3D black holes on a 2-brane in 4D Minkowski space

We investigate three-dimensional black hole solutions in the realm of pure and new massive gravity in 2+1 dimensions induced on a 2-brane embedded in a flat four-dimensional spacetime. There is no cosmological constant neither on the brane nor on the four-dimensional bulk. Only gravitational fields are turned on and we indeed find vacuum solutions as black holes in 2+1 dimensions even in the absence of any cosmological solution. There is a crossover scale that controls how far the three- or four-dimensional gravity manifests on the 2-brane. Our solutions also indicate that local BTZ and SdS₃ solutions can flow to local four-dimensional Schwarzschild-like black holes, as one probes from small to large distances, which is clearly a higher dimensional manifestation on the 2-brane. This is similar to the DGP scenario where the effects of extra dimensions for large probed distances along the brane manifest.     

Black Hole Scattering via Spectral Methods

We present an alternative method to solve the problem of scattering by a black hole by adapting the spectral code originally developed by Boyd (Comp Phys 4:83, 1990). In order to show the effectiveness and versatility of the algorithm, we solve the scattering by Schwarzschild, standard acoustic, and charged black holes. We recover the partial and total absorption cross sections and, in the case of charged black holes, the conversion factor of eletromagnetic and gravitational waves. We also study the exponential decay of the reflection coefficient, which is a general feature of any scattering problem.     

LargeP T photoproduction in the hard scattering expansion

Largep _T photoproduction is studied in the hard scattering expansion, including both three- and four-jet processes. The higher twist corrections (∝p _T ^?6 andp _T ^?8 ) to the basic QCD hard scattering process (∝p _T ^?4 ) are estimated using the constituent interchange model and the various terms compared. Both single jet inclusive cross sections and single particle inclusive π⁰ cross sections are evaluated, the latter using scale violating fragmentation functions. We find that the higher twist terms are significant at present energies, particularly for three-jet events, though the four-jet anomalous photon contribution can be measured. Three-jet QCD processes require considerably higher energies to provide a significant contribution to the cross section. Methods of separating the different processes experimentally are discussed.     

Low-pt jets and the rise with energy of the inelastic cross section

The contribution of QCD jets to the rise with energy of the inelastic cross section is discussed quantitatively and found to be large. It is seen that the inclusive jet yield is the fastest growing component of the total cross section. The dependence of this yield upon the rapidity cuts, the choice of parton densities, the QCD scale Q² and the transverse momentum cutoff p_cut are examined. At higher energies, multiple parton scattering processes are seen to be non-negligible. Extrapolations of the low-p_t jet yield to the Tevatron are presented also.     

Resonant scattering of light in a near-black-hole metric

We show that low-energy photon scattering from a body with radius R slightly larger than its Schwarzschild radius r _s resembles black-hole absorption. This absorption occurs via capture resulting in one of the many long-lived, densely packed resonances that populate the continuum. The lifetimes and density of these meta-stable states tend to infinity in the limit r _s →R. We determine the energy-averaged cross section for particle capture into these resonances and show that it is equal to the absorption cross section for a Schwarzschild black hole. Thus a non-singular static metric may trap photons for arbitrarily long times, making it appear completely ‘black’ before the actual formation of a black hole.     

New physics, the cosmic ray spectrum knee, and pp cross section measurements

We explore the possibility that a new-physics interaction can provide an explanation for the knee just above 10⁶ GeV in the cosmic ray spectrum. We model the new-physics modifications to the total proton–proton cross section with an incoherent term that allows for missing energy above the scale of new physics. We add the constraint that the new physics must also be consistent with published pp cross section measurements, using cosmic ray observations, an order of magnitude and more above the knee. We find that the rise in cross section required at energies above the knee is radical. The increase in cross section suggests that it may be more appropriate to treat the scattering process in the black disc limit at such high energies. In this case there may be no clean separation between the standard model and new-physics contributions to the total cross section. We model the missing energy in this limit and find a good fit to the Tibet III cosmic ray flux data. We comment on testing the new-physics proposal for the cosmic ray knee at the Large Hadron Collider.     

