Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA novel factorization for $F_L$ in the large $x$ limit
169
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
A novel factorization formula is presented for the longitudinal structure function $F_L$ near the elastic region $x to 1$ of deeply inelastic scattering. In moment space this formula can resum all contributions to $F_L$ that are of order $ln^k N/N$. This is achieved by defining a new jet function which probes the transverse momentum of the struck parton in the target at leading twist. The anomalous dimension $gamma_{J^prime}$ of this new jet operator generates in moment space the logarithmic enhancements coming from the fragmentation of the current jet in the final state. It is also shown how the suggested factorization for $F_L$ is related to the corresponding one for $F_2$ in the same kinematic region.
rate research
Read More
We present the perturbative parts of the structure functions F_2^c and F_L^c for a gluon target having nonzero transverse momentum squared at order alpha _s. The results of the double convolution (with respect to the Bjorken variable x and the transverse momentum) of the perturbative part and the unintegrated gluon densities are compared with HERA experimental data for F_2^c and F_L at low x values and with predictions of other approaches. The contribution from F_L^c structure function ranges 10div30% of that of F_2^c at the HERA kinematical range.
A leading-twist factorization formula is derived for the longitudinal structure function in the x -->1 limit of deeply inelastic scattering. This is achieved by defining a new jet function which is gauge independent and probes the transverse momentum of the struck parton in the target. In moment space, terms of order (ln^k N)/N, which are the leading ones for F_L, are shown to be resummable through the cusp anomalous dimension gamma_K and the anomalous dimension gamma_{J^prime} of the new jet function. This anomalous dimension is computed to O(alpha_s). The suggested factorization for F_L reproduces the fixed order results known to O(alpha_s^2). The general ideas for resumming the terms of order (ln^k N)/N in moment space may be extended to the other structure functions and to other inclusive processes near the elastic limit.
We use results for the structure functions $F_L$ for a gluon target having nonzero transverse momentum square at order $alpha_s$, obtained in our previous paper, to compare with recent H1 experimental data for $F_L$ at fixwd W values and with collinear GRV predictions at LO and NLO approximation.
We present a method to include colour-suppressed effects in the Mueller dipole picture. The model consistently includes saturation effects both in the evolution of dipoles and in the interactions of dipoles with a target in a frame-independent way. When implemented in a Monte Carlo simulation together with our previous model of energy--momentum conservation and a simple dipole description of initial state protons and virtual photons, the model is able to reproduce to a satisfactory degree both the gamma*-p cross sections as measured at HERA as well as the total p-p cross section all the way from ISR energies to the Tevatron and beyond.
Familiar factorized descriptions of classic QCD processes such as deeply-inelastic scattering (DIS) apply in the limit of very large hard scales, much larger than nonperturbative mass scales and other nonperturbative physical properties like intrinsic transverse momentum. Since many interesting DIS studies occur at kinematic regions where the hard scale, $Q sim$ 1-2 GeV, is not very much greater than the hadron masses involved, and the Bjorken scaling variable $x_{bj}$ is large, $x_{bj} gtrsim 0.5$, it is important to examine the boundaries of the most basic factorization assumptions and assess whether improved starting points are needed. Using an idealized field-theoretic model that contains most of the essential elements that a factorization derivation must confront, we retrace the steps of factorization approximations and compare with calculations that keep all kinematics exact. We examine the relative importance of such quantities as the target mass, light quark masses, and intrinsic parton transverse momentum, and argue that a careful accounting of parton virtuality is essential for treating power corrections to collinear factorization. We use our observations to motivate searches for new or enhanced factorization theorems specifically designed to deal with moderately low-$Q$ and large-$x_{bj}$ physics.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
