Nuclear Theory·nucl-th

Friday·February 24, 2017

12 papers—2 primary·10 cross-listed

01
Electromagnetic characteristics of $A \leq 3$ physical and lattice nuclei
Johannes Kirscher🇺🇸 · Ehoud Pazy🇮🇱 · Jonathan Drachman🇮🇱 · Nir Barnea🇮🇱
We analyze the quark-mass dependence of electromagnetic properties of two and three-nucleon states. To that end, we apply the pionless effective field theory to experimental data and numerical lattice calculations which simulate QCD at pion masses of 450~MeV and 806~MeV. At the physical pion mass, we postdict the magnetic moment of helium-3, $μ_{^{3} H e} = - 2.13$ nNM, and the magnetic polarizability of deuterium, $β_{D} = 7.33 1 0^{- 2}$ fm $^{3}$ . Magnetic polarizabilities of helium-3, $β_{^{3} H e} = 9.7 1 0^{- 4}$ fm $^{3}$ , and the triton, $β_{^{3} H} = 8.2 1 0^{- 4}$ fm $^{3}$ , are predictions. Postdictions of the effective theory for the magnetic moments are found consistent with QCD simulations at 806~MeV pion mass while our EFT result $β_{D} = 2.92 1 0^{- 2}$ fm $^{3}$ was not extracted from the lattice. The deuteron would thus be relatively pliable compared to a three-nucleon state for which we postdict $β_{^{3} H} = 3.9 1 0^{- 5}$ fm $^{3}$ . At $m_{π} = 450$ MeV, the magnetic moment of the triton is predicted, $μ_{^{3} H e} = - 2.15 (5)$ nNM, based on a conjecture of its binding energy, $B_{^{3} H} ≅ 30$ ~MeV. For all three pion masses, we compare the point-charge radii of the two and three-nucleon bound states. The sensitivity of the electromagnetic properties to the Coulomb interaction between protons is studied in anticipation of lattice calculations with dynamical QED.
nucl-thhep-latPRC(2017)·28 citations
02
Taming instability of magnetic field in chiral medium
Kirill Tuchin🇺🇸
Magnetic field is unstable in a medium with time-independent chiral conductivity. Owing to the chiral anomaly, the electromagnetic field and the medium exchange helicity which results in time-evolution of the chiral conductivity. Using the fastest growing momentum and helicity state of the vector potential as an ansatz, the time-evolution of the chiral conductivity and magnetic field is solved analytically. The solution for the hot and cold equations of state shows that the magnetic field does not develop an instability due to he helicity conservation. Moreover, it develops a peak only if a significant part of the \emph{initial} helicity is stored in the medium. The initial helicity determines the height and position of the peak.
nucl-thhep-phhep-thNPA(2018)·17 citations
03
$Λ_{c} \to Λ ℓ^{+} ν_{ℓ}$ form factors and decay rates from lattice QCD with physical quark masses
Stefan Meinel🇺🇸
The first lattice QCD calculation of the form factors governing $Λ_{c} \to Λ ℓ^{+} ν_{ℓ}$ decays is reported. The calculation was performed with two different lattice spacings and includes one ensemble with a pion mass of 139(2) MeV. The resulting predictions for the $Λ_{c} \to Λ e^{+} ν_{e}$ and $Λ_{c} \to Λ μ^{+} ν_{μ}$ decay rates divided by $∣ V_{cs} ∣^{2}$ are $0.2007 (71) (74) ps^{- 1}$ and $0.1945 (69) (72) ps^{- 1}$ , respectively, where the two uncertainties are statistical and systematic. Taking the Cabibbo-Kobayashi-Maskawa matrix element $∣ V_{cs} ∣$ from a global fit and the $Λ_{c}$ lifetime from experiments, this translates to branching fractions of $B (Λ_{c} \to Λ e^{+} ν_{e}) = 0.0380 (19)_{LQCD} (11)_{τ_{Λ_{c}}}$ and $B (Λ_{c} \to Λ μ^{+} ν_{μ}) = 0.0369 (19)_{LQCD} (11)_{τ_{Λ_{c}}}$ . These results are consistent with, and two times more precise than, the measurements performed recently by the BESIII Collaboration. Using instead the measured branching fractions together with the lattice calculation to determine the CKM matrix element gives $∣ V_{cs} ∣ = 0.949 (24)_{LQCD} (14)_{τ_{Λ_{c}}} (49)_{B}$ .
↳ hep-lathep-exhep-phnucl-thPRL(2017)·93 citations
04
The effect upon neutrinos of core-collapse supernova accretion phase turbulence
James P. Kneller🇺🇸 · Mithi de los Reyes🇬🇧