Two body reactions and the quark model

A simple quark model for two-body hadronic amplitudes is presented and applied to pp ($\text{p}\text{p}$) and K^±p elastic scattering. Hadronic processes are described in terms of quark-quark scattering, using Glauber theory to take into account the effects of multiple scattering. Exchange degenerate Regge poles are introduced at the quark level. A predictive model for Regge cuts is obtained. It has some features in common with the dual absorption model in its correlation of dip structure and shrinkage in elastic processes with the exoticity of the s-channel but also significant differences, for example in the interpretation of the $\text{p}\text{p}$ dip. The qualitatively different structure in the pp differential cross section is also reproduced. It breaks exchange degeneracy in a well-defined way and in doing so offers an explanation of the differences between pp and K⁺p total cross sections. The difference in their differential cross sections is a natural consequence of the model and structure similar to the pp structure is predicted to appear in the K⁺p differential cross section in the region t ≈ ?2(GeV/c)².     

The nonlinear effects of quantum electrodynamics at high energies

In this paper we considere ⁺ e ^? scattering with intermediate photon-photon scattering as a possibility for getting information about the nonlinear effects of quantum electrodynamics (QED) at high energies. This process is a higher-order correction to double bremsstrahlung. However, these two processes have quite different behaviour with the photon-photon scattering angle. Here we calculate the unpolarized differential cross section of thee ⁺ e ^? scattering with intermediate γγ scattering and also the interference terms with the double bremsstrahlung. Moreover, we show that the sum of these two contributions predominates over the contribution of the double bremsstrahlung for sufficiently large scattering angles of the photons. This result enables us to extract the differential cross section of the γγ scattering. Through extrapolation to different kinematical conditions we can get the cross sections for nearly real photon-photon scattering, photon splitting and Delbrück scattering. As a quantitative example we use the result for a test of the electron propagator in a gauge-invariant way with the usual minimal interaction. We give also numerical examples of this test, which will improve the present values of the testing parameters.     

The scattering of strings by a black hole

We study the elastic and inelastic scattering of strings by a Schwarzschild's black hole. Pair creation takes place (and in all the modes) as a consequence of the composite structure (oscillator modes) of the string. The S-matrix amplitudes including the pair-creation rate are found at first order in √α'/R_S (√α' = Planck's length and R_S = Schwarzschild's radius). Explicit computations are made in the weak-field expansion in powers of (R_S/b)^D−3 (b = impact parameter of the string center of mass). The deflection angle and cross sections are found. The quantum string corrections to the gravitational analogue of Rutherford's scattering are computed (these are of order α'²). The pair-creation or radiation amplitude we find here is of order α', it is non-thermal and of different origin than Hawking radiation.     

The reaction e− + p → Λ + ν and the contributions of the individual form factors to the differential cross section

We calculate the differential cross section for the weak, strangeness changing, electron scattering process, e⁻ + p → Λ + ν, for incoming electron energies of 0.5, 1.0, 2.0, 4.0, and 6.0 GeV. We obtain as well contributions of the individual form factors to the differential cross sections. We find that the differential cross sections peak as the maximal scattering angle for the Λ is approached and that the peak height increases as the electron energy is increased. The behavior of the differential cross section near the maximal angle is discussed as is the possibility of observing this reaction in a facility such as TJNAF.     

Dirac quantization of open p-brane

We give the scheme of Dirac quantization of open p-brane in the D-brane background. Treating the mixed boundary conditions as primary constraints, we get a set of secondary constraints, then the constraints conditions are shown to be equivalent to orbifold conditions imposed on normal p-brane modes.     

Compton and double-compton scattering processes at colliding electron-photon beams

Radiative corrections to the Compton scattering cross section are calculated in the leading and next-to-leading logarithmic approximations in the case of colliding high-energy photon-electron beams. Radiative corrections to the double-Compton scattering cross section in the same experimental setup are calculated in the leading logarithmic approximation. We consider the case where no pairs are created in the final state. We show that the differential cross section can be written in the form of the Drell-Yan process cross section. Numerical values of the K-factor and the leading-order distribution on the scattered electron energy fraction and scattering angle are presented.     

