In a special run of the LHC with $\beta^\star = 2.5~$km, proton-proton elastic-scattering events were recorded at $\sqrt{s} = 13~$TeV with an integrated luminosity of $340~\mu \textrm{b}^{-1}$ using the ALFA subdetector of ATLAS in 2016. The elastic cross section was measured differentially in the Mandelstam $t$ variable in the range from $-t = 2.5 \cdot 10^{-4}~$GeV$^{2}$ to $-t = 0.46~$GeV$^{2}$ using 6.9 million elastic-scattering candidates. This paper presents measurements of the total cross section $\sigma_{\textrm{tot}}$, parameters of the nuclear slope, and the $\rho$-parameter defined as the ratio of the real part to the imaginary part of the elastic-scattering amplitude in the limit $t \rightarrow 0$. These parameters are determined from a fit to the differential elastic cross section using the optical theorem and different parameterizations of the $t$-dependence. The results for $\sigma_{\textrm{tot}}$ and $\rho$ are \begin{equation*} \sigma_{\textrm{tot}}(pp\rightarrow X) = \mbox{104.7} \pm 1.1 \; \mbox{mb} , \; \; \; \rho = \mbox{0.098} \pm 0.011 . \end{equation*} The uncertainty in $\sigma_{\textrm{tot}}$ is dominated by the luminosity measurement, and in $\rho$ by imperfect knowledge of the detector alignment and by modelling of the nuclear amplitude.
The measured total cross section. The systematic uncertainty includes experimental and theoretical uncerainties.
The measured total cross section. The systematic uncertainty includes experimental and theoretical uncerainties.
The rho-parameter, i.e. the ratio of the real to imaginary part of the elastic scattering amplitude extrapolated to t=0. The systematic uncertainty includes experimental and theoretical uncerainties.
A measurement of the proton-proton elastic differential cross section at 50 GeV/ c incident momentum in the momentum transfer range 0.8<| t |<4.0 (GeV/ c ) 2 is presented. The data are compared to pp data at lower and higher energies, and to some model predictions.
NUMERICAL VALUES OF DATA SUPPLIED BY D. IMRIE. ERROR CONTAINS BOTH STATISTICAL AND SYSTEMATICS EXCEPT THE OVERALL NORMALIZATION ERROR.
Differential cross sections have been measured for nucleon-isobar production and elastic scattering in p−p interactions from 6.2 to 29.7 GeVc in the laboratory angle range 8<θsc<265 mrad. N*' s at 1236, 1410, 1500, 1690, and 2190 MeV were observed. Computer fits to the mass spectra under varying assumptions of resonance and background shapes show that conclusions on t and s dependence are only slightly affected despite typical variations in absolute normalization of ± 35%. Logarithmic t slopes in the small- |t| range are ∼15 (GeVc)−2 for the N*(1410), ∼5 (GeVc)−2 for the N*'s at 1500, 1690, and 2190 MeV, and ∼9 (GeVc)−2 for elastic scattering. Also for the small- |t| data, cross sections for N*'s at 1410, 1500, 1690, and 2190 MeV and for elastic scattering vary only slightly with Pinc consistent with the dominance of Pomeranchuk exchange and with diffraction dissociation. A fit of N*(1690) total cross sections to the form σ∝P−n gives n=0.34±0.06, while for elastic scattering n=0.20±0.05. For the N*(1690) the effective Regge trajectory has the slope αeff′(0)=0.38±0.17. When compared with N* production in π−, K−, and p¯ beams these data also agree with approximate factorization of the Pomeranchuk trajectory. N*(1236) cross sections are consistent with other measurements at similar momenta. For −t>1 (GeVc)−2, elastic scattering cross sections decrease approximately as Pinc−2, and they and N*(1500)− and N*(1690)− production cross sections have t slopes consistent with 1.6 (GeVc)−2.
No description provided.
No description provided.
No description provided.
About 3700 two-prong and 5600 four-prong events of 10-GeV/c pp interactions in the Saclay 81-cm hydrogen bubble chamber have been measured and analyzed. The reliability of the identification of the different final states has been checked using Monte Carlo-generated events. For the channels accessible to analysis, cross sections and invariant-mass distributions are given. The c.m. angular distributions and the mean values of the transverse momentum for all final-state particles are shown and discussed. Production of Δ++(1236) accounts for about 30% of the cross section σ(pp→pnπ+)=4.1±0.4 mb. About 50% of the cross section σ(pp→ppπ+π−)=2.4±0.2 mb can be accounted for by Δ++ production. Production of nucleon isobars at 1450, 1520, and 1730 MeV and their subsequent decay into pπ+π− are investigated. Their cross sections, t dependences, and branching ratios are determined, using a one-pion-exchange model (OPEM) for calculating the background distributions. The production of resonances decaying into pπ− at 1236, 1500, and 1690 MeV is seen, and cross sections are given. Resonance production in the ppπ+π−π0 and pnπ+π+π− reactions is studied using background curves calculated with a model based on simple parametrizations of the c.m. momentum distributions. The production of nucleon isobars accounts for nearly 100% of these reactions. For the reactions pp→ppω, ppη, and ppf0, the cross sections found are 0.16±0.03, 0.16±0.07, and 0.10±0.04 mb, respectively, corrected for unobserved decay modes. It is shown that most of the gross features of the pion-production reactions can be explained by the OPEM with the form factors of Ferrari and Selleri.
