155 research outputs found
Physical theory of the twentieth century and contemporary philosophy
It has been shown that the criticism of Pauli as well as of Susskind and
Glogover may be avoided if the standard quantum-mechanical mathematical model
has been suitably extended. There is not more any reason for Einstein's
citicism, either, if in addition to some new results concerning Bell's
inequalities and Belifante's argument are taken into account. The ensemble
interpretation of quantum mechanics (or the hidden-variable theory) should be
preferred, which is also supported by the already published results of
experiments with three polarizers. Greater space in the text has been devoted
also to the discussion of epistemological problems and some philosophical
consequences.Comment: 12 page
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
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
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.
Proton-proton elastic scattering at the LHC energy of {\surd} = 7 TeV
Proton-proton elastic scattering has been measured by the TOTEM experiment at
the CERN Large Hadron Collider at {\surd}s = 7 TeV in dedicated runs with the
Roman Pot detectors placed as close as seven times the transverse beam size
(sbeam) 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 d t =
0.1GeV p|t|. In this letter, first results of the differential cross section
are presented covering a |t|-range from 0.36 to 2.5GeV2. The differential
cross-section in the range 0.36 < |t| < 0.47 GeV2 is described by an
exponential with a slope parameter B = (23.6{\pm}0.5stat {\pm}0.4syst)GeV-2,
followed by a significant diffractive minimum at |t| =
(0.53{\pm}0.01stat{\pm}0.01syst)GeV2. For |t|-values larger than ~ 1.5GeV2, the
cross-section exhibits a power law behaviour with an exponent of -7.8_\pm}
0.3stat{\pm}0.1syst. When compared to predictions based on the different
available models, the data show a strong discriminative power despite the small
t-range covered.Comment: 12pages, 5 figures, CERN preprin
Elastic Scattering and Total Cross-Section in p+p reactions measured by the LHC Experiment TOTEM at sqrt(s) = 7 TeV
Proton-proton elastic scattering has been measured by the TOTEM experiment at
the CERN Large Hadron Collider at TeV in special runs with the
Roman Pot detectors placed as close to the outgoing beam as seven times the
transverse beam size. The differential cross-section measurements are reported
in the |t|-range of 0.36 to 2.5 GeV^2. Extending the range of data to low t
values from 0.02 to 0.33 GeV^2,and utilizing the luminosity measurements of
CMS, the total proton-proton cross section at sqrt(s) = 7 TeV is measured to be
(98.3 +- 0.2(stat) +- 2.8(syst)) mb.Comment: Proceedings of the XLI International Symposium on Multiparticle
Dynamics. Accepted for publication in Prog. Theor. Phy
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 scattering of hadrons
Colliding high energy hadrons either produce new particles or scatter
elastically with their quantum numbers conserved and no other particles
produced. We consider the latter case here. Although inelastic processes
dominate at high energies, elastic scattering contributes considerably (18-25%)
to the total cross section. Its share first decreases and then increases at
higher energies. Small-angle scattering prevails at all energies. Some
characteristic features are seen that provide informationon the geometrical
structure of the colliding particles and the relevant dynamical mechanisms. The
steep Gaussian peak at small angles is followed by the exponential (Orear)
regime with some shoulders and dips, and then by a power-law drop.
Results from various theoretical approaches are compared with experimental
data. Phenomenological models claiming to describe this process are reviewed.
The unitarity condition predicts an exponential fall for the differential cross
section with an additional substructure to occur exactly between the low
momentum transfer diffraction cone and a power-law, hard parton scattering
regime under high momentum transfer. Data on the interference of the Coulomb
and nuclear parts of amplitudes at extremely small angles provide the value of
the real part of the forward scattering nuclear amplitude.
The real part of the elastic scattering amplitude and the contribution of
inelastic processes to the imaginary part of this amplitude (the so-called
overlap function) at nonforward transferred momenta are also discussed.
Problems related to the scaling behavior of the differential cross section are
considered. The power-law regime at highest momentum transfer is briefly
described.Comment: 72 pages, 11 Figures; modified Physics-Uspekhi 56 (2013)
- …