Search results for "normalization"
showing 10 items of 632 documents
Renormalization of the 1S0 One-Pion-Exchange NN Interaction in Presence of Derivative Contact Interactions
2003
We use standard distorted wave theory techniques and dimensional regularization to find out solutions of the nucleon-nucleon Lippman--Schwinger equation with a kernel determined by the Weinberg's next-to-leading potential, which consists of one--pion exchange and additional contact terms with derivatives. Though for simplicity, we restrict the discussion to the $^1S_0$ channel and to contact terms containing up to two derivatives, the generalization to higher waves and/or number of derivatives is straightforward. The undetermined low energy constants emerging out of the renormalization procedure are fitted to data.
The Axial Charge Renormalization in a Relativistic Description of Finite Nuclei
1994
Starting from a realistic One-Boson-Exchange model of the nucleon nucleon interaction the relativistic mean field for nucleons is determined within the Dirac Brueckner Hartree Fock approach for finite nuclei. The matrix elements of the axial charge operator evaluated for the solutions of the Dirac equation with this selfenergy are investigated. These matrix elements are enhanced with respect to the equivalent non relativistic ones obtained from the solutions of the Schr\"odinger equation with the non relativistic equivalent potential. The present results confirm at a qualitative level the results for the axial charge renormalization obtained with perturbative approaches. However, the result…
Energy and system size dependence of subnucleonic fluctuations
2018
The energy evolution of the fluctuating proton structure is studied by solving the JIMWLK renormalization group equation. The initial condition at moderate $x$ is obtained by fitting the charm reduced cross section data from HERA, requiring that the proton size remains compatible with the diffractive vector meson production measurements. Additionally, we show that the nucleon shape fluctuations are visible in exclusive vector meson production off nuclei.
Enhanced charm hadroproduction due to nonlinear corrections to the DGLAP equations
2004
We have studied the effects of nonlinear scale evolution of the parton distribution functions to charm production in $pp$ collisions at center-of-mass energies of 5.5, 8.8 and 14 TeV. We find that the differential charm cross section can be enhanced up to a factor of 4-5 at low $p_T$. The enhancement is quite sensitive to the charm quark mass and the renormalization/factorization scales.
Precision predictions for the tt¯ production cross section at hadron colliders
2011
Abstract We make use of recent results in effective theory and higher-order perturbative calculations to improve the theoretical predictions of the top-quark pair production cross section at hadron colliders. In particular, we supplement the fixed-order NLO calculation with higher-order corrections from soft gluon resummation at NNLL accuracy. Uncertainties due to power corrections to the soft limit are estimated by combining results from single-particle inclusive and pair invariant-mass kinematics. We present our predictions as functions of the top-quark mass in both the pole scheme and the M S ¯ scheme. We also discuss the merits of using threshold masses as an alternative, and calculate …
QED radiative corrections to Virtual Compton Scattering
2000
The QED radiative corrections to virtual Compton scattering (reaction $e p \to e p \gamma$) are calculated to first order in $\alpha_{em} \equiv e^2 / 4 \pi$. A detailed study is presented for the one-loop virtual corrections and for the first order soft-photon emission contributions. Furthermore, a full numerical calculation is given for the radiative tail, corresponding with photon emission processes, where the photon energy is not very small compared with the lepton momenta. We compare our results with existing works on elastic electron-proton scattering, and show for the $e p \to e p \gamma$ reaction how the observables are modified due to these first order QED radiative corrections. We…
Pinch technique self-energies and vertices to all orders in perturbation theory
2003
The all-order construction of the pinch technique gluon self-energy and quark-gluon vertex is presented in detail within the class of linear covariant gauges. The main ingredients in our analysis are the identification of a special Green's function, which serves as a common kernel to all self-energy and vertex diagrams, and the judicious use of the Slavnov-Taylor identity it satisfies. In particular, it is shown that the ghost-Green's functions appearing in this identity capture precisely the result of the pinching action at arbitrary order. By virtue of this observation the construction of the quark-gluon vertex becomes particularly compact. It turns out that the aforementioned ghost-Green…
Flavor violation in supersymmetric SU(5) GUT at large tan beta
2001
We study flavor violation in the general SUSY SU(5) GUT assuming all the third generation Yukawa couplings to be due to the renormalizable physics above GUT scale. At large tan beta, as suggested by Yukawa unification in SU(5), sizable flavor violation in the left (right) slepton (down squark) sector can be induced in nonminimal models due to renormalization effects of down type Yukawa couplings between GUT and Planck scales, in addition to the flavor violation in the right slepton sector. The new flavor physics contribution to K-(K) over bar, B-(B) over bar mixing is small but might be of phenomenological interest in the case of b --> s gamma. The sign of the latter contribution is the sam…
Gauge-Independent Analysis of K_L --> e \mu in Left-Right Models
1997
The lepton-flavour-violating decay K_L --> e \mu is studied in detail within the context of SU(2)_R x SU(2)_L x U(1)_(B-L) models, which include heavy Majorana neutrinos. Particular attention is paid to the gauge independence of this decay process to one loop. In analogy with earlier studies on the K^0\bar{K}^0 mixing, it is explicitly shown how restoration of gauge invariance occurs in the decay amplitude containing the box diagrams, when the relevant Higgs-dependent self-energy and vertex graphs are taken into account in the on-shell skeleton renormalization scheme. Based on the analytic expressions so derived, we find that the branching ratio B(K_L --> e \mu) can be considerably enhanced…
Renormalization of relativistic baryon chiral perturbation theory and power counting
2003
We discuss a renormalization scheme for relativistic baryon chiral perturbation theory which provides a simple and consistent power counting for renormalized diagrams. The method involves finite subtractions of dimensionally regularized diagrams beyond the standard $\bar{\rm MS}$ scheme of chiral perturbation theory to remove contributions violating the power counting. This is achieved by a suitable renormalization of the parameters of the most general effective Lagrangian. In addition to simplicity our method has the benefit that it can be easily applied to multiloop diagrams. As an application we discuss the mass and the scalar form factor of the nucleon and compare the results with the e…