TY - JOUR

T1 - Forward physics at the LHC; Elastic scattering

AU - Fiore, R.

AU - Jenkovszky, L.

AU - Orava, R.

AU - Predazzi, E.

AU - Prokudin, A.

AU - Selyugin, O.

N1 - Funding Information:
We thank Mario Deile, Alan Martin, Marcio Jose Menon, Francesco Pacca-noni, Vladimir Petrov, Jacques Soffer and Serguey Troshin for useful remarks. L. Jenkovszky and O. Selyugin are grateful to the Department of Theoretical Physics of the University of Torino and the Department of Physics of the University of Calabria and the Istituto Nazionale di Fisica Nucleare — Sezione di Torino and Gruppo Collegato di Cosenza, where part of this work was done, for their warm hospitality and support. R. Orava wants to express his gratitude to the Academy of Finland for support. A. Prokudin and R. Fiore acknowledge partial support by the Italian Ministry of University and Research.

PY - 2009/6/10

Y1 - 2009/6/10

N2 - The following effects in the nearly forward ("soft") region of the LHC are proposed to be investigated: • At small |t| the fine structure of the cone (Pomeron) should be scrutinized: (a) a break of the cone near t ≈ -0.1 GeV2, due to the two-pion threshold, and required by t-channel unitarity, and (b) possible small-period oscillations between t = 0 and the dip region. • In measuring the elastic pp scattering and total pp cross-section at the LHC, the experimentalists are urged to treat the total cross-section σt, the ratio ρ of real to imaginary part of the forward scattering amplitude, the forward slope B and the luminosity ${\mathcal L}$ as free parameters, and to publish model-independent results on dN/dt. • Of extreme interest are the details of the expected diffraction minimum in the differential cross-section. Its position, expected in the interval 0.4 < -t < 1 GeV2 at the level of about 10 -2 mb · GeV-210-1 mb · GeV -2, cannot be predicted unambiguously, and its depth, i.e. the ratio of dσ/dt at the minimum to that at the subsequent maximum (about -t = 5 GeV2, which is about 5) is of great importance. • The expected slow-down with increasing |t| of the shrinkage of the second cone (beyond the dip-bump), together with the transition from an exponential to a power decrease in -t, will be indicative of the transition from "soft" to "hard" physics. Explicit models are proposed to help in quantifying this transition. • In a number of papers a limiting behavior, or saturation of the black disk limit (BDL), was predicted. This controversial phenomenon shows that the BDL may not be the ultimate limit, instead a transition from shadow to antishadow scattering may by typical of the LHC energy scale.

AB - The following effects in the nearly forward ("soft") region of the LHC are proposed to be investigated: • At small |t| the fine structure of the cone (Pomeron) should be scrutinized: (a) a break of the cone near t ≈ -0.1 GeV2, due to the two-pion threshold, and required by t-channel unitarity, and (b) possible small-period oscillations between t = 0 and the dip region. • In measuring the elastic pp scattering and total pp cross-section at the LHC, the experimentalists are urged to treat the total cross-section σt, the ratio ρ of real to imaginary part of the forward scattering amplitude, the forward slope B and the luminosity ${\mathcal L}$ as free parameters, and to publish model-independent results on dN/dt. • Of extreme interest are the details of the expected diffraction minimum in the differential cross-section. Its position, expected in the interval 0.4 < -t < 1 GeV2 at the level of about 10 -2 mb · GeV-210-1 mb · GeV -2, cannot be predicted unambiguously, and its depth, i.e. the ratio of dσ/dt at the minimum to that at the subsequent maximum (about -t = 5 GeV2, which is about 5) is of great importance. • The expected slow-down with increasing |t| of the shrinkage of the second cone (beyond the dip-bump), together with the transition from an exponential to a power decrease in -t, will be indicative of the transition from "soft" to "hard" physics. Explicit models are proposed to help in quantifying this transition. • In a number of papers a limiting behavior, or saturation of the black disk limit (BDL), was predicted. This controversial phenomenon shows that the BDL may not be the ultimate limit, instead a transition from shadow to antishadow scattering may by typical of the LHC energy scale.

UR - http://www.scopus.com/inward/record.url?scp=67650242006&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=67650242006&partnerID=8YFLogxK

U2 - 10.1142/S0217751X09044255

DO - 10.1142/S0217751X09044255

M3 - Article

AN - SCOPUS:67650242006

SN - 0217-751X

VL - 24

SP - 2551

EP - 2599

JO - International Journal of Modern Physics A

JF - International Journal of Modern Physics A

IS - 14

ER -