CERN Accelerating science

Article
Report number	TOTEM-2012-004 ; CERN-PH-EP-2012-353
Title	Luminosity-independent measurements of total, elastic and inelastic cross-sections at $\sqrt{s}$ = 7 TeV
Author(s)	Antchev, G (Sofiya, Inst. Nucl. Res.) ; Aspell, P. (CERN) ; Atanassov, I. (CERN ; Sofiya, Inst. Nucl. Res.) ; Avati, V. (CERN) ; Baechler, J. (CERN) ; Berardi, V. (INFN, Bari ; Bari U.) ; Berretti, M. (INFN, Siena ; Siena U.) ; Bossini, E. (INFN, Siena ; Siena U.) ; Bozzo, M. (INFN, Genoa ; Genoa U.) ; Brogi, P. (INFN, Siena ; Siena U.) ; Brücken, E. (Helsinki Inst. of Phys. ; Helsinki U.) ; Buzzo, A. (INFN, Genoa) ; Cafagna, F.S. (INFN, Bari) ; Calicchio, M. (Bari U. ; INFN, Bari) ; Catanesi, M.G. (INFN, Bari) ; Covault, C. (Case Western Reserve U.) ; Csanad, M. (Budapest, RMKI ; Eotvos U., Dept. Atomic Phys.) ; Csörgö, T. (Budapest, RMKI) ; Deile, M. (CERN) ; Doubek, M. (CTU, Prague) ; Eggert, K. (Case Western Reserve U.) ; Eremin, V. (Ioffe Phys. Tech. Inst.) ; Ferretti, R. (INFN, Genoa ; Genoa U.) ; Ferro, F. (INFN, Genoa) ; Fiergolski, A. (Warsaw U. of Tech.) ; Garcia, F. (Helsinki Inst. of Phys.) ; Giani, S. (CERN) ; Greco, V. (INFN, Siena ; Siena U. ; CERN) ; Grzanka, L. (CERN ; Cracow, INP) ; Heino, J. (Helsinki Inst. of Phys.) ; Hilden, T. (Helsinki Inst. of Phys. ; Helsinki U.) ; Intonti, R.A. (INFN, Bari) ; Kaspar, J. (Prague, Inst. Phys. ; CERN) ; Kopal, J. (Prague, Inst. Phys. ; CERN) ; Kundrat, V. (Prague, Inst. Phys.) ; Kurvinen, K. (Helsinki Inst. of Phys.) ; Lami, S. (INFN, Pisa) ; Latino, G. (INFN, Siena ; Siena U.) ; Lauhakangas, R. (Helsinki Inst. of Phys.) ; Leszko, T. (Warsaw U. of Tech.) ; Lippmaa, E. (NICPB, Tallinn) ; Lokajicek, M. (Prague, Inst. Phys.) ; Lo Vetere, M. (INFN, Genoa ; Genoa U.) ; Lucas Rodriguez, F. (CERN) ; Macri, M. (INFN, Genoa) ; Mäki, T. (Helsinki Inst. of Phys.) ; Mercadante, A. (INFN, Bari ; Bari U.) ; Minafra, N. (CERN) ; Minutoli, S. (INFN, Genoa) ; Nemes, F. (Budapest, RMKI ; Eotvos U., Dept. Atomic Phys.) ; Niewiadomski, H. (CERN) ; Oliveri, E. (INFN, Siena ; Siena U.) ; Oljemark, F. (Helsinki Inst. of Phys. ; Helsinki U.) ; Orava, R. (Helsinki Inst. of Phys. ; Helsinki U.) ; Oriunno, M. (CERN ; SLAC) ; Österberg, K. (Helsinki Inst. of Phys. ; Helsinki U.) ; Palazzi, P. (INFN, Siena ; Siena U.) ; Prochazka, J. (Prague, Inst. Phys.) ; Quinto, M. (INFN, Bari) ; Radermacher, E. (CERN) ; Radicioni, E. (INFN, Bari) ; Ravotti, F. (CERN) ; Robutti, E. (INFN, Genoa) ; Ropelewski, L. (CERN) ; Ruggiero, G. (CERN) ; Saarikko, H. (Helsinki Inst. of Phys. ; Helsinki U.) ; Santroni, A. (INFN, Genoa ; Genoa U.) ; Scribano, A. (INFN, Siena ; Siena U.) ; Smajek, J. (CERN) ; Snoeys, W. (CERN) ; Sziklai, J. (Budapest, RMKI) ; Taylor, C. (Case Western Reserve U.) ; Turini, N. (INFN, Siena ; Siena U.) ; Vacek, V. (CTU, Prague) ; Vitek, M. (CTU, Prague) ; Welti, J. (Helsinki Inst. of Phys. ; Helsinki U.) ; Whitmore, J. (Penn State U.) ; Wyszkowski, P. (CERN ; AGH-UST, Cracow)
Publication	2013
Imprint	2013
Number of pages	7
In:	EPL 101 (2013) 21004
DOI	10.1209/0295-5075/101/21004
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; TOTEM
Free keywords	forward physics ; minimum bias ; experimental results ; LHC ; Total Cross Section ; Forward physics
Abstract	The TOTEM experiment at the LHC has performed the first luminosity-independent determination of the total proton-proton cross-section at $\sqrt {s} = 7\,{\mathrm { TeV}}$ . 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 < |η| < 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 (β* = 90 m) and Roman Pots approaching the beam close enough to register elastic events with squared four-momentum transfers |t| as low as 5·10(−)(3) GeV(2). The luminosity-independent results for the elastic, inelastic and total cross-sections are σ(el) = (25.1 ± 1.1) mb, σ(inel) = (72.9 ± 1.5) mb and σ(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 ρ 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 ρ-independent measurement makes a first estimate for the ρ parameter at $\sqrt {s} = 7\,{\mathrm { TeV}}$ possible: |ρ| = 0.145 ± 0.091.
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