In a 35 000-picture exposure of the 30-in. hydrogen bubble chamber to a 300-GeV/c proton beam at the Fermi National Accelerator Laboratory, 10054 interactions have been observed. The measured total cross section is $40.68 \pm 0.55$ mb, the elastic cross section is $7.89 \pm 0.52$ mb, and the average charged-particle multiplicity for inelastic events is $8.S0 \pm 0.12$.
From 2728 events of 205-GeV pp interactions found in 15 000 pictures taken with the 30-in. hydrogen bubble chamber at the National Accelerator Laboratory, a total cross section of 39.5±1.1 mb was measured. The mean charged-particle multiplicity for inelastic pp collisions was measured to be 7.65±0.17. The prong distribution from 2 to 22 prongs is broader than a Poisson distribution and has a width parameter f2−=〈n−(n−−1)〉−〈n−〉2=0.95±0.21.
The pseudorapidity distributions of dijets as a function of their average transverse momentum ($p_\mathrm{T}^\text{ave}$) are measured in proton-lead (pPb) and proton-proton (pp) collisions. The data samples were collected by the CMS experiment at the CERN LHC, at a nucleon-nucleon center-of-mass energy of 5.02 TeV. A significant modification of the pPb spectra with respect to the pp spectra is observed in all $p_\mathrm{T}^\text{ave}$ intervals investigated. The ratios of the pPb and pp distributions are compared to next-to-leading order perturbative quantum chromodynamics calculations with unbound nucleon and nuclear parton distribution functions (PDFs). These results give the first evidence that the gluon PDF at large Bjorken $x$ in lead ions is strongly suppressed with respect to the PDF in unbound nucleons.
An experiment using the Fermilab Single Arm Spectrometer (SAS) facility and an associated nonmagnetic vertex detector studied the reactions a+p→c+X, where a and c were π±, K±, p, or p¯. Extensive measurements were made at 100 and 175 GeV/c beam momenta with the outgoing hadrons detected in the SAS covering a kinematic range 0.12<x<1.0 and pT<1.25 GeV/c. Additional data covering a more restricted range in x were also gathered at 70 GeV/c incident momentum. In this high-statistics experiment, the identification of both the incoming and outgoing charged hadrons were made with a total of eight Čerenkov counters. New and extensive single-particle inclusive data for charged-particle production in low-pT hadronic fragmentation are presented. The average associated charged-particle multiplicity and pseudorapidity distributions are also given.
Pseudorapidity (eta) distributions of charged particles produced in proton-proton collisions at a centre-of-mass energy of 8 TeV are measured in the ranges abs(eta) < 2.2 and 5.3 < abs(eta) < 6.4 covered by the CMS and TOTEM detectors, respectively. The data correspond to an integrated luminosity of 45 inverse microbarns. Measurements are presented for three event categories. The most inclusive category is sensitive to 91-96% of the total inelastic proton-proton cross section. The other two categories are disjoint subsets of the inclusive sample that are either enhanced or depleted in single diffractive dissociation events. The data are compared to models used to describe high-energy hadronic interactions. None of the models considered provide a consistent description of the measured distributions.
The average total energy as well as its hadronic and electromagnetic components are measured with the CMS detector at pseudorapidities $-$6.6 $<\eta<-$5.2 in proton-proton collisions at a centre-of-mass energy $\sqrt{s}=$ 13 TeV. The results are presented as a function of the charged particle multiplicity in the region $|\eta|< $2. This measurement is sensitive to correlations induced by the underlying event structure over a very wide pseudorapidity region. The predictions of Monte Carlo event generators commonly used in collider experiments and ultra-high energy cosmic ray physics are compared to the data.
The highest-energy measurement of ΔσL(pp) and the first ever measurement of ΔσL(p¯p), the differences between proton-proton and antiproton-proton total cross sections for pure longitudinal spin states, are described. Data were taken using 200-GeV/c polarized beams incident on a polarized-proton target. The results are measured to be ΔσL(pp)=−42±48(stat)±53(syst) μb and ΔσL(p¯p)=−256±124(stat)±109(syst) μb. Many tests of systematic effects were investigated and are described, and a comparison to theoretical predictions is also given. Measurements of parity nonconservation at 200 GeV/c in proton scattering and the first ever of antiproton scattering have also been derived from these data. The values are consistent with zero at the 10−5 level.
The differential cross section for inclusive particle production as a function of energy in proton-proton collisions at a center-of-mass energy of 13 TeV is measured in the very forward region of the CMS detector. The measurement is based on data collected with the CMS apparatus at the LHC, and corresponds to an integrated luminosity of 0.35 inverse microbarns. The energy is measured in the CASTOR calorimeter, which covers the pseudorapidity region -6.6 < eta < -5.2. The results are given as a function of the total energy deposited in CASTOR, as well as of its electromagnetic and hadronic components. The spectra are sensitive to the modeling of multiparton interactions in pp collisions, and provide new constraints for hadronic interaction models used in collider and in high energy cosmic ray physics.
A measurement of the inelastic proton-proton cross section with the CMS detector at a center-of-mass energy of $\sqrt{s} =$ 13 TeV is presented. The analysis is based on events with energy deposits in the forward calorimeters, which cover pseudorapidities of -6.6 $< \eta $ 4.1 GeV and/or $M_\mathrm{Y} >$ 13 GeV, where $M_\mathrm{X}$ and $M_\mathrm{Y}$ are the masses of the diffractive dissociation systems at negative and positive pseudorapidities, respectively. The results are compared with those from other experiments as well as to predictions from high-energy hadron-hadron interaction models.
A measurement is presented of the inelastic proton-proton cross section at a centre-of-mass energy of sqrt(s) = 7 TeV. Using the CMS detector at the LHC, the inelastic cross section is measured through two independent methods based on information from (i) forward calorimetry (for pseudorapidity 3 < abs(eta) < 5), in collisions where at least one proton loses more than 5E-6 of its longitudinal momentum, and (ii) the central tracker (abs(eta) < 2.4), in collisions containing an interaction vertex with more than 1, 2, or 3 tracks with transverse momenta pT > 200 MeV. The measurements cover a large fraction of the inelastic cross section for particle production over about 9 units of pseudorapidity and down to small transverse momenta. The results are compared with those of other experiments, and with models used to describe high-energy hadronic interactions.
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