Elastic light-by-light scattering, $γ γ \to γ γ$ , can be measured in electromagnetic interactions of lead (Pb) ions at the Large Hadron Collider (LHC) and Future Circular Collider (FCC), using the large (quasi)real photon fluxes available in ultraperipheral collisions. The $γ γ \to γ γ$ cross sections for diphoton masses m $_{γ γ} >$ 5 GeV in pp, pPb, and PbPb collisions at LHC ( $s_{_{NN}}$ = 5.5, 8.8, 14 TeV) and FCC ( $s_{_{NN}}$ = 39, 63, 100 TeV) center-of-mass energies are presented. The measurement has controllable backgrounds in PbPb collisions, and one expects about 70 and 2500 signal events per year at the LHC and FCC respectively, after typical detector acceptance and reconstruction efficiency selections.
Comments:
7 pages, 3 figures. Proceedings EDS'15 Blois conference, July 2015, Corse
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1602.08088 [pdf]
6 citations

Affiliations

first authorsco-authorsvia INSPIRE