The dipole pomeron and pp scattering

A dipole Pomeron model is applied to high energy pp scattering. It is shown that the model reproduces both: the dip structure in the differential cross section and the break in the slope at small ¦t¦. The model indicates the existence of a hard core inside the proton.Submitted to the Symposium on Hadron-Hadron Scattering at High Energies, Liblice, Czechoslovakia, June 16–21, 1975.Helpful discussions with A. I.Bugrij, N. A.Kobylinsky, V. V.Serebryakov and B. V.Struminsky are acknowledged.     

Proton-proton scattering without Coulomb force renormalization

We demonstrate numerically that proton-proton (pp scattering observables can be determined directly by standard short-range methods using a screened pp Coulomb force without renormalization. In the examples the appropriate screening radii are given. We also numerically investigate solutions of the 3-dimensional Lippmann-Schwinger (LS) equation for a screened Coulomb potential alone in the limit of large screening radii and confirm analytically predicted properties for off-shell, half-shell and on-shell Coulomb t -matrices. These 3-dimensional solutions will form a basis for a novel approach to include the pp Coulomb interaction into the 3N Faddeev framework.     

Proton-proton inelastic scattering at 0.5 TeV

We have measured at 500 GeV the cross section $\text{d}{}^2\text{σ}\text{dt dM}{}_{\mathrm{X}}{}^2$ for the inclusive reaction p + p → + X. We determine the mass spectrum of the diffractive peak to be $\text{1}\text{M}{}^{\mathrm{3.8\pm 0.2}}$ and the scaling part of the cross section to be dσ/dM_X² = (15.7±1.1)/smb/GeV².     

Search for glue balls in a pomeron pomeron scattering experiment

The exclusive reactionpp→ppπ⁺ π^? has been studied using the SFM spectrometer at ISR energies of \(\sqrt s = 24\) and 63 GeV. The cross section in the double pomeron exchange region defined by |x _p |>0.9, |y _π |<1 is 28±6, 23(+13, ?6) and 29(+29, ?10)μb, respectively. The ππ mass spectrum is dominated by an 1/m _ππ ² part, as expected for pomeron pomeron scattering. In addition, thef(1, 270) resonance is clearly distinguished. There are no further resonance signals, which could be assigned to glueball candidates expected in the 1,000 MeV region. Compared to photon photon scattering, the ratio of continuum tof-resonance production cross sections is significantly larger in pomeron pomeron scattering.     

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.     

Proton-proton scattering from 0.35 to 1.0 MeV

Differential cross sections for the scattering of protons by protons have been measured at energies from 0.35 to 1.0 MeV over an angular range from 24° to 110° in the c.m. system with an absolute accuracy of 0.2 %. Special care was taken at energies around the interference minimum where, due to the extremely small values of the cross section, the accuracy has been 0.8 % at θ_{c.m. = 90°}. The resulting value for the minimum energy is E_IM = 382.48 ± 0.10 keV. The high accuracy could be achieved mainly by using a new double compensated calorimeter for the current integration.     

Proton-proton scattering above 3 GeV/c

A large set of data on proton-proton differential cross sections, analyzing powers and the double-polarization parameter A_NN is analyzed employing the Regge formalism. We find that the data available at proton beam momenta from 3GeV/c to 50GeV/c exhibit features that are very well in line with the general characteristics of Regge phenomenology and can be described with a model that includes the $ \rho$ \rho , $ \omega$ \omega , f₂, and a₂ trajectories and single-Pomeron exchange. Additional data, specifically for spin-dependent observables at forward angles, would be very helpful for testing and refining our Regge model.     

The pomeron in elastic meson-baryon scattering

We show that a pomeron (P) trajectory with α_P(t) ≈ 1.07 + 0.22t provides a simple and satisfactory fit to π^±p and K^±p elastic scattering data (as well as pp and $\text{p}$p considered in an earlier publication) for |t| < 1.2 GeV², including the rising total cross sections. The destructive term needed to explain the diffraction minimum in pp may be explained as a weak P ? P cut effect provided that the Gribov vertices are given suitable structure, and the prediction is then made that similar minima should be observed in meson-baryon scattering at FNAL somewhere in the region 1.5 < |t| < 2.5 GeV². The P ? P cut does not seem to be related (at least directly) to the unitarization effects which must eventually make σ_tot ～ log²s (but not until s > 10⁸GeV²). Thus the “effective” J-plane singularity structure, at currently available energies seems to be much simpler than it can be asymptotically.     

