Nuclear Theory·nucl-th

Wednesday·September 19, 2018

10 papers—1 primary·9 cross-listed

01
[Submitted on 17 Sept 2018]
Weak radius of the proton
C. J. Horowitz🇺🇸
The weak charge of the proton determines its coupling to the $Z^{0}$ boson. The distribution of weak charge is found to be dramatically different from the distribution of electric charge. The proton's weak radius $R_{W} = 1.545 \pm 0.017$ fm is 80\% larger than its charge radius $R_{c h} \approx 0.84$ fm because of a very large pion cloud contribution. This large weak radius can be measured with parity violating electron scattering and may provide insight into the structure of the proton, various radiative corrections, and possible strange quark contributions.
Comments:
4 pages, 2 figures, Error estimate improved, Phys. Lett. B in press
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1809.06478 [pdf]
PLB(2019)·7 citations
02
[Submitted on 15 Sept 2016] (cross-list from hep-ph)
Chiral spiral induced by a strong magnetic field
H. Abuki🇯🇵
We study the modification of the chiral phase structure of QCD due to an external magnetic field. We first demonstrate how the effect of magnetic field can systematically be incorporated into a generalized Ginzburg-Landau framework. We then analyze the phase structure in the vicinity of the chiral critical point. In the chiral limit, the effect is found to be so drastic that it totally washes the tricritical point out of the phase diagram, bringing the continent for the chiral spiral. This is the case no matter how small is the intensity of the magnetic field. On the other hand, the current quark mass protects the chiral critical point from a weak magnetic field. However the critical point will eventually be covered by the chiral spiral phase as the magnetic field grows.
Comments:
6 pages, 6 eps figures. Presented at QCD@Work 2016: International Workshop on QCD - Theory and Experiment, June 27-30, Martina-Franca (Italy)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.04605 [pdf]
EPJ Web Conf.(2016)·8 citations
03
[Submitted on 17 Sept 2018] (cross-list from hep-ph)
Proton charge radius extraction from electron scattering data using dispersively improved chiral effective field theory
J. M. Alarcón🇪🇸 · D. W. Higinbotham🇺🇸 · C. Weiss🇺🇸 · Z. Ye🇺🇸
We extract the proton charge radius from the elastic form factor (FF) data using a novel theoretical framework combining chiral effective field theory and dispersion analysis. Complex analyticity in the momentum transfer correlates the behavior of the spacelike FF at finite $Q^{2}$ with the derivative at $Q^{2} = 0$ . The FF calculated in the predictive theory contains the radius as a free parameter. We determine its value by comparing the predictions with a descriptive global fit of the spacelike FF data, taking into account the theoretical and experimental uncertainties. Our method allows us to use the finite- $Q^{2}$ FF data for constraining the radius (up to $Q^{2} \sim$ 0.5 GeV $^{2}$ and larger) and avoids the difficulties arising in methods relying on the $Q^{2} \to 0$ extrapolation. We obtain a radius of 0.844(7) fm, consistent with the high-precision muonic hydrogen results.
Comments:
8 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
1809.06373 [pdf]
PRC(2019)·72 citations
04
[Submitted on 17 Sept 2018] (cross-list from astro-ph.HE)
Impact of QCD jets and heavy-quark production in cosmic-ray proton atmospheric showers up to 10 $^{20}$ eV
David d'Enterria🇨🇭 · Tanguy Pierog🇩🇪 · Guanhao Sun🇨🇭
The PYTHIA 6 Monte Carlo (MC) event generator, commonly used in collider physics, is interfaced for the first time with a fast transport simulation of a hydrogen atmosphere, with the same density as air, in order to study the properties of extended atmospheric showers (EAS) produced by cosmic ray protons with energies E $_{C R} \approx 1 0^{14}$ -- $1 0^{20}$ eV. At variance with the hadronic MC generators (EPOS-LHC, QGSJET, and SIBYLL) commonly used in cosmic-rays physics, PYTHIA includes the generation of harder hadronic jets and heavy (charm and bottom) quarks, thereby producing higher transverse momentum final particles, that could explain several anomalies observed in the data. The electromagnetic, hadronic, and muonic properties of EAS generated with various settings of PYTHIA 6, tuned to proton-proton data measured at the LHC, are compared to those from EPOS-LHC, QGSJET 01, QGSJET II, and SIBYLL 2.1. Despite their different underlying parton dynamics, the characteristics of the EAS generated with PYTHIA 6 are in between those predicted by the rest of MC generators. The only exceptions are the muonic components at large transverse distances from the shower axis, where PYTHIA predicts more activity than the rest of the models. Heavy-quark production, as implemented in this study for a hydrogen atmosphere, does not seem to play a key role in the EAS muon properties, pointing to nuclear effects as responsible of the muon anomalies observed in the air-shower data.
