9899757
Probing parton orbital angular momentum in longitudinally polarized nucleon
While the total orbital angular momentum (OAM) of a definite quark flavor in a longitudinally-polarized nucleon can be obtained through a sum rule involving twist-two generalized parton distribution (GPDs), its distribution as a function of parton momentum in light-front coordinates is more complicated to define and measure because it involves intrinsically twist-three effects. In this paper, we consider two different parton OAM distributions. The first is manifestly gauge invariant, and its moments are local operators and calculable in lattice QCD. We show that it can potentially be measured through twist-three GPDs. The second is the much-debated canonical OAM distribution natural in free-field theory and light-cone gauge. We show the latter in light-cone gauge can also be related to twist-three GPDs as well as quantum phase-space Wigner distributions, both being measurable in high-energy experiments.
117586880
Prompt $J/\psi$ production at $e^{+} e^{-}$ colliders
In this paper, we discuss the prompt j/psi production at e^+e^- colliders via color-singlet and color-octet production mechanisms. The color-singlet production processes include 1) e^+e^- to J/\psi gg; 2) e^+e^- to J/\psi c\bar{c}; 3) e^+e^- to q \bar q ggJ/\psi and e^+e^- to q \bar q g\chi_c followed by \chi_c to J/\psi \gamma. The color-octet production processes include 1) e^+e^- to J/\psi g; 2) e^+e^- to j/psi q\bar q. Of all these production channels, we find that the color-octet contributions dominate over the color-singlet contributions at any energy scales. At low energies (\sqrt{s}< 20 GeV), the dominant channel is e^+e^- to J/\psi g whereas at high energies e+e^- to j/psi q\bar q will take the leading part. We also find that the energy spectrum for the color-octet j/psi production in process e^+e^- to j/psi q\bar q is very soft, and the mean energy of the produced j/psi is only about 10 GeV~ 20 GeV even at very high energies (e.g. at 1000 GeV). The extraction of color-octet matrix elements from j/psi production in e^+e^- collisions is also discussed.
13309625
Diffractive charm jet production at hadron colliders in the two gluon exchange model
Following our recent paper on the calculations of diffractive quark jet production at hadron colliders, we present here the calculations of gluon jet production at hadron colliders in the two-gluon exchange parameterization of the Pomeron model. We use the helicity amplitude method to calculate the cross section formula. We find that for the gluon jet production the diffractive process is related to the differential off-diagonal gluon distribution function in the proton. We estimate the production rate for this process at the Fermilab Tevatron by approximating the off-diagonal gluon distribution function by the usual diagonal gluon distribution.
16473915
D-wave charmonium production in B decays
The calculation of D-wave charmonium production rates in B meson decays under the NRQCD factorization formalism is presented. We find that the inclusion of the color-octet contributions permits us to detect the D-wave charmonium states in B decays at present experimental facilities. The same amount of signals of the 2{sup {minus}{minus}} D-wave state as that of {psi}{sup {prime}} could be observed at CERN LEP and CESR. We also predict that the relative production rates for four D-wave states are {delta}{sup c}:{delta}{sub 1}{sup c}:{delta}{sub 2}{sup c}:{delta}{sub 3}{sup c}=2.5:3:5:7, where {delta}{sup c}, {delta}{sub 1}{sup c}, {delta}{sub 2}{sup c}, {delta}{sub 3}{sup c} represent, respectively, the 2{sup {minus}+}, 1{sup {minus}{minus}}, 2{sup {minus}{minus}}, 3{sup {minus}{minus}} states. {copyright} {ital 1997} {ital The American Physical Society}
118378485
Phases of Augmented Hadronic Light-Front Wave Functions
It is an important question whether the final/initial state gluonic interactions which lead to naive-time-reversal-odd single-spin asymmetries and diffraction at leading twist can be associated in a definite way with the light-front wave function hadronic eigensolutions of QCD. We use light-front time-ordered perturbation theory to obtain augmented light-front wave functions which contain an imaginary phase which depends on the choice of advanced or retarded boundary condition for the gauge potential in light-cone gauge. We apply this formalism to the wave functions of the valence Fock states of nucleons and pions, and show how this illuminates the factorization properties of naive-time-reversal-odd transverse momentum dependent observables which arise from rescattering. In particular, one calculates the identical leading-twist Sivers function from the overlap of augmented light-front wavefunctions that one obtains from explicit calculations of the single-spin asymmetry in semi-inclusive deep inelastic lepton-polarized nucleon scattering where the required phases come from the final-state rescattering of the struck quark with the nucleon spectators.