Proton-proton elastic scattering and nucleon resonance production at high energies

Angular distributions of proton-proton elastic scattering have been measured for incident beam momenta of 10.0, 12.0, 14.2 and 24.0 GeV/c over a range of lab scattering angles from 12 to 152 mrad. This is equivalent to a range of four-momentum transfer squared from about 0.1 to 6.7 GeV² at the highest momentum. Nucleon resonance production in the two-body reaction p + p → p + X has been studied at 24.0 GeV/c incident momentum from 13.5 to 112 mrad by measuring the proton momentum spectra from the elastic peak down to a momentum corresponding to a missing mass of about 2.6 GeV. The new data are compared with previous results and theoretical models.     

The pomeron colour structure and hadron scattering on the six-quark deuteron configuration

The pomeron colour structure provides some contribution to the elastic hadron-deuteron amplitude not contained in the Glauber like approach. This contribution is very sensitive to the short distance behaviour of the deuteron wave function and poses one to fix with a high precision a size of the deuteron six-quark bag.     

Proton-proton elastic scattering analyzing power in the 2.16 to 2.28 GeV energy region

We analyze the possibility of testing local Lorentz invariance from the observation of tau decays. Future prospects of probing distances below the electroweak characteristic scale are discussed.     

Triple pomeron vertex and complex pomeron trajectories

Complex Pomeron trajectories can give rise to (log s)²-shrinkage of the diffraction peak. With factorization, one obtains consistency with the energy momentum sum rule in the triple-Regge limit provided the total cross section approaches a constant or increases less fast than $\text{(}\text{log}\text{s)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$.     

Models for the pomeron and low energy K+p scattering

Using a simple s-channel unitarity model for the pomeron, abstracted from a number of more ambitious schemes, we compute the pomeron contribution using low-energy data in K⁺p scattering. The agreement with experiment obtained is qualitatively fair but in detail substantial discrepancies appear. Possible reasons for these discrepancies and suggestions for their future investigation are presented.     

Forward gluon production in hadron–hadron scattering with pomeron loops

We discuss new physical phenomena expected in particle production in hadron–hadron collisions at high energy, as a consequence of pomeron loop effects in the evolution equations for the color glass condensate. We focus on gluon production in asymmetric, ‘dilute–dense’, collisions: a dilute projectile scatters off a dense hadronic target, whose gluon distribution is highly evolved. This situation is representative for particle production in proton–proton collisions at forward rapidities (say, at LHC) and admits a dipole factorization similar to that of deep inelastic scattering (DIS). We show that at sufficiently large forward rapidities, where the pomeron loop effects become important in the evolution of the target wavefunction, gluon production is dominated by ‘black spots’ (saturated gluon configurations) up to very large values of the transverse momentum, well above the average saturation momentum in the target. In this regime, the produced gluon spectrum exhibits diffusive scaling, so like DIS at sufficiently high energy.     

Unitarity and the BFKL pomeron

High energy onium-onium scattering is calculated as a function of impact parameter in the one- and two-pomeron exchange approximation. Difficulties with using the multiple scattering series to unitarize single pomeron exchange at high energy are noted. An operator formalism which sums all numbers of pomeron exchange is given. A toy model which has a similar operator structure at high energy as QCD is presented and the S-matrix is evaluated. Estimates of the energies and impact parameters at which blackness occurs in onium-onium scattering are given. It is emphasized that the problem of unitarity in high energy onium-onium scattering can be solved in a purely perturbative context, with a non-running coupling if the onium is heavy enough.     

Diffusion and the BFKL pomeron

We study the high energy behaviour of elastic scattering amplitudes within the leading logarithm approximation. In particular, we cast the amplitude in a form which allows us to study the internal dynamics of the BFKL Pomeron for general momentum transfer. We demonstrate that the momentum transfer acts as an effective infrared cut-off which ensures that the dominant contribution arises from short distance physics.