Pseudorapidity (η) distributions of charged particles produced in proton-proton collisions at a centre-of-mass energy of 8 TeV are measured in the ranges |η| < 2.2 and 5.3 < |η| < 6.4 covered by the CMS and TOTEM detectors, respectively. The data correspond to an integrated luminosity of L = 45 µb −1 . 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.

We report measurements of the primary charged-particle pseudorapidity density and transverse momentum distributions in p-Pb collisions at √ s NN = 5.02 TeV and investigate their correlation with experimental observables sensitive to the centrality of the collision. Centrality classes are defined by using different event-activity estimators, i.e., charged-particle multiplicities measured in three different pseudorapidity regions as well as the energy measured at beam rapidity (zero degree). The procedures to determine the centrality, quantified by the number of participants (N part ) or the number of nucleon-nucleon binary collisions (N coll ) are described. We show that, in contrast to Pb-Pb collisions, in p-Pb collisions large multiplicity fluctuations together with the small range of participants available generate a dynamical bias in centrality classes based on particle multiplicity. We propose to use the zero-degree energy, which we expect not to introduce a dynamical bias, as an alternative event-centrality estimator. Based on zero-degree energy-centrality classes, the N part dependence of particle production is studied. Under the assumption that the multiplicity measured in the Pb-going rapidity region scales with the number of Pb participants, an approximate independence of the multiplicity per participating nucleon measured at mid-rapidity of the number of participating nucleons is observed. Furthermore, at high-p T the p-Pb spectra are found to be consistent with the pp spectra scaled by N coll for all centrality classes. Our results represent valuable input for the study of the event-activity dependence of hard probes in p-Pb collisions and, hence, help to establish baselines for the interpretation of the Pb-Pb data.

The measurement of primary , , and production at mid-rapidity ( 0.5) in proton–proton collisions at 7 TeV performed with a large ion collider experiment at the large hadron collider (LHC) is reported. Particle identification is performed using the specific ionisation energy-loss and time-of-flight information, the ring-imaging Cherenkov technique and the kink-topology identification of weak decays of charged kaons. Transverse momentum spectra are measured from 0.1 up to 3 GeV/ for pions, from 0.2 up to 6 GeV/ for kaons and from 0.3 up to 6 GeV/ for protons. The measured spectra and particle ratios are compared with quantum chromodynamics-inspired models, tuned to reproduce also the earlier measurements performed at the LHC. Furthermore, the integrated particle yields and ratios as well as the average transverse momenta are compared with results at lower collision energies.

Proton-proton elastic scattering at the LHC energy of s = 7 TeV The TOTEM Collaboration, G. Antchev, P. Aspell et al.Measurement of proton-proton elastic scattering and total cross-section at The TOTEM Collaboration, G. Antchev, P. Aspell et al.-LHC optics measurement with proton tracks detected by the Roman pots of the TOTEM experiment The TOTEM Collaboration, G Antchev, P Aspell et al. Abstract -TOTEM has measured the differential cross-section for elastic proton-proton scattering at the LHC energy of √ s = 7 TeV analysing data from a short run with dedicated large-β * optics. A single exponential fit with a slope B = (20.1 ± 0.2 stat ± 0.3 syst ) GeV −2 describes the range of the four-momentum transfer squared |t| from 0.02 to 0.33 GeV 2 . After the extrapolation to |t| = 0, a total elastic scattering cross-section of (24.8 ± 0.2 stat ± 1.2 syst ) mb was obtained. Applying the optical theorem and using the luminosity measurement from CMS, a total proton-proton cross-section of (98.3 ± 0.2 stat ± 2.8 syst ) mb was deduced which is in good agreement with the expectation from the overall fit of previously measured data over a large range of center-of-mass energies. From the total and elastic pp cross-section measurements, an inelastic pp cross-section of (73.5 ± 0.6open access editor's choice 21002-p1The TOTEM Collaboration (G. Antchev et al.) Introduction. -The observation of the rise of the total cross-section with energy was one of the highlights at the ISR, the first CERN collider [1][2][3][4]. Some indirect indications for this unforeseen phenomenon had already come earlier from high-energy cosmic-ray showers [5][6][7]. A long series of total proton-antiproton cross-section measurements followed in the last decades both at the CERN SppS collider [8,9] and at the TEVATRON [10][11][12][13].In this letter, we report the first measurement of the total and elastic proton-proton cross-sections at the CERN Large Hadron Collider (LHC) using the optical theorem together with the luminosity provided by the CMS experiment [14,15]. With a dedicated beam optics configuration (β * = 90 m) TOTEM has measured the differential crosssection of elastic scattering for four-momentum transfer squared values |t| to 2 × 10 −2 GeV 2 , making the extrapolation to the optical point at |t| = 0 possible. This allows the determination of the elastic scattering cross-section as well as the total cross-section.

-At the LHC energy of √ s = 7 TeV, 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 (≈ 5σ beam ) in a dedicated run with β * = 90 m, |t|-values down to 5 · 10 −3 GeV 2 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 GeV 2 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 crosssection 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).open access