During the accretion phase of a core-collapse supernovae, large amplitude turbulence is generated by the combination of the standing accretion shock instability and convection driven by neutrino heating. The turbulence directly affects the dynamics of the explosion, but there is also the possibility of an additional, indirect, feedback mechanism due to the effect turbulence can have upon neutrino flavor evolution and thus the neutrino heating. In this paper we consider the effect of turbulence during the accretion phase upon neutrino evolution, both numerically and analytically. Adopting representative supernova profiles taken from the accretion phase of a supernova simulation, we find the numerical calculations exhibit no effect from turbulence. We explain this absence using two analytic descriptions: the Stimulated Transition model and the Distorted Phase Effect model. In the Stimulated Transition model turbulence effects depend upon six different lengthscales, and three criteria must be satisfied between them if one is to observe a change in the flavor evolution due to Stimulated Transition. We further demonstrate that the Distorted Phase Effect depends upon the presence of multiple semi-adiabatic MSW resonances or discontinuities that also can be expressed as a relationship between three of the same lengthscales. When we examine the supernova profiles used in the numerical calculations we find the three Stimulated Transition criteria cannot be satisfied, independent of the form of the turbulence power spectrum, and that the same supernova profiles lack the multiple semi-adiabatic MSW resonances or discontinuities necessary to produce a Distorted Phase Effect. Thus we conclude that even though large amplitude turbulence is present in supernova during the accretion phase, it has no effect upon neutrino flavor evolution.
↳ astro-ph.HEastro-ph.SRhep-phnucl-thJ.Phys.G(2017)·9 citations
05
Enforcing causality in nonrelativistic equations of state at finite temperature
Constantinos Constantinou · Madappa Prakash
We present a thermodynamically consistent method by which equations of state based on nonrelativistic potential models can be modified so that they respect causality at high densities, both at zero and finite temperature (entropy). We illustrate the application of the method using the high density phase parametrization of the well known APR model in its pure neutron matter configuration as an example. We also show that, for models with only contact interactions, the adiabatic speed of sound is independent of the temperature in the limit of very large temperature. This feature is approximately valid for models with finite-range interactions as well, insofar as the temperature dependence they introduce to the Landau effective mass is weak. In addition, our study reveals that in first principle nonrelativistic models of hot and dense matter, contributions from higher than two-body interactions must be screened at high density to preserve causality.
↳ astro-ph.HEnucl-thPRC(2017)·9 citations
06
Fermions in worldline holography
Dennis D. Dietrich🇩🇪 · Adrian Koenigstein🇩🇪
We analyse the worldline holographic framework for fermions. Worldline holography is based on the observation that in the worldline approach to quantum field theory, sources of a quantum field theory over Mink $_{4}$ naturally form a field theory over AdS $_{5}$ to all orders in the elementary fields and in the sources. Schwinger's proper time of the worldline formalism automatically appears with the physical four spacetime dimensions in an AdS $_{5}$ geometry. The worldline holographic effective action in general and the proper-time profiles of the sources in particular solve a renormalisation group equation. By taking into account sources up to spin one, we reconstruct seminal holographic models. Considering spin two confirms AdS $_{5}$ as consistent background.
↳ hep-thhep-phnucl-thPRD(2017)·1 citation
07
More efficient formulas for efficiency correction of cumulants and effect of using averaged efficiency
Toshihiro Nonaka🇯🇵 · Masakiyo Kitazawa🇯🇵 · ShinIchi Esumi🇯🇵
We derive formulas for the efficiency correction of cumulants with many efficiency bins. The derivation of the formulas is simpler than the previously suggested method, but the numerical cost is drastically reduced from the naive method. From analytical and numerical analyses in simple toy models, we show that the use of the averaged efficiency in the efficiency correction can lead to wrong corrected values, which have larger deviation for higher order cumulants. These analyses show the importance of carrying out the efficiency correction without taking the average.
↳ physics.data-anhep-phnucl-exnucl-thPRC(2017)·82 citations
08
An overview of experimental results from ultra-relativistic heavy-ion collisions at the CERN LHC: hard probes
Panagiota Foka🇩🇪 · Malgorzata Anna Janik🇵🇱
