Differential Cross Section Of Process Research Articles

Scattering and conversion of electromagnetic and gravitational waves by Reissner-Nordström black holes: The Regge pole description

We investigate the problem of scattering and conversion of monochromatic planar gravitational and electromagnetic waves impinging upon a Reissner-Nordstr\"om black hole using a Regge pole description, i.e., a complex angular momentum approach. For this purpose, we first compute numerically the Regge pole spectrum for various charge-to-mass ratio configurations. We then derive an asymptotic expressions for the lowest Regge poles, and by considering Bohr-Sommerfeld-type quantization conditions, obtain the spectrum of weakly damped quasinormal frequencies from the Regge trajectories. Next, we construct the scattering and conversion amplitudes as well as the total differential cross sections for different processes using both a complex angular momentum representation and a partial wave expansion method. Finally, we provide an analytical approximation of the scattering and conversion cross sections of different processes from asymptotic expressions for the lowest Regge poles and the associated residues based on the correspondence Regge poles, ``surface waves'' propagating close to the photon (graviton) sphere. This allows us to extract the physical interpretation encoded in the partial wave expansions in the high-frequency regime (i.e., in the short-wavelength regime), and to describe semiclassically with very good agreement both black hole glory and a large part of the orbiting oscillations, thus unifying these two phenomena from a purely wave point of view.

Integer and half-integer channel spins for elastic scattering cross sections

We present analytical expressions for differential cross sections and independent partial amplitudes of elastic scattering of nuclear particles for channels with a spin value of 1/2, 1, 3/2, 2 and 5/2. The independent partial amplitudes are calculated taking into account the spin-orbit splitting for arbitrary orbital angular momentum l. The analytical expressions allow one to carry out full phase shift analysis using experimental data of differential cross sections for processes with channel spins 1/2, 1, 3/2, 2 and 5/2.

Calculation of amplitudes in quantum electrodynamics

A new method of calculation of amplitudes of different processes in quantum electrodynamics is proposed. The method does not use the Feynman technique of trace of product of matrices calculation. The method strongly simplifies calculation of cross sections for different processes. The effectiveness of the method is shown on the cross-section calculation of Coulomb scattering, Compton scattering and electron-positron annihilation.

Peripheral processes 2 → 3 and 2 → 4 in QED and QCD in $$p(\bar p)p$$ high-energy collisions

Differential cross section of processes with high energy $p(\bar p)p$ collisions in frames of QED: creation of scalar, pseudoscalar and lepton pair - are considered in Weizs\"acker - Williams approximation. In frames of QCD processes with conversion of initial proton (antiproton) to fermionic jets accompanied with one gluon jet as well as the state of two gluons and quark-antiquark pair (with out rapidity gap) are considered in frames of effective Reggion action of theory of Lipatov. Process of creation of a Higgs boson accompanied with two fermionic jets is considered. The azimuthal correlation in process of two gluon jet separated by rapidity gap is investigated. Effects of gluon reggeization are taken into account. Some distributions are illustrated by numerical calculations.

Peripherical processes 2 → 3 and 2 → 4 in QED and QCD in [formula omitted] high energy collisions. Azimuthal correlation of gluon jets

Differential cross sections of processes with high-energy p ( p ¯ ) p collisions creation of a scalar, a pseudoscalar and a lepton pair - are considered in the Weizsacker – Williams approximation in QED in the QCD framework, processes with conversion of the initial proton (antiproton) to fermionic jets accompanied with one gluon jet. The process of creation of a Higgs boson accompanied with two fermionic jets is considered. The azimuthal correlation in the process of two gluon jets separated by a rapidity gap is investigated. The of gluon Reggeization effects are taken into account. Azimuthal correlation of two gluon jets, accompanied in quark-antiquark production is analyzed.

Formation of trapped surfaces in the collision of nonexpanding gravitational shock waves in an AdS4 space-time

We discuss various mechanisms of catalysis of black holes/wormholes (BH/WH) formation in particles collisions. The current paradigm suggests that BH/WH formation in particles collisions will happen when center of mass energies of colliding particles is sufficiently above the Planck scale (the transplanckian region). To estimate the BH/WH production we use the classical geometrical cross section. We confirm the classical geometrical cross section of the BH production reconsidering the process of two transplanckian particles collision in the rest frame of one of incident particles. This consideration permits to use the standard Thorne's hoop conjecture for a matter compressed into a region to prove a variant of the conjecture dealing with a total amount of compressed energy in the case of colliding particles. We calculate geometrical cross sections for different processes and for different background, in particular, for (A)dS. We show that results are in agreement with closed trapped surface (CTS) estimations though there are no general theorems providing that the BH formation follows from CTS's formation. We show that the process of BH formation is catalyzed by the negative cosmological constant and by a particular scalar matter, namely dilaton, while it is relaxed by the positive cosmological constant and at a critical value just turns off. Also we note that the cross section is sensible to the compactification of extra dimensions and to the particular brane model.

