583 research outputs found
Evidence for non-exponential elastic proton proton differential cross-section at low vertical bar t vertical bar and √ 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 root s = 8 TeV based on a high-statistics data sample obtained with the beta* = 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 <vertical bar t vertical bar <0.2 GeV2 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. (C) 2015 The Authors. Published by Elsevier B.V.Peer reviewe
First measurement of elastic, inelastic and total cross-section at √s = 13TeV by TOTEM and overview of cross-section data at LHC energies : TOTEM Collaboration
The TOTEM collaboration has measured the proton- proton total cross section at v s = 13 TeV with a luminosity- independent method. Using dedicated ss * = 90m beam optics, the Roman Pots were inserted very close to the beam. The inelastic scattering rate has been measured by the T1 and T2 telescopes during the same LHC fill. After applying the optical theorem the total proton- proton cross section is stot = (110.6 +/- 3.4) mb, well in agreement with the extrapolation from lower energies. This method also allows one to derive the luminosity- independent elastic and inelastic cross sections: sel = (31.0 +/- 1.7) mband sinel = (79.5 +/- 1.8) mb.Peer reviewe
Pressure Induced Hydration Dynamics of Membranes
Pressure-jump initiated time-resolved x-ray diffraction studies of dynamics
of the hydration of the hexagonal phase in biological membranes show that (i)
the relaxation of the unit cell spacing is non-exponential in time; (ii) the
Bragg peaks shift smoothly to their final positions without significant
broadening or loss in crystalline order. This suggests that the hydration is
not diffusion limited but occurs via a rather homogeneous swelling of the whole
lattice, described by power law kinetics with an exponent .Comment: REVTEX 3, 10 pages,3 figures(available on request),#
Characterisation of the dip-bump structure observed in proton-proton elastic scattering at root s=8 TeV
We describe an analysis comparing the p (p) over bar elastic cross section as measured by the D0 Collaboration at a center-of-mass energy of 1.96 TeV to that in pp collisions as measured by the TOTEM Collaboration at 2.76, 7, 8, and 13 TeVusing a model-independent approach. The TOTEM cross sections, extrapolated to a center-of-mass energy of root s = 1.96 TeV, are compared with the D0 measurement in the region of the diffractive minimum and the second maximum of the pp cross section. The two data sets disagree at the 3.4s level and thus provide evidence for the t-channel exchange of a colorless, C-odd gluonic compound, also known as the odderon. We combine these results with a TOTEM analysis of the same C-odd exchange based on the total cross section and the ratio of the real to imaginary parts of the forward elastic strong interaction scattering amplitude in pp scattering for which the significance is between 3.4s and 4.6s. The combined significance is larger than 5 sigma and is interpreted as the first observation of the exchange of a colorless, C-odd gluonic compound.Peer reviewe
Odderon Exchange from Elastic Scattering Differences between pp and p(p)over-bar Data at 1.96 TeV and from pp Forward Scattering Measurements
We describe an analysis comparing the p (p) over bar elastic cross section as measured by the D0 Collaboration at a center-of-mass energy of 1.96 TeV to that in pp collisions as measured by the TOTEM Collaboration at 2.76, 7, 8, and 13 TeVusing a model-independent approach. The TOTEM cross sections, extrapolated to a center-of-mass energy of root s = 1.96 TeV, are compared with the D0 measurement in the region of the diffractive minimum and the second maximum of the pp cross section. The two data sets disagree at the 3.4s level and thus provide evidence for the t-channel exchange of a colorless, C-odd gluonic compound, also known as the odderon. We combine these results with a TOTEM analysis of the same C-odd exchange based on the total cross section and the ratio of the real to imaginary parts of the forward elastic strong interaction scattering amplitude in pp scattering for which the significance is between 3.4s and 4.6s. The combined significance is larger than 5 sigma and is interpreted as the first observation of the exchange of a colorless, C-odd gluonic compound.Peer reviewe
New physics, the cosmic ray spectrum knee, and cross section measurements
We explore the possibility that a new physics interaction can provide an
explanation for the knee just above GeV in the cosmic ray spectrum. We
model the new physics modifications to the total proton-proton cross section
with an incoherent term that allows for missing energy above the scale of new
physics. We add the constraint that the new physics must also be consistent
with published cross section measurements, using cosmic ray observations,
an order of magnitude and more above the knee. We find that the rise in cross
section required at energies above the knee is radical. The increase in cross
section suggests that it may be more appropriate to treat the scattering
process in the black disc limit at such high energies. In this case there may
be no clean separation between the standard model and new physics contributions
to the total cross section. We model the missing energy in this limit and find
a good fit to the Tibet III cosmic ray flux data. We comment on testing the new
physics proposal for the cosmic ray knee at the Large Hadron Collider.Comment: 17 pages, 4 figure
Diffraction and Total Cross-Section at the Tevatron and the LHC
At the Tevatron, the total p_bar-p cross-section has been measured by CDF at 546 GeV and 1.8 TeV, and by E710/E811 at 1.8 TeV. The two results at 1.8 TeV disagree by 2.6 standard deviations, introducing big uncertainties into extrapolations to higher energies. At the LHC, the TOTEM collaboration is preparing to resolve the ambiguity by measuring the total p-p cross-section with a precision of about 1 %. Like at the Tevatron experiments, the luminosity-independent method based on the Optical Theorem will be used. The Tevatron experiments have also performed a vast range of studies about soft and hard diffractive events, partly with antiproton tagging by Roman Pots, partly with rapidity gap tagging. At the LHC, the combined CMS/TOTEM experiments will carry out their diffractive programme with an unprecedented rapidity coverage and Roman Pot spectrometers on both sides of the interaction point. The physics menu comprises detailed studies of soft diffractive differential cross-sections, diffractive structure functions, rapidity gap survival and exclusive central production by Double Pomeron Exchange.Peer reviewe
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
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
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