Pp Total Cross Section Research Articles

Unitarisation dependence of diffractive scattering in light of high-energy collider data

We study the consequences of high-energy collider data on the best fits to total, elastic, inelastic, and single-diffractive cross sections for pp and poverline{p} scattering using different unitarisation schemes. We find that the data are well fitted both by eikonal and U-matrix schemes, but that diffractive data prefer the U-matrix. Both schemes may be generalised by means of an additional parameter; however, this yields only marginal improvements to the fits. We provide estimates for ρ, the ratio of the real part to the imaginary part of the elastic amplitude, for the different fits. We comment on the effect of the different schemes on present and future cosmic ray data.

Precision RENORM / MBR Diffraction Predictions Tested by Recent LHC Results

Diffractive, elastic, and precision total pp cross-section predictions, based on the pre-LHC RENORM/MBR model, are compared to recent experimental results. Discrepancies among results by different experiments present a challenge to testing the model. Suggestions for analyses/measurements to understand and resolve the experimental discrepancies are discussed.

Measurement of the total cross section from elastic scattering in pp collisions at [formula omitted] with the ATLAS detector

In this contribution a measurement of the total pp cross section with the ATLAS detector at the LHC at s=7 TeV is presented. In a special run with high-β⋆ beam optics, the differential elastic cross section is measured as a function of the Mandelstam momentum transfer variable t. The measurement is performed with the ALFA sub-detector of ATLAS. Using a fit to the differential elastic cross section in the |t| range from 0.01 GeV2 to 0.1 GeV2 to extrapolate to |t|→0, the total cross section, σtot(pp→X), is measured via the optical theorem to be:σtot(pp→X)=95.35±0.38(stat.)±1.25(exp.)±0.37(extr.) mb, where the first error is statistical, the second accounts for all experimental systematic uncertainties and the last is related to uncertainties in the extrapolation to |t|→0. In addition, the slope of the elastic cross section at small |t| is determined to be B = 19.73 ± 0.14 (stat.) ± 0.26 (syst.) GeV-2.

Large Rapidity Gap Method to Select Soft Diffraction Dissociation at the LHC

In proton-proton (pp) collisions, any process involves exchanging the vacuum quantum numbers is known as diffractive process. A diffractive process with no largeQ2is called soft diffractive process. The diffractive processes are important for understanding nonperturbative QCD effects and they also constitute a significant fraction of the total pp cross section. The diffractive events are typically characterized by a region of the detector without particles, known as a rapidity gap. In order to observe diffractive events in this way, we consider the pseudorapidity acceptance in the forward region of the ATLAS and CMS detectors at the Large Hadron Collider (LHC) and discuss the methods to select soft diffractive dissociation for pp collisions ats=7 TeV. It is shown that, in the limited detector rapidity acceptance, it is possible to select diffractive dissociation events by requiring a rapidity gap in the event; however, without using forward detectors, it seems not possible to fully separate single and double diffractive dissociation events. The Zero Degree Calorimeters can be used to distinguish the type of the diffractive processes up to a certain extent.

Diffraction and Forward Physics in ATLAS: results and perspectives

1 I.N.F.N. Sezione di Bologna (ITALY) Abstract. The present and future potential of ATLAS for diffraction and forward physics is presented. As recent results the rapidity gap cross section and elastic and total pp cross sections are reported. The upgrade project AFP is presented and it is shown how it will complement the ALFA acceptance for diffractive physics in mea- surements taken with β ∗ =90 m LHC beam optics. Moreover, the AFP detector will guarantee good acceptance on diffractive events also during normal running conditions allowing to improve the ATLAS detector perfor- mances. If in addition, a high luminosity program will be feasible, AFP might be fundamental for potential discoveries with extra dimensions being one example.

Measurement of the total cross section from elastic scattering in pp collisions at [formula omitted] with the ATLAS detector

A measurement of the total pp cross section at the LHC at s=7 TeV is presented. In a special run with high-β⋆ beam optics, an integrated luminosity of 80 μb−1 was accumulated in order to measure the differential elastic cross section as a function of the Mandelstam momentum transfer variable t. The measurement is performed with the ALFA sub-detector of ATLAS. Using a fit to the differential elastic cross section in the |t| range from 0.01 GeV2 to 0.1 GeV2 to extrapolate to |t|→0, the total cross section, σtot(pp→X), is measured via the optical theorem to be:σtot(pp→X)=95.35±0.38(stat.)±1.25(exp.)±0.37(extr.)mb, where the first error is statistical, the second accounts for all experimental systematic uncertainties and the last is related to uncertainties in the extrapolation to |t|→0. In addition, the slope of the elastic cross section at small |t| is determined to be B=19.73±0.14(stat.)±0.26(syst.) GeV−2.