Comments:
13 pages, 20 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1809.06406 [pdf]
ApJ(2019)·15 citations
05
[Submitted on 17 Sept 2018] (cross-list from hep-ph)
Form Factors and Generalized Parton Distributions of Heavy Quarkonia in Basis Light Front Quantization
Lekha Adhikari🇺🇸 · Yang Li🇺🇸 · Meijian Li🇺🇸 · James P. Vary🇺🇸
We calculate the electromagnetic (charge, magnetic and quadrupole) form factors and the associated static moments of heavy quarkonia (charmonia and bottomonia) using the Basis Light Front Quantization (BLFQ) approach. For this work, we adopt light front wavefunctions (LFWFs) generated by a holographic QCD confining potential and a one-gluon exchange interaction with fixed coupling. We compare our BLFQ results with the limiting case of a single BLFQ basis state description of heavy quarkonia and with other available results. These comparisons provide insights into relativistic effects. Using the same LFWFs generated in the BLFQ approach, we also present the generalized parton distributions (GPDs) for selected mesons including those for radially excited mesons such as $ψ^{'}$ and $Υ^{'}$ . Our GPD results establish the foundation within BLFQ for further investigating hadronic structure such as probing the spin structure of spin-one hadrons in the off-forward limit.
Comments:
20 pages, 29 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1809.06475 [pdf]
PRC(2019)·39 citations
06
[Submitted on 18 Sept 2018] (cross-list from hep-ph)
Dual chiral density waves in nuclear matter
Hiroaki Abuki🇯🇵 · Yusuke Takeda🇯🇵 · Masayasu Harada🇯🇵
We study inhomogeneous chiral phases in nuclear matter using a hadronic model with the parity doublet structure. With an extended ansatz for the dual chiral density wave off the chiral limit, we numerically determine the phase structure. A new type of dual chiral density wave where the condensate has nonvanishing space average is confirmed and it comes to occupy a wide range of low density region as the chiral invariant mass parameter is lowered.
Comments:
7 pages, 5 eps figures, contribution to "QCD@Work 2018", International Workshop on QCD Theory and Experiment. 25-28 June 2018, Matera, Italy
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1809.06485 [pdf]
EPJ Web Conf.(2018)·10 citations
07
[Submitted on 18 Sept 2018] (cross-list from hep-ph)
Reflections on the Origin of the EMC Effect
Anthony W. Thomas🇦🇺
In the 35 years since the European Muon Collaboration announced the astonishing result that the valence structure of a nucleus was very different from that of a free nucleon, many explanations have been suggested. The first of the two most promising explanations is based upon the different effects of the strong Lorentz scalar and vector mean fields known to exist in a nucleus on the internal structure of the nucleon-like clusters which occupy shell model states. The second links the effect to the modification of the structure of nucleons involved in short-range correlations, which are far off their mass shell. We explore some of the methods which have been proposed to give complementary information on this puzzle, especially the spin-dependent EMC effect and the isovector EMC effect, both proposed by Cloet, Bentz and Thomas. It is shown that the predictions for the spin dependent EMC effect, in particular, differ substantially within the mean-field and short-range correlation approaches. Hence the measurement of the spin dependent EMC effect at Jefferson Lab should give us a deeper understanding of the origin of the EMC effect and, indeed, of the structure of atomic nuclei.
Comments:
Contribution to the Volume celebrating the contributions of Prof. Ernest Henley
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1809.06622 [pdf]
IJMPE(2019)·21 citations
08
