Measurement of the proton-antiproton total cross section at the SppS collider by a luminosity dependent method

The proton-antiproton total cross section was measured at the center-of-mass energy of s = 541GeV at the SppS at CERN using a luminosity dependent method. The result \u3c3tot=63.0\ub12.1 mb is in agreement with the luminosity independent measurement performed earlier by the UA4 Collaboration

The UA4/2 experiment at the CERN SppS collider

The UA4/2 experiment performed at CERN to measure the ratio of the real to the imaginary part of the forward elastic scattering amplitude is described. The accent is placed on the improvements with respect to the previous UA4 experiment, especially on the much improved design of the high-\u3b2 insertion and a high-resolution, highly multiplexed scintillating fiber tracking detector

Performance of almost edgeless silicon detectors in CTS and 3D-planar technologies

The physics programme of the TOTEM experiment requires the detection of very forward protons scattered by only a few microradians out of the LHC beams. For this purpose, stacks of planar Silicon detectors have been mounted in moveable near-beam telescopes (Roman Pots) located along the beamline on both sides of the interaction point. In order to maximise the proton acceptance close to the beams, the dead space at the detector edge had to be minimised. During the detector prototyping phase, different sensor technologies and designs have been explored. A reduction of the dead space to less than 50 \u3bcm has been accomplished with two novel silicon detector technologies: one with the Current Terminating Structure (CTS) design and one based on the 3D edge manufacturing. This paper describes performance studies on prototypes of these detectors, carried out in 2004 in a fixed-target muon beam at CERN's SPS accelerator. In particular, the efficiency and accuracy in the vicinity of the beam-facing edges are discussed

Measurement of the forward charged particle pseudorapidity density in pp collisions at root s=8 TeV using a displaced interaction point

The pseudorapidity density of charged particles dN(ch)/d(eta) is measured by the TOTEM experiment in proton-proton collisions at root s = 8 TeV within the range 3.9 < eta < 4.7 and -6.95 < eta < -6.9. Data were collected in a low intensity LHC run with collisions occurring at a distance of 11.25 m from the nominal interaction point. The data sample is expected to include 96-97 % of the inelastic proton-proton interactions. The measurement reported here considers charged particles with p(T) > 0 MeV/c, produced in inelastic interactions with at least one charged particle in -7 < eta < -6 or 3.7 < eta < 4.8. The dN(ch)/d eta has been found to decrease with vertical bar eta vertical bar, from 5.11 +/- 0.73 at eta = 3.95 to 1.81 +/- 0.56 at eta = -6.925. Several Monte Carlo generators are compared to the data and are found to be within the systematic uncertainty of the measurement

Luminosity-independent measurements of total, elastic and inelastic cross-sections at 1as = 7 TeV

The TOTEM experiment at the LHC has performed the first luminosity-independent determination of the total proton-proton cross-section at 1a s = 7TeV. This technique is based on the optical theorem and requires simultaneous measurements of the inelastic rate accomplished with the forward charged-particle telescopes T1 and T2 in the range 3.1 < |\u3b7| < 6.5 and of the elastic rate by detecting the outcoming protons with Roman Pot detectors. The data presented here were collected in a dedicated run in 2011 with special beam optics (\u3b2* = 90m) and Roman Pots approaching the beam close enough to register elastic events with squared four-momentum transfers |t| as low as 5 \ub7 10-3 GeV2. The luminosity-independent results for the elastic, inelastic and total cross-sections are \u3c3 el = (25.1 \ub11.1)mb, \u3c3inel = (72.9 \ub11.5)mb and \u3c3tot = (98.0 \ub12.5)mb, respectively. At the same time this method yields the integrated luminosity, in agreement with measurements by CMS. TOTEM has also determined the total cross-section in two complementary ways, both using the CMS luminosity measurement as an input. The first method sums the elastic and inelastic cross-sections and thus does not depend on the \u3c1 parameter. The second applies the optical theorem to the elastic-scattering measurements only and therefore is free of the T1 and T2 measurement uncertainties. The methods, having very different systematic dependences, give results in excellent agreement. Moreover, the \u3c1 -independent measurement makes a first estimate for the \u3c1 parameter at 1a s = 7TeV possible: |\u3c1| = 0.145 \ub10.091

Luminosity-independent measurement of the proton-proton total cross section at 1as=8 TeV

The TOTEM collaboration has measured the proton-proton total cross section at 1as=8 TeV using a luminosity-independent method. In LHC fills with dedicated beam optics, the Roman pots have been inserted very close to the beam allowing the detection of 3c90% of the nuclear elastic scattering events. Simultaneously the inelastic scattering rate has been measured by the T1 and T2 telescopes. By applying the optical theorem, the total proton-proton cross section of (101.7\ub12.9) mb has been determined, well in agreement with the extrapolation from lower energies. This method also allows one to derive the luminosity-independent elastic and inelastic cross sections: \u3c3el=(27.1\ub11.4) mb; \u3c3inel=(74. 7\ub11.7) mb

Measurement of proton-proton elastic scattering and total cross-section at 1as = 7 TeV

At the LHC energy of 1as = 7TeV, under various beam and background conditions, luminosities, and Roman Pot positions, TOTEM has measured the differential cross-section for proton-proton elastic scattering as a function of the four-momentum transfer squared t. The results of the different analyses are in excellent agreement demonstrating no sizeable dependence on the beam conditions. Due to the very close approach of the Roman Pot detectors to the beam enter ( 485\u3c3beam) in a dedicated run with \u3b2*= 90m, |t|-values down to 5\ub710-3 GeV-2 were reached. The exponential slope of the differential elastic cross-section in this newly explored |t|-region remained unchanged and thus an exponential fit with only one constant B = (19.9\ub10.3) GeV-2 over the large |t|-range from 0.005 to 0.2GeV2 describes the differential distribution well. The high precision of the measurement and the large fit range lead to an error on the slope parameter B which is remarkably small compared to previous experiments. It allows a precise extrapolation over the non-visible cross-section (only 9%) to t = 0. With the luminosity from CMS, the elastic crosssection was determined to be (25.4\ub11.1)mb, and using in addition the optical theorem, the total pp cross-section was derived to be (98.6\ub12.2)mb. For model comparisons the t-distributions are tabulated including the large |t|-range of the previous measurement (TOTEM Collaboration (Antchev G. et al.), EPL, 95 (2011) 41001)