### Abstract

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 GeV^{2}, 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 σ_{t}, 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 GeV^{2} at the level of about 10 ^{-2} mb · GeV^{-2}10^{-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 GeV^{2}, 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.

Original language | English (US) |
---|---|

Pages (from-to) | 2551-2599 |

Number of pages | 49 |

Journal | International Journal of Modern Physics A |

Volume | 24 |

Issue number | 14 |

DOIs | |

State | Published - Jun 10 2009 |

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### All Science Journal Classification (ASJC) codes

- Atomic and Molecular Physics, and Optics
- Nuclear and High Energy Physics
- Astronomy and Astrophysics

### Cite this

*International Journal of Modern Physics A*,

*24*(14), 2551-2599. https://doi.org/10.1142/S0217751X09044255

}

*International Journal of Modern Physics A*, vol. 24, no. 14, pp. 2551-2599. https://doi.org/10.1142/S0217751X09044255

**Forward physics at the LHC; Elastic scattering.** / Fiore, R.; Jenkovszky, L.; Orava, R.; Predazzi, E.; Prokudin, A.; Selyugin, O.

Research output: Contribution to journal › Article

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.

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

VL - 24

SP - 2551

EP - 2599

JO - International Journal of Modern Physics A

JF - International Journal of Modern Physics A

SN - 0217-751X

IS - 14

ER -