First determination of the parameter at TeV: probing the existence of a colourless C-odd three-gluon compound state

G. Antchev; P. Aspell; I. Atanassov; V. Avati; J. Baechler; C. Baldenegro Barrera; V. Berardi; M. Berretti; E. Bossini; U. Bottigli; M. Bozzo; R. Bruce; H. Burkhardt; F. S. Cafagna; M. G. Catanesi; M. Csanád; T. Csörgő; M. Deile; F. De Leonardis; A. D’Orazio; M. Doubek; D. Druzhkin; K. Eggert; V. Eremin; F. Ferro; A. Fiergolski; F. Garcia; H. Garcia Morales; V. Georgiev; S. Giani; L. Grzanka; J. Hammerbauer; J. Heino; P. Helander; T. Isidori; V. Ivanchenko; M. Janda; A. Karev; J. Kašpar; J. Kopal; V. Kundrát; S. Lami; G. Latino; R. Lauhakangas; R. Linhart; C. Lindsey; M. V. Lokajíček; L. Losurdo; M. Lo Vetere; F. Lucas Rodríguez; M. Macrí; M. Malawski; A. Mereghetti; N. Minafra; S. Minutoli; D. Mirarchi; T. Naaranoja; F. Nemes; H. Niewiadomski; T. Novák; E. Oliveri; F. Oljemark; M. Oriunno; K. Österberg; P. Palazzi; V. Passaro; Z. Peroutka; J. Procházka; M. Quinto; E. Radermacher; E. Radicioni; F. Ravotti; S. Redaelli; E. Robutti; C. Royon; G. Ruggiero; H. Saarikko; B. Salvachua; A. Scribano; J. Siroky; J. Smajek; W. Snoeys; R. Stefanovitch; J. Sziklai; C. Taylor; E. Tcherniaev; N. Turini; V. Vacek; G. Valentino; J. Welti; J. Wenninger; J. Williams; P. Wyszkowski; J. Zich; K. Zielinski

doi:10.1140/epjc/s10052-019-7223-4

2024 Impact factor 4.8

Particles and Fields

Open Access

Eur. Phys. J. C (2019) 79: 785
https://doi.org/10.1140/epjc/s10052-019-7223-4

Regular Article - Experimental Physics

First determination of the ${\rho }$ parameter at ${\sqrt{s} = 13}$ TeV: probing the existence of a colourless C-odd three-gluon compound state

TOTEM Collaboration

G. Antchev, P. Aspell¹⁷, I. Atanassov, V. Avati¹⁵^,17, J. Baechler¹⁷, C. Baldenegro Barrera¹⁹, V. Berardi⁸^,9, M. Berretti⁴, E. Bossini¹⁴, U. Bottigli¹⁴, M. Bozzo¹¹^,12, R. Bruce¹⁷, H. Burkhardt¹⁷, F. S. Cafagna⁸, M. G. Catanesi⁸, M. Csanád⁶, T. Csörgő⁶^,7, M. Deile¹⁷, F. De Leonardis⁸^,10, A. D’Orazio⁸^,10, M. Doubek³, D. Druzhkin¹⁷, K. Eggert¹⁸, V. Eremin, F. Ferro¹¹, A. Fiergolski¹⁷, F. Garcia⁴, H. Garcia Morales¹⁷, V. Georgiev¹, S. Giani¹⁷, L. Grzanka¹⁵, J. Hammerbauer¹, J. Heino⁴, P. Helander⁴^,5, T. Isidori¹⁹, V. Ivanchenko¹⁶, M. Janda³, A. Karev¹⁷, J. Kašpar²^,17^*, J. Kopal¹⁷, V. Kundrát², S. Lami¹³, G. Latino¹⁴, R. Lauhakangas⁴, R. Linhart¹, C. Lindsey¹⁹, M. V. Lokajíček², L. Losurdo¹⁴, M. Lo Vetere¹¹^,12, F. Lucas Rodríguez¹⁷, M. Macrí¹¹, M. Malawski¹⁵, A. Mereghetti¹⁷, N. Minafra¹⁹, S. Minutoli¹¹, D. Mirarchi¹⁷, T. Naaranoja⁴^,5, F. Nemes⁶^,17, H. Niewiadomski¹⁸, T. Novák⁷, E. Oliveri¹⁷, F. Oljemark⁴^,5, M. Oriunno, K. Österberg⁴^,5, P. Palazzi¹⁷, V. Passaro⁸^,10, Z. Peroutka¹, J. Procházka², M. Quinto⁸^,9, E. Radermacher¹⁷, E. Radicioni⁸, F. Ravotti¹⁷, S. Redaelli¹⁷, E. Robutti¹¹, C. Royon¹⁹, G. Ruggiero¹⁷, H. Saarikko⁴^,5, B. Salvachua¹⁷, A. Scribano¹³, J. Siroky¹, J. Smajek¹⁷, W. Snoeys¹⁷, R. Stefanovitch¹⁷, J. Sziklai⁶, C. Taylor¹⁸, E. Tcherniaev¹⁶, N. Turini¹⁴, V. Vacek³, G. Valentino, J. Welti⁴^,5, J. Wenninger¹⁷, J. Williams¹⁹, P. Wyszkowski¹⁵, J. Zich¹ and K. Zielinski¹⁵

