Coulomb Interference Region Research Articles

High-Beta Optics and Running Prospects

Dedicated high-beta optics are used to make forward proton scattering measurements possible at the LHC. Following a short general introduction and history of special high-beta optics and running conditions, we describe the two types of special high-beta runs planned for 2018. A run at top energy at β y * = 90 m for elastic and diffractive scattering, and a low energy run to measure the rho-parameter in the Coulomb interference region.

AMPLITUDES IN pp AND ${\rm \bar{p}p}$ SCATTERING

Solutions for the amplitudes that give accurate description of pp and [Formula: see text] scattering at high energies are investigated, with particular attention given to the properties of their zeros and slopes, whose determination is required for the study of the Coulomb interference region. Proper extrapolations of these quantities to the LHC energies are important for the analysis of the forthcoming experiments.

The elastic [formula omitted] differential cross section measurements at the CERN [formula omitted] and the real part of the scattering amplitude

The experimental data of the p p differential cross section in the energy range ∝ s = 541–546 GeV at the CERN Sp p S including the recent precise UA4/2 experiment in the Coulomb interference region are analyzed to obtain information on the real part of the scattering amplitude at the whole region of the momentum transfer of the experimental data points. We make a fit to the experimental data by using the real part of the scattering amplitude given by the derivative dispersion relation (DDR). We obtrained ϱ = 0.120 −0.003 +0.017 for the ratio of the real part to the imaginary part of the forward scattering amplitude.

The real part of the elastic-scattering amplitude at the $$S\bar ppS$$ and predictions at LHC and SSCand predictions at LHC and SSC

A precise measurement of\(\bar pp\) elastic scattering in the Coulomb strong-interaction interference region was performed at the CERN\(S\bar ppS\) Collider at a centre-of-mass energy of 541 GeV. The ratio of the real-to-imaginary part of the forward elastic-scattering amplitude was found to be ρ=0.135±0.015. The slope of the exponential fall-off of the strong-interaction part was also measured to beb=15.5±0.1 GeV−2. Using this new result, an overall fit to the data on the total cross-section and on the real part for\(\bar pp\) and pp was performed using dispersion relations. Numerical predictions are presented for total cross-sections at LHC and SSC energies.

Comparison of theoretical predictions from the impact picture with the recent UA4 data

The theoretical predictions of the proton-antiproton elastic scattering cross section is compared with the recent UA4 data in the Coulomb interference region at the center-of-mass energy of 541 GeV. The agreement is excellent. A plot of the ratio of the experimental data to the theoretical prediction shows an oscillation of about (2–3)%. Further experimental studies are needed to ascertain whether this oscillation is actually present.

ERRATA: REAL PART OF THE ${\bar p}p$ ELASTIC SCATTERING AMPLITUDE AT $\sqrt{s} = 546~{\rm Gev}$

In order to get an accurate determination of the real part of the elastic scattering amplitude at , the Genoa–Palaiseau–Roma–Valencia collaboration plans to take experimental data on dσ/dt in the Coulomb interference region. We present detailed theoretical predictions for this cross-section. These predictions can be compared directly with the forthcoming data.

REAL PART OF THE $\bar pp$ ELASTIC SCATTERING AMPLITUDE AT $\sqrt{s} = 546\, {\rm GeV}$

In order to get an accurate determination of the real part of the [Formula: see text] elastic scattering amplitude at [Formula: see text], the Genoa–Palaiseau–Roma–Valencia collaboration plans to take experimental data on dσ/dt in the Coulomb interference region. We present detailed theoretical predictions for this cross-section. These predictions can be compared directly with the forthcoming data.

Crossing-odd effects in soft nucleon collisions

A complete set of the data onpp andp\(\bar p\) scattering including measurements in the Coulomb interference region are analised to discover crossingodd effects in soft collisions. It is shown that the odderon is unable to produce a significant increase in ReA/ImA at\(\sqrt s = 546\) GeV. Moreover, the data give preference to that odderon which makes negative contribution to Re\(A_{p\bar p} \) and ceases the decrease of difference inp\(\bar p\) andpp total cross-sections.

The real part of the proton-antiproton elastic scattering amplitude at the centre of mass energy of 546 GeV

Abstract Proton-antiproton elastic scattering was measured at the CERN SPS Collider at the centr-of-mass energy s =546 GeV in the Coulomb interference region. The data provide information on the phase of the hadronic amplitude in the forward direction. The conventional analysis gives for the ratio ϱ of the real to the imaginary part of the hadronic amplitude the result ϱ=0.24±0.04.

Impact picture in the coulomb interference region at high energies

We present the predictions on pp̄ elastic differential cross sections in the Coulomb interface region for energies 0.546 to 2.0 TeV on the basis of the impact picture.

MEASUREMENT OF ANN FOR [MATH] ELASTIC SCATTERING IN THE COULOMB INTERFERENCE REGION

ANN for [MATH] elastic scattering has been measured at 1.47 and 1.28 GeV/c in the Coulomb interference region. We present preliminary results of the measurement.