The first collisions of lead nuclei, delivered by the CERN Large Hadron Collider (LHC) at the end of 2010, at a centre-of-mass energy per nucleon pair $s_{N N}$ = 2.76 TeV, marked the beginning of a new era in ultra-relativistic heavy-ion physics. The study of the properties of the produced hot and dense strongly-interacting matter at these unprecedented energies is currently experimentally pursued by all four big LHC experiments, ALICE, ATLAS, CMS, and LHCb. The more than a factor 10 increase of collision energy at LHC, relative to the previously achieved maximal energy at other collider facilities, results in an increase of production rates of hard probes. This review presents selected experimental results focusing on observables probing hard processes in heavy-ion collisions delivered during the first three years of the LHC operation. It also presents the first results from Run 2 heavy-ion data at the highest energy, as well as from the studies of the reference pp and pPb systems, which are an integral part of the heavy-ion programme.
↳ hep-exhep-phnucl-exnucl-thRev.Phys.(2016)·59 citations
09
An overview of experimental results from ultra-relativistic heavy-ion collisions at the CERN LHC: bulk properties and dynamical evolution
Panagiota Foka🇩🇪 · Malgorzata Anna Janik🇵🇱
The first collisions of lead nuclei, delivered by the CERN Large Hadron Collider (LHC) at the end of 2010, at a centre-of-mass energy per nucleon pair $s_{N N}$ = 2.76 TeV, marked the beginning of a new era in ultra-relativistic heavy-ion physics. Following the Run 1 period, LHC also successfully delivered PbPb collisions at the collision energy $s_{N N}$ = 5.02 TeV at the end of 2015. The study of the properties of the produced hot and dense strongly-interacting matter at these unprecedented energies is experimentally pursued by all four big LHC experiments, ALICE, ATLAS, CMS, and LHCb. This review presents selected experimental results from heavy-ion collisions delivered during the first three years of the LHC operation focusing on the bulk matter properties and the dynamical evolution of the created system. It also presents the first results from Run 2 heavy-ion data at the highest energy, as well as from the studies of the reference pp and pPb systems, which are an integral part of the heavy-ion programme.
↳ hep-exhep-phnucl-exnucl-thRev.Phys.(2016)·88 citations
10
The semi-relativistic scattering states of the two-body spinless Salpeter equation with the Varshni potential model
O.J. Oluwadare · K.J. Oyewumi
In this present work, the scattering state solutions of the Spinless Salpeter equation with the Varshni potential model were investigated. The approximate scattering phase shift, normalization constant, bound state energy, wave number and wave function in the asymptotic region were obtained. The behaviour of the phase shift with the two-body mass index {\eta} were discussed and presented.
↳ quant-phnucl-thEur.Phys.J.Plus(2017)·5 citations
11
Vector boson-tagged jet production in heavy ion collisions at the LHC
Zhong-Bo Kang🇺🇸 · Ivan Vitev🇺🇸 · Hongxi Xing🇺🇸
Vector boson-tagged jet production in collisions of heavy nuclei opens new opportunities to study parton shower formation and propagation in strongly interacting matter. It has been argued to provide a golden channel that can constrain the energy loss of jets in the quark-gluon plasma created in heavy ion reactions. We present theoretical results for isolated photon-tagged and $Z^{0}$ boson-tagged jet production in Pb+Pb collisions with $s_{N N} = 5.02$ TeV at the LHC. Specifically, we evaluate the transverse momentum imbalance $x_{JV}$ distribution and nuclear modification factor $I_{AA}$ of tagged jets and compare our theoretical calculations to recent experimental measurements by ATLAS and CMS collaborations. Our analysis, which includes both collisional and radiative energy losses, sheds light on their relative importance versus the strength of jet-medium interactions and helps quantify the amount of out-of-cone radiation of predominantly prompt quark-initiated jets.
↳ hep-phnucl-thPRC(2017)·45 citations
12
Chiral Vortical Effect for Bosons
Artur Avkhadiev🇺🇸 · Andrey V. Sadofyev🇺🇸
The thermal contribution to the chiral vortical effect is believed to be related to the axial anomaly in external gravitational fields. We use the universality of the spin-gravity interaction to extend this idea to a wider set of phenomena. We consider the Kubo formula at weak coupling for the spin current of a vector field and derive a novel anomalous effect caused by the medium rotation: the chiral vortical effect for bosons. The effect consists in a spin current of vector bosons along the angular velocity of the medium. We argue that it has the same anomalous nature as in the fermionic case and show that this effect provides a mechanism for helicity transfer, from flow helicity to magnetic helicity.
↳ hep-thnucl-thPRD(2017)·54 citations

Affiliations

first authorsco-authorsvia INSPIRE