Radiative muon pair production in high-energy electron-positron annihilation process

The lowest order radiative correction to the differential cross section of process of muon pair production with the emission of a hard photon at high energy electron-positron annihilation are calculated. Taking into account the emission of additional soft and hard photon, the cross section can be put in the form of the Drell-Yan process in leading logarithmical approximation. Applying the crossing transformation, we obtain the cross section of the radiative electron-muon high-energy scattering process. Virtual and soft photon emission contributions of the nonleading form are tabulated for several typical kinematical points. The limit of the small invariant mass of a muon pair is in agreement with our previous analysis.

A UNIFIED APPROACH TO NNLO SOFT AND VIRTUAL CORRECTIONS IN ELECTROWEAK, HIGGS, QCD, AND SUSY PROCESSES

I present a unified approach to calculating the next-to-next-to-leading order (NNLO) soft and virtual QCD corrections to cross-sections for electroweak, Higgs, QCD, and SUSY processes. I derive master formulas that can be used for any of these processes in hadron–hadron and lepton–hadron collisions. The formulas are based on a unified threshold resummation formalism and can be applied to both total and differential cross-sections for processes with either simple or complex color flows and for various factorization schemes and kinematics. As a test of the formalism, I rederive known NNLO results for Drell–Yan and Higgs production, deep inelastic scattering, and W+γ production, and I obtain expressions for several two-loop anomalous dimensions and other quantities needed in next-to-next-to-leading-logarithm (NNLL) resummations. I also present new results for the production of supersymmetric charged Higgs bosons; massive electroweak vector bosons; photons; heavy quarks in lepton–hadron and hadron–hadron collisions and in flavor-changing neutral current processes; jets; and squarks and gluinos. The NNLO soft and virtual corrections are often dominant, especially near threshold, and they reduce the scale dependence of the cross-section. Thus, a unified approach to these corrections is important in the search for new physics at present and future colliders.

Impulse formalism for atom-diatom collisions.

An exact formulation of the impulse approach (IA), or quantum-mechanical spectator model, is applied to atom-diatom collisions. Results are compared with previous work on the IA, which has always involved the peaking approximation (PA). The PA is seen to overestimate (underestimate) differential cross sections for processes involving projectile atom energy loss (gain). The internal consistency of the IA is explored by subjecting it to semidetailed balancing. For small scattering angles the IA is seen to be an inadequate theory, probably due to the neglect of double- and higher-collision terms in the multiple-collision expansion of the three-body T matrix. For large scattering angles, where the IA does appear to describe the scattering process accurately, the exact calculation is shown to give the same results as when only the energy-conserving on-the-energy-shell two-body processes are considered. An accurate approximation method is also developed for rapid computation of inelastic differential cross sections. Finally, the calculated results are compared with the experimental measurements, and the need to explore two-body potentials more complicated than the hard-core potential is pointed out.

Unified Treatment of Hadronic Processes Involving High-Mass Virtual Photons

A unified treatment of the three processes (I) lepton+proton \ensuremath{\rightarrow} lepton+hadrons, (II) proton+proton \ensuremath{\rightarrow} lepton pair+hadrons, and (III) lepton pair \ensuremath{\rightarrow} hadrons is presented. Our dynamical model is an off-mass-shell bootstrap theory of the hadrons. We show that the model predicts slow ${q}^{2}$ (photon mass squared) variation of the differential cross sections for processes I and II in spite of the fact that the model requires the elastic and quasi-elastic hadronic form factors to decrease faster than any power in ${q}^{2}$. The cross section for process III, however, is predicted to decrease rapidly in ${q}^{2}$ and to violate the scaling law observed for process I. More detailed predictions of multiplicities and angular distributions of the final states are made, as well as the surprising predictions that for large ${q}^{2}$, the ratio $\frac{(\frac{d\ensuremath{\sigma}}{d{q}^{2}})(pp\ensuremath{\rightarrow}pp+\mathrm{lepton}\mathrm{pair})}{(\frac{d\ensuremath{\sigma}}{d{q}^{2}})(pp\ensuremath{\rightarrow}\mathrm{pp}\ensuremath{\pi}+\mathrm{lepton}\mathrm{pair})}$ for process II and the ratio $\frac{\ensuremath{\sigma}(\mathrm{lepton}\mathrm{pair}\ensuremath{\rightarrow}\overline{p}p)}{\ensuremath{\sigma}(\mathrm{lepton}\mathrm{pair}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}+\mathrm{real}\mathrm{photon})}$ for process III should both approach zero. The latter ratio should be comparable to 1 for ${q}^{2}\ensuremath{\simeq}6$ Be${\mathrm{V}}^{2}$.

Tests expérimentaux de certaines hypothèses de symétrie relatives aux interactions fortes

Various tests for the global symmetry and for the Salam-Polkinghorne assumption are proposed. In the high energy reactions considered, such as antibaryon production, it is expected that the global symmetry might be more apparent than in reactions involving K mesons at low energies. While the tests for the universality of the pion-hyperon coupling are described by equalities, those which apply to a comparison between the pion-hyperon and pion-nucleon couplings are expressed in terms of inequalities between cross-sections for different processes. This is a consequence of indiscernibility and of the presence of the target nucleon in the initial state. These inequalities might, however, prove to give rather simple tests as they hold independently of the number of emitted pions. The tests for the Salam-Polkinghorne assumption are chosen so as to give a lower limit on the number of Ξ's appearing in a reaction, while the previously proposed tests gave an upper limit. Finally phase space effects are briefly discussed.