J. Procházka

First measurement of the total proton-proton cross-section at the LHC energy of \chem{\sqrt{s} = 7\,TeV}

TOTEM has measured the differential cross-section for elastic proton-proton scattering at the LHC energy of analysing data from a short run with dedicated large-β* optics. A single exponential fit with a slope B=(20.1±0.2stat±0.3syst)u2009GeV−2 describes the range of the four-momentum transfer squared |t| from 0.02 to 0.33u2009GeV2. After the extrapolation to |t|=0, a total elastic scattering cross-section of (24.8±0.2stat±1.2syst)u2009mb was obtained. Applying the optical theorem and using the luminosity measurement from CMS, a total proton-proton cross-section of (98.3±0.2stat±2.8syst)u2009mb was deduced which is in good agreement with the expectation from the overall fit of previously measured data over a large range of center-of-mass energies. From the total and elastic pp cross-section measurements, an inelastic pp cross-section of was inferred.

Measurement of proton-proton elastic scattering and total cross-section at \chem{\sqrt {s} = 7\,TeV}

At the LHC energy of , 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 center (?5?beam) in a dedicated run with ?*?=?90?m, |t|-values down to 5?10?3?GeV2 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???0.3)?GeV?2 over the large |t|-range from 0.005 to 0.2?GeV2 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 cross-section was determined to be (25.4???1.1)?mb, and using in addition the optical theorem, the total pp cross-section was derived to be (98.6???2.2)?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).

Proton-proton elastic scattering at the LHC energy of \chem{\sqrt{s} = 7\,TeV}

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 (σbeam) 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 p |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 )G eV −2 , followed by a significant diffractive minimum at |t| =( 0.53 ± 0.01 stat ± 0.01 syst )G eV 2 .F or|t|-values larger than ∼ 1. 5G eV 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. open access Copyright c EPLA, 2011

Luminosity-independent measurements of total, elastic and inelastic cross-sections at \chem{\sqrt {s} = 7\,TeV}

The TOTEM experiment at the LHC has performed the first luminosity-independent determination of the total proton-proton cross-section at . 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 3.1xa0<xa0|η|xa0<xa06.5 – 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 (β*xa0=xa090xa0m) and Roman Pots approaching the beam close enough to register elastic events with squared four-momentum transfers |t| as low as 5·10−3xa0GeV2. The luminosity-independent results for the elastic, inelastic and total cross-sections are σelxa0=xa0(25.1xa0±xa01.1)xa0mb, σinelxa0=xa0(72.9xa0±xa01.5)xa0mb and σtotxa0=xa0(98.0xa0±xa02.5)xa0mb, 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 ρ 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 ρ-independent measurement makes a first estimate for the ρ parameter at possible: |ρ|xa0=xa00.145xa0±xa00.091.

Evidence for non-exponential elastic proton-proton differential cross-section at low |t| and √ s = 8 TeV by TOTEM

Abstract The TOTEM experiment has made a precise measurement of the elastic proton–proton differential cross-section at the centre-of-mass energy s = 8 TeV based on a high-statistics data sample obtained with the β ⁎ = 90 m optics. Both the statistical and systematic uncertainties remain below 1%, except for the t-independent contribution from the overall normalisation. This unprecedented precision allows to exclude a purely exponential differential cross-section in the range of four-momentum transfer squared 0.027 | t | 0.2 GeV 2 with a significance greater than 7 σ . Two extended parametrisations, with quadratic and cubic polynomials in the exponent, are shown to be well compatible with the data. Using them for the differential cross-section extrapolation to t = 0 , and further applying the optical theorem, yields total cross-section estimates of ( 101.5 ± 2.1 ) mb and ( 101.9 ± 2.1 ) mb , respectively, in agreement with previous TOTEM measurements.

Measurement of the forward charged-particle pseudorapidity density in pp collisions at ?s = 7?TeV with the TOTEM experiment

The TOTEM experiment has measured the charged-particle pseudorapidity density dNch/d? in pp collisions at for 5.3<|?|<6.4 in events with at least one charged particle with transverse momentum above 40?MeV/c in this pseudorapidity range. This extends the analogous measurement performed by the other LHC experiments to the previously unexplored forward ? region. The measurement refers to more than 99% of non-diffractive processes and to single and double diffractive processes with diffractive masses above ~3.4?GeV/c2, corresponding to about 95% of the total inelastic cross-section. The dNch/d? has been found to decrease with |?|, from 3.84 ? 0.01(stat) ? 0.37(syst) at |?|=5.375 to 2.38?0.01(stat)?0.21(syst) at |?|=6.375. Several MC generators have been compared to data; none of them has been found to fully describe the measurement.

Measurement of elastic pp scattering at

The TOTEM experiment at the CERN LHC has measured elastic proton–proton scattering at the centre-of-mass energy

TeV in the Coulomb–nuclear interference region: determination of the

sqrt{s}=8,