[Submitted on 18 Sept 2018] (cross-list from physics.atom-ph)
Evaluation of CP-violation in HfF $^{+}$
A.N. Petrov (1,2)🇷🇺 · L.V. Skripnikov (1,2)🇷🇺 · A.V. Titov (1,2)🇷🇺 · V. V. Flambaum (3) ((1) B.P.Konstantinov Petersburg Nuclear Physics Institute, Gatchina, Leningrad district, Russia (2) Dept. of Physics, Saint Petersburg State University, Saint Petersburg, Russia (3) School of Physics, The University of New South Wales, Sydney, Australia)🇦🇺
CP violation effects produced by the nuclear magnetic quadrupole moment (MQM), electron electric dipole moment (EDM) and scalar $-$ pseudoscalar nucleus $-$ electron neutral current (SP) interaction in $^{177}$ Hf $^{19}$ F $^{+}$ and $^{179}$ Hf $^{19}$ F $^{+}$ are calculated. The role of the hyperfine interaction is investigated. It is shown that the MQM shift can be distinguished from the electron EDM and SP ones due to the implicit dependence of MQM shift on the hyperfine sublevel. The MQM effect is expressed in terms of the proton (EDM), QCD vacuum angle $θ$ and quark chromo-EDMs.
Subjects:
Atomic Physics (physics.atom-ph); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1809.06701 [pdf]
PRA(2018)·22 citations
09
[Submitted on 18 Sept 2018] (cross-list from hep-ph)
A Deeply Bound Dibaryon is Incompatible with Neutron Stars and Supernovae
Samuel D. McDermott🇺🇸 · Sanjay Reddy🇺🇸 · Srimoyee Sen🇺🇸
We study the effect of a dibaryon, S, in the mass range 1860 MeV < m_S < 2054 MeV, which is heavy enough not to disturb the stability of nuclei and light enough to possibly be cosmologically metastable. Such a deeply bound state can act as a baryon sink in regions of high baryon density and temperature. We find that the ambient conditions encountered inside a newly born neutron star are likely to sustain a sufficient population of hyperons to ensure that a population of S dibaryons can equilibrate in less than a few seconds. This would be catastrophic for the stability of neutron stars and the observation of neutrino emission from the proto-neutron star of Supernova 1987A over ~ O(10)s. A deeply bound dibaryon is therefore incompatible with the observed supernova explosion, unless the cross section for S production is severely suppressed.
Comments:
4ish+2 pages, 1 main figure; matches journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1809.06765 [pdf]
PRD(2019)·18 citations
10
[Submitted on 18 Sept 2018] (cross-list from hep-ph)
Final-state interactions of the Higgs boson in quark-gluon matter
David d'Enterria🇨🇭 · Constantin Loizides🇺🇸
In the first version of this paper \cite{dEnterria:2018bqi}, we presented a study of the final-state interactions of the Higgs boson in the hot and dense quark-gluon systems produced in pp, pPb, and PbPb collisions at CERN LHC and FCC energies. By computing the leading-order diagrams of the Higgs-parton scattering cross sections in perturbative QCD, and by embedding the produced Higgs bosons in an expanding quark-gluon medium modeled with 2D+1 viscous hydrodynamics with various QCD equations of state, we presented estimates of the expected scalar boson yields as functions of transverse momentum $p_{T}^{H}$ , and produced medium space-time size. A moderate suppression of the scalar boson yields was predicted due to medium-enhanced $H \to g g, q q ˉ$ decays, in detriment of the $H \to γ γ, 4 ℓ$ channels that are typically used to observe the Higgs particle. After our work appeared, J. Ghiglieri and U. Wiedemann \cite{Ghiglieri:2019lzz} have presented thermal-field-theory calculations that indicate that the $H \to g g, q q ˉ$ partial decays widths remain basically unaffected by interactions with surrounding partons in the kinematic range of relevance of our study. Such a theoretical result, in contradiction with our estimates, has brought us to revisit our calculations and to realize of the quantitative importance of thermal virtual corrections, neglected in our first work, that are as large as the real ones and of opposite sign. Such virtual corrections significantly reduce the Higgs-parton "absorption" cross sections originally computed in Ref. \cite{dEnterria:2018bqi}, and make the Higgs boson suppression negligible in the kinematic regime considered.
Comments:
Paper withdrawn for the reasons explained above
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1809.06832 [pdf]
13 citations

Affiliations

first authorsco-authorsvia INSPIRE