https://doi.org/10.1140/epjc/s10052-019-7223-4
Regular Article - Experimental Physics
First determination of the 
parameter at 
TeV: probing the existence of a colourless C-odd three-gluon compound state
TOTEM Collaboration
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
The TOTEM experiment at the LHC has performed the first measurement at 
of the 
parameter, the real to imaginary ratio of the nuclear elastic scattering amplitude at 
, obtaining the following results: 
and 
, depending on different physics assumptions and mathematical modelling. The unprecedented precision of the measurement, combined with the TOTEM total cross-section measurements in an energy range larger than 
(from 2.76 to 
), has implied the exclusion of all the models classified and published by COMPETE. The 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 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 
, completely independent from the previous TOTEM determination. Combining the two TOTEM results yields 
.
© CERN for the benefit of the TOTEM collaboration, 2019
