Proton-proton elastic scattering has been measured by the TOTEM experiment at the CERN Large Hadron Collider at √ s = 7 TeV in dedicated runs with the Roman Pot detectors placed as close as seven times the transverse beam size (σ beam ) from the outgoing beams. After careful study of the accelerator optics and the detector alignment, |t| , the square of four-momentum transferred in the elastic scattering process, has been determined with an uncertainty of δt = 0.1 GeV |t|. In this letter, first results of the differential cross section are presented covering a |t|-range from 0.36 to 2.5 GeV 2 . The differential cross-section in the range 0.36 < |t| < 0.47 GeV 2 is described by an exponential with a slope parameter B = (23.6 ± 0.5 stat ± 0.4 syst ) GeV −2 , followed by a significant diffractive minimum at |t| = (0.53 ± 0.01 stat ± 0.01 syst ) GeV 2 . For |t|-values larger than ∼ 1.5 GeV 2 , the cross-section exhibits a power law behaviour with an exponent of -7.8 ± 0.3 stat ± 0.1 syst . When compared to predictions based on the different available models, the data show a strong discriminative power despite the small t-range covered.
The TOTEM Experiment will measure the total pp cross-section with the luminosityindependent method and study elastic and diffractive scattering at the LHC. To achieve optimum forward coverage for charged particles emitted by the pp collisions in the interaction point IP5, two tracking telescopes, T1 and T2, will be installed on each side in the pseudorapidity region 3.1 ≤ |η| ≤ 6.5, and Roman Pot stations will be placed at distances of ±147 m and ±220 m from IP5. Being an independent experiment but technically integrated into CMS, TOTEM will first operate in standalone mode to pursue its own physics programme and at a later stage together with CMS for a common physics programme. This article gives a description of the TOTEM apparatus and its performance.
Abstract-Silicon detectors for the Roman Pots of the the large hadron collider TOTEM experiment aim for full sensitivity at the edge where a terminating structure is required for electrical stability. This work provides an innovative approach reducing the conventional width of the terminating structure to less than 100 m, still using standard planar fabrication technology. The objective of this new development is to decouple the electric behavior of the surface from the sensitive volume within a few tens of micrometers. The explanation of the basic principle of this new approach together with the experimental confirmation via electric measurements and beam test are presented in this paper, demonstrating that silicon detectors with this new terminating structure are fully operational and efficient to under 60 m from the die cut.
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