119183210
Comment on Phys. Rev. Lett. 109, 152005 (2012)
The identifications of transverse boost and rotation operators in light front theory done in Phys. Rev. Lett. {109}, 152005 (2012) is incorrect. The simple parton interpretation claimed is, in fact, for the transverse boost operator. Manifestation of Lorentz symmetry as claimed in the context of their calculation involving transverse Pauli-Lubanski polarization vector is unsupported.
116463245
The GPDs of The Photon
We report on a recent calculation of the generalized parton distributions (GPDs) of the photon when the momentum transfer in the transverse direction is non-zero. We use an overlap representation of the photon GPDs in terms of the photon light-front wave functions. We calculate the GPDs at leading order in electromagnetic coupling $\alpha$ and zeroth order in strong coupling $\alpha_s$. We consider also the case when the helicity of the photon is flipped. Fourier transform of the GPDs with respect to the transverse momentum transfer gives the parton distributions of the photon in impact parameter space.
119418615
Threshold resummation for W-boson production at BNL RHIC
We study the resummation of large logarithmic perturbative corrections to the partonic cross sections relevant for the process pp{yields}W{sup {+-}}X at the BNL Relativistic Heavy Ion Collider (RHIC). At RHIC, polarized protons are available, and spin asymmetries for this process will be used for precise measurements of the up and down quark and antiquark distributions in the proton. The corrections arise near the threshold for the partonic reaction and are associated with soft-gluon emission. We perform the resummation to next-to-leading logarithmic accuracy, for the rapidity-differential cross section. We find that resummation leads to relatively moderate effects on the cross sections and spin asymmetries.
118529485
Off-axis excitation of hydrogenlike atoms by twisted photons
We show that the twisted photon states, or photon states with large ($> \hbar$) angular momentum projection ($m_\gamma$) in the direction of motion, can photoexcite atomic levels for a hydrogen-like atom that are novel and distinct and are not restricted by $m_\gamma$, when the symmetry axis of the twisted-photon beam does not coincide with the center of the atomic target. Selection rules are given and interesting implications and observables for the above process are pointed out.
118544091
Excitation of an Atom by Twisted Photons
Twisted photon states, or photon states with large ($> \hbar$) angular momentum projection in the direction of motion, can photoexcite atomic final states of differing quantum numbers. If the photon symmetry axis coincides with the center of an atom, there are known selection rules that require exact matching between the quantum numbers of the photon and the photoexcited states. The more general case of arbitrarily positioned beams relaxes the selection rules but produces a distribution of quantum numbers of the final atomic states that is novel and distinct from final states produced by plane-wave photons. Numerical calculations are presented using a hydrogen atom as an example.
55544629
Universality of TMD correlators
In a high-energy scattering process with hadrons in the initial state, color is involved. Transverse momentum dependent distribution functions (TMDs) describe the quark and gluon distributions in these hadrons in momentum space with the inclusion of transverse directions. Apart from the (anti)-quarks and gluons that are involved in the hard scattering process, additional gluon emissions by the hadrons have to be taken into account as well, giving rise to Wilson lines or gauge links. The TMDs involved are sensitive to the process under consideration and hence potentially nonuniversal due to these Wilson line interactions with the hard process; different hard processes give rise to different Wilson line structures. We will show that in practice only a finite number of universal TMDs have to be considered, which come in different linear combinations depending on the hard process under consideration, ensuring a generalized universality. For quarks this gives rise to three Pretzelocity functions, whereas for gluons a richer structure of functions arises.
6841250
Quantum Monte Carlo calculations of neutron matter with nonlocal chiral interactions.
We present fully nonperturbative quantum Monte Carlo calculations with nonlocal chiral effective field theory (EFT) interactions for the ground-state properties of neutron matter. The equation of state, the nucleon chemical potentials, and the momentum distribution in pure neutron matter up to one and a half times the nuclear saturation density are computed with a newly optimized chiral EFT interaction at next-to-next-to-leading order. This work opens the way to systematic order by order benchmarking of chiral EFT interactions and ab initio prediction of nuclear properties while respecting the symmetries of quantum chromodynamics.
100464553
Level densities of nickel isotopes: microscopic theory versus experiment
We apply a spin-projection method to calculate microscopically the level densities of a family of nickel isotopes $^{59-64}$Ni using the shell model Monte Carlo approach in the complete $pfg_{9/2}$ shell. Accurate ground-state energies of the odd-mass nickel isotopes, required for the determination of excitation energies, are determined using the Green's function method recently introduced to circumvent the odd particle-number sign problem. Our results are in excellent agreement with recent measurements based on proton evaporation spectra and with level counting data at low excitation energies. We also compare our results with neutron resonance data, assuming equilibration of parity and a spin-cutoff model for the spin distribution at the neutron binding energy, and find good agreement with the exception of $^{63}$Ni.
119532334
Variational theory of hot nucleon matter
We develop a variational theory of hot nuclear matter in neutron stars and supernovae. It can also be used to study charged, hot nuclear matter which may be produced in heavy-ion collisions. This theory is a generalization of the variational theory of cold nuclear and neutron star matter based on realistic models of nuclear forces and pair correlation operators. The present approach uses microcanonical ensembles and the variational principle obeyed by the free energy. In this paper we show that the correlated states of the microcanonical ensemble at a given temperature T and density {rho} can be orthonormalized preserving their diagonal matrix elements of the Hamiltonian. This allows for the minimization of the free energy without corrections from the nonorthogonality of the correlated basis states, similar to that of the ground state energy. Samples of the microcanonical ensemble can be used to study the response, and the neutrino luminosities and opacities of hot matter. We present methods to orthonormalize the correlated states that contribute to the response of hot matter.
118482889
Quantum Monte Carlo with Coupled-Cluster wave functions
ECT*, Villa Tambosi, I-38123 Villazzano (Trento), Italy(Dated: May 3, 2013)We introduce a novel many body method which combines two powerful many body techniques,viz., quantum Monte Carlo and coupled cluster theory. Coupled cluster wave functions are intro-duced as importance functions in a Monte Carlo method designed for the conﬁguration interactionframework to provide rigorous upper bounds to the ground state energy. We benchmark our methodon the homogeneous electron gas in momentum space. The importance function used is the coupledcluster doubles wave function. We show that the computational resources required in our methodscale polynomially with system size. Our energy upper bounds are in very good agreement withprevious calculations of similar accuracy, and they can be systematically improved by includinghigher order excitations in the coupled cluster wave function.
54611279
Number-conserving theory of nuclear pairing gaps: A global assessment
We study odd-even mass staggering of nuclei, also called pairing gaps, using a Skyrme self-consistent mean-field theory and a numerically exact treatment of the pairing Hamiltonian. We find that the configuration-space Monte Carlo method proposed by Cerf and Martin [Phys. Rev. C 47, 2610 (1993)] offers a practical computational procedure to carry out the numerical solutions in large-dimensional model spaces. Refitting the global strength of the pairing interaction for 443 neutron pairing gaps in our number-conserving treatment, we find the correction to the pairing correlation energies and pairing gaps to have rms values of 0.6 and 0.12 MeV, respectively. The exact treatment provides a significant improvement in the fit to experimental gaps, although it is partially masked by a larger rms error due to deficiencies in other aspects of the theory, such as the mean-field energy functional.