The TOTEM experiment at the LHC has performed the first luminosity-independent determination of the total proton-proton cross-section at root s = 7 TeV. This technique is based on the optical theorem and requires simultaneous measurements of the inelastic rate - accomplished with the forward charged-particle telescopes T1 and T2 in the range 3.1 < vertical bar eta vertical bar < 6.5 - and of the elastic rate by detecting the outcoming protons with Roman Pot detectors. The data presented here were collected in a dedicated run in 2011 with special beam optics (beta* = 90m) and Roman Pots approaching the beam close enough to register elastic events with squared four-momentum transfers vertical bar t vertical bar as low as 5 . 10(-3) GeV2. The luminosity-independent results for the elastic, inelastic and total cross-sections are sigma(el) = (25.1 +/- 1.1) mb, sigma(inel) = (72.9 +/- 1.5) mb and sigma(tot) = (98.0 +/- 2.5) mb, respectively. At the same time this method yields the integrated luminosity, in agreement with measurements by CMS. TOTEM has also determined the total cross-section in two complementary ways, both using the CMS luminosity measurement as an input. The first method sums the elastic and inelastic cross-sections and thus does not depend on the rho parameter. The second applies the optical theorem to the elastic-scattering measurements only and therefore is free of the T1 and T2 measurement uncertainties. The methods, having very different systematic dependences, give results in excellent agreement. Moreover, the rho-independent measurement makes a first estimate for the rho parameter at root s = 7 TeV possible: vertical bar rho vertical bar = 0.145 +/- 0.091.
|Autori interni:||BERARDI, Vincenzo|
|Titolo:||Luminosity-independent measurements of total, elastic and inelastic cross-sections at root s=7 TeV|
|Data di pubblicazione:||2013|
|Digital Object Identifier (DOI):||10.1209/0295-5075/101/21004|
|Appare nelle tipologie:||1.1 Articolo in rivista|