103 research outputs found
LHC Optics Measurement with Proton Tracks Detected by the Roman Pots of the TOTEM Experiment
Precise knowledge of the beam optics at the LHC is crucial to fulfil the
physics goals of the TOTEM experiment, where the kinematics of the scattered
protons is reconstructed with the near-beam telescopes -- so-called Roman Pots
(RP). Before being detected, the protons' trajectories are influenced by the
magnetic fields of the accelerator lattice. Thus precise understanding of the
proton transport is of key importance for the experiment. A novel method of
optics evaluation is proposed which exploits kinematical distributions of
elastically scattered protons observed in the RPs. Theoretical predictions, as
well as Monte Carlo studies, show that the residual uncertainty of this optics
estimation method is smaller than 0.25 percent.Comment: 20 pages, 11 figures, 5 figures, to be submitted to New J. Phy
Double diffractive cross-section measurement in the forward region at LHC
The first double diffractive cross-section measurement in the very forward
region has been carried out by the TOTEM experiment at the LHC with
center-of-mass energy of sqrt(s)=7 TeV. By utilizing the very forward TOTEM
tracking detectors T1 and T2, which extend up to |eta|=6.5, a clean sample of
double diffractive pp events was extracted. From these events, we measured the
cross-section sigma_DD =(116 +- 25) mub for events where both diffractive
systems have 4.7 <|eta|_min < 6.5 .Comment: 5 pages, 1 figure, submitted for publicatio
Performance of the TOTEM Detectors at the LHC
The TOTEM Experiment is designed to measure the total proton-proton
cross-section with the luminosity-independent method and to study elastic and
diffractive pp 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, are installed on each side of the IP in the
pseudorapidity region 3.1 < = |eta | < = 6.5, and special movable beam-pipe
insertions - called Roman Pots (RP) - are placed at distances of +- 147 m and
+- 220 m from IP5. This article describes in detail the working of the TOTEM
detector to produce physics results in the first three years of operation and
data taking at the LHC.Comment: 40 pages, 31 figures, submitted to Int. J. Mod. Phys.
Diamond Detectors for the TOTEM Timing Upgrade
This paper describes the design and the performance of the timing detector
developed by the TOTEM Collaboration for the Roman Pots (RPs) to measure the
Time-Of-Flight (TOF) of the protons produced in central diffractive
interactions at the LHC. The measurement of the TOF of the protons allows the
determination of the longitudinal position of the proton interaction vertex and
its association with one of the vertices reconstructed by the CMS detectors.
The TOF detector is based on single crystal Chemical Vapor Deposition (scCVD)
diamond plates and is designed to measure the protons TOF with about 50 ps time
precision. This upgrade to the TOTEM apparatus will be used in the LHC run 2
and will tag the central diffractive events up to an interaction pileup of
about 1. A dedicated fast and low noise electronics for the signal
amplification has been developed. The digitization of the diamond signal is
performed by sampling the waveform. After introducing the physics studies that
will most profit from the addition of these new detectors, we discuss in detail
the optimization and the performance of the first TOF detector installed in the
LHC in November 2015.Comment: 26 pages, 18 figures, 2 tables, submitted for publication to JINS
Evidence for non-exponential elastic proton-proton differential cross-section at low |t| and sqrt(s) = 8 TeV by TOTEM
The TOTEM experiment has made a precise measurement of the elastic
proton-proton differential cross-section at the centre-of-mass energy sqrt(s) =
8 TeV based on a high-statistics data sample obtained with the beta* = 90
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 sigma. 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.Comment: Final version published in Nuclear Physics
Elastic differential cross-section at 2.76 TeV and implications on the existence of a colourless 3-gluon bound state
The proton-proton elastic differential cross section
has been measured by the TOTEM experiment at TeV energy with
m beam optics. The Roman Pots were inserted to 13 times the
transverse beam size from the beam, which allowed to measure the differential
cross-section of elastic scattering in a range of the squared four-momentum
transfer () from GeV to GeV. The differential
cross-section can be described with an exponential in the -range between
GeV and GeV, followed by a diffractive minimum (dip)
at GeV and a subsequent maximum (bump).
The ratio of the at the bump and at the dip is . When compared to the measurement of the D0 experiment at
TeV, a significant difference can be observed. Under the
condition that the effects due to the energy difference between TOTEM and D0
can be neglected, the result provides evidence for a colourless 3-gluon bound
state exchange in the -channel of the proton-proton elastic scattering.Comment: 75 authors, 17 pages, 10 figures, 3 table
Elastic differential cross-section measurement at root s=13 TeV by TOTEM
The TOTEM collaboration has measured the velastic proton-proton differential cross section d sigma/dt at root s = 13 TeV LHC energy using dedicated beta* = 90 m beam optics. The Roman Pot detectors were inserted to 10s distance from the LHC beam, which allowed the measurement of the range [0.04 GeV2; 4 GeV2] in four-momentum transfer squared vertical bar t vertical bar. The efficient data acquisition allowed to collect about 10(9) elastic events to precisely measure the differential cross-section including the diffractive minimum (dip), the subsequent maximum (bump) and the large-vertical bar t vertical bar tail. The average nuclear slope has been found to be B = (20.40 +/- 0.002(stat) +/- 0.01(syst)) GeV-2 in the vertical bar t vertical bar-range 0.04-0.2 GeV2. The dip position is vertical bar t(dip)vertical bar = (0.47 +/- 0.004(stat)+/- 0.01(syst)) GeV2. The differential cross section ratio at the bump vs. at the dip R = 1.77 +/- 0.01(stat) has been measured with high precision. The series of TOTEM elastic pp measurements show that the dip is a permanent feature of the pp differential cross-section at the TeV scale.Peer reviewe
Elastic differential cross-section dσ/dt at s√=2.76 TeV and implications on the existence of a colourless C-odd three-gluon compound state
The proton–proton elastic differential cross section dσ/dt has been measured by the TOTEM experiment at s√=2.76 TeV energy with β∗=11 m beam optics. The Roman Pots were inserted to 13 times the transverse beam size from the beam, which allowed to measure the differential cross-section of elastic scattering in a range of the squared four-momentum transfer (|t|) from 0.36 to 0.74 GeV2. The differential cross-section can be described with an exponential in the |t|-range between 0.36 and 0.54 GeV2, followed by a diffractive minimum (dip) at |tdip|=(0.61±0.03) GeV2 and a subsequent maximum (bump). The ratio of the dσ/dt at the bump and at the dip is 1.7±0.2. When compared to the proton–antiproton measurement of the D0 experiment at s√=1.96 TeV, a significant difference can be observed. Under the condition that the effects due to the energy difference between TOTEM and D0 can be neglected, the result provides evidence for the exchange of a colourless C-odd three-gluon compound state in the t-channel of the proton–proton and proton–antiproton elastic scattering
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