Absorption/Scattering of Scalar Waves by Dilatonic Black Hole

We investigate the scattering and absorption cross sections of scalar waves by Garfinkle-Horowitz-Strominger (GHS) black hole spacetime with partial wave method. We find that the total absorption cross section oscillates around the geometric optical value, and the scattering angle width becomes narrower and the damping oscillation pattern becomes more complex as l increases. With fixed frequency ω, the main glory peak value becomes higher and the glory width becomes wider as the magnetic parameter a increases.     

Anomaly free effective action for the elementary M5-brane

We construct an effective action describing an elementary M5-brane interacting with dynamical eleven-dimensional supergravity, which is free from gravitational anomalies. The current associated to the elementary brane is taken as a distribution valued δ-function on the support of the 5-brane itself. Crucial ingredients of the construction are the consistent inclusion of the dynamics of the chiral two-form on the 5-brane, and the use of an invariant Chern-kernel allowing to introduce a D=11 three-form potential which is well-defined on the worldvolume of the 5-brane.     

Proton-proton elastic scattering via the Trojan horse method

We address a successful indirect technique, the Trojan horse method, which allows one to measure the bare nucleus cross section for rearrangement reactions down to astrophysical energies. In particular, we consider here the application of the method to the p-p elastic scattering. This represents an important test of the main feature of the method, namely the suppression of Coulomb effects in the entrance channel due to off-energy-shell effects. In contrast to the on-energy-shell case, the extracted p-p cross section does not exhibit the Coulomb-nuclear interference minimum, as predicted by the half-off-energy shell calculations. This hypothesis is strengthened by the agreement between the Trojan horse p-p data and the calculated on-energy-shell n-n, n-p and nuclear p-p cross sections.     

Cross Section Enhancement in pd Reactions at Higher Energy

Cross sections of pd breakup reaction at E _p = 250 MeV were measured systematically in single-proton detection and in two-proton coincidence detection. Measured cross section is up to two times higher than calculated ones. The enhancement of breakup cross section is similar to reported enhancement in pd elastic scattering cross section. Origins of this enhancement are discussed.     

Conformal symmetry for rotating D-branes

We apply the Kerr/CFT correspondence to the rotating black p-brane solutions. These solutions give the simplest examples from string theory point of view. Their near horizon geometries have structures of AdS, even though black p-brane solutions do not have AdS-like structures in the non-rotating case. The microscopic entropy which can be calculated via the Cardy formula exactly agrees with Bekenstein–Hawking entropy.     

Virtual Compton scattering off the pseudoscalar meson octet

We present a calculation of the virtual Compton scattering amplitude for the pseudoscalar meson octet in the framework of chiral perturbation theory at O(p ⁴). We calculate the electromagnetic generalized polarizabilities and compare the results in the real Compton scattering limit to available experimental values. Finally, we give predctions for the differential cross section of electron-meson bremsstrahlung.     

Heterotic p-branes from massive sigma models

We explicitly construct massive (0,4) supersymmetric ADHM sigma models which have heterotic p-brane solitons as their conformal fixed points. These yield the familiar gauge 5-brane and a new 1-brane solution which preserve half and a quarter of the space-time supersymmetry, respectively. We also discuss an analogous construction for the type 11 NS-NS p-branes using (4,4) supersymmetric models.     

CompleteO(α s 2 ) corrections to (2 + 1) jet cross sections in deep inelastic scattering

Complete next-to leading order QCD predictions for (2+1) jet cross sections and jet rates in deep inelastic scattering (DIS) based on a new parton level Monte Carlo program are presented. All relevant helicity contributions to the total cross section are included. Results on total jet cross sections as well as differential distributions in the basic kinematical variablesx, W ² andQ ² are shown for HERA energies and for the fixed target experiment E665 at FERMILAB. We study the dependence on the choices of the renormalization scale μ _R and the factorization scale μ _F and show that the NLO results are much less sensitive to the variation of μ=μ _F =μ _R than the LO results. The effect of an additionalp _T cut to our jet definition scheme is investigated.