A new determination of the πN sigma term using hyperbolic dispersion relations in the (ν2,t) plane

Dispersion relations in the (ν2,t) plane along hyperbolas are used in order to extrapolate the invariant isospin-even πN amplitude D+(ν2,t) to the Cheng-Dashen point, ν=0, t=2μ. The fluctuation of the results obtained with different hyperbolas gives a realistic estimate of the errors, except for errors of the partial wave solution and of the ππ $$ - N\bar N$$ amplitudes assumed at t < 4μ2 —If our ππ $$ - N\bar N$$ partial waves are used, which are based on the ππs-wave scattering length a 0 0 =0.28 μ-1, the result for the sigma term is 64±8 MeV, in agreement with earlier determinations.—The discrepancy with the theoretical prediction σπN≈ 30 MeV is smaller by only 8 MeV, if our $$ - N\bar N$$ amplitudes are modified in such a way that the threshold behaviour of the ππs-wave agrees with Weinberg's prediction a 0 0 =0.16 μ-1. Further progress depends on new accurate experimental π±p scattering data in the Coulomb interference region at low energies.

Elastic pp scattering at 1.463 GeV/ c in the Coulomb interference region

The differential cross section for elastic pp scattering has been measured at 800 MeV, for laboratory angles ranging between 1.2° and 4.3° (lab). The ratio ϱ of the real to imaginary parts of the forward spin-independent scattering amplitude and the combined magnitudes of the forward double spin-flip amplitudes have been extracted from the data and are compared with the results of recent forward dispersion relation calculations and phase shift analyses.

The nucleon nucleon interaction

In this session we have 25 contributed papers. Those concerned with the new results of the Basque group (n-p elastic differential and total cross sections in the energy range 210–500 MeV) and of the Geneva group (measurement of correlation parameters in p−p elastic scattering between 400–600 MeV) were reported on by D. Bugg 1). The study of the reaction app → π + d was described by R. Hess 2). Contributions 3E1 on elastic pp scattering at 1.463 GeV c in the Coulomb interference region (G. Pauletta et al.), 3E3 on a measurement of A nn in 6 GeV c np elastic scattering (D.G. Crabb et al.), 3E18 on an analysis of the singlet and triplet contributions to the total cross section differences Δσ T and Δσ L in a pp scattering between 1 and 3 GeV c (C.L. Hollas) and 3E22 on the np analyzing power at LAMPF energies (C.R. Newson et al.) will be presented by their authors. Due to lack of time and space, I shall be able to summarize only a few of the remaining papers if I want to remain intelligible. I apologize to the authors whose papers will not be reviewed here.

Measurements of π −p elastic scattering in the coulomb interference region at high energies

The differential cross section has been measured at 30, 50, 80, 100, 120 and 140 GeV/ c for 0.002 < | t| < 0.04 ( GeV/ c) 2. The results show that the π −p real part goes from negative to positive values below 80 GeV/ c. The slope parameter in the t-region measured is significantly higher than what has been found − t = 0.2 (GeV/ c) 2.

Polarization in elasticp−pandp−nscattering at 1.03 GeV

The polarization in elastic proton-proton and proton-neutron scattering has been measured at an incident kinetic energy of 1.03 GeV. The proton-proton data have a significantly higher precision than previously obtained in this energy range and extend into the Coulomb interference region. The proton-neutron measurement is the first in this energy region. The results are compared with existing nucleon-nucleon phase shifts solutions.NUCLEAR REACTIONS Polarization in $\mathrm{pp}$ and $\mathrm{pn}$ scattering, GeV energies, measurement.

Evaluation of the medium-energy real parts of the forward p-4He elastic scattering amplitude from dispersion relations

The dispersion relation method, together with the conformal mapping technique, is used to estimate the real part of the forward p-4He elastic scattering amplitude in the proton laboratory energy range 1.5-10 GeV. The predictions obtained rest heavily on the phase-shift input and need testing by direct measurements of the real parts in experiments performed in the Coulomb interference region.

Small-angle π − p elastic scattering measurements

We have measured small angle elastic pion-proton scattering in 40 and 50 GeV c π − beams at Serpukhov. Analysis of the data in the Coulomb interference region yields a value for the ratio of the real to the imaginary part of the strong amplitude, ϱ(0)=−0.074 ± 0.033 at 40 GeV/ c and ϱ(0)=−0.006 ±0.026 at 50 GeV/ c

The nn scattering amplitude at 845 MeV/ c

Experimental data on dd small-angle elastic scattering in the Coulomb interference region are analysed to yield the dd scattering amplitude. This amplitude is then expressed in terms of the nucleon-nucleon scattering amplitudes and the Glauber correction. The value for the nn scattering amplitude found is shown to be in good agreement with the pp amplitude.

Spin effects in proton-proton elastic scattering near the forward direction

We have analysed the several sets of experimental data on pp elastic scattering in the Coulomb interference region in the range p lab between 9 and 500 GeV/ c, in order to estimate the size of the spin dependent part of the strong amplitude. Calling β the ratio of this spin-dependent part to the spin-dependent amplitude in the forward direction, we find all the data strongly suggest but do not conclusively prove a non-negligible β whose value is around 10% and approximately constant with energy. This result cannot be explained theoretically in terms of exchange of any simple factorising Regge pole. We suggest important pomeron cut contributions. Implications of our analysis for some experiments at ISR energies which appear to give rising total cross sections are discussed.