Chiral-Odd and Spin-Dependent Quark Fragmentation Functions and their Applications

We define a number of quark fragmentation functions for spin-0, -1/2 and -1 hadrons, and classify them according to their twist, spin and chirality. As an example of their applications, we use them to analyze semi-inclusive deep-inelastic scattering on a transversely polarized nucleon.Comment: 19 pages in Plain TeX, MIT CTP #221

Leading Chiral Contributions to the Spin Structure of the Proton

The leading chiral contributions to the quark and gluon components of the proton spin are calculated using heavy-baryon chiral perturbation theory. Similar calculations are done for the moments of the generalized parton distributions relevant to the quark and gluon angular momentum densities. These results provide useful insight about the role of pions in the spin structure of the nucleon, and can serve as a guidance for extrapolating lattice QCD calculations at large quark masses to the chiral limit.Comment: 8 pages, 2 figures; a typo in Ref. 7 correcte

Transport discovery of emerging robust helical surface states in Z2=0Z_2=0 systems

We study the possibility of realizing robust helical surface states in $Z_2=0$ systems. We find that the combination of anisotropy and finite-size confinement leads to the emergence of robust helical edge states in both 2D and 3D $Z_2=0$ systems. By investigating an anisotropic Bernevig-Hughes-Zhang model in a finite sample, we demonstrate that the transport manifestation of the surface states is robust against non-magnetic disorder, resembling that of a $Z_2 = 1$ phase. Notably, the effective energy gap for the robust helical states can be efficiently engineered, allowing for potential applications as valley filters and valley valves. The realization of emerging robust helical surface states in realistic material is also discussed.Comment: 5 pages, 4 figures; submitted to Phys. Rev. Lett. on Nov. 25. 201

Glueball Spin

The spin of a glueball is usually taken as coming from the spin (and possibly the orbital angular momentum) of its constituent gluons. In light of the difficulties in accounting for the spin of the proton from its constituent quarks, the spin of glueballs is reexamined. The starting point is the fundamental QCD field angular momentum operator written in terms of the chromoelectric and chromomagnetic fields. First, we look at the restrictions placed on the structure of glueballs from the requirement that the QCD field angular momentum operator should satisfy the standard commutation relationships. This can be compared to the electromagnetic charge/monopole system, where the quantization of the field angular momentum places restrictions (i.e. the Dirac condition) on the system. Second, we look at the expectation value of this operator under some simplifying assumptions.Comment: 11 pages, 0 figures; added references and some discussio

Reactor Fuel Fraction Information on the Antineutrino Anomaly

We analyzed the evolution data of the Daya Bay reactor neutrino experiment in terms of short-baseline active-sterile neutrino oscillations taking into account the theoretical uncertainties of the reactor antineutrino fluxes. We found that oscillations are disfavored at $2.6\sigma$ with respect to a suppression of the $^{235}\text{U}$ reactor antineutrino flux and at $2.5\sigma$ with respect to variations of the $^{235}\text{U}$ and $^{239}\text{Pu}$ fluxes. On the other hand, the analysis of the rates of the short-baseline reactor neutrino experiments favor active-sterile neutrino oscillations and disfavor the suppression of the $^{235}\text{U}$ flux at $3.1\sigma$ and variations of the $^{235}\text{U}$ and $^{239}\text{Pu}$ fluxes at $2.8\sigma$. We also found that both the Daya Bay evolution data and the global rate data are well-fitted with composite hypotheses including variations of the $^{235}\text{U}$ or $^{239}\text{Pu}$ fluxes in addition to active-sterile neutrino oscillations. A combined analysis of the Daya Bay evolution data and the global rate data shows a slight preference for oscillations with respect to variations of the $^{235}\text{U}$ and $^{239}\text{Pu}$ fluxes. However, the best fits of the combined data are given by the composite models, with a preference for the model with an enhancement of the $^{239}\text{Pu}$ flux and relatively large oscillations.Comment: 9 page

Molecular dynamics simulation for microscope insight of liquid evaporation on a heated surface

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Molecular dynamics (MD) simulation is a very effective tool that gives a microscopic insight into the mechanisms of complex physical phenomena. This paper uses MD simulation to study the evaporation of a liquid from a heated surface. As for the argon/platinum model, a group of simulations starts from a fixed lower wall with the temperature of 110K. In this system, argon molecule numbers of 784, 1200, 1440 are simulated respectively. Additional simulations for argon models are based on superheat conditions, which indicate that the variation of ultra-thin liquid film thickness is very small with the different numbers of argon molecules. Also, it shows that if the argon molecule numbers increase, the extra molecules accumulate near the cooling wall. In terms of the MD simulation for the water/magnesium model, water evaporates from a magnesium heating wall at different temperatures and an initial study has been carried out. Moreover, further and more accurate simulations will be improved in the near future

Exploring the proton spin structure

Understanding the spin structure of the proton is one of the main challenges in hadronic physics. While the concepts of spin and orbital angular momentum are pretty clear in the context of non-relativistic quantum mechanics, the generalization of these concepts to quantum field theory encounters serious difficulties. It is however possible to define meaningful decompositions of the proton spin that are (in principle) measurable. We propose a summary of the present situation including recent developments and prospects of future developments.Comment: 8 pages, 1 figure, 2 tables, contribution to the proceedings of the DAE-BRNS High Energy Physics Symposium 2014, Dec 8-12, Guwahati, Indi

Disentangling positivity constraints for generalized parton distributions

Positivity constraints are derived for the generalized parton distributions (GPDs) of spin-1/2 hadrons. The analysis covers the full set of eight twist-2 GPDs. Several new inequalities are obtained which constrain GPDs by various combinations of usual (forward) unpolarized and polarized parton distributions including the transversity distribution.Comment: 9 pages (REVTEX), typos correcte

Solution of the off-forward leading logarithmic evolution equation based on the Gegenbauer moments inversion

Using the conformal invariance the leading-log evolution of the off-forward structure function is reduced to the forward evolution described by the conventional DGLAP equation. The method relies on the fact that the anomalous dimensions of the Gegenbauer moments of the off-forward distribution are independent on the asymmetry, or skewedness, parameter and equal to the DGLAP ones. The integral kernels relating the forward and off-forward functions with the same Mellin and Gegenbauer moments are presented for arbitrary asymmetry value.Comment: 11 pages, LaTeX, no figures, revised version, references adde