First measurement of the total proton-proton cross-section at the LHC energy of \chem{\sqrt{s} = 7\,TeV}

Abstract

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.

Measurement of the proton-air cross section with Telescope Array’s Middle Drum detector and surface array in hybrid mode

“…The dotted curve is the QCD inspired fit of the total p-p cross section vs. the center of mass energy √ s(GeV) [7]. The result from this work at √ s = 95 +5 −8 TeV, in addition to the most recent result published by the Auger experiment at √ s = 57 TeV [2] and reported recent result by the LHC at √ s = 7 TeV [42] are all in agreement with the fit. The proton-proton cross section vs. the center of mass energy result of this work, including the statistical (outer/thinner) and systematic (inner/thicker) error bars.…”

“…Here σ inel p−air is converted to σ total p−p using the BHS fit. periments like Fly's Eye [1], Akeno [29], HiRes [32], and Auger [2], together with accelerator pp andpp cross section measurement [41], in addition to the recent result from LHC by TOTEM [42]. The dotted curve is the QCD inspired fit of the total p-p cross section vs. the center of mass energy √ s(GeV) [7].…”

Eikonal fit toppandp¯pscattering and the edge in the scattering amplitude

“…This is the same energy range with the same constraints as used in the Block-Halzen fits based on analytic amplitudes with a ln 2 s high energy behavior [2,9]. However, we include the newer data at very high energies from the Large Hadron Collider (LHC) [12][13][14][15][16] and the Auger [17] and HiRes [18] collaborations.…”

\(\langle X_{\text{max}} \rangle \) Uncertainty from Extrapolation of Cosmic Ray Air Shower Parameters

“…The cross section measured by the TOTEM [26] experiment at the LHC, at 7 TeV, has an uncertainty of ± 3%. So a range of uncertainty of ±3% in p-p becomes a range of ±4.8% in the p-air cross section yielding an uncertainty in < X max > of ±2 g/cm 2 .…”

“…[25]. The recent result from LHC is also shown by the star marker [26]. The results by cosmic ray detectors are also included [24,[27][28][29][30].…”