Publication Date:
2019-09-01
Description:
The TOTEM experiment at the LHC has performed the first measurement at $$sqrt{s} = 13,mathrm{TeV}$$s=13TeV of the $$
ho $$ρ parameter, the real to imaginary ratio of the nuclear elastic scattering amplitude at $$t=0$$t=0, obtaining the following results: $$
ho = 0.09 pm 0.01$$ρ=0.09±0.01 and $$
ho = 0.10 pm 0.01$$ρ=0.10±0.01, depending on different physics assumptions and mathematical modelling. The unprecedented precision of the $$
ho $$ρ measurement, combined with the TOTEM total cross-section measurements in an energy range larger than $$10,mathrm{TeV}$$10TeV (from 2.76 to $$13,mathrm{TeV}$$13TeV), has implied the exclusion of all the models classified and published by COMPETE. The $$
ho $$ρ 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 $$
ho $$ρ 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 $$sigma _{mathrm{tot}} = (110.3 pm 3.5),mathrm{mb}$$σtot=(110.3±3.5)mb, completely independent from the previous TOTEM determination. Combining the two TOTEM results yields $$sigma _{mathrm{tot}} = (110.5 pm 2.4),mathrm{mb}$$σtot=(110.5±2.4)mb.
Print ISSN:
1434-6044
Electronic ISSN:
1434-6052
Topics:
Physics
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