No description provided.
A description is given of an experiment to study elastic scattering of π ± , K ± and p on protons at c.m. scattering angles from 45° to 100° at incident laboratory momenta 20 GeV/ c and 30 GeV/ c . The corresponding t range is from −6.2 (GeV/ c ) 2 to −28 (GeV/ c ) 2 . There are no previous observations for these reactions in this t range. High intensity and large geometrical acceptance were required in order to measure the low cross sections. The experiment used a double-arm spectrometer. MWPCs were used for reconstruction, and threshold and differential Čerenkov counters for identification. Scintillation counters, Čerenkov counters and a hadron calorimeter were used in the trigger. The trigger logic utilized specially designed matrices and a hard wired microprocessor. The π − p elastic scattering cross sections follow approximately the dimensional counting rule from 3.5 GeV/ c .and up to 30 GeV/ c . The cross sections decrease by seven orders of magnitude in this energy range. The data is compared to quark models. None of these models give a comprehensive description of the results. However, some modifications to these models improve their consistency with the data.
EARLIER RESULTS GIVEN IN 'A'.
No description provided.
EARLIER RESULTS GIVEN IN 'A'.
Results are presented from experiment WA7 at the CERN SPS, which has measured the elastic differential cross sections of π ± p, K ± p, p p and pp at incident momen ta of 20, 30 and 50 GeV/ c . The measurements cover the momentum transfer range 0.5 < | t | < 8 (GeV/ c ) 2 , corresponding to c.m. scattering angles between 10° and 50°. The experimental set-up, trigger logic and data analysis are described. The experimental results are compared with existing meson-proton and nucleon-proton data at lower and higher energies covering the medium- and large-| t | region. Some prominent models and their predictions for elastic scattering at WA7 energies and beyond are reviewed, with emphasis on geometrical scaling, factorizing eikonal models, lowest-order QCD and other dynamical exchange-type models. Results for p p two-body annihilation into π − π + and K − K + at 30 and 50 GeV/ c , obtained in parallel with the elastic p p data, are also presented.
No description provided.
No description provided.
No description provided.
Data are presented from a high statistics bubble chamber experiment to study K − p interactions in the c.m. energy range 1775 to 1957 MeV. For the reactions K − p → K − p, K − p → K 0 n , K − p → Λπ 0 and K − p → Σ ± π ∓ channel cross sections, differential cross sections and, where appropriate, polarisation distributions have been obtained. The channel cross sections for K − p → Σ 0 π 0 are presented. In general the results are in agreement with those previously published although a significant discrepancy has been found in the Σ ± π ∓ cross sections at the lower energies. New measurements of the Σ ± lifetimes have also been obtained ( τ Σ − = 1.49 ± 0.03 × 10 −10 sec, τ Σ + = 0.807 ± 0.013 × 10 −10 sec).
No description provided.
THE FORWARD DIFFERENTIAL CROSS SECTION IS THE EXTRAPOLATED VALUE OF THE LEGENDRE POLYNOMIAL FIT.
No description provided.
The elastic differential cross section for pp scattering has been measured up to a momentum transfer of ‖ t ‖ = 3(GeV/ c ) 2 at 100 GeV/c and 200 GeV/c incident momenta. The 200 GeV/ c measurements shows a diffractive like dip at ‖ t ‖ = 1.5 GeV/ c while no such dip is seen in the 100 GeV/ c data.
No description provided.
A bubble chamber investigation of π−+p elastic scattering at 1 200 MeV (K.E.) is reported. The total and differential cross-sections are determined. By extrapolation of the angular distribution, the 0° cross-section is derived and compared with the results obtained with the help of the dispersion relations and the optical theorem. The forward peak is investigated in terms of diffraction scattering and a value for the optical radius is derived.
No description provided.
No description provided.
No description provided.
The differential cross sections for K − p and p p elastic scattering have been measured over the range of four-momentum transfer squared 0.18<− t <3.3 (GeV/ c ) 2 . The K − p data decrease smoothly as a function of − t , whereas, the p p data shows a break at − t = 0.6 (GeV/ c ) 2 followed by a fast drop to − t ≅ 1.6 (GeV/ c ) 2 where the differential cross section levels off and stays constant out to − t = 3 (GeV/ c ) 2 .
No description provided.
Forum