211730981
Transverse Momentum Dependent Parton Distri- butions at an Electron-Ion Collider
Transverse momentum dependent (TMD) parton distributions have attracted great attentions from both experiment and theory sides in recent years [1]. They open a new window to investigate the strong interaction physics and the fundamental properties of QCD theory. At the leading order, there are eight independent TMD quark distributions: three k⊥-even distributions (unpolarized, longitudinal polarized quark distributions, and the quark transversity), and five k⊥-odd distributions. Because of the correlations between the quark transverse momentum and the nucleon spin, the TMDs naturally provide important information on the dynamics of partons in the transverse plane in momentum space. Measurements of the k⊥-odd quark distributions provide information about the correlation between the quark orbital angular momentum and the nucleon/quark spin because they require wave function components with nonzero orbital angular momentum. One particular example is the quark Sivers function f 1T which describes the transverse momentum distribution correlated with the transverse polarization vector of the nucleon. There have been strong evidence of the Sivers effect in the DIS experiments observed by the HERMES, COMPASS, and JLab Hall A collaborations [2, 3, 4] (see Fig. 1). An important aspect of the Sivers functions which has been revealed theoretically in last few years is the process dependence and the color gauge invariance [5, 6]. Together with the Boer-Mulders function, they are denoted as naive time-reversal odd (T-odd) functions. In the semi-inclusive DIS (SIDIS), where a leading hadron is detected in coincidence with the scattered lepton, the quark Sivers function arises due to the exchange of (infinitely many) gluons between the active struck quark and the remnants of the target, which is referred as the final state interaction effects in DIS. On the other hand, for the Drell-Yan lepton pair production process, it is the initial state interaction effects. As a consequence, the quark Sivers functions differ by a sign in these two processes. This nonuniversality is a fundamental prediction from the gauge invariance of QCD [6]. The experimental check of this sign change is currently one of the outstanding topics in hadronic physics, and Sivers functions from Drell-Yan process can be measured at RHIC. In high energy hadronic processes where we hope to study the transverse momentum dependent parton distributions, besides the transverse momentum, an additional hard momentum scale is essential to make the proper use of the TMD parton distributions and fragmentation functions. This hard momentum scale needs to be much larger than the transverse momentum scale. At the electron-ion collider, DIS processes naturally provide a hard momentum scale: Q, the virtuality for the virtual photon. More importantly, the EIC design has a wide range
118671189
Generalized Hodge dual for torsion in teleparallel gravity
For teleparallel gravity in four dimensions, Lucas and Pereira have shown that its action can be constructed via a generalized Hodge dual for torsion tensor. In this paper, we demonstrate that a direct generalization of this approach to other dimensions fails due to the fact that no generalized Hodge dual operator could be given in general dimensions. Furthermore, if one enforces the definition of a generalized Hodge dual to be consistent with the action of teleparallel gravity in general dimensions, the basic identity for any sensible Hodge dual would require an ad hoc definition for the second Hodge dual operation which is totally unexpected. Therefore, we conclude that at least for the torsion tensor, the observation of Lucas and Pereira only applies to four dimensions.
119257303
F(T) GRAVITY FROM HOLOGRAPHIC RICCI DARK ENERGY MODEL WITH NEW BOUNDARY CONDITIONS
Commonly used boundary conditions in reconstructing f(T) gravity from holographic Ricci dark energy (RDE) model are found to cause some problem, we therefore propose new boundary conditions in this paper. By reconstructing f(T) gravity from the RDE with these new boundary conditions, we show that the new ones are better than the present commonly used ones since they can give the physically expected information, which is lost when the commonly used ones are taken in the reconstruction, of the resulting f(T) theory. Thus, the new boundary conditions proposed here are more suitable for the reconstruction of f(T) gravity.
119293239
Harrison Metrics for the Schwarzschild Black Hole
Based on the hidden conformal symmetry, some authors have proposed a Harrison metric for the Schwarzschild black hole. We give a procedure which can generate a family of Harrison metrics starting from a general set of SL(2, R) vector fields. By analogy with the subtracted geometry of the Kerr black hole, we find a new Harrison metric for the Schwarzschild case. Its conformal generators are also investigated using the Killing equations in the near-horizon limit.
118654021
Thermodynamics of nonspherical black holes from Liouville theory
A Liouville formalism was proposed many years ago to account for the black hole entropy. It was recently updated to connect thermodynamics of general black holes, in particular the Hawking temperature, to two-dimensional Liouville theory. This relies on the dimensional reduction to two-dimensional black hole metric. The relevant dilaton gravity model can be rewritten as a Liouville-like theory. We refine the method and give general formulas for the corresponding scalar and energy–momentum tensors in Liouville theory. This enables us to read off the black hole temperature using a relation which was found about three decades ago. Then the range of application is extended to include nonspherical black holes such as neutral and charged black rings, topological black hole and the case coupled to a scalar field. As for the entropy, following previous authors, we invoke the Lagrangian approach to central charge by Cadoni and then use the Cardy formula. The general relevant parameters are also given. This approach is more advantageous than the usual Hamiltonian approach which was used by the old Liouville formalism for black hole entropy.