¹ University of West Bohemia, Pilsen, Czech Republic
² Institute of Physics of the Academy of Sciences of the Czech Republic, Prague, Czech Republic
³ Czech Technical University, Prague, Czech Republic
⁴ Helsinki Institute of Physics, University of Helsinki, Helsinki, Finland
⁵ Department of Physics, University of Helsinki, Helsinki, Finland
⁶ Wigner Research Centre for Physics, RMKI, Budapest, Hungary
⁷ EKU KRC, Gyöngyös, Hungary
⁸ INFN Sezione di Bari, Bari, Italy
⁹ Dipartimento Interateneo di Fisica di Bari, Bari, Italy
¹⁰ Dipartimento di Ingegneria Elettrica e dell’Informazione - Politecnico di Bari, Bari, Italy
¹¹ INFN Sezione di Genova, Genoa, Italy
¹² Università degli Studi di Genova, Genoa, Italy
¹³ INFN Sezione di Pisa, Pisa, Italy
¹⁴ Università degli Studi di Siena and Gruppo Collegato INFN di Siena, Siena, Italy
¹⁵ AGH University of Science and Technology, Kraków, Poland
¹⁶ Tomsk State University, Tomsk, Russia
¹⁷ CERN, Geneva, Switzerland
¹⁸ Department of Physics, Case Western Reserve University, Cleveland, OH, USA
¹⁹ The University of Kansas, Lawrence, KS, USA

^* e-mail: jan.kaspar@cern.ch

Received: 16 January 2019
Accepted: 9 July 2019
Published online: 23 September 2019

Abstract

The TOTEM experiment at the LHC has performed the first measurement at $\sqrt{s} = 13\,\mathrm{TeV}$ of the $\rho$ parameter, the real to imaginary ratio of the nuclear elastic scattering amplitude at $$t=0$$ , obtaining the following results: $\rho = 0.09 \pm 0.01$ and $\rho = 0.10 \pm 0.01$ , depending on different physics assumptions and mathematical modelling. The unprecedented precision of the $\rho$ measurement, combined with the TOTEM total cross-section measurements in an energy range larger than $10\,\mathrm{TeV}$ (from 2.76 to $13\,\mathrm{TeV}$ ), has implied the exclusion of all the models classified and published by COMPETE. The $\rho$ results obtained by TOTEM are compatible with the predictions, from other theoretical models both in the Regge-like framework and in the QCD framework, of a crossing-odd colourless 3-gluon compound state exchange in the t-channel of the proton–proton elastic scattering. On the contrary, if shown that the crossing-odd 3-gluon compound state t-channel exchange is not of importance for the description of elastic scattering, the $\rho$ value determined by TOTEM would represent a first evidence of a slowing down of the total cross-section growth at higher energies. The very low-|t| reach allowed also to determine the absolute normalisation using the Coulomb amplitude for the first time at the LHC and obtain a new total proton–proton cross-section measurement $\sigma _{\mathrm{tot}} = (110.3 \pm 3.5)\,\mathrm{mb}$ , completely independent from the previous TOTEM determination. Combining the two TOTEM results yields $\sigma _{\mathrm{tot}} = (110.5 \pm 2.4)\,\mathrm{mb}$ .