Modeling $\bar{p}p$ and recent LHC pp total cross-sections

New technique is presented for modeling total cross-section of both pp and [Formula: see text] collisions from low to ultra high energy regions using an efficient artificial neural network (ANN). We have used the input (center-of-mass energy, [Formula: see text], and type of particle P) and output (total cross-section σ tot ) data to build a prediction model by ANN. The neural network has been trained to produce a function that studies the dependence of σ tot on [Formula: see text] and P. The trained ANN model shows a good performance in matching the trained distributions, predicts cross-sections that are not presented in the training set. The general trend of the predicted values shows a good agreement with the recent Large Hadron Collider (LHC) measurements, where the total cross-section at [Formula: see text] and 8 TeV are measured to be 98.6 mb and 101.7 mb, respectively. The predicted values of the total cross-section at [Formula: see text] and 14 TeV are found to be 105.8 mb and 111.7 mb, respectively. Those predictions are in good agreement with Block, Cudell and Nakamura.

Relativistic Meson-Proton and Proton-Proton Cross- Sections and Quantum Molecular Dynamics Model

Above 104 GeV/c projectile momenta, the total cross-sections for pp and( p) ̅ p collisions as a function of laboratory beam momentum and center of mass energy, are independent. In the range, 0.1 up to 104 GeV/c the total cross-section depends on the nature of the interacting particles and on the geometrical interpretations in terms of the impact parameter. This could explain in terms of the Quantum Molecular Dynamic QMD model and its ultra relativistic approach UrQMD, in terms of the isospin of the colliding particles, their flavor, and center of mass energies. The model can give also a qualitative success for such dependencies for π^+ p and k^+ p interactions.

Modeling hadronic collisions using genetic programming approach

New technique, Genetic Programming, is presented for modeling total cross section of both pp and ¯ pp collisions from low to high energy regions. Recent total cross section data are taken from Particle Data Group and LHC collaboration. The model seems to fit the experimental data well.

Truncated QCD-Pomeron at LHC Energies

The eikonalized elastic proton-proton and proton-antiproton scattering amplitude F(s, t) as a function of the available increasing energy is constructed with the use of the suggestion of a finite sum of ladder diagrams calculated in QCD with a certain number of s-channel gluon rungs and, correspondingly, the powers of logarithms in the total cross section. Explicit expressions for the total cross section involving three and four rungs (four and five prongs) with ln3(s) and ln4(s) as the highest terms, respectively) are fitted to the all available proton-proton and proton-antiproton total cross section data. Predictions for the pp total cross section at the LHC energy are given.

Results from TOTEM

The TOTEM experiment at the CERN LHC is focussed on the measurement of the elastic proton-proton scattering, the total pp cross-section, and all kinds of di ffractive phenomena. Detectors housed in Roman Pots which can be moved close to the out- going proton beams allow to trigger on elastic and diffractive protons and to determine their parameters like the momentum loss and the transverse momentum transfer. In ad- dition, charged particle detectors in the forward regions detect almost all inelastic events. Together with the CMS detector, a large solid angle is covered enabling precise studies of Min. Bias as well as Single Diffractive and Double Pomeron Interactions. The results will considerably help the interpretation of the Cosmic Ray Showers at highest energies and will give insight into the proton structure and the QCD theory of strong interactions. TOTEM measured the elastic pp- scattering over a large range of t (the squared momen- tum transfer) from 10 −3 - 4 GeV 2 . None of the considered models could yield a satisfac- tory fit over the complete range. However, the exponential slope at low |t|-values and the position of the diffractive minimum are well within the extrapolation from lower energies. The total pp cross-section has been determined in different ways from the extrapolation of the elastic scattering to t=0 (optical point) and the inelastic rate: (i) From the elastic scattering using the optical theorem and the CMS, (ii) luminosity independently, using the inelastic rate, elastic scattering and the optical theorem, (iii) � independently, by using elastic scattering, inelastic rate and the CMS luminosity. The results for the total cross- section obtained from the different methods are in excellent agreement with each other. First studies of the data on diffractive phenomena have been performed by correlating the momentum loss of the forward protons with the topology of the particle flux. The data look very promising and further studies will follow. Since the conference, data have also been taken with specialized optics to reach even lower |t|-values. A determination of the � value is now in reach. The TOTEM results and the ways how they have been obtained are described in the publications (1-8) listed below.

Measurement of proton-proton elastic scattering and total cross-section at

At the LHC energy of , under various beam and background conditions, luminosities, and Roman Pot positions, TOTEM has measured the differential cross-section for proton-proton elastic scattering as a function of the four-momentum transfer squared t. The results of the different analyses are in excellent agreement demonstrating no sizeable dependence on the beam conditions. Due to the very close approach of the Roman Pot detectors to the beam center (≈5σbeam) in a dedicated run with β* = 90 m, |t|-values down to 5·10−3 GeV2 were reached. The exponential slope of the differential elastic cross-section in this newly explored |t|-region remained unchanged and thus an exponential fit with only one constant B = (19.9 ± 0.3) GeV−2 over the large |t|-range from 0.005 to 0.2 GeV2 describes the differential distribution well. The high precision of the measurement and the large fit range lead to an error on the slope parameter B which is remarkably small compared to previous experiments. It allows a precise extrapolation over the non-visible cross-section (only 9%) to t = 0. With the luminosity from CMS, the elastic cross-section was determined to be (25.4 ± 1.1) mb, and using in addition the optical theorem, the total pp cross-section was derived to be (98.6 ± 2.2) mb. For model comparisons the t-distributions are tabulated including the large |t|-range of the previous measurement (TOTEM Collaboration (Antchev G. et al), EPL, 95 (2011) 41001).

