Measurement of inelastic, single- and double-diffraction cross sections in proton--proton collisions at the LHC with ALICE

B. Abelev , C. Cheshkov (1) , B. Cheynis (1) , L. Ducroux (1) , J.-Y. Grossiord (1) , Maxime Guilbaud (1) , R. Tieulent (1) , A. Uras (1) , Y. Zoccarato (1) , Laurent Aphecetche (2) , Guillaume Batigne (2) , E. Bergognon (2) , M. Bregant (2) , H. Delagrange (2) , O. Driga (2) , B. Erazmus (2) , Magali Estienne (2) , Marie Germain (2) , A. Lardeux (2) , F. Lefèvre (2) , L. Luquin (2) , Gines Martinez Garcia (2) , A. Mas (2) , L. Massacrier (2) , A. Matyja (2) , Philippe Pillot (2) , Y. Schutz (2) , Alexandre Shabetai (2) , Diego Stocco (2) , Y.W. Baek (3) , A. Baldit (3) , V. Barret (3) , N. Bastid (3) , P. Crochet (3) , P. Dupieux (3) , R. Ichou (3) , X. Lopez (3) , F. Manso (3) , M. Marchisone (3) , S. Porteboeuf-Houssais (3) , P. Rosnet (3) , B. Vulpescu (3) , X. Zhang (3) , N. Arbor (4) , G. Conesa Balbastre (4) , J. Faivre (4) , C. Furget (4) , R. Guernane (4) , S. Kox (4) , J.S. Real (4) , C. Silvestre (4)

1 IPNL - Institut de Physique Nucléaire de Lyon
2 SUBATECH - Laboratoire SUBATECH Nantes
3 LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand
4 LPSC - Laboratoire de Physique Subatomique et de Cosmologie

Measurements of cross sections of inelastic and diffractive processes in proton--proton collisions at LHC energies were carried out with the ALICE detector. The fractions of diffractive processes in inelastic collisions were determined from a study of gaps in charged particle pseudorapidity distributions: for single diffraction (diffractive mass $M_X < 200$ GeV/$c^2$) $\sigma_{\rm SD}/\sigma_{\rm INEL} = 0.21 \pm 0.03, 0.20^{+0.07}_{-0.08}$, and $0.20^{+0.04}_{-0.07}$, respectively at centre-of-mass energies $\sqrt{s} = 0.9, 2.76$, and 7 TeV; for double diffraction (for a pseudorapidity gap $\Delta\eta > 3$) $\sigma_{\rm DD}/\sigma_{\rm INEL} = 0.11 \pm 0.03, 0.12 \pm 0.05$, and $0.12^{+0.05}_{-0.04}$, respectively at $\sqrt{s} = 0.9, 2.76$, and 7 TeV. To measure the inelastic cross section, beam properties were determined with van der Meer scans, and, using a simulation of diffraction adjusted to data, the following values were obtained: $\sigma_{\rm INEL} = 62.8^{+2.4}_{-4.0} (model) \pm 1.2 (lumi)$ mb at $\sqrt{s} =$ 2.76 TeV and $73.2^{+2.0}_{-4.6} (model) \pm 2.6 (lumi)$ mb at $\sqrt{s}$ = 7 TeV. The single- and double-diffractive cross sections were calculated combining relative rates of diffraction with inelastic cross sections. The results are compared to previous measurements at proton--antiproton and proton--proton colliders at lower energies, to measurements by other experiments at the LHC, and to theoretical models.

Domaines: Physique des Hautes Energies - Expérience [hep-ex]

B. Abelev, C. Cheshkov, B. Cheynis, L. Ducroux, J.-Y. Grossiord, et al.. Measurement of inelastic, single- and double-diffraction cross sections in proton--proton collisions at the LHC with ALICE. European Physical Journal C: Particles and Fields, 2013, 73, pp.2456. ⟨10.1140/epjc/s10052-013-2456-0⟩. ⟨in2p3-00725471⟩