Status of the TOTEM experiment at LHC

The TOTEM experiment is dedicated to the measurement of the total proton-proton cross-section with the luminosity-independent method and the study of elastic and diffractive scattering processes. Two tracking telescopes, T1 and T2, integrated in the CMS detector, cover the pseudo-rapidity region between 3.1 and 6.5 on both sides of the interaction point IPS. The Roman Pot (RP) stations are located at distances of +/- 147 m and +/- 220 m with respect to the interaction point to measure the very forward scattered protons at very small angles. During the LHC technical stop in winter 201012011, the TOTEM experiment was completed with the installation of the T1 telescope and the RP stations at +/- 147 m. In 2011, the LHC machine provided special optics with the large beta* = 90 m, allowing TOTEM to measure the elastic scattering differential cross-section, down to the four-momentum transfer squared vertical bar t vertical bar = 2 x 10(-2) GeV2. Using the optical theorem and extrapolation of the differential cross-section to t=0 (optical point), the total p-p cross-section at the LHC energy of root s = 7 TeV could be computed for the first time. Furthermore we measured with standard LHC beam optics and the energy of root s = 7 TeV the forward charged particle pseudorapidity density dn/d eta in the range of 5.3 < vertical bar eta vertical bar < 6.4. The status of the experiment, the performance of the detectors with emphasis on the RPs are described and the first physics results are presented. (C) 2012 Elsevier B.V. All rights reserved.