Summary of Physics Results from the TOTEM Experiment

The TOTEM experiment has performed several measurements related to its physics program in dedicated (high β*, low ℒ) LHC fills at √s = 7 TeV. Under various beam and background conditions, the differential elastic (as a function of |t|), elastic, inelastic and total pp cross-sections have been measured. A measurement of the forward charged particle η density has also been performed. A summary of these measurements is here reported, as well as the first results from runs at the LHC energy of √s = 8 TeV.

New Results from the CMS experiment

We'll present recent results from the CMS experiment on measureme nts, such as the total inelastic pp cross section, diffractive phenomena, leading particle spectra and energy flow in the forward region, measurements relevant for tuning o f Monte Carlo programs used for cosmic rays studies. We'll also give a brief overv iew of the searches for new physics and the recent results on the discovery of a higgs-like p article with a mass of 125 GeV.

Kaon pair production in proton-proton collisions at COSY-ANKE

The near-threshold production of kaon-pairs has been investigated in proton-proton collisions at Cooler Synchrotron (COSY)at Forschungszentrum Jülich. In the pp → ppK+K− reaction, the invariant mass distributions of K−p, K−pp, and K+K− indicate the presence of both K−p and K+K− final state interactions. Total cross sections for pp → ppϕ reaction have been determined at excess energies ε of 18.5, 34.5, and 76 MeV. The differential spectra at an excess energy of 18.5 MeV exhibit a clear s-wave dominance, while the high statics data at an excess energy of 76 MeV shows that higher partial waves represent the majority of the pp → ppϕ total cross section, whose energy dependence would then seem to require some s-wave ϕp enhancement near threshold.

The Recent Absolute Total np and pp Cross Section Determinations: Quality of Data Description and Prediction of Experimental Observables

The absolute total cross sections for np and pp scattering below 1000 MeV are determined based on partial-wave analyses (PWAs) of nucleon-nucleon scattering data. These cross sections are compared with the most recent ENDF/B-VII.0 and JENDL-3.3 data files, and the Nijmegen PWA. Systematic deviations from the ENDF/B-VII.0 and JENDL-3.3 evaluations are found to exist in the low-energy region. Comparison of the np evaluation with the result of most recent np total and differential cross section measurements will be discussed. Results of those measurements were not used in the evaluation database. A comparison was done to check a quality of evaluation and its capabilities to predict experimental observables. Excellent agreement was found between the new experimental data and our PWA predictions.

Searches for the technicolor signatures via gg → W±πt∓ at the Large Hadron Collider

In this paper, we calculate the production of a charged top pion in association with a W boson via gg fusion at CERN's Large Hadron Collider in the context of the topcolor assisted technicolor model. We find that the total cross section of pp → gg → W±πt∓ is several dozen femtobarns with reasonable values of the parameters, and the total cross section of pp → W±πt∓ can reach a few hundred femtobarns when we consider the sum of the contributions of these two parton subprocesses, gg → W±πt∓ and bb̄ → W±πt∓.

Development of radiation hard edgeless detectors with current terminating structure on p-type silicon

Abstract The development of edgeless Si detectors was stimulated by the tasks of the total pp cross-section study in the TOTEM experiment at the Large Hadron Collider at CERN. For this, the dead region at the detector diced side should be reduced below 50 μm. This requirement is successfully realized in edgeless Si detectors with current terminating structure (CTS), which are now operating at LHC. The development of the experiment and future LHC upgrade need the elaboration of radiation hard version of edgeless Si detectors. The current investigation represents an extension in understanding on edgeless detectors operation and development of a new issue – edgeless detectors with CTS on p-type Si.

Forward physics at the LHC: detecting elastic pp scattering by radiative photons

Photon bremsstrahlung is proposed to be used to identify elastic proton-proton interactions at the LHC. In addition to a measurement of the elastic pp cross section (assuming that the elastic slope is known), the bremsstrahlung photons will allow the evaluation of the total pp cross section, luminosity and to align the Zero Degree Calorimeters (ZDCs).

The measurement of the [formula omitted] reaction near threshold

It is shown that a recent extraction of the total cross section for pp→K+nΣ+ from inclusive K+ production data by the HIRES Collaboration [Phys. Lett. B 692 (2010) 10] is in conflict with experimental data on the exclusive pp→K+pΛ reaction. The HIRES result may be interpreted as an upper bound, which is not inconsistent with the much lower values that already exist in the literature.